# BMS for AGM's. . . opinions??



## DIYguy (Sep 18, 2008)

Hi all,

I'm soliciting opinions regarding BMS for AGM's. Obviously, I'll need to control overcharge to help preserve the life and keep them balanced. Can anyone comment on their experiences (good and bad), preferrences, likes/dislikes. It would be most appreciated. Oh yes,...it needs to be capable of doing 16 x 12V batts.

I'm leaning towards Bryan's (Belktronix) at the moment. I think it is about $27/battery.. .there may be some additional costs...not 100% sure.

Thanks in advance.

Gary


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## bblocher (Jul 30, 2008)

Hopefully you'll get some better feedback here but I've yet to see a LA build using balancing. I haven't looked very hard either though to be honest.

It's my understanding that you should balance the LA cells by simply fulling charging each battery with your standard 12v charger, then put them in series and go. They can handle some over charging without issue, much better than LiFePO4 for example.

Using some type of monitoring system like the PakTrakr will give you the ability to check for a cell that is too low and you may need to manually top off a battery occasionally again with the 12v charger.

It's not going to hurt, but is it worth the extra cash?


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## DIYguy (Sep 18, 2008)

bblocher said:


> Hopefully you'll get some better feedback here but I've yet to see a LA build using balancing. I haven't looked very hard either though to be honest.
> 
> It's my understanding that you should balance the LA cells by simply fulling charging each battery with your standard 12v charger, then put them in series and go. They can handle some over charging without issue, much better than LiFePO4 for example.
> 
> ...


Hey Brian, thks for the reply. While its true that floodies don't require management, AGM's (and GEL's) do. The main issue is the effect overcharge has on the battery life. The float charge level can't be more than about 13.8V for most AGM's or life shortening impact will be the result. Floodies just boil and loose water but AGM's will boil and sebseqently vent. Since there is no way to replace the electrolyte, the increased acidic electrolyte, and reduced volume eventually causes early failure. Balance in itself isn't the biggest deal, but when bulk charging the pack, the imbalance will invariably lead to overcharging of some cells. . So. . . For AGM's, who's life may already be somewhat shorter. . BMS is a must. This phenomenon has contributed to the beliefe that sealed batteries have a short life. . . Which has truth to it but, may not be as bad as some believe, with the right care. I hope that made some sense. I'm on my BB and the typos are probably getting hard to take by now! ! Lol


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## bblocher (Jul 30, 2008)

Yeah as I was reading your post bells started going off and I recalled reading about the sensitivities of the sealed types and over charging.

If you have to go through the hastle of monitoring and balancing might as well go with LiFePO4. Seems you should end up saving quite a bit actually over the years. If they hold up like they say they will. 

I can't say too much about mine yet with only 130 miles on them.


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## DIYguy (Sep 18, 2008)

bblocher said:


> Yeah as I was reading your post bells started going off and I recalled reading about the sensitivities of the sealed types and over charging.
> 
> If you have to go through the hastle of monitoring and balancing might as well go with LiFePO4. Seems you should end up saving quite a bit actually over the years. If they hold up like they say they will.
> 
> I can't say too much about mine yet with only 130 miles on them.


A different battery chemistry is in my future.  the whole point of the BMS is so I don't have to go through any hasles of balancing. Monitoring I will do because I like to know, and I think everyone should monitor regardless of bat type. 
I bought 20 x 12 V AGM 135Ah batts, for $1000 ($50 each ) they r like new. I can't go wrong for a starter pack huh? ? 

I really hope u and the other trail-blazers have the best experience with the LiFePo4 chemistry. 
Thanks again. 

Gary


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## bblocher (Jul 30, 2008)

DIYguy said:


> I bought 20 x 12 V AGM 135Ah batts, for $1000 ($50 each ) they r like new. I can't go wrong for a starter pack huh? ?
> 
> I really hope u and the other trail-blazers have the best experience with the LiFePo4 chemistry.
> Thanks again.
> ...


Hopefully not side tracking your thread here too much. That is a great deal on the batteries. Are all 20 going into the vehicle or are some just spares? Definately a great starter pack. I almost went with LA but after looking at the little weight I could add to my already heavy car and range I needed, I knew there was nothing to test. Lead just wan't going to cut it. Good luck and keep us posted when you get rolling!


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## DIYguy (Sep 18, 2008)

Hey Brian,

My final pack voltage and number of batteries truly has been an evolution. Right from the start though, I wanted at least a 144 volt system. My current thinking and my system design is one that will allow perhaps more evolution. I am currently planning for 192 volts. I will start lower and I may even end up higher. All of my system components have been selected to allow this evolution and perhaps flexibility for the future. I want to see how the truck performs, range, ride and handling before I settle on it. It should be interesting. Short answer..... 16 batteries and some "spares". I may even rotate my spares through the pack like a spare tire hoping to get more overall life out of the pack by using all of them. It will take a little work and tracking...but, could be done. Whadaya think??


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## bblocher (Jul 30, 2008)

DIYguy said:


> Hey Brian,
> 
> My final pack voltage and number of batteries truly has been an evolution. Right from the start though, I wanted at least a 144 volt system. My current thinking and my system design is one that will allow perhaps more evolution. I am currently planning for 192 volts. I will start lower and I may even end up higher. All of my system components have been selected to allow this evolution and perhaps flexibility for the future. I want to see how the truck performs, range, ride and handling before I settle on it. It should be interesting. Short answer..... 16 batteries and some "spares". I may even rotate my spares through the pack like a spare tire hoping to get more overall life out of the pack by using all of them. It will take a little work and tracking...but, could be done. Whadaya think??


Sounds like a good idea to me. I wish I could have went higher voltage. I'm at 144 (max for my components) but if I could do it all again knowing what I know now I'd try for a 288 or higher volt AC setup (if I could afford the AC system).


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## Muju (Jan 25, 2008)

I have been looking for some kind of BMS system for AGMs for a while now and no luck. I have been thinking 144v of hawker odysseys but don't want to spend the money on AGMs if I can't protect them. For me the LiFePos are just too untested right now. I figured one set of AGMs would last me long enough for more people to test the LiFePos but am now wondering if I should just go with flooded if I am going to just kill the AGMs before their time anyway.


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## DIYguy (Sep 18, 2008)

Muju said:


> I have been looking for some kind of BMS system for AGMs for a while now and no luck. I have been thinking 144v of hawker odysseys but don't want to spend the money on AGMs if I can't protect them. For me the LiFePos are just too untested right now. I figured one set of AGMs would last me long enough for more people to test the LiFePos but am now wondering if I should just go with flooded if I am going to just kill the AGMs before their time anyway.


Well Muju, don't give up that easy! You can buy them from a few places. Talk to Brian at Belktronix, $27 each.

Another tidbit....
The simplest type is a Regulator (example: BatPro or Rudman Regulator). One goes across each battery. If the voltage during charging indicates that the battery is full, the regulator bypasses any further charging current through a resistor, to prevent that battery from overcharging. The excess charging power is burned up as heat.

A Balancer is a bit more sophisticated (example: Powercheq, Badicheq, Zizan Smoother). These systems also monitor individual battery voltages, but use a small DC/DC converter and switching network to transfer charge from one battery to another. Balancers can thus work to balance batteries even while parked or driving; not just while charging.


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## EVThing (Apr 20, 2011)

Hey Guys,

Looks like this is pretty old string, but I thought I would give it a shot. I just lost a pack of AGM after 18 months. The reason is poor charging and no load balancing. I've learned a lot in the last 6 weeks and am in the process of decide to move forward with a new pack or not. 

What I'm really interested in is these AGM for $50. I don't see anything for under $250. If I could get back on the road for $600 I'm back in. It's the 3k + that has me thinking.

If you are still around please let me know the type and where you got them.

Gary


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## DavidDymaxion (Dec 1, 2008)

Optima D31M (Blue Tops) about $145 each at CostCo. (Much cheaper than what I could find online.)


EVThing said:


> Hey Guys,
> 
> Looks like this is pretty old string, but I thought I would give it a shot. I just lost a pack of AGM after 18 months. The reason is poor charging and no load balancing. I've learned a lot in the last 6 weeks and am in the process of decide to move forward with a new pack or not.
> 
> ...


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## DIYguy (Sep 18, 2008)

EVThing said:


> Hey Guys,
> 
> Looks like this is pretty old string, but I thought I would give it a shot. I just lost a pack of AGM after 18 months. The reason is poor charging and no load balancing. I've learned a lot in the last 6 weeks and am in the process of decide to move forward with a new pack or not.
> 
> ...


I replied to your email. I think it is in ur spam folder tho.


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## HYPRDRV (Aug 20, 2009)

I'll mention I've been using the HDM balancers for the last 3 months on a pack of AGM's and everything seems to be happy. 

http://www.hdm-sys.com/

Steve


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