Solved! Braking issue with fully charged battery

Here’s a screen shot of my settings. Batt min is at -12A

Could be a variety of things, but it does sound like what @link5505 mentioned. Though, I wouldn’t imagine you need to go all the way to 90% to stop it from happening. Another possibility is that you’re getting voltage spikes during regen that bring it over the max. Anyway you can plug it into your laptop and do active sampling to see if you get a fault code? You Might have to hold the brake down while turning the wheel during full charge to see it.

It sound like some kind of Over Voltage, probably a fault from the BMS. Are the Brake working without any load ?

Edit : Also are you in bldc mode or foc ?

Same thing happens in both BLDC and FOC. Brakes work fine once the battery is at 90%. Charging it up now. Gonna see if I can get a sample

Also, if can read the fault* in the BLDC Tool it would be great.

I agree with @link5505 this is a common story with VESC.

They use a dual-drive system. They describe it (albeit in a very basic way) here:

The solution for most of us with single drive, is to reduce braking force in BLDC. Then less energy is created when regen is happening, so you’re less likely to trip your VESC’s cutoff threshold. You could charge the battery just below max. The problem with this is it is at max charge, for most BMSs, where balancing happens.

When I know my battery is full, I avoid heavy extended braking for the first few minutes. That’s how I solve it personally, along with slightly reduced braking force settings.

@Mrmoonlight it sounds like you’re regen settings are not configured well for you setup, thus the sensitivity you’re experiencing. @onloop wrote a good post about it here, try manipulating the settings according to this post:

Got an over voltage fault when I brake. I’m able to get it to brake when I push the throttle half way for a sec, then apply 50% brakes.

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Sounds like one or more of your cells might’ve gone bad causing the overvolt during regen.

@treenutter The reason I’m hesitant to go to that conclusion is because that he needs to go all the way to 90% for the issue to go away. This should stop happening even at 98-99%. The settings seem correct for battery Regen according to his screenshot.

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I think maybe they use something to simply dissipate the leftover energy as heat?

It sound like a problem with the bms or the battery, I think you should contact @carl.1 or @onloop to take a look into your problem.

On the faq it says they have a secondary braking resistor to correct the problem. My theory is that the resistor reduces the voltage to prevent current from flowing back into the battery and it redirects the energy as heat to a sink.

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Sounds good to me. Wouldn’t reduced voltage means that the board is slower at the start though?

Braking resistor would mean it’s lowering the voltage against current from flowing into the battery, not out.

Ah, got it. I wonder why other sellers with ‘regen braking’ don’t do this…

I think it’s because it requires additional engineering due to it being a “secondary braking resistor” meaning it needs to have a primary one for actually regen braking when it’s not full. I could be completely wrong though, so a bit of a disclaimer there :slight_smile:

I think ur probably right. Either way, mellow defenitely packed more into their product than other sellers, so it’s not surprising that they took the time to make sure braking is always available

I have the same OVER_VOLTAGE braking issue with the space cell. However, my display recently stopped working so I can’t check at what percentage it fixes itself. Do you also get the OVER_VOLTAGE error when you rapidly press the throttle to full in short bursts?

I thought the vesc and braking at full charge was a risk because you can over charge the batteries and blow them up but the brakes worked fine until that happens:grinning:

Nope, just when I hit the breaks.

I recall hearing somewhere that the SpaceCell had some protection against that and it would only pose an issue if you started your ride braking down a big hill. Otherwise, once you start off, you deplete the battery enough that it shouldn’t pose an issue.

So I messed with my settings a bit and at 97% charge, I needed to set my Motor Min -10A to get it to brake without any errors. Once I got down to 95%, I could up that to -25A.