FLATISH BATTERY START

[djk3816]

My car (1960) is safely locked in an underground garage with a very steep ramp up to the road and no electricity supply. However, I will not be able to get to the car(100 miles away) until the current lockdown is over and the car has already stood idle for 6 weeks.
All the electricals are switched off but I expect the battery to be nearly flat by the time the present crisis is over.
If when I can get to the car I take with me a spare charged battery that I have and can I safely connect the good battery to the depleted battery using jump leads and start it without damaging the electrical circuits/components ?
I believe the process is to connect from the negative donor battery to the car negative followed by the same process for the live side (?) I would rather do this than just swap the batteries over as (a) the garage is dark and cramped and (b) I would prefer to keep the original battery insitu anyway. Thoughts/Ideas /advice ?

[alawrence10360]

If your battery is healthy it should be ok

[alawrence10360]

If it was me I would connect pos first (assuming it’s a negative earth vehicle)because when making the final connection if you inadvertently touch the metal work you will not cause a short circuit

[Biggles1957]

Connect earth last

Disconnect earth first

[geoberni]

Big thing to watch will be if the Moggie is Positive Earth still that you 'cross connect' the cables for a Jump start if using a modern car as the Starter.

There shouldn't be anything (certainly not on the Moggie) on either vehicle that can be damaged, IF you know what you are doing. But you must make sure the Batteries are connected Pos to Pos and Neg to Neg.

If, as you said, you're just taking a Spare Battery with you, then hopefully this will not be an issue.
However, be aware that if doing that then the moment you connect the good battery to the discharged battery, the duff one will be pulling power from the good one as well as the starter motor trying to turn the engine over.

Shouldn't be a problem with a little engine like a Moggie, but needs to be remembered.
That's why when doing a 'Jump Start' you have the donor vehicle running, preferably with a little throttle on too.

[simmitc]

Take the spare batteyr and jump leads with you just in case. As long as your battery was charged and in good condition when the car was parked, and you do not have any accessories such as a radio that will drain the battery (modern ones drain power even when switched off) or a clock, then the car should start. If it's slightly flat then you could use the starting handle.

If using the jump leads, then connect the non-earther lead first, earth side second. Start the car. disconnect earth lead first and non-earth second. Once started, you can disconnect the second battery immediately. When disconnecting the leads, remove both ends of each lead to avoid the risk of shirting them together. Go for a good run the get the fitted battery charged, and carry the spare with you until that charge is complete.

If the garage is dark, then take a torch with you

[Sleeper]

Do you not have a starting handle ?

John ;-)

[geoberni]

Do you not have a starting handle ?

John ;-)

I think they're overrated with timing changes over the years for fuel changes. I've tried several times to hand crank Basil since we brought him, without success.

[myoldjalopy]

Well, I dunno.......I've always been successful with it. Has come in useful a few times over the years when out in the middle of BFN with a flat battery! Of course it helps if timing, valve clearances, points and plug gaps are spot on.....

[bufferzone]

Here is a most helpful item just for these situations

https://www.xenonpro.com/js1001-10000-m ... ttery-pack

[geoberni]

Well, I dunno.......I've always been successful with it. Has come in useful a few times over the years when out in the middle of BFN with a flat battery! Of course it helps if timing, valve clearances, points and plug gaps are spot on.....

Perhaps I should try again sometime...

[oliver90owner]

As in a recent thread, connect the earth lead to a suitable point away from the battery and disconnect first - to prevent risk of sparks at the battery terminals (of either battery).

[myoldjalopy]

Well, I dunno.......I've always been successful with it. Has come in useful a few times over the years when out in the middle of BFN with a flat battery! Of course it helps if timing, valve clearances, points and plug gaps are spot on.....

Perhaps I should try again sometime...

This article may be useful regards technique, especially how to grasp the handle and when to give it some oomph: https://www.oldclassiccar.co.uk/starting-engine.htm