Thread: Dual Battery System not charging Auxiliary Battery

Who is running a dual battery system in there D3 and how is it performing.

The reason I ask is that I have found that although LRA originally provided me with voltage charging stats, I have found that not only are some D3s charging at even lower voltages, that these lower voltages are causing problems for quite a few Dual Battery Controllers, because the voltage is not rising high enough to turn the controllers on.

This problem has no effect on the D3 but it is stopping the auxiliary battery from being charged.

Cheers.

Originally Posted by drivesafe

Hi jik22 and discomaniac, I’m pretty sure you won’t have any problems with my gear but I am just following up on info that has come to me from a number of different sources.

What’s happening and because of the situation where it happens, my units, because of the way they work, should not be effected but this is what’s occurring and it occurring at the worst possible time.

The vehicle is started in the morning and as it is starting cold, the charge voltage quickly rises to around the 14 volt mark. This is well and truly high enough to turn on any battery isolator. Alls well so far.

Your off on your holidays and drive for a few hours then stop for fuel or a break.

After the break, ( during which time, most battery isolators have cut out because the motor wasn't running ) you start the motor and off you go.

Here’s where the problem is occurring, because the motor is still hot, once the motor is running, the voltage in the newer D3s is not rising much over 13.2 volts which means the other battery isolators are not cutting in again and the auxiliary battery is actually being discharged by the fridge and what ever else may be drawing power from it instead of getting power from the alternator.

The end result is that when you get to your days destination, your auxiliary battery is anything but charge up.

The reason for posting this thread is to try to get as much info as I can on this situation.

BTW a similar problem is also effecting auxiliary battery charging it new Toyota cruises.

Cheers.

Although I own a D2, this is exactly how things are happening with my auxiliary battery setup.

I have gone overkill on wiring - 18mmsq. using a Traxide SC40 coupled to a Fullriver 120amp/h.

I have a newish battery - 1.5 years - new 120amp alternator and the whole system does not work efficiently.

I have had my discussion with "12 volt power efficiency" and I am over it.

Why?

Just a couple of questions....

What voltage does a battery need to charge? = 13.8 or more.

What voltage should your alternator put out to charge that battery? = 13.8 or more.

Has anyone heard of this....

"To get heaps of current into a battery you need to supply it with 14.5 V or higher. Most vehicle alternators will not produce this sort of output wen the motor is warmed up (due to alternator temperature compensation.) So the battery will not absorb the full current output available from a vehicle alternator."


Why is my Commorore VT 2000 model has a voltage of 14.2 at the battery yet my D2 has 12.8 - 13.6 at the battery which is all dependent on the temperature. The only time I have seen 14 plus volts was when it was about 1 degree and that was at the cig lighter!

I have just been through to Alice Springs and the whole auxiliary battery set up was a disaster. Even after driving for 6 hours the aux. battery would be reading 12.4 at best. How long do you think the battery would last just running the Engel fridge. It lasted less than 4 hours before the cutout tripped out at 11.6 which means the aux battery is technically flat i.e after this point you are damaging the battery.

As you could possibly tell I am totally frustrated with this whole project. I have collected my research and the finding with my experience firmly confirm you cannot fully charge a battery (100%) by using your altenator. There are too many computers controlling the current for it to charge.

Over to you.