Cut of voltage/current please help

MtbHillBilly

100 µW
Joined
Sep 28, 2022
Messages
9
Can someone please tell me If my batters cut of voltage is 39v and my controllers is 42v should i set it to 39v and if my controller current is rated at 35+1A continuous and 70+1A max and my battery’s discharge current is 20A continuous 60A(100us) max what should I set it to on my controller my set up is a 48v 13ah 1500w 15mosfet soon to be 52v 20ah
 
Most folks aren't going to run their batteries down to the low voltage cutoff (LVC) on purpose. It's hard on the battery.

2nd, there's this thing called voltage sag. The bigger your motor/max amp draw, the easier it is to have happen.

If I go to wide open throttle with a battery voltage in the 45v range (or lower), the bike will shut right down due to the LVC (Bafang Ultra). Thankfully all I have to do is back off for a second and it comes back to life. Many others will need to be turned back on again. Neither situation cool when using max power to get across a busy road for instance....

It's for this reason my batteries are charged when they get down to 46v.
 
42 is low enough. I would never let the battery get that low though. 42 will protect you from yourself, in case you aren't paying attention.
 
MtbHillBilly said:
Howi don’t understand

Set the current limit on your controller to 20A to be conservative, and protect the battery. If you could supply more information about your battery, including the type/brand of cells it uses, and the pack configuration, e.g. 13S#P, where # is the number of parallel groups, then you could figure out what time of headroom you have to set the limit higher. A link to the actual battery would might also provide some of that info.
 
Thank you heres the link to the battery im using

https://www.ebay.co.uk/itm/155047313624?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=g5eb8jpzsyy&sssrc=2349624&ssuid=3hykZyHRQpu&var=&widget_ver=artemis&media=COPY
 
MtbHillBilly said:
Thank you heres the link to the battery im using

https://www.ebay.co.uk/itm/155047313624?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=g5eb8jpzsyy&sssrc=2349624&ssuid=3hykZyHRQpu&var=&widget_ver=artemis&media=COPY

Thanks. Based on the description, the pack is made of generic 2600mAh Chinese cells, although they tout them to be "Grade A". My old pack was 14S8P of similar cells, and I could pull 2000W from it, so around 5A per cell/parallel group, but with a decent amount of voltage sag, so not good continuous. That would be 25A for your pack, which is what I would set my controller limit to if it were me. The 60A max rating looks to be when the pack BMS would trip, since the time show 100 microseconds at that current. Oddly, they call it a 30A BMS, although rated at 20A.
 
Picture of the controllers label
 

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What does the brakes low level mean and booster and speet and dual mode. Also how do i know what the max and low voltage/max and low current/max and low amp rating of my controller is also Tia
 

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I know that “Speet” is the voltage range of the throttle, 1.1v-4.2v. “Dual mode” means it’ll run on sensored or sensorless motors.

I’m not sure about the brake level or booster. You might be ok running at 52v. Maybe someone with more experience can help you with the other areas. :)
 
MtbHillBilly said:
Would i be okay running 52 or 60v through the controller

Probably ok with 52, unsure about 60. 52, or 14S, is 58.8V. 60, or 16S, is 67.2V. 48 would be 13S, or 54.6V. Capacitors and FETs come in all sizes, but the common voltages for caps in the ebike voltage range are 35V, 50V, 63V, 100V, 160V. So it if they are using 63V caps, then 14S is fine, but not 16S. Similarly the FETS will have their own voltage limits.

Me, I wouldn't bother opening up the controller to see if 52V would work, I'd just hook it up. But for 60V, I would peak inside first rather than playing the odds.
 
MtbHillBilly said:
What does the brakes low level mean

Low level brakes usually means that there is a two wire connector (ground and signal) for brake sensors switches, that when closed, shorts to ground, and cuts off the controller power. If the controller is regen capable and has it set on, the input could also trigger regen, or if it support cruise control, it cuts that.
I've never used high level brakes, but I believe that that uses 12V most of the time, and may be utilized for brake lights or something.
 
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