Re: [electricboats] Splitting 48V System Into Two Boxes?

The leads you should really worry about being long are the high current wires.  If they're just sense wires, then they draw minimal current so don't worry about that length so much...within reason naturally. Noise pickup could theoretically be an issue at extremely long lengths.  That's why shielding is good for those.  Matching is generally no big deal except for the individual pairs.  Those pairs should be matched...and _twisted_ pairs.

However, the charging leads _do_ qualify as high current if you're charging at 250A, so there's that.  Even still, you really want them _shorter_ rather than matched.

Also, the LOOP AREA of the high current wires are a BIG DEAL.  Plus and minus should be next to each other and (ideally) also twisted for best results.  Twisting lengthens them slightly but you'll be generating a magnetic field relative to the amount of current.  The bigger the loop area the bigger the radiated field.  Twisting radiates it in such a way as to cancel with each successive twist.  Your compass probably will like that better.

Fair winds and following seas!

Dave

On Wednesday, May 3, 2023 at 04:54:20 AM CDT, aasmith970@gmail.com <aasmith970@gmail.com> wrote:

I have a question about the feasibility of splitting up my 280 amp hour 48 V system into two aluminum battery boxes, that I will be custom making making. I am constrained on the space in my Newport 28 sailboat and it would be much easier and balance the way much better if I split the bank.. 

I am concerned, or the question is will the leads being longer from one system to the next, and the BMS leads being different links affect the current/reading of the BMS?? The leads going between the two boxes would be made out of double00 welding cable with properly crimped terminals while the leads going between the individual cells in the boxes will be copper busbars. 

Should all the BMS leads be the exact same length or can eight of them be 2 to 3 times as long as the other eight the boxes will be about 30 inches apart?

280ah new cells from Docan
250 amp BMS Daly
Delta Q charger + 150 watts solar
7.5 KW system from Foshan Green Motor 

thanks for any and all comments. 

Aaron