JBD 24v 100A BMS sent with 8 awg cable

[ShaneC]

Hi,

I have just received the JBD SP22S003B BMS for my 24v 280Ah battery pack. On the website it is shown with 2x8 awg cables in parallel for both the B- and C- connections however on arrival it has just one. I am concerned that the single 8 awg just can't handle the 100A current and even if it could would lead to power loss through resistance.

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I have tried to contact JBD but they are on holiday until the 30th due to the Chinese sprint festival.

Am I right in saying that this is inadequate for the 100A load? Should I try to desolder the existing 8 awg cable and connect 4 awg instead?

Tempted to ask for a refund, atleast a partial one to cover the hassle and cost of cable. Here is what I received:

 

[MisterSandals]

I am concerned that the single 8 awg just can't handle the 100A current and even if it could would lead to power loss through resistance.

If you are getting power loss it would be in the form of heat. You could easily fell the wire if it were hot. Easy to test.

Keeping these wires short will help.

 

[SeaGal]

Interesting.. my overkill 48v 100A one came with two 8awg and they get slightly warm at 65A draw...

But your cable looks thicker in the pic - have you measured it? i.e. are you sure they haven't put a single bigger cable in there?

 

[ShaneC]

Interesting.. my overkill 48v 100A one came with two 8awg and they get slightly warm at 65A draw...

But your cable looks thicker in the pic - have you measured it? i.e. are you sure they haven't put a single bigger cable in there?

It's definitely 8 awg, it's written on the cable and is the same size when compared to my other 8 awg cable.

 

[740GLE]

They prob just used a larger insulator to deal with the higher temps.

If it were me I’d be looking to double up 8awg or try and get 4awg on there and keep the leads as short as possible.

Side note: If you are designing a 24v system for a constant 100a load, you picked the wrong BMS. IMO the BMS should be rated for 2x constant load, this allows for spikes without causing issues. If your system runs regular consistent 50a and only occasionally hits 100a then 8awg maybe fine for those peaks, heat and voltage drop may not be that bad.

 

[ShaneC]

They prob just used a larger insulator to deal with the higher temps.

If it were me I’d be looking to double up 8awg or try and get 4awg on there and keep the leads as short as possible.

Side note: If you are designing a 24v system for a constant 100a load, you picked the wrong BMS. IMO the BMS should be rated for 2x constant load, this allows for spikes without causing issues. If your system runs regular consistent 50a and only occasionally hits 100a then 8awg maybe fine for those peaks, heat and voltage drop may not be that bad.

The plan is not to have 100a continuous, but I would like the cables rated for it. The BMS doesn't cut off til 120A for 30s so it's capable of supplying more than my inverter will pull (2kw Giandel). Given that this is just going to be used for my office equipment it will usually be 20-40A but I want the headroom for further usage on top of that (another PC for example).

So you're right that the 8awg would do for my use-case but I just want the cables capable of dealing with what the BMS can supply. It's annoying that it's mis-sold on their website as having 2x8awg cables. I won't be able to fit a 4 awg lug on there but plan to try desoldering what's there and fitting 2x8awg lugs, might be a bit tricky with the layout of the board but I'll see what I can do.

 

[Quattrohead]

What you thought you were buying and what you actually received appear to be a rather different. I would have a word with them if I were you before going any further.

 

[ShaneC]

What you thought you were buying and what you actually received appear to be a rather different. I would have a word with them if I were you before going any further.

Apart from the cables it seems pretty much what's in the photos on their shop. Still a 100A BMS just without the cables rated to 100A.