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Beolit 12 DIY battery replacement Image 1

Beolit 12 DIY battery replacement Image 1
posted by On the fence
Wed, Aug 4 2021


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Hi all, I thought I'd add my experience here if it helps at all.

Small print:- I'm not an electronics engineer, and have no affiliation with the suppliers mentioned.

My Beolit 12 battery died after a few years, so I carefully cut open the pack, and replaced the cells with some nice Panasonic 18650's I got from 'Batteries plus' (in the UK). They cost £30.75 for the 4 inc. shipping & tax.

Plugged in, and nothing. no output from the board. I tried charging the pack directly, in case the undercharge function* was stopping it working, and still got nothing.

*Lithium cells have to be charged individually, and strict current limits exist on charging and discharging, and not being a fully trained electrical engineer I wasn't sure how many of these functions were being performed by the board in the battery pack, and how many by the unit itself.

I did hunt for a wiring diagram online, but had no luck there.

I note that the individual charge voltages are present on the yellow, green and blue wires from the connector, but still not sure about the current protection levels, so decided to add a new BMS (Battery management system) board.

I bought this board from ebay, from a seller with the confidence filling name of CrazyTom:-'4S 30A 14.8V 16V8 Li-ion Lithium battery BMS BALANCE CHARGE'. Cost £4.99. Very quick shipping.

Wiring is very simple; Large red & black charge wires from the Beolit12 connector to the board (charge/discharge tabs), then add similar size cables from the battery +/- to the board. It comes with a harness which includes the small wires to connect to each cell for charging/balancing.  This is all shown in a diagram on the sellers ebay site. The mini connector from the BL12 is now redundant.

Thought is required as to the direction the wires are soldered, as there's not much room for the board.

Make sure all the tabs are insulated properly, I used heat shrink sleaving (got a nice kit of sleaves form Lidl), but ebay will provide, or at least insulating tape will suffice. And when soldering, do your best not to short out the cells (probably the trickiest part!). Tape can be used to hold the cells in their pack formation too.


I didn't officially time it, but the pack worked fine, and lasted a good day at medium volume.

With my new set-up there is no thermal protection, so I monitored the voltages and temperature of the cells during charge and discharge, and noted the cell voltage pulsing, which showed the charge current was being limited, and there was no nasty temperature rise.

So all in all a success, converting a paperweight into a useful object!

I've never had any success with the wifi, and use a Bluetooth dongle instead.

I also managed to find a replacement door catch from Ali express here:-https://www.aliexpress.com/item/32868859217.html?spm=a2g0s.9042311.0.0.7e304c4dbd25EX £2.09 for 20!

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