Adjusting King Power chargers

[dnmun]

you cannot balance the pack without using a BMS unless you go use a balancing charger. if this is a new build pack then if the cells are not balanced initially it does take forever for them to balance this way.

you can do like zippy said and use a resistor to drain the current off of the high cells to get them closer but you don't have to remove the BMS to do it. i use big cement power resistors with alligator clips on the leads so i can clip it onto the cell i wanna drain, or group of cells. but you gotta keep the power in mind or the resistor will get too hot.

sometimes i have melted the solder off the connection between the resistor and leads it got so hot.

 

[izeman]

i think the one cell is broken. i discharged this on twice to 3.3v (i know 3.3v is a broad voltage for a lifepo4 cell - can be anything from nearly empty to nearly full). but even at 3.300v it charged to 3.9v faster then any other cell, when bulk charging the pack (all other cells at 3.4v already). the other cells didn't have time to catch up. i was hoping to avoid open up the pack and replace the one cell.

 

[dnmun]

yep, no capacity left.

 

[izeman]

but i checked every cell before. discharge to 2.6v, charge to 3.65v, and every one gave at least 18Ah.

 

[dnmun]

if it was caused by high internal resistance then the voltage would drop back down to the same voltage as the others. you could try swapping locations of the cells to see if went along with the location. i always found decreased capacity but this was with old and abused cells too.

 

[jumpjack]

How hot is it getting? Mine get pretty warm at 600W, but I can still easily pick 'em up and hold 'em in my hands, even on the hot side.

Is your fan working right? It should be running unless the status LED is green. Mine used to get hotter until I got the fan working. You could probably skate by for a while by turning the amps down a ways.

The ticking sound is probably a capacitor starting to fail. If you can figure out which one the ticking sound is coming from, you should replace it unless your heating problem is really bad, in which case you need to fix that.

Even 10 (ten) of my Kingpan charger failed in 2 years (warranty time) due to venting capacitors due to overtemperature!
What could it depend on? I never modified anything in them, and fan always worked properly until final fail.
Weird thing is that there is a NTC in the charger... on the opposite side w.r.t. the hotter part of the charger!

Unless your KP charger is vastly different from mine, the charger will produce its maximum voltage when it is plugged in and the switch is turned on. The red and green lights will be go but the fan will not run until the battery is connected. Do you have a voltmeter to measure it?

Measure the voltage without the battery connected. Then when you connect a partly-discharged battery, the green light will go off, the fan will run, the voltage will drop and the charger will go into its constant-current mode. At that point you can adjust the charging current if you want to. Just don't exceed the power rating of the charger. Current multiplied by the max voltage equals max power.

Always connect the battery after plugging in charger and after turning on the charger switch (if it has one). This will prevent a spark and preserve wear on your connectors.

My charger does not start at all if I connect power BEFORE the battery.
Or maybe it starts in CV mode and I can't see it as the fan does not start?!?

This is my charger, how do I identify Voltage and Current pots?

It's rated 67.2V/3A and it charges an unknown-technology battery, whose cells are at 4-10-4.20 after a full charge.

1: trimmer 1
2: trimmer 2
3: useless NTC (does not prevent overtemperature)
4: transistor in daughter board
5: trimmer 3

 

[dnmun]

why did you take the charger out of the the case? is it broken?

5 is the output voltage adjustment, 4 is the daughterboard that turns off the charger when the charger reaches full voltage and the charging current drops very low. when it detects this low level of charging current the op amp triggers the dauthgterboard to turn off the charger until you reset it by unplugging and replugging in the charger.

 

[jumpjack]

why did you take the charger out of the the case? is it broken?

Yes, capacitors around the coil blew up, the uppermost capacitor right of the coil even vented due to high temperature... and it's not the first time!
http://jumpjack.wordpress.com/2012/03/20/diario-elettrico-36-viaggio-nel-caricabatterie/

 

[fechter]

The NTC is probably an inrush current limiter in series with the AC line.

It sounds like they used poor quality capacitors if they failed early. Those could be upgraded.

 

[jumpjack]

I tried moving all the capacitors out of the cabinet.
A fuse burnt at first recharge.
Replaced the fuse, I retried the charge... and a transistor burnt!
Damn.
I did some welding wrong I suppose...

 

[amberwolf]

Unrelated to the above, but I wanted to note here that the one I had that "died" was easily fixed--it turned out that the large final inductor had simply come out of the board at one side. Just had to be resoldered and then now it works fine.

 

[jumpjack]

By the way, is it normal that that coil becomes VERY VERY hot during charging?

 

[amberwolf]

Probably--that's likely why it's right in the fan's airflow path. But depending on where your coil is relative to other hot parts, and how the air flows around them all, it could be made even hotter than it normally would be by hot air being pulled past it from other stuff.


I don't know what temperature the coil on mine is, but when it's at the 4A phase of charging, right at the start, it'll get hot enough I cna't leave a fingertip on it for even a second, without the case being closed up and the fan moving air across it thru the length of the case.

 

[jumpjack]

I don't know what temperature the coil on mine is, but when it's at the 4A phase of charging, right at the start, it'll get hot enough I cna't leave a fingertip on it for even a second, without the case being closed up and the fan moving air across it thru the length of the case.

I think there are way too many big components on the way, blocking the air flow. And I also think it's not so smart to place capacitors 1 mm apart from a highly heating component.
But overall, why the hell is the NTC on the opposite side?!?

 

[fechter]

But overall, why the hell is the NTC on the opposite side?!?

Trace the legs on the NTC and see if it is in series with the AC line or between the bridge rectifier and the main capacitor. I've seen them used to reduce the inrush you get when first plugged in to the wall. After the supply gets going, it heats up and the resistance drops.

 

[amberwolf]

I think there are way too many big components on the way, blocking the air flow. And I also think it's not so smart to place capacitors 1 mm apart from a highly heating component.

The latter I certainly agree with, but it is a common design "flaw".

However, the common reason to do it is to keep traces short because of inductance/ringing/etc., as these are usually high-current types of circuits they're on, and the farther away they are from the stuff they're filtering, the less effective they are, as a general rule. There are ways to engineer the PCB design and/or add other capacitors of different types in there in addition to minimize the problem while allowing more distant placement, but it costs more to do, and takes longer to design and test, and probably most engineers don't have the experience to do it right the first time.... Of course, since they usually don't get the chance to try to do it, they don't get the experience either....

Mostly, it's about money. That $1-$2 in parts and time to install them costs a lot of money over a manufacturing run of thousands, assuming that they don't test them and/or that they don't have any failures due to the additional parts (defective or placed wrong).

Then there is the extra physical space taken by the design changes, making the unit larger or differently shaped, requiring what would probably be a more expensive casing, more PCB area, etc., all of which is again more money.


Since most companies don't care how long these units last, only that they sell in the first place, it's all about saving every penny they can, and making more profit.



If they really cared about the usability/lifetime of them, they'd do a LOT of things different in design and manufacturing, especially considering these are going to realistically be used as portable devices, and need to be "hardened" against that sort of use/abuse. But they're not, hence the failure of my own with the coil breaking loose from the PCB, and other people's similar types of failures from vibration/etc.

 

[dnmun]

on the chargers i have seen where that little 35V cap between the choke and the transformer blew and where the other 35V220uF cap next to the big output cap blew up was because the choke had shorted to the trace that delivers current from those diodes next to the transformer over to the input of the voltage regulator on the side. this is correlated with the output cap shorting out and blowing too when the charger goes to high voltage as the TL494 seems to make the charger run full tilt up to 116V.

you can check continuity between the choke and the input to the voltage regulator to see if this is what happened. the trace runs directly under the choke and the choke overheats and melts the shellac over the trace so that the choke, with full output voltage, shorts to the 20V input to the regulator which blows up those caps since they are tied to that trace.

 

[jumpjack]

by "choke" do you mean "coil"?

 

[izeman]

by "choke" do you mean "coil"?

yes he does..

 

[dnmun]

or toroid. if the choke has shorted to the regulator input it pushes high voltage onto all of those capacitors in the back end that are not part of the charging output.

the reason the choke gets so hot is because of the eddy currents induced in the ferrites in the choke core and the current level flowing through the small wire wound around the core. the oscillator runs at 28kHz so it does make heat.

i bot some 14G magnet wire to rewind the choke on one of the chargers i repaired that had burned up the choke just like this one. and then i put down a layer of plastic under the choke to isolate the trace that goes over to the regulator. it takes about 40" of wire to fill the space. i bot 40' on ebay (200o rating) for the cost of two new chokes from mouser, before shipping. i can give you the mouser part number for the choke if you want it.

 

[jumpjack]

What about Yangming chargers?
Any experience with them?
I have one rated 77V but tagged YMC60-12L , so it is probably overvolted (it was used to charge 19 LiFePO4 cells on an Efun scooter, although I think it's a too high voltage...).
It does not give out any voltage if not connected to batteries, so I can't even figure out which is the + terminal! :x

 

[dnmun]

never heard of them. you can check continuity from the pcb to the plug to determine polarity and usually you can measure output voltage in front of the relay or pchannel FET on the output.

 

[jumpjack]

never heard of them. you can check continuity from the pcb to the plug to determine polarity and usually you can measure output voltage in front of the relay or pchannel FET on the output.

Fortunately I just found a "+" and a "-" printed on PCB.
Interesting is that "-" is on red wire, "+" on blue one.