# Replacing Lead with Lithium



## dimitri (May 16, 2008)

80AH pack at 144V is not enough to drive Ford Ranger. You need at least twice as much capacity to stay within reasonable C rates.

I would not consider anything less than CALB 180AH cells or TS160 cells for Ford Ranger, at 144V.


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## Ziggythewiz (May 16, 2010)

I'm a floodie myself , but I'd recommend at least a 100ah pack.

Do you need to replace your charger too, or is it programmable?


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## Dougnutz (Aug 22, 2011)

dimitri said:


> 80AH pack at 144V is not enough to drive Ford Ranger. You need at least twice as much capacity to stay within reasonable C rates.
> 
> I would not consider anything less than CALB 180AH cells or TS160 cells for Ford Ranger, at 144V.


In what little driving I did I found that it rarely went above 200 amps. Unless I was gunning it. The Winston (thundersky) batteries are rated at 3C continuous which should stay in the same range 80*3=240 right? or am I missing something.

@Ziggythewiz The charger is programmable but I plan to get one that can charge off 220V as well. The current one is 120v only.

Oh and are you guys recommending 100Ah for range or C rate?

What are your thoughts on the AGM batteries?


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## dimitri (May 16, 2008)

Dougnutz said:


> In what little driving I did I found that it rarely went above 200 amps. Unless I was gunning it. The Winston (thundersky) batteries are rated at 3C continuous which should stay in the same range 80*3=240 right? or am I missing something.


2 issues here. First - 3C continuous is a max figure, assuming you can keep cells cool enough. In real life 3C for cruising current is too much and will stress your cells and they won't live long enough to be worth the $$$, so you'd end up throwing good money after bad. Also, it means 6C for acceleration, which could be 10-15 seconds at a time and its also too much for these cells if done often.

Second, 3C cruising means 20 minute runtime on a charge, which means low range. You didn't mention your range needs.


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## dimitri (May 16, 2008)

As a rule of thumb, in my opinion, any decent street vehicle should plan for 1C-1.5C cruising, 2C-3C acceleration. This will allow for good range and avoid stressing cells, which leads to long and happy life.


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## Dougnutz (Aug 22, 2011)

dimitri said:


> As a rule of thumb, in my opinion, any decent street vehicle should plan for 1C-1.5C cruising, 2C-3C acceleration. This will allow for good range and avoid stressing cells, which leads to long and happy life.


Thanks for the feedback. This does make sense. What are your thoughts on the agm batteries like the optima yellow tops? I find it really hard to get AH ratings for these batteries. Everything seems rated in reserve capacity.

Oh and I don't need a lot of range. Most trips will be 8 miles or less.


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## PTCruisin (Nov 19, 2009)

Ziggythewiz said:


> I'm a floodie myself , but I'd recommend at least a 100ah pack.
> 
> Do you need to replace your charger too, or is it programmable?



I second the 100Ah pack, but it really depends on your range/speed requirements. At 144V and 100Ah you will have approx 14.4kWh of stored energy, and assuming 80% DOD maximum, gives you 11.5kWh of useable stored energy. As a first-order approximation you will require around 300Wh/mile at 55mph, so you will have a range of about 38 miles.

I'm using 100Ah TS cells in a vehicle not much better than your truck aerodynamically, and I see around 150A drawn at 55mph and average 300Wh/mile.


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## dimitri (May 16, 2008)

Dougnutz said:


> I find it really hard to get AH ratings for these batteries. Everything seems rated in reserve capacity.


Which is a tell sign those aren't good for EV. They are not meant for high C rate and won't survive long. In lead acid world weight is king, more lead, better battery. 

If you don't need much range, why not get cheap golf cart floodies?


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## Dougnutz (Aug 22, 2011)

dimitri said:


> Which is a tell sign those aren't good for EV. They are not meant for high C rate and won't survive long. In lead acid world weight is king, more lead, better battery.
> 
> If you don't need much range, why not get cheap golf cart floodies?


Ya I'm leaning back toward floodies. For ebikes lead acid is such an anchor but for a truck the % of weight is much lower. 

I don't like the idea of buying a battery that won't last for the long term but for the sake of marital bliss I may put off spending 5-6k more on this vehicle until next year. 

I'm currently trolling through the gazillion posts by n00bs like myself to get an idea of what will work.


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## piotrsko (Dec 9, 2007)

define "long term": there is someone on this site that has about 6 years on his floodies. I believe that with careful management and care like the lithium bunch uses floodies aint that bad.


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## Guest (Sep 30, 2011)

The way I drive, no amount of careful management of lead batteries would last even close to 6 years. Lead is short distance and too much work to keep them alive and frankly just not a real viable solution for the electric car. Lets not nit pick here. Lead is not the way to go. Even the crappiest LiFePO4 cells are better than the best of the lead batteries. Lead is dead. I agree. I know. I built both.


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## Guest (Sep 30, 2011)

Lets stop dragging around the lead and drop it off at the nearest corner and move on. The future awaits and its not with lead acid.


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## Dougnutz (Aug 22, 2011)

@gottdi don't hold back, how do you really feel about lead?

Anyway I got the budget approved so it's a lifepo4...


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## Duncan (Dec 8, 2008)

Hi Dougnutz

I only need a short range so my solution was to use Headways - my pack is (in customs at Auckland but due here next week) 
2P 44S Headway 16Ah so I have
150v x 32Ah = 4.8Kwhrs
Max continuous (10C) 320 amps.
Burst (15C) 480 amps (10 seconds)
They are ~ $1.25 /Ah + shipping - less if you buy more
$ 1,777 + $400 shipping (to NZ) - I bet you get cheaper shipping to the US

Enough range, 
Enough performance, 
Light weight (44Kg) 
Low cost


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## Shane Jackson (Sep 28, 2011)

cruisin said:


> You are right. Typo. I sell them for $1.25 per ah, which comes to $225 per 180 ah cell. CALIB POWER is now their name which was Sky before. The copper contact connectors and bolts/washers are extra and the straps if needed are not available from CALIB. I am providing this information to you with no intent of promoting products or sales.


That's a reply taken from a post on my tread. May want to contact him and get a price quote.

I'm eyeballing an EV truck about the same specs as yours and I am thinking of getting the 60Ah's as they have the best specs on paper (shows 72ah @ 1c). I will start out with 2 strings of 45 to give 120Ah (144Ah if one is to believe the spec sheet) at 144V. That should be a good start and if needed I could always step up to a 3rd or 4th string. I'm guessing it wouldn't need the 3rd or 4th as the weight difference with 2 strings is around 1000lbs! That's a lot of weight. 

Shane


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## Dougnutz (Aug 22, 2011)

At this point It looks like I need to smash the piggy bank and purchase 100-120 AH to make power this truck. And even at that I need to limit the current to 2C cruising. Which I should be able to do considering that most of my trips will be short and at a max speed of 35-40 mph.


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## Dougnutz (Aug 22, 2011)

Pop quiz, what would you do.

245 ah of trojan floodies for about 4k delivered. 
or
120 ah of Calib lifePo for 8K delivered and in another year add 4k more for a total of 180ah (12K total)

1. The truck already has floodies so the swap would be simple.
2. With the LifePo I would need to limit the controller to about 250 amps to keep from hurting the batteries.

I can already hear the chant "lead is dead" but I would hate to murder a set of 8K batteries by over discharging, thus the 250 amp limit. But that effectively make the truck a 45-50 hp truck.


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## dimitri (May 16, 2008)

With 120AH CALBs you don't need to limit controller, they are rated to 4C and can certainly supply 500A for 10-15 seconds without much stress. As long as you don't drive with pedal floored all the time 120AH CALBs will work well and you probably won't even need to upgrade later unless your range needs will increase.


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## palmer_md (Jul 22, 2011)

I'm assuming you are still talking about a 144v pack. Reading between the lines I'm assuming you are going with a 60Ah battery and two strings parallel now, and a third in the future.

Based on those assumptions, I'd say that the lead pack and the two parallel pack will give you a usable capacity (kWh) that are almost exactly the same. The big difference is that the lithium pack will probably weigh half of the lead one, and you will have significantly less voltage drop on acceleration so it will feel more powerful. That is a double win (less weight and more usable power). Adding the third string will really give the car more range.

I think you are being a bit too conservative with the 250amp limit. They should be able to handle the 500 amps from your controller without issue for the short acceleration bursts you vehicle is capable of. You'll find that steady state consumption is well below your 250 number.

edit: I cross posted with dimitri...sorry for the duplication.


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## Guest (Oct 1, 2011)

With out a doubt, Lithium is the winner. Consider that the lead is $4K and will last, what, 3 years! You do the math. Not sure why you even need to ask that. So if you go lead you will be spending another $4K in three years. Performance sucks and that weight is a killer. 

LEAD IS DEAD. Why continue even thinking about it. There are enough lithium cars out here now to be able to say that with NO DOUBT.


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## Dougnutz (Aug 22, 2011)

I knew the "lead is dead" chant would come up. 

My main concern is that I will hurt the lithium pack in the next year while I take care of some of the little things the truck needs. Like power steering. 

Certainly the calib pack can take a 4C burst once in a while but I live on a hill that takes about a minute to climb. I need to make sure I'm not stressing the pack on that hill. I'm going to go out later today and see what the amp gauge says when I climb that hill, so I can talk real numbers.

It's interresting to me that most of the trucks (s-10's and rangers) in the Garage section use floodies. I'm sure it comes down to cost. For me the truck is a spare vehicle that will mostly be used 1-2 times a week mainly on the weekends for short hops. So the Lead would probably last a few years longer. 

I really want to go with the Lithium and most likely will. I just want to leverage the experience of the guru's around here. You guys have been looking at and dealing with conversions far longer than me. Spending 8K on the Lithium pack doesn't count any BMS or changing the charger. either. I'm pretty sure I can manage balancing the pack manually for a while but the charger will probably need to be replaced. Initially I didn't think I would need a new charger but looking closer at the slections on the charger it only has 4 modes and they are all for lead acid type batteries (Wet, gel, agm, etc). It says "all types of batteries" but really means all types of lead acid batteries. The total voltage on the AGM setting would match the lithium pack total charge voltage, but it sounds like the charging profiles are different.

So there's about another grand in hidden costs with the lithium. Still it's a better pack but it's really stretching the budget for something that is a weekend runabout.


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## Duncan (Dec 8, 2008)

_Pop quiz, what would you do._

I bought Headway batteries - similar cost per Ah and rated at 10C continuous
If you don't need the range you can fit a smaller pack


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## Guest (Oct 1, 2011)

It's not a chant, Its a fact. Why do you think you'd hurt your lithium cells by adding components later? Never tap into part of the pack for voltage needs. I own some older Hi-Power Cells and they have a factory rating of .5C continuous and I have been successfully using them in the 2C to 7C range. They give the power and don't overheat. Cruising they provide 2.5C at freeway speeds and on the hill your looking at a very short time each time anyway. I'd not worry your head on such trivial things since the data is available and that the successful lithium cars can be checked. 

Pete


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## GizmoEV (Nov 28, 2009)

You really need to stick with lead. If you don't you are likely to figure out what those of us have who have switched from lead to LiFePO4 cells have found. Here is a partial list:


LiFePO4 cells are more efficient so you can actually drive further on a kWh of electricity from the wall than you can with lead thus causing the power company to not make as much profit which might hurt them.
The lighter pack will mean that your brakes, tires, and suspension parts won't wear out as much so you won't be supporting the various suppliers as often since you won't need replacements as often.
The voltage doesn't sag as much so acceleration will tend to be higher and you will likely leave the other cars behind at the traffic lights and they might get jealous.
You don't have to water the cells so you won't be supporting the local grocery store with your distilled water purchases.
You will possibly drive your EV more than before because you aren't spending all your time cleaning your terminal connections since there is no acid mist to worry about.
The acceleration when the pack is near 20%SOC is nearly the same as it is at 100%SOC so you will have to read your Ah counter to know how "full" your EV tank is rather than go by the feel
You can safely parallel individual cells and they will act like a single cell (I use a 2p20s pack of 100Ah cells)
The cells don't really drift much if at all so you can safely run without a BMS for quite a while (6000 miles and 11 mo for me)
Charging takes less time for the same energy storage since the voltage stays flat for so long and rises sharply at the end. No long absorption and then an equalization stage like lead acid needs.
There are many more but please stick with lead acid. We are trying to keep the above information a secret. Your own personal experience with LiFePO4 would just makes it harder to do so.


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## GizmoEV (Nov 28, 2009)

BTW, what charger do you have right now? I don't remember seeing you state that any where. I just had mine reprogrammed for LiFePO4 and it works solid and consistently every time. I have both a Zivan NG1 and NG3. It cost me <$100 including shipping both ways for each unit.


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## Guest (Oct 1, 2011)

GizmoEV said:


> You really need to stick with lead. If you don't you are likely to figure out what those of us have who have switched from lead to LiFePO4 cells have found. Here is a partial list:
> 
> 
> LiFePO4 cells are more efficient so you can actually drive further on a kWh of electricity from the wall than you can with lead thus causing the power company to not make as much profit which might hurt them.
> ...


Aaaaah man, guess I should have done a better job keeping things a secret. If you want it kept secret then don't tell me.


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## tomofreno (Mar 3, 2009)

> There are enough lithium cars out here now to be able to say that with NO DOUBT.


 Although I have had an LiFePO4 pack longer than you Pete, I would not say that. No one has 8 or 10 years on a pack yet, and most less than 5 so we don't know for certain that they last any longer than that. We keep stating about 10 years based on the spec'ed cycle life, and something repeated often enough becomes "common sense" whether it is true or not - as long as it is not demonstrably untrue. 

I give a much more guarded response - that they are spec'ed at 3000 cycles for 70% DoD (CALB cells) which would be around 10 years, but no one has had them that long so it is unknown how accurate the spec is, nor how operation at high discharge currents in an ev effects their lifetime. Not that I don't recommend LiFePO4, just don't like to give an unqualified recommendation, and I certainly agree that performance is much better as far as less sag/lower Peukert, less affected by temperature.


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## Guest (Oct 2, 2011)

China usually seriously under rates their items. I have one of the crappiest brands according to all who have purchased and used lithiums. They are just magic. Mine are rated at .5C but will give with out balking 7C. As all batteries, they do sag at those high levels but all batteries do that. These cells will keep up with any of the top brands of LiFePO4 cells currently made to date. So, I have no trouble stating that. Nor should you. 

Pete


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## EVfun (Mar 14, 2010)

tomofreno said:


> Although I have had an LiFePO4 pack longer than you Pete, I would not say that. No one has 8 or 10 years on a pack yet, and most less than 5 so we don't know for certain that they last any longer than that. We keep stating about 10 years based on the spec'ed cycle life, and something repeated often enough becomes "common sense" whether it is true or not - as long as it is not demonstrably untrue.
> 
> I give a much more guarded response - that they are spec'ed at 3000 cycles for 70% DoD (CALB cells) which would be around 10 years, but no one has had them that long so it is unknown how accurate the spec is, nor how operation at high discharge currents in an ev effects their lifetime. [snip]


I'm aiming to find out what they think of high discharge rates! I've got the controller cranked up to suck them down at 7.5C (450 amps for 60 amp hour TS cells.) It's a tiny 6.1 kWh pack (32 cells.) They hang at right about 2.63 volt per cell and lightweight buggy keeps ending up somewhere other than where I put my right foot down. It will take a few years of work to figure out if they mind, but I'll take one for the team.


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## GizmoEV (Nov 28, 2009)

EVfun said:


> I'm aiming to find out what they think of high discharge rates! I've got the controller cranked up to suck them down at 7.5C (450 amps for 60 amp hour TS cells.) It's a tiny 6.1 kWh pack (32 cells.) They hang at right about 2.63 volt per cell and lightweight buggy keeps ending up somewhere other than where I put my right foot down. It will take a few years of work to figure out if they mind, but I'll take one for the team.


And I went the opposite direction. I have a 200Ah pack and never see more than 500A out of them. My WOT cruising current is about 130A so these cells are getting babied by comparison. Even when they have half the capacity left I'll still have over 30 miles of range. It will be great to compare results in a few years. I hope you are tracking total Ah delivered by your pack. The CycleAnalyst does this so I will have a relatively good idea of how many "cycles" this pack will have done.


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## tomofreno (Mar 3, 2009)

> China usually seriously under rates their items.


 That is a very broad statement. What data do you base it on?


> I have one of the crappiest brands according to all who have purchased and used lithiums. They are just magic. Mine are rated at .5C but will give with out balking 7C. As all batteries, they do sag at those high levels but all batteries do that.


 That doesn't tell us how long they will do that. They might crap out next week, next year, or 10 years from now. My point is that we don't have any data on lifetime, only specs, the basis of which we have no idea. Mine are performing well and I've noticed no change in performance over two years, but I can't point to any data that says they will last 10 years, only a spec. Part of the justification for choosing them over lead is economic - they cost more but will last much longer and give better performance. No argument on the latter, the former is still a question mark. Maybe in a few years evfun and others will have enough cycles to give a more definitive answer. It will take me about 8 more years to get to 3k cycles.


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## Dougnutz (Aug 22, 2011)

Well lithium it is. I got the budget aproved 

I did consider head ways but I do eventually want to get the total ah up to 180 or 200. With 16 ah cells that's a lot of connections to deal with. In the long run I think the larger cells will be easier to manage. 

Next up is dealing with the charger. I have a quick charge, sco14410 charger. I don't know if it can be modified to charge lithium of not. I kind of doubt it. Worse case I'll sell it.


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## GizmoEV (Nov 28, 2009)

Looking at one site which sells that model charger I highly doubt it is reprogrammable. You could start looking on places like eBay for used chargers which can be reprogrammed for you or look at the various new ones available. I like the way the Zivan chargers work because they are very consistent and fool proof but they are only programmable for one profile at a time and you have to send them into get that changed. Also, they are either 120V input OR 240V input, not both. The Elcon chargers can have more than one profile so you could have different numbers of cells programmed in so that if you increase the number of cells in series you can field change the charger.

If you are planning on increasing the capacity of your pack in a year or two I'd recommend you go with paralleling individual cells rather than paralleling separate strings. The advantage is that each parallel set will act like one cell and provide only one monitoring point for the set. Also, due to the Voltage vs SOC nature of these batteries cells with differing capacity will still work nicely. Since each cell in the set will be forced to the same terminal voltage they will each hit full/empty at the same time.

Suppose you are going to start with a 200Ah pack and later want to raise that to 300Ah. You could get 90 100Ah cells and create a 2p45s pack. Later you could purchase 45 more 100Ah cells (hoping they are the same form factor) and add one new cell to each of the paralleled old cells. The new cells will likely have a little higher capacity than the old ones so they may work a little harder but they will still reach full/empty at the same time as the other two in the parallel set. I suppose the only trick is to build your battery boxes so that you can add the extra cells in later.

BTW, do you have a good Ah counter? If not you need to get one. The CycleAnalyst (ebikes.ca) isn't too expensive, there is also the EV Display which dimitri sells. See his ad in the side bar.


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## drgrieve (Apr 14, 2011)

EVfun said:


> I'm aiming to find out what they think of high discharge rates! I've got the controller cranked up to suck them down at 7.5C (450 amps for 60 amp hour TS cells.) It's a tiny 6.1 kWh pack (32 cells.) They hang at right about 2.63 volt per cell and lightweight buggy keeps ending up somewhere other than where I put my right foot down. It will take a few years of work to figure out if they mind, but I'll take one for the team.


Thanks for the data. I'd like to add this to my spreadsheet can you please check my maths - I assume the starting voltage is 3.3. Or if you could give another voltage reading at another amp load that would also suffice.

So 3.3 - 2.6 = ~ 0.7 volt drop for 450 amps. Your pack resistance is 1.5 milliohms.


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## Dougnutz (Aug 22, 2011)

GizmoEV said:


> Looking at one site which sells that model charger I highly doubt it is reprogrammable. You could start looking on places like eBay for used chargers which can be reprogrammed for you or look at the various new ones available. I like the way the Zivan chargers work because they are very consistent and fool proof but they are only programmable for one profile at a time and you have to send them into get that changed. Also, they are either 120V input OR 240V input, not both. The Elcon chargers can have more than one profile so you could have different numbers of cells programmed in so that if you increase the number of cells in series you can field change the charger.
> 
> If you are planning on increasing the capacity of your pack in a year or two I'd recommend you go with paralleling individual cells rather than paralleling separate strings. The advantage is that each parallel set will act like one cell and provide only one monitoring point for the set. Also, due to the Voltage vs SOC nature of these batteries cells with differing capacity will still work nicely. Since each cell in the set will be forced to the same terminal voltage they will each hit full/empty at the same time.
> 
> ...


 
I ordered a cycle analyst last week. I have one on my ebike already so I'm familiar with the operation. Not that they are tricky but I like the format.

I'm pretty sure you are right about the charger too. I'm going to investigate it a little more but at this point the plan is to sell the charger (ebay or similar). I am leaning toward the Elcon chargers. Mainly because I want to be able to charge from 110 or 220 outlets.


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## EVfun (Mar 14, 2010)

That models my little cells quite well. Just to note though, my *cell* resistance is 1.5 milliohms, my pack resistance is 48 milliohms. Wow, that is up to 9.7 kW of heat being created (if all the sag was internal resistance and none local depletion.) The cells never feel warm after a drive, even a spirited one. 

Is the cell resistance of the 180 amp hour cells was only 1/2 mO? If so a pack of those cells would make a fast EV if you where willing to demand 7.5 C from a string of 50 cells. A flat peak power of around 200 horsepower jammed into some unsuspecting econobox...


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## GizmoEV (Nov 28, 2009)

Dougnutz said:


> Spending 8K on the Lithium pack doesn't count any BMS or changing the charger. either. I'm pretty sure I can manage balancing the pack manually for a while but the charger will probably need to be replaced.


Since it looks like you are going the manual BMS route, at lease initially, you will want to start working on how you are going to balance your batteries. There are three modes of thought on this. Assume the batteries are all at the same SOC (state of charge) when you get them, top balance them, or bottom balance them. My understanding is that CALB batteries usually come with a sheet giving capacity and internal resistance for each cell. Some claim that all the cells are brought to 50% SOC at the factory but others have said that doesn't seem to be the case. I don't have the trust that all the cells are at the same SOC when I get them so I would either top or bottom balance them before assembling my pack.

And to be clear, I'm only talking about LiFePO4 prismatic cells, not lipoly or any other type of cell. I have a pack of TS-LFP100AHA cells.

In my case I did a top balance because I started out with a BMS. I have since removed it, not because it caused problems but because I'm trying to determine if one is really needed. The benefit of top balancing is that all the cells will reach full at the same time regardless of variations in capacity. This means there is unlikely to be a cell or two which will go way over voltage at the end of charging. The disadvantage to top balancing is that if you run the pack empty you are very likely to kill one or more cells: the one(s) which go empty first. This can happen very quickly when under load. By quickly I mean a second or two, maybe even less.

The advantage of bottom balancing is that if you do run your pack empty all the cells go empty at the same time so your car will just stop. None of the cells have the energy to "force" the low ones into reversal so everyone is happy even though their tongues are hanging out. If you always stay above 80% DOD (depth of discharge) you should never see the bottom with either top or bottom balancing, however, as the pack ages and the capacity diminishes it is possible that what used to be 80% DOD is now 100% DOD so you might inadvertently run your pack flat. I haven't experienced this yet my self and I haven't heard of anyone else reporting on this yet either. I don't know how many are running non-BMS packs right now but I suspect it is fewer than those running with a BMS but I really don't have any data on it. The disadvantage to bottom balancing is then on the charging side of things. A Gizmo owner in FL is converting his rig over to LiFePO4 and went with CALB 180Ah cells. He bottom balanced his pack and found that on charging the assembled pack to 3.465vpc (69.3V, 20 cells) that one hit 4V, another 3.8V and a couple of others in the 3.6V range with the rest down around normal. I personally would not want to have a spread that great in my pack. If I had the same pack as he does and I didn't have any spare cells I would go with top balancing and stay away from the bottom.

BTW, I recommend buying a few spare cells so if you have some duds or something you will have identical replacements from the same factory run. In the case of the FL Gizmo owner I suggested he replace the low capacity ones with his spares. Also, any spares you have should be stored partially charged. They will last much longer that way.

If you buy smaller cells and then parallel them you can match the cells by capacity. Match them up so that the total capacity of the cells in a parallel group is the same as the next group and so on. Keep in mind that if you go with parallel groups that you will need more than 1 connecting strap per battery. I've attach a picture of my batter box to help you get an idea of what it might look like.

I'd recommend you consider building a half-pack voltage monitor for your pack. I did a post on how I made mine on my blog linked in my signature line. It is very simple to do. It will let you know if one half or the other has something going wrong even when the pack voltage doesn't indicate any thing abnormal.

End of charge voltage. The charging of LiFePO4 cells specifies a target voltage along with an ending current. The documentation with my TS cells said to charge to 4.00V and hold until the current tapered to 0.015C. For my 200Ah pack that would be an ending current of 3A. I do not know what CALB or others list as the end of charge criteria but my preliminary testing shows that if the ending current is lower than 0.015C that the ending voltage can/should be lower too. LiFePO4 cells are nearly 100% efficient so even very low currents will still charge them. Furthermore, there is very little energy above 3.4V any way so I don't see any reason to charge to much over that point. If you charge to only 3.4V, however, it will take a long time to reach 98-100% SOC. Charging to 3.465V does not take very long and even less time to higher voltages. This is because the voltage curve is so steep at the ends. The farther up the voltage curve you charge to, the later in the charge sequence the charger goes before switching from Constant Current to Constant Voltage. My charger tapers the current down to nearly nothing so I have found that charging to 3.465-3.5vpc is just fine and I don't leave much if any capacity on the table. Some bench testing I did with a 100Ah cell shows less than 1% is left.

I'll be blogging about my ~6000mi 11 months without balancing and what I'm doing now relatively soon so check my blog in a week or two if you are interested.


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## Dougnutz (Aug 22, 2011)

@GizmoEV wow that's a lot of info. Thanks for taking the time to go into such detail. It's going to take me a little bit to sort through it all. 

I had been debating the pro's and cons of parralling the cells vs paralleling the strings. I was leaning toward paralleling the cells but the downside to that is that when I add more cells it's a lot easier to add a string of 48 cells rather than take the whole pack apart. But probably worth it.


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## gsmith191145 (May 1, 2011)

Dougnutz said:


> Pop quiz, what would you do.
> 
> 245 ah of trojan floodies for about 4k delivered.
> or
> 120 ah of Calib lifePo for 8K delivered and in another year add 4k more for a total of 180ah (12K total)


I got interstate 232 AH batteries for 90 a piece. Just FYI. Your figures are off. Also I personally got about 4 years out of my lead pack. However, if you purchase the military grade lead batteries that are 345 AH they are guaranteed for several years.

If you got the money for lithium go for it.


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## GizmoEV (Nov 28, 2009)

Dougnutz said:


> @GizmoEV wow that's a lot of info. Thanks for taking the time to go into such detail.


You are welcome. I figured that people would be more benefited if I could put that info into one post and not make them have to sift through the strong opinions on one side or the other of things. The hard part is that no one has 10 years on their packs and even if they did, every situation is different. One has to consider cycle depth, number of cycles, charging rate, discharge rate, temperature range, temperature differences from one part of the pack to another, charge ending voltage and current, balance method, time at 100%SOC compared to time at partial SOC, contact preparation and maintenance, and a host of other things which can make a comparison difficult.

Oh, in case I didn't mention it, don't play with your cells until you are nearing ready to install them in the vehicle. Unless, of course, you are learning about their characteristics. If/when you decide to balance them hook them up in parallel and charge to the top (~3.6V) or discharge to the bottom (~2.8V) and let them sit in parallel for a while before breaking them apart.

If you discharge in parallel you might do what the guy in FL did. He picked up some 1/16" stainless steel welding rod. He found that a 3 foot length had about 0.5 Ohms of resistance so that gives a current of around 6A for each rod. They are long enough that they won't get too hot. He just put a loop in each end for the terminal bolt and made a tall hoop out of it. It stayed out of the way and discharged his pack just fine. When nearing the end he would just start removing the hoops to reduce the current draw.



gsmith191145 said:


> I got interstate 232 AH batteries for 90 a piece.


Are those deep cycle golf cart type and is that a current price or one from a while back? That is a good price if they are. After using LiFePO4 I'll never go back to lead for a road going rig.


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## Dougnutz (Aug 22, 2011)

Ok I should probably know this but what is the lithium equivilant of 144v lead acid (12 x 12v batteries).

I'm using a curtis controller http://curtisinstruments.com/?fuseaction=cDatasheets.dspListDS&CatID=1&siteID=1

model 1231C 96-144 V

Now hot off the charger the lead acid pack can be as high as 172v but nearly instantly drops to a "full" rating of 166V. This seems about right as it's 13.5v per pattery. So if I use 166v as a safe limit on the charger and I am using thundersky lifeYpo they have a max voltage of 4 volts aproximately 41-42 cells will do that.

Knowing that lithium has much less sag then lead I am tempted to go with a 40S string of the thundersky battery. However 4 v is max charge and I know they won't really stay at that for any amount of time, I'm not sure that the nominal voltage is for these batteries either.

With all that in mind I see lots of examples of people with 40-45s lithium batteries calling their packs 144V.


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## dimitri (May 16, 2008)

Nominal is 3.2V , so 45 cell pack is 144V nominal.

Max voltage can vary from 3.45V to 3.85V, depending on your battery management strategy, which involves many decisions I won't go into, but you have to make sure your charger's max voltage does not exceed your controller's max voltage, or you won't be able to drive immediately after charge.

Some people pick final cell count to match existing charger to avoid reprogramming.


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## palmer_md (Jul 22, 2011)

I have a 42s pack. Use 3.65 V/cell on your charger instead of 4.00. The battery will be 3.3 as soon as you remove the charger.


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## Dougnutz (Aug 22, 2011)

I would size it to my charger but the charger is designed for lead acid batteries so I'm going to need a new charger anyway.

The LifeYPo4 thundersky's seem to have a slightly higher charge voltage compared to the LifePo4 versions

LFP60AHA nominal 3.2, low cut 2.8 high cut 3.8
http://lithiumstorage.com/index.php..._id=29&zenid=0808c6ba1752cc24d3ae1769a8721786

LYP60AHA (yttrium doped version)
nominal ??, Low 2.8, high 4.0


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## dimitri (May 16, 2008)

All LiFePO4 cells behave virtually the same way and have 3.2V nominal voltage. Difference in spec sheets and some minor variations of chemistry can be ignored in high level discussions and planning. The "upper knee" can be a little wider in some brands like TS/Winston, but it has no effect on their nominal voltage.


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## Dougnutz (Aug 22, 2011)

Ok so I found a source of thundersky 160 ah batteries local to me. CurrentEvtech. I have seen some very sketchy reviews but he answered the phone and they are local so I can drive up, pay and walk out with batteries. That's hard to beat. 

The downside for me is that I will only be able to afford 40 cells vs the 45 if I went with calib. I don't think it will matter that much, I'll have to buy a charger either way so I'm planning to buy the matching Elcon 1.5Kw charger.

I suppose I will loose a little top speed (and HP) by dropping to 40S but for my application I don't think it will matter that much. 

Do any of you guys think 40s over 45s will be that noticable?


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## gsmith191145 (May 1, 2011)

GizmoEV said:


> Are those deep cycle golf cart type and is that a current price or one from a while back? That is a good price if they are. After using LiFePO4 I'll never go back to lead for a road going rig.


Yes they are 6 volt deep cycle golf cart batteries. They are the interstate equivalent to T-105's. 

Lithium would be very nice and light weight. Hopefully this will be my last lead acid pack.


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## GizmoEV (Nov 28, 2009)

Dougnutz said:


> Ok so I found a source of thundersky 160 ah batteries local to me. CurrentEvtech. I have seen some very sketchy reviews but he answered the phone and they are local so I can drive up, pay and walk out with batteries. That's hard to beat.


I bought my cells through Dave Kois when he was at the former EVC place. I first met him here in Kelso/Longview, WA when he drove his converted RAV4 to one of our first LCCEVA meetings. I found him knowledgeable, helpful, and not a hint of dishonesty. I definitely would buy from him again.



> The downside for me is that I will only be able to afford 40 cells vs the 45 if I went with calib. I don't think it will matter that much, I'll have to buy a charger either way so I'm planning to buy the matching Elcon 1.5Kw charger.


Make sure you get the charger programmed for 40 and more cells. I've heard that they can put 10 different profiles in them so decide on what the maximum number of cells you might go to and have the charger programmed to handle that number of cells. Also your ending voltage per cell will determine how you have the charger programmed. If the options for the Elcon are the same as for the Zivan chargers you will have several to choose from. Depending on the ending vpc you have available you can then determine what increment you want the ending voltages to be for each profile. Suppose you can only choose 3.65vpc. You can then have the charger programmed for cell counts of 38, 39, 40, ..., 47. If you install 40 cells and set the charger for the 38 cell setting the cells will be charged to 3.4675vpc average. This would be a conservative setting since you are planning to run without an on board BMS, at least initially. If you later decide to install a BMS which needs a 3.65vpc ending voltage merely change the profile. Another advantage of starting with a profile with a lower cell count than you are going to install allows you some wiggle room should a cell go bad on you. You will be able to remove a couple of cells and still charge while you wait for replacements to come in.


```
[FONT=Fixedsys]
V per Cell =>    3.20      3.50      3.60      3.65
# of Cells  Nominal V    Pack V    Pack V    Pack V
   38          121.60    133.00    136.80    138.70
   39          124.80    136.50    140.40    142.35
   40          128.00    140.00    144.00    146.00
   41          131.20    143.50    147.60    149.65
   42          134.40    147.00    151.20    153.30
   43          137.60    150.50    154.80    156.95
   44          140.80    154.00    158.40    160.60
   45          144.00    157.50    162.00    164.25
   46          147.20    161.00    165.60    167.90
   47          150.40    164.50    169.20    171.55
   48          153.60    168.00    172.80    175.20[/FONT]
```



> I suppose I will loose a little top speed (and HP) by dropping to 40S but for my application I don't think it will matter that much.
> 
> Do any of you guys think 40s over 45s will be that noticable?


It will be noticeable if you drive with 45 cells and then remove some and go back to 40 cells. You might not notice the difference because your rig will drive so much better with 40 cells than it did with lead acid. Except on acceleration the pack voltage will be relatively close to the nominal voltage. How much does the lead acid pack sag? Go with the 40, add a few more later if your requirements change.


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## EVfun (Mar 14, 2010)

You are looking at some good TS cells, I think most of these where from the same batch of cells shipped to EV Components as my 60 amp hour cells (or perhaps the shipment after mine.) I got my cells from EVC in early March 2010, I think because he knew I could show up at the shop anytime -- I live near by. 

If you have a 144 volt controller intended for a lead car it can take (not necessarily power the motor, but can see on the input when off) at least 180 volts. That is because a 144 volt pack of flooded lead can regularly hit that on charge (7.5 volts per 6 volt battery.) At the same time, the controller can clearly operate up to at least 165 volts because otherwise it would have problems operating fresh off a charge. With these numbers in mind, you should be fine with up to 48 cells if you limit the charging voltage to less than 3.7 volts per cell. 45 cells is commonly called a 144 volt pack and is a good number to shoot for. Lower voltage will generally only limit the top speed in each gear. If you can hit 70 mph now the reduction to 128 volts (40 cells) should be no problem, pulling perhaps 5 mph off the top speed.

You don't need to push the Thunder Sky cells up to 3.7 volts per cell or higher when charging. I only charge my TS cells to 3.5 vpc. I'm giving up around 2% of the full capacity, but Lithium lasts longer (and has lower internal resistance over time in theory) if not fully charged. Lead acid batteries have a shorter life in increasing internal resistance if not fully charged regularly. Lead thinking has to be ditched for Lithium batteries. Lithium batteries are actually easier to use because you don't need to figure out how to get every cell in a EV long series string fully charged regularly.


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## Dougnutz (Aug 22, 2011)

I opted for the 40 cells and a new charger that was programmable to higher voltages (more cells) when I expand someday. I was really drooling over those last 5 cells but I have already murdered my budget 

Considering how bad the lead acid pack is currently I'm sure that the Lithium will feel like nitrous . To give you an idea of how bad my lead pack is, If I pull out of my driveway on a full charge and head uphill, I will hit 300amps and the voltage will sag steadily down to the LVC of the controller at 67V within one mile.

Anyway,

CurrentEvTech had a nice selection of cell configurations to choose from. Banded in 3,4,5, and 9 packs. I purchased all 5 cell packs. Since I haven't built battery boxes yet they should sit pretty nicely where the old 12v packs are. All you guys have been such great help, you gently pointed out obvious oversights on my part and I am now confident in my purchase.

The next steps are to digest all the info about charging and balancing the pack. I took a quick read on all the cells last night and 36 of them were charged to 3.30 v with the remaining ones at 3.31 volts. That seems like a pretty good start. The really awesome thing about buying locally is no shipping worries, and instant gratification


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## Dougnutz (Aug 22, 2011)

It took me a while to get all this sorted out but finally the batteries are in and the truck is running great. I opted for a top balance (for a variety of reasons). I’m expecting to monitor the pack closely for a while and probably rebalance sooner rather than later. 

One thing I found out is the cells I purchased are likely to be 18 mo. old or so. I don’t know this for sure but regardless they are thunder sky branded (not Winston) and have the older part numbers. But according the paperwork I have they say they have the Yttrium added. Does anyone know if the production date is encoded on these anywhere?

In any event they are working quite well, huge improvement. But I am a little gun shy about running the pack with no warning system. I have a cycle analyst hooked up and my longest trip so far only used 24 ah, I typically only use 14ah so capacity isn’t really a problem. But I’m looking for ideas for an early warning system. 

I’m like the idea of splitting the pack in two and comparing the two halves but I ended up with 45 cells after all so that won’t quite work. Suggestions?


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## EVfun (Mar 14, 2010)

Dougnutz said:


> It took me a while to get all this sorted out but finally the batteries are in and the truck is running great. [snip]
> 
> One thing I found out is the cells I purchased are likely to be 18 mo. old or so. I don’t know this for sure but regardless they are thunder sky branded (not Winston) and have the older part numbers. But according the paperwork I have they say they have the Yttrium added. Does anyone know if the production date is encoded on these anywhere?
> 
> ...


Good to hear, once you do Lithium it's hard to get that same EV high from Lead. 

Did you get these cells from Current EV Tech? They have been selling the court released cells from the meltdown of EVComponents. Your cell information sounds a lot like my information. The cells are labeled TS-LFP(...) but the paperwork indicates they are LiFeYPO4 cells. I think my cells where from the last batch of cells that EVC delivered to customers, mine have a manufacture date of Feb 2010 and I received them in March 2010. Actually, much of my batch may not have been shipped -- mine where since I was local and could show up on his doorstep. My cells are pretty tough, I've pulled up to 450 amps from them -- that is 7.5C from my 60 amp hour cells. 

To do a split with an odd number of cells you need to use slightly unequal resistances. If one "half" is 22 cells and the other 23 cells then you need to make the resistance is the side with 23 cells 4.5% higher to create a "virtual center."


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## GizmoEV (Nov 28, 2009)

Dougnutz said:


> I’m like the idea of splitting the pack in two and comparing the two halves but I ended up with 45 cells after all so that won’t quite work. Suggestions?


If you build a circuit like I did for my Gizmo you could just replace the potentiometer in the middle with a larger range one and it could then compensate for the voltage difference between the two "halves." If you use 100kohm resisters on each half you could use a 10kohm pot and adjust out the difference.


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## DIYguy (Sep 18, 2008)

I just read this thread. Really nice example of helping a guy get it right. I have a very similar vehicle with more battery. One comment I would have is, regarding your choice for balancing. I'm not stuck on top or bottom balancing per se when not running a BMS however, I think that there is a little more risk in choosing a top balance when you have a smaller pack and the chances of running it low, are higher. 
The other thing that stuck out was the comments about lead vs lithium and the duration in years for life cycle. I had two lead packs in my truck before the lithium and one important point is that when you have lead, you don't rack up the miles. I put approximately 5 times more miles per year (or season) using the lithium than the lead. Since the range is that much more, I can use it like a regular vehicle.

Good stuff.


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## Guest (Nov 5, 2011)

> I put approximately 5 times more miles per year (or season) using the lithium than the lead. Since the range is that much more, I can use it like a regular vehicle.


And this is the reason Lithium has made Electric Cars Viable. With lead your limited to more or less around town toys. Since June I have racked up just under 5500 miles on my Leaf. Miles are racking up fast. Use it daily. Sweet daily driver. 

Pete


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## Dougnutz (Aug 22, 2011)

GizmoEV said:


> If you build a circuit like I did for my Gizmo you could just replace the potentiometer in the middle with a larger range one and it could then compensate for the voltage difference between the two "halves." If you use 100kohm resisters on each half you could use a 10kohm pot and adjust out the difference.


I think this is the best direction for me for now. I just assumed that the "center" would drift as the pack changed but the more I thought about it I realized the capacity is "used" evenly from the cells. Well at least we hope it is. So the offset center should work. Right?




DIYguy said:


> I just read this thread. Really nice example of helping a guy get it right. I have a very similar vehicle with more battery. One comment I would have is, regarding your choice for balancing. I'm not stuck on top or bottom balancing per se when not running a BMS however, I think that there is a little more risk in choosing a top balance when you have a smaller pack and the chances of running it low, are higher.





DIYguy said:


> The other thing that stuck out was the comments about lead vs lithium and the duration in years for life cycle. I had two lead packs in my truck before the lithium and one important point is that when you have lead, you don't rack up the miles. I put approximately 5 times more miles per year (or season) using the lithium than the lead. Since the range is that much more, I can use it like a regular vehicle.
> Good stuff.


Ya, there was a lot of great feedback. I really feel like I made the best decision for the long run. I do agree that without a BMS the arguments for bottom balancing are compelling. But I my case the truck is really just a weekend vehicle that makes short trips, I commute by bicycle. I may change my mind later but for now it’s much simpler for me to maintain the pack if I do top balancing. Though I am not sure about a 23 KwHr (144x160) being a small pack. 




gottdi said:


> And this is the reason Lithium has made Electric Cars Viable. With lead your limited to more or less around town toys. Since June I have racked up just under 5500 miles on my Leaf. Miles are racking up fast. Use it daily. Sweet daily driver.


I do find myself making a lot of excuses to drive the truck. But all the trips remain pretty short.


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## GizmoEV (Nov 28, 2009)

Dougnutz said:


> I think this is the best direction for me for now. I just assumed that the "center" would drift as the pack changed but the more I thought about it I realized the capacity is "used" evenly from the cells. Well at least we hope it is. So the offset center should work. Right?


Right. Since the resistances on each side of the circuit will be proportional to their respective sides, the voltage drop across each side will also be proportional so that if the sides change voltage proportionally the voltage reading of the balance gauge will stay the same.

If you use 100kohm resistors and a 10kohm pot the total current through the device when the cells are at 3.4V will only be 0.73mA or 0.11W. Remember to put the resistors at the battery terminal if you aren't going to use fuses. You could do what I did or you could put the fuse inside a ring terminal to go under the bolt. You will want to come up with some sort of strain relief so the stiff fuse wire doesn't break where you attach things.


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## Dougnutz (Aug 22, 2011)

GizmoEV said:


> Right. Since the resistances on each side of the circuit will be proportional to their respective sides, the voltage drop across each side will also be proportional so that if the sides change voltage proportionally the voltage reading of the balance gauge will stay the same. A light will also be easier to explain to my Wife... Red means stop.
> 
> If you use 100kohm resistors and a 10kohm pot the total current through the device when the cells are at 3.4V will only be 0.73mA or 0.11W. Remember to put the resistors at the battery terminal if you aren't going to use fuses. You could do what I did or you could put the fuse inside a ring terminal to go under the bolt. You will want to come up with some sort of strain relief so the stiff fuse wire doesn't break where you attach things.


Thanks for the numbers Gizmo. I'm noodling out what I want to do. My short term goal is an warning that something went wrong. So I'm leaning toward the light style warning. I'm not sure if I want to buy a pack of resistors or a pot. I'm leaning toward the pot since I can just make it up once and dial it in. 

My long term goal is a little different. I plan to build a small touch screen interface that will take over the duties of the CA and provide some logic to predect distance to empty, SOC etc. I'm planning to use the .Net gadgeteer (or similar) as a base, because my strengths are in programming not circuits  Eventually I hope to switch the curtis out for a Sol 1 and tap the data stream for more info to display.


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## GizmoEV (Nov 28, 2009)

A pack of resistors to zero the meter will be a pain. A 15 turn 10k pot will be simplest and if you ever do go with an even number of cells it is a simple matter of adjusting it. I just bought resistors and a pot from RadioShack. Even though the resistors are only 5% the pot took care of any differences in them.

As you build your display setup you could just build an input for the pack balance. Just display double the voltage reading and you will have the effective voltage difference between the sides. In my case it is the actual voltage difference since each half is the same size.

FWIW, the most I've seen is 0.14V difference. It is usually -0.01V or so right after charge and then 0.00 after a little is taken from the pack. Only under load do I see a greater difference. That could be due to the difference resistance in the connecting straps or battery differences. I just don't know.


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