# FLA trouble: bad cells - why?



## jockepocke (Nov 24, 2009)

I bought 10 FLA 12 V, 105 AH crown deep cycle batteries, got 8 replaced due to bad cells (after some months of arguing). 

I have now 10 new batteries (configuration is series, a 120 V pack). I can go shorter distances without trouble (about 10 km is fine), but suddenly two batteries are out of energy, while the other have more than half the charge left! This is the same scenario as with the other batteries... 

All batteries were of course balanced and fully charged. (I use 10 smaller charger to top of the charge of each battery from time to time). They have enough water - but not too much. I also have a voltmeter for each battery so I can se the voltage drop as I drive. This is how I found the bad batteries (and because I could not get home...). At first, voltage drop is about the same for every battery, and then, quite suddenly two of them drops. 

Why do I keep getting bad batteries? What am I doing wrong? These are supposed to be new, and have only about 10 cycles! I have contacted the company who sold them, and they have no clue... Was thinking about the cold (weather is about -3°C right now), but the failing batteries are insulated and in the middle of the pack, thus not the coldest ones. The batteries are next to each other, but I think it is a coincidence. 

Max current is less than 250 battery amps, and the mean is less than 100.


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## Guest (Nov 25, 2010)

Have you checked the specific gravity of each cell when fully charged and when fully discharged from a drive? Did you top or bottom balance your batteries? Were they the same voltage from the start? You need to balance your batteries when you add in new ones to a used pack for sure and bottom balance is actually pretty good. I did. I know they are flooded but balancing from the low end is the better end. The SG is very important for floodies. Check them. Do not add water until you charge up full and don't over fill. 

Check out all the information here on Lead Acid Batteries. 

http://www.evdl.org/lib/index.html

Pete


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## jockepocke (Nov 24, 2009)

gottdi said:


> Have you checked the specific gravity of each cell when fully charged and when fully discharged from a drive? Did you top or bottom balance your batteries? Were they the same voltage from the start? You need to balance your batteries when you add in new ones to a used pack for sure and bottom balance is actually pretty good. I did. I know they are flooded but balancing from the low end is the better end. The SG is very important for floodies. Check them. Do not add water until you charge up full and don't over fill.
> 
> Check out all the information here on Lead Acid Batteries.
> 
> ...


I have not checked the specific gravity, have to rush and buy the tool first...  But I still know that I have bad cells, the problem is that I cannot figure out why! When charged, they reach the same voltage. I does not seem likely to get so many poorly manufactured cells (although I got 8 ones replaced by warranty... I am actually trying to get the company buying back their batteries, so I can later buy lithium!).

As the batteries are very new, I have not yet had to fill up on water. Also, I cannot fully discharge all batteries because of the series configuration. When the bad batteries are drained the good one(s) still have a lot (maybe half) of charge left. 

They were top balanced: Old batteries were charged full, and new were charged full by using the 10 small chargers have. 

After driving, at the end of charge, with the batteries almost fully charged, I disconnect the main pack charger and turn on the 10 small chargers, one for each battery, which brings them to the same voltage. My BMS also shows a very similar voltage for each battery when driving, until the bad ones are drained and plunge. So driving about 10 km shows nothing wrong, voltage differences appear quite suddenly.


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## Guest (Nov 25, 2010)

> So driving about 10 km shows nothing wrong, voltage differences appear quite suddenly.


Yea! at the bottom where you don't want that to happen. On top its not quite so bad because floodies can handle over charges easier than over discharges. Those batteries that are showing lots of power when it starts to crap out will suck the low ones dry and reverse them and kill them and you won't even know it. Drain your good batteries and balance at the bottom. Find a good low voltage setting and make them all the same then charge them up. Be sure you check your water and SG. New or not don't depend upon the battery company to make a perfect set for you. After a drive you want you batteries to be in the same zone. Keeps things alive. Never add water to a discharged cell. Make a list of all your cells SG both charged and discharged. It's a pain but you need to get your batteries back in line. 

Pete


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## jockepocke (Nov 24, 2009)

gottdi said:


> Yea! at the bottom where you don't want that to happen. On top its not quite so bad because floodies can handle over charges easier than over discharges. Those batteries that are showing lots of power when it starts to crap out will suck the low ones dry and reverse them and kill them and you won't even know it. Drain your good batteries and balance at the bottom. Find a good low voltage setting and make them all the same then charge them up. Be sure you check your water and SG. New or not don't depend upon the battery company to make a perfect set for you. After a drive you want you batteries to be in the same zone. Keeps things alive. Never add water to a discharged cell. Make a list of all your cells SG both charged and discharged. It's a pain but you need to get your batteries back in line.
> 
> Pete


I will try!  

I have done my best no to reverse any battery, like never driving until I cannot get further... I always stop when a battery drops... and my father will tow me home 

I cannot see why discharging all batteries to the same SOC and then charging them all to 100% would create a more balanced pack than just charging every battery to 100% individually, from different SOC (which is what I am doing right now)... Could you please explain? 

I shall try equalizing charge a couple of times too!


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## Guest (Nov 25, 2010)

You want them to start out the same on the low side. The low side is the dangerous side. If you have one cell that is low when all the others are high you can kill that cell without even noticing. Do the same drive again with maybe one more cell going south and you can kill that one cell. Each battery has 6 cells for a 12 volt battery. Any number of those can go south but when charged up full they all look fine but the bad ones hold much less AH and when discharged they crap out and the others cover for that one bad cell and that one bad cell can go into reversal long before you ever notice and you think your well within your end voltage range. Bottom balancing is a smart thing to do. Yes you should also charge and balance your batteries from time to time but you need to keep an eye on the low side too. Not just the top side. I have a battery that when fully charged shows a good SG and voltage but when discharged one cell is just crap while all the others are fine. That battery got pulled. For low discharge uses its fine but for my EV it's toast. All others are fine. 

Pete


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## jockepocke (Nov 24, 2009)

gottdi said:


> You want them to start out the same on the low side. The low side is the dangerous side. If you have one cell that is low when all the others are high you can kill that cell without even noticing. Do the same drive again with maybe one more cell going south and you can kill that one cell. Each battery has 6 cells for a 12 volt battery. Any number of those can go south but when charged up full they all look fine but the bad ones hold much less AH and when discharged they crap out and the others cover for that one bad cell and that one bad cell can go into reversal long before you ever notice and you think your well within your end voltage range. Bottom balancing is a smart thing to do. Yes you should also charge and balance your batteries from time to time but you need to keep an eye on the low side too. Not just the top side. I have a battery that when fully charged shows a good SG and voltage but when discharged one cell is just crap while all the others are fine. That battery got pulled. For low discharge uses its fine but for my EV it's toast. All others are fine.
> 
> Pete


I am with you on the theory, and thanks for reminding about the cells! To be honest, I did not think further than battery voltage (possibly because I cannot monitor cell voltage)... So probably the bad cell(s) of the bad batteries have taken some beating! 

If I understand correctly, this bottom balancing is to find any bad cells, not some way to miraculously bring back my bad batteries to life, and not a better way to balance? Or is this bottom balancing something needed to keep batteries balanced, or will top balancing be sufficient for this? 

Because, I already think I have identified the batteries containing bad cell(s), and I keep wondering why so many of my batteries keep failing! One of the other batteries, when returned, showed, according to the company something like 15% capacity, and I am having the exact same symptoms now, only I can go further!


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## Guest (Nov 25, 2010)

Bottom balancing starts your pack on equal footing. If you tap off a battery or two you need to keep an eye on those at the bottom side. If a cell goes bad and you continue to keep charging with out fixing the problem it will cascade as other cells become further out of bottom balance. When you charge it may look good if you only go by voltage. Floodies are not maintainence free.

Pete


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## jockepocke (Nov 24, 2009)

gottdi said:


> Bottom balancing starts your pack on equal footing. If you tap off a battery or two you need to keep an eye on those at the bottom side. If a cell goes bad and you continue to keep charging with out fixing the problem it will cascade as other cells become further out of bottom balance. When you charge it may look good if you only go by voltage. Floodies are not maintainence free.
> 
> Pete


Ok, thanks! Just as I though! Sorry, but what is "tap off"? Any suggestions on how to fix this? Or theories on why I get so many bad cells? 

I was thinking of adding H2SO4, which should, in theory, increase AH if there is enough PbO and Pb left on the plates. Although that would be on the cost of battery life... 

And other cells go bad... because they will have to do the work of reversing the already weak? just trying to understand!


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## dtbaker (Jan 5, 2008)

I hate to break into the tail of this thread, but thought I would throw in a few comments...

- floodies 'balance' at the top by gassing when they hit their peak. so charging until all are gassing pretty much top-balances. This is not a bad thing since this is how MOST chargers tell when you are 'done', when the pack voltage hits a target after a short gassing. You have to be a little careful if bringing mixed batterie back into balance as the gassing will deplete water more and you DON"T want to run any cells dry. If you suspect some cells/batteries were gassing more than others, be sure to water after charges to make SURE the water level is consistant.

- mixing different age batteries is problematic.... older ones charge slower and have lower capacity so the whole system gets out of balace rapidly and the weker ones get weaker.

- if all are about the same age, but out of balance badly, you MIGHT want to take the time to disconnect and wire in parallel for a coupe days and let them sit so they can self-equalize. Then charge, and then water.

- am suspicious that you are killing cells in the same position of the pack. Have you checked the cabling? connections?

- also it sounded like you are not using a normal single charger fo rthe pack in series... true? if so, are you SURE your chargers are charging to the same top voltage, and turning off correctly? perhaps one is high, or low, or gassing longer than others?


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## EVfun (Mar 14, 2010)

I have one thing to add to Dan's advice. If you do not fully charge all the batteries regularly they will quickly die. A bottom balanced lead acid pack is not a viable option.


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## GizmoEV (Nov 28, 2009)

I'd like to add another comment. I don't agree with gottdi's advice to bottom balance a flooded lead acid battery. This might be ok with Lithium but lead acid batteries will sulfate if left in a partial state of charge. Since you are monitoring all the batteries if you stop when one falls off the cliff you won't reverse a cell. As Dan said above, flooded batteries off gas when they reach full. This is why there are several stages to a flooded charging routine. My Zivan had a bulk charge phase where it would charge at full current, then a constant voltage stage where the voltage would be held constant until the current dropped back to about 6A or so and then an absorption phase where the current was kept at 6A for a set time period depending on how long it took to get the the last phase. There was also an upper voltage limit as a safety. As my batteries aged I could see that the voltage would climb and then start to drop again just before the end of the last stage of charging. As I understand it, the point where the voltage started to drop was when the batteries were full.


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## Guest (Nov 27, 2010)

I am not saying to leave your batteries in a lower state of charge but to start off balancing them on the bottom. With floodies the norm is to charge with a bit extra. If you put another battery in the pack to replace a bad one you need to balance it in on the bottom then go to the top from there. That is how it is done with lithium but lithium can be under charged so not to over charge. Floodies can handle a bit of over charge. It is good practice to start out balanced on the bottom then go up. It is also good to bottom balance the SG on the bottom too. That is where the most critical part is in a battery discharge curve. Not going to kill a floodie by over charging a but you will kill any battery if it is over discharged. Some more than others but over discharging is not the way keep your pack alive for as long as you can. Be sure you discharge your pack to a specific point then stop. Don't allow yourself to go that extra mile. It can kill a cell. If you top balance and only top balance you may never know you have a cell that discharges quicker than the others and you may find a cascade effect happening and your pack dying faster than expected. Range lessening and over all performance just in the crapper. Other cells will take over for a bad one and soon those will crap out too. 

Sorry but bottom balancing at the beginning is what you want. I am not saying to bottom balance every charge. Neither is Jack saying that on his Lithium packs. He just says to bottom balance from the start. Damn good advice. Proven and irrefutable. 

Pete


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## GizmoEV (Nov 28, 2009)

Bottom balancing floodies is a waste of time. So, go ahead and bottom balance them. First of all, you can bottom balance only in a group of 6 cells with a 12V battery. Then on your first proper flooded lead acid charge you are top balancing them so you wasted the bottom balancing and further you ran them lower than you typically want to run them.

The voltage curve for lead acid is quite different than lithium. What Jacks contention is that people were applying flooded lead acid charging to lithium. Now you are applying lithium charging to lead acid.

When bottom balancing LiFePO4 type batteries the charge cycle should never run any cell voltage over its maximum safe voltage. With lead acid it naturally just "boils" off any extra charge. Lithium do not have such a mechanism.


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## jockepocke (Nov 24, 2009)

dtbaker said:


> I hate to break into the tail of this thread, but thought I would throw in a few comments...
> 
> - floodies 'balance' at the top by gassing when they hit their peak. so charging until all are gassing pretty much top-balances. This is not a bad thing since this is how MOST chargers tell when you are 'done', when the pack voltage hits a target after a short gassing. You have to be a little careful if bringing mixed batterie back into balance as the gassing will deplete water more and you DON"T want to run any cells dry. If you suspect some cells/batteries were gassing more than others, be sure to water after charges to make SURE the water level is consistant.
> 
> ...



I have had that problem before: An equalizing charge did not stop, because some cells did not reach high enough voltage, and I lost a lot of water, so I am careful not to let that happen again! These were the old batteries, and although they did not lose enough water do make any harm, they are replaced because of other reasons. The batteries kept failing one after another, so they just replaced them all! I am afraid the same thing will happen now again... Seems like the batteries cannot deliver the power for my EV (as I said, FLA, 105 AH (at 20 h), 120 V pack - should work). 

The batteries as almost the same age, got 2 replaced first, then 8, so the two olders may have had 10-20 cycles more, or something like that. Also, these are not the batteries failing, but 2 of the 8 new ones. 

I have checked the cables, no heat etc, but I will try going further and check again, because this was one of my theories. Also cables are 70 mm^2, so resistance should be negligible. 

I do have a normal charger, china made, for 120 V FLA pack, charging at 8 A (takes some time to charge full...), but I have also 10 smaller battery chargers for balancing the pack. I will measure those today to check the voltage. I checked two of them before, showing the same voltage. Most charges, I let the 120 v charger to all the work, but sometimes I disconnect it just before charging stops, and let each battery charge full individually by means of these 10 smaller chargers, in order to balance batteries. Also, the 120 V charger have equalizer mode, used to balance the cells.


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## Guest (Nov 27, 2010)

What I said if you did not listen last time, Start with a pack bottom balanced. All on equal footing and yes you can bottom all the cells at least with SG which will be better anyway. A hassle for sure but a good thing to do. Can't hurt. Then charge as normal for floodies. I am not talking about charging as you would a lithium. I am fully aware about the charge and discharge curve of Lithiums and with the floodies you can get into very dangerous territory real fast if you decide to go that last mile. If your cells are not balanced or your batteries are not taken care of you will have problems. Your Floodies are not maintenance free. You must work with them like you would do with a VW gas engine. They are not plug in and forget type batteries. 

I also understand that your battery has cells that you can not check the charge but you do get to use SG which is equally important. More than anything get your SG to match in each cell. So rather than balance with voltage also do so with SG since that is what you can do with each cell. 

Like I said I can have two batteries side by side and charge each one to the proper voltage for a full battery but the capacity of one or more cells in the battery will be more or less than another and if you discharge to far you will loose a cell. Guaranteed and it is a proven and unarguable fact. Floodies, AGM, Gel, Lithium, NiMH, and any other you can think about to add to the list. I happen to have a battery that has cells that are down. I did not in the beginning balance them on the bottom before starting out. Now my floodies are sitting pretty. I charge the normal way for floodies and yes the top out balanced too. That does not knock out the bottom. I did mention that the floodies do top out balance during charging too. 

Bottom balancing does not mean to take your pack to the utter low end of the voltage before you balance them. You do however balance them in a low range across the board. It is done ONE TIME. Done properly it helps keep the pack balanced. If you tap off any batteries you will knock out that balance. 

I am also not talking about that drop off cliff like a Lithium battery during the discharge. The floodies don't do that but they do drop off and SAG like hell when you stress them and that hurts them too. Be careful. 

A one time bottom balance is not a waste of time. Even a $1500 pack of floodies is expensive and an investment. Take care of them. Or not. 

Pete 

Don't forget you need to check water and SG every once and awhile too and you need to keep them clean. Can't just drop them in charge them up and forget about them. It won't work.


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## Guest (Nov 27, 2010)

For 6 volt Floodies

Open Circuit Voltage	Electrolyte Specific Gravity @ 80°F	State of Charge

≥6.3 ≥1.265 100%
6.2 - 6.3	1.225	75% - 100%
6.1 - 6.2	1.190	50% - 75%
6.0 - 6.1	1.155	25% - 50%
5.85 - 6.0	1.120	0% - 25%
<5.85	<1120 0%


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## jockepocke (Nov 24, 2009)

gottdi said:


> What I said if you did not listen last time, Start with a pack bottom balanced. All on equal footing and yes you can bottom all the cells at least with SG which will be better anyway. A hassle for sure but a good thing to do. Can't hurt. Then charge as normal for floodies. I am not talking about charging as you would a lithium. I am fully aware about the charge and discharge curve of Lithiums and with the floodies you can get into very dangerous territory real fast if you decide to go that last mile. If your cells are not balanced or your batteries are not taken care of you will have problems. Your Floodies are not maintenance free. You must work with them like you would do with a VW gas engine. They are not plug in and forget type batteries.
> 
> I also understand that your battery has cells that you can not check the charge but you do get to use SG which is equally important. More than anything get your SG to match in each cell. So rather than balance with voltage also do so with SG since that is what you can do with each cell.
> 
> ...


I was of course listening, and I am buying the gravity meter today, but how can I alter the specific gravity? I have heard filling up on acid is not exactly recommended (I have about 0,5 l sulphuric acid, and if needed I think I could easily get some at my university lab - I can already fill up how much distilled water I want there), and adding water will decrease specific gravity. 

I think the problem is not balancing the cells, but rather that some of them holds less energy... what can I do about that? Or are you saying that if I equalize the troubling batteries enough the cells will get back to normal? If so, how do I do this? Equalizing charge a couple of hours? And, maybe the most important: why does some cells fall out of balance, or as I think the case is, decrease in capacity? Because I failed to bottom balance at the start?  Have to prevent this happening again and again and again... 

And I am sorry I am not actually doing this recommendations right now, but the car is at my parents place (I do not have a parking space, and even less charging opportunity at my apartment), but I will visit today!


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## Guest (Nov 27, 2010)

If you have cells in your battery that are weaker than others don't buy that battery. If your battery is charged properly your SG should be the same across all the cells. If not you can balance them out. You really need to check your batteries when you buy them. Just getting random batteries can lead to troubles. No cell will be perfect but you need to have them close. The closer the better. That is what balancing is all about at the top or bottom. Lots of things can knock out a flooded battery cell. Over discharging is at the top. Keeping your battery partly charged is another. Keep them fully charged. They are not Lithiums. Vibration, natural degradation, among others. You can buy batteries with weak cells. That is the problem. You can have a fully charged battery with weak cells and without checking SG you may have a bum battery. I can have a cell that looks fully charged but when checking SG it shows it may be lets say 90% but on the volt meter the battery looks fully charged. Much to your surprise you will if you take your pack to the utter low end while driving which many will do you will weaken that cell further and soon have a dead cell as the other cells will take over for the weak one and your performance will drop like a rock. I know first hand how that works. SG is very very important. It will show you a dead cell. So what do you do to prove it? Charge up a battery with a weak cell. It will show fully charged but your SG will be off. 

Never add pure distilled water to a discharged cell. Never use any thing but pure distilled water in your battery. Any minerals will weaken or kill a floodie. If you happen to need to ad acid go by some premixed for the task. It is likely you won't need to do that. When you go buy your batteries you need to check voltage and SG. If they won't let you, go buy them somewhere else. Don't be half hearted about your investment. 

Pete 

SG. When you discharge your pack SG goes down. When you charge up it goes up. Most likely unless you spilled your battery you won't need to add any acid. After about a year or so you many need to ad a touch. Do so only with a full charged battery and only a tiny bit at a time. Get the premixed and you add like water when your water is low but your fully charged. Not too much. A bit at a time and check. Mix well before checking. In other words go for a drive and charge up then check. Do so until it comes back into balance but don't over fill your battery either. 

If you loose water your SG goes up but low water can lead to plate damage. So watch your level and keep your water above the plates. That is the purpose of adding water. Too much water will lower your overall SG slightly. Just be careful and don't spill on your clothes. It will eat them up in a hurry. Wear old clothes while doing any work on your batteries. 

Pete


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## Guest (Nov 27, 2010)

I don't need to add more about batteries because all the information is out there. You just need to hunt and read for yourself and learn as you go. Bottom balancing Floodies is not as critical as for lithium but still a very good thing to do. No amount of care for your batteries is a waste of time.


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## dtbaker (Jan 5, 2008)

jockepocke said:


> but how can I alter the specific gravity? I have heard filling up on acid is not exactly recommended


it is really NOT recommended to change the SG... it is a good way to blow up the battery. measurement is really just a double check on whether each CELL is balanced to spot problems. I never really understood people saying to check the SG, because you shouldn't DO anything about it!

All you can do is fully charge, then water to correct levels.


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## Guest (Nov 27, 2010)

It is usually not required but sometimes it is required to bring a cell back up to the level with the others. I say check voltage and SG when you go buy your batteries. If it is grossly off don't buy the battery. SG is a Check like Checking Voltage. However if it really is required the by all means do so but do so correctly. It is not a haphazard thing to do. Be very sure you know what your doing if you need to bring the SG back to the proper levels. Usually it is not required to change the SG. 

Like I said earlier. The proper information is out there on the care of Lead batteries. Search and read. Don't do anything to your batteries until you are sure of what your doing. 

Pete


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## dtbaker (Jan 5, 2008)

gottdi said:


> It is usually not required but sometimes it is required to bring a cell back up to the level with the others.


the cases where you add battery acid (easily purchased at the auto stores mixed to sg=2.65) is really only for the rare cases that you spill a battery. I in fact had my batteries fall off the delivery truck and numerous cells spilled 'some' acid, and one corner cracked and ALL the acid leaked out! I repaired the case, refilled, and attempted to balance sg, but gotta tell you it is a tricky business in part because you don't really know how much has already been absorbed into the cell during whatever partial charge it has.

my FLA pack had a very hard life, got run dry once before I added a watering system, and probably never were well balanced from day one. They've lasted almost 2 years and 6000 miles, but dropped to about 60% original capacity and no longer comfortably work for my typical day.... so I am going to try and sell the pack to someone needing only short-range for cheap, and step up to Li.....

the BEST investment for floodies is a central watering system, and to water every 500 miles (after a full charge) because it is then quick and easy and you are sure every cell is filled the same level.


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## GizmoEV (Nov 28, 2009)

jockepocke said:


> Seems like the batteries cannot deliver the power for my EV (as I said, FLA, 105 AH (at 20 h), 120 V pack - should work).


What battery current are you pulling out of those batteries? You could be murdering them from high current in addition to over discharging them. Are they actually "golf cart" batteries? That may be your problem.


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> Are they actually "golf cart" batteries? That may be your problem.


I missed the earlier info of the capacity.... sounds like pretty weanie batteries. 100ah rating at 20hr means only about 50ah at a 1hr discharge rate. maybe 15 to 20 mile range max when new and worse rapidly if they are discharged deeply often.


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## EVfun (Mar 14, 2010)

gottdi said:


> A one time bottom balance is not a waste of time. Even a $1500 pack of floodies is expensive and an investment. Take care of them. Or not.


A one time bottom balance is a waste of time. You are going to top balance the pack every cycle or regularly. The bottom should be avoided, deeper cycles only serve to shorten life.

I do not recommend you add a battery to a lead acid pack. The batteries spend their whole life with slightly changing charge efficiency and voltage. It is difficult to get the new one to play nicely. If you must replace a battery try to get another used one that has seen similar use. 

In any case, I recommend you fully charge your pack, fully charge the replacement battery, and then add the battery to the pack. Next is a check for end of charge compatibility. Turn the charger on again, for 5 to 10 minutes, and check the voltages of each battery across the pack. If the new one is shooting way higher than the rest it will be hard to get it worked into the pack. The charger is likely to cook the new one trying to get the other batteries full.


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## jockepocke (Nov 24, 2009)

Just checked gravity: The first of the bad battery had all cells very close to 1,30 g/cm^3, however, the second bad battery had 2 cells a little closer to 1,29 g/cm^3. Note that the temperature is -10°C (14°F) here right now. Batteries are insulated, but as I have not driven for some time they are cold. I started a shorter equalizing charge to try and bring the second battery into balance. 

I am not sure if this small difference in charge can account for these batteries to die when the others have at least 50% charge left... 

Could not get a proper voltage reading, because I somehow managed to restart some chargers tampering with an AC fan. 

About 200 A should be the real top battery current. I do, however, try to drive very economical, so 200 A is very seldom. 

I am aware of the short range: car was a school project with very limited budget! This does not change the fact that I never got the pack to work properly. I am trying to get some money back and saving for 40 100 AH thundersky.


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## jockepocke (Nov 24, 2009)

About 2,5 H equalizing charge later now, and still about the same difference in gravity... 

All cells in the good batteries are at 1,30 g/cm^3, with almost no fluctuation.


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## GizmoEV (Nov 28, 2009)

200A out of those batteries is definitely going to kill them. I remember talking with some old time EVers from the Oregon Electric Vehicle Association about me pulling 250A out of 8V Trojan T-875s and seeing them cringe. There wasn't anything I could do about my hill climb home. They all agreed that I needed to go to 6V batteries. When my T-875s went south I put in a pack of 6V interstate golf cart batteries out of another Gizmo I'm restoring and my efficiency went up even though I added an extra 120+ lbs of weight to the vehicle. It weighed 993lbs with the 6V pack. Now with 40 TS LFP100AHA in a 2p20s configuration the vehicle weighs 829lbs and that is after adding a cooling blower to the motor. Definitely worth the investment. You will like the improvement when a lithium pack.

About temperature...are those chargers temperature compensated? When the batteries are cold you have to charge them to a higher voltage otherwise you are chronically undercharging them.

And I'd like the second EVfun's comment on not bottom balancing a flooded battery. This agrees with Roland Weinch on the EVDL who is a master at making flooded batteries last for years. In the 4-5 years of reading his posts on the EVDL he has never suggested bottom balancing a flooded battery even when he has talked about what was done to refurbish lead acid batteries back when they were able to be refurbished and when he talked about getting the SG in the cells balanced.


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## jockepocke (Nov 24, 2009)

GizmoEV said:


> 200A out of those batteries is definitely going to kill them. I remember talking with some old time EVers from the Oregon Electric Vehicle Association about me pulling 250A out of 8V Trojan T-875s and seeing them cringe. There wasn't anything I could do about my hill climb home. They all agreed that I needed to go to 6V batteries. When my T-875s went south I put in a pack of 6V interstate golf cart batteries out of another Gizmo I'm restoring and my efficiency went up even though I added an extra 120+ lbs of weight to the vehicle. It weighed 993lbs with the 6V pack. Now with 40 TS LFP100AHA in a 2p20s configuration the vehicle weighs 829lbs and that is after adding a cooling blower to the motor. Definitely worth the investment. You will like the improvement when a lithium pack.
> 
> About temperature...are those chargers temperature compensated? When the batteries are cold you have to charge them to a higher voltage otherwise you are chronically undercharging them.
> 
> And I'd like the second EVfun's comment on not bottom balancing a flooded battery. This agrees with Roland Weinch on the EVDL who is a master at making flooded batteries last for years. In the 4-5 years of reading his posts on the EVDL he has never suggested bottom balancing a flooded battery even when he has talked about what was done to refurbish lead acid batteries back when they were able to be refurbished and when he talked about getting the SG in the cells balanced.


Hmm.. sad, started to think something like that myself! Although the company were I bought them recommended them for this use (I was looking at some other batteries at first, but those were probably even worse) 


Damn, do not think the chargers are compensating for temperature! :/ Although they had enough voltage to gas while they were charged tonight! What can I do about this? 

I am getting quite mixed messages, are you saying bottom balancing will do me no good? I have not understood how bottom balancing should be better, or even necessary... The theory behind it all, that is


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## GizmoEV (Nov 28, 2009)

jockepocke said:


> Damn, do not think the chargers are compensating for temperature! :/ Although they had enough voltage to gas while they were charged tonight! What can I do about this?


If they were gassing then they might be putting enough out. I actually haven't watched what the gassing is like with a cold battery compared to a warm one with the finish voltage set for a warm battery. Remember that the charging will warm the batteries some so the compensation has to be based on battery temperature at the finish charge.



jockepocke said:


> I am getting quite mixed messages, are you saying bottom balancing will do me no good? I have not understood how bottom balancing should be better, or even necessary... The theory behind it all, that is


I know you are getting mixed messages. I think Jack Rickard of evtv.me was one of the first to really push bottom balancing. Basically it is nearly impossible to have a battery pack with all cells exactly matched in all aspects at all times. Temperature variations, manufacturing differences, and other things will guarantee that the cells will not all be matched. What Jack did was top balance a set of TS LFP100AHA batteries in his Gem vehicle and then drive it until the battery pack volt meter in his car dropped to the "empty" voltage for his pack. He was trying to prove that top balancing and BMS systems were bad for a battery pack. All his Gem tests (he did more than one, I believe) did was prove that if you top balance and then use just pack voltage or when the car lost power to determine empty that you are almost guaranteed to have reversed one or more cells in your pack. This is because when the first cell reaches empty and the others are not there yet they will keep pushing current through the empty cell and thus reverse its voltage. This is likely to go undetected when only measuring full pack voltage because out of say 40 batteries a 3V drop is a very small amount. My LFP pack sits at 65V at rest but will sag to 62V at about 0.5C current draw so you can see that losing one battery won't be detected easily based on pack voltage. The idea is that if you were to bottom balance all your cells to say 2.9 or 3.0V, which is where the voltage curve starts to drop rapidly, and then charge the whole pack to an average of 3.5 or 3.6vpc (this is with TS cells) that some cells will end at 3.7V and some at 3.45V and others in between but all right about when the voltage begins to rise rapidly on the full end. If you then drive until "empty" all the cells will reach empty at the same time so no one of them will be able to force current through any other cell after it goes dead.

The concern many have with this method is the fact that bottom balancing stresses the cells more than they would like. Also, if any cells drift from the rest then, without any sort of cell level monitoring, there is the risk of either over charging a cell, thus killing it or starting a fire or over discharging it and reversing it which will also kill it. Another concern is that bottom balancing will be running the lower capacity cells at the lower region of their state of charge rather than their upper region and thus wearing them out sooner.

What Jack says he has been seeing is that the cells in his car after two years of driving are actually getting closer together rather than drifting apart. Based on his experience so far he is taking the position that one should bottom balance unless a full pack of cells comes from the same batch in which case just leave them alone. In one of his more recent videos he made it very clear that he is only talking about TS and CALB cells since he hasn't tested other cells enough. He is also of the position that one should not have a BMS. There have been some BMS boards which shunt current to top balance a pack. Some of these have either poor design and/or poor or defective parts and have been stuck "on" and shunted a cell to death. It didn't turn off after bringing the battery voltage back to where it should be. Also, if a cell reaches the low voltage trip, LVT, and turns on an LED or other low voltage warning it could drain a cell too.

I think either way one is taking a risk. It is just, which risk do you want to take. The BMS boards I have on my pack don't shunt until 4.00V and don't have a LVT until 2.93V which is conservative at the low end. For example, with my pack at 2 degrees C a 2C load on them will cause the LVT to signal my dash and turn on a buzzer. This is with a full pack so one has to know how to interpret it. I also have a CycleAnalyst so I know how many Ah I've pulled from my pack. Another feature of my particular BMS boards is that below 2.75V my BMS LVT will actually turn off so it doesn't drain the cells. I don't know how many BMSs on the market do this. Mine are from www.black-sheep.us.

Now onto flooded lead acid batteries. The acid is more dense than water so if the electrolyte isn't stirred up regularly it will sink to the bottom of the battery. Charging a battery until it gasses helps stir this up and keep the electrolyte evenly mixed. I would never trust an SG reading in a battery that has been sitting still for a long time. It is almost sure to be wrong. Trying to bottom balance a flooded lead acid battery by adjusting SG at the bottom is playing with only part of the chemistry. Notice that with the lithium batteries only the charge was adjusted, not any of the chemicals in the battery. The lead plates also play a part in the reaction.
It would be worth reading some of the articles here: http://www.evdl.org/lib/index.html

Here are a couple of threads on the EVDL you might want to read:
http://evdl.org/archive/#nabble-td445728|a445736
http://evdl.org/archive/#nabble-td3026249|a3026327

In both of them Roland Weinch talks about SG and mixing acid.

HTH,
David


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## Guest (Nov 28, 2010)

> He was trying to prove that top balancing and BMS systems were bad for a battery pack.


He did prove it. He charged like you all with your BMS systems and then took the pack to its utter end which many will do. If you know people they will ignore the warnings and keep driving because it still moves. Heck if you are still moving in your ICE you still have gas right? Well not so right with batteries. He killed batteries every time. When bottom balanced he did the same and never lost a single cell. Bottom balancing is important and can be done with any battery. Bottom balancing is not taking your batteries to the utter end then balance them. It is to take them to a low safe end of charge state and balance them all. In other words take them all to that point and then charge them up. Slightly under charge them and slightly underdischarge them. In other words stop driving before you get to the drop off knee of the lithium batteries. Thankfully lead batteries don't drop off the cliff like lithiums do but the technique is the same. It is utmost important to be sure your pack is balanced and the bottom is the best point. If you take a bunch of batteries and only top balance you have no idea where your cells are when you reach the knee. If you are stupid and take your vehicle past that point you will kill a cell or two. If you bottom balance you won't. No BMS required. What do you use to manage the BMS. Why so complex for such a simple thing? No matter what you must be smart about how you drive, and charge and discharge. Keep things within the parameters of the cell and you will be fine. Take things to the utter edge and you loose. Most will not heed and take things to the utter edge and loose. 

Pete


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## GizmoEV (Nov 28, 2009)

gottdi said:


> He did prove it. He charged like you all with your BMS systems and then took the pack to its utter end which many will do.


The key is that there is that extra item. Taking the pack to the utter end. He conveniently left that out of his conclusion and refused to acknowledge it. The reality is that top balancing is only bad if you don't heed the warning signs. The statement needs to read, "If you top balance your LFP pack and only drive by pack voltage to the utter end then you will kill one or more cells." That is a completely different statement than saying top balancing kills your pack. Top balancing does NOT kill the pack. Top balancing AND running it until the car won't move does. If Jack had a BMS of some flavor which would have told him when a cell went low he wouldn't have killed any cell if he would have stopped then. That is a FACT. In and of it self, saying that top balancing a pack kills it is simply false. The whole picture needs to be told.

Why don't people get it? It is like a religion or something. Take your pick: the risk of no BMS or the risk of a BMS. If you pick the no BMS of any sort then you can minimize your risk with an LFP pack by bottom balancing them. If you pick a BMS of some sort then take either route. Both are safe if you heed the warnings and understand the risks. It is just that there have been some bad BMS designs out there and defective parts.

My BMS boards don't even shunt the way I'm using them. I charge to 3.5vpc which is a full 0.5V below the shunting voltage. I also don't run my batteries into the ground. I take monthly end of charge voltage readings on each cell set and am keeping a record of them to see what is happening with my pack. If something happens out of the ordinary and a cell either goes high or low my BMS will warn me about it. Beyond that it is like I don't have a BMS. It is quite simple. 

In any case, bottom balancing a flooded lead acid is not even in this league because it will get top balanced on the next proper charge. Yes, if you run the battery flat you will most likely reverse a cell. But to keep the bottom in line you cannot fully charge your lead acid pack. This means you are trading the risk of reversing a cell in the event that you run the pack empty with the guarantee of sulfating one or more cells because you can't fully charge them because you lose the benefit of your bottom balancing. These aren't LiFePO4 batteries! You can't treat them the same if you want the longest life. I acquired a set of undercharged 6V floodies. They had less power than my 8V pack with a reversed cell. After properly charging them which meant equalizing them regularly and charging them according to the battery temperature they woke up quite a bit but not to what they could have been had they been fully charged all the time.


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## Guest (Nov 28, 2010)

Best bet is to just go learn about flooded batteries and how to take care of them and then make your own decision on how to make them work for you. I did loads of reading and using them and also incorporating new ideas into how to make it easier. It sure can't hurt to bottom balance. If your bottom end is not in order you will run into trouble. It matters not what batteries you use. Charging is another matter all together for different batteries. 

Pete 

Make your own decision. Do your own homework.


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## GizmoEV (Nov 28, 2009)

gottdi said:


> Make your own decision. Do your own homework.


And that should always be the case. Too many people don't do this and then blame someone they listened to who steered them wrong. That is also why I posted several links to people who have been working with floodies for 40+ years and been quite successful with them.


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## Guest (Nov 28, 2010)

Why don't you get it. There is no need for a BMS if you bottom balance to be sure your low end is in order and you never over charge and have your controller cut you off before you get to the cliff. Why do you need all that dangerous wiring. He proved you don't need it. He is not against a good system to monitor AH in or out but the BMS (BS) systems out there are mostly just garbage and there is no way for anyone to know which one actually works and does what it says. 

What I see is that you buy your batteries and BS system and then under charge and under discharge and your batteries are happy little campers. It is not your BS system that is keeping them there happy as little clams on the sea floor. If you allow your BMS system to top balance at the utter top end and never have your bottom in order and you take your batteries to the utmost end which you know many will do, you will loose cells. His argument is mostly that its dangerous to have so much wiring and there is no need to top balance your pack at its utter top. What is the advantage of making sure you have that last AH stuffed into the pack. Over charging is just as bad as overdischarging. But if you have your bottom in order your less likely to loose any thing which has been proven. He left nothing out and did the tests to show you don't need a BS system. Its not that you don't need to put limits on your pack but you surely don't need a BS system that will cost you a few batteries worth. Go buy a couple extra batteries and just put in a setup that will monitor a split pack. If one side shows it's off kilter then you need to go investigate. It is not rocket science. What it is is a fact. He took his money and proved all the BMS folks wrong for the Prismatic TS, CALB, Headway and a few others. As for cylinder style batteries or packet batteries he has said he does not know. He also does not care. He is only using the Prismatic style anyway. He has done way more for EV's than many I have encountered. He has spent money to prove and test. He does not say what he does lightly as you all seem to think. Has any one actually proven that a BMS system will save your pack from abuse? If so I have not see that proof. Only words. 

Pete


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## GizmoEV (Nov 28, 2009)

gottdi said:


> Why don't you get it. There is no need for a BMS if you bottom balance to be sure your low end is in order and you never over charge and have your controller cut you off before you get to the cliff.


What Jack has proved is that in two years you don't need a BMS. I was really disappointed that he was talking about changing the batteries in the speedster because if he does, he can't say anything about the long term benefits/risks of not having a BMS system of some sort. I find it interesting that he is now saying to use a split pack voltage comparison. That tells me he is not totally for no BMS. Lee Hart published a simple device years ago to do this. You can see it here: http://www.evdl.org/pages/battbridge.html. The thing is I do get it. There are two basic paths or risks one has to take: BMS or no BMS. There are three choices on LFP battery charging with either of those choices. Jack has started talking about a third, the do nothing with your new pack of cells route and just charge them up. If one goes the BMS route then more work should go into choosing one and one should know the risks of their choices. Since Jack hasn't run his no BMS system for the life of the pack it is anyone's guess as to what will happen over time. I hope he is right. The batt-bridge is probably the simplest BMS one could get.

In the mean time, I have a BMS system which will warn me on HVT and LVT of a single cell. Furthermore, it will turn it self off below 2.75V so as not to drain the cell and kill it if I don't do anything about it. Normally neither end will be triggered. Basically I have my cake and can eat it too. I can operate as if there is no BMS and yet have the benefits of a warning if necessary. After a few years, 10 I hope, I will have my own data. I am putting my money where my mouth is too. Jack has way more disposable income than I do. For me, the no BMS route is more risky than the particular route I have gone and I can still test out the theory that the cells don't drift apart.



gottdi said:


> Has any one actually proven that a BMS system will save your pack from abuse? If so I have not see that proof. Only words.


I don't remember what topic or thread it was on but I do remember someone, JRP3 maybe, who had dimitri's miniBMS system I think, who had their pack saved because of the BMS. It cut back the controller current to limit the lowest cell from going below the LVC and he was able to limp home. Sorry I don't remember who. What we don't know, however, is how would that drive have gone if there was no BMS and the pack had been bottom balanced. That is what makes this question so difficult to be sure on. We have what appears to be two data points, one for a BMS and one for bottom balancing and no BMS.

This brings me back to the why don't I, or you, get it? You are comfortable with one real data point on a 2 year old no BMS system and I'm not. Where I believe I get it is that I'm looking for more data. Sorry, that is the Physics Major in me. I'm choosing what I feel is a lower risk route. There are so many BMS systems out there that they can't all be considered the same. I don't know any one else using the BMS system I'm using. Maybe there aren't many. After all I spent $40/cell including hardware for it, about the cost of three 100Ah batteries or 1.5 cell pairs in my pack. Was it worth the investment/risk. I think so. You don't. That is ok and that is what I'm saying. Why don't people get it? There are two types of risk. Pick one and go with it.

jockepocke, now that Pete and I have basically hijacked your thread, one of Pete's comments reminded me that you might want to look at Lee Hart's Batt-Bridge circuit. It is really simple if you have an even number of batteries in your pack. If you are concerned about over charging some batteries you might want to look at his Zener regulators too, at http://www.evdl.org/pages/hartregs.html.


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## Guest (Nov 28, 2010)

> What we don't know, however, is how would that drive have gone if there was no BMS and the pack had been bottom balanced.


Sure we know. It was done on purpose. Nothing would have happened it it had been bottom balanced. Now if you have a dumb controller and need a way to monitor and cut back when your voltage gets to a specific point I can see a monitoring system like that but you still need to bottom balance to be safe because those systems are using only voltage to do the cutback. A gross voltage monitoring of a split pack could be easy. But a monitoring system vs management system is in order. One that can do AH in and out and check a pack but no need for single battery connections. Just a few in a split pack should do just fine as the batteries if balanced (bottom) have proven to stay within specs unless your tapping off the pack and expecting things to remain balanced. 

Pete


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## GizmoEV (Nov 28, 2009)

gottdi said:


> Sure we know. It was done on purpose. Nothing would have happened it it had been bottom balanced.


I'm not sure if your statement that it was done on purpose is regarding Jack's purposeful murdering of TS cells with a top balanced pack or the drive I was referring too. I'm referring to the drive where the person was able to limp home without murdering his top balanced pack because of the BMS he had set up. And no, we don't know what would have happened. Let me expand on that. There is a possibility that he wouldn't have made it home without a tow or a charge at someone's house along the way if he had bottom balanced his pack. The reason being that he would have not charged to as high of a voltage to make sure he didn't over charge a cell. This may have been just enough energy that he wouldn't have made it. I wasn't referring to cells getting murdered or not. Since we don't know any more detail about the trip we can't say for sure. Given that there is very little energy at either end of the voltage curve it may very well be that he would have made it with a bottom balanced pack. Still, we don't know because we don't have enough information. Any conclusion to the contrary is pure speculation.

Again, two years of data on one vehicle isn't enough to convince me that no monitoring is needed at the cell level. When I convert a vehicle like a quad or my lawn mower I will probably go with a Batt-Bridge since it will be easy to check on the cells during charging and the pack will be a whole lot less expensive than the one in my car. Also note that Jack has gone from no monitoring, to an Ah counter, to an Ah counter with a Batt-Bridge type device. It seems to me that the two extremes will meet in the middle after a few years.

Edit: I agree that tapping off part of the pack is a bad idea. That is why I like the CycleAnalyst, it uses full pack voltage without having to install some voltage pre-scaler. If someone is going to use something like a PakTrakr on LFP batteries then they better be top balancing to compensate for the drain on a subset of the cells in the pack.


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## Guest (Nov 28, 2010)

> I'm looking for more data.


 How much more do you need? What will you do with that information? 

Sure you can go with or without. Kinda like the clutch or no clutch debate. I still argue for clutch and no bms but I do want a way to monitor my pack gross voltage. I will let my charger keep the voltage where it needs to be and my controller from going to far. That is my battery management system and a volt and amp guage. Pretty easy. Simple and no chance for my tiny little wires to get crossed and short out. It takes very little to short out a wire or loose a connection or make a connection erratic in nature. Just a teeny tiny little loss of communication is all it takes to toss a system into havoc. What system monitors that sort of failure? Systems to monitor systems that monitor systems. Where does it end. 

Yup! Pick your Poison. In the end it is all about what you want. Read and weigh the issues and if you do go with a BMS (BS) system be sure it is what you need and want and one that you can actually safely install without fear of shorting out. Remember it is not a static environment in the vehicle and wires are under stress and duress. So be sure, absolutely sure of your decisions. If you have one and are using it and are absolutely sure you have done right then I guess you have done well. I do bet you find out that you don't need one in the end when you finally decide you have enough data points to satisfy your desires. When will you stop? I know of one person who has monitored his batteries from day one. Every cell and battery and every charge and discharge and every fill up and battery change since the 80's. He has proven you don't need to monitor your pack so close but continues to this day. That is a lot of years of data points and still he is not satisfied with his work. 

Do you monitor your gas usage? You sure your getting the mileage you expected? You sure your tires are full and proper every day? You sure your brakes will stop you? You sure your starter battery is charged enough? Or do you take for granted that it just all works as expected. No magic and no monitoring and yet year after year it just works. When it fails you replace it. What is the difference with the batteries. You don't monitor you engine that close either. You just know it works but are you sure it will work tomorrow or when you get off work? No you don't but yet you know it will most of the time. Very little checking is ever done on your car. Same should be with your EV. 

How many with BMS systems monitor their systems even though you have the BMS installed. The premiss behind the BMS is to have a system that you can set and forget. I doubt many with them have done that. 

And again to what end is all that information going to do for you anyway? It will prove you don't need one installed and it will prove you don't need to monitor your system daily either. It has been done for you. Believe the facts. 

Pete


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## Guest (Nov 28, 2010)

I was referring to he would not have murdered his cells if they had been bottom balanced and no bms. Nothing to do with getting to the destination. When your out of juice your out. But is your pack dead? Most likely not. Had it been top balanced and taken that far with no BMS I can guarantee that he would have had some bad cells. It's been proven. Top balanced only. Argue the point till your blue in the face. The facts remain. 

By the way, Jack has always been an advocate of AH counting and and a bridge to monitor a split pack only not each cell in the pack. He did not go from none to that. He has always wanted a good battery monitoring system which is still needed by the way. It is always a good thing to be able to monitor. His controller monitors the end voltage for cutout and his charger monitors the top and charges to a set point. That is his system. He monitors split pack voltages but not every 1/100th of a second. It is just a glance at a couple meters or however he has that setup. He is working on a setup that monitors AH in and out to better show a proper SOC while on the road. You know, a fuel guage. One that is more accurate than just voltage alone. 

Pete 

I'm tired, time for bed. 
Time to install my adaptor to my motor tomorrow.


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## EVfun (Mar 14, 2010)

Why not just run the amp hour counter? Know the capacity of your lowest cell and make sure it is charged. The rest can be top balanced, bottom balanced, or as received. Shut the controller down when the amp hours are removed -- you ran it out of "gas."


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## Guest (Nov 28, 2010)

Do you have access to a good AH counter that can shut down a controller after a predetermined AH rating has been meet? When I mean good I mean good quality and one that is accurate and available now and not months away. 

Pete


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## EVfun (Mar 14, 2010)

The old E-meters where good at it and are not to hard to find. Switch them from showing watts to amp hours and set Peuket's to 1.0 for Lithium, then use the low level lift lockout to shut it down. 

Right now I have an EVworks fuel gauge driver that is an amp hour counter designed to drive a standard thermal/resistive fuel gauge. I won't know if it is accurate enough until after it's been installed in the car for a while. It's output could be used to drive a simple comparator circuit to set the cut off point. If it has the repeatability that would be a simple prefboard project with just a handful of parts driving a small PC board relay (set up so that relay going off is the shut down signal.) It is pretty common that I build up a few little boards to do different things in all the EVs I've done, it's part of integration. 

The next version of this gauge driver is available for order now, but yet in stock. EVworks has been real good about delivering stuff. It has the adjustable low level output built in that doesn't have to be used to drive a low fuel light.

Currently my backup is the EVworks cell level monitors. These mean I have no traction pack potential spaghetti as the units bolt directly to the cell terminals. The small connection are a single series loop that connects to each units normally closed photorelay. The isolated outputs remain closed between 2.5 and 4 volts. One end of them is connected to the vehicles 12 volts through a 1000 ohm resistor. The other end goes to a comparator circuit that keeps a relay closed so long as the cell loop remains closed (the head board is from Dimitri's system.) This signals an annoying underdash buzzer and severe Zilla cut back at this time, but I could turn the Zilla down to nothing or even use a relay to cut the 12 volt ignition input. I'm still in the new build testing phase so I'm pretty much the BMS, even ahead of the installed BMS. I'm working this stuff out so I can turn it over to the system, and also because cell level boards are not quite as good an idea for the summer beach buggy EV.


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## jockepocke (Nov 24, 2009)

Ok, so I got a lot of info here! 

In fact, I monitor the voltage over each battery while driving using these http://www.evconvert.com/article/led-bargraph-battery-monitor-part-2 LED bargraph monitors (10 of them), so no need for a the batt bridge thing! Checking the voltage as I drive will tell me if a battery goes south, which is exactly what happened, and it happened way before the others. High end voltage is 12,7 and the low-end voltage of the LED bargraph monitor is at 11,0 volts, so in theory, I should be warned way before I can reverse a cell (voltage should drop below 11 volts if one is reversed, and I try to always keep the resting voltage, as well as voltage during sag, above 11 volt/battery). 

The problem right now is not how to tell wether my batteries are bad, or out of balance, as I know they are, and also which ones are. The voltage of the good cells were about 12 volt resting when two of the batteries got below 11, and so of course I did not try to drive any further. Also, SG reading shows issues with the balance in cells in one of the bad batteries. 

So basically, I need one or two batteries replaced as they hold maybe 50 % of the energy, and probably need a better pack to not kill the batteries one after another, which seems to be the case right now (although I still see cars with smaller packs doing fine like this one, about 100 kg lighter than mine: http://www.diyelectriccar.com/garage/cars/194 or maybe SLA can handle more amps?). What I am trying to do is getting some money out of the FLA pack and go lithium when I can afford. No point in buying more Pb when I am still switching to Li. 


I will probably NOT bottom balance the FLA pack, due to the issues of under-charging lead acid. Lets say I bottom balance my pack right now, by bringing all batteries down to 0 % charge for the ease of calculations. I then charge the whole pack until the first battery is filled. Because of the bad cells some batteries can only hold, lets say 50 AH when fully charged. That means the good cells, if we say they can hold 100 AH, will only be half-full! Issues with this is that the charger will probably continue charging until pack reaches high enough voltage, thus over-charging the bad cells, OR leaving most of the batteries at 50 % SOC, not a good idea for FLA? Li is not the same. 

It is true that with a bottom balanced pack I will be noticed by pack voltage when I cannot go further, which will happen when all batteries are 0 % SOC, that is when 50 AH have been used, instead of having 2 batteries of 0 % SOC, and 8 at 50 % SOC, when 50 AH have been used. The issue with the second setup is of course that if you try and drive further you will reverse the other batteries. However, monitoring them should make bottom balance unnecessary.

(And I know I should not drive to 0 % SOC, but it is the example that is important here!)


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## Guest (Nov 28, 2010)

I really like that fuel gauge driver from EVworks. I plan on purchasing one. Elegant. Perfect for my VW Bus. No need to add in a gauge or change the original. The bus does use an electric fuel gauge. Looking at some lithium batteries right now. Should have them before the end of December. So you are more or less monitoring your own rather than managing them via electronics. Monitoring is what is needed and a redundant system should be in play. My controller works well at cutting back at a specified voltage but adding in the ability to cut back from AH used would be even better. A back up so to speak. Splitting a pack and monitoring and recording the voltage between packs to be sure they are balanced is good too.

Anyway when an excellent well executed battery monitoring system is available that will monitor voltage, ah in and out and be able to shut down the whole system in case of fault wirelessly then I will become interested. I will monitor my own pack with minimal electronics. My controller is good at much of that already. 

Pete


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## EVfun (Mar 14, 2010)

jockepocke said:


> In fact, I monitor the voltage over each battery while driving using these http://www.evconvert.com/article/led-bargraph-battery-monitor-part-2 LED bargraph monitors (10 of them), so no need for a the batt bridge thing!.
> 
> So basically, I need one or two batteries replaced as they hold maybe 50 % of the energy, and probably need a better pack to not kill the batteries one after another, which seems to be the case right now (although I still see cars with smaller packs doing fine like this one, about 100 kg lighter than mine: http://www.diyelectriccar.com/garage/cars/194 or maybe SLA can handle more amps?).
> 
> It is true that with a bottom balanced pack I will be noticed by pack voltage when I cannot go further, which will happen when all batteries are 0 % SOC, that is when 50 AH have been used, instead of having 2 batteries of 0 % SOC, and 8 at 50 % SOC, when 50 AH have been used. The issue with the second setup is of course that if you try and drive further you will reverse the other batteries. However, monitoring them should make bottom balance unnecessary.


Please fuse those wires going to your voltage monitor boards at the battery terminals. This is one of the things EVers commonly do that presents a real shorting hazard. You are bringing full pack potential around the car to get inside. Little 1/4 amp fuses will do fine. With lead systems there is only about 1/4 as much of this spaghetti for a monitoring system so generally we where getting away with it (I even have that spaghetti, unused and unfused, in my EV buggy.) 

Most SLA batteries can handle more amps peak. I think the other part of the problem is that you are trying to replace bad batteries instead of the whole pack. Lead acid batteries have changes going on throughout their life, the charge efficiency slowly drops and the end of charge voltage tends to as well. It has always been difficult to mix new and old. It looks like you are using what is basically a marine type battery, and they don't have as long a life in deep cycle duty.

I guess the goal is to limp these along until you can build a new pack. Limping lead usually means bad range and a little more attention when charging. This is one of those times when a set of Manzanita Micro battery regs with big load resistors would make things a lot easier. The problem is, they have had a lot of feature creep, and price creep, over the years. It used to be a $30 per battery solution that could make just about any 2 batteries work together. You might want to see if you can get some used batteries of your size. They could be better than your worst ones and cheeper. They are also likely to charge in the pack with less problems that new batteries in a old pack.


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## jockepocke (Nov 24, 2009)

EVfun said:


> Please fuse those wires going to your voltage monitor boards at the battery terminals. This is one of the things EVers commonly do that presents a real shorting hazard. You are bringing full pack potential around the car to get inside. Little 1/4 amp fuses will do fine. With lead systems there is only about 1/4 as much of this spaghetti for a monitoring system so generally we where getting away with it (I even have that spaghetti, unused and unfused, in my EV buggy.)
> 
> Most SLA batteries can handle more amps peak. I think the other part of the problem is that you are trying to replace bad batteries instead of the whole pack. Lead acid batteries have changes going on throughout their life, the charge efficiency slowly drops and the end of charge voltage tends to as well. It has always been difficult to mix new and old. It looks like you are using what is basically a marine type battery, and they don't have as long a life in deep cycle duty.
> 
> I guess the goal is to limp these along until you can build a new pack. Limping lead usually means bad range and a little more attention when charging. This is one of those times when a set of Manzanita Micro battery regs with big load resistors would make things a lot easier. The problem is, they have had a lot of feature creep, and price creep, over the years. It used to be a $30 per battery solution that could make just about any 2 batteries work together. You might want to see if you can get some used batteries of your size. They could be better than your worst ones and cheeper. They are also likely to charge in the pack with less problems that new batteries in a old pack.



They are all fused, of course!  Although they have 24 V car-fuses, which is still better than nothing! 

Well, I got the first pack of 10 FLA totally replaced, these are 10 new ones! But two of the new ones I have were used in the old pack a couple of cycles, probably less than 20. What happened was that battery after battery kept failing, and ultimately I got tired and got the 8 ones left from the old batch replaced as well. 

Marine type you say? Strange, because they actually recommended these batteries for use in an electric car conversion! They are crown deep cycle, and about 23 kg each. Maybe I should have been less trusting when they offered me a better price on these than listed... :/ 

No, goal is to get a good deal on them buying back their cr*p batteries, and me buying LiFePO4


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## Guest (Nov 28, 2010)

> Marine type you say?


Quite likely. The sales people at battery companies have no friggin clue and only want to sell you some batteries. If they can convince you then they have done their job and made some money. We try to inform folks around here to be sure you are using Golf Cart batteries. No marine or starter batteries. Marine batteries are designed for long slow trolling. Yes they are deep discharge batteries but not suitable for EV use. Use 1/4 amp fusing on all those wires from your monitor. Any higher and you risk fire and shock hazards that can kill. If you have a short you want that short to blow the fuse like yesterday. Be Safe. Be Smart.


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## jockepocke (Nov 24, 2009)

gottdi said:


> Quite likely. The sales people at battery companies have no friggin clue and only want to sell you some batteries. If they can convince you then they have done their job and made some money. We try to inform folks around here to be sure you are using Golf Cart batteries. No marine or starter batteries. Marine batteries are designed for long slow trolling. Yes they are deep discharge batteries but not suitable for EV use. Use 1/4 amp fusing on all those wires from your monitor. Any higher and you risk fire and shock hazards that can kill. If you have a short you want that short to blow the fuse like yesterday. Be Safe. Be Smart.


Damn [insert obscenities] I just checked, and now, more than a year later, those are actually referred to as marine batteries! Still, I just checked the email conversation I have with them, and they are actually telling me to buy them, because they will suit my application better! 

I will have to blame myself a bit for not researching this enough! Well, no idea trying to drive anymore with those... will probably just kill them all!


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## GizmoEV (Nov 28, 2009)

gottdi said:


> How much more do you need? What will you do with that information?
> [snip]
> And again to what end is all that information going to do for you anyway? It will prove you don't need one installed and it will prove you don't need to monitor your system daily either. It has been done for you. Believe the facts.


Right now the fact is there is one data point worth only two years of length. There is no one that I have heard of that has run for the full life of a LFP pack. I need the data from the full life of a pack for it to really be valid. If I only wanted my pack to last a couple years or maybe three I wouldn't bother with any sort of BMS.

What I do have is individual BMS boards, screwed to the top of brass bolts which hold the connecting straps. They are all conformal coated to handle the elements. There is a daisy chain of three wires running from one board to the next and ending on a master board which then has three wires to my dash. The wires carry only 12V so no high voltage in the dash from this setup.

What I do have is a system that lets me test both ideas, BMS and no BMS, simultaneously. Here is how I figure it. Since I'm not charging up to the shunt voltage of 4.00vpc I'm not shunting so not continually top balancing my pack, same as no BMS. If I go the life of the pack and never have a cell go over voltage on charge then we have another data point to support no cell level monitoring. If I never hit a LVT while driving normally and am still above the Ah usage limit then a we have another data point to support no BMS needed at the bottom end. If, however, I have a cell go bad and am warned by the BMS system then we have a data point in favor of a BMS system. Time will tell. My getting data once/month on end of charge voltage will also help determine if there is a trend as the batteries age.


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## GizmoEV (Nov 28, 2009)

gottdi said:


> Had it been top balanced and taken that far with no BMS I can guarantee that he would have had some bad cells. It's been proven. Top balanced only. Argue the point till your blue in the face. The facts remain.
> [snip]
> Time to install my adaptor to my motor tomorrow.


If you read through everything I have written you will see that I have never argued that point. In fact, it had been proven many times before Jack did it that if you top balance and then drive until the pack voltage drops that a cell will get reversed. Jack didn't even need to run the test him self to prove that. That point is even proven in theory. What is being done is trying to prove that if you top balance and run the pack until the voltage drops that it is the fault of the BMS. That statement is simply illogical. Sure, bottom balancing and doing the same thing supports bottom balancing but it does not follow that a BMS is bad. It is not an either/or situation. What has not been proven is whether all the cells in a pack will always behave the same throughout the life of the pack. That is the data that isn't out there. And unless I missed it, Jack didn't start talking about some sort of Batt-Bridge monitor until recently, well after he did his cell murdering in his Gem.

Edit: hope your adapter installation goes well today. I assume this is in your VW Bus?


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## Guest (Nov 28, 2010)

Well I got set back a bit doing some other stuff with my Daughters Jetta but yes the Kostov will be going in the Bus.


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## jockepocke (Nov 24, 2009)

gottdi said:


> Well I got set back a bit doing some other stuff with my Daughters Jetta but yes the Kostov will be going in the Bus.


Everything went well with adaptor? 

I just talked to the company, and they agreed on buying back batteries for 70% of what I payed! Not the full price, but at least something!  

So now I have 7000$ for Lithium!  Maybe for the summer then!


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## EVfun (Mar 14, 2010)

I don't know what kind of performance you expect, but I think you would be faster and go a lot farther with a pack of 40, 100 amp hour Thunder Sky or CALB (Sky Energy) cells. That should fit your budget too, depending on local costs.


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## GizmoEV (Nov 28, 2009)

Awesome! As you look at Ah counters consider the CycleAnalyst. It takes a little work building a faceplate for it (the large screen version) but it gets its energy from the whole pack so it won't drain a few cells and get them out of balance. They are at http://ebikes.ca/index.shtml. I just checked and they now have an enclosure for the large display version now. That would have made my life easier!

If you haven't already I'd start figuring out how you are going to mount them and whether or not you will have some sort of heating. I've read multiple places that you shouldn't charge them when they are below 0 degrees C but I haven't found any one with a definitive reason or what happens if you do. You'll also want to be sure you have a charger which is very good at stopping at your "full" voltage. I have a Zivan and got it programmed with a 3.65vpc cut-off voltage for 19 cells but am running 20 cells with the voltage calibration pot turned up just a tad so my cut-off voltage is 3.48vpc. This is for TS cells. Watching the Zivan charge it has been very consistent, within 0.2V of the cut-off voltage at battery temperatures from just above 0C through 25C. It charges full tilt until about the last 10 minutes when it starts tapering off all the way down to 0A. I've seen it run at less than 20W out of the wall for the final stage of charging. I'm sure there are many other good chargers out there to consider especially if you need both 120V and 208 or 240V charging.

Be careful getting lithium, however. Once you have used them for a while you'll likely never build a lead acid based conversion again.


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