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Old 24-01-2014, 16:22   #3496
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LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Higher capacity cells discharged at lower fractional C rates will exhibit a lower V/I approaching almost zero slope. Equally at high C the slope is more pronounced

What that effects is that in high C capacity , low fractional C discharge you will get a constant or near constant discharge voltage and then the lower knee voltage will appear quite fast.

Be very careful about assigning SOC % to voltage points in the flat part of the curve. It's very misleading. What you are seeing isnt Peukerts effect , more that you are most likely running closer to a greater discharge range then 20%. . To check this don't just count the amps discharged , count the amps need to recharge to the designated upper set point. Charge at the same rate as discharge and amp count

Anyway peukert was invented to model lead acid battery's and doesn't really apply to Li.

Dave
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Old 24-01-2014, 16:43   #3497
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I answered my own question. After a 80% DOD cycle, the loaded voltage was 12.77 volts, unloaded 12.88 volts (same as during the capacity test) but after 30 minutes of rest was at 13.01 volts, confirming that the cells rebound a bit with rest. I'll wait another 30 minutes and see what it rebounds to. The 2nd 30 minute rest only netted +0.02 to 13.03 volts.
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Old 24-01-2014, 18:18   #3498
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi Bob,
Your figures are close to mine under load, my loads are 0.5C for capacity testing so I can attempt to mirror the factory testing so my stop voltage is 2.8v. The discharge this time will be to 100% of advertised capacity or 2.8v under load, which ever occurs first. The have copped a terrible beating in both deep discharges and well over voltage recharges over the last 6 mths purely due to my lack of supervision and maintenance of the control equipment. The 2 cables on the solid state relays came in contact with each other, this escaped my attention, the control gear could no longer turn the charging or discharging off resulting in less than optimal voltage regulation. I expect the internal resistance has increased so the voltage drop under a 0.5C load will be much greater this time.
The voltage under load is the important one, rested voltage is a bit meaningless, much like rested voltage in lead acid batteries after a load, it only tells you that the discharge was too deep if the recovery voltage was less than 3v per cell.
the voltage drop under load is a product of how easily the lithium ions can move from one electrode to the other, heavy coatings on either electrode slows the ion flow allowing the voltage to sag, but once the load is removed the ions can flow back into the electrode and restore equilibrium. If the loaded discharge voltage is allowed to drop below 2.8v the coating will increase in density as the electrolyte heats up and eventually serious damage will result.
I now have 32 cells that look like they are candidates for a pregnancy test, but they are still functioning, if the capacity loss is excessive I'll try compressing the cell cases and see if the capacity return or if they have suffered irrepairable damage.

T1 Terry
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Old 27-01-2014, 10:32   #3499
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi guys!
My name is Damir and I come from the Croatian coast.
I have a small boat about 19 feet long. Three years ago I installed a trolling motor. The system is 48 V, 4 x 100 Ah AGM. The charger 25 A, 12 V and I also have 2 x 90 W solar panels (just 20 Ah at sunny days).
I also have wattmetar with ammeter and voltmeter. Everything works great except my AGM batteries.
Average consumption in Trolling is 3-5 A (150-250 W). Maximum consumption at full throttle is 10-12 A (500-600 W).
Average consumption in the fishing day is 10 - 20 Ah.
Now I decided to replace my AGM batteries with LiFePO4.
I want to buy a 16 x 60 x 16 Ah or 90 Ah cells WINSTON which I want to charge with GENASUN solar charger for LiFePO4 (This is the only charger that rising voltage with my 42 Voc to 50 + V.
Now I need your help:
1. Is 16 cells too many cells to work without BMS (small current: 3-5 A, a lot of the capacity of 60 Ah or 90 Ah, low power consumption (about 20 Ah per day)
2. I would like to avoid BMS, mains charger and charge them only with a solar charger.
3. What do you recommend voltage per cell? 3.4 V or something bigger? Will it work?
4. Whether I buy a mains charger 58.4 V, 10 A, which I used in combination with ordinary network timer (2 hours maximum) when the battery is low during cloudy days and in combination with Cellog alarm port with the relay?
Greetings from Croatian,
Damir
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Old 28-01-2014, 10:02   #3500
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hello All,

I have some questions for the users of LiFePo4 as house banks in cruising sailboats or just users in general. The time has come to replace my 4xgrp24 FLA house bank of 320Ah and upgrade it to at least 400Ah, LiFePo4 might just be the answer. Now for the questions.

How has the reliability been on the Winston cells? Has anybody had any failures and if so what was the cause and failure mode? Are there other manufactures I should look at?

Once the cells are balanced and used as a house bank with <.2C load how often is re-balancing required? How long does it take to rebalance?

In a four cell 12V nominal bank is a full BMS required or is overcharge/discharge shutdown sufficient?

Can the cells be mounted in any orientation or do they need to stay upright? I have a height limitation of <9" (<228mm) and would like to stack two 400Ah cells on their sides for a total height of about 5.5" (133mm), two of these modules will make the house bank. Anybody see any problems with this?

Swelling of the case has been mentioned. Does anybody know why or under what conditions this occurs? Should this be a concern, should it be allowed for when mounting the cells?

Do the cells heat up when charging? Should the cell temp be monitored while charging?
The max charge current will be 100A from a Balmar alternator so even the charge current will be <.25C for the bank, what cell temp rise should I expect under these conditions?

Any recommendations for a vendor? I see Balqon mentioned and have seen their web site as well as Battery Space. Any other vendors I should look at?

Has anybody had any issues with their insurance? I know LiFeP04 chemistry is safe but an insurance company may just see "Lithium battery" in a survey and denie a claim or coverage. Any comments from surveyors?

I see Mastervolt is selling LiFePo4 batteries with built in BMS and typical Mastervolt complexity so I guess Li is becoming somewhat mainstream. Don't know the cost for the Mastervolt system but I'm sure it's $$$$ more than I'm planning to spend. Anybody using or know of these batteries?

Since I'm at the go/nogo LiF at this point I'll leave off the technical details such as cell monitoring, max/min cell voltages and charger settings, I'll ask about that later if the decision is a 'go'. I do have the technical ability to construct and modify whatever equipment is necessary for a successful installation as well as the ability to make dumb mistakes with the best of them.

Special thanks to all those who have done the 'science experiments', your results have been most helpful to get me to at least this point.

Steve
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Old 28-01-2014, 11:02   #3501
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi Steve,

I've been using 4x4x200a winston cells for 800a bank on my boat for three years now.

Have had no problems. I have not had to rebalance, I'm using 4 x 4s arrangement. I have a miniBMS BMS system which provides for shunting, cell monitoring and shutdown. I'm only charging to 14v so not much shunting takes place.

Manual says you can mount on side but I'd be worried about doing up connection bolts in that position.

I have mine installed fairly tight to prevent swelling, have had none, so not sure if they would have swelled otherwise.

Have not noticed temp rise when charging, I'm charging at max 0.25c.

Generally very happy with the batteries and would hate to go back to LA.

Doug

Quote:
Originally Posted by SteveSails View Post
Hello All,



I have some questions for the users of LiFePo4 as house banks in cruising sailboats or just users in general. The time has come to replace my 4xgrp24 FLA house bank of 320Ah and upgrade it to at least 400Ah, LiFePo4 might just be the answer. Now for the questions.



How has the reliability been on the Winston cells? Has anybody had any failures and if so what was the cause and failure mode? Are there other manufactures I should look at?



Once the cells are balanced and used as a house bank with <.2C load how often is re-balancing required? How long does it take to rebalance?



In a four cell 12V nominal bank is a full BMS required or is overcharge/discharge shutdown sufficient?



Can the cells be mounted in any orientation or do they need to stay upright? I have a height limitation of <9" (<228mm) and would like to stack two 400Ah cells on their sides for a total height of about 5.5" (133mm), two of these modules will make the house bank. Anybody see any problems with this?



Swelling of the case has been mentioned. Does anybody know why or under what conditions this occurs? Should this be a concern, should it be allowed for when mounting the cells?



Do the cells heat up when charging? Should the cell temp be monitored while charging?

The max charge current will be 100A from a Balmar alternator so even the charge current will be <.25C for the bank, what cell temp rise should I expect under these conditions?



Any recommendations for a vendor? I see Balqon mentioned and have seen their web site as well as Battery Space. Any other vendors I should look at?



Has anybody had any issues with their insurance? I know LiFeP04 chemistry is safe but an insurance company may just see "Lithium battery" in a survey and denie a claim or coverage. Any comments from surveyors?



I see Mastervolt is selling LiFePo4 batteries with built in BMS and typical Mastervolt complexity so I guess Li is becoming somewhat mainstream. Don't know the cost for the Mastervolt system but I'm sure it's $$$$ more than I'm planning to spend. Anybody using or know of these batteries?



Since I'm at the go/nogo LiF at this point I'll leave off the technical details such as cell monitoring, max/min cell voltages and charger settings, I'll ask about that later if the decision is a 'go'. I do have the technical ability to construct and modify whatever equipment is necessary for a successful installation as well as the ability to make dumb mistakes with the best of them.



Special thanks to all those who have done the 'science experiments', your results have been most helpful to get me to at least this point.



Steve
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Old 28-01-2014, 11:07   #3502
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by SteveSails View Post
Hello All,

I have some questions for the users of LiFePo4 as house banks in cruising sailboats or just users in general. The time has come to replace my 4xgrp24 FLA house bank of 320Ah and upgrade it to at least 400Ah, LiFePo4 might just be the answer. Now for the questions.

How has the reliability been on the Winston cells? Has anybody had any failures and if so what was the cause and failure mode? Are there other manufactures I should look at?

I have 215 cycles to 80% DOD, no problems.
CALB is another cell choice.


Once the cells are balanced and used as a house bank with <.2C load how often is re-balancing required? How long does it take to rebalance?

I'm using a 0.41 C load on those above mentioned 215 cycles, voltages still tight. Balance time depends on output of PS feeding all your cells in parallel.

In a four cell 12V nominal bank is a full BMS required or is overcharge/discharge shutdown sufficient?

I'm not using a BMS but UV and LV shutdown is recommended to save the cells from an accidental over voltage while charging or too low a cell voltage while discharging.

Can the cells be mounted in any orientation or do they need to stay upright? I have a height limitation of <9" (<228mm) and would like to stack two 400Ah cells on their sides for a total height of about 5.5" (133mm), two of these modules will make the house bank. Anybody see any problems with this?

Shouldn't be a problem.

Swelling of the case has been mentioned. Does anybody know why or under what conditions this occurs? Should this be a concern, should it be allowed for when mounting the cells?

At low C rates (less than 1.0 C) I haven't seen bulging, but my cells are banded.

Do the cells heat up when charging? Should the cell temp be monitored while charging?

I charge at 0.5C and never see heat above 100 F.

The max charge current will be 100A from a Balmar alternator so even the charge current will be <.25C for the bank, what cell temp rise should I expect under these conditions?

Not much.

Any recommendations for a vendor? I see Balqon mentioned and have seen their web site as well as Battery Space. Any other vendors I should look at?

Has anybody had any issues with their insurance? I know LiFeP04 chemistry is safe but an insurance company may just see "Lithium battery" in a survey and denie a claim or coverage. Any comments from surveyors?

I see Mastervolt is selling LiFePo4 batteries with built in BMS and typical Mastervolt complexity so I guess Li is becoming somewhat mainstream. Don't know the cost for the Mastervolt system but I'm sure it's $$$$ more than I'm planning to spend. Anybody using or know of these batteries?

Since I'm at the go/nogo LiF at this point I'll leave off the technical details such as cell monitoring, max/min cell voltages and charger settings, I'll ask about that later if the decision is a 'go'. I do have the technical ability to construct and modify whatever equipment is necessary for a successful installation as well as the ability to make dumb mistakes with the best of them.

Special thanks to all those who have done the 'science experiments', your results have been most helpful to get me to at least this point.

Steve
Steve,

Due to conservative a-hr ratings, nil Peukert, and being able to cycle to 80% DOD, you will discover that what ever a-hr rating worked fine for you in a lead bank, 1/2 that rating will give the same usable a-hr in LiFePO4. So if you were going to upgrade your lead bank to 400 a-hr, 200 a-hr LiFePO4 would be the same upgrade over your current 320 a-hr bank
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Old 28-01-2014, 11:34   #3503
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Steve,

Quote:
Originally Posted by SteveSails View Post

How has the reliability been on the Winston cells? Has anybody had any failures and if so what was the cause and failure mode? Are there other manufactures I should look at?
No issues that I am aware of, other than the owners of the cells.... I don't think Winston cells are quite as well matched as CALB but they still work fine in a house bank system.

Quote:
Originally Posted by SteveSails View Post
Once the cells are balanced and used as a house bank with <.2C load how often is re-balancing required? How long does it take to rebalance?
I have now exceeded 230 cycles, most to 80% DOD and the cells are still in near perfect balance out to the thousandths of a volt or well beyond where you can measure on most boats. HOWEVER, I am using my bank in the middle range of 20% SOC to about 98% SOC.. Our pack is never charged above 14.0V and never discharged below 20% SOC.. Our BMS is there simply as an insurance policy and our charge sources are dialed in to parameters that keep the cells in the "safe" range.

I am somewhat convinced that the need for continual cell balancing is partially caused by regularly pushing into either the upper or lower knees as many EV guys do. As more and more off grid use becomes more popular I think we will see this cell balance issue as a once yearly or bi-yearly, if that, event.

Re-balancing is as easy as charging the pack in series until the highest cell hits 3.800V. Then wiring the pack in parallel, letting it sit for a day or two and then charging the parallel pack to 3.800V again.

Quote:
Originally Posted by SteveSails View Post
In a four cell 12V nominal bank is a full BMS required or is overcharge/discharge shutdown sufficient?
It does not hurt to have one and will likely be required by the safety standards for Li when they are done.. I would say it is more important to have a system that can monitor individual cell voltages and do HVC or LVC based on cell voltages not just on pack voltages. The Clean Power Auto House Power BMS system is about $100.00 and is very cheap insurance.

I would also suggest that re-wiring the boat to have both a charge bus and loads bus is also a very wise way to lay out the system. One relay for everything is a poor design choice IMHO.. My systems use individual HVC relays for solar, shore charging, and alternator. It also uses a Tyco EV200 contactor for LVC on the loads bus. If my bank cuts on LVC I can still charge or vise-verse..

Quote:
Originally Posted by SteveSails View Post
Can the cells be mounted in any orientation or do they need to stay upright? I have a height limitation of <9" (<228mm) and would like to stack two 400Ah cells on their sides for a total height of about 5.5" (133mm), two of these modules will make the house bank. Anybody see any problems with this?
Winston Cell Orientation (LINK)

Quote:
Originally Posted by SteveSails View Post
Swelling of the case has been mentioned. Does anybody know why or under what conditions this occurs? Should this be a concern, should it be allowed for when mounting the cells?
The cells should be well strapped together but swelling is a non-issue if the cell are kept withing charge voltage range and not over charged or abused.

A couple of guys on here have bulged cells by not being careful or by not using a BMS that could have protected against their own HEF/human error factor. This all comes back to my first sentence about the "owners" of the cells being the biggest liability.

Quote:
Originally Posted by SteveSails View Post
Do the cells heat up when charging?
At sailboat charge / discharge rates I have not been able to discern or measure any changes in cell temp beyond perhaps 0.5F to 1F and even that is within the margin of error for my pyrometer. Suffice it so say you should see no measurable temp changes in typical sailboat house bank use. We charge a 400Ah pack at 120A - 130A (0.3 "C" to 0.325 "C") and see no measurable cell level temp changes.

Quote:
Originally Posted by SteveSails View Post
Should the cell temp be monitored while charging?
Monitoring temp would not hurt anything UNLESS this monitoring also compensates/adjusts charging voltage. LiFePO4 should not be connected to temp compensated charge sources.


Quote:
Originally Posted by SteveSails View Post
The max charge current will be 100A from a Balmar alternator so even the charge current will be <.25C for the bank, what cell temp rise should I expect under these conditions?
Unless your Balmar is a 150A alt you are not going to see 100A of charging. You would be wise to set that alt at Belt Manager/Amp Manager level 3 or 4 or it will simply run too hot and have a very, very short life. LiFePO4 eats alternators for lunch that are not temp compensated or set up properly.

Quote:
Originally Posted by SteveSails View Post
Any recommendations for a vendor? I see Balqon mentioned and have seen their web site as well as Battery Space. Any other vendors I should look at?
I would not use Balquon again even if you paid me. The company is run like it is in your friends back yard Tree Fort. This is an unorganized, poor communication, lack of stock organization that I can not personally recommend any longer..

I am now using only CALB cells either the SE (blue case) or the new CA series (gray case). These cells are in-stock from a number of US distributors. The new CA cells are pretty amazing and run about $499.00 for a 400Ah cell. Genasun uses the CALB SE series and choose CALB due to consistency in the product.

Quote:
Originally Posted by SteveSails View Post
Has anybody had any issues with their insurance? I know LiFeP04 chemistry is safe but an insurance company may just see "Lithium battery" in a survey and denie a claim or coverage. Any comments from surveyors?
Unless your policy has specific exclusions for LiFePO4, which none do, then you won't have any issues. I called my company to check, AMICA, and they had no qualms with it what so ever.

Quote:
Originally Posted by SteveSails View Post
I see Mastervolt is selling LiFePo4 batteries with built in BMS and typical Mastervolt complexity so I guess Li is becoming somewhat mainstream. Don't know the cost for the Mastervolt system but I'm sure it's $$$$ more than I'm planning to spend. Anybody using or know of these batteries?
Li in any format, wheter from Genasun, Mastervolt or a well executed self build, is going to be more complex than any lead acid bank any way you slice it up.

Quote:
Originally Posted by SteveSails View Post
Since I'm at the go/nogo LiF at this point I'll leave off the technical details such as cell monitoring, max/min cell voltages and charger settings, I'll ask about that later if the decision is a 'go'. I do have the technical ability to construct and modify whatever equipment is necessary for a successful installation as well as the ability to make dumb mistakes with the best of them.
The technology is amazing but unless you have a good grasp of electrical systems in general then this may not be for everyone and could result in a big fat hole in your wallet if not done well....
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Old 28-01-2014, 13:54   #3504
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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I would also suggest that re-wiring the boat to have both a charge bus and loads bus is also a very wise way to lay out the system.
What is the normal way that a bank SOC meter is set up if you have two seperate busses for charging and discharging ? Do the two busses get combined just prior to the shunt and then go as one to the battery ?
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Old 28-01-2014, 14:16   #3505
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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What is the normal way that a bank SOC meter is set up if you have two seperate busses for charging and discharging ? Do the two busses get combined just prior to the shunt and then go as one to the battery ?
The shunt is on the neg side.... All negatives are still in the same place, the neg loads bus. Shunt gets placed between house neg and neg loads.

The busses are simply isolated so that a low voltage event does not simply break the entire bank away leaving you with no way to charge or use loads..

In an HVE you want to be able to use the loads but discontinue charging.

In an LVE you want to break away the system loads but be able to charge.


The dual bus provides this flexibility.. Some system designs simply break a single relay which stops any charging or discharging and 100% isolates the bank. A dual bus breaks charging on HV and breaks loads on LV....
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Old 28-01-2014, 15:08   #3506
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Maine Sail

Glade you posted the info on cell orientation. I had never heard this before.

"There is only a small amount of electrolyte in each cell. The plates "wick" the electrolyte so they need to have their "feet in the water" so to speak. Imagine the plates having a sponge cover. When they sit in electrolyte they can soak up more. If they don't have contact with the electrolyte pool they will dry out and become ineffective. So when the cell is flat the top plates can suffer from electrolyte starvation.

http://visforvoltage.org/forum/9972-...ll-orientation
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Old 28-01-2014, 15:24   #3507
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Maine Sail

Glade you posted the info on cell orientation. I had never heard this before.

"There is only a small amount of electrolyte in each cell. The plates "wick" the electrolyte so they need to have their "feet in the water" so to speak. Imagine the plates having a sponge cover. When they sit in electrolyte they can soak up more. If they don't have contact with the electrolyte pool they will dry out and become ineffective. So when the cell is flat the top plates can suffer from electrolyte starvation.

http://visforvoltage.org/forum/9972-...ll-orientation
I had not really seen that explanation but the top picture is what Thundersky used to show in their manual...
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Old 28-01-2014, 15:25   #3508
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Thanks Maine Sail, all good info.
I see now where lying cells flat could starve the upper plates of electrolyte, mounting on edge limits me to 180Ah cells to maintain a height of <9", maybe I'll go with 8 cells for at least a 300Ah system.
I like the newer CALB cells if for no other reason the manufacturer has molded their name 'CALB' into the case, makes me wonder when a manufacturer doesn't want their name on a product. They do cost more but might be worth it. I see that Sinopoly which makes Thundersky and maybe Winston? is in deep financial trouble, don't want to get involved in that and apparently not with Balqon either.
I agree that a single disconnect relay is a bad idea and I intend to use separate shutdowns on each charge source, AC charger, solar and alternator. As for the alternator you are right that 100A from a 110A rated alternator is not reality, even 80A will require additional cooling. With the Balmar 624 regulator I can monitor alternator temp and dial back as necessary.
When I rewired a couple of years ago I made up a high load breaker panel with breakers for main panel feed, windlass, SSB radio, and autopilot. It will not be too difficult to add a LV shutoff to the feed for this panel which will disconnect all the loads. The way the charge sources are wired I'm pretty close to a dual bus system already so there should be no big problems there.
I'm still at the sketch 'back of napkin' design stage and everything I said is off the top of my head so room for lots of error but this is the fun part. Next is the real work, define the system performance specs, dig into component spec sheets, pick the components and measure and remeasure to make sure everything will fit. Reminds me of being back at work.

Steve
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Old 28-01-2014, 16:01   #3509
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Thanks Maine Sail, all good info.
I see now where lying cells flat could starve the upper plates of electrolyte, mounting on edge limits me to 180Ah cells to maintain a height of <9", maybe I'll go with 8 cells for at least a 300Ah system.
I like the newer CALB cells if for no other reason the manufacturer has molded their name 'CALB' into the case, makes me wonder when a manufacturer doesn't want their name on a product. They do cost more but might be worth it. I see that Sinopoly which makes Thundersky and maybe Winston? is in deep financial trouble, don't want to get involved in that and apparently not with Balqon either.
I agree that a single disconnect relay is a bad idea and I intend to use separate shutdowns on each charge source, AC charger, solar and alternator. As for the alternator you are right that 100A from a 110A rated alternator is not reality, even 80A will require additional cooling. With the Balmar 624 regulator I can monitor alternator temp and dial back as necessary.
When I rewired a couple of years ago I made up a high load breaker panel with breakers for main panel feed, windlass, SSB radio, and autopilot. It will not be too difficult to add a LV shutoff to the feed for this panel which will disconnect all the loads. The way the charge sources are wired I'm pretty close to a dual bus system already so there should be no big problems there.
I'm still at the sketch 'back of napkin' design stage and everything I said is off the top of my head so room for lots of error but this is the fun part. Next is the real work, define the system performance specs, dig into component spec sheets, pick the components and measure and remeasure to make sure everything will fit. Reminds me of being back at work.

Steve
I know at least with the CALB SE series cells they only recommend vertical orientation... I don't yet have my hands on the manual for the new CA series cells.

I do tend to question the "reason" of why not to side mount them and can only take CALB at their word. No reasonable explanation, with any reasonable scientific detail, has ever been provided by CALB or Winston on this matter that I have been able to find..
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Old 28-01-2014, 16:12   #3510
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Steve,

My Winston 100 a-hr cells are 218 mm in height and with the terminal bolts, cables, and cell series connect bars are just barely under 9" in the upright position. I'm not a fan of series/parallel, but if dictated by available space, then this height would maximize your space. Just something to think about while it is still in the "back of napkin" design phase.

Here is a link on CALB cells and dimensions.

http://www.electriccarpartscompany.c...matic_c_1.html
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