# looking for BMS for lead acid batteries



## just_a_zoo (Jun 22, 2010)

Hi All... I'm working on my first EV conversion, and am wondering if anyone knows of where I could find a good balancer/equalizer BMS for flooded lead acid batteries. It is for a 96 volt pak.


----------



## Tesseract (Sep 27, 2008)

The Rudman Regulator is one product that does this. Note that I am not familiar with these outside of knowing they exist.


----------



## ewdysar (Jun 15, 2010)

just_a_zoo said:


> Hi All... I'm working on my first EV conversion, and am wondering if anyone knows of where I could find a good balancer/equalizer BMS for flooded lead acid batteries. It is for a 96 volt pak.


Alternatively, you can look into multiple-bank chargers. Dual Pro makes a 4 by 15A charger that operates as 4 separate 12v smart chargers. Your 96V system would need two of these chargers. These chargers are connected to each 12V battery (or each pair of 6V) and do their charging without having to separate the pack. The electric boat people are very pleased with how this is working and many are switching back from bigger 48V chargers. The Dual Pro is basically a 900W charger

Pro-Mariner makes a 30A charger that will manage 4 different batteries. This charger has the ability to shift amperage to the neediest battery, effectively allowing for 30A of 12v charging if only 1 out of 4 batteries is low, but since the batteries are connected in a pack, that type of inbalance is unlikely. The ProMariner is essentially a 450W charger. 

I've also seen some people suggest seperate small, inexpensive 12V chargers for each battery. This will perform the same type of balancing as BMS or multi-bank chargers.

That said, I'm using a 48V Elcon 2000+ with EV Works BMS modules for my lithium pack.

Eric


----------



## just_a_zoo (Jun 22, 2010)

The rudman regulator seems to be what I'm looking for, thank you



ewdysar said:


> I've also seen some people suggest seperate small, inexpensive 12V chargers for each battery. This will perform the same type of balancing as BMS or multi-bank chargers.


I have seen this too. How does one go about isolating each individual battery for this?


----------



## pgt400 (Jul 12, 2008)

most of the newer smart chargers are isolated...note the most not all.


----------



## ewdysar (Jun 15, 2010)

just_a_zoo said:


> I have seen this too. How does one go about isolating each individual battery for this?


You don't have to isolate the batteries when charging, as long as the entire bank is being charged at once. 

You can imagine that applying a single 12V charger to part of your battery pack will never complete charging the battery that it is hooked up to because the other batteries that are not charging would be adding load. In this situation, the hooked up battery would be taking considerable abuse by having all the current flowing through it to the other discharged batteries.

But if you had a seperate 12V charger attached to each battery, charging all at once, each battery has enough autonomy, even while wired in series, to allow the charger to select the charging phase according to that battery's needs. So the first battery to the constant current cutoff would start the constant voltage phase with decreasing amps, even while it's neighbor was getting still taking full amps. You won't get much cross battery flow since they are all in a charging phase and should be close to the same voltage. Once all the batteries get to the constant voltage phase, there won't be any cross flow, because there is no voltage difference. As each charger drops into the float phase, reduced voltage and amps, there will be some minor cross flow, but since the amps are down across the entire pack, the amount of current flow should be negligible. As long as one charger is pushing current, all of the batteries would stay at a higher than resting voltage, but not really getting any more charge. Once the last charger shut off, the whole pack would return to it's resting voltage.

While there is some room for a massively out-of-balance battery to confuse some of the chargers, this strategy will keep the batteries top balanced by tailoring the charge to each battery, so a dramatically out-of-balance situation would be rare. If you noticed that one charger ran consistantly longer than the others, it would indicate a failing cell. This is similar to noting that one battery never hit peak voltage and starting shunting with BMS.

This is why the multi-bank chargers, hooked up to individual batteries that are connected in series (like ours) or parallel (house batteries in RV's and boats) work so well in keeping the batteries in balance.

Eric


----------



## EVMAN (Jul 26, 2007)

just_a_zoo said:


> Hi All... I'm working on my first EV conversion, and am wondering if anyone knows of where I could find a good balancer/equalizer BMS for flooded lead acid batteries. It is for a 96 volt pak.


Flooded batteries do not need EQualizers. After 3-stage charging, you finish with an equalizing charge of 3 to 5 amps for a few hours. This bubbles the electrolyte and is a way of dissipating energy as ALL the cells come up to full charge. 

The ZIVAN NG3 does ALL this and is isolated.


----------



## 9852 (Jan 17, 2010)

just_a_zoo said:


> Hi All... I'm working on my first EV conversion, and am wondering if anyone knows of where I could find a good balancer/equalizer BMS for flooded lead acid batteries. It is for a 96 volt pak.


 
if you are able to solder, I have a circuit that you can have to ballance the batteries in your back, it monitors a 12v battery and cuts off power to the charger when the voltage reaches a preset limit, so if one battery reaches the charge limit, it will cut off power to the charger, and each one in secquence as they reach there limit.


----------



## ewdysar (Jun 15, 2010)

ewdysar said:


> Pro-Mariner makes a 30A charger that will manage 4 different batteries. This charger has the ability to shift amperage to the neediest battery, effectively allowing for 30A of 12v charging if only 1 out of 4 batteries is low, but since the batteries are connected in a pack, that type of inbalance is unlikely. The ProMariner is essentially a 450W charger.
> 
> Eric





findcarparts said:


> This charger has the ability to change the rating of the poorest battery, effectively allowing 30A 12V if one of the four batteries are low, but when the batteries are connected in a packet, this type of imbalance is unlikely. The ProMariner is primarily a 450W charger.


"Imitation is the sincerest form of flattery." (Charles Caleb Colton,1820). I guess I should be flattered... 

Eric


----------



## just_a_zoo (Jun 22, 2010)

billhac said:


> if you are able to solder, I have a circuit that you can have to ballance the batteries in your back, it monitors a 12v battery and cuts off power to the charger when the voltage reaches a preset limit, so if one battery reaches the charge limit, it will cut off power to the charger, and each one in secquence as they reach there limit.


I'm all ears... please, tell me more


----------



## mhud (Oct 19, 2009)

I have an order out for 9 PowerCheq modules for my 120V pack. Another forum user DONEAL has had success with these balancers (11 of them) for his 144V pack. I'll let you know how they work when I get them. I asked DONEAL how they were working and he said great. 

I have a single charger for my 10 AGMs and they get out of balance very quickly.


----------



## just_a_zoo (Jun 22, 2010)

mhud said:


> I have an order out for 9 PowerCheq modules for my 120V pack. Another forum user DONEAL has had success with these balancers (11 of them) for his 144V pack. I'll let you know how they work when I get them. I asked DONEAL how they were working and he said great.
> 
> I have a single charger for my 10 AGMs and they get out of balance very quickly.


Thanks Mhud, I'm looking forward to your results


----------



## dtbaker (Jan 5, 2008)

I don't think most people bother with a BMS on a pack of floodies.... if one goes over-voltage at the end of the cycle, it would just gas a little until others caught up.


----------



## mszhao (Oct 17, 2009)

more people now days are using lithium batteries because of its various advantages.but lead acid batteries are much cheaper. and generally no need BMS.
maybe you can try to use lithium battery pack +BMS+charger
or lead acid battery+elcon charger
elcon charger has high effiency and overall protection functions.
we can offer this charger to you at very good price.


----------



## dtbaker (Jan 5, 2008)

mszhao said:


> more people now days are using lithium batteries because of its various advantages.but lead acid batteries are much cheaper. and generally no need BMS.


lead may be half the cost, b ut with Li lasting 3x or 4x longer make more sense in the long run.... and are the only choice if you need more than 40 mile range.


----------



## Tafi (Jul 20, 2010)

There is cpompany called Reapsystems they do bms +442380 312944


----------



## DIYguy (Sep 18, 2008)

I'm not sure I would use an equalizer on floodies, but if you AGM/sealed batteries... I wouldn't run without them. I bought these.... awesome....

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

I have 5 of them on a 192 volt pack. Equalize 5 amps during charge, discharge and idle. I've even heard of them used with mixed batteries.


----------



## jumpjack (Sep 9, 2012)

Quite an old thread, but does anybody know where to buy such a BMS in Europe?


----------



## ElectriCar (Jun 15, 2008)

dtbaker said:


> I don't think most people bother with a BMS on a pack of floodies.... if one goes over-voltage at the end of the cycle, it would just gas a little until others caught up.


I did this on my pack of 24 6V batteries and ran them for nearly 9000 miles. A charger that will do an equalization charge is all you need. I have a Zivan NG5 that I used. The end charge was about 181V or 7.54V for a 6V battery. It just wastes a lot of power doing so but so would a BMS I suspect.


----------

