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DIY Battery for Patio Roof Motor


Iiceman
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Hi Guys

I am in need for some advice please...

So my patio roof has a motor to open and close the roof.

In the control box there are 3 x 12v2.4ah lead acid batteries connected to the main board with 3 pairs of positive and negative cables. So im assuming this motor is 36v. Just to be clear, these batteries are not connected in series, but rather directly to the main board.

Here is where i need the advice..i have quite a few reclaimed 18650 cells in good working order..i was thinking of setting them up as 3 x 3S1P

Would i be able to use them in place of lead acid's? and would i require 1 BMS for each of the 3 packs?

 

regards

Iiceman

 

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  • 2 weeks later...

Hey Iceman

There are a number of options to replace those ridiculously priced 2.5AH 12V batteries.

  1.  Cheapest and easiest is to simply replace them with 3x 7AH Sealer Lead Acid batteries. This will provide you with plenty of capacity and the batteries are cheap as chips (get decent brand ones eg CSB or Forbatt). The existing charger may be a  little under rated but the effect is not too serious as the charge time will take longer if the batteries are really flat. Simple job to put the new batteries in an external case as I am sure they are not likely to fit where the old ones went. Check if you can find the charging circuit IC eg LM317 and if it does not have a heatsink, put one on !
  2. LBSA sell 6 AH 32700 cells and a 36V BMS (12S). The 32700s have built in nuts and bolts which make it easy to assemble with connecting strips. This is a neat and elegant solution. Cells - https://lithiumbatteriessa.co.za/collections/cells/products/3-2v-6ah-lifepo4-lithium-ion-phosphate-battery-call; 20A BMS - https://lithiumbatteriessa.co.za/collections/bms/products/lbsa-bms-20a-12s-36v-lifepo4-lithium-ion-phosphate?variant=34759461503143. Cell connectors  - https://lithiumbatteriessa.co.za/collections/diy/products/battery-connector-set
  3. If you want to go down the 18650 route (I built a 10 AH eBike battery with them) you will need a 10S BMS. Have not found one locally available though. I imported mine from AliExpress. I soldered the connections between the 18650s but the result is not very pretty so I have ordered a spot welder to connect the cells using nickel strip. 

PS make sure your reclaimed 18650s in the pack you are building  are of similar capacity and I would highly recommend you also check that their internal resistance is acceptable. You can get a charger that has a built in internal resistance checker or you can do it the manual method - google it and there a number of good sites describing how to do it. 

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I just did the exact same thing to my 24V garage motor backup just the other day. I replaced the two 12V 2.4AH batteries (similar size to 60mmx80mmx175mm I think) with 8S1P 32700 batteries in a staggered configuration. I bought a cheapie BMS, 20A perhaps, and it seems to work nicely.

image.png.5315be63bfe137c6cdc21c62cdd9e0bd.png

image.png.a4860c0f00b57b0571f0de4ac24c1276.png

My next step is to get a BT BMS so I can monitor the cells remotely via my phone but before that I want to do a few Open|Close operations to see how many operations I can get before declaring this a success and leaving it in as a permanent replacement. My old batteries lasted 4 years (with a balancer) and they are still good. The LiFePo4 upgrade was just because I was bored over December 🙂 

Before installation one of the cells was slightly low but it took a few hours and they are all in perfect balance now.

So, if you like to do small projects like this then go for it, just make sure the charge voltage is enough to balance the cells and not too high to have the BMS cut off the power. Check the datasheet.

 

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