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I came to get into my car today ( haven't used it in around 6 weeks, but it was left on charge with the the factory supplied Optimate TM290, and both green lights on the charger were on showing the battery was connected and good) but the keyfob did nothing, hoping it was a flat keyfob battery I tried my spare.. to no avail.

I tried unlocking the door with the key, but had read that if the battery goes flat when locked with the fob it wont open with the key.... which it didn't.

So I popped off the access panel, and checked the battery terminals which showed 0v. Having the factory lithium battery I presumed the Auto shutdown had kicked in on the controller for whatever reason?!

so I hooked up a normal battery charger briefly to the connections under the access panel. The alarm blipped, and the lights flashed briefly. I was then able to unlock the car with the remote fob.

I then disconnected the normal charger and opened the boot to have a look. The green light on the Lithium battery controller had gone off, I pressed the reset button, and the green light came on. I put my multimeter across the battery and it showed 10.8v.

I jumped into the car and powered on the ignition, everything came on, but obviously not enough power to start the engine.

After attempting one crank I checked the battery again and it showed 10.3v

I stuck my probes into the charger to see what voltage it puts out, but it must be a smart voltage sensing unit, as it showed 0v, but as soon as I connect the charger to the battery the charger kicked into life and the lights came on to show it was charging

so I left it charging for a hour or so, then went back out to check its status, the green light had gone out again on the controller (presumably as the voltage was still too low) checked the voltage and it had increased a little since last check so just left it as is.

The charger never goes to the "Save" or "Charge" state, just jumps straight to "Optimize"  is that right??

Ive left it a few more hours and its now at 11.2v so steadily climbing. Do these batteries just charge slowly? Ive got a LIPO powered RC car with a fancy charger, and can charge those batteries pretty quickly.


I did a bit of googling, and found on here that it states in the manual that if leaving the car parked over 2 weeks you shouldn't lock it with the fob. I appreciate that the security system draws some power, but does it really draw more than what the charger is putting back into it?


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Upgrade today to remove Google ads and support TLF.

When I bought the car from a dealer I did ask if there was a tracker fitted by the previous owner,  but they didn't know. Is there a standard place they are fitted,  or are they hidden away in different places so a thief can't find them?

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True, a tracker draws power. If you use a tracker, set it to deep sleep.

If you think there is a tracker but you can't find it you could try to disconnect the car battery for a week or so than the internal battery of the tracker should have died also and the tracker shuts down all together. Perhaps the tracker wont restart anymore after that cycle. 

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I've come to the car this morning,  and the green light on the battery isolator had gone off,  meaning the battery voltage voltage hasn't gone up from charging... its still in the 10.xx v range

The charger is hooker directly to the battery, whereas any power drain will go through the battery isolator. When the isolator switches off that would mean nothing else is able to drain power as the circuit had been cut,  but the charger is still connected directly to the battery, so it should charge without hindrance. 

This leads me to wondering if it's the charger that's faulty, as I did notice before that its skipping the charge mode and just going straight to optimize. The user manual says that at 10.xx v range it should be in the charge state mode. 

Either way for the time being until I get to the bottom of the issue I'm going to get an AGM battery. A Varley RedTop 30. It's exactly the same size as the lithium, and will fit in there nicely.  I weighted the full lithium setup which showed a 5.2kg. The redtop 30 is 10.6kg, but it will give me a bit extra  piece of mind

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Ive had the battery out, and on my workbench charging on, and off. The battery charger will push out a bit of voltage for around 1/2hour before it goes into the idle / monitor mode. its now up to 12.2V but I haven't tried it yet

I've got its first MOT end of this month, so I'm taking the battery and charger back to Lotus to see if they can see where the problem is Battery, or Charger.

In the meanwhile I've got the car back up and running with my new AGM battery solution. It bolts into the aluminium base as used with the Lithuim batteries mount




Its an Odyssey Extreme 30 PC950. I bought a battery tray for it from Rally Design, and then chopped off one of the mounting lugs, and fabricated/welded on a new one that tied in with the existing mount holes

Ive had it on the scales vs the lithium setup from Lotus (Super B 12V25AH)

AGM setup:  10.2kg  vs Litium setup:  5.2kg

Litium setup from Lotus:








Edited by Davey D
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