chasthanhburns
10 mW
Can i charge my 48v battery with a 24v charger by only charging half the battery allowing the bms to balance the two sides?
Last edited:
Charging 48v battery with 24 volt charger li-ion??????????
- Thread starter chasthanhburns
- Start date
chasthanhburns
10 mW
doe
Does it matter that i meant charge a 48v with a 24 volt charger?
docw009
10 MW
I assume this is an Li-ion, not LiFePO4 pack. Regardless of the cell type, anytime you connect a charging source directly to the cells, you bypass the BMS which is a safety risk. Balance is the least of your concerns. There is no overcharge protection, which makes this a bad idea.
In addition, a 48V Li-ion pack is built with 13 series groups which total 54.6V. It cannot be divided in half evenly, so the 7th group in the middle is a problem. You need a 29.4V charger to do the first seven groups, and a 25.2V charger to do the last six, and you still have the overcharge risk.
I believe the LiFePO4 packs are 16 series groups, so they could be charged 8 groups at a time, but there is still the overcharge risk with the BMS bypassed.
In addition, a 48V Li-ion pack is built with 13 series groups which total 54.6V. It cannot be divided in half evenly, so the 7th group in the middle is a problem. You need a 29.4V charger to do the first seven groups, and a 25.2V charger to do the last six, and you still have the overcharge risk.
I believe the LiFePO4 packs are 16 series groups, so they could be charged 8 groups at a time, but there is still the overcharge risk with the BMS bypassed.
If it's a lead battery meaning four 12 volt batteries put together in series to make 48 volts. Then you can charge two of them at one time with your 24 volt charger always watching not to let anything overcharge beyond 14 volts each 12 volt battery.
Hard to answer your question ( a battery )
Could be 12s could be 13s both have been sold as 48 volt. Which would have different final state of charge.
You're making us guess about a lot of info ??????????
Hard to answer your question ( a battery )
Could be 12s could be 13s both have been sold as 48 volt. Which would have different final state of charge.
You're making us guess about a lot of info ??????????
I think you need to clarify what you mean by charging with a 24v charger. One read is that you’re plugging in a 24v charger into the 48v battery charge port. The other is that you are opening the battery and connecting half the parallel groups at a time, but since a 48v pack is 13 groups in series, there’s no way to isolate “half” the pack. A 24v pack has 8 parallel groups in series.
If your idea is to go through the charge port, the charger will never turn on, since the depleted 48v pack will still be above the 33.6v charger output.
The partial pack method won’t work either.
As far as the BMS goes, most are passive balancing, draining down the high cells to match the low ones. An active one would drain the high into the low, but that would take forever (if you charged 8 groups and expect the BMS to balance up the other 5 groups).
docw009
10 MW
You're not wrong at all. With lithium, you really have to do things by the book.
offGridDownUnder
10 kW
Not at all. Death is just Nature's way of telling us to slow down.
gromike
10 kW
You can charge your 48v battery with a proper 24v charger by splitting your pack electrically in two (as far as charging is concerned.) No bms, so be careful.
The amount of time and effort to do it makes the price of a 48v charger quite the bargain.
The amount of time and effort to do it makes the price of a 48v charger quite the bargain.
Sadly 24v = 8S and 48v is 13S, there’s no way to split the pack. The OP should not do anything until he gets the correct charger. From a safety perspective, the original question should set off enough alarm bells to avoid suggesting otherwise. He’s certainly not in a position to safely implement any creative solutions. With a lot of work and what he has to work with, the pack could be fully disassemble to the cell level, built into two 8S packs and run them in series at 16S/60V with a few cells left over. But he lacks the knowledge, and likely the tools, to do that safely.
chasthanhburns
10 mW
Oh no. Wish I had rad this reply earlier. My house is burning down. Wait thats just my joint.
chasthanhburns
10 mW
Already tried it today. I completely disconnected my bms as i was not sure it would balance out the battery pack. I am just charging one bank then the other bank. Just needed to solder on one wire. I probably should just buy the charger but I am hard headed, i like to learn by experimenting, and aint got no money. I also aint sure of what the finish line is or what I am trying to build. It is actually a 72v battery i built. The 48v question was just because i thought it would be more relatable to those that read this. I also got a 96v controller and a108v controller I may want to use but i can not find a way to activate the abs on them and these bikes i am using are really garbage with really garbage brakes and rust and just dangerous flimsy metal. I got it up to 41 mph today when i tested it to drain the battery. 2100watts at peak with 31 amps peak. Only got 11.5 miles before the 62v cut off i set in the BMS. It almost seemed fast enough to keep up with traffic but also was scary on this crap bike. Sorta hopping for 55mph but agian the 96v controller has no abs and it was fairly scary at 41mph.
chasthanhburns
10 mW
I used 48v as an example cuz i thought it would be more relatable to the reader but you are right. It is a li ion battery but my actual battery is a 72v battery. so 20s. I did do it. It does work. I disconnect the bms and the bike before charging the packs one at a time. I plan to check that voltages are really close before connecting them back to the bike and bms. I should just buy a charger but I bought all this stuff when Trump was handing out money. I aint got no money under bidden so gotta do what i gotta do.
chasthanhburns
10 mW
I should just buy a charger but I bought all this stuff when Trump was handing out money. I aint got no money under bidden so gotta do what i gotta do. Safety aint a big concern when riding something like this. No front brakes at all, front wheel i jammed in so tight that the front shocks are bond up and do notwork, no gears at all, and rust and zip ties holding it together.
chuyskywalker
10 kW
I mean....so, it's a STRONGLY bad idea, but, yeah, actually you can charge a 48v battery with a 24v charger. You, though, would have to charge each half of the pack, one side at a time.
On a smaller scale I have, in the past, charged a specific parallel group of cells that was WAY out of balance in a pack (because I was lazy when I built it from previously used cells) by just stealing the BMS lead and plugging into those pins for the right parallel group and using a bench power supply set to 4.2v/1a.
There are a LOT of challenges and pitfalls (potentially fire tastic) to doing this, but it is possible.
On a smaller scale I have, in the past, charged a specific parallel group of cells that was WAY out of balance in a pack (because I was lazy when I built it from previously used cells) by just stealing the BMS lead and plugging into those pins for the right parallel group and using a bench power supply set to 4.2v/1a.
There are a LOT of challenges and pitfalls (potentially fire tastic) to doing this, but it is possible.
You could do that with a 52V battery (14S), but not a 48V (13S), using a 24V (7S) charger (I misspoke earlier, 24V is 7S not 8S).
Anyway, it's up to 20S now, so the 48V example was just a cannabis induced example I guess.
chuyskywalker
10 kW
Yeah, ooops. I mean, I guess you still could, but...now it's an even worse idea.
chasthanhburns
10 mW
Tried that. Cannabis caused me to plug the first in backwards now I am down to one charger. E-HP was right. I should just buy a proper charger.
If you make a rule of no cannabis while charging, you’ll suddenly have the incentive to buy high quality, fast charging batteries. Better batteries, safer charging. Turn it into a win win
