kfong said:
I hadn't tried just using metal rings. That's a cheap solution. Ferrite is suppose to have better properties but as long as you get results. The original design by Neodymics had a 300uh inductor. Since I don't have an inductance meter. I just wound as much as I could. As long as it works for you. You can have more inductance, just as long as you meet the 300uh minimum. Its sole purpose is to reduce the spikes going back to the batteries, so if the BMS doesn’t shut down then you’re good to go. The only other time it shuts down is when you draw too much current. You will get a pulsating effect. This is different from the spike shutdown.
I tried re-winding with 2 and then 3 rings but it wasn't happening.
My final wind is 8' of #14 wire around 4 rings. Put a bead of hot-melt glue between each ring, set the stack on a level surface, hit it with a heat gun to get the rings settled into close contact, and then wound it - dabbing a little more hot-melt on the first and last windings just to keep it easy to handle.
Probably some overkill, but not *that*much.
Seems to be 100% reliable.
Does anybody know if there is any value in how close the rings are? Or is it just the total mass plus the length of the wire?
View attachment DSC_3196.JPG
Once the crimper arrives, I will trim the leads - maybe even solder one end directly into a board.
After a few shallow discharges/charges, I ran one of the batteries flat -riding up and down one of the hills that lead to our house.
Per the CA: 2.165 AH and 65 Watt Hours. That's at 38 degrees F, but with the battery coming from inside the house - so I doubt it had time to get really chilled.
[(79 nominal- 65 actual) / 79] ==> 18% reduction in capacity... which seems to agree with what I've read about temp/capacity
I've got the CA's amp limit set at 12. That pulls 15 amps momentarily but limits it to twelve 99% of the time. That's about 420-440 watts. 400 watts is just fine for what I want to do and I can live with 350... so the rig as it is now seems like a pretty good fit.
Losing 10+ pounds of battery *really* improves the bike's ride/handling.
Tonite I'm leaving the other DeWalt in the garage where it will chill to near-outside temp and we'll see how the capacity holds up.
EDIT:
Next day, I got 61 watt hours: (61/79) ==> 77% nominal capacity. Temps in the mid forties.