Has anyone come across regenerative braking killing their display? I'm on a 72V system with TFT UCK1 display and I've had 2 of them die on me randomly when using regen at high speed. I'm talking like 40+mph. Maybe I have it set too high? I'm using the MQCON app and set it to 40a for the ebrake function which gives me a moderate amount of motor braking. Should I be using something lower and I'm just blowing the displays with that setting?
Regen killing displays
- Thread starter nelwyn
- Start date
Adrian_
10 W
- Joined
- Apr 12, 2022
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- 89
I'm also using UKC1 with 60A regen for 6000 miles and never had an issue. My guess would be that there's a voltage spike during regen which is too high for the display which kills it. Have you ever paid attention to voltage during regen and seen it go above 84v?
Well the current doesn't flow through to the display, but the current induced voltage from the shunt used to determine the actual current flow with will be a negative value. I had an external wattmeter that didn't like regen. After using it with regen, the accumulated watthour function stopped working. I don't think it could handle the negative voltage through that circuit, but that's just a guess. Maybe there was a defective batch of displays sent out.
I don't usually regen when I'm near full battery. This happened when it was around maybe 76V and the regen makes it go up slightly like 1V.
Chalo
100 TW
Replacing brake pads once in a while is easier and safer. Adding a little battery capacity is cheaper than replacing dead displays, controllers, etc.
I think regen is best left to vehicles that have thousands of kg of m to make their mv².
I only have one e-bike at the moment that will regeneratively brake, and it only does so gradually when it exceeds the unloaded speed of the hub motor. It still bums me out not to be able to go down a hill at terminal velocity.
I think regen is best left to vehicles that have thousands of kg of m to make their mv².
I only have one e-bike at the moment that will regeneratively brake, and it only does so gradually when it exceeds the unloaded speed of the hub motor. It still bums me out not to be able to go down a hill at terminal velocity.
The UKC / etc type displays aren't like the wattmeters--they do not have current-measuring shunts in them, so they don't see any of the voltage generated in them, whether positive or negative.
However, if your controller regenerates voltages above the limit of the LVPS in the display (the circuit that takes battery voltage and converts it to 5v, etc for all the display electronics), it could damage or destroy the display (or anything else connected to the battery voltage that can't handle this). It only takes one momentary spike above this limit to destroy the electronics, and you probably can't see this spike on your voltmeter, especially if it's digital, since they all average the incoming voltages over time, *and* have a sampling rate that can miss some short inputs, *and* have a display refresh rate that changes what you see even less often than any of those.
So you can look at the specs for the display (and controller, and anything else running off battery voltage) to see what they list as a maximum voltage, then try to measure the actual peak (not just displayed!) voltage generated by your regen braking under worst-case (highest regen amount at fullest battery charge voltage). (some good multimeters have a Vmax / peak hold function good enough for this). If the generated voltage is higher than the limit, or even right at it, it is probably what is causing the damage.
If the controller has a setting to limit regen voltage, you can try that by setting it as far below the lowest voltage spec limit as necessary to prevent damage. Many controllers simply prevent regen from occuring when above a regen voltage limit, rather than actually limiting the voltage, so keep that in mind when using regen braking--there may be times it simply doesn't engage.
If it's just a very short spike causing the damage, you could try a choke on the main battery input to the display. (choke = inductor in series).
However, if your controller regenerates voltages above the limit of the LVPS in the display (the circuit that takes battery voltage and converts it to 5v, etc for all the display electronics), it could damage or destroy the display (or anything else connected to the battery voltage that can't handle this). It only takes one momentary spike above this limit to destroy the electronics, and you probably can't see this spike on your voltmeter, especially if it's digital, since they all average the incoming voltages over time, *and* have a sampling rate that can miss some short inputs, *and* have a display refresh rate that changes what you see even less often than any of those.
So you can look at the specs for the display (and controller, and anything else running off battery voltage) to see what they list as a maximum voltage, then try to measure the actual peak (not just displayed!) voltage generated by your regen braking under worst-case (highest regen amount at fullest battery charge voltage). (some good multimeters have a Vmax / peak hold function good enough for this). If the generated voltage is higher than the limit, or even right at it, it is probably what is causing the damage.
If the controller has a setting to limit regen voltage, you can try that by setting it as far below the lowest voltage spec limit as necessary to prevent damage. Many controllers simply prevent regen from occuring when above a regen voltage limit, rather than actually limiting the voltage, so keep that in mind when using regen braking--there may be times it simply doesn't engage.
If it's just a very short spike causing the damage, you could try a choke on the main battery input to the display. (choke = inductor in series).
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