48v lifepo4 charger = 55v need repair help

[dnmun]

Very impressive Les/#'s Good for you man, that is awesome.

ES is awesome an place to put your thoughts into action and to share learning about electronics. 6mths ago I would of been lost. I have been doing low level electronics for years and years. I figured its time to get my hands dirty.

Dnmun has been a great source of information to me in this pushing me to learn a little more.

i am trying to talk dogman into fixing his charger too, he sent me a picture, maybe he will start a thread to fix it, does it look like yours?
i can't upload his pictures, maybe he will post them up.

i think subfighter has the same board, not sure.

 

[Capripower]

Hello again I finally understood or so I hope, the pic. show the pack top and bottom with the cells numbered and what I did last night was I swapped out cell pair 15 from my other battery and hooked it up to the charger and everything behaved normal so I think? the charger voltage was 51.3 and blinking red this morning I walked in and the led was green with even glow but the voltage was still at 51.3 ? Now why would that be ? It should be at 57 ?
When you look at the second picture there is a burn mark on the connecting plate,[ for cell 14 and 15] in the early stages the pack shorted out with the bike rack and created some heat could that be the reason for the cell pair to be damaged ?
the cell sensing wire look fine
Here are the readings of each cell-pair
1- 3.21
2- 3.2
3- 3.19
4 - 3.18
5- 3.18
6 - 3.2
7 - 3.22
8- 3.18
9 - 3.21
10- 3.2
11- 3.19
12- 3.19
13- 3.20
14- 3.18
15- 3.27 cell pair #15 came from my other headway battery and was at 3.27 v !
16- 3.20 any other information that will be helpful please let me know and THANKS for the help
I did order 4 new cells to have all two packs working again since I can not charge a single cell or test it .

 

[Capripower]

just connected the charger and it is blinking red again so its charging will see what happens in a few h
Felix

 

[dnmun]

the two low cells, 2.09 and 2.10V were on the end where that connector plate shorted out originally? if the sense wire there was broken then the BMS would have stopped you.

you have the headway charger with all chinese writing and the two leds in the top? with the chinese characters for labeling? 220V printed on the back and everything chinese?

did it ever charge up to 58.4V originally?

you had mentioned on one of the previous threads that the pack was cutting out before your son wrecked it. is this the pack? with the 2.1V cells?

 

[Capripower]

Yes I have the original headway charger with the chinese writing and 220 v on it
Yes it originally charged up to 58.4 or so and the low cells I replaced where 1.5 and 1.5 v and they where cell pair # 15 in the above picture. I used cell pair 8 from the other pack and that was the battery pack that had the really low cells #9 was 1.1 and 1.09 v .
the sense wires are all intact
the early shut down happened with each battery pack and it shut down first at about 48 V and later at 50v could this be controller related ? we have a 35a analog xlyte controller
I did call evcomponet today and the guy I talked to thought 51.3 v is what the pack should charge up to and that was the rest voltage of the battery when it is full ?
Thanks for your help Dnmun

 

[dnmun]

no, it should charge up to the same original 58.4V.

did you order the 4 new cells from evcomponents?

i think your BMS should not have let those cells get so far out of balance. the headway BMS is better than that so it could have been damaged before the wreck and those cells were just not balancing all this time.there is not a good reason for #8 to go out. i can see how your #16 could have been shorted out, but it seems like it may have been 15, shorted through the frame, that may be the case with the #8 on the other pack too.

the only thing to do is install the new cells and charge it up to 58.4V. measure the cells as it charges up and see if some are slow and never make it.

 

[317537]

Between 51v and 52v is ok for cells on float mode. 55v is what comes from the charger with no resistance from the pack. You will get some voltage loss when when its connected and you will see the pack voltage drop a little more when you disconnect it from the charger.

Your problem was indeed the dead cells and you may find they better balance over the time you use them. Keep check on those replaced cells though and figure a way so you can test them regulary as the BMS still may of been the root of the problems to begin with. The BMS may not be doing its job both during charging or discharging on those cells.

You should get a good idea when one cell is out in the pair if that cell pair is discharging faster than another cell pair. One cell in the pair will not be as good as another. If this is the case pull cell pair thats bad and separate them and my guess is the lowest cell from the pair is the problem. Yon use cell phone charger or anything rated at 3.6v you could even use one thats rate above the cell charge rate and add diodes to one wire to achieve a .7v drop on each diode.

One schokey diode =.4 volts drop and
one rectifier diode = .7v drop

If your mobile charger is lipo, diodes wil do fine.

I have a motorrola charger rated at 3.6v Would take ages to charge them, but will do to find out.

I would get myself a 6v 1 amp transformer and use a LM317t reg and build my own cell charger. LM317t are cheaper than chips and you can build it to adjust the voltages. One 5 k trimpot a couple of caps and a load resistor and your are in businness.

Your cell charger would cost about $20 tops, and you could have it so you could switch a resistor to keep them in float. Then build a circuit to do this automatically.

 

[317537]

Does blinking red mean charge complete?

As it may of got to full charge being 58v or so when you were asleep and went into float mode when you awoke.

 

[Capripower]

Hey thanks guys for the good info
Yes I ordered the 4 new cells from evcomponents do to arrive in 2 weeks or so
so after I hooked up the charger again with red light blinking [ indicating it is charging ] voltage at 51.3 it is just sitting
there without any change so I will have to invest money to buy a better meter to measure amp flow or something that will tell me if the charger is putting anything out !
I am also checking if the cells are all the same still in a min. or so wile I am having some coffee
Leslie
I will build this charger you are describing although I will need some help, something like this will present a challenge for starters where will I find some of the components ? we only have a radio shack near by and what are caps ?
so if your are willing to help I will do it !!
Thanks
Felix

 

[Capripower]

checked voltage on the pack and there is no significant change voltage is 1 hundreds up or down
cells 7 / 8 / 9 / 11 / 13 / are down
cells 10 / 16 / are up
thanks
Felix

 

[dnmun]

your charger should charge the pack back up to the 58.4V. there is not need to build a new charger or worry about stuff you don't have control over.

can you put your ammeter in line with the current so you can measure the current coming out of the charger? you may need to think about doing this if it doesn't appear to charge.

if it doesn't charge up to 58.4V or even change voltage and stays blinking red then it is likely that there is either something wrong with the charger or the BMS has stopped the charge because the comparator has detected overvoltage on one of the cells.

 

[Capripower]

the voltage an all the cells are in a range which will require further charging so I think it is the charger or the bms
how do I correctly measure amperage ? meter in line with + or negative ? 10 a range is all I have
What would happen if i used the battery the way it is and drain the volts down to maybe 45 and then try to recharge ?
Thanks
Felix

 

[dnmun]

sure you can cycle it, but if your charger used to put out 58.4V, then it should still do that.

 

[Capripower]

I hooked the battery up with 51.3 v and use it with no load it took about 2 h till it shut down at 44.7 v
then I measured the individual cells and there was an interesting discharge pattern !
1- 3.14
2- 3.01
3- 3.01
4- 2.99
5- 2.49
6- 3.10
7- 3.16
8- 2.46
9- 3.15
10- 3.12
11- 2.92
12- 3.07
13- 3.07
14- 2.47
15- 3.26
16- 3.11
the charger revealed it is dead no amp flow on red or black !!!
so where do I buy a decent charger ? it probably never balanced the pack and this is the result ?
any help is welcome thanks
Felix

 

[BLUESTREAK]

TRY (RECHARGEABLELITHIUMPOWER.COM) ANDY will take care of your needs.

 

[dnmun]

your headway charger is dead?

i have taken them apart already. if you wanna try to fix it, do you have a voltmeter? you need to have dry skin too so when you brush up against the 354V it doesn't do more than tingle.

did your red power led come on? the flashing red for charging? final green?

 

[Capripower]

Hi dnmun
I measured amps before I did the test and there was 0.00 amps after the test it still was 0.00 amps.
the red light of the charger was on, the 2end one was blinking and glowed very dim green after 10 h when I tried to charge the battery after the test { my amp meter could also not have been working]
so I assume the cells have fallen out of balance because the charger was malfunctioning !?
dnmun I will pm you with more info thanks for the offer and all the help
Felix

 

[dnmun]

one of the headway chargers i worked on would not really charge either, but it sounds like the charger is your only real problem. those low cells will pull up when you charge them up and that will get you out of the low voltage cutoff LVC which has been shutting down the BMS.

is that your only charger? your other low cells may actually be ok. just needed charging.

 

[Capripower]

It was my only charger so I am looking into getting a spare
Felix