80v charger blown caps .

[petehall347]

ok i have an 80v charger here that came in not working . soon figured out the broken legs on the output diodes . must have been dropped to do that . i repaired that problem by soldering wires to the broke legs so as to reconnect them . all seemed fine so charger went back to owner . after 20 mins of charging there was a pop and smoke but charger still working . i have it open and found 2 series bypass caps blown to bits .these connect across the output caps . first off is what may have caused them blow and what to replace them with ?

[petehall347]

Re: 80v charger blown caps .

forgot to say i have another of these chargers i can take apart to measure values on those caps but would be easier if someone can give me a ball park value to order .

[stj]

Re: 80v charger blown caps .

probably 100n 50v
check the blue ceramics - top right in first pic.
one has a mark

[petehall347]

Re: 80v charger blown caps .

well spotted i missed that blue cap .tried to clean off the mark but its staying put so best replace it ..its marked 222 1kv . i expect its 2.2nf 1kv

[stj]

Re: 80v charger blown caps .

i'm sure a 2KV will fit

[petehall347]

Re: 80v charger blown caps .

ordered 1kv ..i also took the good charger apart to have a nosy at the caps . 180nf but in circuit so wont be right . only measure one way so has to be wrong .

[momaka]

Re: 80v charger blown caps .

ok i have an 80v charger here that came in not working . soon figured out the broken legs on the output diodes . must have been dropped to do that .... after 20 mins of charging there was a pop and smoke but charger still working . i have it open and found 2 series bypass caps blown to bits .these connect across the output caps . first off is what may have caused them blow and what to replace them with ?

Well, if that charger was indeed dropped a few times, those ceramic caps could have gotten cracked then and were just waiting for "the right moment" to short out and throw the sparks show.

I fixed a surround sound system a while back that had a popped ceramic cap on one of the 35V rails after the owner moved from one house to another (which probably disturbed the unit/PCB enough to crack the caps.) After fixing this issue and the system working fine for a number of years... it did it again with another ceramic cap and once more when it was moved around. So either the PCB was flexing too much and breaking these or the caps were already with defects from the factory and just waiting for the right moment to go bad.

[petehall347]

Re: 80v charger blown caps .

ok changed the caps including the blue one . did a good job considering the damage. one trace had to be glued back down .. charged a battery but it only took ten minutes . no smoke and nothing looking burned so its going back to the owner for more testing .

[petehall347]

Re: 80v charger blown caps .

this thing is back again . different fault this time . the charger is saying bad battery pack but tried other chargers same packs and no problems ..am guessing its whatever makes the charger think the pack is bad . its generally too low pack voltage . tested all diodes and resoldered some iffy bits but still not working .. might start a new thread .

[sam_sam_sam]

Re: 80v charger blown caps .

Check the input voltage to the micro controller to make sure that it is correct voltage ( battery voltage ) especially sense you have one to compare to

[petehall347]

Re: 80v charger blown caps .

not figured which pin on mcu just yet as need to remove lacquer of it and get the datasheet .
i have found though if i run it off about 100v mains it starts up and charges for a few minutes then knocks off with flashing red light to say bad battery pack .. but it only appears to be charging at about 79v .. this may or may not be a clue as to where to look next

[sam_sam_sam]

Re: 80v charger blown caps .

Actually it is a clue it might be something with the voltage divider circuit that goes to the micro controller or that part of the has an issue of some sort

[petehall347]

Re: 80v charger blown caps .

ok have pic of the micro and 2 other chips just for fun ..
i cant find the datasheet yet

[petehall347]

Re: 80v charger blown caps .

well the bloody thing wont even try to start up today .. all i did was look for shorts and anything else obvious . there was a burning smell yesterday that i didn't find where it was coming from .i thought it was my dodgy electrics in the shed but maybe not .
there are a few pins on the mcu that seem to be shorted together ..i really need to pick up another charger to compare things with .

[petehall347]

Re: 80v charger blown caps .

it appears the mcu has managed to short out internally . have tried removing some ceramic caps thinking it might be one of those but no joy . the 5v feed to has 2 ohms to ground ..will remove the ic later to confirm .. am guessing the ic will have some custom firmware installed that i cant do much about even with a new one .

[petehall347]

Re: 80v charger blown caps .

ok its dead jim . will grab the other charger just to be 100 percent certain .