# Floodie / Lithium hybrid battery experiment



## piotrsko (Dec 9, 2007)

as much as i would like to see this; I'm thinking it might be a disaster for the calbs's because the chemistry's of the different batteries just don't match up. perhaps a series string of fla then calb pack then fla and parallel those strings.


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## onegreenev (May 18, 2012)

As long as you don't over or under charge the lithium cells you will be fine. I had a disaster with my Prius booster pack to my lead acids. Prius cells over charged. I did not have a smart charger which would be important in the case of using different batteries. Lithium charge is nearly the same as lead acid except the balancing cycle and float cycle. 

You going to use a lithium charger or lead acid charger?


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## Ziggythewiz (May 16, 2010)

poitrsko: not sure what you mean by flood calb flood. I'll post a circuit diagram later to better explain my plan

pete: I'll be using the lead charger I currently have. They'll charge in parallel to mostly offset the unbalancing caused by discharging in parallel, and the JLD will cut them out before they get too high. 

I probably want them to charge to about 3.5V/cell (14V on the lead they're boosting) so they'll rest around 3.3. Since they have to match the lead they'll probably live at a high 3.2-3.3 all the time. 

I want to do a DIY lithium charger someday, but likely not until just before switching to full lithium.


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## Ziggythewiz (May 16, 2010)

Here's a schematic of the planned setup


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## mizlplix (May 1, 2011)

Parallel anything gets interesting. Paralleling different power sources is even more. But, after charging them separately , when that isolating contractor cuts back in, the fun really starts.

One will be charging the other, always, until equilibrium is met. 

Series is easier. Just monitor the smallest capacity cell and charge/discharge to that.

Miz


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## Ziggythewiz (May 16, 2010)

Yes, the plan is to have the contactor cut out when the cells are at a voltage that will let them rest equal to the lead's resting voltage. I'm sure it will take some tweaking. 

One of the points of this is to see how things behave in parallel. As for upgrades, series is not even an option without either two new chargers or a new charger and motor controller.

I've had some repairs that set me back some, so I still need better baseline records, and I decided I need some more meters before I'm ready to go.


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## onegreenev (May 18, 2012)

mizlplix said:


> Parallel anything gets interesting. Paralleling different power sources is even more. But, after charging them separately , when that isolating contractor cuts back in, the fun really starts.
> 
> One will be charging the other, always, until equilibrium is met.
> 
> ...


You can parallel Lead Acid and you can Parallel Lithium but I would not mix chemistries in series or parallel.


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## dougingraham (Jul 26, 2011)

onegreenev said:


> You can parallel Lead Acid and you can Parallel Lithium but I would not mix chemistries in series or parallel.


Parallel works fine but you have to know what you are doing.

I wouldn't consider this as a solution for anything because you still have lead acid batteries in your car and you still have all of their disadvantages, namely the low energy density and high weight. The only thing people see with LA is the illusion of saving money.


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## onegreenev (May 18, 2012)

dougingraham said:


> Parallel works fine but you have to know what you are doing.
> 
> I wouldn't consider this as a solution for anything because you still have lead acid batteries in your car and you still have all of their disadvantages, namely the low energy density and high weight. The only thing people see with LA is the illusion of saving money.


Lead along side NiMH is not a good idea. Yes it can be done but introduces a high level of complex issues. 

I agree that people see the illusion of saving money. It is that illusion that stops EV's from becoming main stream. I am for breaking the illusion. I will break 13,000 miles today on my Leaf. I'd say it has fully integrated itself into society just fine. Most everyone has more than one vehicle and most driving is done commuting to and from work. Like me I commute and work 5 days a week and two days off. I do go places that negate my use of the Leaf but not often. It is then that we take the gasser. We have spent so much less in fuel it is amazing. I have now gotten our TDI back on the road so the Wife will be driving that for awhile. 46 mpg is pretty good and I may try bio fuel at home now that one tank will last at least a couple months for my wife's commute. 

Electric is it and Lithium is king. Cost IS less.


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## TruEnergy (Apr 6, 2009)

As long as your contactor cuts out at the right voltage, I believe your charge method will work fine. My guess is the lithium will consume the majority of the charge current due to its lower IR.



Ziggythewiz said:


> ..., and I decided I need some more meters before I'm ready to go.


Not sure what you have in mind for meters, but I have one of these Doc Wattson Meters, and its pretty neat for the price. It doesn't log, so you have to manually record data at regular intervals. But for tests like this, you'll probably be monitoring it anyway.

http://www.powerwerx.com/digital-meters/doc-wattson-meter-dc-inline.html

I ended up finding one on eBay a while back, for slightly cheaper. If you google it, there seems to be more online stores carrying them now.


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## Ziggythewiz (May 16, 2010)

I have a JLD404 for measuring amps through the CALBs, and I'll compare that to the crappy westach reading the full pack. I'll also have a bunch of cheap DVMs on individual batteries/groups.


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## TruEnergy (Apr 6, 2009)

Nice.

Glad you are able to do this experiment. Thanks, and looking forward to the results.


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## Ziggythewiz (May 16, 2010)

System's been good to go for about a week. Just need the rain to stop or find the time to get my wipers fixed so I can start getting data. Some areas got 17" yesterday.


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## Ziggythewiz (May 16, 2010)

So...I've finally managed to squeeze a few commutes in between the thunderstorms.

Before starting the experiment, the floodies (HM29) measured at ~12 mΩ. The CALBs measure at 6 mΩ. So far, current sharing seems to be close to expected based on those numbers, with the CALBs passing 65%

With the batteries typically within 1/5th of a volt when connecting or coming off a cruise, current between strings starts around 10A, and decreases to ~5A within a few seconds, then tapering down to 2 within a minute or two. I never gave it a chance to fully equalize, will have to see how long that takes.

With my current charge level the CALBs were almost always feeding the floodies, though it was running backwards at least once. I need to tweak the charge level to try to minimize that. 

Voltage sag for the boosted batteries was dramatically improved.

I really need another JLD or two to get better data, and will look into accessing the data port for some automated logging as well.


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## PStechPaul (May 1, 2012)

I like experiments like this. The idea may go against conventional wisdom, but you have made some thoughtful approximations and it seems like it may work for you. 

My idea was to have complete battery modules containing any number of cells of the same chemistry, and including all the BMS and charging and protection circuitry in the module, and also boosting (or bucking) the voltage so that the output is a consistent value, such as 144V. Each module would be individually rated for a certain kW-Hr and could have built-in displays showing the approximate state of charge and cycle data and expected end-of-life. But such a device would need a very efficient DC-DC converter or buck-boost circuit. It might be useful for small vehicles where you might be able to use one 2 kW-Hr pack with 320 VDC output for a 2 HP riding mower or small tractor with a 3-phase motor.

Keep up the good work. Your monitor panel is impressive!


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## Ziggythewiz (May 16, 2010)

Thanks, I'll have to rework my monitor panel when I get another JLD. Will need some better tools so I'm not having to 'cut' the plastic with my grinder again.


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## PStechPaul (May 1, 2012)

Have you considered using a PIC or other microcontroller with multiple A/D channels to do the monitoring? It could interface to an LCD display and/or it could connect to a Windows program vis serial port or USB to display the data and log everything to a data file for later analysis. Here is what I have done:
http://www.mytractorforum.com/showthread.php?t=239700

It uses quad op-amps as differential amplifiers so it can read voltages and currents without worrying about the ground reference. I don't have the circuit in good form but I'm willing to share details and source code. The PIC code is written in C and the Windows GUI uses Borland Delphi, but you can also use Hyperterm or any other serial port terminal application. However, for a nice display, you will want something a bit better.

I wasn't sure what the JLD was but I found this:
http://evtvshop.projectooc.com/proddetail.php?prod=JLD404AH

That is a nice meter but for $175 it's a bit much. If you don't mind a few hours of breadboarding you can build something like I made for less than $50 or so.


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## Ziggythewiz (May 16, 2010)

Thanks. I do need to look into that or a celllogish method to store the data. My meters are great for watching, but it's a a bit of work to take samples from a video.

The JLD404's awesome, after having it for months I don't know how I ever drove without it. Mine's a bit gimpy, so I need to send it in for replacement, but I may get another one as well, haven't decided. It's only $70 from the vendor, $100 if you count the shunt and a DC-DC if you want that. It can do logging as well, but I haven't messed with that yet.


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## Tedktis (Jan 20, 2012)

Awesome! Love the expirement, regardless of the outcome. Think out of the box and take risks, that's what got us here in the first place isn't it?


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## Ziggythewiz (May 16, 2010)

Good to hear the interest. I probably won't bother geting more data for now on the HM29's as I'd rather drive 'em into the ground. Should have phase 2 up (GC8's) in a couple weeks after being out of town.


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## Ziggythewiz (May 16, 2010)

Destroyed and replaced 5 batteries as planned. Phase 2 is now good to go and I should have data tomorrow (GC8 behavior, boosted and non). Phase 3 is on the way


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## TruEnergy (Apr 6, 2009)

I wish I had the testing equipment (and an EV!) to do some real world testing like this!!! Good work Ziggythewiz!

For what its worth, I did a simple discharge simulation.

12V Pb 18mΩ
12V LiFePO4 6mΩ
R1 10Ω
R2 1Ω
R3 0.01Ω
Switch 1 'on' at 1s (0.91Ω parallel)
Switch 2 'on' at 3s (0.0099Ω parallel)

At low loads, the two chemistries share current contribution. At higher loads, the LiFePO4 contributes more - limited by its lower IR. I don't have detailed cell models, but this should explain why the Pb voltage sag was less. Being able to log individual pack discharge current and total current should show a similar trend. The question is the rate of power consumption. At relatively "low" loads, they will contribute a similar amount. Under "high" loads the lithium should contribute more. Low and high are very relative because if you never actually reach the "high" part - both chemistries will continue to contribute evenly.


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## Ziggythewiz (May 16, 2010)

Interesting sim. I don't suppose there's a mechanism to make the voltages sources behave like batteries (voltage decreases with runtime/SOC)?



TruEnergy said:


> I don't have detailed cell models, but this should explain why the Pb voltage sag was less.


By less sag I mean the boosted lead sags far less than non-boosted because it carries less than half as much current. That was an assumption going in and one of the goals of phase 3 is to see how cycle life is affected (for the 29HMs as I have no control data for GC8s) by lowering the amp demands on the lead pack.



I'm still analyzing the data from phase 2. Just finished a page of calcs and realized I biffed some formulas, so now I'm questioning the rest of it 

I have found that the amp sharing is very SOC dependent. With a higher SOC (where I want to run) the lithium will carry 75% and at a lower SOC they can share even 50/50 (what I'd like ). I need to squeeze my grey matter and see if there's a cell count that will feed me cake, at least for my typical commute.

I'm really slow crunching numbers as I'm trying to get the garage in order for new cells arriving this week  Then phase 3 begins! I expect the full hybrid pack to add ~13-17 miles to my range (currently 18-34 miles).


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## TruEnergy (Apr 6, 2009)

Indeed a more detailed battery model would help simulate your findings much more accurately. I have read some university papers where they attempted to create PSpice models of lead batteries. Very difficult and very specific to the brand, internal construction, capacity, and materials used.

It might be possible to create one from something like a PL6 log. If the logs are generated at different discharge rates.

Do you know your total amperage draw? If so, I could program identical pack sizes that you are using and iterate through some load values to get an idea of the current distribution. But since the distribution seems to vary with SOC, you will be faced with finding a "close enough" sharing solution. Let me know if there is anything specific you'd like me to try simulate. I will also continue searching for some battery models.


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## _GonZo_ (Mar 23, 2009)

Some years ago I run a very similar experiment making it even more complicated.
Firstly I wanted to test an hibrid life 4S pack made with A123 cells and TCL cells in paralell that did not had any problem to work and passed all the test but there is no much benefit to do this this in order to gain power unless ther is a control.

That battery was left on my garage and endend in parallel with the 12V lead battery of my IC car.
Happened that I was going on holidays and the Lead battery decided to do weak start the same morning I was leaving so I just screwd the Life battery in a run and for holidays we left... 
It finally was instaled under the hood without BMS (I checked it every month or so) for a year, until I bought a new lead battery (you know there is always more interesting things to do...)

No problems so far with the sistem, actually the Life battery was taking care of most of the job due the weakness of the other battery, and it is quite small around 12-14Ah.
I still have it around and seems to be find, anyway a test will be necesary to prove that it is still ok.


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## _GonZo_ (Mar 23, 2009)

Ziggythewiz said:


> Not familiar with TCLs. Is that just a brand?


It is an big electronics OM manufacturer in China they produce lithium cells as well.
http://www.tcl.com/


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## Ziggythewiz (May 16, 2010)

New cells arrived. I pulled the booster packs from the car and everything's just about fully charged. I need to finish drilling and grinding my busbars so I can do a 4S10P final charge then 42P to sit and balance.

I ran some numbers and found my typical commute voltage drop is ~140 -> 134.5V 
I want to run the booster pack between 90 and 30% SOC, which corresponds to 3.33 -> 3.2 VPC. With 42 cells that's 139.86 -> 134.4


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## Ziggythewiz (May 16, 2010)

Booster pack fully charged and balancing.


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## joamanya89 (Feb 13, 2012)

you are missing something here... if you really wanna think green, let's think about batteries recycling, and for lithium it is not possile yet, so LA batteries are really green when you know that almost 97% of it can be recycling


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## joamanya89 (Feb 13, 2012)

but what are the recycling cost? the silicon is also recyclable but using acids and very dangerous products for environment...

You can't think that you are saving the planet if you are killing it in other place


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## joamanya89 (Feb 13, 2012)

sorry if I have bothered you, I just really care about environment, and I keep thinking it is a delicate topic about using any kind of battery.

I wouldn't disturb you any more...


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## jeremyjs (Sep 22, 2010)

joamanya89 said:


> sorry if I have bothered you, I just really care about environment, and I keep thinking it is a delicate topic about using any kind of battery.
> 
> I wouldn't disturb you any more...


If nothing else there's very little lithium in one of these batteries, they're not all that toxic, and contain largely copper and aluminum by weight in the foils and terminals. I bet that you could find a local scrap yard that would take them for the aluminum and copper content alone. 

Anyway. Back on topic. Love reading about these types of real world experiments. Keep up the good work.


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## Ziggythewiz (May 16, 2010)

Got the booster pack loaded up last weekend and finally got the instrumentation connected enough to make the FLHB operational today. Taking it easy until I get a few more meters connected to keep an eye on things.

One benefit I hadn't really considered before is the reduced peukert from taking the load off the floodies. They averaged ~25A this morning, so I should be able to get a much higher % of sticker out of 'em compared to drawing at 80A. Will have to do a range test in a few weeks to see how much it helps.


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## Ziggythewiz (May 16, 2010)

Charged higher than I meant to so cells were resting at 3.38 instead of 3.3 where I want 'em. 

High SOC = slutty batteries...they put out like crazy.

I have my other JLD in now so I can see what's going on, the booster carried 85% of the load, with the floodies just along for the ride and getting charged whenever I let off the pedal. I drove chunks on the booster only to try and knock 'em down but it didn't do much. After a 6 mile drive the boosters were still too high to bother charging.

Also noticed when using only the lithium the current ramps up almost instanty instead of taking a few seconds. Not sure why that is; will have to investigate in a week or two.


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## Jamie EV (Oct 3, 2012)

Interesting results. Sounds like the Lithium may be "backed" my the lead acid? Perhaps they are acting as a buffer against catastrophic drain ?

All conjecture on my part but I'm waiting for your reports with baited breath!


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## Ziggythewiz (May 16, 2010)

The lithium booster pack has enough juice for my regular commute (just), so I expect the lead to just share the current load to keep the C rate down on both, but for days I have to run between offices or do errands I expect the booster to do most of the peak work while being fed by the floodies while under peak.

I think the booster's JLD may be misconfigured, exaggerating the extreme results reported above, so I'll have to fix that and see how things look tomorrow.


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## Ziggythewiz (May 16, 2010)

After charging the floodies but not the booster and shaving a little juice here and there I ended up with a 5:6 F:L current distribution and 0 cross current at rest. That's sitting at 136.2V (3.24 vplc).


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## Jamie EV (Oct 3, 2012)

which chemistry can handle high drain better?


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## dtbaker (Jan 5, 2008)

Jamie EV said:


> which chemistry can handle high drain better?


lead sags more under high load, and suffers from peukart's.


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## Jamie EV (Oct 3, 2012)

dtbaker said:


> lead sags more under high load, and suffers from peukart's.


I see...and it's heavy....so that's lead's weakness....what's Lithium's?


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## Ziggythewiz (May 16, 2010)

Lithium can take higher C rates, but the floodies have over 3x the (sticker) capacity. I want them to share somewhere between 5:5 and 2.5:5 F:L. 3:5 would be ideal.


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## Ziggythewiz (May 16, 2010)

Jamie EV said:


> I see...and it's heavy....so that's lead's weakness....what's Lithium's?


Just $$$ and potential damage if overcharged/discharged. In my setup the lead makes it impossible to overdischarge the lithium (without trying) and the JLDs will prevent overcharge.


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## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> Just $$$ and potential damage if overcharged/discharged. In my setup the lead makes it impossible to overdischarge the lithium (without trying) and the JLDs will prevent overcharge.


Sweet! In theory that's a marriage made in heaven. What's a JLD? I know dumb question...


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## Ziggythewiz (May 16, 2010)

In (my) theory it's a good way to get from lead to lithium without the huge upfront cost. If you have the money, straight LiFePO4 is the way to go. 

The JLD404 is a smart meter that reads V, A, counts AH, and has two programmable relays. At $65 I think it's the coolest device known to EVdom.


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## Jamie EV (Oct 3, 2012)

Good price for sure. 
I think I saw a 96 volt array of lithium cells (each 100ah) including bms and charger for like 5000. that's not bad considering the cost of Valence cells....yikes! Don't know if they are crap or not.


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## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> $5000 would get you a nice 128V 100AH set of CALBs.



Might have been cheaper. I just thought the fact that included bms and charger was good.


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## Ziggythewiz (May 16, 2010)

Finally got some new meters in, so I can rebuild my gauge panel without needing so many isolated DC-DCs (I managed to lose 2 and fried another one (that's 3 I've fried)).

Using 3 of these 50V DVMs instead of 2 99V meters will also give me more insight to the booster pack, since ~1/3 is SEs and ~2/3 is CAs.










Pack is working fine but I haven't pushed it for range or current. Surprisingly the lithiums seemed more affected by the cold snap we had the last few days than the floodies. Hopefully I can get a box on em this week and then make a couple for the floodies in the next couple weeks.


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## Jamie EV (Oct 3, 2012)

How cold was cold? Does charging not heat them up sufficiently?


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## Ziggythewiz (May 16, 2010)

Low 40's. They're done charging by midnight, so unless I plug em back in in the morning they're ambient (garaged most of this week) by the time I leave. Once I get em in some insulated boxes they should hold some of the charging warmth till morning.


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## Jamie EV (Oct 3, 2012)

it can't take much heating to keep the inside of a batt box warm. I mean how many btus could it need? Has anyone calculated that? How many watts? I would imagine you could use some of that electric radiant in floor heating stuff to do it. That would be compatible. I think it runs on 120volts....that small amount wouldn't draw much.

You could line your boxes with that maybe. I would be worried about the temp differential between the warm side and cold side of the batteries though. Maybe use spacing to get convection in there too?


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## Ziggythewiz (May 16, 2010)

I don't plan to add any heating. Just insulating and garaging should be good enough. After the first cold night when the lithium seemed saggy I finished getting the garage cleared enough to fit the bug in and no issues since. Now it's back in the 60s at night so no worries for a couple weeks.


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## Jamie EV (Oct 3, 2012)

That's not cold at all. My winters get down to -30 C below or so. -40 C on a bad day.


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## Jamie EV (Oct 3, 2012)

Average of about -15 in January. I would install a heater as a "just in case" precaution. It probably won't ever have to click on.


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## Ziggythewiz (May 16, 2010)

Yeah, just non-winter Houston cold. That's why I was surprised by the saggy lithium. I expected the lead to be super saggy at those temps, but it handled it better, though I don't know how much on either because I don't have all my meters on.

I don't plan to waste time, effort, and money on something I'll likely never need. I've got plenty of other things I don't have time for.


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## dougingraham (Jul 26, 2011)

Jamie EV said:


> You could line your boxes with that maybe. I would be worried about the temp differential between the warm side and cold side of the batteries though. Maybe use spacing to get convection in there too?


Probably you don't need to worry about differences across a cell. If you think about it these batteries are a stack of copper and aluminum foils with a thin electrical insulator saturated with electrolyte between them. The case might be different temps from one side to the other but there won't be much difference from one side of the internals to the other for very long.

It gets very cold here on occasion (I have seen -40 a couple of times in the last 38 years). I insulated my battery boxes (A little better than R3) and if it proves to be a problem I will put a heat plate under the cells. I expect a few jackrabbit starts will warm them up enough though. Heating this last summer was not an issue. The most I saw was about 10 degrees above ambient and with the cells in the insulated box they stayed cooler than the inside of the car when it was sitting in the sun. What I am trying to say is that the battery temps vary less than the outside air temp.


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## Jamie EV (Oct 3, 2012)

dougingraham said:


> Probably you don't need to worry about differences across a cell. If you think about it these batteries are a stack of copper and aluminum foils with a thin electrical insulator saturated with electrolyte between them. The case might be different temps from one side to the other but there won't be much difference from one side of the internals to the other for very long.
> 
> It gets very cold here on occasion (I have seen -40 a couple of times in the last 38 years). I insulated my battery boxes (A little better than R3) and if it proves to be a problem I will put a heat plate under the cells. I expect a few jackrabbit starts will warm them up enough though. Heating this last summer was not an issue. The most I saw was about 10 degrees above ambient and with the cells in the insulated box they stayed cooler than the inside of the car when it was sitting in the sun. What I am trying to say is that the battery temps vary less than the outside air temp.


That's good to know. I guess batt insulation can solve a lot of problems for extreme weather. R3 is next to nothing. If that's all that is needed, I'm glad.


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## Ziggythewiz (May 16, 2010)

Booster bonus feature:

Doing my semi-annual battery watering I noticed a a very loose terminal on a floodie. It was very discolored from the heat, and there were a couple spots where molten lead had formed. It it weren't for the redundancy provided by the booster pack the whole terminal would have blown off.  Also good that I happened to be watering today to notice.


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## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> Booster bonus feature:
> 
> Doing my semi-annual battery watering I noticed a a very loose terminal on a floodie. It was very discolored from the heat, and there were a couple spots where molten lead had formed. It it weren't for the redundancy provided by the booster pack the whole terminal would have blown off.  Also good that I happened to be watering today to notice.


Is there anything negative that you've observed so far?


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## Ziggythewiz (May 16, 2010)

Jamie EV said:


> Is there anything negative that you've observed so far?


Just that having a half lithium pack really makes me want a full lithium pack.


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## Ziggythewiz (May 16, 2010)

Update: I had my new draft instrument panel nearly complete, but while trying to calibrate one of the 50V DVMs it crapped out, so I have to wait a month or so for more to float over from China.

In another setback: My 120V controller no longer likes to run at 140V. I had to pull one 8V batt from the floodie pack, which means I'll need to crunch some numbers and pull 2-3 cells from the booster pack (too bad it isn't 4!) and refigure the ideal charge cutoff point.


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## Ziggythewiz (May 16, 2010)

I've been running 40 cells in the booster pack for a while now. It works well enough, but not nearly as good as it did with 42. 

With the charged resting voltages matched the boosters are charging the floodies significantly (while coasting or stopped) for the first mile, then just a little the next 2/3 of my commute, then the floodies are charging the boosters more than I'd like for the remainder. If I drive further than normal it increases until it's at .5C after ~20 miles, which is as fast as I'll let them charge, so I cut the booster at that point.

I might drop to 39 cells and play with the charge points a little, but still need to crunch the numbers.

One thing that's surprised me this winter is that the lithium booster pack is much more affected by the cold than the floodies, even though it's better insulated.

I'm pretty bad at keeping records, but for the days I managed to remember last month here's a comparison of outside temp vs load sharing for the booster pack. These are averages, so real-time numbers are a little more extreme.

I'd probably get better data if I compared the morning split with night-time lows and the afternoon split with daily highs.


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## rmay635703 (Oct 23, 2008)

mizlplix said:


> One will be charging the other, always, until equilibrium is met.
> 
> Miz


A diode fixes that problem.


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## Ziggythewiz (May 16, 2010)

Pulled a cell and reconfigured the booster box on Sat.

I've been charging to 133.9 V for a resting 132 (3.3 VPC).

Now charging to 132.5 V to rest ~130.65 (3.35 VPC).

Today's drive went well. Boosters carried a slight majority of the load and were always being recharged when idle @ ~2A. Will be interesting to see how they measure next time I go further than usual.


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## ga2500ev (Apr 20, 2008)

Ziggy,

I have a few questions and wanted to see if I could get a summary of your experiment so far.

My understanding is that you have parallel FLA and Lithium packs that have the same resting charge voltage. When the EV is driven, energy is drawn from both packs at a current ratio determined by the internal resistance of the respective packs. Typically this means that more current is drawn from the Lithium side. When the vehicle comes to rest again, since the Lithium put out more energy, current flows from the FLA pack, recharging the lithium pack. Feel free to clear up any misconceptions.

The objectives are using the Lithium pack to buffer the heavy current draw from the FLA, which both extends the cycle life and reduces the Peukert effect on the FLA. On the other side the FLA serves as a buffer for the Lithium which will keep the Lithium pack from going into deep undercharge. Also the FLA power participation facilitates using a smaller Ahr lithium pack as opposed to a Lithium only pack. Again feel free to clear up any misconceptions.

So my questions:

1. What exactly happens in a heavy current draw situation such as accelerating from a stop? Does the current draw ratio stay the same, or does it shift towards the FLA pack as the current draw gets higher? Is there any protection for the Lithium pack to prevent exceeding the maximum pulse/continuous current rating of the Lithium?

2. You have a post that indicates that after a long drive that the charging rate reaches 0.5C from the FLA to the Lithium pack. I presume this is because since the total energy of the Lithium is smaller than the FLA that the Lithium is depleted? Also you stated that the Lithium pack is then cut off. Does that mean that you no longer charge the Lithium pack, or that you allow for it to recharge from the FLA via a diode, but not contribute energy to the controller via a contactor? 

3. What are the effects if a booster pack is built with smaller Ahr cells than the 40 Ahr cells that you used for your test? Three small current draw cells are the A123 20Ah pouch and the Headway 38120HP 8 Ahr cell. Both of these allow for 20C continuous draw. There is also the headway 40152S 15 Ahr cell that can have a 10C continuous draw. With each with prices at $25 or less per cell, it would be possible to build booster packs in small chunks ($900 a slice for a 36 cell group for 120V nominal pack). I am unclear what happens when such a booster pack is heavily current driven in conjunction with the FLA pack.

Any clarifications or answers would be welcome.

Thanks

ga2500ev


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## Ziggythewiz (May 16, 2010)

Yup, good summary. The way the cells are now (39 cells, high SOC for 120V nom). I get nearly even sharing with a slight bias to the lithium. If it's cold it's a slight bias to the lead. Previously is was heavily weighted to the lithium but the opposite when cold.

1) The ratio is nearly the same under low amps as high amps. The cells can't exceed current ratings. My controller only goes up to 400A max, which matches their 10C pulse rating. I normally only pull 220-240 while accelerating anyway, so the boosters see 3C pulse, 1-1.5 continuous. The most they've ever seen is 6C. I'll probably shoot for 4-5C regularly if I ever get around to installing my other meters.

2) Yes, with my previous setup the further I discharged the more out of balance the strings would get and I'd turn the contactor off when the balancing current reached C/2. That was always just for a mile or two so after letting the car sit for a minute I'd reconnect the booster and it'd charge starting ~16A and settle below 5 very quickly and I'd just charge like normal.

That doesn't happen anymore. The largest balancing charge I've seen in my current config is 3.5A around 2/3 into my commute, and it just drops off from there. Once I get more meters in I'll do a range test to see if that holds true past the 22ish miles max I've driven.

3) I don't know how things would work out with a smaller booster. That was originally my intention but I couldn't stomach paying over $1.50/ah for a booster string that wouldn't significantly contribute to my range once fully lithium. I think it could be made to work very well with a little tweaking.

I'm rather hooked on the whole booster thing so 5-10 years from now (after switching to full lithium and upgrading controller, charger, and motor) I expect I'll have a LiFePO4 pack with a LiFePO4 SuperCapacitor Hybrid Battery as a booster.


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## PStechPaul (May 1, 2012)

I may very well do something similar if and when I build a road-going EV. But I plan to use SLAs instead of FLAs, and I intend to make a 250-320V battery pack with a three-phase 230VAC motor and VFD. I can get 12V 12Ah SLAs for about $20 each, including delivery, so that is about $0.14/Wh (although probably closer to $0.25/Wh including Peukert). They are 12 lb each (1 lb/Ah), compared to 0.6 lb/Ah for FLA:
http://www.tractorsupply.com/en/store/stowaway-battery-st27dc180

The cost for these FLAs is $85 or $0.067/Wh. For my purposes, I would need at least 20 of these for 240 VDC, which would be 26.4 kWh and about $1600. The weight would be 1300 lb which is a bit much but probably manageable especially if installed in a truck. If I can run at 350 wH/m at 40 MPH I would be pulling 14kW (18.6 HP) or 58A from the 240V pack, so with Peukert I would have a true 58 Ah or 1 hour of driving at 40 MPH or 40 miles (but probably 30 miles to be safe).

To get about the same performance with LiFePO4 I would need 80 x 60Ah cells which I might be able to get for $100 each including delivery, so $8000. They are about 7lb each for 560lb total. They would also need three times as many high-current interconnects, as well as a more sophisticated BMS, which adds maybe another 50 lb and $800. So 600 lb and $8600. 

If I made a combination with 50 Ah FLAs and 30Ah LiFePO4, I would probably spend $4300+$800 or $5100, and weight would be about 650+300 = 950 lb. There is also the complexity factor with two different chemistries.

As for long-term cost, the Lithium cells might last 10 years, and the FLAs 2.5 years, so that makes the lead system $6400 vs $8600. If you factor in the recycle salvage value of lead at $0.27/lb, the cost of a set of FLAs drops $350 to $1250/set or $5000 for 10 years.
http://www.earthworksrecycling.com/prices/index.html

I think LiFePO4 needs to drop to about 1/2 its present cost, and then the numbers look a lot better. I don't know if it really makes sense to use the combination at this point, especially for a high voltage pack.


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## ga2500ev (Apr 20, 2008)

Ziggythewiz said:


> Yup, good summary. The way the cells are now (39 cells, high SOC for 120V nom). I get nearly even sharing with a slight bias to the lithium. If it's cold it's a slight bias to the lead. Previously is was heavily weighted to the lithium but the opposite when cold.


I'm glad I've been reading this right.



> 1) The ratio is nearly the same under low amps as high amps. The cells can't exceed current ratings. My controller only goes up to 400A max, which matches their 10C pulse rating. I normally only pull 220-240 while accelerating anyway, so the boosters see 3C pulse, 1-1.5 continuous. The most they've ever seen is 6C. I'll probably shoot for 4-5C regularly if I ever get around to installing my other meters.


Is the 1-1.5C with the original setup of 40 Ahr cells? I was unclear when you got the second set of cells if you paralleled them with the original set or not (giving you 80 Ahr cells).



> 2) Yes, with my previous setup the further I discharged the more out of balance the strings would get and I'd turn the contactor off when the balancing current reached C/2. That was always just for a mile or two so after letting the car sit for a minute I'd reconnect the booster and it'd charge starting ~16A and settle below 5 very quickly and I'd just charge like normal.
> 
> That doesn't happen anymore. The largest balancing charge I've seen in my current config is 3.5A around 2/3 into my commute, and it just drops off from there. Once I get more meters in I'll do a range test to see if that holds true past the 22ish miles max I've driven.


Maybe you can clear up my confusion a bit. The action you described above is only when the car is stopped right? If the car is powered, then both strings are contributing energy to the controller/motor, and not to each other. So I'm just trying to make sure there isn't a situation when the FLA pack is both powering the motor and charging the booster at the same time.




> 3) I don't know how things would work out with a smaller booster. That was originally my intention but I couldn't stomach paying over $1.50/ah for a booster string that wouldn't significantly contribute to my range once fully lithium. I think it could be made to work very well with a little tweaking.


$1.50 an Ah seems to be about standard yes? Most of the sites I see has 40 Ah prismatics in the $58-$60 range which is just under $1.50/Ah. I've seen Headway 40152S 15 Ah cells for $23 which is about $1.53/Ah. I'm not so sure there's that big a price difference buying smaller cells. Consider if you were starting with 160 Ahr cells. They seem to be running about $210-$220 a cell. You can get 150 Ahr by tying 10 15Ah cells together. The cost at $23 each would be $230. So the total cost of a 36x160Ah stack is $7560 while the 360x15Ah setup is $8280. The total energy is 19 KWh vs. 17.8 KWh for a final $/Wh cost of $0.39/Wh vs. $0.46/Wh. But the second stack can be purchased as 10 individual $828 strings while the entire cost of the 160 Ah stack would need to be capitalized in the beginning.

I have access to 12Vx35Ah U1 wheelchair AGMs at $25 each. For $750 it's possible to put together a 12.6 KWh SLA stack in a 120Vx105 Ah 10S3P configuration at a weight of 750 lbs. Now I agree that adding less than 2 Kwh of Lithium isn't that helpful to range. But what are the effects in terms of buffering the deep discharge current when accelerating? What effect would that have on the range since the Peukert effect is lessened by Lithium string.


> I'm rather hooked on the whole booster thing so 5-10 years from now (after switching to full lithium and upgrading controller, charger, and motor) I expect I'll have a LiFePO4 pack with a LiFePO4 SuperCapacitor Hybrid Battery as a booster.


As you can see I'm interested too...

ga2500ev


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## Ziggythewiz (May 16, 2010)

ga2500ev said:


> Is the 1-1.5C with the original setup of 40 Ahr cells? I was unclear when you got the second set of cells if you paralleled them with the original set or not (giving you 80 Ahr cells).


At the beginning of the project I had a 124V nominal lead acid pack. 

I bought 16 CALBs (SE40s). I put 8 of those in parallel with 2 12V 29HMs (Sam's replacement for 29DCs). This was my proof of concept just to make sure things went well. It did so I added the other 8 cells giving me 16 SE40s in parallel with the 2 29HMs and 3 8V GC8s. 

I planned to run that for a long time gathering data, but ended up finding the cash to do the full booster pack, so I bought 26 more CALBs (CA40s). By this time I had replaced some old lead, giving me a 128V nominal lead pack (13 GC8s + 2 29HMs) and a 42 cell booster pack (16 SE40s + 26 CA40s).

My controller decided it didn't like being overvolted so I pulled 1 GC8 and dropped to 40 cells on the booster, then 39 to improve the balance.

I won't have a 80AH pack until the lead all dies in the next year or two and I buy another 40ish cells to put in parallel. So far I've only used series lithiums in parallel with lead.




ga2500ev said:


> The action you described above is only when the car is stopped right?


When coasting or stopped there's a balance current between the packs, sometimes one way, sometimes the other. Now that I've again found a good balance point it's very small, and is nearly 0 within a few minutes.




ga2500ev said:


> $1.50 an Ah seems to be about standard yes? Most of the sites I see has 40 Ah prismatics in the $58-$60 range which is just under $1.50/Ah. I've seen Headway 40152S 15 Ah cells for $23 which is about $1.53/Ah. I'm not so sure there's that big a price difference buying smaller cells. Consider if you were starting with 160 Ahr cells. They seem to be running about $210-$220 a cell. You can get 150 Ahr by tying 10 15Ah cells together. The cost at $23 each would be $230. So the total cost of a 36x160Ah stack is $7560 while the 360x15Ah setup is $8280. The total energy is 19 KWh vs. 17.8 KWh for a final $/Wh cost of $0.39/Wh vs. $0.46/Wh. But the second stack can be purchased as 10 individual $828 strings while the entire cost of the 160 Ah stack would need to be capitalized in the beginning.


I'd consider $1.25/AH to be a decent price for CALBs. Depending on the supplier the price/AH can be the same for small as large cells. Mine were cheaper and other prismatic brands are cheaper. Headways are more, and they've gone up instead of down; I wouldn't consider using A123 or other pouches because of the assembling hassle, same for non-threaded cyllindrical cells (some headways and many other brands).

While I think headways could make a great booster, I don't think you'd want to go that route for a full pack unless you really need C rates over 10. I think the few who have done full headway packs have said they wouldn't again. 360 cells would be a huge pain to connect, and I've heard they don't stay balanced as well as the prismatics, so that'd be another pain/expense.




ga2500ev said:


> I have access to 12Vx35Ah U1 wheelchair AGMs at $25 each. For $750 it's possible to put together a 12.6 KWh SLA stack in a 120Vx105 Ah 10S3P configuration at a weight of 750 lbs. Now I agree that adding less than 2 Kwh of Lithium isn't that helpful to range. But what are the effects in terms of buffering the deep discharge current when accelerating? What effect would that have on the range since the Peukert effect is lessened by Lithium string.


That could work. I'm not too familiar wth AGMs, but I doubt wheelchair batts are designed for much current. For comparison, my original pack was 10 125AH DC29s for ~$850 and lasted about a year.

I think my 12V batts are around a year old now, so unboosted they'd be about dead. I need to start doing an unboosted run every 1-3 months to see how they hold up on their own. Also for the reduced Peukert I need to get more meters connected and do a good range test.


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## TexasCotton (Sep 18, 2008)

Ziggythewiz said:


> Yup, good summary. The way the cells are now (39 cells, high SOC for 120V nom). I get nearly even sharing with a slight bias to the lithium. If it's cold it's a slight bias to the lead. Previously is was heavily weighted to the lithium but the opposite when cold.
> 
> 1) The ratio is nearly the same under low amps as high amps. The cells can't exceed current ratings. My controller only goes up to 400A max, which matches their 10C pulse rating. I normally only pull 220-240 while accelerating anyway, so the boosters see 3C pulse, 1-1.5 continuous. The most they've ever seen is 6C. I'll probably shoot for 4-5C regularly if I ever get around to installing my other meters.
> 
> ...


My bad Ziggy wish I read this thread orig instead startin the other.Where did you get your Lifepo4 cells from?
Like I sorta stated in other thread. I want to boost the 24vdc 80ahLifepo4pack with SLA or VRLA two 12volt 100ah which pair will give 24vdc 100ah SLA . Is same ah better or a little higher ah on the SLA side better. Also could you use a power diode between packs instead of contactor?


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## TexasCotton (Sep 18, 2008)

I am going to restate some my past issues (my apologies to OP)
I want to augment a Enginer PHEV RFE 24vdc 80ah Lifepo4 pack(this pack augments the OEM pansonic (Nimh 201vdc 7.2amp pack). Charge and balance of the RFE 24vdc 80ah Lifepo4 will be done outside of overall systems while vehicle unoperate(complex)However curious if I can apply a
24 vdc 90ah or 100ah SLA to boost the 24vdc 80ah Lifepo4 . Additionally thinking of using power diode to seperate the Lifepo4 from SLA and may possible use solar panels with charge control on SLA. Thanks ziggy for your posts


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## TexasCotton (Sep 18, 2008)

rmay635703 said:


> A diode fixes that problem.


Hope this will work in my application


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## Ziggythewiz (May 16, 2010)

Multiple threads on the same topic is great. It promotes further discussion and makes things easier to understand.

I think it works best when the lead is significantly larger than the lithium, otherwise the lithium will be doing nearly all the work and an imbalance will form the longer you discharge.

If things don't work as well as you want though you could always use one, then the other. 

I'm not aware of diodes that can handle over 100V+ @ 100A+. If they exist and are reasonably affordable it could help but you'd need separate monitoring on each pack. You need a contactor (or relay) anyway to break the connection during charging.


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## TexasCotton (Sep 18, 2008)

onegreenev said:


> As long as you don't over or under charge the lithium cells you will be fine. I had a disaster with my Prius booster pack to my lead acids. Prius cells over charged. I did not have a smart charger which would be important in the case of using different batteries. Lithium charge is nearly the same as lead acid except the balancing cycle and float cycle.
> 
> You going to use a lithium charger or lead acid charger?


 I have found and seen a lot of this on Lifepo4 packs where someone thinks you can trust a BMS to do its function on charge (plug,charge,and leave) However the reality is Lifepo4 get overcharged even with BMS. I am of the thinking that timed charge,voltage checks, bottom balance is a better solution.
I am hoping maybe a SLA booster pack to a PHEV Enginer Lifepo4 will work.


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## TexasCotton (Sep 18, 2008)

Ziggythewiz said:


> Multiple threads on the same topic is great. It promotes further discussion and makes things easier to understand.
> 
> I think it works best when the lead is significantly larger than the lithium, otherwise the lithium will be doing nearly all the work and an imbalance will form the longer you discharge.
> 
> ...


 My electronic and EV history is limited. But was thinkin maybe these could work
http://www.ebay.com/itm/DD104N16K-I...564?pt=LH_DefaultDomain_0&hash=item3a7ed4060c
http://blog.evtv.me/store/proddetail.php?prod=diode


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## Ziggythewiz (May 16, 2010)

Those could work. They just look rather weenie to me compared to my other connections.


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## TexasCotton (Sep 18, 2008)

Ziggythewiz said:


> Multiple threads on the same topic is great. It promotes further discussion and makes things easier to understand.
> 
> I think it works best when the lead is significantly larger than the lithium, otherwise the lithium will be doing nearly all the work and an imbalance will form the longer you discharge.
> 
> ...


I am thinking IGBT may work too. So you could not solar panel charge the SLA side while connected . I have heard and seen relay however comin up with how to diagram or wire in the relay not comfortable with. In your application you used a Tyco kilovac


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## PStechPaul (May 1, 2012)

The EVTV dual diode may be better because you can use both of them, while the one on eBay is two diodes connected as a half-bridge. The problem with diodes is that they conduct only in one direction, so each battery pack can drive the controller, but they can't charge each other, and regen will not work. It might be better to use a pair of big MOSFETs or IGBTs so the intrinsic freewheeling diode can steer the current out of the packs, and the gates of the devices can be activated for charging as desired. With MOSFETs, when the gate drive is applied, current can flow in either direction so it may be more efficient at lower current levels where the voltage drop from RdsOn is less than the diode drop.


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## TexasCotton (Sep 18, 2008)

PStechPaul said:


> The EVTV dual diode may be better because you can use both of them, while the one on eBay is two diodes connected as a half-bridge. The problem with diodes is that they conduct only in one direction, so each battery pack can drive the controller, but they can't charge each other, and regen will not work. It might be better to use a pair of big MOSFETs or IGBTs so the intrinsic freewheeling diode can steer the current out of the packs, and the gates of the devices can be activated for charging as desired. With MOSFETs, when the gate drive is applied, current can flow in either direction so it may be more efficient at lower current levels where the voltage drop from RdsOn is less than the diode drop.


 I kinda want a one way feed so that would be SLA to Lifepo4 to Nimh.The Lifepo4 Enginer (middle feed) could be switch off at any point during operation. Thinkin maybe high voltage power diode,IGBT, golf cart relay, isolated solenoid relay. possible choices


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## TexasCotton (Sep 18, 2008)

onegreenev said:


> Lead along side NiMH is not a good idea. Yes it can be done but introduces a high level of complex issues.
> 
> I agree that people see the illusion of saving money. It is that illusion that stops EV's from becoming main stream. I am for breaking the illusion.
> 
> Electric is it and Lithium is king. Cost IS less.


Lead has drawbacks to Lifepo4 in both weight and energy density.
.


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## TexasCotton (Sep 18, 2008)

may use something like this
http://www.ebay.com/itm/UNIVERSAL-1...US_Rechargeable_Batteries&hash=item5d37d0a874
to boost. I may try solar panel wired to solar controller wired to SLA battery wire to diodes to 24vdc Lifepo4 80ah and see what I get on my Prius, I am hoping to charge the Lifepo4 via SLA mainly kinda of a solar charger on wheels.


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## Ziggythewiz (May 16, 2010)

Don't expect mobile solar to do much charging, and be wary of buying batteries that have been sitting around unused.


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## Ziggythewiz (May 16, 2010)

Finally got around to hooking up my split pack meters and switches, 1 for each 13 cells. They're not calibrated (the last one I touched fried and set me back a couple months) so they'll rarely ever match but if they ever spread by a couple volts I'll know there's a problem.

Here's my latest spaghetti board prototype:


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## Ziggythewiz (May 16, 2010)

With warmer overnight temps I don't need the charger floating overnight anymore, so I've reduced booster charge voltage to 132.6 (3.4 vpc), giving a rest ~130.5V.


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## TexasCotton (Sep 18, 2008)

dtbaker said:


> lead sags more under high load, and suffers from peukart's.


 Hello
OP I was wondering in my application 24vdc lifepo4 80ah and 24vdc 100ah lead acid . Would a 80ah rated battery isolater between them work?


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## Ziggythewiz (May 16, 2010)

Usually an isolator is made for two or more batteries to charge together but discharge separately. That's not the case for a hybrid pack. You could use a heavy diode to separate them but that would make the discharge balance vary significantly.

As for ratings, you'd need to be rated for the peak or average current depending on the device. Capacity (AH) is irrelevant.


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## TexasCotton (Sep 18, 2008)

Ziggythewiz said:


> Usually an isolator is made for two or more batteries to charge together but discharge separately. That's not the case for a hybrid pack. You could use a heavy diode to separate them but that would make the discharge balance vary significantly.
> 
> As for ratings, you'd need to be rated for the peak or average current depending on the device. Capacity (AH) is irrelevant.


Has anyone consider like a ultracaps booster pack for lifepo4 battery pack


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## Ziggythewiz (May 16, 2010)

Yes, no need. Lithium is pretty good already and for the same weight is much more useful than supercaps, not to mention the price.


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## PStechPaul (May 1, 2012)

Today I just happened to pass by a local BatteriesPlus store and I asked them what their price would be for 12V 12Ah SLA batteries such as I recently got on eBay for about $22 each including shipping. I think theirs were about $49/1 and the best they could do for 20 pieces was $35 each. But their 8Ah batteries would be just $16.50 each. So, for my tractor, I could get 240V 8Ah or 1.92 kWh for $330 plus $20 to make the governor happy, so just about $350. I have demonstrated that my small riding mower with me aboard will run at 24V 15A or 360 watts, so I may be able to expect 1 HP or 750 watts to go faster or climb hills or do some work, and at that level I'd draw about 3 amps (0.4C) Peukert says I'll have 5.1 Ah and I should get a run time of about 1.5 hours. That seems pretty good. 

If and when I get back to my project (after my scheduled hip replacement April 22), I'll start a build thread. But this seems like a pretty good deal at $0.17/Wh (more realistically about $0.25 with tax and Peukert). The batteries have a 1 year guarantee and should be fine for occasional use, and I think they weigh about 5.25 lb each and an equivalent on eBay is about $17.50. But the batteries from BatteriesPlus are made in USA rather than China so I feel better about that. 

For an electric car as an adjunct to lithium cells, the 55 Ah deep cycle battery might be appropriate, and at a list price of $150 it's not bad at $0.23/Wh. In quantity they are probably much less, maybe under $100, or close to the smaller battery's $0.17/Wh. These are 42.5 lb so a 240V 55Ah 13.2 kWh pack would be 850 lb and about $2000. 

EDIT: I found out that the Werker brand from BatteriesPlus may be produced by Deka/East Penn but also could be from elsewhere, including some Mexican sources. There are some local reps for Deka/East Penn. 
http://www.dekabatteries.com/default.aspx?pageid=844
http://www.dekabatteries.com/ZipSearch.aspx?pageid=843

Their factory is about 2 hours north of me in Lyons, PA.
https://maps.google.com/maps?saddr=Cockeysville,+MD+21030&daddr=Lyon+Station,+PA&hl=en&sll=40.187267,-75.311279&sspn=2.135889,5.218506&geocode=FYFvWgId7IFu-ylngO2kZxLIiTEDNpvSwWL1mg%3BFfe0aQIdggd8-ynF9kpUf9PFiTG6EDsTNxblAw&oq=21030&mra=ls&t=m&z=9


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## Ziggythewiz (May 16, 2010)

Finally got around to doing a range test. I drove 41 miles before I got tired of going in circles. I cut out the booster ~27.5 miles in at 80% DOD. The floodies were probably still ~70% DOD when I stopped, so I have ~45 mile range to 80% DOD.

Average efficiency was 242 wh/m from the batteries, 332 from the wall.

I'll have to do another test soon without the booster to try to measure the increase in Peukert effect.


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## TexasCotton (Sep 18, 2008)

Hey OP
I have a question .What difference(if any) would there be in the discharge of these two examples.
two 12volt AGM 200ah lead acid
or
four 6volt 200ah golf cart deep cycle

The discharge rate would be 5ah
I am thinking the 6volt deep cycle may be the better performance


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## Ziggythewiz (May 16, 2010)

Depends on the exact batteries. I've heard some AGMs perform better, but others don't like high current as well.

I assume you mean a rate of 5A? Either should handle that fine.


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## TexasCotton (Sep 18, 2008)

yeah a discharge at a rate of 5ah/aka amp hour . ....I found 6 volt golf cart battery 200ah on a local basis and also thinking they may withstand my application not that the AGM would not but both closely price but the purchase of 6 volt deep cycle golf less footwork


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## dougingraham (Jul 26, 2011)

TexasCotton said:


> yeah a discharge at a rate of 5ah/aka amp hour . ....I found 6 volt golf cart battery 200ah on a local basis and also thinking they may withstand my application not that the AGM would not but both closely price but the purchase of 6 volt deep cycle golf less footwork


At 5 amp discharge rate both cells will give you the full 200 ah as this would be a 40 hour rate. The real problem is that once you get below about 50% state of charge the plates start sulfating at an accelerated rate so while your battery will do this once it will be hurt by doing so. I don't know which of the cell types you mention would survive this better. Some of the Lead Acid batteries would do this only a handful of times and they would be completely ruined.

If you only discharge to half (about 20 hours) either type should last a couple of years.


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