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Leaving Battery connected


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A question for Esprit owners with cars that have ECU's. Is it best to leave the battery connected with a trickle charger or disconnect the battery when laid up for any length of time?

My main concern is the ECU's life especially considering how rare they are. Battery' are easy to replace.


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Depends on time stored, ease of access etc. I'd leave the battery connected and hook up a charger every once in a while. Or permanently connect a good trickle charger.

If it's for a longer period, you could remove the battery, but I don't really see an advantage to that. With a good battery, you can just disconnect the negative so there's no current draw while parked and reconnect when you want to drive it again, without the need to charge it.


I have made many mistakes in my life. Buying a multiple Lotus is not one of them.


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I've heard horror stories of people frying their V8 ECU:s in particular - I would't risk it. I don't even leave my battery connected on my 4 cylinder car.

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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I always leave the battery connected in the car (1990 Turbo SE). I use a good ctek charger. Only seldomly I disconnect the battery if I need to Work a bit more thorough on the car.

Never had any trouble during my 6 years of ownership. Also, it's the same battery as when I bought it, so now more than 8 years old, working perfectly.

Usually, if battery has been disconnected, I let it warm up as usual, and then drive on. ECU learns what it needs after apprx. 40 kms.

As I have an alarm and imobiliser installed in the car since new (from Swedish Lotus dealer/importer - which was a must at the time), there's a Little current Draw, but it easily last two months, and can still start the car with a fast spinning starter. Those are my experiences.

Kind regards,


Nobody does it better - than Lotus ;)

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I have the battery of my LH 1990 Esprit Turbo SE permanently connected with a trickle charger .

It is connected with a male plug and a female plug (with spring actuated dirt cap) which is mounted in the upper part of the left rear wheel arch (invisible) as well as an internal intermediate fuse; all directly connected to the battery by a separate wire.

I use a cheap Chinese made autom. controlled trickle charger ( GBP 15,-).

This way I always have the right tension on the car

Never had any trouble during my 26 years of ownership.

My maintenance free battery was replaced of course a couple of times during those 26 years; the average lifetime each battery (surprisingly) was generally 5 years and 8 months.

After a (trickle charger connected) lay-off period of for instance a half or one year the Esprit starts within 0,5-1,5 seconds.

I have 2 other cars, a Mazda Rotary RX-8 Renesis HP / 231 hp and a Mazda 2 1,5 GTM, as well as a Honda Goldwing GL1000 motorbike of 1975.........all 3 have their own trickle charger connection on the outside of the vehicle and all 3 are permanently connected and therefore I have never any fuzz with the electr. start tension.


Edited by rudolphwolven
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10 hours ago, pureguava said:

If disconnecting battery regularly does that not mean you are resetting the ECU each time?

My S4S runs badly for about 15 km after a reset until it relearns - are others not having this ?

As said, that's the relearn cycle. Something I rather avoid if possible, so I only disconnect the battery when working on/near electrickery. With the Esprit in daily use, I never need to worry about maintaining the battery anyway. I certainly don't have the patience to wait 'till the fans kick in before I can go for a drive. And I wouldn't be comfortable with letting her idle so long either, especially immediately after start up. The oil pump needs a bit of revs to build up a good flow and pressure and make sure everything is properly lubricated. Driving off straight away (after fastering seatbelt, adjusting radio etc, say 10 sec) and gently warming up on the road seems much better, also warms up the gearbox so you can soon start having fun.


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I have made many mistakes in my life. Buying a multiple Lotus is not one of them.


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