Ian Jackson expressed precisely :
In message , Gib Bogle
writes
On 26/12/2010 12:01 a.m., Ian Jackson wrote:
In message , Gib Bogle
writes
On 24/12/2010 1:51 p.m., george [dicegeorge] wrote:
On 23/12/10 23:39, Adrian C wrote:
On 23/12/2010 22:01, ARWadsworth wrote:
As per the header. The neighbour has got a knackered car battery but
he is
too nervous to just buy and fit a new one (he wants a main dealer to
swap
it!).


Probably it's either

1) he's worried the anti-theft radio will lose it's marbles and he
.
As car electronics gets cleverer and cleverer
disconnecting the battery to swap it for a new one may break more things
than
the radio.

[g]

Yeah, somehow that doesn't seems very clever to me.

I wonder how flat the battery has to be to have the same effect as being
disconnected.

Surely there must be a clever way to replace a battery without
disconnecting,
using jumper cables. It might be tricky.

1. Run jumpers from the battery leads to the new battery.
2. Remove leads from old battery.
3. Remove old battery.
4. Install new battery.
5. Here's the tricky part - connect leads to new battery while
maintaining
connection between battery terminals and leads at all times. I'm not sure
how
this should be done.

1. Slacken the bolts on the battery connectors.

2. Make sure that the connectors are loose, but don't disconnect from the
battery terminals.

3. Connect the jumper lead clips to the connectors.

4. Ease the connectors off the battery terminals.

5. Replace battery.

6. Put the connectors on the battery, making sure that they are a push fit
(tighten/slacken bolts as necessary).

This is the tricky step. At this point there is a jumper lead clip on the
battery terminal, and the other clip is on the battery connector. You have
to get the connector onto the battery terminal which has a jumper clip on
it. The clips are usually quite large, comparable in size with the
terminal. Care will be needed to make sure that the contact between the
connector and the terminal is maintained while the clip is removed from the
terminal.

Before starting the job, you obviously need to assess the possible snags that
might arise, and prepare for them. The cigar lighter connection is obviously
easier, provided it works (which it ought to).

Only if the lighter socket is permanently live!

A better method than connecting across the battery leads, is to find
the under-bonnet main fuse box and seeing if there is an accessible
live all the time bus bar. Connect to that and a good ground/ earthed
engine part.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk