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Comms Failure EMS

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Hi, I know this has been covered before but slightly conflicting advice and most of it quite some time ago so hopefully someone has found a solution. I hadn't been out in the Evora for a while and had accidentally disconnected the trickle charger so battery discharged. Charged it and it started fine, then went for a decent drive (around 20 miles). When I tried to restart later everything worked - clocks, music, lights, locks - but no signs of life from engine and have the comms failure EMS message. I am confused in that if I'd fried something I'd have thought it wouldn't have started in the first place.

Tried disconnecting the battery for a while - no help (in fact now clocks are not lighting up, although music, fan etc still working). Bought a fault reader but it doesn't seem to be getting a response from ECU.  I suspect it's a trip to the dealers on a trailer, but any easy ideas first before I bite the bullet? 

Thanks. Ben

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A trickle charger can prop up a battery nearing end of life but once it's been fully discharged it can struggle to recover.  Often that only shows up as a very slight voltage drop but if you can measure capacity you'll find it's way down - which means accessories may work but the car won't start.  Lots of people (me included) have seen odd behaviour from electrics when the battery is below capacity but not completely dead, then it'll fail completely a few days/weeks later.

If you've got home breakdown cover then folks like AA/RAC can test battery capacity as well as voltage.  A replacement battery is about £80 for the uprated Varta Silver spec with a 5 year warranty.

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Sounds familiar. I have ordered a new battery for mine as I have not used the car in a month (or set up the trickle charger) since we moved house. Seems the full discharge has done for the battery. Recharged it, but it isn't "right".

A Lotus is for driving, pork is for breakfast.

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Using a "Ctek" I have had 8 years out of a Battery, as they cycle the battery after 10  days, it helps keep the plates clear on a Lead acid Battery. As for the AGM ( absorbed Glass Matt) battery I use one in my 7, only had one for 30 months so Ill have to wait and see.

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New battery arrived today,  installed it. All the lights etc. now working fine again (battery was indeed kaput - 11.9V after overnight charging dropping to 9V) but original problem remains. Still getting the Comms Failure EMS message, nothing when I turn the key, phone connecting to the OBD adaptor but adaptor not connecting to the ECU. Tested the obvious fuses (ECU related) and they're fine. I read there is an ECM recovery process which Lotus can try, but presumably they need the car for that.

Assuming it does need to go into Lotus, any views on whether Hoffmans or Bell and Colvill (local dealers) are better for this kind of non-standard troubleshooting type stuff? 

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