running another charge wire to another battery

[4sum4]

can you run another charge wire to another battery off the one alternater,Say if one goes flat while camping or what ever you still have another fully charged to jump off

[cpt-mud]

just set up a basic dual battery system, much eaiser.

[-Scott-]

If the alternator is electrically connected to both batteries, without any form of isolating device, then both batteries are electrically connected - you'll drain them both together.

There's also the issue of battery sense voltage. The regulator looks at the battery voltage and adjusts the alternator output to suit. With two batteries connected directly to the alternator which one will your regulator monitor?

Traditional dual battery systems connect the second battery across the first, so both are (nominally) at whatever voltage the alternator is sensing. If the batteries are joined at the alternator, rather than to each other, the regulator can only sense the voltage of one.

That's not necessarily a huge problem, but if they're at massively different states of charge the charging rate could be less than optimum. For example, if your main battery is fully charged but your secondary is not the alternator will basically be in "trickle" mode (let the arguments begin ) and the second battery will be charging much slower than it otherwise could.

[chunderlicious]

oe f my batteries was rooted, i had my second battery joined at the alt. it then drained my main battery which has now stuffed it.

[j-top paj]

just set up a basic dual battery system, much eaiser.

x2