Super Cheap BMS for Solar Charging Bank

[Nikg736]

I'm looking to build a few small projects with 18650 cells. Looking at 3s-6s and nothing more than 4p-8p with 1600mah cells.
Anybody ever used these type of super-cheap BMS units?

3S BMS
6S BMS

One project I have in mind would be a "backpack battery" for a leaf blower. I have a 20v (5s) 4ah battery for it that died, so I was going to use the connector from that battery to plug into the machine and create a larger 24v (6s) battery of 4p or 8p. A bit more voltage and a whole lot more capacity. Would probably try charging with a 6s RC lipo balance charger but wondering if I would even need a BMS in that case?

 

[sunshine_eggo]

No, but I would hesitate to use a BMS with a high cut-off of 4.25-4.35V

 

[Nikg736]

Let me make sure I have the job of the BMS correct. They are meant to prevent over-charging and over-discharging at the cell level, right? And an additional feature that some may have is balancing at the cell level. So tool batteries have a built-in BMS in the battery itself I'm assuming. To charge my backpack battery, I guess I wouldn't need a BMS if using an RC type charger because the charger would monitor and balance charge. So if a crappy BMS had high cutoff of 4.25-4.35 then that wouldn't really matter with my charging method as the cutoff would rely more on the charger. I guess what would matter more is the low cutoff making sure the cells didn't go too low and cause damage/death. Right?

 

[sunshine_eggo]

Let me make sure I have the job of the BMS correct. They are meant to prevent over-charging and over-discharging at the cell level, right? And an additional feature that some may have is balancing at the cell level. So tool batteries have a built-in BMS in the battery itself I'm assuming. To charge my backpack battery, I guess I wouldn't need a BMS if using an RC type charger because the charger would monitor and balance charge. So if a crappy BMS had high cutoff of 4.25-4.35 then that wouldn't really matter with my charging method as the cutoff would rely more on the charger. I guess what would matter more is the low cutoff making sure the cells didn't go too low and cause damage/death. Right?

Sorry. I see it now, but I missed that you planned to use a balance charger. If you're using an RC type charger with balance charging, then I would be far less concerned about that BMS.

 

[Nikg736]

OK, so in that case I guess really all the BMS would be responsible for is low voltage cutoff to prevent over-discharge. I'm assuming hopefully it can handle that duty just fine