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Blog des Suntrippers

Battery story

09.02.2021 - Alex Hofvander
Alex Hofvander Alex Hofvander

I actually tore my newly built battery apart and gave it a completely new form factor. Why?

You know when something is nagging you. Like did I close the window or did I turn off the stove. Well, that happen to me. The absolute first part of the build I used a piece of crap equipment called Sunkko to do the welds. I was not sure it did a good enough weld so I ordered the more expensive kWeld from Germany.
But I let the welds be and continued the build with the kWeld which did a fantastic job. Then I stated thinking ahead. What if one of the welds break? I don’t want to destroy a pretty expensive battery even if it is DIY. The roads are pretty rough at times…

So I started to rip everything apart. It was a hassle to do and it took me a good chunk of time. As I suspected. The welds made by the Sunkko spot welder was absolute crap. I could rip the nickel strips off by hand. But not the ones made by the kWeld. Had to use pliers. They were on there hard.

I cleaned everything up with a dremel on all cells and added another set of 9 cells in parallel and then added that so it becomes 13 in series instead of 12 like from the original build.
So now I have a 48V pack instead of 44v but I lowered the state of charge even more from 85% SOC to 80% SOC to achieve the legal top limit of 1155wh for the Suntrip. See pictures.
This way I am saving my battery even more and making it even safer. The further away from 100% charge it is. The better it is and safer it is for the battery and my health. Li-ion cells can catch fire. Especially if battery is abused like it will be in a solar charged vehicle like my trike. Constantly being charged at the same time it is being used. Sometimes at very high discharge currents and/or sometimes at high charge currents. High charge currents can be achieved going down a long decent and I use regenative braking and when the sun is baking the panels at the same time. I have seen charging up to 21A going down hill. This battery can handle that safely.

This new form factor also allows for better cooling of the battery since the cells aren’t packed so closely together anymore. And it gives me a much easier time when it comes to fitting it to the trike. Before I only had one option on where to mount it. On the rear pannier rack. Didn’t like that. Too high centre of gravity. I wanted it lower to the ground. Creates greater stability. I have two options now. Mount it on the left side under the seat or on the boom. Haven’t decided yet which way to go but it is nice to have options.
Now I am just waiting for the new 13s battery management system to arrive and then I can build it the way I want. Same kind as before but for this new configuration. This time with really good equipment all the way. No fear for failure.

I do not think most people think about these things but it is important. It is your health it concerns and your wallet. The way I do thing saves both. Except the initial cost and the added weight. Other than that, I wouldn’t ride any other way.


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