# Lead Acid BMS



## jxm1029 (Oct 12, 2012)

Hello all,

I have been trying to find information regarding lead acid battery management systems but have not had much luck. I'm trying to find and/or design my own system that would work with a 12V lead acid battery. I want to have something that can work with a single 12V battery or 4 or more batteries in series (48V). I also was hoping to have a way to communicate with the board to an independant controller through usb or an rj45 connection if possible although I would settle for a serial connection as well. If someone could please point me in the right direction I would greatly appreciate it. Thanks.


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## frodus (Apr 12, 2008)

Do you just want to monitor? Because lead acid batteries are a bit more resistant to unbalancing (but they do get unbalanced). It's sometimes easier just to charge each 12V battery individually once in a while.

I know Manzanita Micro has a system for lead.


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## Ziggythewiz (May 16, 2010)

What kind of lead?


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## midelectric (Mar 27, 2011)

There's Lee Hart's Battery balancer as well, it actively shuttles energy between modules to keep them all at the same SOC. He's supposed to release the logic board soon, I have the relay boards and a power (?) board sitting around that I don't think I'll ever use at this point. It was to control a 24 module pack and is available if you want to go in that direction.


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## jxm1029 (Oct 12, 2012)

> Do you just want to monitor? Because lead acid batteries are a bit more resistant to unbalancing (but they do get unbalanced). It's sometimes easier just to charge each 12V battery individually once in a while.
> 
> I know Manzanita Micro has a system for lead.


I just want to monitor at this point I think and as I learn more about building and making a BMS i would move towards controlling and doing other things. I will definitely check them out thank you.



> What kind of lead?


Lead acid? I want it to be applicable to any lead acid battery really, and again as I learn more about designing these and how they work I will probably move on to Li type batteries.



> There's Lee Hart's Battery balancer as well, it actively shuttles energy between modules to keep them all at the same SOC. He's supposed to release the logic board soon, I have the relay boards and a power (?) board sitting around that I don't think I'll ever use at this point. It was to control a 24 module pack and is available if you want to go in that direction.


I will look into this and see if I can find information on that. In the event I can't find Lee Hart's balancer do you have a link to more information about it?


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## Ziggythewiz (May 16, 2010)

jxm1029 said:


> Lead acid? I want it to be applicable to any lead acid battery really, and again as I learn more about designing these and how they work I will probably move on to Li type batteries.


Flooded lead acid doesn't need any pack balancing. It self balances every charge by gassing. You might have one battery that goes to 13.2V and another that only gets to 13, but both are 'full' and trying to balance them would accomplish nothing.

Other kinds of lead acid are different, and the exact voltage they require (which you'd have to build into the BMS) would vary.


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## jxm1029 (Oct 12, 2012)

Ziggythewiz said:


> Flooded lead acid doesn't need any pack balancing. It self balances every charge by gassing. You might have one battery that goes to 13.2V and another that only gets to 13, but both are 'full' and trying to balance them would accomplish nothing.
> 
> Other kinds of lead acid are different, and the exact voltage they require (which you'd have to build into the BMS) would vary.


Well I would intend to use the same kind of battery across the board so could we look at it both ways whether i had to balance the batteries or not?


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## Ziggythewiz (May 16, 2010)

so...what battery?


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## jxm1029 (Oct 12, 2012)

Something along the lines of these two batteries which it seems are AGM based on the sheets? Only the second one specifically mentions AGM the other just says SLA.

http://www.enersys-emea.com/reserve/pdf/EN-SBS-EON-OGH-002_0909.pdf

http://www.ddbunlimited.com/wp-content/uploads/2012/02/RPS-LDT-TDS-S1.pdf


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## Ziggythewiz (May 16, 2010)

First looks interesting, 1500 cycles to 50% dod...but shelf life of 2 years. I guess their definition is different from mine.

2nd is VRLA, so tons of google hits for BMS info.

They look pricey though, how do they compare to lithium?


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## alvin (Jul 26, 2008)

jxm1029 said:


> I will look into this and see if I can find information on that. In the event I can't find Lee Hart's balancer do you have a link to more information about it?


 
LINK

Lee Hart's balancer is down the page at that link.


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## midelectric (Mar 27, 2011)

Some info on Lee Hart's balancer;
http://www3.telus.net/nook/balancerland/balancer/index.htm


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## jxm1029 (Oct 12, 2012)

Ziggythewiz said:


> First looks interesting, 1500 cycles to 50% dod...but shelf life of 2 years. I guess their definition is different from mine.
> 
> 2nd is VRLA, so tons of google hits for BMS info.
> 
> They look pricey though, how do they compare to lithium?


Well I haven't dabbled much in the battery world so this is relatively new to me (in case it wasn't obvious lol) so I don't know how they compare to lithium. The first ones were donated to me though so those would be my primary choice for a bms system. I'm assuming they self balance? As you can see though because they are two different type batteries that's why I wanted the ability to change my BMS on the fly with some type of microcontroller where I can load in parameters given the battery style i'm using.


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## Ziggythewiz (May 16, 2010)

Can't argue with free.

No, those do not appear to self balance. I'm not aware of a BMS that adjusts on the fly. Usually you have tailor resistor values and such to match the desired top and bottom limits. Just read up on the links others are providing and have a go at it.


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## jxm1029 (Oct 12, 2012)

midelectric said:


> There's Lee Hart's Battery balancer as well, it actively shuttles energy between modules to keep them all at the same SOC. He's supposed to release the logic board soon, I have the relay boards and a power (?) board sitting around that I don't think I'll ever use at this point. It was to control a 24 module pack and is available if you want to go in that direction.


Do you have pictures of these? I've been looking at Lee's balancer and then I took a look at Tim Wong's BMS and it looks like that might apply to me a bit more. Plus I don't necessarily like the idea of lots of relays to monitor. I was hoping to have something that very simply monitored 1 battery in a series and then reported back to to a main controller through some comm port. This way i could make one board per battery and the size would still remain fairly small.


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## DIYguy (Sep 18, 2008)

Ziggy is right about floodies, they balance at the top of the charge. For SLA, you need a balancer since you don't want to "boil" them. 

I did a lot of searching on this several years ago when I was running AGM's. I would recommend the HDM Equalizers. I used them and they work famously. They balance at rest, during discharge and during charge. 
Check them out. . http://www.hdm-sys.com/products/equalizer.php


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## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> Flooded lead acid doesn't need any pack balancing. It self balances every charge by gassing. You might have one battery that goes to 13.2V and another that only gets to 13, but both are 'full' and trying to balance them would accomplish nothing.
> 
> Other kinds of lead acid are different, and the exact voltage they require (which you'd have to build into the BMS) would vary.


If you want to be able to change the bms for different chemistries etc, you might want to consider using an Arduino to manage them. It can use multiple input ports for voltage values, you can use it for controlling cooling, discontinuing charge when the SOC is correct and even use it to apply charge to specific modules. 

It might be ideal for your type of setup.


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## HYPRDRV (Aug 20, 2009)

I will second the HDM Equalizers. Been running them for 2 years? without any problems.


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## dtbaker (Jan 5, 2008)

thread caught my eye.... If you are running sealed lead (AGMs) like Optima or similar, you probably do want to consider a BMS that will shunt and balance as they do not self-balance like floodies that have a gassing cycle at end of charge.

I happen to have a set of the Manzanita Rudman Regs for sale that I pulled from a lead build I am upgrading to lithium.

so.... if you have an AGM pack, consider these.


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## wsv3424 (Apr 3, 2011)

still have it?


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## [email protected] (Jun 14, 2011)

http://www.evdl.org/docs/zenerregs.pdf

Lee Hart PDF on how to: I think this is for 6 volt batteries.

If so, can anyone adapt to 12 volt batteries besides putting two on each

battery?


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## dtbaker (Jan 5, 2008)

[email protected] said:


> http://www.evdl.org/docs/zenerregs.pdf
> 
> Lee Hart PDF on how to: I think this is for 6 volt batteries.
> 
> ...



dunno..... but I have a set of 12 rudman regs designed for 12v AGMs for sale in classifieds if you want to consider that.
http://www.diyelectriccar.com/forums/showthread.php?t=79452


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## alvin (Jul 26, 2008)

[email protected] said:


> http://www.evdl.org/docs/zenerregs.pdf
> 
> Lee Hart PDF on how to: I think this is for 6 volt batteries.
> 
> ...


 
They are for a 12 volt battery. This link has parts list for other voltages.


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