DC to Dc Chargers - Dash indications

[101RRS]

I may have asked this before but I cannot find it.

For the auto electricians - in my 24v 101, I am intending to use a 24v to 12v 60 amp 3 stage battery charger to charge to 12v auxiliary battery. What I also want is to have an indicator light on the dash that works like an ignition light - so when the charger is not charging (with ignition on) the light illuminates on the dash and when the charger is charging the light does out.

I have an old electronic 3AW relay unit that can operate the light but the problem is that if the charger is not working, the battery is then providing power to the 3AW unit and and prevents the indicator light from coming on. I thought about putting in a 100amp diode into the cables from the charger to the battery to prevent power running back to the charger when charging is lost but I believe that with a diode of that size I can expect a voltage loss of about 2v which is too much to keep the battery topped up.

So can the auto elects suggest a circuit that can provide an ignition style light (off when charging, on when not charging) for a DC DC system.

Yes I can put in low voltage systems that can alert me when voltages in the charging system drop off and I may do that but this thread is only about having an ignition style indicator light. I want a dash indicator system that will alert me immediately the charger has stopped charging - just like would happen if an alternator stopped charging.

Thanks

Garry

[bee utey]

If you used a VSR like off a dual battery isolator, attach the electronic bit to the 12V battery and make it drive a NC relay to run a charge warning light off the 24V side. No idea if Redarc would sell just the electronic bit or if an electronics shop would have something suitable.

[101RRS]

Thanks for that - I have never had a dual battery system so I will need to research a bit more on what you have suggested and see what I can find out.

Cheers

Garry

[bee utey]

I've found a Jaycar kit which seems to fit the bill:

Universal Voltage Switch | Jaycar Electronics (https://www.jaycar.com.au/universal-voltage-switch/p/KC5377)

[101RRS]

Thanks - I will check it out - looks though it would continue to work off power from the battery even if the charger stopped working until battery voltage triggered the unit at the preset voltage.

Cheers

garry

[Red90]

Just add a little voltmeter. Much more useful.

[bee utey]

Or you could just open the case of the charger, tap into the "on" indicator and wire it to the dash.

[101RRS]

Just add a little voltmeter. Much more useful.

Already have that but doesn't tell you it is not charging until the voltage drop becomes noticeable - I want a light that comes on to catch my eye if there is no charging - just like a an ignition light comes on if the alternator stops charging - even when there is a voltmeter in the system.

Cheers

Garry

[damienb]

Connect the ESR in parallel with diodes to isolate.

[101RRS]

Or you could just open the case of the charger, tap into the "on" indicator and wire it to the dash.
Thanks Jilden - yes I considered that very early in the process but the little indicator light on the charger indicates it has power going into it and not that is it producing output.

WELL I AM A DUMMY I just typed the above then :idea:.

I haven't actually pulled the charger out of its storage in a few years but I knew it had an ON light.

Well it actually has an input indicator light but [B]ALSO an output indicator light (doh). So as you suggested I will just tap into this light with a micro relay that is off with power to it to activate a LED in the dash.

As they say Prior Preparation Prevents **** Poor Performance (the 6 Ps) - should have double checked before asking but glad I did.

Thanks

Garry

[Red90]

The voltmeter tells you everything. You could add a low voltage alarm but that is crazy overkill.

An alternator light only tells you that the alternator is not on or has a bad diode. It does not tell you it is not charging. There are many types of failure where the light will not come on.