Smoking 2 chargers in 2 months?? Someone help??

[RC_guy]

Hi guys,
I have been charging lipos for 8 years now. Except 3 years ago I started charging 12S 15ah packs from a Thunder 1220 charger. This was a 300W 14S capable charger. I liked I could charge my 12S pack without any modifications.
The input shorted??? I tried turning it on one day and my power supply would not turn on (ATX 12V PSU). I tried with a 12V battery and the 30amp input fuse on the input side of the board blew. I replaced it and tried the charger again.
After about 5 seconds of the charger being ON with no load, the fuse blew again.

Just over a year ago I got a Hyperion 1420i which is 550W and also 14S capable. I was powering that one with 2 atx psu in series and I cut the gnd wire to one of them.
A week ago it did the same thing. Except this one has a 40amp input fuse that did not pop but my psu would not turn on. And connecting to a 18V battery (to turn the charger ON with no charging load) I almost melted the bullet connector.
This charger is capable of 28V input.

I just ordered a Thunder Power 1430C and I hope this is the last one I need to buy?!?

Could this be due to my psus?
Could it just be that those chargers don't like charging 12S?
They do get quite hot for over 1 hour when I charge.
Could they be repaired?

Thanks in advance!!

 

[dnmun]

do you have the skills to repair them? they can be repaired. why not just build your battery into a 12S pack with a BMS and charge with a regular bulk charger so you can get the reliability and protection? i am just staggered at how much effort i see all these people go through to use these RC chargers for ebike packs just because they don't do things different from everybody else. a BMS and bulk charger is cheaper by far too. especially after 2 chargers down. how many will it take?

 

[izeman]

i personally don't like those atx psu as they are normally not very strong on the 12v rail. i also don't like this psu in series idea. i bought an hp dl580 psu. you can increase it's output voltage to 13.x volts and it can deliver 50a easily.
i can't say anything about the thunder chargers and if they are picky on input voltage.

 

[RC_guy]

I need RC chargers for my RC airplanes.
I have a few 6S 5000mha batteries that I sometimes need to charge in a hurry. I know its off topic but my latest is an 80' wingspan running a 12S 5000mha setup that develops over 3000W
I already had RC chargers when I built my 1st e-bike so it just made sense to use technology I was familiar with.

About the PSUs, I group all the 12v yellow wires together and take the same amount of ground wires I have been pulling around 22 amps with all my psus for many years.

So still:
Could the psus be the culprits?
Do those chargers not like 12S?

As a side note, I am not familiar with any bms. Can you adjust the end voltage of your charge with those? for normal riding I never charger over 4.16V/cell but when I go for a long ride, I will charge to 4.20V

Thanks

 

[dnmun]

you can adjust the final voltage on the charger to stop at the 4.15V level or just turn off the charger after a period of time sufficient to reach that voltage. but to make them balance the pack you have to charge to 4.20V/cell. but bulk charging gets you more reliability imo, and the BMS protects against overcharging. i have a big 44Ah 21S lipo pack so i have to use bulk charging with the Bestechpower D131 BMS. two BMS actually, master/slave.

but those balancing chargers can be repaired. pretty simple circuitry.

 

[RC_guy]

Hey dnmun,
Would you happen to know where I could have those repaired in Canada?
I spoke to a few peoples and they said that if they do not know if the PWM is acting up or one of the caps lost its values, we could change all the fets and it could do the same thing again.
Their is no apparent damage to any components from what I can see except on the 300W charger, the fuse is blown?

If you do not know how I could fix it in Canada, do you have any suggestions for me?

Thanks

 

[dnmun]

on the icharger i found it was the switching mosfets in buck converter that would short out and that killed them. it is kinda easy to identify bad mosfets by using a voltmeter and looking for the body diode between the source and drain. i don't even know of people in the US who repair stuff, much less in canada.

i am stumped on the hyperion i am trying to repair for zippy. i hate it when everything i test works ok.

 

[RC_guy]

Could you please explain how to test the fets?

Thanks

 

[marty]

I need RC chargers for my RC airplanes.
I have a few 6S 5000mha batteries that I sometimes need to charge in a hurry. I know its off topic but my latest is an 80' wingspan running a 12S 5000mha setup that develops over 3000W
I already had RC chargers when I built my 1st e-bike so it just made sense to use technology I was familiar with.

About the PSUs, I group all the 12v yellow wires together and take the same amount of ground wires I have been pulling around 22 amps with all my psus for many years.

So still:
Could the psus be the culprits?
Do those chargers not like 12S?

As a side note, I am not familiar with any bms. Can you adjust the end voltage of your charge with those? for normal riding I never charger over 4.16V/cell but when I go for a long ride, I will charge to 4.20V

Thanks

80' as in 80 Feet?

 

[dnmun]

to test a mosfet you can measure the resistance from source leg to drain leg since they are usually shorted.

when you look at the mosfet face on the legs from left to right are gate, drain, source.

current goes from source to drain. for an n channel mosfet, the drain is attached to the higher voltage, source to lower voltage. turned on by raising the gate voltage above the source by 5-10V.

for p channel mosfet, source is higher than the drain, and it turns on when the gate is lower than the source by 5-10V.

so when you test with the ohmeter it is pushing current out one leg and into the other so the resistance will be different in each direction you place the probes.

when a mosfet is manufactured, the process of doping the layers of silicon used by the mosfet in the 'planar' process of making the mosfets on the surface of the silicon creates a diode in that silicon between the drain and source.

using the diode tester on your voltmeter, for an n channel FET. put the red probe on the drain, and the black probe on the source. the diode tester pushes a current out of the red probe, and measures the voltage between the red and black probes and displays it on the meter.

when the drain is biased higher by this current from the red probe, the body diode is reversed and no current can flow. meter reads open circuit.

reverse the leads and put the red probe on the source, and the black probe on the drain and now when the current is pushed out of the red probe, it flows through the body diode of the mosfet to the drain leg. the reading on the meter shows the forward bias of the body diode. depending on what kinda mosfet and the doping of the layers, the forward bias will be in the 300-600mV range.

so you can keep track of that forward bias value and compare all the mosfets to see if one is damaged and has a particularly low forward bias or higher than the others. that gives you a clue if they are partially damaged.

a shorted mosfet will have a very low or zero value on the meter in each direction.

 

[RC_guy]

Hey Marty,
Its actually 80''