BLDC Battery Min (Regen) - is this correct?

I am trying to work out my correct battery min.

I have 2x 4s1p 20c 5000mah in series, to make an 8s battery.

Spec: Configuration: 4S1P / 14.8v / 4Cell Constant Discharge: 20C Peak Discharge (20sec): 30C Max Charge Rate: 5c

So I have 8S1P correct, does this mean I can charge at 5c or 10c?

So lets say I can charge at 5C, should I set my Bat min regen to -5A, or is that 5C x 5A = -25C?

You are running your batteries in series so the 5000mah remains as the capacity with all the same limits. I would try around 2c first, so -10 to -12. If you are running dual then you need to use -5 to -6 for each vesc and go up from there if needed. This affects the brakes at higher speeds so test it and be cautious at first. Try it on flat ground. The recharge part will be fine, to me it’s more about brakes.

Be safe and report back.

Your max charge rate is still 5C (25A in your case), I would say you can set bat min regen up to to -20A. I have battery with max charge rate of 50A and my batt min regen is set to -40A (-20A on both vescs). Regenerative braking is not continious and probably you even won’t reach the set limit in reality.

Thanks guys for you input, think I understand a bit more now. Just been out for a ride and set it to BLDC watt mode with settings:

Motor max: 60A Motor min: -50A Max battery: 50A Min battery: -30A

Braking seems nice and responsive, although my belt was slipping quite a bit so might of been a bit harsh. Do you think these settings are safe for my battery setup. Running a 8s 270kv 60mm motor with focbox.

Looks fine but I would not exceed -25A bat min. Belt skipping is annoying, I know :wink:, you could set the motor min to -30A or -40A. Which belt width do you use?

Try adjusting tension of the belt, looser or tighter. It’s a matter of trying few possibilities until belt doesn’t skip. You will eventually find correct tension. Also new vesc tool has breaking curve adjustment. I have used it to have breaks lighter an the begging and then stronger towards end of the throttle ( when pushed towards the end of reach). Now breaks work better, slight press of the throttle doesn’t lock the wheel any more. It does lock the wheel when applied at full force but that’s how it will work.

Yeah very annoying, mostly worried about wearing out the belt too quickly, just made some adjustments and seems to be good again. I think its just because I need some decent bolts to lock the motor down rather than little screws that are hard to get tight enough.

@rich belt is 15mm

15mm is good. The best solution is an idler pulley (on the slack line) if you have enough space on your motor mount. The problem is, when you have too much belt tension, you could harm the bearings (wheel+motor). On my longboard I had 9mm belt and awful skipping so I tried it with a lot of tension but had to change the bearings of the driving wheel every week. Now I have a dual motor build with 15mm belts (not tight) and on hard brake there is still sometimes skipping.

Also check your pulleys, in my case it was a bad quality motor pulley, too. Look at this, compared to a proper one :joy:

The right combination will lock down every screw and pulley forever unless you use a torch :wink:

I have some fully eroded windings on my torqueboards hub motors. Do I have a chance of getting the bolts to hold again with any of these?

If you clean down to bare metal, use primer, yes Loctite product catalog, a solution to any problem :grin: http://hybris.cms.henkel.com/medias/sys_master/catalogsync/catalogsync/9030422331422.pdf

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Cool thanks, I guess I can go for high strength? What is the primer for, to build the new winding surface? So I clean to bare metal first, insert primer, then the bolt to create the new winding, then loctite to keep it all in place? Sorry if this doesn’t make sense.

That catalog has step by step guides, it depends on what you’re using when/how it’s applied.

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Do you mean the thread on the bolt is worn out?

No the bolts are fine, it’s windings that are worn out. Two out of eight on the motor casing. So the bolts don’t hold anymore.

Getting that clean is gonna be a p.i.t.a The threads are likely gunked up likely crazy The thread that holds the screw is at the top or bottom of the screw? Or the whole length?

Is this the whole thread that holds those screws?

Yes correct!

Oh ok, cleaning shouldnt be that bad then.