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Cheap Chinese Active Balancers
I have noticed that AliExpress have recently started offering "Active Balancers".

Knowing that these JUST balance and are not a complete BMS, has anyone had any experience with these?

There are apparently 2 types being offered. The second type appears to use capacitors to transfer charge from cell to cell, but not sure about the first type.

The first one has been reviewed by Julian Ilett:

There's someone else who's done it too, but I can't remember who did.
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There's a few threads on active balancers. Haven't really wanted to tinker with those cheap under $20 units. But have looked at some more capable units.

QNBBM, expensive when scaled up since they're 20 each. So for a 14S it would be $280.

No name 1A balancer. Not configurable, but balances to 40mV. I use these currently on my 7S300P build. Since they have a serial output that I use to log the data in my build. Under $100 for a 14S setup. If you look at my build I did some small test on it. I'm actually more interested in the one below that I'm waiting to arrive any day.

Another 1A active balancer. This is highly configurable, and bluetooth output. Just bought one of these to test. Under $100 for a 14S setup.
This looks built to last:
(11-18-2019, 11:26 AM)Overmind Wrote: This looks built to last:

Why? Just because it has big resistors?

In all honesty, there is no need for an active balancer in a powerwall. If your battery bank is constantly balancing, there are either cells near failure or the batteries are terribly mismatched in terms of capacity. It's best to address the underlying issue rather than masking it with an "active balancer" and hiding other potential problems/warning signs along the way.
Yes. I did have some problem with resistors including on various chargers like Xtar. Soviet-era resistors always permanently fixed the problem.
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(11-18-2019, 12:32 PM)mike Wrote: In all honesty, there is no need for an active balancer in a powerwall. If your battery bank is constantly balancing, there are either cells near failure or the batteries are terribly mismatched in terms of capacity. It's best to address the underlying issue rather than masking it with an "active balancer" and hiding other potential problems/warning signs along the way.

I disagree on that an active balancer is useless.  I think that term should apply to all balancers. An active balancer just works differently, but otherwise works like any other balancer would. Being active doesn't necessarily mean that it's always balancing. It just means it's not passively dissipating the energy as heat like a batrium would. Instead it's transferring some of the energy back into the system. The active balancer can be set to only balance at certain deviations, therefore should sit idle most of the time, just like a passive balancer would. Its only advantage is that it doesn't waste the energy during the balancing. My wall stays under 30mV difference at all times. It can do that for months at a time. My active balancer only kicks in at 40mV and it does that only occasionally, so bringing in some of the slightly out of balanced packs. That is a normal occurance.

So the correct thing to say is that is no need for a balancer in a powerwall.
So if you dont balance you dont move any energy and therefore a passive ballancer would have been cheaper

What Mike and me and many other is trying to say is that the cost getting active balancer does not pay off on a proper battery bank. With that said moste of the "cheap" active balancers only HIDE the balancing done meanwhile a decent passive balancer even reports back on how much off a cell is.

I calculated it and on my battery bank it would take 15+ years before i even save anything buying active balancers instead of the passive i had today.

Also note that you generally balance when you have excess energy that in most cases also gets wasted.

Add upp the fact that an active balancer also wastes energy so for the purpose they are built they are ment to balance during bottom and top meaning they always move energy back and forth... Tongue

Active balancer have their purpose for sure but in most powerwals they only hide whats going on and people need to understand why you balance and when before masking it.

I would say "It should not be needed" Smile
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I don't see how an active balancer is more expensive than a passive balancer. Last time I check a decent active balancer that is configurable is under $100 for a 14S setup. So cost is not an issue here. If you're trying to calculate the ROI of a active saving you money, then yes I agree it's never going to pay back. An active would be more efficient in how it's balancing, so reduction in heat. Again, you're under the general assumption that an active balancer is balancing 100% of the time, wasting energy transferring between cells all the time. That's not the case. You set it to only transfer when there is enough deviation between the cells. Over time you can tell which cell is always going out of balance just as much as a passive system would since it will always be the highest in deviation.
these are the ones that I have used. the top one, I bought a 4s version for 12 dollars, and connected to an out of balance battery, after 5 hours nothing happened, it was still out of balance. I bought 2 of them and both perform the same, they are useless to balance a pack.

The middle one, I bought the 4s version(20 dolllars) and Also after 5 hours the battery was still out of balance but it did  balance a small bit. But it would be insignificant.It does work but very slowly, it would take days to balance an out of balance pack. But it will keep a pack that is mostly balance, in balance.

The bottom one I also bought a 4s version (95 dollars) that one actually works and I use 24/7 on a 4s 220ah lifepo4 that has balancing problems. This one keeps up if you like to fast charge your battery.

I like my batteries to be in perfect balance, thats why I use the active balancers. I also like to fast charge my packs, active balancers lets the battery stay balance close to the top end, without the balancers I would never get a full charge on my 220ah lifepo4 pack, the bms would activate too early.


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