Redarc dual Battery

[philf63 Lurker Find all posts View Profile Close philf63]

Hi
i have a redarc dual battery setup i noticed that my main Battery was at 12.7V i then checked my second Battery it was at 10.8 V i turned of the ingal went for a drive about 40 minutes re measured the main battery still the same 12.7 then measured the Second battery it was upto 12.5v
is this correct charging i thought the firts battery gets charged then it charges the second battery ?

cheers Phil

i have a 07 D4D

[Llamaboy Junior Member Find all posts View Profile Close Llamaboy]

I have too have had problems with our redarc solenoid not charging the auxiliary battery. It turned out to be carbon on the solenoid when we pulled it apart. The solution was to replace the redarc solenoid, problem solved. This is our third redarc solenoid they only seem to last 2 years and we start to get the same issue of not charging the battery.

[philf63 Lurker Find all posts View Profile Close philf63]

my redarc is only about 3 months old and it is charging the second battery first

[Llamaboy Junior Member Find all posts View Profile Close Llamaboy]

Your main battery should be brought up to 12.7v first then the aux battery will be connected, just look for the red light to turn on. While still charging you should be able to measure both terminal on the redarc the voltage should be the same +13v.

The other thing to remember is if your aux battery is a deep cycle, then 40mins drive will not be enough to charge the battery as it will take several hours to fully charge. you may also be seeing the effects of what is known as the water fall effect, where both batteries will equalise once connect and not receiving an external charge.

You should not be able to charge the aux battery first the main battery should be first charged.

[leachy_9 Advanced Member Find all posts View Profile Close leachy_9]

The redarc has a design "Kick in voltage" of 13.2V and a "kick out voltage" of 12.5V. ie once your main battery voltage is above 13.2V the redarc closes putting the main and aux. batteries in parallel, charging both batteries. The Redarc will remain closed until the main battery voltage drops below 12.5V.
If your main battery was at 12.7V chances are it had been above 13.2V (causing the Redarc to close) and hadn't yet to dropped below 12.5V. So the redarc would still be closed and charging both batteries.
More checks would be needed to verify that your Redarc is working properly, though from the information you have given there is no reason to believe it is not working.

Note: If correctly installed the Redarc cannot charge the aux. battery and not the main battery. Just because you have seen a change in terminal voltage at the aux. battery and not the main battery does not mean the Redarc is faulty. The batteries were obviously at different states of charge and most probably different types of batteries, thus they will recharge at different rates.

Leachy

[philf63 Lurker Find all posts View Profile Close philf63]

cheers i will keep a close check on it

[leachy_9 Advanced Member Find all posts View Profile Close leachy_9]

If you are concerned and want to check to operation of the Redarc, you can follow the procedure below:

Run car until main battery charge is >13.2V.

Stop engine.

Check that Redarc has closed. This is indicated by a red light on the top of the Redarc – light ON equals Redarc closed.

Turn on headlights hi beam (leave engine off).

Use a multimeter to monitor main battery voltage. If the Redarc is operating correctly it should open (red light OFF) when the main battery voltage drops below 12.5V.

Once the Redarc has opened, turn off the headlights and restart the car. Note: don’t let the main battery voltage drop below 12.2V waiting for the Redarc to open as you may not be able to restart the car. If the Redarc hasn’t opened by this stage there is a problem.

With the car running monitor the main battery voltage. When the voltage reaches 13.2V the Redarc should close. If you get to this point and the Redarc has open and closed as described then it is working correctly.

Keep in mind that there may be slight differences in measured voltages and design switch point voltages due to the accuracy of the Redarc sensing circuit and your multimeter.

Leachy

[lofty Advanced Member Find all posts View Profile Close lofty]

Thanks leachy for your excellent explanation of how the redarc solenoid works.

Am i right in thinking that there is a way to bypass the solenoid and use the aux battery as a cranker?

[leachy_9 Advanced Member Find all posts View Profile Close leachy_9]

Lofty,

yes. There is a short lead on the Redarc that when connected to 12V overrides the voltage sensing and turns the Redarc on. Typically this is wired from the Aux. battery positive terminal via a pushbutton, allowing you to crank off the aux. battery when the push button is depressed.

Leachy

[Pedro Advanced Member Find all posts View Profile Close Pedro]

Not sure if this helps but there was an article in Autumn 2007 newsletter from Redarc
http://www.redarc.com.au/news/Autumn07.pdf

I had mine changed to the new one.