Traxide dual battery issue (i THINK)

[coopers1969]

Hello all
i have a dual battery set up in my Disco 4 2011. the main battery is what came with the car i have replaced the Aus battery in the last 3 months. i feel that there may be a problem with my Traxide SC80 unit. When i have both batteries hooked up together i am getting battery drain to the point that i have to start the car every second day or it wont start. The starter battery to be honest is probably not 100% but it does hold charge. the issue is this morning i went out and check the battery voltage both the starter and the aux battery read 12.54 volts and the green light on the traxide was solid, so all good. i then disconnected the traxide unit to create to separate batteries the starter battery climbed to 12.79 volts and the Aux battery went to 12.89 volts. This to me feels like the traxide unit is pulling power from both the batteries. any ideas. i would have thought with these reading the 2 batteries combined through the Traxide unit should be around the 12.79 Volts i may need to replace the traxide unit i have with another one. any other suggestions would be great.

[drivesafe]

Hi Coopers, and it actually sounds like your setup is fine.

The voltage reading you got while the SC80 was connected, is probably very close to the REAL voltage level of your batteries, and at 12.54, your batteries are at around 90% SoC.

The voltage readings you got once the SC80 was disconnected, is what is known as an OPEN CIRCUIT voltage reading and is next to useless.

This has nothing to do with you, it is just that this type of reading is used all the time but is prone to a number of errors that OPEN CIRCUIT voltage readings do not indicate and the very reason I NEVER use OPEN CIRCUIT voltage readings.

Again, everything sounds fine.

To get a much better idea of the state of your cranking battery, try turning your Ignition but do not start your motor.

Leave the ignition on for a few minutes and then measure the cranking battery voltage.

Turn your ignition off and watch the cranking battery rise again.

[Hogarthde]

Coopers, I have no exact data, however in my case I reckon now I double lock every time ,,the battery holds its charge longer.

dave

[DiscoMick]

No problem there. About 12.6 is virtually fully charged. Anything above that is a false reading.
Put the battery under load and the reading will drop to the real level.

Remember too that the two batteries are connected so there may be some current flowing between them. This is a design feature of Traxide units.
The Traxide will separate the two batteries to make sure enough charge remains in the starting battery to start the vehicle.

[Tombie]

Your primary battery is failing.

[scarry]

What Tombie said.

To check,pull the earth off the SC80,therefore the two batteries are isolated,and the SC80 is drawing no current.

Charge main battery until it is fully charged and see how it goes.
If same issues,it’s probably shagged,replace it.
Or get it tested.

Charge auxiliary overnight and get it tested,or run a fridge or another load on it and see how it goes.

This will determine condition of each battery.

I had same sort of issues with mine,the auxiliary battery was faulty,6 months later,more issues,it was the main battery.Both times one dragged down the other.

[muddy]

what is the isolation voltage of the unit ?

[Tombie]

In a D4 8 years from a primary battery is an absolute extreme run by about 3 years!

Your problem will go away once a new battery is fitted.

[coopers1969]

Your primary battery is failing.

This is what I recon as well. I may get it tested to check CCA my little eBay one says the CCA is well down from its 735CCA

[ramblingboy42]

In a D4 8 years from a primary battery is an absolute extreme run by about 3 years!

Your problem will go away once a new battery is fitted.

I wish I could get 8yrs from a battery....I got 4 from mine.

[coopers1969]

some more numbers from over the last 24 hours
as drivesafe said turn on the ignition for a couple of min to get rid of any surface charge. voltage with both batteries connected went down to 12.26 volts. at which stage the traxide isolated the the Aux battery as it should. turn off ignition within 10 mins main battery which is now isolated (traxide light flashing) 12.38 volts. Aux battery (isolated) 12.80 volts i would assume that the surface charge would also have been taken off from the ignition being on and the 2 batteries joined.
1 hour later traxide still flashing so batteries are isolated main battery voltage is 12.80 and the Aux battery voltage is 12.87 volts.
in the morning same scenario as above both batteries isolated main battery is 12.76 volts and aux battery 12.85 volts. interestingly i turned the ignition on this morning after getting a reading of 12.76 volts and after i had turned the ignition on the main start battery (still isolated) when down to 11.85 volts car wouldn't start, battery stuffed.
based on the numbers alone before i turned on the ignition i thought the main battery is fine but after turning on the ignition i now know the main need to be replaced. what surprises me is how the battery voltage recovered but the it doesn't hold the power to start the car.