Elise battery life: green knob & ECU

[sunmax]

Dear Lotus enthusiasts,

I just joined your wonderful community and I already have some questions,
(I split them according to the forums), here come the ones about the battery.

The original battery kicked the bucket after I did no drive (alas!) my
sweet Elise (a laser blue Fed 06) for a couple of weeks. It's possible
that the weather (hot and humid here in Miami) could be a factor too...,
so I replaced it with a heavy, but long lasting Optima Yellow Top D35.

Building up some basic knowledge reading through your forums I decided
to install a "green knob" too.

Now, considering that I normally can enjoy the Elise only once or twice
a week for ~20 miles, I'm trying to maximize the longevity of the battery.

a) when the Green Knob is unscrewed (i.e. going through the fused path)
is the battery drainage lower than through the normal path (when the
knob is closed)?

b) I read that there are 3 major factors discharging the battery:
ECU, alarm/immobilizer, radio.

My car is in a secured gated parking, alas outside (but well wrapped
in a Weathershield cover ;-), if I don't insert the alarm using the
Cobra, is the battery going to last much longer?

Anyway, between the gated parking, the locked car cover and the green
knob, I think I can sleep safe even without the alarm... ;-)

c) I know the green-knob is meant as an anti-theft device, but what would
happen to the Elise if I used it to completely cut off power removing
the fuse, before unscrewing the knob (I would of course disarm the
alarm first!) ?

I don't care that much about radio stations, but what about the ECU ?

Is the car going to start ok if, let's say after a couple of weeks,
I come back and screw the knob back in?

Looking forward to your expert suggestions!

Thanks!
-Max

P.S: I'm pretty new around here, and even if I did some homework it's possible
that I missed something in one of the previous threads. If this is the case just
point me to them, and I'd be glad to read them ;-)

[TheViper]

Hi Max,
I don't know if you have read this Battery Choices & Information See my specific responses below. Even with the battery connected the Yellow D35 should last at least a couple of weeks connected.
Michael

Originally Posted by sunmax

Dear Lotus enthusiasts,

I just joined your wonderful community and I already have some questions,
(I split them according to the forums), here come the ones about the battery.

The original battery kicked the bucket after I did no drive (alas!) my
sweet Elise (a laser blue Fed 06) for a couple of weeks. It's possible
that the weather (hot and humid here in Miami) could be a factor too...,
so I replaced it with a heavy, but long lasting Optima Yellow Top D35.
High temperatures do shorten a battery's life due to sulphation

Building up some basic knowledge reading through your forums I decided
to install a "green knob" too.

Now, considering that I normally can enjoy the Elise only once or twice
a week for ~20 miles, I'm trying to maximize the longevity of the battery.

a) when the Green Knob is unscrewed (i.e. going through the fused path)
is the battery drainage lower than through the normal path (when the
knob is closed)? Battery drain is exactly the same, you need to remove the fuse to stop it.

b) I read that there are 3 major factors discharging the battery:
ECU, alarm/immobilizer, radio.

My car is in a secured gated parking, alas outside (but well wrapped
in a Weathershield cover ;-), if I don't insert the alarm using the
Cobra, is the battery going to last much longer? Yes

Anyway, between the gated parking, the locked car cover and the green
knob, I think I can sleep safe even without the alarm... ;-)

c) I know the green-knob is meant as an anti-theft device, but what would
happen to the Elise if I used it to completely cut off power removing
the fuse, before unscrewing the knob (I would of course disarm the
alarm first!) ? No parasitic battery drain

I don't care that much about radio stations, but what about the ECU ?
No power to the ECU is no problem

Is the car going to start ok if, let's say after a couple of weeks,
I come back and screw the knob back in? Yes


Looking forward to your expert suggestions!

Thanks!
-Max

P.S: I'm pretty new around here, and even if I did some homework it's possible
that I missed something in one of the previous threads. If this is the case just
point me to them, and I'd be glad to read them ;-)

[ojars]

Consider a battery tender -- I took the advice found in these fora and purchased a Battery Tender Plus a few years ago. I am still running the stock battery.

[TheViper]

He stated that his car is parked outside.
Michael

Originally Posted by ojars

Consider a battery tender -- I took the advice found in these fora and purchased a Battery Tender Plus a few years ago. I am still running the stock battery.

[ojars]

Whoops! An oversight on my part. It is easy to imagine a parking area with no easy electric access and perhaps that is the case for sunmax.

[SobeLotus]

I used the battery tender as well here in Miami. I still have my 2005 factory battery. I cannot complain. I sometimes don't drive it in two weeks. Good luck.

[TimMullen]

Originally Posted by TheViper

He stated that his car is parked outside.

The a good choice is the Solar powered Battery MINDer (or the other solar powered battery maintainers) : BatteryMINDer 12 Volt 15 Watt Solar Battery Charger: BatteryMart.com

[TheViper]

However he stated it was under a car cover.
Michael

Originally Posted by TimMullen

The a good choice is the Solar powered Battery MINDer (or the other solar powered battery maintainers) : BatteryMINDer 12 Volt 15 Watt Solar Battery Charger: BatteryMart.com

[ojars]

The solar powered Battery Minder is intriguing. Looks like a good match for those of us in Southern Florida. The solar array need only be positioned outside the car cover. Anybody actually have one and use it?

[sunmax]

Hi there Lotus guys!

Thank you very much for the prompt feedback.

>> I don't know if you have read this Battery Choices & Information

I used its table to choose the Optima Y D35 as the best compromise for my Elise time.
After you pointed that out I went through all the posts in that thread. Very informative!

>> Consider a battery tender -

Yes, unluckily I am far from any power outlet :-(

I am familiar with tenders, I have one on my MR2 in Europe so that when I go back,
it's always ready to start! (I wish it was an Elise though...)

The Solar panel option is indeed intriguing, but even if I put it on the top of Weathershield
cover I would still be a bit concerned about the sudden wind gusts here in Miami Beach...

I think the way for me to go is to use the green knob instead of the alarm (which I'd leave off
to reduce drain) for the times of the year when I can drive the Lotus once a week, and then
to remove the fuse and completely cut off the battery if I should be away for over 2 weeks.

>> No power to the ECU is no problem

Cool. One final question on this then I am set ;-)

I remember that last year a Lotus dealer had to upgrade some sw
(forgive my imprecise lingo!) in the ECU - is the update going to
get lost if I cut the power off for 2 weeks ?

Is there any cons in leaving the Elise for so much time without any power ?

Very impressed with your support guys! Best car forum ever.

Long live the Lotus!
-max

[TimMullen]

Originally Posted by sunmax

I remember that last year a Lotus dealer had to upgrade some sw (forgive my imprecise lingo!) in the ECU - is the update going to get lost if I cut the power off for 2 weeks ?

No. The Updates in the ECU are written to (erasable) permanent memory. The SW remains hard coded in the ECU until it is intentionally overwritten, and it is not dependent on a power source.

Most ECUs have "temporary" memory on "fine" tuning parameters that are lost when you disconnect the battery, but that just means that it would have to re-learn the adjustments again after battery power is restored.

[TheViper]

One additional point, the Optima Yellow Top is a true deep cycle battery. This means that it can be safely discharged many times without it causing deterioration due to sulfation.
Cheers,
Michael