Adding mosfets to unpopulated pads on BMS???

Thread Starter

bigjoncoop

Joined Feb 1, 2019
83
I'm in the middle a building a large battery using 18650 cells. While saving money to afford a $500+ Batrium BMS I've been looking for some cheap BMS solutions for the time being. I have came across a few cheap BMS is and I've noticed a similarity between a lot of them. a lot of them have a lot more room for more mosfets then are currently installed. from what I can tell all the mosfets are in parallel. I've included a picture and was wondering if one could install as many mosfets as would fit and if doing so would raise the current capability the BMS.

I'm thinking that adding more mosfets would allow the BMS to handle more current as long as I beefed up the traces with extra solder or wire leading to the pads for the load and battery connections. and if you notice the required resistors or components are already installed next to the missing mosfets.

if doing so would not raise the current capability then would it have any other benefits?

61YVs1wMReL._SL1001_.jpg61YVs1wMReL._SL1001_.jpg
 

Sensacell

Joined Jun 19, 2012
2,567
Possible, but you are making a lot of assumptions.

Don't bother unless you understand exactly what is going on in the circuit.
 

jpanhalt

Joined Jan 18, 2008
9,113
That board looks like all 6 mosfets are in parallel. Each mosfet is rated at more than 50 A, and maximum Drain-Source voltage is 40 V. For continuous current, those 6 should be able to handle 20 A easily, if not, adding a heat sink will probably increase heat dissipation better than adding additional mosfets.

Here's a link to the datasheet for the mosfets: https://pdf1.alldatasheet.net/datasheet-pdf/package/1146249/HUAYI/HY1804B.html
 

Thread Starter

bigjoncoop

Joined Feb 1, 2019
83
That board looks like all 6 mosfets are in parallel. Each mosfet is rated at more than 50 A, and maximum Drain-Source voltage is 40 V. For continuous current, those 6 should be able to handle 20 A easily, if not, adding a heat sink will probably increase heat dissipation better than adding additional mosfets
Thank @jpanhalt ,
I'm pretty sure you're correct. those mosfets are in parallel. and if each one is rated at 50 amps, then surely that BMS is more than capable of handling higher current. and that BMS does come with an aluminum plate on top of it with thermal compound in between acting as a heat sink.

I think I will order a few of them since they're so cheap, remove the aluminum plate and add a beefy heatsink on top of the mosfets maybe with active Cooling. Ill thicken up the necessary traces by adding more solder, and solder on some thick wire capable of handling higher current going to the battery and to the load.

I don't see why this wouldn't work since there's nothing else on these sorts of BMS that should be affected by higher current draw. the battery is connected to one side of the mosfet and the load to the other so as long as the mosfets and the traces are able to carry the current and I can keep them cool enough.

the BMS's will be here in a couple days I'll give it a shot and keep you posted.
 
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