Discovery 2 Battery Charge to 70%

[Shakey]

I've got a traxide installed for my dual battery and I've recently added a battery meter/combined plug for my battery charger.

The problem is that the battery meter never shows the main battery as charged above 70% even after a long drive, however when I charge it from the mains it goes to 100% and stays there for days (even after unplugging the charger).

Both batteries are less than 6 months old (and touch wood) I don't have issued starting or the battery light on.

Could anybody help with some trouble shooting tips please?

[drivesafe]

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

[Shakey]

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

[drivesafe]

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.

[DiscoKym]

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 (http://densoautoparts.com/alternators)

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

[drivesafe]

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

Denso Alternators (http://densoautoparts.com/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.

[DiscoKym]

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.

[DiscoKym]

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.

[DiscoKym]

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.

[DiscoKym]

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

Hey Shakey any updates on rested battery voltage as per drivesafe's request?

Sounds like yours is not much different from mine.. :)

[Shakey]

Just measured it again overnight and it's down to 12.28v

[Tombie]

Just so we are clear on definition...

What constitutes a long drive to you?

[Shakey]

An hour (I am a pommy)

[Tombie]

An hour (I am a pommy)


From 70% to full would take several hours above idle. Idle doesn't really help much!

[drivesafe]

Just measured it again overnight and it's down to 12.28v

Hi again Jake and that voltage reading is quite common.

Here is a bit of background and then you can see where I am coming from.

Voltage readings are an indication of the state of charge of the capacity in a battery that can actually be charged.

The problem is that this is no indication of how much of the battery’s total original capacity is actually still available and there is no quick and easy way to work out how much of a battery’s capacity is still available.

With a battery in a good state of charge and at it’s full original capacity, a battery can be discharged down to 40% SoC ( 11.9v ) and still maintain it’s CCA rating.

When a battery’s SoC is below 40%, it no longer has the capacity to maintain it’s CCA “RATING”, but this does not mean you can not start the motor.

I have tested many new vehicles over the last 10 or so years and I have not found a single new vehicle that I could not start using a battery with an SoC of 20% ( 11.58v ).

There is a catch, the batteries were always in good condition. In other words, they were at their maximum capacity.

Now back to your battery.

Through continual short drive use, and a 1 hour drive is not long enough to charge a battery that is in a low state of charge, your battery, like most cranking batteries, is in a poor condition, but it will probably still make it’s CCA rate.

Your battery can actually remain at that level of charge and it will continue to start your motor.

The drawback is that it will probably have a much shorter operating life.

So the only way around this common problem is to give your battery a periodical charge with a battery charger or fit a small solar panel.

While personally prefer a small solar panel, this is in most people's case, not a viable option.

So a battery charger is the way to go, to recondition and maintain your battery at it’s best.

SPECIAL NOTE, to get the best results from battery charger reconditioning, use a SMALL current capacity battery charger, and any cheap, 3 stage battery charger is all you need to get your battery back to a good condition and to increase it’s available capacity.

High current battery chargers do not charge lead acid batteries properly, they just charge them quickly.

[Shakey]

Thanks for that drivesafe, I've got a small 3A solar panel connected for our trip for the next few weeks so I'll see how that goes and then see if I can find if there is a current draw when I get back that is discharging. What is an acceptable drawer on the D2 battery when no key is in the ignition?