How to take this Lifepo4 pack apart
- Thread starter cai876
- Start date
dogman dan
1 PW
Whatever you do, leave as much of the spot welded strips in place as possible. Heavy scissors or tin snips should be able to cut the strips where connections are made between cell groups.
I can see some of those strips in the pic, where a short strip bridges from a bunch of negative terminals to a bunch of positive terminals.
Once broken down into 40 ah parallel strings of cells, you can decide where to cut for 15 ah, or whatever you are planning on.
Looks like a ton of work, even more if some of those cell groups are no good. Have fun.
I can see some of those strips in the pic, where a short strip bridges from a bunch of negative terminals to a bunch of positive terminals.
Once broken down into 40 ah parallel strings of cells, you can decide where to cut for 15 ah, or whatever you are planning on.
Looks like a ton of work, even more if some of those cell groups are no good. Have fun.
dnmun
1 PW
these batteries have caused fires when the parallel strap running across the anode end short out to the case where the strap passes over the thin plastic insulation on the case where it surrounds the anode button so .we recommend people avoid purchasing these Vpower packs. no matter how cheap, a fire is more expensive than any battery
dnmun
1 PW
if you look at the anode you will see what i was talking about. this pack is not the Vpower pack but it is also built without the insulating cardboard shield under the straps.
if your strap cuts through the blue plastic around the anode it is only limited by the white plastic under that end so if that cuts through and the strap contacts the case then the entire row will discharge through the short. the best outcome is if it burns the strap open immediately and doesn't discharge all the energy held in 30Ah of those individual cylindricals.
if your strap cuts through the blue plastic around the anode it is only limited by the white plastic under that end so if that cuts through and the strap contacts the case then the entire row will discharge through the short. the best outcome is if it burns the strap open immediately and doesn't discharge all the energy held in 30Ah of those individual cylindricals.
dnmun
1 PW
sure, you can take it apart and build a new battery with it. just consider how to prevent the straps from cutting into the plastic insulation on the anode end. some battery makers use a cardboard spacer on top of the case.
your battery looks like it is two 15Ah packs tied together at the cell level by those straps running up and down the sides. when you cut those open then you will have two 20S15Ah packs.
your battery looks like it is two 15Ah packs tied together at the cell level by those straps running up and down the sides. when you cut those open then you will have two 20S15Ah packs.
Hillhater
100 TW
cai876 said:
...Very carefully !! :wink:
dogman dan
1 PW
Yeah, snipping the side strips could be the best starting point. When using the snips to cut the tab strips, you will need to be careful what you let touch the snips as you cut. Don't let the snips touch positive terminals, and cut into the plastic insulating the negative case of the cell. Careful also, with any long strips, don't let them touch the other end of the cell group. Maybe get some tape or something on them once you cut those longer strips.
In case you didn't get what was being talked about, the entire can is the negative on metal cells. Not just the end.
In case you didn't get what was being talked about, the entire can is the negative on metal cells. Not just the end.
cassschr1
10 kW
looks like this is two batteries,.......15s6p. How are they getting 40a capacity? Unless there's four packs.
To the OP..what size battery are you after?
To the OP..what size battery are you after?
40ah is just what it was described as being when it was sold to me on ebay. I bought it as a bit of an impulse buy. I have a 48v 10ah battery at the moment on a gng v1 setup. But I am aware that I am on the 2c limit with the 20amp draw that the gng uses. I am after more power so I wanted some new batteries. I got this on ebay for £270 and didnt think the whole thing through properly. The idea was to either stick to 60v and maybe split the pack in half or up the voltage and see what kind of ah I can end up with.
I have done electronics and physics at A level so have some experience with soldering and I understand electricity but havent got experience with lithium batteries.
I have done electronics and physics at A level so have some experience with soldering and I understand electricity but havent got experience with lithium batteries.
dnmun
1 PW
like i said there are two separate 20S packs one on top of the other and connected in parallel at the cell level by those long straps running down the sides. if you cut those straps you will have two 20S packs.
if you wanted to use them together and put them on different sides in back then you can do that and reconnect them in parallel by soldering some jumper wires across from one pack to the other, connecting the straps again so the cells are all in parallel. you do not need large wire to connect them in parallel but the main cable from each end of the pack should be substantial. 10AWG is best, and connect the two B- wires together at the B- spot on the BMS and then connect the two red wires for B+ to the controller positive.
the P- spot on the BMS goes to the controller negative. that is only one wire, again at least 10AWG.
if you wanted to use them together and put them on different sides in back then you can do that and reconnect them in parallel by soldering some jumper wires across from one pack to the other, connecting the straps again so the cells are all in parallel. you do not need large wire to connect them in parallel but the main cable from each end of the pack should be substantial. 10AWG is best, and connect the two B- wires together at the B- spot on the BMS and then connect the two red wires for B+ to the controller positive.
the P- spot on the BMS goes to the controller negative. that is only one wire, again at least 10AWG.
wb9k
10 kW
The real danger with this pack (and probably the reason it can start fires) is that there is no fusing mechanism built into the weld straps. This means a shorting event across any two given points on the pack will be allowed to continue longer than it would were a fuse present in the current path. This means rapidly elevating temperatures on the weld straps and probably combustion of the material the pack is wrapped in, even if the cells don't blink at what's happening. The way to make a pack design like this safe is to put mechanical neck-down fuses into the weld strap at every cathode or anode terminal in the pack (if the can is "live" put the fuse on the same side that is common to the can--the cathode if using A123 cells.) This of course leads to a need for better mechanical support for cells so the neck-downs can't bend with vibration.
I've mentioned a large cache of used cells at Sybesma's Electronics a number of times here. Lots of good material and lessons there for an aspiring builder. He (Hank Sybesma) has all the old Hymotion inventory too. Lots of very nice 14/28 Volt modules with 26650's in 11P, all new older stock. Storage conditions have not been perfect for preserving calendar life, but they have been very good.
Sorry--don't want to sound like an advertisement, but it really is germane to the OT.
I've mentioned a large cache of used cells at Sybesma's Electronics a number of times here. Lots of good material and lessons there for an aspiring builder. He (Hank Sybesma) has all the old Hymotion inventory too. Lots of very nice 14/28 Volt modules with 26650's in 11P, all new older stock. Storage conditions have not been perfect for preserving calendar life, but they have been very good.
Sorry--don't want to sound like an advertisement, but it really is germane to the OT.
arkmundi
10 MW
Every battery is a fire hazard if not treated with due precaution. Shorting next to skin can hurt, shorting next to plastics or other flammable material can cause a fire. The precautionary principal calls for using the right tools, skill and care. The trick will be in cutting the conductor strips apart without shorting. Since you'll be using tin-skips or similar cutters, the metal can bridge an arc. Compensate on the side of caution.cai876 said:Is this battery a fire waiting to happen?
999zip999
100 TW
Here is a pic of what Dmumn was talking about![HY5LP[}J3C`}BTVG0B@]@NM OSN.jpg](https://endless-sphere.com/sphere/data/attachments/64/64192-57af775310e4987ef535c8c1d8498959.jpg "HY5LP[}J3C`}BTVG0B@]@NM OSN.jpg")
chilledoutuk
100 W
I would do as dogman suggested cut the tab welds but then use the Dr Bass technique of folding the Nickle strip so that when you solder a copper bar a forced gap is created between the can edge and your bar.
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