Thread: Dual Battery System - Disco Series 2A

Hi drivesafe (what is your name?)

I did some more testing, a bit more scientific this time and made sure all termials I tested from were clean. This was the results

Firstly main battery before turning engin on:

Main battery - 12.01v

Next with engine revving at 1500RPM

Back of alternator - 13.57v
Main Battery - 13.50v
Battery in rear of car - 13.47v


Does this seem resonable or still too low. You seem to know what you are talking about. Do you think the charge might be too low to be charging up the second orbital in the back which is the reason it failed so quick.
I have never had a problem starting the car and the winch (which has had some serious workouts) has never had a problem and only runs off the main battery.

Is there anyone else out there with V8 series 2 disco's which could measure voltage at the back of the alternator with engine running.

thanks,

Hi Walker, just a couple of questions.

Was the vehicle sitting around for a day or two before you tested the main battery or had you been using the auxiliary battery and pulled the main battery down otherwise 12.1 is just OK and a sign that your battery is not holding it’s charge.

A stationary cranking battery after 24 hours should have at the very least 12.25 volts but more likely to be at 12.5 volts.

Next because your main battery was low at the time of stating the Disco, you would probably need to take the Disco for a good 1 hour drive.

Then measure the batteries while the motor is still running.

After an hour and revving up to around 1500 rpm, you should get a reading of around 14 volts or there abouts.

You 13 volt readings are still to low but this may change once you take the Disco for a drive.

Cheers.

The car had been driven today and is driven everyday. There has been no load on the aux battery and when I dont think it would have brought down the voltage of the main battery as they are isolated when engine is not going.

I will try the driving around thing and will also disconnect the aux battery and see what difference it makes.

As I said I have never had a problem with starting or winching so???????

The amin battery on Disco's is a lead-calcium battery so maybe this is different. I am going to get an Arrid charger anyway to get a better voltage to the aux battery and that should sort it all out.

Before you do any thing, you would be better off sorting out the charging voltage first and once that’s done you probably wont need anything beyond what you already have.

The cable in your pictures seems to be thick enough and if you are having problems now, you will still have the same problems after you do any adding to the system.
Cheers.

But lets assume that the output voltage from the alternator is OK as starting etc is all ok and this is the same voltage I had when I checked 5 months ago.

If this is the case then putting a booster charger before the second deep cycle battery will make sure it remains properly charged at all times.

Does that make sense or am I missing something?

try measuring voltage with a different voltmeter.

Hi Walker, again before you do anything get your voltage levels at the front of the Disco sorted first.

If you don’t, adding a booster will probably just make things worse.

If after you fix the voltage levels, you still think you need the booster, try Engel voltage booster. It’s about half the price.

For my money, I still think that once you sort out the problem with the voltage, you won’t need another thing.

cheers

Ok, thanks Tony. I tried reading with 4 different meters (I'm am an electrician so i have a few) and they all read similar.

I just disconnected the rear Aux. battery and tested again. I had a slight increase and had 13.84v at the back of the alternator at 1500RPM.

I looked up the RAVE manual I have and I am spot on the money, according to the manual I should have 13.8v at the alternator so I dont have a problem. The problem may be that it is still not enough to properly charge a fully sealed glass mat battery.

The Engel chargers are no good. They are only designed to charge up the small battery packs provided by engel and not a car battery.