Finally got my first LiFePO4 from china.. what now ?

[carl2.0]

I finally got my first Lithium pack . A generic LiFePO4 48V 15ah pack made using 16 40152 cells. I brought it home atd the first thing I did was to cutthrough the duct tape and take a look to confirm the cells and the wiring. Next I checked the voltage, around 51V and then checked each cell (voltages between 3.2 - 3.3V). I gave it a charge for 4 hours (came with a 4A 48V charger) then checked the voltage (57V), some cells around 3.6 and a few around 3.4V one as high as 3.745V.

Soo my questions are:

what should the charged voltage of this pack be roughly ?
what should be the average voltage of a charged cell be ?
What else should be done with a new LiFePO4 pack before I put it on my ebike?

I have a feeling I should look into buying a separte 3.2V charger to balance the few that are significantly lower (3.4V) What do the experts think

 

[biohazardman]

I finally got my first Lithium pack . A generic LiFePO4 48V 15ah pack made using 16 40152 cells. I brought it home atd the first thing I did was to cutthrough the duct tape and take a look to confirm the cells and the wiring. Next I checked the voltage, around 51V and then checked each cell (voltages between 3.2 - 3.3V). I gave it a charge for 4 hours (came with a 4A 48V charger) then checked the voltage (57V), some cells around 3.6 and a few around 3.4V one as high as 3.745V.

Soo my questions are:

what should the charged voltage of this pack be roughly ?
what should be the average voltage of a charged cell be ?
What else should be done with a new LiFePO4 pack before I put it on my ebike?

I have a feeling I should look into buying a separte 3.2V charger to balance the few that are significantly lower (3.4V) What do the experts think

Soo my questions are:

what should the charged voltage of this pack be roughly ? Generally 3.65 per fully charged cell multiplied by 15 cells for a 48V pack gives one 54.7V. Headways slightly higher from what I have read.
what should be the average voltage of a charged cell be ? Nominal voltage for the LifePO4 cell is 3.3V although most will hold higher if in good shape.
What else should be done with a new LiFePO4 pack before I put it on my ebike? Some will cycle with a light load several times others just balance the pack and ride the bike.
A .2V difference in cell charge should be watched carefully so it does not get worse.

I have a feeling I should look into buying a separate 3.2V charger to balance the few that are significantly lower (3.4V) What do the experts think[/quote]
You need something to keep the pack balanced at near the manufactures spec. Cheap single cell chargers do not last long from my experience. Balancing by single cell and by hand is slow but some packs do not need it done often so it is acceptable. Get a good charger. Other packs need done every couple of rides so you would be better off with a balancing charger or BMS.

 

[agniusm]

I finally got my first Lithium pack . A generic LiFePO4 48V 15ah pack made using 16 40152 cells. I brought it home atd the first thing I did was to cutthrough the duct tape and take a look to confirm the cells and the wiring. Next I checked the voltage, around 51V and then checked each cell (voltages between 3.2 - 3.3V). I gave it a charge for 4 hours (came with a 4A 48V charger) then checked the voltage (57V), some cells around 3.6 and a few around 3.4V one as high as 3.745V.

Soo my questions are:

what should the charged voltage of this pack be roughly ?
what should be the average voltage of a charged cell be ?
What else should be done with a new LiFePO4 pack before I put it on my ebike?

I have a feeling I should look into buying a separte 3.2V charger to balance the few that are significantly lower (3.4V) What do the experts think

Soo my questions are:

what should the charged voltage of this pack be roughly ? Generally 3.65 per fully charged cell multiplied by 15 cells for a 48V pack gives one 54.7V. Headways slightly higher from what I have read.
what should be the average voltage of a charged cell be ? Nominal voltage for the LifePO4 cell is 3.3V although most will hold higher if in good shape.
What else should be done with a new LiFePO4 pack before I put it on my ebike? Some will cycle with a light load several times others just balance the pack and ride the bike.
A .2V difference in cell charge should be watched carefully so it does not get worse.

I have a feeling I should look into buying a separate 3.2V charger to balance the few that are significantly lower (3.4V) What do the experts think

You need something to keep the pack balanced at near the manufactures spec. Cheap single cell chargers do not last long from my experience. Balancing by single cell and by hand is slow but some packs do not need it done often so it is acceptable. Get a good charger. Other packs need done every couple of rides so you would be better off with a balancing charger or BMS.[/quote]

For LiFePO4 48V system is 16S, 36V 12S, 72V -24S
LiFePO4 nominal - 3.2V LiFePO4 A123 cell nominal - 3.3V
Fully charged, hot of the charger should be 58.4V, then leaved it settles at lower voltage.

 

[dogman dan]

If this thing has a bms, then give it the typical new pack "break in" procedure. Mostly it consists of keeping rides short, and in between rides leave it on the charger at all times. After a few cycles, and a few overnight charges, you should see the pack balanced then. Expect to see about 3.5-3.8v per cell. During the balancing process, a cell can go as high as 4v though. Then after some time, the bms will pull it back down to 3.6-3.7v.

If you don't have a bms, then getting an RC lipo charger would be a good way to occasionally balance the pack, using it as a single cell charger on the lifepo4 setting.

 

[carl2.0]

Thanks for the advice guys, this lifepo4 pack cost me some serious money so i just wanna make sure it lasts s. Ill start to break it in over the wkend

 

[999zip999]

Do answer ALL question that people ask of you. Do you have a BMS that came with the pack ? Where did you buy the pack ?

 

[carl2.0]

ith the pack ? Where did you buy the pack ?

The battery came with a BMS located outside the the pack in a box. a 48V 30A BMsS is what I requested.. have yet to confirm.

The pack was purchased on special order from asian-resources.com. It looks just like this, with a 4A charger

 

[dogman dan]

Good, then given enough time, the bms should keep the pack balanced. The way the bms works, it's very slow, and needs to have the charger connected overnight to finish balancing the pack if it is very much out of balance. It can even take days or weeks if it's severely out of balance.

Normal use though, just leave it on the charger overnight any time you drain it completely. The green light comes on, the bms drains some high cells, then the red light comes back on very briefly. So it has to be still plugged in to get those short top ups that are part of the process.

 

[zoom2136]

How do you like this pack so far?

 

[dnmun]

I finally got my first Lithium pack . A generic LiFePO4 48V 15ah pack made using 16 40152 cells. I brought it home atd the first thing I did was to cutthrough the duct tape and take a look to confirm the cells and the wiring. Next I checked the voltage, around 51V and then checked each cell (voltages between 3.2 - 3.3V). I gave it a charge for 4 hours (came with a 4A 48V charger) then checked the voltage (57V), some cells around 3.6 and a few around 3.4V one as high as 3.745V.

Soo my questions are:

what should the charged voltage of this pack be roughly ?
what should be the average voltage of a charged cell be ?
What else should be done with a new LiFePO4 pack before I put it on my ebike?

I have a feeling I should look into buying a separte 3.2V charger to balance the few that are significantly lower (3.4V) What do the experts think

you should charge the pack up past the 58.4V full charged level. the BMS will balance the cells usually down to around 3.6V for lifepo4. you can measure the cell voltage on the BMS where the sense wire cable connects to the pcb.

if the BMS does not push all the cells up to and past the 3.6V level on a new pack then you can worry about it then but that is not likely to happen to new battery. the single cell charger is for people who have to build a new pack from new cells. you should not be using it for a new pack.

 

[999zip999]

If you have the pack open you can just put a flashlight blub or a signal blub from a car and bring the the 3.75v cell down just like the bms does and the charger will turn on and start charging the other lower cells. 3.4v to 3.45v is getting pretty full. From 3.5v to 3.65v goes up fast. Over 3.7v and that cell will read higher at a faster rate when charging. Meaning 3.5 is pretty full and getting to 3.65v goes very fast.
It's best to start out balance and leave on the charger for so time so the bms can balance the pack. A single cell charger like voltpheaks lifepo4 mine stop at 3.6v and 3.65v