Hi there Back in December 2019 my Backfire G3 arrived and after a few uses the unit refused to power on. It was then that I discovered that it was part of the recall batch: " **Backfire has discovered a defect in some of their Backfire G3 models. They found a flaw in the BMS (Battery-Management-System), which will cause the G3 to lose power while riding." They sent me a replacement and all has been good ever since. Now doing a bit of spring cleaning and I still have the faulty unit laying around. So my question is; has anyone repaired one of these or repurposed it?
Welcome to the forum. You like battery? Big battery is better. Little battery is no bueno.
The range is great on it, so I don’t need to addon to the current one - I did 8 miles to work once, charged it (might have gotten away with no needing to) and then went back home on it in the evening and man were my legs burning! might have been different if it had been 8 miles of untouched tarmac! I use it more for short bombs to places, so only a couple of miles at a time. So thinking if I can get it working as a spare or even use it for a second custom build then that would be good. I think I used it for about a week before it died and was sent the replacement.
What kind of cells are in them?
According to the Backfire site:
Battery:** 50.4V 260Wh (Equivalent to 42V 7.2Ah-7.5Ah)
- 12S 21700 Battery Cells Voltage 50.4V
Sweet. How many p? 3?
Doesn’t matter. Lol. I’d get a different bms. Balance them and put it back together
There is a very good chance the cells are fine.
Pull the battery apart. And remove the outer case if possible. We need to see the cell and the wires.
Take photos and upload them here and we can help you decide the next steps.
Guessing this doen’t really help much. I’m surprised they replaced the whole unit, rather than the BMS, if that was the fault…but maybe not so easy for some owners to swap out.
You need to disconnect that white plug from BMS and do some voltage checks.
The reading on the multimeter should increase in increments of 3.XX - all the way up to voltage of the entire pack.
If each cell group is still holding a voltage somewhere in the 3.XX volt range you might just need to swap the BMS.
I doubt there is any advanced electrickery in there.
Ideally we need to see a picture of all the wires laying flat and how they run into/out of the BMS before recommending the next step.