Battery layout.

[Blunderbuss]

HER !!! I don't think Kirstin want's to be a HER or a HESHE.
He dear boy, He.

No offence mean't a mistake, for which i apologise - but i am no boy either!

 

[Nealh]

I have done a quick mock up and looking at the layout the nickel strips will be a different length - is that bad thing?;

a to g and c to e = 45mm
b to h and d to f = 30mm

If so as another option could i not use a bit of nickel sheet/foil that would cover the whole of the eight batteries in each S, like what KirstinS shows in her post (https://www.pedelecs.co.uk/forum/threads/hear-shrink-large-for-whole-packs.33604/) the holes/gaps look like they are just to align the nickel but it covers all 8 ends.

Differing length of buss will mean the longer ones will/ may get a bit warmer and power share per cell will different, the two cells with shorter nickel will deliver slightly more ampacity then the other pair due to the fact the flow to the center is shorter. You can use one piece of nickel to cover any eight cells in series but will still need to ensure ampacity flow is enough, the nickel covering all eight will ensure equal flow but you will still need the copper link for current flow. A piece of 0.15mm x 30mm nickel to cover the cells will good for 20a optimal or 30a acceptable with 10a cells you will still need the copper or use a couple of awg 16 or 18 wires soldered like so to aid current flow like so.

 

[Nealh]

No offence mean't a mistake, for which i apologise - but i am no boy either!

!!!

 

[anotherkiwi]

I've been thinking about this a lot

Battery 5P12S, controller peak 17 Amps, cell 15 Amp continuous output.

Each series bus will be required to provide 3.4 Amps (5 x 3.4 = 17 Amps + a bit for losses), any 0.15 mm nickel strip can handle that. Electricity like water seeks the easiest path to flow, my modified version of the scheme is hence like this:

(please imagine 5P and the strips nicely trimmed at the end and folded over the top )

So I will have 4 x series busses carrying 3.4 Amps (0.23C) and 2 x exterior series busses carrying 1.7 Amps. The nickel strip is spot welded by 4 points, each spot weld carries 3.4 Amps/4 = 0.85 Amps.

At the end of the battery pack we have the problem area where we reunite all the series strings and so find ourselves with 17 Amps current, a copper strip soldered across the ends of all the series strings is used to handle the higher current.

I think copper is justified for a hot rod motor drawing regularly over 30-35 Amps, mine will be more often at <8.5 Amps than at 17 Amps.

Is my reasoning correct?

 

[Nealh]

From browsing many pages on ES the concensus is the best layout is a uniform block one with even number cells in parallel for best conductivity between cells.

For odd #cells like 5p you are best probably sticking to conventional series connection with one on each cell or for better uniformity use a single piece nickel plate covering all 10 cells in each series group.

 

[wheeliepete]

a copper strip soldered across the ends of all the series strings is used to handle the higher current.

Or solder your main power wire to each series connection, but using a copper strip is prob. neater and keeps the pack flatter.

 

[Nealh]

With a copper parallel buss on the first & last group it is still appears best not to have the discharge wiring on the last cell but nearer the middle or a pair of wires culminating in to one.

 

[anotherkiwi]

From browsing many pages on ES the concensus is the best layout is a uniform block one with even number cells in parallel for best conductivity between cells.

For odd #cells like 5p you are best probably sticking to conventional series connection with one on each cell or for better uniformity use a single piece nickel plate covering all 10 cells in each series group.

6P then, I can't see the logic behind that choice however. 0.2C peak will be very kind to the battery however. Like I said ES is often pushing things to the extreme limits.

 

[wheeliepete]

I'm liking this "fine tuning" of battery construction thing, but like you say AK, some of it is prob. unnecessary for low power application, but all good stuff to learn.