Thread: Discovery 2 Battery Charge to 70%

Hi Jake, what are the actual voltage readings and when are you taking?

12.5v at the moment, been out for a drive and it's at 75%

Hi Jake and you need to take a voltage reading when you D2 has not had the motor running for at least 12 hours.

Let us know the voltage reading then.

Cheers, Tim.

After reading this I went and checked mine.

I am running a Redarc isolator, SCA N70ZZ main battery and a Fullriver Aux battery.

Disco has been sitting all night and both batteries show 12.3V.

Denso Alternators

I notice Denso say charging is at a constant 13.5 Volts..

Originally Posted by DiscoKym

Disco has been sitting all night and both batteries show 12.3V.

Denso Alternators

I notice Denso say charging is at a constant 13.5 Volts..

Hi Kym and it is actually very common for vehicles, that are not driven enough, to have cranking battery voltages of 12.2v.

I had a customer phone me this last week after he had his D4 at the dealers because his cranking battery kept going flat.

He was told by the service person that my isolator was causing the problem because the cranking battery must never be discharged below 12.5v.

This is a total load of crap, based on pure ignorance.

If the same person went out into the sales yard and measured the voltage of every LR there, he would NOT find a single vehicle with a rested voltage of higher than 12.3v and most would be 12.1v to 12.2v.

BTW, the customer has had my isolator disconnected for nearly a month now, Because the same people made the same claim last time he went there with the same problem, and still his cranking battery is still not charging.

There is a problem with the software controlling the alternators in many of the D4s, and this has nothing to do with having a dual battery system, mine or any other brand.

The problem occurs more times in the UK but it happens here as well and requires a software fix.

One other point Kym, don’t pay too much attention to the 13.5v.

Like nearly all other alternators, the vehicle manufacturer will set a specific operating voltage for an alternator and this can be anything from 13.5v to 14.7v.

The best way to find out what your alternator operates at, is after a continuos drive of more that 30 minutes, pullup, leave the motor idling, turn everything else off, A/C, sound system, lights, and so on.

Then measure the voltage at your cranking battery’s terminals.

This will give you a pretty good indication of the operating voltage of your specific vehicle.

Last car had about 6mm cable and Disco has 8mm or bigger. Neither seemed to have problems with the Relay dropping out.

Neither battery volt meter gets down to 12.7 volts while the engine is running. After the relay cuts in the batteries are usually within .3 volts of each other.

Originally Posted by drivesafe

Hi Kym and it is actually very common for vehicles, that are not driven enough, to have cranking battery voltages of 12.2v.

There is a problem with the software controlling the alternators in many of the D4s, and this has nothing to do with having a dual battery system, mine or any other brand.

The problem occurs more times in the UK but it happens here as well and requires a software fix.

One other point Kym, don’t pay too much attention to the 13.5v.

Then measure the voltage at your cranking battery’s terminals.

This will give you a pretty good indication of the operating voltage of your specific vehicle.

Good info thanks. It still starts and runs fine. From what I read the charging volt drops as the weather get hotter.

Will test as recommended.

I am just adding experience to Shakey's problem.

My setup is working fine, second battery is a new Fullriver running the fridge and UHF. When tested both have same voltage and going by drivesafe all is good in my system.