Charging small 12v powerwall

olafkr

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New to the forum so here goes.

I'm planning to make small 12v powerwall with 84 cells in total.

But there's my question: If i want to charge them without BMS or MPPT with solar panel what type of power supply should i use?
Should i use iMax B6 or other charger?
 
Rc chargers wont work well with solar panel as input.

Cheap bms and a chargecontroller is what i recomend

Ie there is no easy sollution to ur demand :)
 
You misunderstood me.

I want to charge my pack WITHOUT solar panel.
What BMS and charge controller should i buy? Will the cheap 3s 25A from ebay do the thing?


Sorry for stupid questions. I'm just a total newbie to powerwalls.
 
Yes, you can use the B6. I think it is limited to 50W and 6A though so you can calculate how long it will take to charge your battery.
 
olafkr said:
If i want to charge them without BMS or MPPT with solar panel what type of power supply should i use?

Here you specifically stated with solar panelbut withoutBMS or MPPT. So, Daromer replied based on that information. He did not misunderstand you, you misinformed us.
Unless you meant "MPPT with solar panel" as one phrase. In which point, is highly confusing with the way you asked.



Curious, what are you planning on running with such a small pack/voltage? I'm guessing you aren't using any kind of inverter as most will not work well with the 3s or 4s configurations.

Perhaps if you gave some more information we can make a better tailered response.
 
If you talk about normal charging from outlet or DC source normal RC charger all the way. I personally dont like the B6 unless you go with the real one. But then you can likewise pick a better charger for the same price :)

I just read your information and picked the best answer on that :)
 
I am talking about normal charging from outlet :)

I'm planning to make small 12v 3s84p pack with an inverter to get 220v in my dad's camper.

So what type of configuration should i use for e.g 600w 220V inverter?
 
it depends on the inverter you choose.
12V is very difficult to get an optimal setup with LiIon cells that has a nominal voltage of or around 3.7V. The reason is that its either to low or to high.

3s you dont get to use much untill the low voltage limit hits and 4s fully charged is way above 16V. Generally either go with a 7s aka 24V system that is more optimal or a 4s LiFePo4 system that have also more equal voltage to the 12V systems.

Also dont say you going to limit the system by using the lower voltage cut out on the inverter and use 3s system. Because that wont work very well. As soon as you power something up or hit a spike it will shut down :) And when you want to use all you cant if you have the limit :)
 
You should rather go for 7S36P and use a 24V inverter. Neither 3S nor 4S fits the classic 12V system very well and you can't have 3.5S obviously. But you can double it to 7S and that fits 24V nicely. For a 600W output your battery has to supply around 27A which is 750mA per cell. No problem for new cells, but if you want to use reclaimed laptop cells I would probably make the battery bigger to spread the current over more cells.
 
Okay,

So if i'll choose the 24v configuration, how am i supposed to charge it? :)

RC Chargers can output 20v at most.
 
No, that's not true. Most of them do at least 6S / 22.2V because that is the biggest type of battery commonly used in RC vehicles. And then there are quite a few that do 7S and 8S and the maximum is usually 10S. No problem at all to find a suitable charger for 7S.
 
Just go for an 8s charger for 7s system as Dark said. I personally use iCharger Duo 308 and 4010. 8s and 10s chargers.
 
You can't do 6S. Well, you can, but then you don't get a 24V battery ;)
Take a look at the Junsi iCharger 208B (runs on DC only) or SkyRC D400 (runs on AC and DC). Maybe one of these fit your budget?
 
DarkRaven said:
Take a look at the Junsi iCharger 208B (runs on DC only) or SkyRC D400 (runs on AC and DC). Maybe one of these fit your budget?

Unfortunately, it'll not. My budget for the charger is about 40-45$
Maybe there's a way to charge 7S using iMax or something cheaper? :)
 
You COULD try having 2 packs - a 3s and a 4s that both suit your current charger/s, then combine them for use as a 7s.

Not elegant, but practical...
 
You can have a 7s pack and just break out the connection and charge it as Grumplestiltskin said.
 
I'll think about that.
What's the cheapest 7s charger that won't blow up my house? :)

And what about the BMS that I linked? Will it do its job?
 
Not for a 7S battery, but there are 7S models out there as well. These cheap BMS boards are generally a bit doubtful though. With a balance charger you don't need a BMS to charge the battery. Only for automatic low voltage cutoff if you want something like that.
 
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