Balancing Voltages and Currents

Watching cell voltages and balancer currents on a 4S LiFePO4 battery

[@12villages]

Internal resistance of those cells are different so they will never balance charge without a bms

[@nickjones886]

Ive noticed a battery pack (i made) that i fitted with a active balancer runs down way faster than just having a bms that balances around the 90% SOC mark.. So i have to recharge it frequently..

[@JulianIlett]

Yes, they do consume power, but that's OK if the battery is solar charged.

[@sailingoctopus1]

Presumably, once you are satisfied that the active balancer is working as intended you can get rid of all the meters. I need an active balancer for my 24S pack and don't fancy all the wiring involved

[@JulianIlett]

I could, but I won't. For the 8S battery, I'll need 8 voltmeters, an 8-way balancer and a larger piece of wood :)

[@donepearce]

My question is whether two batteries at identical voltage are in fact at the same state of charge. I think things may be a little more complicated. It would be a good experiment to now discharge this system minus the balancer and see if all the batteries discharge to their end point at the same time. Then do it again, but this time allowing them to reach whatever voltage they charge to without forcing them to the same point

[@JulianIlett]

Each cell has a different capacity, so they will only reach their bottom endpoint together if you bottom-balance the pack. Most people want the cells to reach their top endpoint together, so they top-balance the cells.

[@restorer19]

With enough parallel cells per series bank (nP4S) and enough testing and swapping cells, you can eventually get all the series levels to have nearly-identical charge state-voltage curves. Though the number of potential combinations of cells gets pretty big once you have enough cells to reasonably balance their capacities in banks.

[@panospapadimitriou3498]

what cells are working with 46160 holders????? /... they are small i loved em

[@SlyerFox666]

Nice, Would be interesting to see meters again after battery has been used, charging without balancer to see how big of a difference the cells would be out by. 👍

[@JulianIlett]

From my observations, quite a bit different.

[@SlyerFox666]

@@JulianIlett Oh thanks for the reply, do you think it would cause much damage over time to the cells if you didn't balance them or could be a fire risk ?

[@davestech6357]

The balancer discharges the pack when hooked up continuously. It would be better to use tl431 shunt regulators on each cell set at 3.5 volts. Then it top balances the cells only.

[@JulianIlett]

Fine if you're charging the battery daily.

[@Electronzap]

Nice.

[@jlucasound]

Thanks Julian!! 🤩😍⭐⭐⭐⭐⭐

[@marcosmercado5648]

Hello from Puerto Rico! Nice setup and testing method. Where did you get those single cell voltmeter? I need a few of those, also for a LiFePO4 project.

[@JulianIlett]

They're BT168D or BT168 PRO battery testers. Cut up and fitted with JST connectors :)

[@marcosmercado5648]

@@JulianIlett Great, thanks for the info!

[@galen__]

👍

[@fredflintstone1]

julian I have watched your videos on battery balancing and wonder could you do one on Bank account balancing as that is where I need help🙂

[@JulianIlett]

Yeah, don't mine crypto, that won't help at all :)

[@ShafaqIftikhar-pw9ld]

LOL😂

[@TheEmbeddedHobbyist]

i have a weight balancing problem, it's all in the middle 🙂

[@fredflintstone1]

@@TheEmbeddedHobbyist Hmm, is it all out front in the middle?????😉

[@TheEmbeddedHobbyist]

@@fredflintstone1 yep, but the gym is slowly moving it to the legs and arms, ;-)

[@JasonWee]

very complex...and highly technical...

[@frankowalker4662]

That was really interesting. Cheers, Julian. 👍

[@stevenc22]

Grab a good RC charger like a icharger x8 or isdt to charge the cells. It will charge and balance at the same time.

[@kapegede]

Sure he could, but that's not the point of this vid. It's about showing and understanding how batteries and a balancer works.

[@robertgoddard6787]

I love contraptions. Great stuff.

[@restorer19]

What's the net current draw of the battery voltmeters and the balancing board at steady-state? About 20 mA, as in the last shot?

[@JulianIlett]

The voltmeters pull a few microamps. The balancer a few milliamps.

[@pmacgowan]

You need a DC clamp meter

[@JulianIlett]

They're useful, but you do have to keep zero-ing them.

[@markclark787]

Great explanation!

[@TheEmbeddedHobbyist]

i think the best way to go is buy the biggest capacity battery you can or just make up a 1s50p and use a boost converter to the voltage you want. No issues with balancing as they are using a bloody big wire to balance them all.

[@JulianIlett]

You'd have to parallel up the boost converters too. As luck would have it, that's the subject of my next video :)

[@TheEmbeddedHobbyist]

@@JulianIlett back in the days of nickel-cadmium battery packs, before the days of power management etc. a single cell pack and booster was the most reliable way to go.

[@aldoconciso]

a 1s50p pack could give around 100A, which at 3V is just 300W... And you'd have to disconnect each cell to check them

[@TheEmbeddedHobbyist]

@@aldoconciso but you wouldn't ever need to balance them. But point was a single large cell.

[@aldoconciso]

yes, they would self-balance, and also self-discharge faster. And don't forget about thermal management, as voltage depends also on temperature. About doing it with a big single cell, i guess it's difficult to make them much bigger because of problems with heat dissipation

[@electro2606]

Hi 👋

[@himselfe]

For a moment I was half expecting the "A while later" screen to cut to a video of the fire brigade standing around the smoldering remains of a shed. Incidentally, would the balancer work better or worse with the charge current turned off? i.e so the only power transfer is between the cells.

[@Irilia_neko]

This type of balancer, will not do a lot, possibly 300 ma max

[@JulianIlett]

I consider 300mA to be a lot. The BMS balancers do about 30mA.