Electronic Wizards - Split Charge

[jims-terrano]

Right I need a little advice please. My project truck has split charge and a second battery which is causing a few problems of late and I’ve wanted to fit a tell tale lamp since fitting but not too sure.
I’ve got a tiny little split charge controller that allegedly handles 30 amp but I’m pretty sure something so tiny it cannot possibly switch 30 amps. So I fitted a relay between my two batteries that the controller switches.

So I can fit a lamp in circuit so that I know when the controller is feeding power to the relay which is no problem at all. What I want to do is fit a lamp to indicate when my relay has switched which is where the problem is. Think about it stick a lamp directly there between relay and second battery the lamp will be lit all the time. It may not be possible, I’ve thought about using a diode but can’t logically think this would work either.

That’ll get people scratching their heads :doh

 

[kitchenman]

Best way is to fit a second alt on the aircon bracket, works on my mav

diode should work, I have one on my motorbike

 

[Lazy-Ferret]

When I did both the dual battery conversions on our cars, I went through the same thoughts... The problem is, Diodes drop about 0.7v across each one, and not only that, but high current ones tend to be expensive. The 0.7v drop might not sound a lot, but basically that is most of the difference between a fully charged, and a nearly flat battery, so it then confuses any voltages sensitive stuff. Not only that, but I could only find a way of doing it with at least 2 diodes in line at any time.

The best way I found, that was both cheap and reliable, was 2 LED voltage meters, one on each battery. When the car is stopped, and the charge relay is dropped out, the batteries will discharge at different rates, so you will see a different voltage on each battery when you check it after the car is stopped for any time. When the batteries are connected, they will both read the same all the time, and if the engine is running, then they will both charge with the same raised voltage.

On Suz's car, I got 2 identical meters, and connected them to a power supply, and in the back of the meters was a very tiny potentiometer, which with gentle tweeking, I got the meters to read absolutely identically.

Other than that, as kitchenman says, 2 alternators, both charging a battery each, and then you can have 2 charge warning lights from the alternator.

 

[solarman216]

I like that idea Clive, very nice simple and accurate, Rick

 

[Fez_uk]

Why don't you stick the lamp between the relay & 30 amp controller?

 

[jims-terrano]

Yeah that tell me the controller is switching but I want to make sure the relay is switching, Clive’s solution maybe the easiest answer.