# AGM Battery Issue, 3 of 12 died



## ARti (Oct 27, 2008)

Hi. I'm looking for recommendations on how to resolve some battery problems.

Three of my 12 Odyssey PC2150s AGM batteries (Group 31, [email protected]) have gone bad. I'm considering alternatives, and need some input. Please see below for the five paths I'm considering.

Problem: Decreased range. 
Typical Comfortable Range with no sponginess in acceleration: ~25miles, estimated to be 70% DoD.
Last Observed Range: ~12miles
Final Straw: Elcon PFC-1500 Battery Charger errored out, would not charge string

Background:
Project: 1997 BMW 318ti hatchback (see BMW 318ti Conversion to "EMW")
Components Ordered from EVA: January 2009
Project initiated and completed myself, with mechanical help from local buddies with a fab shop and Tool/Die experience. They also built the adapter from the motor shaft to the flywheel (yes, I decided to keep the clutch). The first electric drive was in April of 2010. I have around 2500 electric miles on it. 

When the Elcon errored out, I removed the batteries and started charging them with an Odyssey brand, AGM specific charger. Nine of the batteries came out fine, but three kept tripping. One hisses, and two of the three generate that nasty "bad battery" smell if you leave them on the charger. They're gone.

Alternatives:


Buy three new Odyssey PC2150s batteries to replace the dead ones, and keep going. They're out of warranty, so the full $350 each will be out of pocket. This is the simplest choice, but I wanted to get input from you guys on potential issues with putting new batteries in a string of aged batteries. *Any thoughts? * This approach would be good if I want to keep going, business as usual, but may lead to a succession of $350 purchases at unknown intervals. When would I know when to call it quits and replace all of them?
Buy three Exide or other brand AGMs that are also Group31, around 100AH and put them in the string. I've found other brands that are available for around $200 each. This is financially appealing, and wouldn't require a lot of rework, but I wanted to get input from you guys on potential issues with mixing battery types AND putting new batteries in a string of aged batteries. *Any thoughts?* I'm also a smidge concerned because these cheaper brands are lighter, indicating that they wouldn't perform as well as the Odys. This would be a stop-gap approach that would keep me rolling while I explore lithium and save money.
Buy one Odyssey PC2150s AGM and drop the system voltage down to 120 to see if the performance is tolerable. But here's the question; how hard is it to reprogram the Elcon charger to aim for ten AGMs, instead of 12? *Any Thoughts? *This approach is also economical ($350), and the slower performance may be just fine for my typical use cases (5-10 mile going to lunch or dropping kids at school, then returning home).
Start Saving for Lithium and park the car until I've got enough. Sell off the Odys to boaters for trolling motors, and mothball the BMW until some day when I've got enough to move to Lithium, or whatever's next. How do I estimate the cost of a move to Lithium?
Sell the components here on DIY, scrap the BMW, call this $15000 an interesting phase of my life, and start shopping for a used Chevy Volt. This approach feels a little defeatist, and is unappealing, but may be the most responsible thing to do.
Suggestions Welcome,
Phillip


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## Sunking (Aug 10, 2009)

NO, do not buy 3 more batteries. You made a huge error. The battery you bought is a SLI battery (Starting, Lighting, Ignition aka Starting battery). They are designed for cranking engines with short burst of high current and then quickly recharged. If you press them into Cycle Service will not last and do exactly what you describe. 

If you are going to use Lead Acid use a Hybrid Battery which is a cross between an SLI battery and a True Deep Cycle battery. Additionally never discharge a lead acid battery more than 50% DOD.


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## Ziggythewiz (May 16, 2010)

Do you have anything to keep the AGMs balanced? If not they'd likely keep dying, and at an accelerated rate if you added new or different cells.

How many cycles do you have on them?

Have you looked into options for getting the elcon reprogrammed? Alternatively, is it okay with you interrupting the charge? You could just add a programmable relay to kill the charge when it gets to the desired target.

What's your current battery budget?

I couldn't afford to make the leap to full lithium all at once, so I made a lithium booster pack (40ah) that's half of what I want and I run it in parallel with my lead. This year or next I'll double the lithium and ditch the lead. I don't know if that would work alongside your AGMs or not; alternatively, for your short range, you could just do a small lithium pack ($2kish) and add to it when you can.


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## major (Apr 4, 2008)

Sunking said:


> NO, do not buy 3 more batteries. You made a huge error. The battery you bought is a SLI battery (Starting, Lighting, Ignition aka Starting battery). They are designed for cranking engines with short burst of high current and then quickly recharged. If you press them into Cycle Service will not last and do exactly what you describe.


The Odyssey PC2150s AGM batteries are deep cycle rated. http://www.odysseybatteries.com/battery/pc2150.htm They are rated at 400 cycles to 80% DOD. He had 3 die at about 100 cycles using 70% DOD claimed. Could be battery quality ---like that ever happens  Or maybe a crappy charger. Or maybe the lack of a regulator (BMS) system.  I don't know. 

ARti,

If those batteries were giving you satisfactory performance before the 3 crapped out, I'd consider replacing the 3. If it were me, I'd test the others for capacity and internal resistance. If they are near the original spec they should have another 300 cycles in them.

Of course Lithium would be sweet, but you have to decide regarding the cost. If you stick with lead acid, check out the charger and consider regulators or a monitor system. The Odyssey battery is a top brand battery. But all batteries fail sooner or later.


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## ARti (Oct 27, 2008)

Thanks for the quick feedback. I don't have a pack equalizing BMS, but I do have Volt Blochers for the Odys. I can think of around 10-15 mornings I went out and more than half were actively shunting while the charger soldiered on.

As Major guesstimated, I've got probably 100-150 cycles; the bulk of them 50% DoD or less. I work out of the house and typically plug back in right after running an errand. I will concede that I've probably spoiled the pack by charging at 110V instead of 220. The guys at EVAmerica gave me a hard time about that. I finally finished my 220 connection this fall, so the next round should be treated a little better.

I haven't given much thought to blending in lithium gradually. I suppose with a little effort I could get the Elcon reprogrammed to 108V (9x12) and have a switch between the 108V AGM pack and a 36V Li pack; charge with them separated and run with them sequenced? I'd probably have to learn how to re-parameterize the charger myself if I were going to take that approach as each AGM dies.

Something to think about.

Does anybody have any grave concerns about blending in three 12V AGMs of a cheaper grade than the Odys? 

Thanks,
Phillip


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## Ziggythewiz (May 16, 2010)

You wouldn't want to add lithium in series, only parallel if you choose that route.

With the blochers I think you'd be okay adding in some cheaper batts, but you should check to see if your charger is putting out more than the blochers can manage, especially if they're running overnight that way.


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## EVfun (Mar 14, 2010)

Replacing individual batteries in an AGM pack is not recommended. You will need battery regulators and they should be able to shunt at least a few amps. The new cells will have a higher charge efficiency and will get full first. If they cannot be bypassed with a shunt reg they will cook. Without knowing the condition of all the batteries I cannot guess at how much range you will get back by replacing the 3 that are toast.


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## piotrsko (Dec 9, 2007)

IMHO: you also might want to do something with the Elcon. Some of us think that the "equalization" portion is a bit stiff. Trojan recommends 240 V max for my string and the Elcon I use turns into maintenance mode at 252. By any chance the bad batteries are at the neg end of the string?


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## ARti (Oct 27, 2008)

piotrsko said:


> By any chance the bad batteries are at the neg end of the string?


In fact, they were...#1, 2, and 3.


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## Sunking (Aug 10, 2009)

major said:


> The Odyssey PC2150s AGM batteries are deep cycle rated. http://www.odysseybatteries.com/battery/pc2150.htm They are rated at 400 cycles to 80% DOD. He had 3 die at about 100 cycles using 70% DOD claimed. Could be battery quality ---like that ever happens  Or maybe a crappy charger. Or maybe the lack of a regulator (BMS) system.  I don't know.


 Major the battery has a CCA rating which is a dead giveaway it is a SLI battery. Deep Cycle batteries are rated in Amp Hours, not CCA. This battery has no AH spec.


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## Sunking (Aug 10, 2009)

ARti said:


> As Major guesstimated, I've got probably 100-150 cycles; the bulk of them 50% DoD or less.


That is the problem with using an SLI battery for cycle application, they do not last. A good quality Deep Cycle AGM like say a Concorde PVX series (Appendix C page 40) should yield over 1000 cycles to 50% DOD.


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## major (Apr 4, 2008)

Sunking said:


> Major the battery has a CCA rating which is a dead giveaway it is a SLI battery. Deep Cycle batteries are rated in Amp Hours, not CCA. This battery has no AH spec.


Sun,

I realize that this battery is not considered a "true" deep cycle product by your industry. However in the world of batteries used on vehicles, it is labeled that way. http://www.batterymart.com/pdf_files/odyssey_guide.pdf See page #6. The C/20 rating is 100 Ah. 

It is a good battery, not perfect, but one of the best for the intended purpose. I've used Odyssey, Genesis, and Hawkers. Most perform very well for Pb-Acid on vehicles. A few samples suck, but most do well.

major


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## major (Apr 4, 2008)

Sunking said:


> That is the problem with using an SLI battery for cycle application, they do not last. A good quality Deep Cycle AGM like say a Concorde PVX series (Appendix C page 40) should yield over 1000 cycles to 50% DOD.


Some types of deep cycle batteries do not do well for EVs because they lack power. I do not see the internal resistance or short circuit current listed for the 100 Ah model on your linked spec sheet. The Odyssey has very low resistance and is quite powerful.


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## Sunking (Aug 10, 2009)

major said:


> The Odyssey has very low resistance and is quite powerful.


I understand as all SLI batteries have extremely low resistance to have high CCA ratings. To do that they have to have multiple thin spongy plates to increase surface area to get the low resistance. Problem is thin spongy plates do not last long. 

An EV needs a hybrid battery which is a cross between a SLI and True Deep Cycle battery. 

However here is what you want to know. Check the BCI 31 group. Translating CCA to Internal Resistance give them a CCA rating of roughly 2200 amps. Beats the heck out of the Odyssey battery and with over 1000 cycles @ 50% is a superior battery.


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## major (Apr 4, 2008)

Sunking said:


> An EV needs a hybrid battery which is a cross between a SLI and True Deep Cycle battery.


That is what the Odyssey is. 



> Some batteries provide enormous cranking
> power. Others, deep cycle reserve power.
> The revolutionary ODYSSEY® battery is
> designed to do both.


From the link I gave above.


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## Sunking (Aug 10, 2009)

major said:


> That is what the Odyssey is.
> 
> From the link I gave above.


Major I am saying is there are much better AGM batteries to do the same job.  You know as well as I do there are trade offs with respect internal resistance, DOD, cycle life, and high discharge/charge current. IMHO the Odyssey is neither good value or great performer. Sure they are inexpensive, but that does not make them the most economical choice. You can pay $100/Kwh for a 200 cycle battery, or you can pay $200/Kwh for a 1000+ cycle battery,. It is no contest IMO. 

On the Horizon is the PbC AGM battery made by Deka and Axiom which may put all battery chemistry to shame.


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## tomofreno (Mar 3, 2009)

ARti said:


> Thanks for the quick feedback. I don't have a pack equalizing BMS, but I do have Volt Blochers for the Odys. I can think of around 10-15 mornings I went out and more than half were actively shunting while the charger soldiered on...


 Did you check the voltage on your batteries near end of charge to see if they were all being fully charged? There was an issue with some of the Volt Blochers having leakage current and draining cells down. This is an example of one good VB (the one flat along the horizontal axis until turn on of the shunt, and others with leakage:
View attachment VB I versus V.pdf


The numbers in the legend are the voltages to which each of the cells was drained by these VB's when left without charging for a couple months. Vertical axis is Amps. (Edit:the data was taken by connecting a power supply, with current readout, across the VB leads and varying voltage over the range shown). If by chance the VB's on those 3 batteries have leakage like this you may have been discharging those 3 batteries down to a much lower SoC than you thought if you weren't checking voltages regularly.


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## major (Apr 4, 2008)

Sunking said:


> Major I am saying is there are much better AGM batteries to do the same job.  You know as well as I do there are trade offs with respect internal resistance, DOD, cycle life, and high discharge/charge current. IMHO the Odyssey is neither good value or great performer. Sure they are inexpensive, but that does not make them the most economical choice. You can pay $100/Kwh for a 200 cycle battery, or you can pay $200/Kwh for a 1000+ cycle battery,. It is no contest IMO.


I don't know why you are off topic like this. He has the Odyssey batteries in there so that's why I'm talking about them. Maybe there are better batteries. Maybe Odyssey is the best for his money. Odyssey looks better on paper than your candidate, and have seen widespread use in EVs over the years, and were the battery of choice for the top EV racers until Lithium showed up. Just drop it or start a "Best AGM" thread


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## BobD (Dec 26, 2012)

I wouldn't add 3 new, or even one new, AGM to the series. You'd probably just end up burning the new ones up quickly to match internal resistance in the old ones.

Did you really pay $350 each for those batteries? Personally, given the greatly increased cycle life in Deka's lead-acid gels, I don't see why anyone bothers with AGMs, unless you're in a climate that gets below -22F (gel will freeze), or you don't have a charger that can be programmed to limit voltage, or you want to absolutely maximize charge rate, weight/capacity ratio, and $$$/capacity ratio at the expense of everything else. I've been running 12 Deka Dominator gels in my Porsche 924 for 4 years now with no problems, charging with a cheap QuickCharge 10-amp charger (or a set of PV panels and an Outback Flex-max80 controller when at home) and QuickCharge shunt regulators.

I'm saving my money for lithium but I wouldn't add an accessory pack of them in parallel. I'll wait for some depletion in performance and trade the whole set up, since I'll need the right charger type and capacity, the right size BMS, and probably, all new racks and covers.


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## Sunking (Aug 10, 2009)

major said:


> I don't know why you are off topic like this.


It is not off topic and very relevant to the OP. He has 3 shot batteries and advised not to replace the 3 dead ones, but replace all of them. So if he replaces all of them, he is well advised to use a better battery.


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## major (Apr 4, 2008)

Sunking said:


> It is not off topic and very relevant to the OP. He has 3 shot batteries and advised not to replace the 3 dead ones, but replace all of them. So if he replaces all of them, he is well advised to use a better battery.


You can always advise to use a better battery. But you have been off base here from the start. You said:


Sunking said:


> NO, do not buy 3 more batteries. You made a huge error. The battery you bought is a SLI battery (Starting, Lighting, Ignition aka Starting battery). They are designed for cranking engines with short burst of high current and then quickly recharged. If you press them into Cycle Service will not last and do exactly what you describe.


 The Odyssey battery he is using is not SLI.

In fact, it is very much like the SunXtender battery you keep shoving in his face. The Odyssey is better by spec having 5000A vs 4000A short circuit current meaning 20% lower resistance and 20% higher efficiency with less internal generated heat. The SunXtender claims higher cycle life of 550 vs 400 at 80% DOD. Put all that together and it would be a choice based on price, warranty, availability and dealer relationship. The Odyssey has a good history in EV use; I have never seen or heard of the SunXtender used in any EV. I did not see the dimensions and weight for the SunXtender so do not know how it stacks up.

He has been using the Odyssey and 3 have failed. Not because he is using SLI batteries, but for some other reason. Personally I think he should consider replacing the 3 failed units with new ones if he can determine that the remainder are in good shape and determine the cause of the failure and correct the situation. Without identifying the cause, he could buy a new set of the batteries you recommend and end up exactly in the same place 100 cycles from now.

Batteries are always a crap shoot. You increase your odds using quality batteries, good engineering and a lot of testing. Close monitoring can help a lot.


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## ARti (Oct 27, 2008)

Thanks everybody for the input. Here's my plan; comments are more or less welcome:

While I'd love to upgrade to lithium, I don't have the budget for it right now.
While I'd feel more comfortable replacing all 12 of the batteries with something new, which would open the topic of which brand/type would be best, I don't have the budget for that right now either.

So, I'm going to find three new AGMs to replace the dead ones. Ideally they'd be the Ody PC2150 just to keep things the same, but we'll see what kind of wheeling and dealing I can do. I may wind up with a different brand, but will try to fight the urge to go Sam's Club Commercial "Energizer" AGM (mfg by JCI) and go middle of the road price wise.

Regarding balancing and overvoltage protection: 
I'm intrigued by piotrsko's correct guess that the dead batteries were the most negative in the string. I did check the sticker on the Elcon and somehow managed to find curve 212 described online. The voltage settings are correct for the 100Ah Odyssey. 

One of the issues I hadn't mentioned (not withholding, just forgot) is that of my 12 VoltBlochers, five appear to be dead. I don't know if they gave their life protecting the batteries or what. I was disappointed to note that of the three dead batteries, two VBs still seem to function. So I don't know what that means for the other four batteries with dead VBs. In any case, VBs are no longer readily available, and I can't go with seven VBs and five something elses, so I need all new balancers. I'm going put together 12 of the Lee Hart zener regulators. Again, due to the budget thing, and medium term plans to move to lithium, I don't want to sink more money into the current pack than necessary.

We'll see how it goes, but that's what the current fiscal priorities are leading me to.

Thanks again everybody for the analysis and recommendations. I'm always impressed by the speed, breadth, and depth of knowledge available here at DIYec.

Phillip


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## piotrsko (Dec 9, 2007)

Wasn't a guess, 45 years experience. Put whatever new you end up getting back on the negative side which will kinda balance the older capacities. Wouldn't hurt to mix positions on the older optimas either.


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## dtbaker (Jan 5, 2008)

with agm you pretty much need to consider rudman regulators to balance since there is no gassing cycle like the floodies..... you'll end up spending a fair amount per battery ($75) to do this, and might be better off saving up and upgrading to Li.


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## ARti (Oct 27, 2008)

I wound up replacing all 12 AGMs with Trojan AGM blemished units. It fit the budget. It's making the Odysseys look good. I'm rolling, and that's better than not rolling.

I also picked up shunt regulators from QuickCharge to replace the VoltBlochers. Very handy, industrial grade packaging, easy to install. I'll try to work rotation into my maintenance schedule so that the batteries at the end of the string don't get overworked.

Thanks again for the feedback and recommendations.


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## favguy (May 2, 2008)

Hi Arti,

Where would I find the Quickcharge regulators please? What do they cost?

I've just started to use my new conversion and built a set of Lee Hart zener regulators to protect the new pack of AGM's. However although the AGM's are new and a matched set, the zener's still just don't shunt enough current to keep the batteries in order (especially after any high current runs) and end of charge voltages are getting far too high on some batteries whilst others catch up, I'm having to watch them manually and shut off before absorption is complete .


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## ARti (Oct 27, 2008)

Send an eMail to [email protected] . Ray responded pretty quickly. They left them off when they updated their website. Here's some details: 








Since I've got 8 batteries in the back and 4 in the front, they made up three banks of four regulators. Nice and sturdy. It took about three weeks for them to show up at the door step.


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