48v lifepo4 charger = 55v need repair help

[Subfightr]

Hello friends, I have been having the damnedest luck with my Ebike. The first charger that was sent to me blew a fuse the moment I plugged it in, repaired the fuse then the entire thing blew up. So Vpower (in china) made me a "deal" by selling me a 5ah "better charger" for $20 total, this will charge my 48v 20ah lifepo4 battery enough to go for 4 blocks before instantly shutting off.

Placing my multi-meter inside the plug of the charger shows an output of 55.2 volts ( you can watch it here if I did not say it correctly (new to this) [youtube]KCy9HQN-EhM[/youtube] ) To my understanding the reading should be about 60v

The seller says I can pay for shipping and ship it back to him once he gets it he will send me a new one, this will take months! OR he says I can have it fixed by someone.

I have no idea who to take it to have it fixed. Any of you guys know? Or would any of you be willing to walk me through repairing it myself?

Thanks in advance.
- Sub

 

[kentlim26]

hi

i got my charger from vpower too, i went to see what voltage is ? yes you are right, it iss voltage 60.1v vpower charger. my is a 5amper charger from vpower. don't take the shippment to long to be sent to your home. before you are asking them to send, please ask them to ensure they have tested the voltage and a photo copy need to be send to your for assurance. They seldom or never check their things they they will just send.

Fixed by who? i think it will be a long process waiting for the charger to arrival. if i am you i will get another charger from other seller ecitypower (maybe) their products seem to been better the vpower.

kentlim

 

[dnmun]

i just tried to fix a few headway chargers, one was damaged in manufacturing, thought it would work, but didn't and the other didn't work either.

what do you have for voltmeter? is it possible it was in the constant current phase and 55V was all it could do and maybe if you put it on your pack it will charge to a higher voltage.

can you certify the voltage polarity on the leads before you plug in the battery? is this one of those octopus type chargers, just a picture would help.

 

[Subfightr]

Hi dnmun, I corrected my link in the first post. It is a video I sent to the people in china as they did not understand what I was telling them. In it you can see what my charger looks like.

 

[dnmun]

like i said, can't see video on my laptop because it has no memory. but if you plug the charger into the battery, through the BMS, it should start charging, so then it will be a flashing red led until it reaches final voltage and then the led goes green. measure the voltage while it is charging up by keeping your voltmeter on the charging leads all the time and let us know.

you have never charged this battery before? this was the one where the charger blew up the first time you used it?

it may stop charging at something lower than the full pack voltage in that case, but start charging anyway and let us know. then discharge some, not too much, and recharge, keeping track of the voltages.

anybody else have the same problems?

 

[goodluck-2009]

Hello friends, I have been having the damnedest luck with my Ebike. The first charger that was sent to me blew a fuse the moment I plugged it in, repaired the fuse then the entire thing blew up. So Vpower (in china) made me a "deal" by selling me a 5ah "better charger" for $20 total, this will charge my 48v 20ah lifepo4 battery enough to go for 4 blocks before instantly shutting off.

Placing my multi-meter inside the plug of the charger shows an output of 55.2 volts ( you can watch it here if I did not say it correctly (new to this) [youtube]KCy9HQN-EhM[/youtube] ) To my understanding the reading should be about 60v

The seller says I can pay for shipping and ship it back to him once he gets it he will send me a new one, this will take months! OR he says I can have it fixed by someone.

I have no idea who to take it to have it fixed. Any of you guys know? Or would any of you be willing to walk me through repairing it myself?

Thanks in advance.
- Sub

Hi,Sub,
If your battery is 48v ,the floating voltage of 48v charger should be 60v.
You mean 55.2v,is it for the fault charger?

 

[fechter]

Yes, 55v is a bit too low. It should be closer to 60v.

Many of these chargers have a voltage adjustment pot inside. You might open the case and look for one. Of course, this might void the warranty.

 

[Subfightr]

I'll try and get a hold of my girlfriends digital camera once she gets home (around 6 or 7 pm) All I can do is make movies with my Flip Video camera and then pause it and get you a still photo, but it does not look very good, if you needed to look at a circuit board or something it's just a blob of dots. So yeah, I'll get back to ya'll asap and we'll kill this things warranty together! I don't have the money for another one but screw it! FOR SCIENCE!!!!!

 

[Capripower]

Hi I have a headway charger with 2 headway 48/20ah packs and some difficulties charging after they sat around for 3 Mt.
can I measure voltage directly on the charger output plug without the battery connected ? when I measure it with the battery connected it will start to pulls and as soon as I remove the probes it will return to normal ?
Thanks for any help
Felix

 

[dnmun]

you will have to open it up enuff to determine if the screws are loose or if the silicone rubber caused the connections to corrode. and you have to measure each cell, and it would be best to keep it all on the other thread too, or you can just stick with this one i guess but nobody can do anything for you until you open it up and measure them. it does sound like it was damaged in the wreck though and allowing it to discharge doesn't help so open it up and take some pictures.

 

[317537]

Just for my own learning doesnt a 48v for 16 cells lifepo4 charger float at about 53v and full charge mode is at 59v.

His charger is in float mode in the video and even this is a little high from what I am reading, but I also believe lifepo4's can handle a higher standby mode and besides the BMS should keep this under control shouldnt it.

Even my 48 SLA charger should do this job fine as it floats at 52v and full charges at 59.2.

 

[317537]

Take the bike for a ride and then plug the charger in and then test the voltage while its charging and when almost finished. Take a while and watch the voltage rise on the pack.

Do the lights change colour or does one switch off etc.. Often a charger will not go into full charge mode unless the pack has been discharged enough to trip the flip flop circuit in the charger.

 

[Subfightr]

Hi 890709870986... Leslie ? I assume you are talking to me. The charger that was being tested in the video never goes into a fully charged mode. I have depleted the battery pack to the point of it shutting off, plugged in the charger, left it plugged in for days, then road 4-8 blocks before it died, I did this twice. Both with the same result. I wish I wrote down the numbers when the pack was charging, I know that it never got above 52v. And when it was dead the voltage read 48v.


The lights on the charger in the video never ever change, no matter what. The maker says they should turn red/green when not plugged in, orange when charging, and green when fully charged. Yet only the red and green leds remain on, constantly, no matter what. No change in color, and one never switches off.

My 48V sla charger that I have been using for a month now, gets a reading of 55.9v when it states that the bike is fully charged the battery reads 53 volts.

So you are saying that you get a full 59 volts outta your Lifepo4 battery once fully charged with your 48v sla charger?

Seeing as someone else posed a new question, I am a but confused as to who is replying to whom.

 

[dnmun]

he has a pack that won't charge either. i wonder if you have low cells that are causing your LVC shutdowns. did you measure all the cells already too?

i thought this was a new pack. no need to take pictures inside the new charger if it is just low voltage then there is nothing to see, except the layout of the board, but i can explain what the stuff is on the board if you do that too.

 

[317537]

Weird.


I think.

It wont flip into full charge mode becuae the IC circuit is not responding due to the reference feed components suffering or the ic is out. Then volatge seems to tail out past the float value, and the switchmode is limping and crashing IMO and not supplying enough current to your power resistor and load. This is hard because I can trickle charge my slas on 41.7v and get full capacity with my bad boy and a lm338 chip.

The battery should be able to do more than 8 blocks sitting at that voltage so either your pack is out or the BMS. Any amperage charge amp at 52v should get you further than 8 blocks.

Cheapest first.

Test the charger on some SLA's or for a short period "like 5 seconds" on your LiFePo4 battery bypassing the BMS, remove the positive from the bms so you have no chance of a stray cap charging up giving you false readings. Does the charger go into full charge?

If not

Get a good charger and if the new charger doesnt still go into full charge mode, get a new BMS.

By now you should be able to charge the batteries.

If it still cant do more than 8 blocks do a running test. Meaning have the volt meter going when you are ridding and test the voltage slump perkins effect.

If the charger goes into top full charge mode when its connected to your lifepo4s with no BMS, get a new BMS or look to repair it.

 

[317537]

except the layout of the board, but i can explain what the stuff is on the board if you do that too.

Yes that would be cool.

 

[Subfightr]

Hi 317537, Im gonna call you #'s from now on.

The seller told me that if my input and output readings on the BMS were the same then the BMS is fine. I tested this in the video, hopefully I did it correctly, if not lemme know. Anyway, (assuming I did it correctly) the voltage result from the BMS input and output was the same.

Is the seller correct? Does this mean the BMS is good?

Regarding your helpful trouble shooting

"Test the charger on some SLA's or for a short period "like 5 seconds" on your LiFePo4 battery bypassing the BMS, remove the positive from the bms so you have no chance of a stray cap charging up giving you false readings. Does the charger go into full charge?"

I have single 12v SLA I could possibly test the Lifepo4 charger on, I'll figgure out a way to rig it up and let you know if the fully charged light comes on the Lifepo4 charger ( I assume that is what you are expecting?).

Regarding removing the positive wire from my BMS, I can't, the positive and negative wires on the BMS are housed in a single connector. You can see this in the video, perhaps I do not know what I am talking about just yet though.

I'll be back soon with pics of the 48v 5ah lifepo4 charger and it's guts

 

[dnmun]

the BMS is actually in the negative battery lead. they put the red positive battery lead onto the corner of that board so there is a convenient place to attach the charging lead to the positive terminal of the battery by attaching it to the red battery lead there on the corner of the BMS, and then they can bring the positive battery lead out close to the negative lead from the controller so the positive battery lead can run along the same path to the controller.

having the red lead there is not the end of the world, but you have to worry about shorting it out when you are working around it since the full battery voltage is across it.

the BMS should have very little voltage drop across it from the B- spot where the controller connects to the P- spot where it runs off to the negative terminal of the battery.the FETs have almost no voltage drop even under heavy load. the voltage drop across the shunt is millivolts.

i'm gonna go to the bookstore tomorrow and get a book on switch mode power supplies and maybe there is more info that will help me figure them out. if i can figure the book out.

 

[317537]

except the layout of the board, but i can explain what the stuff is on the board if you do that too.

Yes that would be cool.

Here is my charger pics Dnmun. Not too clear in focus but I hope they can help do us some learning.


View attachment front 2.jpg



View attachment 1

I added a parrallel resistor to the input of the power transistor to bump upthe current from 2.8 amps and I got 3.1 amps out of it now. My first attempt had me draining over 3.7 amps out of this charger but i got a little worried about the 400v cap and and switch mode transformer and I didnt need a 3.7 amp charger for my 24ah batteries.

The extra resistor is in the third picture on the far right on the back of the .6 power resistor.

Not too much heat comming from either of the transistors and Ive checked their specs. The irf6308 is rated at 9 amps and the 80c3 transistor for powering the switch mode is rated at 11 amps. The only thing that I could improve is maybe the filter cap at the main supply as it could get warm in summer and I am getting too much EMF from the switch mode. Any suggestions for improvements would be awesome. That reverse voltage protection diode is rated at 6 amp and gets a tad warm but this is to be expected.

 

[317537]

The 3.1 amp mod resistor. This feeds the main power input transistor and limits the current to the whole circuit to 2.8 amps now moded to 3.1 amps. The yellow purple gold gold is the resistor and this is a 4.7 1 watt ohm resistor. I added to bring the resistance down to allow more current to flow through the circuit.

View attachment 3.1 amp mod.jpg

UC3842N PWM IC controller.

 

[317537]

Here is a chip with the branding 358.

View attachment 1

I suspect this is a lm358 and is a dual opamp. My guess is its used for a summing amplifier but it can be used for a few things. I'm not entirely sure what this is used for yet. but Dnmun might shed some more light upon the workings of this switchmode transformer.


The irf630a mosfet.

View attachment IRF630a.jpg

This transistor is used to supply the battery with juice.

 

[317537]

Hi 317537, Im gonna call you #'s from now on.


I have single 12v SLA I could possibly test the Lifepo4 charger on, I'll figgure out a way to rig it up and let you know if the fully charged light comes on the Lifepo4 charger ( I assume that is what you are expecting?).

Regarding removing the positive wire from my BMS, I can't, the positive and negative wires on the BMS are housed in a single connector. You can see this in the video, perhaps I do not know what I am talking about just yet though.

I'll be back soon with pics of the 48v 5ah lifepo4 charger and it's guts

No do not test you charger on a single SLA, you may get away with three SLA's but even that could melt your charger.

 

[dnmun]

sub, he means that the voltage difference between the charger and the battery will blow up the charger. and even something as low as 3SLA will be too low.

way cool leslie, you are too far ahead of me. the output fet has the gate tied back to the drain i think through a reistor so when there is a battery out there, it turns on the FET, and there is a transistor between the gate of the output FET and the 358 which turns off the FET, i think that's how it works. you lucked out since i have been studying for 3 days. the 358 is dual opamp like you say. counting from lower left counterclockwise, 1out,1in-,1in+,grd,2in+,2in-,2out,Vcc

i will look at the traces to see exactly but i could see them running straight out to something, one output drives the led i bet along with turning off the output FET

what is the value of that resistor in parallel with the power resistor, orangeblackgold?

the little square device below the inductor is the phototransistor and the 3 terminal device tied to that little cap is the 3 terminal IC voltage reference that is tied to the phototransitor through a resistor bridge between ground and the charger + output, and the cathode of the three terminal reference is tied to the cathode of the input side of the phototransistor so that as the voltage or current sags in the output section then the photo transistor sinks the feedback voltage on the 8 pin oscillator, fb, which is pin 2 on mine, and pin 1 is grd. the other side of the input to the phototransistor is the current source to drive the led inside and comes off the regulated 5V on that side through a current limiting transistor.

the frequency of my pwm current controller is adjusted by a resistor to ground at pin4, and i looked at the resistor and the data sheet and mine oscillates at 220khz. look at the datasheet for my OB2269CP and they have the circuit schematic, much better than all the stuff i read in the switch mode power supply handbook because they are all dated and my charger is using surface mount parts which were developed in the last year or two. but the smps design handbook by billings was sold out. ozcad just had a thread on gatesource capacitance and i posted up some stuff on there about the miller capacitance too that billings talked about in his book 'switching power supply design' pressman, billings, morey. i think there may be a limit to how much power you can get through the inductor from the input to the output, but was thinking of hacking the power resistor just like you, and building up the traces that carry current.

did you see my notes on the other charger thread? i like that you are doing this, i have learned a lot of electronics common sense in the last few days, but not yet able to figure out how to fix them or decipher how they failed. just ordered some chargers from ping so i can learn on his. if anyone has a dead ping charger lemme know and we will compare to a new one and try to fix it, or i will buy it to tear apart to learn on.

http://endless-sphere.com/forums/viewtopic.php?f=14&t=13060

 

[Capripower]

Hi everyone, I finally got to work on my battery pack and it has no damage from the silicon there are 4 total cells that are off of all the 32 cells I will attach pictures 2 in the very back [ opposite bms ] are the worst 1.09 and 1.10 v
2 more to the front are only 0.07 v[ behind 3.20 ] the rest which is at 3.27 v
also the total voltage of the pack before the bms is 50v after the bms it is 48.1 v ? does this matter ?
how can I resurrect the 2 low [ 1.09 ] cells ?
Thanks Felix

 

[Capripower]

And I also measured the voltage on my charger I received with my headway packs and plugged it in without the battery connected, it pulses and there is a clicking noise and the volts are 22.9 to 24 volts any idea why ? does it have to be connected to the pack to have full voltage [ 57v] ?
Thanks for any help
Felix