Building new pack, cells from new supplier good!

[wheelchairer]

I have some room in this build to make spaces between battery cells. Is it worth maximising the spaces for cooling of the battery cells, or does it not matter?

[shirley_hkg]

Won't be necessary.

Better insulation is preferable.

[wheelchairer]

Well maybe. I didnt look it up I just looked at some cables in my charge box. I did use .7 mm2 on my long extension charge cable though. Those are silicone so externally thicker insulation. As well as on the chair side. Fit the pins fine. But I am using the large SubD connectors.

2 smaller black and red bags are the .7 sqmm (silicone) and the Revolectrix balance wire at the top and middle are marked as 22swg which is a fraction smaller conductor.

The charge cables are marked 12swg - same as stock revolectrix and silicone. They get just SLIGHTLY warm to the touch at 40A. Not sure what the mm2 is.

On balancing its not really about the current carry capability but the fact that when a 3A "brake" is applied or less than this when almost balanced, the resistance makes the voltage seem correct when its not yet. We are talking about a couple of mV difference here as thats the balance target accuracy. So long thin balance wires mean that it keeps applying a load to a high cell then releases it before it should. Then it tries again. So balance ends up taking much longer. Ideally balance wires should be as low resistance as possible. Below 300mm is recommended by most charger makers. Of course if the cables have bigger cross section longer is also fine. If you only uses the stock 22swg and made them 10 feet long final balance would take a long time.

So just to clarify from what you have said, those official PL 8 balance cables are three-foot long, and the cables attached to the battery pack have to be at least another 2 foot those so your balance cable there must have been at least 5 foot long?

And is it still possible to get hold of those balance cable extensions you have there in your picture in the 12 inch long version?

[LROBBINS]

Check with Shirley - he's been able to get balance cables and extensions.

[Burgerman]

I bought a dozen 36 inch ones. You use 2 on a powerchair. But I use these things to charge lots of hobby stuff. And so far I got through half of them.

[wheelchairer]

I bought a dozen 36 inch ones. You use 2 on a powerchair. But I use these things to charge lots of hobby stuff. And so far I got through half of them.

yes but what I am asking is this;
your 36 inch cable, is 36 inches long, 3 feet. The 36 inch cable connects to a D-sub, and from the D sub to the terminals has to be at least another two or 3 feet, let's say 3 feet. This means in total the balance cables that are balancing the pack in your wheelchair are 36+36 inches long, which is a total of 6 feet, yes?

[LROBBINS]

You don't need to use a PL8 cable from the D-sub to the cells. Any wires of the right gauge with ring terminals at the battery end are what's needed.

[Burgerman]

yes but what I am asking is this;
your 36 inch cable, is 36 inches long, 3 feet. The 36 inch cable connects to a D-sub, and from the D sub to the terminals has to be at least another two or 3 feet, let's say 3 feet. This means in total the balance cables that are balancing the pack in your wheelchair are 36+36 inches long, which is a total of 6 feet, yes?

Well about 4 foot 6 inches. Yes. It still achieves balance. Probably adds about 15 or 20 minutes longer than a 12 inch cable.

[dixonm]

I used tinned copper wires to reduce the likelihood of galvanic corrosion. You can learn more about galvanic corrosion at https://en.wikipedia.org/wiki/Galvanic_corrosion.

For balancing wires, I used wires obtained from Revolectrix. Those are 22 AWG tinned copper with the proper connectors. Though Revolectrix is no longer in business, you can find similar wires in many places, including Amazon.

I used 10 AWG wire for the power leads and I used 6 AWG to connect the individual cells together.

You can see my complete list of items in the attached spreadsheet:

LiFePO4 Build Parts list.xls

Steve

I looked at your spreadsheet earlier today and I ordered the Fishpaper from Digikey you list as separator with headway cells. I wanted to let everyone know that they have discontinued it and it will be unavailable once there stock is depleted.

Michael

[ex-Gooserider]

If you use the orange plastic 'building blocks' w/ the cylindrical Headway cells, you shouldn't need insulation between cells as the blocks space them apart...

Digikey is not the only source for fishpaper, and there are LOTS of other materials that can be used instead so useful to know, but doesn't make things that much harder...

ex-Gooserider