Is there a BMS for only charging?

I have three small 4000mah 4S lipo batteries(turnigy graphene) that I charge separately , and put them in series(3X xt60 to one xt90) to use with my bbshd.

Does a BMS exists for charging only those batteries? Something I could plug all balance wires into and plug the series discharge lead to charge. Something with flexibility would be perfect, in the case I decide later to buy some more.

I find generic BMS but nothing else that is made for lipo users.

Thanks

this thread might help

https://endless-sphere.com/forums/viewtopic.php?f=14&t=105146

You could use a balancing RC lipo charger. Thunderpower has a badass 12s 1300w charger for only 200 bucks. I like it it's a nice charger.

fredfire said:

I have three small 4000mah 4S lipo batteries(turnigy graphene) that I charge separately , and put them in series(3X xt60 to one xt90) to use with my bbshd.

Does a BMS exists for charging only those batteries? Something I could plug all balance wires into and plug the series discharge lead to charge.

Click to expand...

keep in mind you cannot parallel the balance leads, so you need three separate units, or a wiring harness to connect the three seriesed packs to that connects the balance leads in series as well.

if you parallel the balance leads, you short the batteries out, and either destroy the balance leads or possibly set the packs on fire. but the shorting out would still destroy them.


you could use the various rc battery meters, one per pack, like battery medic, celllog, or other similar things, if you need to see all the voltages at the same time. or something like the 12s thunderpower flattire proposed above, presumably using a harness made to connect all the leads in series. (*not* parallel! -- very important!)


however...nothing other than a complete bms system will actually protect your packs against overcharge when bulk charging them in series, if that's your goal, because it's the only thing that can shut off the charging input when any cell becomes full.

there are two basic kinds of bms, balancing and non balancing; you probably want the balancing kind.

each of those two kinds are further subdivided. some have a single charge/discharge port, and some have separate charge ports from the discharge port. if you use the latter type, you *must* charge thru the charge port *only*, or the bms cannot do it's job to protect the cells from overcharge.


the meters can only monitor and display voltages, sometimes balance cells very slowly.


rc chargers (which is probably what you use now) can act like a bms and a cell-level meter display and a balancer, but you either need three of them (one for each seriesed pack) to charge the packs while seriesed, or you have to do what you already do.

A BMS is at minimum LVC / HVC functionality, so by definition, No.

Only super expensive ones are designed to actually manage the charge process as part of their functions, and usually the slave charger is as well.

A balance charger is what you are thinking of, and there are hundreds that will do the job.

But parallel charging can be unsafe, get good fused protection boards.

rcgroups forum has the details

this is something you can use to charge your 3 packs at same time. As long as they are the same type 4s it will work and save you time. You only need one charger to charge all 3 packs.

fredfire said:

Does a BMS exists for charging only those batteries? Something I could plug all balance wires into and plug the series discharge lead to charge.

Click to expand...

https://www.ebay.com/itm/Li-ion-Lifepo4-Battery-Active-Equalizer-BMS-1-2A-Balance-4S-2S-8S-12V-16-8V-24V/113890432488

You would plug this into the balance leads, but charge through the main power cable.

just keep in mind it doesnt' have any kind of protection against overcharging cells, other than being able to shuffle charge from high ones to low ones at a higher rate than most of the cheap balancing bmses.


also note that since they are universal, they don't really have an lvc as such, so if you have a cell or group that has internal leakage, and that cell or group keeps dropping in voltage whenever charge current isn't flowing at a high enough rate (or at all), then these units will drain the rest of the pack trying to keep that leaky group full, down to 2v / cell.

so...don't leave them attached to the packs except during balancing.

They cannot be connected during use, not a BMS, they are chargers.

And can be used for bulk-only, no balance too..

Just limit the parallel charging to when it's required.

Doing one at a time is safer, more precise, that's when you keep an eye on their SoH.

There are also chargers that will do packs sequentially rather than simultaneously, and only through the balance leads once the first cell hits the target finish voltage.

But getting rare these days

What you need is your RC charger, and the paralleling board. Then you can parallel them to bulk charge or balance charge with your balancing charger.

Be careful about sequence of plugging it all in, you must disconnect all series connections before you start plugging in the balance wires to the board. Easy to do it wrong. I fried two parallel boards that way. :lol: :lol: :lol:

Or get a 12S RC charger like I mentioned above, that way he doesn't need to reconfigure between series and parallel.

But (and this is important) you should rarely need to balance. If your lipos need balancing more than once every few months you are probably discharging them too far or they're worn out or damaged.

Chargers over 10S are getting rarer and rarer, limits your options wrt value, features and build quality.

Better IMO to get a 6S or 8S and then a 10S if you're in a hurry, maximum future flexibility.

Connecting serially for use should be NBD

john61ct said:

They cannot be connected during use, not a BMS, they are chargers.

Click to expand...

these
https://www.ebay.com/itm/Li-ion-Lifepo4-Battery-Active-Equalizer-BMS-1-2A-Balance-4S-2S-8S-12V-16-8V-24V/113890432488
that were just being talked about right before your post, are not chargers, so they can be connected all the time.

but as i noted, there are good reasons for not doing so.

amberwolf said:

these https://www.ebay.com/itm/Li-ion-Lifepo4-Battery-Active-Equalizer-BMS-1-2A-Balance-4S-2S-8S-12V-16-8V-24V/113890432488
that were just being talked about right before your post, are not chargers, so they can be connected all the time

Click to expand...

Are you recommending these? Look very useful for midpoint or bottom balancing also.

Are you saying that each 4S sub-pack could each wear one while they are all connected together in a 12S string?

How about just one, connecting the balance leads of all three in parallel, while they are all still connected together in that 12S string?

I know we've mentioned these ideas before, but I never got a clear confirmation that the latter would work?

john61ct said:

Are you recommending these?

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did you even read my post in reply to the poster that linked them?

Thanks guys , I will get that balancer board with my actual rc charger it is exactly what I needed.

Maybe one day, I will buy a real bms but at that time I'd be better buying a real, secure and powerful brand new battery something like em3ev does.

amberwolf said:

john61ct said:

Are you recommending these?

Click to expand...

did you even read my post in reply to the poster that linked them?

Click to expand...

Yes, I meant independently of the OP use case, all the requirements for use fit my preferences just fine, just asking if build quality / reliability / accuracy is good or not?

Not a protective BMS, just a balancer. Not a problem so long as that is known, just use when a balancing session is the job at hand.

Of course monitoring that job to ensure all is well is required, perhaps with protective circuitry active as well if needed.

If anyone has / get experience using these, or similar, please report back.

Personally I like the idea of those where the higher balance rate is independent of the voltage delta. AKA "active" balancing, should be a faster result. 6A would be my limit personally. Power supply for the balancer would be an issue to test/verify.

But they tend to be a **lot** more expensive.

john61ct said:

Yes, I meant independently of the OP use case, all the requirements for use fit my preferences just fine, just asking if build quality / reliability / accuracy is good or not?

Click to expand...

that i don't know. i think there are threads with people actually using them around here somewhere, but i don't remember who.

personally, i doubt they are any better than a cheap bms or any of the rc type stuff, for those three qualities.