Leaf build question.

[ynot]

To build a pack for 36 or 72 volt use, for golf cart or ebike, is it best to build series packs, then parallel connect, or is it best to build parallel groups then series connect the groups?

Lets say a pack of 10 in series, with 2 groups wired in parallel or a pack of 2 parallel wired into a10 cell group in series for the 72 volt freighter bike.
AND

Lets say a pack of 5 in series with 4 groups in parallel or packs of 4 parallel wired in series for the 36 volt golf cart (read tractor using a golf cart motor).

 

[DG98]

I have a 14s14p battery pack that I made out of 98 first-gen Leaf modules. (Two complete cars' worth, plus a couple spares.) I can't say which method is "best," but I built mine out by paralleling the modules and then connecting those groups serially for one simple reason -- it only requires one BMS that way.

For example, if I had built fourteen individual 14s1p packs and connected those fourteen packs in parallel, I would need to deal with battery management for fourteen individual 14s packs. Instead, with 14s14p, I have a single 14s BMS system from Batrium keeping the entire pack balanced. (Yes, the initial balance took a long time -- think several days -- because of the overall capacity of the battery, but keeping it in balance since then has been a piece of cake.)

Cheers, John

 

[ynot]

Thank you John,
For the tractor am going to go either 4 or 5 series packs with 3 or 4 parallel modules in each.
Doing a little research to see if my 36Volt Curtis controller will handle 40 volts if I go with 5S.
Really welcome the input, have quite a bit to learn.
Tony.

 

[GoneDiving]

If you link parallel cells first then series them you will need very large busbars because there is only one busbar after each parallel group and these take all the output current.

If you build series packs first, then link them, each series string shares the load. Each string then only supplies the total current divided by the number of strings.

One BMS can be used if busbars of the same voltage are linked with balance wires. Note that these are only balance wires so can be light guage. They only take the current to balance the cells between the series strings (if any). They don't take the output current.

 

[floydR]

Doing a little research to see if my 36Volt Curtis controller will handle 40 volts if I go with 5S

Many motor controllers are dual range 24/36 36/48 should say on the unit itself if not then on
https://cdn.curtisinstruments.com/products/datasheets/MSeries_datasheet_en.pdf maybe you have one That is listed in the chart.
later floyd
ps there is an old style 36v series golf cart motor on ebay. https://www.ebay.com/itm/303782182991

 

[ynot]

Thank you Gone Diving, partly because of the possible layout in the battery box, will probably go with 2 5s packs and parallel them, Your tip about using one BMS and linking the matching modules is great, had been wondering if that would work.

Thank you again Floyd, yesterday put a test pack of 5 leaf modules into the tractor and the controller seemed to like it.
The new 24/36 volt motor would hardly run on the 4s golf cart batteries but lit right up basking in the 40 volts of the new pack.
Recommendations for a BMS & charger would be welcome, also now need a buck converter to give me 12 volts for the winch. Thinking that a small 20 amp buck, charging a 2s leaf or 12v LA battery would be a good way to go, small buck with lots of amps for the winch. space and weight not a problem but even Bill Gates has to manage his cash flow.
Cheers
Ynot.