flat second battery

**stray dingo** · 26th November 2012, 02:13 PM

I have installed one of Traxides kits, giving second battery, anderson plug and two sockets in the rear. I also have a small fusebox in the cabin running back to the second battery via 4mm wire . This has the kids dvd headrests and the UHF only plugged into it. (rather than running multiple wires back to the battery)

All works good and no problems till now.

This weekend, I plugged my small Waeco Thermoelectric fridge into the accessories socket in the back. (thus back to the second battery) I plugged it in on Thursday arvo to start cooling. Friday arvo I put the food stuffs in it - it was cold and the fan was running. In the wee dark hours of Sat morning before leaving for a drive, I put something else in and found the fan not running and whilst the led lights were on, they weren't as bright as normal. Inside was still cold.
Turning the UHF on, it couldn't even manage a beep.

I unplugged the fridge, left the radio off and headed off. 150km later I tried the radio again figuring that was plenty of time to get some sort of charge in the battery. It turned on, but the screen was too dim to read. Left it off and kept going for another 100km. When I got to my destination, i turned it on again and found the same thing. I picked up another person calling me, but as soon as I hit transmit it turned off. The battery was still flat.

So I lifted the hood, and changed the lead going to the little fuse box to the main battery instead, and radio was good. The fridge stayed off all weekend....
I have had the fridge on for two weeks at a time before with no problems, and the battery (Optima D34 yellow) is less than 6 months old.

I have a ScanGuage which I don't tend to use too often, but plugged it in and changed to the VLT setting and found it reading 12.2V while running. For the next two days, the same voltage, with an occasional spike to 13.7 and back to 12.2. When I got back home, I grabbed the meter and found the second battery to have only 5.6V charge and 12.7 in the main.

(I have a battery charger, but not yet used it.)

So after all that waffle, and as electrics aren't my area of expertise, does it sound as though something is not right there? Today when I got in the car, the VLT reading on the scanGuage was at 14.3V, but next time started, was at 13.1, and a minute ago 12.7.

Any suggestions to try to isolate the issue?

Its booked at MLR for a service next week so do I have them check the alternator also?
Could it just be a dud battery that took a few months to show up?

Thanks
Andrew

**Redback** · 26th November 2012, 02:28 PM

What's the light on the Traxide isolator doing, is it flashing??

It may be dead!!

4mm wire isn't an ideal size, you might be getting some voltage drop and maybe why the radio isn't working at 100% especially if your battery isn't getting a charge, put a volt meter on the second battery with the engine running, that should tell you if the isolator is dead or you may have wired it up wrong.

Baz.

Tombie · 26th November 2012, 02:44 PM

4mm wire is plenty for a std UHF...

For a commercial UHF not even close...

Voltages from the D4 charging system sound about right. They are all over the place as its computer controlled.

Check your wiring, connections and the Unit...

**drivesafe** · 26th November 2012, 02:53 PM

Hi Andrew and you can either phone me or I can run through the tests here.

Can you tell me if you have the SC80-LR or the USI-160?

Either way, you can begin the testing by starting your motor and see if the LED is flashing or on constant.

It should be glowing constantly with the motor running.

If it’s on constant, can you measure the voltage on the input ( the cable coming from your cranking battery ) and the output ( the cable going to your auxiliary battery ).

If the Yellow Top is still connected and the LED is on constant, we will still need to check as above.

That should get you started.

**bbyer** · 26th November 2012, 02:55 PM

Except for the two direct battery readings, the voltages you mentioned are those showing on the ScanGauge that plugs into the OBD plug. As such, my thinking is that you have an alternator problem as those voltages are what I would call the starting battery voltage and also the nominal voltage of the electrical system as seen by the OBD plug.

While rather academic, it may be that the regulator within the alternator is going or that some of the diodes within the alternator have quit. Regardless, if so, this means a new alternator. I think that the alternator still puts out some current but not enough to properly charge up one battery, let alone two, but still enough to keep the engine running.

I tend to think that the Traxide relay thing is working as intended. It will not allow the second battery to accept a charge and keeps the second battery off line until the starting battery is properly charged.

Once you do get the alternator replaced, you should charge up each battery separately on a mains battery charger to give your new alternator a fresh start.

**stray dingo** · 26th November 2012, 02:58 PM

Yes the light is flashing rapidly telling me it is off since the battery is less than 10.6v. Flicking the switch makes no difference. Voltages over the batteries remain the same whether engine is running or not.

The wire running to the fusebox shouldn't make any difference. I wasn't clear as is 4mm diameter wire (not inc shealth) with 7x101x0.12 stranding (considerably thicker than the radio's wiring). I had no issues with the radio before this weekend, or once the same wire was connected to the main battery instead

**thedrover** · 26th November 2012, 03:00 PM

The way I read it, it was ok until you installed the thermocouple fridge. They tend to use a fair bit of power, generating the heat as well as the cool. The thermocouple fridge was left running overnight, probably discharging the second battery.

Possibly the second battery is stuffed.

Recommend isolating it (take off one battery lead) and charging with a 12v battery charger. See if it gets back to 12.xx volts.

The alternator is great for general charging, it will never bring the battery to 100%.

Especially having two dissimilar batteries, a regular (4-6 weeks ideal) charging with dedicated battery charger is good.

To lessen the current drain:

Precool stuff to go in the fridge, or power the fridge via mains power (or 12v power supply) before leaving.

If you post up the current consumption and/or wattage of the fridge + battery specs, someone will be able to work out running times on battery alone

Tipsy-tap

**drivesafe** · 26th November 2012, 03:11 PM

OK folks, I’ve got some more info from Andrew and he is out in the car park testing right now.

we’ll get back to you.

**drivesafe** · 27th November 2012, 07:51 PM

Just an update.

Well Andrew has lots of patience and has had an education and after many tests, the alternator is working fine, the battery is recovering from it’s deep, DEEP discharge and the isolator is functioning exactly how it’s supposed to.

So the cause of the deeply discharged auxiliary battery remains a mystery.

We have some theories but best left that way till something definite shows up.

The only thing Andrew can do now is watch and see if the problem reoccurs!

**weeds** · 27th November 2012, 08:11 PM

A thermo fridge running 30+ hours.......pulling how many amps per hour?

I'm surprised your battery is recovering

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flat second battery

Alternator going probably.

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