Battery - to remove or leave?!!

Unsure what to do about this, any advice please…will be leaving my mx5 in the barn (covered) for about 7 - 8 weeks, don’t really want to disconnect the battery incase it causes a problem when reconnecting, and also the alarm needs to be armed, does anyone know if it will it cause any problems leaving it connected for this period of time.   Thanks in advance

Unfortunately you can’t have it both ways.For that length of time I would disconnect the battery.This will cause no issues on re-connection,but obviously the alarm will not be active,although the immobiliser will.

Awkward one.  With the battery connected and the alarm set, the battery will most probably be flat after 4 or 5 weeks.  If you disconnect the battery and there is no alarm set, you could invalidate your insurance.

If you have power to the barn, your best bet is a smart charger set to maintenance mode. This will keep the battery charged and the alarm working. (No need to disconnect the battery with a smart charger.)

if no power to barn…buy a solar powered jobbie

Good idea





Might be missing something but how would a solar power charger work if the car’s in a barn


Use a 50 meter extension lead?

i would assume the solar panel is on an extended wire to charging unit then wire to car…google is your friend.

As we’re into creative thinking I suppose you could rig up a light from the battery to shine on the solar power charger which then charges the battery - simple

I agree with Creazy’s thoughts. This time of year my MX5 can be in the garage for 2 - 3 weeks before it gets an outing and I had a couple of close calls with the battery being almost flat. I reckoned this was because the alarm drains the battery so I bought a smart charger and never looked back. Brilliant bit of kit and highly recommended. I bought the CTEK MXS 5.0 together with the optional hard wiring kit (basically you make a permanent connection between the battery and a connector under the bonnet which you can simply plug in to the charger cable. The charger also has temperature sensitive charging programmes. I found that I could close the bonnet fully without the cable or the car getting damaged and thus still use the alarm. Hope that helps.

If its in secure garage why set alarm !

…because the small print in your insurance policy states that when left unattended, the vehicle must be fully secured at all times.  Every security device that you declare to your insurers affects your premium and it is conditional that these devices are always used; even in a locked garage!


If your ICE has a security code, make a note of it.

If the battery is removed or flats out, the ICE may think it’s stolen.


If it was mine, I’d leave the battery connected, and set the alarm.  It may well last most of your absence.

But I’d also remove the fuel injection fuse, and maybe jack up, remove a wheel, and it store elsewhere. 

If insurance is the concern I would assume that if you set the car alarm and then the battery dies so the alarm does not work anymore the insurance company could not nullify your policy since you’ve done everything you could to be responsible.  More to the point if that situation were to happen the car would be a safer risk because it couldn’t be started even if someone broke into it.  Therefore if it were me I’d just set it and if when you came back just bring some jump leads or one of those pocket size battery pack starters and off you go again.

Thanks for all the suggestions!  been discussing this with my other half, we don’t have electric in the barn, didn’t want to disconnect the battery - worried about the security code which we don’t have…does anyone know where we can find this - is there a way of accessing it before the battery is disconnected - if we decide to do this?

As a last resort we thought we might keep the battery connected and then if it doesn’t have enough power to turn the engine over use jump leads to start it, thus not disconnecting the battery, but there will come a time when the battery will have to be renewed and we will need the code…so any suggestions on how to access the code please!!!..Cheers

Depends whether you bought the car new, or second hand? If new - did you set a radio code? If second hand, then the previous owner may have set a code, which does mean you have a problem.
Solving it depends on which model you have, though base instructions may apply to all models, but I don’t know that, so unless you tell us which model (Mk) you have, then you may have to wait to find out - when you return.
A solar charger seems a good idea, but it needs to face south mainly, and if you mount it horizontal or at an angle, and it snows, it’s debatable if it will carry on working till the snow clears. Which makes me wonder about all these solar panels on everyone’s roof - - - -.

Going back to my school physics.  Surely you could add an additional battery or batteries to extend the endurance by wiring them in parallel?  Any electricians around to say if it’s possible and if so how to do it?

Rog. Possible, but an expensive way to do it. Also, who buys batteries at £40/50/60 a time just for five weeks? The car battery is less A/H so will discharge faster, so other batteries have to carry the load - for five weeks, you’d need two to be safe.

Also, probably because they’re cheaper, lead acid unvented, so added risk of corrosion in the boot, a A solar charger is cheaper, but needs a minimum 0 .5 amp output at 12V.

Snow was mentioned on the forecast for the next weekend. Snow is opaque, to a point.

Car thieves  don’t walk around with a car battery in their pocket - or their hand either. Me - I’d disconnect and remove the battery and stick it on a top-up charger in the house while I was away. If I was worried about insurance, I’d remove the spark plug leads as well, seeing as cars don’t have distributors any more. (you could remove the rotor which would kill the car dead)