To: EP/KP series charger users who use them for LiFePO4

P

ping

10 mW
Joined
Mar 7, 2008
Messages
32
Hi all,

Long time no see.

Recently, we're testing EP series chargers and found a problem when charging LiFePO4 battery packs. We're glad to share it with you here.

View attachment 2

The EP series chargers are originally designed for Lipo battery packs. So, it has a function of Power lock - when battery pack is charged till charger cut-off, the power won't be turned on even if the battery voltage is reduced or you plug another empty battery pack to it, unless restart the charger or re-plug it to the wall.

It's a good function to protect Lipo battery packs against over-charge, but could cause bad imbalance problems for LiFePO4 battery packs. If all LiFePO4 cells in a pack are balanced or almost balanced, the charger can fully charge and amost balance all the cells . However, if there's a cell is not balanced and BMS is resistor heat bleeding type, the charger cannot balance the pack and the imbalance problem could be worse and worse.

Anyway, we have studied the circuits in the charger and found way to solve the problem.

On the board near the fuse, you can find a daughter board that is in charge of the power lock function.
View attachment CIMG1504.jpg
And a 3 pin component can be found on the small daughter board. Just cut it off and take it out. That's all. Please take a look at uploaded pictures.
View attachment CIMG1510.jpg
After that, your charger will be turned on again if battery voltage is lower than the BMS's threshold.

BTW, we have founded co-operation relationship with the original manufacturer of EP series chargers. And we're testing EP-A and EP-J series chargers now and will sell them in the near future.

Please pay attention that some resellers just resell BMS or chargers or assemble some battery packs but have never checked the qualities and functions. We didn't and we will not. We're always developping better and better LiFEPO4 solutions.

Have a nice weekend,

Ping
 
Thanks Ping.. i'll do that mod. it's few second work.. :wink:

tehre is 4 battery arrived yesterday.. I hope the rest and the charger will arrive today!.. i'm now searching for a GOOD seatpost rack able to cary the weight of a 15Ah 48V battery that WILL NEVER BROKE eventhough the bad road conditions... hard job!

Doc
 
I just received another 2 chargers that needed this mod, sold as Lifepo4 chargers but have the 3 pronged transitor that shuts off the power never to turn on again unless disconnected from power supply and re connected.

Important for people to check when they get a new charger otherwise their BMS can never balance the pack.
 
Amen to that!

I was unaware of this peculiarity with the 38V 360W KP chargers and have been using them "as is" for the past year. I began to notice that my 38V 15Ah LiFePO4 batteries seemed to be gradually getting less and less able to provide their rated Ah.

I came across the ping modification post when searching for some info and promptly modified my chargers. Here is some data:
.......Before = before modification (June 1st; about 75 cycles on the batteries, freshly recharged and then tested with a 5.4 Amp resistive load -- 6-200W light bulbs)
.......After = after modification (July 1st; another 8 cycles recharging with the modified chargers)

.................Batt #1................Batt #2
Output...Before.....After........Before....After
5 Ah......38.4V......38.3V........38.6V......38.6V
10Ah.....37.3V......37.6V........37.8V......37.9V
13Ah.....34.1V......36.6V........30.1V......36.9V
13.8Ah....LVC.......35.7V.........LVC.......36.5V
15Ah..................32.1V......................33.2V

A major improvement in battery output! :D
 
A large number of photos were lost sometime last year and more were lost in the recent change of servers.

Here's a photo of my 360W 38V 8A charger showing the transistor (circled in red) on the daughter board that stops the BMS from balancing a LiFePO4 battery pack. If your charger has this board, just clip off that transistor. Measure the charger current while charging is taking place. When the current drops to zero, observe it for 5-10 minutes. You will see the short pulses in the current if balancing is taking place. I usually leave the charger connected overnight.8 A charger - internal view.jpg
 
Thanks for that, looks like the internals of mine. I've removed the Trans. and the charger is now cycling under the BMS balancing mode.

Cheers

Dave
 
Hello,
I'm currently doing some tests on a headway battery pack and I'm looking for a solution to power lock/unlock my EP charger from an external source (BMS with a HV signal). Does someone know how can I use the daugher board or an other pin on the charger to add this functionality to my charger ?
Thanks
 
hi,

can anyone help me with this problem ? I have an Chinese charger that has this lock; it starts only I plug off both the AC and DC cables. I tried to remove that transistor from the daughter board but nothing new;
The charger stops and never restarts.
 
Hi,

Can someone post the pictures for this mod? I have a KP1500-90-L charger with the cut-off option. When the BMS cuts the charger output during the balancing stage the cut-off kicks in and the charger needs to be AC power cycled to turn on again.

Thanks.
 
if you post up a picture of the inside of your charger we can show you where the daughter board is. i just wiggle them back and forth and break off the entire daughter board to convert them from lipo charger with latched output to lifepo4 charger with CV end phase and low current for the balancing.
 
Thanks for your input dnmun.

Here is a couple of pictures of the KP1500-90-L Kingpan 1500W LiFePO4 Charger:

KP1500-90-L%20Pic1.jpg


KP1500-90-L%20Pic2.jpg


Are you talking about the small daughterboard near the PCB edge and display cable connector?
 
yes, the one with the little transistor at the top. that is the transistor ping was talking about. you can see " A-(G) " in the corner above the two little resistors and two small caps under it and a 4 pin opto and 8 pin op amp next to it. those 5 legs that hold it to the pcb will break off when you wiggle it back and forth.
 
Thanks for your answer dnmun.

The two solutions:

1 - Cutting the transistor

2 - Removing the daughterboard

are equivalent from the charger's functionality point of view?
 
i have never cut the leg of the transistor so i don't know if it is equivalent. i always just break off the daughter board at those 5 legs and remove the little daughter board.
 
I tried first the transistor leg cut because it was the least evasive mod. I could always remove the whole daughterboard later. It worked perfectly. The cut-off mechanism is now disabled. Top cell balancing was quickly achieved to a few millivolts.

Thanks again dnmun.
 
dnmun said:
yep, those daughter boards are there to prevent overcharging the lipo when it hits full voltage. with a BMS you need that small balancing current at CV to balance the cells.
Click to expand...
but if you use LIPO with a bms you still would like to get rid of that board. right?
 
yes. if you have a BMS with a balancing network then the latching output is not needed. it cannot overcharge then. if the lipo had no way to drain off the charge from the constant balancing current through a shunt resistor then it would continue to overcharge.
 
About to do this to my charger. It looks very similar though not identical to the others in this thread. Am I right that it's the same board ad I can safely cut the transistor on the daughterboard seen just under the brown wire coming from the fuse holder?

and
 
yes, that is the latching output board ping mentioned. you can also just remove it by pushing back and forth, rocking it on the pins into the pcb below and eventually the legs all break off and you can remove the entire daughterboard. if you cut the collector on the transistor then you can resolder it later if you wanna reuse it as a li ion charger with no BMS. i always just break them off and remove them. i have a bag full if anyone needs one.
 
dnmun said:
yes, that is the latching output board ping mentioned. you can also just remove it by pushing back and forth, rocking it on the pins into the pcb below and eventually the legs all break off and you can remove the entire daughterboard. if you cut the collector on the transistor then you can resolder it later if you wanna reuse it as a li ion charger with no BMS. i always just break them off and remove them. i have a bag full if anyone needs one.
Click to expand...

That did the trick, thanks again dnmun!
 
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