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Anybody ever parallel 2 or more of the the Heltec 5A active balancers?

Maast

Compulsive Tinkerer
Joined
Oct 31, 2019
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Location
Washington State
I think I'm going to need a LOT more balancing amperage: When I'm done each of the cell groups of my 48v BYD bank is going to have 1125AH per cell group. I've got a string of QNBBMs that can do 5-6A but the highest I've seen in actual use is 1.4A with a .25v differential.

Even with all the tinkering and adding capacity to the weak cells these BYDs are always going to be badly mismatched and I can easily see a cell group getting out of balance and the QNBBMs not being able to keep up - especially in the winter where extremely deep discharges followed by extended high amperage charging is likely.

I'm thinking if I parallel 3 of these I can avoid a premature bank shutdown but I have no idea how well the balancers will play with one another. The ones I'm looking at is the https://heltec-bms.com/product/5a-capacitive-active-equalization-active-balancer/ .

At only $50 per balancer its by far the most cost effective solution I've found so far.

Thoughts?

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I use QNBBM8S models but not with the BYD cells but with EVE 280's & Ayupower 174's. I can't actually say what the amperage is during transfer between cells but they do level up the cells quite nicely. The Winter Workout effect has been superseded by my Thrash tests which is more intense... That stressing has afforded the QNBBMs a workout too. Fortunately the cells I have are not too bad with their drifting at the top.

Heltec offers a few different Active Balancer models including with small super-caps and of course the price reflects such but some of their gear can moive serious amperage.

I do feel I should remind you, there is no BMS or Balancer of any kind that can fix FUBAR Cells. They can "help" with weak cells and even Runners to a point.

BTW: The Heltec Site you are looking at is incomplete. Their Alibaba Store has the full line of products.
Here is a link to the 8S active Balancers: 8S Active - search result, Chengdu Heltec Automation Technology Co., Ltd. (alibaba.com)
Note the more advanced 5A models are not that cheap Page 3 ?). I can't speak to the difference in methods but some have BlueTooth and other features as well, which of course piles on the extra $.
 
I have read your other thread and thought your addition of Headways was ingenious. Having lived with the limitations of a Frankenpack of differeent vintages of Nissan Leaf modules I admire your persistence. At some point I needed more capacity and the thrill of a new pack overwhelmed me. It all depends on where you are standing.
 
I think I'm going to need a LOT more balancing amperage: When I'm done each of the cell groups of my 48v BYD bank is going to have 1125AH per cell group. I've got a string of QNBBMs that can do 5-6A but the highest I've seen in actual use is 1.4A with a .25v differential.

Even with all the tinkering and adding capacity to the weak cells these BYDs are always going to be badly mismatched and I can easily see a cell group getting out of balance and the QNBBMs not being able to keep up - especially in the winter where extremely deep discharges followed by extended high amperage charging is likely.

I'm thinking if I parallel 3 of these I can avoid a premature bank shutdown but I have no idea how well the balancers will play with one another. The ones I'm looking at is the https://heltec-bms.com/product/5a-capacitive-active-equalization-active-balancer/ .

At only $50 per balancer its by far the most cost effective solution I've found so far.

Thoughts?

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I have a 400Ah Lifepo4 DIY pack that I built. I am running a Daly 200A smart BMS that has 0 ability to balance cells. Purchased a Heltec from Amazon and it balanced a 0.51V imbalance to 0.01 in about 10 hours. I, too, am wondering if 2 balancers in parallel would increase balance amps during heavy charge (>50A). Thoughts?
 
I think the results could be unpredictable. There is no way to coordinate and one could try to fight the other one. it is not simple like putting two resistors in parallel.
This.

To add to @Ampster's point: I have watched the voltage on my cells when I plug-in / unplug an active balancer. As soon as the balancer is plugged in, the current starts to flow out of the highest voltage cell. This causes the voltage of that cell to "sag" so it appears to not be very far out of balance. I've done this with both the capacitor based Heltec balancer and the QNBBM-8S. My guess is this would confuse the second balancer (and subsequent balancers if you try more than two), and cause it to think it doesn't need to do anything. If this is the case, you could have a dozen active balancers attached to a pack, and only one would be doing anything at any one time. I'm only speculating, but it makes sense to me.

Edit to add: I will confess my experiments have been only with an 8S pack of the 25Ah Top Band cells. I guess a larger cell might not sag as much, so maybe it would not be as bad as what I described.
 
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DIY 400 amp hour LifePo4 battery box is complete. 200A BMS, dual active cell balancers (in parallel, Daly balancer sucks!), thermostat controlled heating pad. Ready for installation.
 
The balancer supports parallel and cascade,
parallel method can get more balance current
cascade method can adapt more battery strings

but for Lifepo4 battery i suggest the balancer which can adapt for top balance function

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What unit did you end up buying?
This guy, fair warning though, it wasnt cheap at about $530. The cool thing is that it moves 10A even when the voltage is only a few millivolts apart.

I had to get something with that amount of amperage because my bank is rather large @64kwh and anything smaller wouldnt keep up with my badly mismatched BYD module bank. I've got it set to start balancing at 3.38v/cell.

A non-mismatched bank of the same size could probably get by with a 5A balancer.

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Yeah too spendy for me I have 600 amps lto they swing wildly at the top end in a few minutes they can go from balanced to 2.6 to a group of cells to 2.9 while the rest 2.6. The 5 amp balancers only balance at like 1.6a per cell. What side of Washington are you on I'm in spokane. What cells are you running?
 
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@Maast does this balancer have additional outputs that could be used to control other things like relays, shunt breaker and etc. ?
I would appreciate if you would give me more information especially experience you have gained using it. This could be interesting gadget I would try to play with.
 
@Maast does this balancer have additional outputs that could be used to control other things like relays, shunt breaker and etc. ?
I would appreciate if you would give me more information especially experience you have gained using it. This could be interesting gadget I would try to play with.
No, it's strictly a active balancer, albeit the highest amperage balancer that I know of.
 
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