bmiller
New Member
Just wondering if it's possible to use a BMS to keep 12v batteries balanced with each other when connected in series such as a 4s 48v system etc?
BMS to maintain balance 12v batteries in series
- Thread starter bmiller
- Start date
DVD
New member and getting older
There’s a 12v balancer that can be connected to 2, 3, or 4 in series. Uses capacitive charge distribution. Basically sequentially connects a capacitor to one battery then switches to the next battery, etc.
Search Amazon for PwrMr battery equalizer.
Search Amazon for PwrMr battery equalizer.
Ampster
Renewable Energy Hobbyist
It is sub optimal compared to having 16 cells in series with one BMS. There are products, as mentioned above which will do what your want.
Lt.Dan
Solar Wizard
If each battery has its own BMS, then fully charging to 58.4v will bring them all up to the same SOC. the highest battery with disconnect and so taking current until the others catch up.
No Balancer needed.
No Balancer needed.
sunshine_eggo
Happy Breffast!
I'm having trouble understanding this.
Did you mean to say the highest battery will disconnect? If you didn't mean that, please clarify. If you did mean "will", that's not how it works. If the highest battery disconnects, current stops. As far as the charger is concerned, it's an open circuit. Current does not bypass the disconnected battery.
12V balancers for 12V batteries in series are very useful.
Lt.Dan
Solar Wizard
My apologies, I posted that very tired yesterday, and I can tell its pretty incoherent. You are right, once one disconnects, they all get cutoff.
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DVD
New member and getting older
I’ve been looking for an advantage of lead-acid….. yea! I found one ?? LOL
I ran the balancer mentioned and it works well for the most part. However it consumes a noticeable background power even after the batteries are balanced. Just the electronics I presume.
I ran the balancer mentioned and it works well for the most part. However it consumes a noticeable background power even after the batteries are balanced. Just the electronics I presume.
sunshine_eggo
Happy Breffast!
bmiller
New Member
Thank you all for the feedback. I will check out the battery equalizer as I'm looking for a more automated way to ensure all 4 batteries remain at same SoC, rather than breaking it down and charging each one individually.
RCinFLA
Solar Wizard
- Joined
- Jun 21, 2020
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24v (two 12v battery) HA01 models are capacitive based balancers. 48v (four 12v batteries), HA02 models are inductor based charge balancer.
On both models the amount of transfer current is a function of how much voltage difference between batteries. Although they may claim 5 or 10 amps of balancing it requires several volts of difference to accomplish that much transfer current. At less than 100 mV difference there is 20-100 mA's of balancing transfer current.
If using LFP self contained 12v battery with internal BMS, the external 12v balancers are not necessary as the internal BMS will equalize the batteries when doing a full charge. A resistive dump BMS balancer does not transfer current between cells. It only dumps current when an individual cell gets above 3.4 vdc.
For resistor dump balancing, having four separate 4 cell BMS's in series connection is no different than having a single 16s BMS balancer.
Not relating to balancing, each 4s BMS must have series MOSFET's with breakdown voltage rating of 70-100 vdc for a 48v system. Need to check 12v LFP specs to ensure the batteries can be series stacked, meaning they have high enough BMS breakdown voltage for higher series stack voltage. Not all 12v LFP batteries have stacking capability due to use of lower voltage MOSFET's in their BMS.
On both models the amount of transfer current is a function of how much voltage difference between batteries. Although they may claim 5 or 10 amps of balancing it requires several volts of difference to accomplish that much transfer current. At less than 100 mV difference there is 20-100 mA's of balancing transfer current.
If using LFP self contained 12v battery with internal BMS, the external 12v balancers are not necessary as the internal BMS will equalize the batteries when doing a full charge. A resistive dump BMS balancer does not transfer current between cells. It only dumps current when an individual cell gets above 3.4 vdc.
For resistor dump balancing, having four separate 4 cell BMS's in series connection is no different than having a single 16s BMS balancer.
Not relating to balancing, each 4s BMS must have series MOSFET's with breakdown voltage rating of 70-100 vdc for a 48v system. Need to check 12v LFP specs to ensure the batteries can be series stacked, meaning they have high enough BMS breakdown voltage for higher series stack voltage. Not all 12v LFP batteries have stacking capability due to use of lower voltage MOSFET's in their BMS.
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Captain Kirk
New Member
So if I may paraphrase, these balancers are not worth it? In my instance, I have 4 SOK 12V batts in series. The voltage difference of ~0.1/0.2 VDC would not maximize the battery charge/discharge cycle enough to be worth the investment? The batteries will likely outlive me, so I'm not worried about their longevity...Thanks!
DVD
New member and getting older
For the most part I agree the balancers are probably not worth the effort and expense. Particularly true if your batteries are all the same production lot and we’re top charged first.
If your batteries start to exhibit misbalance conditions, you can individually top charge each battery independently.
If your batteries start to exhibit misbalance conditions, you can individually top charge each battery independently.
pollenface
Solar Addict
With that in mind, my AGM banks always exhibit slightly different voltages on the end batteries. Last time i checked with a HA02/PowMr balancer ($67aud) each battery was exactly 14.17v. Well worth the effort in my opinion. If you wish to go without, that's your choice as a free man/woman ?
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