Ok, that sounds like it might actually have been limiting current to it’s max wattage… to limit current it has to drop the voltage so that the delta above battery voltage only draws so much current.
on the other hand it could have been just stressing components and dropping voltage cause of that and about to blow a fuse or a component.
You could stick a current meter inline to be sure. and keep an eye on temps of things… … FAFO as it were. ( My bet is that it will harm the PSU before the battery. )
Looking it up, that seems to be a 1.5 A limited power supply, so that sounds like it’s just charging normally. When you charge something with anything current limited, the voltage will start below the maximum and climb until the battery is mostly charged. Things that aren’t current limited are fairly rare, AFAIK, because they’ll fail in a huge number of different ways. If it weren’t current limited it would probably just break the power supply as soon as you plugged the battery in, but it could also hurt the battery in the process.
but I think things that aren’t current limited aren’t rare.
some will fail. some will blow a fuse. some will trigger a soft fuse. but i think most that weren’t designed to be constant current won’t be current limited in the usual CC way.
I couldn’t confirm the above device did current limiting in any kinda CC way. but if it does… then yah it’s fine.
Experimenting with the clamp meter, clamping both conductors should cancel each other out. What does it mean if you get a reading? What is voltage leakage, and why does it happen?
Probably just not fully canceling it out because of how the two fields arnt fully coupled. magnetic fields aren’t perfectly spherical frictionless cows so the physics isn’t perfect. Clamp meters aren’t 100% accurate. But often if the imbalance is real and not an artifact it is because part of the circuit isn’t in the clamp. Like a neutral or phase conductor has been miss wired down stream or a return path has a different sink for the voltage. Short answer: it’s complicated. It depends on the exact situation
Your vaccuum and battery look extremely similar to mine.
Set your power supply to 29.4v, when it is not connected to the ~25v battery…
When you connect it to the battery, its voltage display will fall to 25.7v or so.
If you get your clampmeter zeroed, and then clamped over one wire it will display about 1.5 amps.
The voltage will rise over time, and somewhere around 29 volts the clampmeter will show 1.4 amps, then keep tapering lower as voltage approaches the 29.4v max.
When the clampmeter reads 0.1 amps the battery is full*. The voltage should never rise above 29.4.
I suspect that the BMS on the battery has Diodes to prevent backflow into the provided wall wart, should it be unplugged from wall. Diodes cause voltage drop. I believe, with no evidence, that they send out these vaccuumes with 7s batteries but 29.4v+ power supplies/charger/wall wart, is either that they completely rely on BMS to stop charging when any one cell exceeds 4.25v, and or the Diodes reduce the max charge voltage to 29.4v.
I want to open up my vacuum’s 7s battery and put better cells inside, but likely won’t anytime soon.
I unplug my vaccuum when it says 99% on the display. It will Display 99% for quite a long time before going to 100, then shutting off display and showing blue lights.
I don’t want 32.15v reaching the cells should something fail.
Toss or revive? A couple weeks ago when I last checked it was like 2.65 per cell so didn’t sit too long below acceptable levels, but I know generally below 2.5 is no go.
12s4p p42a for a low power board, so it wouldn’t be abused in terms of discharge current.
Revive, it’s low enough to age but not below 2v a cell. It’s likely going to drop more if you don’t address it immediately. Charge at minimum current. As little as you can and get it back over 3v a cell. There is so little energy below 3v that even the tiniest drain can kill an ignored pack. That they are all still so balanced is a good sign though.
This is my opinion btw - i wouldn’t feel comfortable selling any pack that got neglected like this but i would run it personally
It’s alive! Had to use a 10S charger to be able to charge it. Went back over 2.7 per cell within a minute. By the time it reached 3.3v per cell it balanced out pretty well already so I guess it’s healthy enough still to run in this board!
That’s great and good save. Just don’t judge the balance in the middle of the charge though - top and bottom are where the pack gives you good information -
Because so much of the energy comes from the middle voltage range the difference between p group capacity can be a lot but only showing just a few millivolt difference. If the p groups were glasses of water the shape would be narrow bottomed and topped - you can see the differences in volume (stored energy) and have more precision (volt per watt hour) when you are in the narrow sections. Top it up and judge the balance there, then look at the bottom of the charge and just it’s health.
… FAFO as it were. ( My bet is that it will harm the PSU before the battery. )
