we bought a new one in the end (£189), which is a shame as the cells where perfectly ok i'm thinking the BMS went on ours (same as you sat around in winter) it does wake up with a bit of tinkering but in our case only for a few hours then it shuts down again
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I'm still in the middle of finding out why ? but will need to replace and check all the wiring which may take some time and as we have no need for it now i might break it down and reconfigure to 48v if i find any more cells..
so if you can't get yours going again and decide a new one is needed i would like to have yours of you for some beer tokens
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I took ours apart exacly how d8veh explained, you need to carefuly chip away the brittle glue then slide outof the bottom turning the top so it fit's through the ally case,
Once out then cut the tape to the insulation board unfold to expose all the cells and bms, The way i woke my bms up strangly was to disconnect the ballance tabs and then plug the charger in for a few seconds, then disconnect then plug ballance wires in again, Stange but worked for me ??...
check all fuses and wiring continuity for any faults, this is as far as i got but still no joy with ours, Just stays alive for couple hours then goes again, strangly down the 13v
Hope you have more luck then us and have fun!!!...