Small LiFePO4 batteries

[jerrysimon]

I would not want to use those cells in a 1p configuration even my Konion cells are in a 2p configuration.

Jerry

 

[cwah]

At 2p configuration with BMS you'd have a 36v5.5AH for 1.1kg. So slightly heavy than your lightest 3AH konion cell at 1kg without BMS?

 

[Arbol]

The instructions are to re-cell Makita drill packs. For ebike use its simply a case of connecting balance leads, balancing them once then connecting them in series for a 36v pack made out of the two 18V 5s2p packs. You DONT need a BMS. You can also use four packs and connect two of the packs in parellel for a 5s4p to make a 18v 6Ah pack then two of these in series for a 36V, 6ah pack. If you follow the endlessphere link is shows you how people harvest them used from dud drill packs and make up their own ebike packs. Buying them from this ebay supplier means you get new cells and they are already made up for you.

As I said I have used these to make two 3Ah (1Kg) and one 6Ah (2kg)pack and in my opinion for lighter power applications like mine, they are even better than A123 cells.

Its a shame that seller won't post to the UK now as at that price you could have a 36V, 6Ah pack for £90!

Funnily, the seller apparently will post to Spain.

Sorry for my absolute ignorance, but in practice, I do not know what you mean by:

"For ebike use its simply a case of connecting balance leads, balancing them once then connecting them in series for a 36v pack made out of the two 18V 5s2p packs. You DONT need a BMS. You can also use four packs and connect two of the packs in parellel for a 5s4p to make a 18v 6Ah pack then two of these in series for a 36V, 6ah pack".

I have been reading the ES thread, and at least to me, it is confusing. I understand that people with a working knowledge on the subject probably everything is quite clear to them, but not to me.

For example, from the vendor page I see:

Where should I connect the balance leads, assuming I want a 10s4p structure (36V 6Ah, so four of the packages showed in the picture above, two in parallel and then two resulting packages in series)? In fact, which balance leads would you recommend?

Without a BMS, the only "obvious" points I see are the ones marked with + and - in the picture above.

How should I connect them in parallel?

How should I connect them to the controller?

How should I connect them to the charger, to balance them?

Sorry for the basic questions. In fact, probably some of the questions above do not make sense. But I am just trying to find a practical, step-by-step process in order to understand.

 

[jerrysimon]

Follow the endlesssphere link I posted which shows you how to do most of that. As you say if you are in Spain then you can purchase and get them shipped there

It is clear from your questions though that you need to read up a lot more to understand what you are doing.

I don't really want to answer all those question again when it has been documented elsewhere. Endlesssphere has a lot of info just do a search on "Konion" and my battery build link here may also help you. My post is about using A123 cells but the principles are the same.


Jerry

 

[Deleted member 4366]

With BMS


without BMS. You need one more lead to join the two packs in series - see the lipo one



lipos

 

[Arbol]

Wow, amazing, thank you d8veh.

 

[Scimitar]

Note that reliable seller also now seems to be listing Konion (cell nickname for SONY-US18650V and VT) cells again ready made up in 5s2p packs.

Sony US18650VT for Makita BL1830 LXT Lithium ion 18V 18 Volt Repair Battery Pack | eBay

I purchased 8 of those to make up my current 36v, 3Ah and 6Ah packs. Lots of info on these cells over on endlessphere here. These cells perform really well are relatively safe, reliable and hold their balance (without a BMS) even better than A123 cells.

Again though I don't think those prices include shipping to the UK (if you select them they wont let you buy them from a UK ebay account) for free and you will have to pay extra for a different shipping method.

Jerry

Strangely, they'll ship to Ireland, yet not the UK. Weird.
Shipping to Ireland is under $8, each additional item is under $5.
I've asked if they can configure that Makita pack as 10s1p which would suit me.

 

[jerrysimon]

Strangely, they'll ship to Ireland, yet not the UK. Weird.
Shipping to Ireland is under $8, each additional item is under $5.
I've asked if they can configure that Makita pack as 10s1p which would suit me.

Dave,

A 1.5Ah pack ?

I would of thought a 2p would be the minimum for ebike applications and even then only for low powered hubs like the Tongxin/Keyde. 1p would be pushing their max current draw.


Regards

Jerry

 

[Deleted member 4366]

Dave,

A 1.5Ah pack ?

I would of thought a 2p would be the minimum for ebike applications and even then only for low powered hubs like the Tongxin/Keyde. 1p would be pushing their max current draw.


Regards

Jerry

Are you talking about my diagram above. If so, the cells are the blue rectangles, so it shows 40 cells, which is typical for 18650 sized ones in a 10aH battery. It's only a diagram to explain wiring. You could put any quantity in each cell string rather than the four shown.

 

[jerrysimon]

No the other Dave (Scimitar)

Jerry

 

[cwah]

Additional safety information from NASA test on the NCR18650 cells:

https://batteryworkshop.msfc.nasa.gov/presentations/Perf_Safe_Test_Panasonic_Li-Ion_NCR_18650_Cells_JRead.pdf

I think I'm going to order the NCR18650PF and see how it goes

 

[jerrysimon]

Look forward to seeing your results cwah

BTW what is an internal short circuit and how does it occur ?

Jerry

 

[cwah]

I think it happens when you puncture the cell

 

[jerrysimon]

Ah thanks cwah. You can do that to A123 cells and they won't ignite!!

Would be interesting to try it with a Konion cell. I do have a couple of older ones I could test

I guess its unlikely you would damage cells like that on an ebike except maybe in a really bad crash. More likely you could short circuit a cell externally and a lot of the safer cells seem to deal/cope with that.

Regards

Jerry

 

[Deleted member 4366]

It's not very clear from that test report, but I read it as the cells go short-circuit when over-discharged. Then when you try and charge them, they overheat and explode.

 

[jerrysimon]

For me when using cells, without a BMS, I really want to use the safest/most robust ones I can. This is why up to now I have stuck to A123 and Konion (Sony 18650VT) cells.

I guess again that's the advantage of using a BMS in terms of then having access to more cell types.

All that said, BMS units have also been known to fail, but offer the best option for those who want plug and play with no hassle of balancing/monitoring cells etc.

Jerry

 

[trex]

I stabbed a Li-ion cell (80% charge, 4.0V) with a kitchen knife this afternoon to see what happened.
I had a bucket full of water just in case. A fair amount o smelly vapour escaped from the pouch, a lot of heat but no fire. When the pouch became too hot to handle, I put it in the bucket. Vapour continues to escape for about half an hour, the pouch stays quite warm.
I then cut open the pouch to see inside.

Here is the photo I took earlier:

 

[Deleted member 4366]

What type of cell was it?

 

[trex]

no name 5500 5AH pouch. I killed the BMS, kept the cells.

 

[Scimitar]

Dave,

A 1.5Ah pack ?

Yep, unfortunately that's all they are. The seller is willing to make them up as required, so I'll ask him/her if they have the 2.6Ah Konions to match the Bosch ones. Actually, when I read that Konions had been discontinued, it's quite possible only the larger sizes were. If so, I'm left wondering if any other cell has the Konion chemistry and can be treated the same way.

They're 10s1p in the Bosch packs, and I have 6 of those in parallel. It's basically just to keep it simple for the Bosch charger - no bms, no hassle, no fires, no explosion, no running around in the middle of the night shouting, no standing in the middle of the road watching my house burn down.