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Forum Index : Electronics : LiFePo4 BMS & Balancers: Anyone use Heltec?

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flyingfishfinger
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Joined: 12/09/2020
Location: United States
Posts: 117

Posted: 06:33pm 24 Mar 2025

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Hi there-
I wasn't sure where to ask this question exactly, but I figure here would be a good bet. The Heltec customer support is pretty nonresponsive, I haven't gotten a clear answer from them about this.

I picked up a couple GlobalPower GPS12100B batteries for cheap recently, without doing a lot of up-front research (hence my question in the other thread about using Poida's MPPT with LiFePo4 packs)

Turns out, the cells are probably great but the BMS / balancing is trash (see Youtube reviews: https://www.youtube.com/watch?v=FGtoiH5dWSI and https://www.youtube.com/watch?v=pGAc-fQPmNY )

That guy suggests he retrofitted a Heltec capacitive balancer onto the existing BMS, which solved the charging & balancing problems but does NOT fix the over / undercharging or temperature detection issues.

Now, Heltec also makes this BMS , which SUPPOSEDLY includes balancing already. So in theory I should get that, right? I asked Youtube guy, he agrees in principle that this would probably be better, but he hasn't tried it.

Here's the wrinkle. On Aliexpress I can buy a COMBINED package which basically sells the BMS and the capacitive balancer together implying I could use them in parallel. I asked Heltec support, all they said was "Yes, can" but that seems contradictory to me. If the second device link I sent already includes balancing, adding the capacitive balancer would seem unnecessary or even harmful, if the balance theresholds aren't the same between devices.

So - to combine or not? Anyone have experience with Heltec devices?

Cheers,
R
Edited 2025-03-25 04:35 by flyingfishfinger

Dinosaur

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Joined: 12/08/2011
Location: Australia
Posts: 323

Posted: 08:12pm 24 Mar 2025

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Hi All

My system in the Caravan and later my Ute camper consist of single cells combined into a
200+ AH 12V battery. The BMS is a Rpi Zero with separate Cell Voltage sensing A2D.
This system controls the charging and discharging according to software and SSR's.
In other words not a single case Hybrid type battery.
I have used the 4S balancers for years and basically confirmed that they work.

Not used their BMS, BUT if you are asking if a BMS can co-exist with the balancer then definitely YES.
I have tried to detect capacitor discharge spikes with a CRO, but I think the impedance of the battery is to low for that.
Therefore I doubt that the BMS would see them and react to them.

When charging without a balancer, the time it takes to naturally dissipate to all the cells
is significantly longer then when the balancer is fitted.
With software I can apply a lot of rules as to when it is allowed to do what and this combo
has not failed me for the last 10 years.

Regards

Regards
Hervey Bay Qld.

flyingfishfinger
Senior Member

Joined: 12/09/2020
Location: United States
Posts: 117

Posted: 08:14pm 24 Mar 2025

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Fair enough. I guess the main question is, does anyone know if the Heltec-type BMSs (there exist a lot of lookalikes, it seems) DO in fact include balancing (since they do have a plug for it, and the datasheet says so), how that interacts with the external balancer...

Thanks for the input though!

EDIT: I think I figured out part of it. The BMS boxes include PASSIVE balancing, whereas the capactive devices are ACTIVE. Therefore the theresholds for balancing in the passive should be overridden by the actively managed one, and I should be able to use both devices together correctly.
Edited 2025-03-25 06:21 by flyingfishfinger

KeepIS

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Joined: 13/10/2014
Location: Australia
Posts: 1816

Posted: 10:17pm 24 Mar 2025

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flyingfishfinger said EDIT: I think I figured out part of it. The BMS boxes include PASSIVE balancing, whereas the capactive devices are ACTIVE. Therefore the theresholds for balancing in the passive should be overridden by the actively managed one, and I should be able to use both devices together correctly.

This is typically of most BMS devices that include passive balancing. Most BMS devices allow you to set Balance start voltage, Delta, and to either enable or disable passive balance.

I've tried combinations in testing and never seen any problems, with an external higher current active balancer and the BMS internal passive balancer, I've never seen any CELL conflict on my four parallel 53V banks, but IMHO passive balance is fine for NEW matched CELLS, but it also depends on charge current and other battery build variables, over time as batteries age I've found Active balancing to be very effective.

I do an occasional top balance once a year as I don't fully charge the LiFePO4 banks.

I see some newer BMS mention inbuilt active balance, but you need to check if the max balance current in these is comparable to an external Active balancer.
.
Edited 2025-03-28 07:42 by KeepIS

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