36v kingpan charger .. pouf at 48v

[Ypedal]

Question for anyone of you who might know.

Got a few 36v chargers from Ping set to 41.8v from factory, all good...

Had a local customer with a 48v Lifepo4 pack in need of a charger, so i opened it up, found the potentiometer and set it to 58.4v, hot glued it back down to secure it.

Before boxing it, i took the time to plug it into my e-BMX that has a 16 cell PSI pack ( lifepo4, 10ah ) that was not fully charged but close at resting voltage 56v .. charger kicked in, fan working, charging at 2.5 amps, all was well.. i disconnected and re-connected a few times, then shipped it.

Just got a call from customer to inform me that it blew up.. :x

I confirmed polarity, Blue=Neg ... Brown=Pos ..

he says the battery side fuse blew, he replaced it, it blew again, then 3rd time around the charger itself quit... :| .......

Did he reverse polarity and is not realizing it/admitting to it ?

His battery pack is fully drained so the resting voltage is no doubt lower than my test pack, the larger swing " could " cause a heavier drain but without instruments to test this, i'm just guessing..

Are these kingpan chargers physically all the same 36v or 48v and trim pot adjusted ? . or are there different models for 48v ?

I'm giving him a refund and calling this issue closed.. but would still like to understand how it failed...

thoughts ?

 

[wesnewell]

If you turn the voltage up, you need to turn the current down. 40V@2A is 80W. 58V@2A is 116W. Eventually, it'll overheat and die.

 

[Matt Gruber]

it was 105 watts,
now it is 145 watts.
40% more power, no surprise it is overloaded.
In other words, i know nothing about these specific chargers.

 

[Ypedal]

agreed..

however, it ran here at 13x watts for over 5 minutes ( warm, not hot ) .... and failed at the customer end instantly before even warming up...

the only factor left is the lower pack voltage of his pack vs the higher voltage of mine.... argh.

 

[Ypedal]

ok.. this is making some sense...

the charger model is KP120W-45L ... i assume 120w rated.

at 36v ( 42.0v ) and 2.5 amps = 105w

At 58.4v x 2.5 amps = 146w

so i would have had to set it to like 1.8 amps max or so to keep it below the 120w rating...


right ?

 

[Matt Gruber]

1.8 sounds good, still a guess since i'm not a charger engineer.
I'm trying my sla charger on limn konions.
it is rated 1.67a, stage 1 ends at 44.8v, so i have to use a timer as i only want each cell 4.00-4.10v for 75-90%. I'm just experimenting.
so it puts out 1.5a at 36.7v and drops to 1.2a at 41.0 on a 4p10s pack
so you can bet on a deeper discharge, like 34v it will jump up to about 1.67a.
so when you tested it, it was a near full pack, and he put it on a dead pack, and BOOM!
i hope this helps!
Also, i blew 2 fuses on another charger with dead cells. they really suck amps! like triple normal.

 

[Spacey]

Ypedal, couple of things I found out on those chargers...the hard way lol......the wires on a lot of them are reverse coded as in Blue can be positive. Blew up a charger this way ages ago, and I would change the output charging amps down by 30% when upping the voltage.

 

[dogman dan]

I agree with the others, despite the test at your place, the charger was doomed if it ran for very long at higher than rated watts.

It might not have been cranking at the full watts in your test, if his battery was lower voltage at the start. I would think that if you set the wattage lower next time, it should work. It's not like the thing has a bunch of 40v caps in it.

But it's quite possible he reversed polarity too. I sure did it enough times, and was very sure I had it right when I got Kff.