bad lifepo4 pack

[kentlim26]

very interesting!! handphone can be also used for lifepo4 battery . thank you for input knowledge. i have a ES friend here, was asking me where to buy the single cell charger. i look everywhere in the ebay, now is no more selling. i suggest to him, look for ypedal had try a single charger.

kentlim

 

[amberwolf]

Just in case any of it helps you, this is my recently-started repair of an older Vpower/CammyCC pack:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=22750&start=0
which details some construction problems and other issues you might encounter.

Ypedal's page
http://www.ypedal.com/cammycc/Index.htm
on his pack repair might help too.

I think using the single-cell charger is your fastest way to fixing the pack, as others have suggested. I"m mostly not doing it that way because i want to see how well the system can fix itself and how quickly, but I am not concerned with time on mine.

 

[limey2]

i was wondering how long does it usualy take to bring a string of 18 cells up from 3.2v to 3.6v? only i have had a string on charge for about 5 hours and it has only moved up to 3.3v is that ok or should i stop ?
limey2

 

[limey2]

limey2 can you read carefully what people telling you next time please ? i was the first to tell you to use a single charger and 15 post later ypedal had to tell you again the same thing

yes sorry but i had sugestions cuming at me like a machine gun and the topic was mistakenly open in two forums and so it got a bit confusing.

 

[Ypedal]

i was wondering how long does it usualy take to bring a string of 18 cells up from 3.2v to 3.6v? only i have had a string on charge for about 5 hours and it has only moved up to 3.3v is that ok or should i stop ?
limey2

cell phone chargers are like 1 amp, so 1 ah per hour.. keep going until you reach 3.6 to 3.8

 

[limey2]

i was wondering how long does it usualy take to bring a string of 18 cells up from 3.2v to 3.6v? only i have had a string on charge for about 5 hours and it has only moved up to 3.3v is that ok or should i stop ?
limey2

cell phone chargers are like 1 amp, so 1 ah per hour.. keep going until you reach 3.6 to 3.8

do you think i should do 1 cell at a time or keep going with 18 cells at once. i would like to do 18 at once so that i dont have to disturb the spot welds. but is a cell phone charger going to be fast enough ?

 

[Ypedal]

do the group... all cells in parallel act like one bigger cell.

 

[Ypedal]

edit to add " if you have a bad cell in the group, it will be aparent after you fully charge the group and the pack sits for a while, as the bad cell will keep draining capacity from the group over time.. ... don't yank the spot welds until you absolutely have to.. "

 

[limey2]

this may take some as i said so in the meantime i thought you might like to see the bike that this battery was bought for.

not a stealth

 

[USAEBIKECO]

Vpower is a good company. On par with ping in my opinion. If the battery cut out after 3 miles you need to balance the cells.

Think that the battery has been in transit to you from China for weeks slowly losing power. When you get a new battery leave it on the charger for a day. Yes an entire day.

There was a big debate about breaking in a lifepo4 pack and its true, you need to break in the pack. The pack needs several shallow discharges before your ready to drain it. I hope this helps.

 

[dogman dan]

:lol: :lol: :lol: :lol: vpower = Ping

 

[limey2]

Vpower is a good company. On par with ping in my opinion. If the battery cut out after 3 miles you need to balance the cells.

Think that the battery has been in transit to you from China for weeks slowly losing power. When you get a new battery leave it on the charger for a day. Yes an entire day.

There was a big debate about breaking in a lifepo4 pack and its true, you need to break in the pack. The pack needs several shallow discharges before your ready to drain it. I hope this helps.

i think a good company would take rather more care when building battery packs ie better insulation between conecting tags and cell walls.
if youv'e ever taken a battery drill apart you will know what i mean proper rubber or plastic washers to keep the tags away from the cells. also good thick srink wrap and an outer rigid plastic case on even the cheapest battery ,not cheap flexible duck tape.

 

[mihai_atanasiu]

The problems with vpower packs are from the refurbish A123 cells; I also bought one in the summer and is still on the test board;
Like yours, form the first time the pack was unbalanced; only 4 or 5 Ah drained after a few cycles and a bad cell; I asked wpower guy and he send me a new one after some emails and 2 weeks of discussions; for free this new cell arrive after 2 weeks; overall about five weeks; in this time the pack was on the test board with opened; mean time I red about wpower and about Ping batteries and decided to buy a 36V 20AH Ping battery that was good from the first time;

after I received the new cell from vpower I made the modifications and put that new cell; sorry, I forgot to tell you: with the ping battery I also bought an extra BMS for this vpower battery because the original BMS was too big and I think a crap also;

I charged each cell separately with an RC charger, I installed the signalab BMS and do a final charge with the vpower charger; after one hour the leds start to blink one by one except one cell; I said: never mind let's do a discharge with car bulbs and a watt meter; about 12 AH draining from the battery; I made another two charge and discharge cycles; the same problems: one cell not fully charged and only about 12 AH discharge; I decided to make a break; next week end I said let's do it again; I said let's charge that low cell with the RC charger;

but SURPRISE ! the cell was completely discharged: zero volts;
I was very angry and not able to talk again with vpower guy; after some weeks of thinking and reading this forum I decided to do something; I decided to reduce the capacity of the pack by cutting two cells from each string: each string has 18 cells thats about 19.8 AH and decided to reduce it to 17.6; from 18 cells to 16 cells;

It wasn't an easy job to cut the nickel tabs but with a fine cutting tool I did the job; I collect 22 cells from the 11 good strings and
pick 16 and made the "new" string; everything was good, I glued the cells, made the solders and repack the whole battery;

Now all the cell was full charged; all the leds from the BMS became red; I put the bulb discharge (3 pieces of 12 V car bulbs) and
drained about 13.5 AH; SURPRISE again ! another cell was the problem; in this moment another cell go bellow 2.5 V and the BMS cuts off the power; I tried to charge the cell with the RC charger but only about 14 AH charge;

that's my sad story with the vpower battery;

mean while everything was very good with the ping battery; after three lite charge and discharge cycles I was able to drain about 19 AH from it;

now I ordered 16 cells welded from ebay from another supplier and waiting for them; hope I can do something; I will be glad if I can drain about 15AH from the theoretical 17.6 AH;

I any one can give me some tips please tell me;

 

[limey2]

The problems with vpower packs are from the refurbish A123 cells; I also bought one in the summer and is still on the test board;
Like yours, form the first time the pack was unbalanced; only 4 or 5 Ah drained after a few cycles and a bad cell; I asked wpower guy and he send me a new one after some emails and 2 weeks of discussions; for free this new cell arrive after 2 weeks; overall about five weeks; in this time the pack was on the test board with opened; mean time I red about wpower and about Ping batteries and decided to buy a 36V 20AH Ping battery that was good from the first time;

after I received the new cell from vpower I made the modifications and put that new cell; sorry, I forgot to tell you: with the ping battery I also bought an extra BMS for this vpower battery because the original BMS was too big and I think a crap also;

I charged each cell separately with an RC charger, I installed the signalab BMS and do a final charge with the vpower charger; after one hour the leds start to blink one by one except one cell; I said: never mind let's do a discharge with car bulbs and a watt meter; about 12 AH draining from the battery; I made another two charge and discharge cycles; the same problems: one cell not fully charged and only about 12 AH discharge; I decided to make a break; next week end I said let's do it again; I said let's charge that low cell with the RC charger;

but SURPRISE ! the cell was completely discharged: zero volts;
I was very angry and not able to talk again with vpower guy; after some weeks of thinking and reading this forum I decided to do something; I decided to reduce the capacity of the pack by cutting two cells from each string: each string has 18 cells thats about 19.8 AH and decided to reduce it to 17.6; from 18 cells to 16 cells;

It wasn't an easy job to cut the nickel tabs but with a fine cutting tool I did the job; I collect 22 cells from the 11 good strings and
pick 16 and made the "new" string; everything was good, I glued the cells, made the solders and repack the whole battery;

Now all the cell was full charged; all the leds from the BMS became red; I put the bulb discharge (3 pieces of 12 V car bulbs) and
drained about 13.5 AH; SURPRISE again ! another cell was the problem; in this moment another cell go bellow 2.5 V and the BMS cuts off the power; I tried to charge the cell with the RC charger but only about 14 AH charge;

that's my sad story with the vpower battery;

mean while everything was very good with the ping battery; after three lite charge and discharge cycles I was able to drain about 19 AH from it;

now I ordered 16 cells welded from ebay from another supplier and waiting for them; hope I can do something; I will be glad if I can drain about 15AH from the theoretical 17.6 AH;

I any one can give me some tips please tell me;

the only tip i can give you is dont buy vpower batteries and tell as many people as you can the same !

 

[limey2]

its bad news - have now been trying for two days to bring the bad bank up by charging each 18 cell string but no luck,they dogedly stick to 3.3v. i think i will have to strip that bank down and charge each cell individualy to find the bad cells. that means there must be at leased 6 bad cells, one for each 18 cell string, and maybe more.
limey2

 

[dnmun]

i think you will regret that. how much current does your single cell charger put out, i assume you are measuring it as it fills the cell. does the charger even work?

 

[limey2]

i think you will regret that. how much current does your single cell charger put out, i assume you are measuring it as it fills the cell. does the charger even work?

have tried two chargers both of wich i monitored.i presume they put out enough for a single cell ? i do have a bosch " iaxo " drill fast charger which has a 3v lithium cell but the charger pumps out 10v.

 

[dnmun]

current, what was the current you measured out of the charger? how many amp hour pack is it?

 

[amberwolf]

The problems with vpower packs are from the refurbish A123 cells; I also bought one in the summer and is still on the test board;

If these things are really made from A123 cells I'd be surprised; I seriously doubt I could pull those kinds of currents from the ones in my pack.

I think there are more serious problems from the way they are handled and assembled by whoever builds the packs at Vpower/CammyCC, and that a lot of the dud cells in them are probably caused by physical damage or electrical misapplication at one point or another in the process.

There probably are some just plain bad cells, but I really think more problems are assembly issues.

 

[Ypedal]

limey.. if you have a few cell phone chargers on hand, you can put them all to work at the same time, speeds up the process... look for the fine pring on the label, it will say how many amps it puts out...

taking the spot welds off is an absolute last resort...

 

[amberwolf]

Yeah, if you do have to take the cells apart, do NOT break the welds, but instead cut the nickel strips in between the cells. I already made that mistake fixing my pack, and ended up being very lucky in being able to solder to the cells, but there is no guarantee that your cells are solderable like mine (which are an older type).

If you have some Fiskars brand scissors, they are sharp enough and tough enough to easily cut the nickel strips, as long as the blades are thin/narrow enough to fit in the small space available between the nickel and the cells.

A Dremel or similar will work too, but you must be very careful not to cut beyond the tab and hit the cell.

 

[dnmun]

do not do any of this until you can show you actually are charging these cells you say are stuck at 3.3V which is where they usually stay until they collect enuff charge.

you still have not said how much current your charger puts out so there is no way to know how long it will take to charge the cells. cutting it apart is just useless and makes it harder to repair if there is even something wrong, which has NOT been proven, imo.

 

[limey2]

do not do any of this until you can show you actually are charging these cells you say are stuck at 3.3V which is where they usually stay until they collect enuff charge.

you still have not said how much current your charger puts out so there is no way to know how long it will take to charge the cells. cutting it apart is just useless and makes it harder to repair if there is even something wrong, which has NOT been proven, imo.

remember the time diference i may not answer imediatly, i will check today. but aren't all cell phone chargers approx. the same current output.

 

[limey2]

ok have checked the output of charger it is 800ml. amps @ 6v.
Each 18 cell string is approx 2amph.
is that 2 1/2 hour charge time or have i got that wrong ?
have just dicovered a quick way to connect bare wires to pack - with magnets! they have to be the rare eath type or they would not be strong enough. see pic.

 

[dogman dan]

Brillaint with the magnets. Be paitent and keep charging. They are stuck at 3.3 because it takes a loooooong time to bring up a big string of cells with a low output cell phone charger. A flat discharge curve = a flat charging curve.

You can also take a 12v lightbulb like a turn signal and discharge some of the higher strings one at a time, bringing the whole pack down to 3.3v. Then put it back on the regular charger. Eventually you will get er balanced.

This pack is not dead! Just out of balance and needing break in. SO DON'T START CUTTING IT UP!