Nice Dave, I like that very much.
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Electric Curiosity
- Thread starter JOHN OF LONDON
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. I will definately go your route. Thanks very much.JOHN OF LONDON
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Just tidying this thread up really. My AGM battery proved to have died of old age so I bought a new Numax leisure and marine 100ah conventional battery. Its wired through a 100amp circuit breaker under the bonnet with 16mm cable to the back where the battery connects with an anderson connector to a 100amp fused battery connector. The battery is earthed through the frame via the anderson.
Auxiliaries are wired through a low voltage cut off which disconnects the output side from the battery at 11V so battery is not overdischarged.
Wiring the Ammeter so it only measures the current flowing to the Numax shows that the maximum current flow with the Numax at 11V is a transient 35Amps which rapidly drops back to about 20Amps. Over the course of a days driving the current slowly diminishes, eventually to a trickle at 1.5 to 2Amps. Alternator output from the new 125Amp alternator remains at 14.4V throughout. Out of interest I temporarily connected the Numax directly, through the Ammeter, with a short length of very heavy cable, and both wires of a heavy duty jump lead for the earth. This made virtually no difference to the Amps going to the Numax!
Not sure what I make of these results but it does show that fully charging a smallish auxiliary battery takes longer than I expected.
Auxiliaries are wired through a low voltage cut off which disconnects the output side from the battery at 11V so battery is not overdischarged.
Wiring the Ammeter so it only measures the current flowing to the Numax shows that the maximum current flow with the Numax at 11V is a transient 35Amps which rapidly drops back to about 20Amps. Over the course of a days driving the current slowly diminishes, eventually to a trickle at 1.5 to 2Amps. Alternator output from the new 125Amp alternator remains at 14.4V throughout. Out of interest I temporarily connected the Numax directly, through the Ammeter, with a short length of very heavy cable, and both wires of a heavy duty jump lead for the earth. This made virtually no difference to the Amps going to the Numax!
Not sure what I make of these results but it does show that fully charging a smallish auxiliary battery takes longer than I expected.
When you connect two batteries together, the alternator 'see's' them as one, if one battery is fully charged and you connect in a flat battery, terminal voltage across the two will drop but not by much. So the alternator will limit the output of amperage, this slows the time taken to recharge, hence mixing battery size/type/capacity is never a good idea.
Regards
Dave
Regards
Dave
Last edited:
To add to this, simply connecting one charged battery to a discharged battery will see them level out over time as the charged battery charges the discharged one. Think of it as connecting two water tanks together through a skinny pipe. The charge will pass quite quickly at first, depending on the voltage of the charged battery and whether the discharged battery starts gassing (accepting a charge). For a faulty battery, think of the empty tank having a hole in it. Both batteries end up discharged and if left unnoticed will be both over discharged and damaged.
JOHN OF LONDON
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Sorry, didn't make that too clear. Auxiliary battery only gets connected to the main batteries when the alternater is charging and activates the voltage sensentive 100amp circuit breaker
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