dual battery charge light feed issue

I've hooked up a dual battery system by connecting the negs together and to ground and the positives via fuses to a 200 amp relay with it's switch going to the positive feed to the charge light on the dash.

Now if I touch the switch wire from the relay to 12v it switches..... if I touch it to the feed wire going to the clocks it switches....

BUT

If I turn the ignition on with the relay's switch connection already connected to the warning light feed to the dash then the relay doesn't get enough current to switch. If I disconnect it and re-connect it it switches.

AND

The not charging light is on whenever the wire is connected to the relay. It goes on even if I connect the dash warning light to a 12v tester! It's as if there is a very poor connection from the alternator.


Do you normally connect it straight to the alternator?

i wouldn't hook into the warning lamp. why not just connect it to an ignition live since you only want it connected when the engines on.

other ways are voltage sensing relays which switch by themselves or stick a manual isolator in, where you turn a key or just leave them connected all the time.

what's it for anyway?

mine goes to the single wire in the back of the alternator.
relay only energises when the engine is running.

why would you need a dual battery system for the standard truck , unless you are winching or have a fleet of flood lights on your roof and bumper or running a few hundred watts of audio Power in the back ?
steve

rogerdee said:

why would you need a dual battery system for the standard truck , unless you are winching or have a fleet of flood lights on your roof and bumper or running a few hundred watts of audio Power in the back ?
steve

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I have a winch bumper ready for a winch early in the new year plus 12 spots/work lights plus the stuff mentioned earlier

What engine do you have? If its a Td5 then the alternator is an 'intelligent' one and doesn't give an output unless its needed. You need to use an ignition switched live rather than a feed off the alternator.

The 300Tdi has a conventional alternator IIRC so this doesn't apply.

ArticFox said:

What engine do you have? If its a Td5 then the alternator is an 'intelligent' one and doesn't give an output unless its needed. You need to use an ignition switched live rather than a feed off the alternator.

The 300Tdi has a conventional alternator IIRC so this doesn't apply.

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It's a 300TDi, I've previously installed similar setups and had no issues. The problem is that the dash light gets a nice clean 12v from the ignition live then the 12v "charging" light cancels this out hence the light going off. If I draw any current off the "charging" wire it pulls the voltage down and the light comes on at various brightnesses. I have alternative options involving a relay.

I am eventually going to fit a 4 position rotary switch (I have some already) with positions for "no connection", "on", "ignition on" and "charge on/normal". It was raining yesterday whilst I was trying to sort it and other issues. I'm going back out after a coffee to fix this and the rear washer button then depending on the weather I have other shiny parts waiting for installation

The charge light is part of the circuit whose only role is to 'excite' the alternator.

You should not add anything to it!

If yoy want to put a charge relay in, you need to leave that circuit alone, and hook the relay into a switched +ive on the ignition.

You will need a feed from one of the batteries to power up the alternator and dash warning light, otherwise you could blow the alternator diodes.

Oldseadog said:

The charge light is part of the circuit whose only role is to 'excite' the alternator.

You should not add anything to it!

If yoy want to put a charge relay in, you need to leave that circuit alone, and hook the relay into a switched +ive on the ignition.

You will need a feed from one of the batteries to power up the alternator and dash warning light, otherwise you could blow the alternator diodes.

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Thanks. I'm mulling over my options. Ignition live via a "don't connect" switch seems like the safest and a simple fix.

just use a caravan type switcher to switch your larger relay

that way it only chargers the 2nd battery when the engine is running and the wiring is simple as it can all be done in the box