13s7p battery pack build

[Vbruun]

Hi

This is my first battery build.

I Will share the progress here on endless sphere. The battery Will be used on a moderatly powered bike, drawing 250w average, 900 w max.

IT Will be made from samsung 29e cells and use an LTT smart BMS.

https://imgur.com/a/pzPnp8c

This is the cells put in their holder. Will weld Them when The spotwelder arrives

 

[ESR_RSE]

What specific model and level of amp BMS are you going to run? I would like to see your details on setting that up w BT.

I was scoping out this one:
https://www.lithiumbatterypcb.com/product/7s-8s-or-10s-lithium-ion-lifepo4-battery-smart-bluetooth-bms-with-80a-to-120a-constant-discharge-current/

 

[Vbruun]

This one

https://www.lithiumbatterypcb.com/product/13s-48v-li-ion-battery-pcb-board-54-6v-lithium-bms-with-60a-discharge-current-for-electric-motorcycle-and-e-scooter-protection-2-2-3-2-2-2-2-2/

And the 30a model. I bought it slightly overrated since the controller can draw 18a max.

 

[Vbruun]

The spotwelder arrived yesterday. Will weld the cells tonight. I am excited!

 

[thundercamel]

You will have fun Feel free to browse the link in my signature for a couple similar homemade packs, if you were interested.

 

[ESR_RSE]

Are you going BT only or going to also have the PC hookup?

 

[Vbruun]

BT only!

I tried the spotwelder tonight! IT didnt Work IT wouldn't fire every the pedal was presses, firing at random intervals og er just kept spamming the pedal. Er cheked the pedal itself and IT worked fine.

It is the jst IIs. Does anyone know where I can find repair/improvement guides?



Pretty bummed out right now

 

[thundercamel]

Just to warn you, some of the BMS settings like temperature limits are only adjustable with the PC interface.

As for those spot welders that just look like a box with two prongs sticking out the front, I couldn't trust them. Even if one did work properly, you can't reach too far over the side of your battery pack. Went with the link below instead, based on other users recommendations.

https://malectrics.eu/product/diy-arduino-battery-spot-welder-kit-v3-2-2-full_bundle_car_battery/

 

[Vbruun]

I hope I will have access to the ones I need via the app.

Are you happy with the spotwelder?

For my form factor, the welder I bought is fine, but the fact that it doesn't work is a big setback.

Right now, we are working on a very simple welder, using a starter relay, a 12v battery and a button.

 

[thundercamel]

Yes, I am happy with the malectrics welder, and have used it to build four packs so far with a roll of 0.15x8mm pure nickel strip.

 

[Vbruun]

Since last time, we contacted the manufacturer of the JST welder, who sent us an english manual to help with adjusting the welder correctly.
It turns of that we had adjusted the welder wildly incorrect, but changing to the right settings didn't help at all, so we decided to make a spotwelder ourselves.
It is based off of a lead-acid battery and a relay meant for tractor starter motors.

It looks a bit messy, but works surprisingly well. Right now, the energy is controlled by how long we hold a switch, but we have already ordered a timing board from ebay.

The biggest issue is that the probe gets pretty hot. too hot to hold after about 10 welds, so then I have to slow down.

The battery is halfway welded in parallel and tomorow we will do the series connections.

 

[Vbruun]

Today I did the rest of the welding. Had a panic moment, when I dropped a piece of Nickel strip on the battery, causing it to Short.
Luckily, the nickel instantly burnt Up in the corner that was touching, so I Hope I didn't damage the cells too bad.

I connected the BMS today and it seemed to work very well. Pretty stoked!

Will finish the rest of the build one og the following Days

 

[thundercamel]

Good work Hopefully there were plenty of strips for the series connections to divide your amperage between, like one for each cell (7).

 

[Vbruun]

Exactly!

Here is a vid og the battery, I forgot to take a picture

https://youtu.be/zrRV84FAXsQ

 

[Vbruun]

Did some more Work in the battery today. IT is now completely connected including charge and discharge connections.
I tried charging IT and All seems to Work fine. Next available oppurtunity, I Will wrap the battery and BMS.
I'm getting pretty stoked!

 

[Vbruun]

Does anyone know if there are problems with extending the balance wires on the LTT BMS?

I would like to do that, but I don't know if it is an issue?

 

[thundercamel]

It'll be fine; they're just wires.

 

[Vbruun]

IT has been done! The battery is finished.

Everything Works fine, which gas surprised med a little It gas been mounted on the bike and makes it ubelieveably much better.
Next item is my friends bigger battery for his speed pedelec. Looking forward to that one!

 

[Vbruun]

Also, I just control the maximum charging voltage via the app to the BMS and it works absolutely flawlessly