"Bill Wright" wrote in message
news
On 14/12/2016 04:57, Rod Speed wrote:
Bill Wright wrote
newshound wrote

With this arrangement, isn't there a danger that if one battery
deteriorates (e.g. a cell shorting out) it will knacker the good one?

Yes. But if they're the same age and type you wouldn't worry about
which one had failed, you'd simply change both.

I wonder if the batteries are knackered anyway, or at least well past
their best. After all, a decent battery of the correct size should
start the engine without further help.

It isnt a car, it’s a piece of farm machinery that doesn’t get used a
lot.

Yes you said. It doesn't really matter.

Corse it does.

If it was designed to start on one battery that should be all it needs.

And if it never was designed to start on one battery, it wouldn't be.

If one battery won't produce enough current to turn the engine over fast
enough

You don’t know that is the problem.

then there's something wrong.

Not if was always designed to need two batterys in parallel to start it.

The battery, the cables, the starter, or the engine.

You don’t know that there is any fault at all.

If it doesn't run for long enough to recharge the battery after starting

That does appear to be the problem.

then yes, you'll need some auxiliary charging. The little solar chargers
aren't much use. The bigger ones are better. Unless the vehicle is in a
barn!

In which case it should be possible to plug it in in
the barn to allow it to be charged when in there.

Leakage is also an issue, especially if the electrics are damp. I have
leakage on the motorhome of 0.001 to 0.002A in winter, which would be
significant if I didn't use the vehicle for several months.