Battery isolation switch

[Gunfleet]

I don't think youre right there Vyv - there are vehicles with tailgates, heavy duty vhf, even caravan electrical supply with multiple batteries that require auto electricians to do more than the bog standard. Any trained auto electrician should be able to do change the sensing on an alternator. My local one certainly can.

 

[halcyon]

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Halcyon, your diagram is missing the charge cables as far as I can see, and it is very hard to understand, so if it was drawen more precisley it would probably be more complicated than mine, and not give as many simple to use options as mine.

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You do not touch the charge cable.

The alternator output goes as standard to the engine battery via starter motor feed. You do not disconnect any cable, so the alternator is always connected to the engine battery.

So sorry, no more cable or mods are required, what you see is all you need. Volt drop is minimum, so unless you have a very low set alternator, you do not need battery sensing, etc.

Brian

 

[halcyon]

Some more detail here .

Brian

 

[Clyde_Wanderer]

Halcyon.
Where is the alternater in your diagram, and what is the grey unit with 2 blue wires comming from it? and what is the unit that the red batt cables are attached to?
Cheers, C_W

 

[halcyon]

The alternator is were the engine manufacture fitted it to, the battery terminal on the starter motor. The grey unit is the control box, the other thing is the relay.

Start engine, alternator charges the engine battery, at set voltage batteries are connected in parallel. Charge takes the least line of resistance and flows to service battery till it's level comes up to the engine battery, both banks then take a charge. stop engine, relay drops out to isolate the batteries.
Put service battery on charge, at set voltage relay engaged to charge the engine battery, charge ceases, relay drops out.
If low engine battery, press switch on blue wires and charge relay comes in to provide link starting from service battery.
Control box has a tapping to operate a relay to drop out high / part load at low battery level.
Volt drop on contacts is 0.04 volt at 100 amp, so a alternator regulating at 14.4 /14.6 volt will not need modifying.

Brian