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The Badger

Charging my second battery

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Trying to find a good solution to make a split charge system. But trying to find how my first battery is charged, from what I understand it's the Brown/White wire from the Ignition, but where does it go to?

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That would depend a lot on which engine you have but normally the charge goes directly form the alternator to the battery, normally via the starter motor terminal. It's not normally connected with the ignition in any way.

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Ok, that is me reading the Hynes manual diagram wrong. It's a 300tdi euro loom. Ok, so if I am understanding correctly, the charge goes back down the starter wire to the first battery?

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Yes, so to add in a second battery you just need a solenoid between the positive of the main battery and the positive of the second and you then trigger that by whatever means you want. I use an Albright HD solenoid between the batteries on mine and trigger it via an off-on-on switch where off isolates the two batteries, first on position is automatic triggered by the voltage on the first battery being above 13 volts and the second on position means it comes on with the ignition, allowing the auxiliary battery to help start the vehicle if required.

The Albright solenoids are waterproof, extremely reliable and can carry a winch current - on my competition motor I use the HD versions to isolate both winches either via a switch on the dash or if I operate the kill switch for the engine.

This is the HD version...
https://www.devon4x4.com/albright-su280-isolator-250a.html

This is the not so HD version which is fine for most uses...
https://www.devon4x4.com/albright-hd-battery-isolator.html

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Forgot to add, when I fit these solenoids I always leave a bit of slack in the battery wires so that, should the need arise, the solenoid can be bypassed simply by moving a cable from one terminal to the other. I've never had one fail but if it does and you're in the middle of nowhere you never know when simply connecting the two batteries together will get you out of a bind.

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Thanks, it's great to get a clear example.

I have two batteries, and I have a HD Albright between the two, the weird thing is the second battery is just not getting charger when I trigger it one via a switch on the dash? I get about a 45amp charge on the first battery, but the second one nothing. Before fitting the solenoid I had a HD manual switch, but it's hard to reach hence fitting the Albright. I left in the HD switch as it will still work if there is no power to put into solenoid.

The batteries are wired up as follows in picture

BatterySetUp.png

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Are you getting any voltage change on the second battery when the solenoid is activated and the engine running ?

Where are you measuring the current ?

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Nope?

A friend who is an auto electrician tested it with his machine, think it was on the positive of the first battery. (but did not pay too much attention as I was fixing my headlights (they are now fixed)

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The thing is that if you measure the current going into the first battery from the alternator and the second battery is connected then you're actually seeing the combined current going into both batteries. The only way to figure out how it's split between the two is to measure the current going through the solenoid/switch and that will give you the proportion of the current that is going into the second battery.

If you have a volt meter, put the negative probe on the positive of the second battery and the positive probe on the positive of the first battery. Start the engine and, with the switch/solenoid open you should see a voltage of somewhere around 2 volts. When you close the switch/solenoid you should see that drop to 0 volts. If it does then it's connecting OK, if it doesn't then you have a high resistance connection so move the negative probe to each side of the solenoid terminal until you get 0 volts. If you get a different reading at each solenoid terminal then the solenoid is faulty, you should only see a 40mV drop at the most across the solenoid and that would be at 200 or more amps flowing through it.

You can also simply measure the voltage across each battery and compare them but the advantage of the above method is that it's more likely to show up a high resistance connection.

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Ok, will try that tomorrow, thanks.

I have a battery level indicator on the first battery and even after a night I get a low power warning on it. I thought that its the second battery draining the first, but then they would have to be connected? I will test before more confusion...

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