Compact LiFePO4 Battery Cells (3.2V), Aluminium Casing

[GM Canada]

These look interesting!

Compact LiFePO4 Battery Cells (3.2V), Aluminium Casing





Gary

[_GonZo_]

This cells looks interesting, do you have more info and prices?

[GM Canada]

Nothing yet, it is something I noticed on the GM China site. That is usually how I discover we have new products

Gary

[Andrew]

Quite a sexy product

[T5T]

Nohting yet, It is something I noticed on the GM China site. That is usually how I discover we have new products

Gary

A dealer should always have first-hand information - why accept it as it is now.
It annoys me every time this comes up again, so I have to comment  it.

It is time to demand ..........

[_GonZo_]

  The communication with China suppliers is quite difficult, lets say special...
Usually if you ask them what is the weight of a product the answer is "red" and things like that.  
So it is not surprising what Gary experiences.

[GM Canada]

If only people really knew what it is like to be a dealer for GM . Anyway I have requested information on these new items, Maybe they will respond.

Gary

[krelle52]

Well Gary

I hope you hear something. Because I am very keen on using them for my project.

And yes .. the level of information could be better from goldenmotor. It bugs me too

[GM Canada]

Im just wondering. Looking at the specs on the these cells. How many and which cells would you use to make up a 48v20 amp hour battery? What is the method?

Gary

[MonkeyMagic]

16 of the 10Ah cells wired in series, then another 16 of 10Ah cells wired in series - connecting both packs in parallel for your 20Ah rating (16s2p)

[krelle52]

I can confirm it, it is also how I would do it.

But MonkeyMagic why 16? 15 x 3,2V = 48V. What is it I am not getting  

[_GonZo_]

16 of the 10Ah cells wired in series, then another 16 of 10Ah cells wired in series - connecting both packs in parallel for your 20Ah rating (16s2p)

Sorry Monkey but that is not the correct way to do it.

The correct way is:
First you have to connect the cells in parallel in this case by pairs so you make 16 elements of 2 cells in parallel (20Ah)
Second you connect those elements in series.

The way you propose it is only interesting if you are going to use 10Ah pack separately for another use.

But MonkeyMagic why 16? 15 x 3,2V = 48V. What is it I am not gettin

It is a question of old thinking... people has not still changed mind from Lead acid batteries (2V per cell) and still talk about 12V (6S), 24V (12S), 48V (24S), etc.
Usually as you can see it is used a pair number of cells because it is easier to make packs.

So LiFe (3,2V per cell) equivalent packs will be: 12,8V (4S), 25,6V (8S), 51,2V (16S), etc.
But instead of calling them by those voltages people still uses the Lead acid nomenclature...

[MonkeyMagic]

16 of the 10Ah cells wired in series, then another 16 of 10Ah cells wired in series - connecting both packs in parallel for your 20Ah rating (16s2p)

Sorry Monkey but that is not the correct way to do it.

The correct way is:
First you have to connect the cells in parallel in this case by pairs so you make 16 elements of 2 cells in parallel (20Ah)
Second you connect those elements in series.

The way you propose it is only interesting if you are going to use 10Ah pack separately for another use.

But MonkeyMagic why 16? 15 x 3,2V = 48V. What is it I am not gettin

It is a question of old thinking... people has not still changed mind from Lead acid batteries (2V per cell) and still talk about 12V (6S), 24V (12S), 48V (24S), etc.
Usually as you can see it is used a pair number of cells because it is easier to make packs.

So LiFe (3,2V per cell) equivalent packs will be: 12,8V (4S), 25,6V (8S), 51,2V (16S), etc.
But instead of calling them by those voltages people still uses the Lead acid nomenclature...

Same same Gonzo, both methods would work - my 16s was in consideration of a BMS (16s more readily available)

Either way, you would still have same amp hour and current output no?

[krelle52]

I find it hard to see how Monkey and my way is wrong Sorry..."not correct". The only difference I see is that Monkey and my way is easier. I almost had to draw your setup Gonzo to understand it. A simple question deserves a simple answer  

The reason I asked why Monkey choice 16 cells instead of 15 cells is that Gary asked for 48V, not 51.2V. Had Gary asked 36V (36V / 3.2 V = 11.25 cells) Then we would have had problems and would have had to round up to 12 Cell. However.. 48V is evenly divisible with 3.2 V = 15 Cell. So Monkey may have had a good reason to why he would give Gary the additional expense of two cells.

I do not mind admitting that I know very little about BMS. The BMS systems I know of, is built up with a master / slave relationship. You buy a Master Card (Not to be confused with the credit card with 2, 4, 8 or 16...etc connectors to connect the slave cards to. A slave card per cell and the slave card I have seen, are not cheap! There are probably other types of BMS systems. Again, not an expert on BMS. But the long and short of it is: then I was just curious why Monkey wanted Gary to spend more money without a good reason. Which I was sure that there was!

[_GonZo_]

Same same Gonzo, both methods would work - my 16s was in consideration of a BMS (16s more readily available)

Either way, you would still have same amp hour and current output no?

The end result of both methods is the same battery pack, but there is a difference on reliability between one way or the other.

One of the reasons is because even if you match the cells really well they will never be exact the same so in long terms you will have more discrepancies between the cells if you make both packs work in parallel.
On the other way the discrepancies will be smaller so battery will have longer life.

As well if you make 2 16S packs and then you connect them in parallel you have 24 independent cells and will need 2 BMS one for each 16S pack.
The other way you will have only 16 elements and you will only need 1 BMS

If you do not plan to use a BMS then is even more important to build the pack as I say, if not you will have to charge each pack independently if you do not want to have problems with the charger/balancer.