Keeping car battery from discharging

Why not simply buy a 'battery diconnect'? Designed for the job, and fitted in seconds.

Such as the one I have:

On things which do have a memory, you'll loose it anyway if you let the battery go flat. And a disconnected battery will hold its charge for many months.

a modern battery will, but not an old niCad.

What about lead acid, which I believe is more common in cars?

Just be aware that the engine management system will have to re-learn some parameters based on your driving when the battery is disconnected. The engine may appear to run differently in the first 15 minutes of driving after a battery re-connection.

Aren't we talking about lead-acid car betteries here? ... anyway I

"appear" to run differently?? Surely it really does run differently! :-)

You're wrong about that with the eneloops.

And wrong about that too.

Isn't it mostly easier to drive the car a bit?

When I have to go out to get some food, I make sure my route is the longer way round to ensure that the car has opportunity to recharge.

Unless there is something preventing that, it seems to the simplest and best approach.

Correct, NiCd didn't have much of a discharge problem, and the toxic cadmium was their demise. They were also much criticised for their memory effect, which was exaggerated and in reality was not something end users need be concerned about at all.

NT

We were talking about cars. A decent lead acid will last many months and still start the car if fully charged then disconnected. Their self discharge rate is very low.

I keep on reading this sort of thing, but have never experienced it. Have you?

For those who prefer to trickle charge batteries I can vouch for CTEK

when I eventually re-connect my car battery, I'll find out the answer. Or, possibly, just an answer.

All I can say - comparing like with like I hope - is that my present electric tootbrush with a lithium ion battery runs far longer between charges and has lasted far longer than any nickel cadmium powered model ever did.

There is an excellent Morrisons 12 miles from here with a bit of 70 mph dual carriageway on the way. I always think of some very specific item that I need and may not be in stock elsewhere!

Come to think if it, what are the supermarkets like in Durham? .

Not the best way to re-charge the battery since it needs time. Your alternator will put out the maximum charge at quite low speeds.

Thanks for that. I did wonder. Only a section of 70 mph. Lot of 30, short stretch of 40 then a bit of 50 then a fairly short burst of 70 then 40 then 30 so I thought this was a good mix.

Did I read somewhere that full output is achieved at about 15 mph?