Alright guys. This is all hypothetical…
I have a 20s battery. I can charge it with my 72v charger.
If I have another 20s battery and connect them in series, that’s a 40s…and another…and another…and another…100s. Right?
How would I charge it without having to disconnect them, plug them all individually onto my 20s charger, then reconnect them. I’m sure there’s a way to do it while they’re all connected.
wire another 4 20s chargers in series? or find a 100s charger?
Are these a bunch of different batteries connected in series for charging like 5 esk8s? That would be bad because they wouldn’t be decently balanced .
If you want to charge 5 batteries from one charger you can put them in parallel but they need to be at the same voltage when you connect them. However they don’t need to be the same capacity you can charge a 1Ah battery with a 50Ah battery just fine.
If you have a high voltage battery what you can do is put a switch or loopkey between some of the groups, you can do this and charge it on 5 20S chargers but connecting them in parallel a load of times is less than ideal.
For a series connection, you would need a BMS circuit, because the batteries could get unbalanced, with one having a higher voltage than another one, which can be very dangerous. And you’d far be better off starting with them balanced (all the same voltage) which generally means charging them individually first, defeating the purpose.
For a parallel connection, there are also serious problems. They need to be balanced (at the same voltage) when the parallel connection is made, or it can be very dangerous. The easiest way to do this is to charge them all (one at a time) on the same charger immediately prior. And then, once they are connected together, they would need to STAY connected together. You can’t practically disconnect them from each other and use them separately, then connect them back together again to charge, mostly because you need to charge them all individually prior to connecting them together again. It can technically be done, but there are a lot of gotchas and huge safety risks that make it impractical in nearly all cases.
You could technically discharge to balance them, but then you would need a device to do this, time to do it, and you will be increasing the wear and age of the batteries unnecessarily. And again, it would need to be done individually prior to connecting them together, which, again, mostly defeats the purpose of connecting them together.
The better options would be to use the five 20S batteries individually, also charging individually
–OR–
make one 100S battery, with a 100S BMS, and a 100S charger, that doesn’t come apart.
This can be very dangerous; do not do this.
You would need a 20S BMS and to connect/disconnect 21 different wires for EACH section when you charge, and you would ALSO need a 100S BMS (101 wires) and also to not run anything bypassed. So your ESC would need to discharge through the 100S BMS.
There are a lot of gotchas here that make it completely impractical to do safely.
It’s either really hypothetical or far from normal (esk8) circumstances so I’m missing some context like I thought Bugabeetle could be talking about connecting/disconnecting 5 packs each charge cycle.
You wouldn’t need to disconnect/reconnect any balance leads necessarily, I’m not sure where I went wrong explaining that. You could have 5 separate packs connected through loop keys or switches with a dc input and a bms for charging like normal, disconnect the packs from each other to not create a short through the mains, and charge it on 5 chargers or put them in parallel but again that I don’t recommend. A (Im too tired to figure out if it’s 6 or 10) pin plug and electronic switches for example could make it take no longer to start than normal charging. Either way why would you need both a 100S bms and 5 20S ones?
Idk why someone wouldn’t use a higher voltage power supply, the scenario doesn’t make sense to me in the first place my understanding of the question is limited but I can lend a little help. Like I caught multiple people (14yo me included) going to wire one pack in two configurations at once and the only way to do it is to disconnect part of one. Which here is just a reminder you can’t charge multiple batteries connected in series from a power supply each, connected to the mains in parallel. Hopefully I’m making at least a little sense.
I’m using the same concept charging my 12S10P. It’s 2 smart chargers charging 6S 10P at up to 21A each from one power supply, slightly like the race boards with LiPos.
Ps feel free to ask me to explain something if it’s not making sense it’s probably on me
Charging them all at once in series with something like this maybe is simplest and safest
a 400+ volt power supply is expensive these seem a possible substitute
Maybe would take too long to charge with these but surely a higher power booster can be found
https://www.amazon.com/Rakstore-Voltage-5V-400V-Converter-Adjustable/dp/B09LD9RTS9/ref=mp_s_a_1_25?crid=323IP4HMZT2SQ&dib=eyJ2IjoiMSJ9.M-vS3Djg2FFGCXuTku6TcZSv5OnEu3W3h-CujehOQzjVOaYOFuIlwRcaocZbf6vunYNbY3i9fc02w-AQ7XJB7s8EUDp1BVzh6Ppx9tj1REdDEolaQHfcdXVmgZ06UqOmi_dSRFZ_FkwesuvDd9d2LKMQSJwJbO8a7z9yigOPg5rkbBt_AJ8ne1glLYm5uIO3b0ki_2kTDf2IuefudkU6Kw.iX7w8VaHWoAFc8e4HfjhEon5xi4QxGh4bJJWFbrI-lc&dib_tag=se&keywords=dc+to+dc+converter+high+voltage+400&qid=1735236556&sprefix=dc+to+dc+converter+high+voltage+400%2Caps%2C275&sr=8-25
I don’t know about other parts of the world, but here above 100VDC or 50VAC is considered “standard low voltage” and applicable to regulation.
400VDC is a lot. Unlike getting a shock form AC voltage, DC doesn’t cross zero so muscles can’t release if grabbing something while getting shocked.
What’s your experience, qualifications, and intentions by constructing a 100S battery?
None of those suggestions are safe, because none of them shut off charging if cells are out of balance. This is how you burn down buildings.
??
The “dangerous unsafe one” could.
I’m assuming the imaginary scenario has a bms on all the batteries. You are assuming they don’t.
Even if the batteries all have individual BMSs, if you connect them in series, then it’s not enough. You would need an additional BMS for the entire new battery. Series connections can’t just be done that way safely.
So you left out that part about buying and connecting a custom BMS for fire prevention, and only included the cheap voltage boost converters which are dangerous to use alone.
What are the risks? I assume the bms on each of the 5 batteries would protect as usual and not allow anything over 4.2 regardless of what voltage is applied to the 5 in series. Maybe the 5 could have different voltages or resistance from each other but still the bms would assure nothing gets over 4.2.