My first DIY battery

[Wishes]

I've been using Li batteries for many years with my RC hobby and more recently with my e-bike. I am quite familiar with the technology. What I have never done is build my own battery pack with BMS. I have decided to take on this new project to help a neighbor. The elderly neighbor takes his mobility scooter up to his cottage, where it is all hills. So he is always climbing. It comes stock with 2 x 45 AH SLA's. But pulling a constant, or close to constant, 15 AMPs from SLA batteries, he is running them down in no time. The objective was to replace his sla's with lion or lipo. The application is a 2 x 25.9v, 32AH, 7 cell packs for a mobility scooter. They run on 24 volts, pulls 15 amps max. Hoping to give him 64AH of battery by connecting them in parallel.

I have sourced both a BMS and the cells for the application. I have a few good contacts with agents in china, and I managed to find these cells are a very reasonable price. Coming from the RC world, and even on my ebike where i use 6 cells 5AH turnigy packs in series and in parallel. I have never used such large single cells.

Anyone have any experience with these large prismatic cells?

Here are the specs of the cell I found.

Li-ion 3.7V 32Ah Prismatic cell
1 Model NO. SLPB60255255HR2
2 Original Japan
3 Material Li-ion
4 Nominal capacity 32Ah
5 Nominal Volt 3.7V
6 N.W 800g
7 Dimension for the cell body: 255x255x6mm
8 Dimension for the tabs 30x80mm
9 Dimension for the cell with tabs 285x255x6mm
10 Recommend Charge Rate 0.2-0.5C
11 Max. Charge Rate 1C
12 Recommend Continuous Discharge Rate 10C
13 Pulse Discharge Rate 20C
14 Working Charge Temp. 0~50°C
15 Working Discharge Temp. –20°C~50°C
16 Storage Temp. –20°C~50°C
17 Internal Resistance
≤1.5mΩ （ Tested with the 1000Hz
Battery Internal Resistance Tester）

Wishes

 

[Wishes]

 

[elfi]

did U made battery pack?
How good perform cells?

 

[Wishes]

did U made battery pack?
How good perform cells?

Yup I did make it. The cells worked out great. Mind you they are being used on a mobility vehicle that draws 15 amps max. So they are not being pushed anywhere close to their limits. But they are holding up well so far. The user is very happy with them and has had no issues to date.

Wishes

 

[dnmun]

but HOW did you make it? how did you make the connection between the bare aluminum tab and the copper tab? what BMS did you use and do you have pictures of the battery you built?

 

[Wishes]

but HOW did you make it? how did you make the connection between the bare aluminum tab and the copper tab? what BMS did you use and do you have pictures of the battery you built?

No i don't have a picture of it all done sorry.

I used a 6s BMS that I have in stock. They are rated for 20 amps discharge and 5 amps charge. I imported a batch of 30 of those BMS boards for myself and some friends. I still have a dozen left I think. They worked great, have not had 1 of them fail yet.

I couldn't solder the tabs. So I ended up sandwiching the tabs together with 2 pieces of metal bolted together.

Here is a picture of a 20AH lifepo battery I made, those came with a nice solder less assembly plates you see at the top of the battery. I had some extra metal plates you see at the top of the battery, so i used 2 of those bolted together to sandwich the tabs of the larger 32ah cells together to create my series connection.

 

[Wishes]

I've got 12 more of these cells coming in. They are going to be used to make a 24 volt, 120AH portable power pack used to recharge lipo RC batteries in the field. I'll be using the same method to connect and the same bms as my previous one. I'll post some pictures of it when it is done.

Wishes

 

[Martini]

Hello Wishes ,

Gianni from Italy , I am working around my battery powered glider please take a look :

http://www.youtube.com/watch?v=ga4wdh-cqhc

I am planning to replace my LiFePo4 19s3p A123 pouch cells with Li-ion 16s2p SLPB60255255HR2

what is your experience on this cells

Thanks

 

[Wishes]

Hello Wishes ,

Gianni from Italy , I am working around my battery powered glider please take a look :

http://www.youtube.com/watch?v=ga4wdh-cqhc

I am planning to replace my LiFePo4 19s3p A123 pouch cells with Li-ion 16s2p SLPB60255255HR2

what is your experience on this cells

Thanks

That is one nice setup. Congratulations on your build

As for the cells. They handle the 1C charge rate very well. And with their capacity, that is a blessing. They are excellent cells, capable of good amounts of dischage current. But you have always have to be conservative on the C rating they claim on the discharge rates. How many AMPs is your setup running?

Wishes

 

[Wishes]

Hello Wishes ,

Gianni from Italy , I am working around my battery powered glider please take a look :

http://www.youtube.com/watch?v=ga4wdh-cqhc

I am planning to replace my LiFePo4 19s3p A123 pouch cells with Li-ion 16s2p SLPB60255255HR2

what is your experience on this cells

Thanks

A few points about the differences you will encounter between the 2 types of cells.

Those lifepo4 cells I see in the video look like the 20AH lifepo4 narrow pouches that I have also used before. In my experience, a small difference between the 2 types of cells, is you are going to get a little more usable AH capacity out of the lifepo4 vs the Li-ion cell before you start obtaining voltage sag. Again that is very dependent on your current draw. The higher the current draw, the the earlier you will encounter voltage sag from the cell in both cases. And at what i call extreme current draw, close to their max c rate, the li-ion cells will outperform in capacity and be able to the deliver the current demand without a voltage sag

In a high current application, high current being defined as relative to the batteries recommended discharge C rating, I would obtain a good 17AH of usable capacity out of the 20ah lifepo4 cells. Versus the Li-ion cells, in a comparable high current application for its discharge C rating, would provide me with only 25AH of usable capacity from the 32ah cells before it would experience voltage sag.

However, if your application takes the batteries close to their max discharge rate. Then you will obtain better overall performance from the Li-ion cells.

Another big difference, is their voltage drop as capacity gets used. The lifepo4 cells, will provide you with an almost constant 3.3 volts for 80% of their capacity usage. Therefore you obtain a very constant voltage for 80% of the duration of your battery pack.

In the opposite, the li-ion cells will start at 4.2 fully charge, and will steadily drop voltage level as the capacity gets used up. Your max voltage from your battery pack will steadily drop as its capacity gets used up.

That means the max rpm of your propeller will steadily decrease as the pack gets used up. Not so important on a ebike or an RC plane\car, but in your application, max rpm = max thrust. Therefore you will have a steady decrease in max thrust as the L-ion battery pack gets used up. Compared to the Lifepo4, which you will obtain a steady max rpm and max thrust for 80% of its capacity. Something to take into consideration if you go the Li-ion route.

Hope that helps.

Wishes

 

[Martini]

Hello Wishes

thanks for your help and support.

Now I am running static tests with 19s3p A123 60Ah pouch cell , this are nice cell , unfortunately too heavvy for my application .

I use a 48pole BLDC motor with Hall sensor , 63Volt - 280A Continue for a 75 / 78 Kg of static thrust .

As do you know this power is needed only for the take off and I estimate to run for 2 to 3 minute max. after this power can be
reduced to 70% , after 5 to 10 minutes power is switch OFF and start gliding

So basically my idea is replace the 19s3p with 16s1p with 60 Ah or 75Ah Dow Kokam cells , unfortunately no replay from the
new company

http://www.xaltenergy.com/cell-products-technology/cells/xalt-energy-cells/


do you Know this ?

Talking form supplier in China She offer me these cells for a low price ( 32USD$ each ) but for my safe I prefer use professional
cells not " toys " cell because cells are back on my seat ......

Do you have any suggestion for cells selection or where I can found it ?

Saluti

GIanni

 

[Martini]

Hello,

surfing on the WEB i found the new full electric BMW i3 is powered by Lithium-Ion Battery ( 8 pack of 12 cells ) = 360 Votl / 22Kw

http://www.greencarcongress.com/2013/07/bmwi3-20130710.html

http://www.klib-org.de/fileadmin/user_upload/Aktuelles/Services/Lamp_BMWi.pdf

Saluti a tutti

 

[Wishes]

Hello Wishes

thanks for your help and support.

Now I am running static tests with 19s3p A123 60Ah pouch cell , this are nice cell , unfortunately too heavvy for my application .

I use a 48pole BLDC motor with Hall sensor , 63Volt - 280A Continue for a 75 / 78 Kg of static thrust .

As do you know this power is needed only for the take off and I estimate to run for 2 to 3 minute max. after this power can be
reduced to 70% , after 5 to 10 minutes power is switch OFF and start gliding

So basically my idea is replace the 19s3p with 16s1p with 60 Ah or 75Ah Dow Kokam cells , unfortunately no replay from the
new company

http://www.xaltenergy.com/cell-products-technology/cells/xalt-energy-cells/


do you Know this ?

Talking form supplier in China She offer me these cells for a low price ( 32USD$ each ) but for my safe I prefer use professional
cells not " toys " cell because cells are back on my seat ......

Do you have any suggestion for cells selection or where I can found it ?

Saluti

GIanni

The Kokam cells are quite reliable and have a good reputation for quality. I've bought about 50 of these in the last 6 months for various applications and so far no issues. However, the cells are not running in an application with anything close to your voltage and current requirements.

I don't know the reseller you put in your url above. I buy those cells from OSN Power Corporation in China. http://www.osnpower.com/. I can PM you the email address of the rep i deal with over there if you are interested. The cost was 32$ USD for those cells.

 

[Martini]

Hello ,

Thanks I'm also in contact with ms. Lin from this company , i wil built 16s2p , 32 + 32A and run it at 5C

Do you think is ok for my project. ?

 

[Wishes]

Hello ,

Thanks I'm also in contact with ms. Lin from this company , i wil built 16s2p , 32 + 32A and run it at 5C

Do you think is ok for my project. ?

In any application that you are using Li-ion, lifepo4, or any other of the new Li battereis, you have to take your precautions.

Like I mentioned in my previous thread, i have gone through about 50 of these without any issues. But none of my applications had the safety of the passenger dependent on the batteries, like in your application.

As a general rule of thumb, li-ion cells are more fussy than Lifepo4. They are more fragile and can tolerate much less abuse versus the Lifepo4.

If you take your precautions with the cells. I think they will do fine. You will get much more energy density for the weight with these Li-ion cells versus the old Lifepo4.

I run the following test on all my cells that I buy. I run this test on the individual cells. It is a longer process, but one that re-assures me on the safety before I sell a battery pack to someone.

I charge and discharge the individual cells 3 times each. Measuring total AH input during charge and total AH used during discharge to make sure they are consistent. I have rarely seen cells deliver their true rated capacity. They usually have about 90-95% of the rated capacity. And it varies slightly from one cell to another.

I measure the internal resistance of all the cells and make sure I do not have a difference of more than .5 ohm resistance between cells within the same pack. ( Note, i have never got a kokam cell that had a higher internal resistance than 1.1 ohm, most are under 1 ohm, very good internal resistance).

I repeat my 3 charge and discharge tests, but this time i use a few cells in series and I use balanced charging and discharging at high current rates. While monitoring the individual battery voltage levels. That usually helps identify when you have one cell that just doesn't like to charge or discharge as fast as the others.

Wishes

 

[Martini]

Hi ,

Yes safe is the most important point .

Can you help me to Know the price of the XALTEnergy 60Ah MODEL F900-0002/F900-1002 in Europe is not possible found price info

http://www.xaltenergy.com/data-sheets/XALT_SpecSheet_60Ah_HP.pdf

i Will buy 16 pieces

Thank

 

[Martini]

Hello Wishes ,

If I understand KOKAM is not a simple way to follow........

So before order 32 pieces of those cells if I pay , you can you made for me an heavvy discharge tests ?

What I need is 2 of these cell in parallel and run 5C or 6C continue test .

I prefer transfer money to you , because I will loose a lot of time buying 2 cells in China made a tests etc etc .

Can you help me ?

Gianni

 

[Wishes]

Hello Wishes ,

If I understand KOKAM is not a simple way to follow........

So before order 32 pieces of those cells if I pay , you can you made for me an heavvy discharge tests ?

What I need is 2 of these cell in parallel and run 5C or 6C continue test .

I prefer transfer money to you , because I will loose a lot of time buying 2 cells in China made a tests etc etc .

Can you help me ?

Gianni

I have a few spare of these. I can send you 2 of them only if you want.

 

[pbrownhg]

I would like to buy these cells and use them in a 6.25C draw application and 0.625C charge. Does anyone have test reports using these batteries in this range?

 

[Wishes]

I would like to buy these cells and use them in a 6.25C draw application and 0.625C charge. Does anyone have test reports using these batteries in this range?

Not I sorry, some of these cells got used in an application that does not even take them to 1C. How many cells did you need. I still have a few left over of these.

 

[pbrownhg]

I need 24. How many do you have up for grabs?