Need experienced advice to let me know what to expect from those cells in real life

[sharinginfos]

Hi
i found a cell that is prismatic and light (not sure if plastico or aluminium encassed at 0.2kg) it is called BPS-LFP7AHP.
my need is to create a light 48v lifepo4 battery to go up hills without long distance. 7amphour seems ok but i wonder if they deliver continous amps as mentionned.
At the moment i have a xiongda 2 speed hub(asks 20apms) but i have read that we should build a battery thinking about possible motor improvements(maybe a BBs02 later(asks 18amps). is 30Amp continous a good thing to aim at to start with ?

The stat of the cells on website are different from the testing report benergy sent me. The complete report is in attached files . below also a graphic they sent me about 410amp discharge curve. the webpage wich they say is not updated is https://www.benergytech.com/Lifepo4-Battery-3-2V-7AH-Prismatic-Cell-pd44615319.html

Does the testing report looks like good quality cell? Can i expect them to deliver 7C 50amps continous discharge as they write? or what would it look like in real live? it says standard discharge 0.5C is 3.5Amp. is this suspicious?

what to expect? any comments or advice is welcomed.

 

[sharinginfos]

anyone can take a look at my post please thanks

 

[Chalo]

I don't think anybody is familiar with the cells you have data for.

If you want LiFePO4 cells that can throw tons of amps but don't need to have lots of range, A123 cells are hard to beat. They're available as used modules that still have plenty of life left, but at low cost.

I don't know what country you live in, but if you can get these shipped to you they're great value:

12V MODULE WITH 8X A123 26650 LIFEPO4

Here are 12v Lifepo4 modules with 8 cells in 4s2p format. Every battery is checked and all cells will have good voltage. These packs are awesome because they line up nicely next to each other. Datasheet is in the 3rd photo. The cells are A123 power cells in 4s2p configuration.

batteryhookup.com

 

[electric_nz]

Lithium Iron Phosphate batteries are lower energy density and therefore heavier for the same capacity as Li-ion. They have high C rate and god cycle life though.

If you had a 2 parallel 16 series pack that would need 32 of these cells, which would weigh 7kg, not too bad but it would be bulky in size.

Good electrical engineering practise is to run components at less than 40% of max, that will give you resiliency and long life. These look to be able to do 3C or 21Amps easily but probably not much higher.

If they are cheap then you could try a 1P pack and see how it goes?

 

[sharinginfos]

I don't think anybody is familiar with the cells you have data for.

If you want LiFePO4 cells that can throw tons of amps but don't need to have lots of range, A123 cells are hard to beat. They're available as used modules that still have plenty of life left, but at low cost.

I don't know what country you live in, but if you can get these shipped to you they're great value:

12V MODULE WITH 8X A123 26650 LIFEPO4

Here are 12v Lifepo4 modules with 8 cells in 4s2p format. Every battery is checked and all cells will have good voltage. These packs are awesome because they line up nicely next to each other. Datasheet is in the 3rd photo. The cells are A123 power cells in 4s2p configuration.

batteryhookup.com

HI Chalo. is it probable that one of the cells of the 8cells would be to replace or they should be ballanced.
i see it is written Datasheet is in the 3rd photo. The cells are A123 power cells in 4s2p configuration. 16s 2p would be nice l light and about 4amp hours. I do not have a spot welder . do you think i could buy 4 of them and and a bms 16s on this without having to spot weld?
i the event that there is a dead cell you you think that i could replace it by buying an additional 4s 2p and keep the tabs on and solder the tabs togehter ?

 

[Chalo]

HI Chalo. is it probable that one of the cells of the 8cells would be to replace or they should be ballanced.
i see it is written Datasheet is in the 3rd photo. The cells are A123 power cells in 4s2p configuration. 16s 2p would be nice l light and about 4amp hours. I do not have a spot welder . do you think i could buy 4 of them and and a bms 16s on this without having to spot weld?
i the event that there is a dead cell you you think that i could replace it by buying an additional 4s 2p and keep the tabs on and solder the tabs togehter ?

Because the cells are 2P, if you have one dead cell, you'll have two. For only $12/module, I'd order an extra module and use the 4 best ones in your pack. Nothing in the listing suggests how much current the cell connections can tolerate, but the fact that they appear to be copper is a very good sign. Anyway, engineered modules like this, often from data center or medical device applications, usually have very good quality control and uniformity. It's not all that likely you'll get dud cells.

If 4-1/2 amp-hours is enough capacity for you, then I think putting 4 such modules in series might do what you want. If you attach to the 2P interconnections between the cells, rather than on top of them, you'll minimize heat related damage to the cells. A BMS has no way to distinguish between one 16S pack and four 4S packs placed in series, so that's not an issue.

 

[whatever]

if your in the usa try this guy, he has good priced cells and lots of different packages you can make up yourself, he's been doing this stuff for a very long time, he will know which cells will suit your purposes.
jehu garcia battery guy

 

[sharinginfos]

if your in the usa try this guy, he has good priced cells and lots of different packages you can make up yourself, he's been doing this stuff for a very long time, he will know which cells will suit your purposes.
jehu garcia battery guy

why do you say if you are the us? im in canada. is it allowed to ship battery or cells usa to canada?

 

[sharinginfos]

Because the cells are 2P, if you have one dead cell, you'll have two. For only $12/module, I'd order an extra module and use the 4 best ones in your pack. Nothing in the listing suggests how much current the cell connections can tolerate, but the fact that they appear to be copper is a very good sign. Anyway, engineered modules like this, often from data center or medical device applications, usually have very good quality control and uniformity. It's not all that likely you'll get dud cells.

If 4-1/2 amp-hours is enough capacity for you, then I think putting 4 such modules in series might do what you want. If you attach to the 2P interconnections between the cells, rather than on top of them, you'll minimize heat related damage to the cells. A BMS has no way to distinguish between one 16S pack and four 4S packs placed in series, so that's not an issue.

Ok when i receive the 5 modules. i imagine i have test to do to see wich one are best. how to select the good ones. ?
i can solder 2 wire in between the 2p modules and im confident i can install a bms.
I still have to balance them right? what machines do i need to do that?

 

[Chalo]

Ok when i receive the 5 modules. i imagine i have test to do to see wich one are best. how to select the good ones. ?

I'd probe all the cell group voltages, and pick the modules that have the least variation between cell groups.

 

[sharinginfos]

I'd probe all the cell group voltages, and pick the modules that have the least variation between cell groups.

i imagine i would still have to balance them?
we dont know how much life is left in those modules right? they could be half capacity capable only correct?

 

[Chalo]

i imagine i would still have to balance them?
we dont know how much life is left in those modules right? they could be half capacity capable only correct?

A decent BMS or balance board would correct any minor imbalances as you charge and discharge the pack.

There is usually some sample testing done by surplus sellers, with results reported in the listing, for instance "every battery is checked and all cells will have good voltage" in the listing I linked. Often they'll say things like "cells test above 90%" or "cells test 80-90%" or whatever. A123 cells have exceptionally long life and consistent quality, which is why I recommended them to you. For 12 clams you can't expect much, but I think they would be well worth the gamble even if they no longer meet their full spec. Only 50% of capacity would mean they're totally wrecked or aged out, which I don't think is what we're looking at here.

 

[sharinginfos]

A decent BMS or balance board would correct any minor imbalances as you charge and discharge the pack.

There is usually some sample testing done by surplus sellers, with results reported in the listing, for instance "every battery is checked and all cells will have good voltage" in the listing I linked. Often they'll say things like "cells test above 90%" or "cells test 80-90%" or whatever. A123 cells have exceptionally long life and consistent quality, which is why I recommended them to you. For 12 clams you can't expect much, but I think they would be well worth the gamble even if they no longer meet their full spec. Only 50% of capacity would mean they're totally wrecked or aged out, which I don't think is what we're looking at here.

On their site i dont see any of those mentions .. .what does that mean?

Are you suggesting that i solder the 4(better) modules together in series or parallel and let them balance with time only? or with bms on ? not sure what you mean. how
I read somewhere on this forum that before connecting cells in parallel , they have to be of similar voltage within small limits or else they damage them self( to much sudden current. )

 

[Chalo]

On their site i dont see any of those mentions .. .what does that mean?

I quoted one from the listing I linked.

Are you suggesting that i solder the 4(better) modules together in series or parallel and let them balance with time only? or with bms on ? not sure what you mean.

If you don't know how a BMS works or what a balance board does, it's not yet time for you to build a pack. Study up first.

 

[sharinginfos]

I quoted one from the listing I linked.



If you don't know how a BMS works or what a balance board does, it's not yet time for you to build a pack. Study up first.

waht quote do you speak of. Maybe you are right and need to learn more. would you have usefull link to learn about balance board and bms in the way you say it?

 

[sharinginfos]

I'd probe all the cell group voltages, and pick the modules that have the least variation between cell groups.

HI
i think i could maybe go forward if someone tells me if my plan is ok.
if i buy the modules from BHookup, and buy this lifepo4 charger

Sorry! Something went wrong!

1 I buy 5 modules, keep the 4 with the least variation between cell group
2 I connect one already paralleled duo(2cells) to the charger above to bring them to 3.65v ( would the charger stop there?) i would use aligator clip i guess
3 repeat step 2 for all 4 duos of the 4 module
4 let them rest for a day
5 connect the modules in serie with wire and a bit of solder.
6 install a bms on them
7 wrap the battery and start using them.

is this procedure ok?


let me know quickly if you can since i might have found what i need but stock is limited.

thanks

 

[sharinginfos]

hum, any one could answer this post?
i would add that if you know a machine that can do what the machine linked does but to do it and stop at 3.45v. It would be greatly appreciated since it is better from what i know in the long run
thanks