Swapping old 18650 cells with new ones

[Joe T.]

I have a 48V 10Ah eZee Flat Battery that I bought new in 8/2013. It has served me well but I have lost some range starting this winter. I am curious if I can simply buy new 18650 cells and replace the old ones. I have a spot welder and have practiced on some batteries already. The original cells are Samsung ICR18650-22P. Luna offers Panasonic 18650 GA 3500 mAh. This should be a nice upgrade for me. I plan to use the current BMS and copy the configuration. The question is can I simply swap out the cells? Or is there compatibility issues that I may need to deal with.

 

[Hillhater]

If you have the skills, tools, and the patience, it should be fairly simple.
You may need to replace the link conductors as they will probably get damaged removing the old cells.

 

[Joe T.]

The plan is to basically build a new battery inside the original battery case. I will replace all the cells. Re-use the rest of the parts. I will save the old cells for future projects.

 

[999zip999]

Is it 13s5p in pyramids ?

 

[Joe T.]

Is it 13s5p in pyramids ?

At this time I am using the battery. I have never looked inside. All I know is it is 13S-5P. So I plan to buy 65 new cells and copy what is inside. My only concern is if there is a compatibility issue with one 18650 cell to the other.

 

[999zip999]

Most 18650 at 3.6v normal and charge to 4.2v a few types higher. Just get the one to match ( voltage ). The capacity doesn't matter just more time charging and discharging. It's more important to match pack to controller. What motor and controller setup do you have. ?

 

[Joe T.]

Most 18650 at 3.6v normal and charge to 4.2v a few types higher. Just get the one to match ( voltage ). The capacity doesn't matter just more time charging and discharging. It's more important to match pack to controller. What motor and controller setup do you have. ?

I bought a GNG in 2013 and the controller that came with the kit is the one I'm still using.

Luna also has Samsung INR 18650 25r cells if that sounds like a better match. I have plenty of power and if I can get more range that would be a good thing.

 

[Joe T.]

I bought some Samsung 35-E cells from Tumich. I started with some nickel strip from the internet but I didn't buy enough. To save time I bought some nickel shim stock from MSC and cut my own battery tabs. My friend Doug built a spot welder using a transformer from a microwave. A relay left over from a job that was programmable. I set the timer to .2 sec for arc time. This worked out well. I simply copied the layout of the original battery including the balance wires.

I charged it and the battery took a full charge to 54V.

I took it for a test ride and it seemed to work fine. Sadly it is winter now and I froze my toes off testing it so it may not be until the spring when I get a good test done. I did go up my favorite hill and the new battery didn't sag like it was with the old cells.

 

[Joe T.]

After first building the pack I took it out but only got 8 miles out of it. This was a cold day and though the power felt great, it cut out early. It recovered well and I was able to nurse it along as much as I wanted. It was cold and I was not dressed well. I was concerned that I could have a cell or two that my have had bad connections.

As the weather got warmer my mileage went up. Things finally fell into place for me to get a ride in with out freezing weather. I got 36 miles out of the pack and I still had power left. It did cut out on a steep hill right at the end but I was not surprised after 36 miles.

Samsung INR 18650 35E cells from Tumich.

 

[999zip999]

Good job. The most important thing is the pack balanced ? Are all cell groups the same voltage. I don't drain a pack to cut off it will unbalance the pack.

 

[Joe T.]

I assume it is balanced. It has a BMS, the original one from the pack. When I first assembled the pack it would not charge. I looked inside and the balance wire plug had come loose. After that it has acted just like before. I will say it takes 5 hours to charge. With the 22P cells it was more like 3.5-4 hours.

I run it mildly hard for a good 15 miles and ease up as I approach the 20 mile mark. I expect the battery to cut out any time after 20. I have never had it not come back during a ride. I just tax it less as the power drops.