Redarc 1225D - do I still need a battery isolator

[NPS]

... and what do you guys do to protect the AUX
battery from getting flat? My old engel fridge has no
low voltage switch off.
Do. we have better alternatives?

cheers

[2bad4u]

No, the DC-DC acts as an isolator. But since you have a Gen 3 which doesn't have a "smart" alternator, why not save yourself money and just run an isolator? No real benefit from running a DC-DC.

[Nab]

You can get low voltage cutouts from Jaycar and the like. I don’t like them on fridges as personally I would rather my fridge kept running and food stay good than try and save a battery. Note my Engel has run fine at 11.1V, most battery low voltage cut outs are set around ~11.7V.

My 2014 Ranger has a “smart” alternator but I still only run a voltage sensing solenoid, no dramas in the last 6 months, in saying that I ran appropriately sized cable to my 2nd battery at the rear of the car.

[Ky1e]

No, the DC-DC acts as an isolator. But since you have a Gen 3 which doesn't have a "smart" alternator, why not save yourself money and just run an isolator? No real benefit from running a DC-DC.

A dc-dc charger is definitely not a waste of money. It will ensure your battery is charged to it's maximum, not overcharged, not over-discharged. Hardly a waste of money with an older non-smart-alternator vehicle.

[Rich0]

I completely agree. I've just upgraded from a redarc low voltage disconnect to the projecta IDC.

It's dramatically improved the life I can get out of the battery. Coupled with a 120w solar panel I was very impressed how well it worked keeping my fridge running

DC-DC chargers are the way to go.

For protection, make sure you've got all positive leads fused

[Aspey]

No doubt not all DC-DC chargers are created equal. Hopefully some battery experts chime in but with my basic understanding I thought that if you have a traditional alternator (>13.8v like most NM-NP's) then a DC-DC charger may not be necessary and might even be a waste of money, (but hey, if it's works for you then awesome).
So unless you have a smart alternator (and even then maybe not), or the Aux Battery is mounted at a distance that you need to compensate for voltage drop or your mixing certain battery technologies it could take you hours longer using a DC-DC to charge your AUX (and you might not fully charge your Aux given the time) over the basic alternators output. (eg:1225D at 25amps vs 120amp alternator).
I top up with a 240v multi stage CTEK charger every month or so which will hopefully extend the life of the batteries.

[Ian H]

it could take you hours longer using a DC-DC to charge your AUX (and you might not fully charge your Aux given the time) over the basic alternators output. .

Can you elaborate on that as to why ?

[nj swb]

Can you elaborate on that as to why ?

If the installation is done well, the alternator may be able to supply well over 20 / 25A to the second battery. So, while the DC-DC is in its current-limited "bulk" phase the alternator is pumping more charge into the battery.

The other side to that is the situation where the alternator has decided the starting battery is full, and dialled its output back to a float charge, where the DC-DC can still be charging at its max current and/or voltage, depending on the state of charge of the aux battery.

Swings and roundabouts.

[Ian H]

The other side to that is the situation where the alternator has decided the starting battery is full, and dialled its output back to a float charge, where the DC-DC can still be charging at its max current and/or voltage, depending on the state of charge of the aux battery.

Thanks. That's the reason I thought having a charger was preferable.

[Aspey]

If the installation is done well, the alternator may be able to supply well over 20 / 25A to the second battery. So, while the DC-DC is in its current-limited "bulk" phase the alternator is pumping more charge into the battery.

The other side to that is the situation where the alternator has decided the starting battery is full, and dialled its output back to a float charge, where the DC-DC can still be charging at its max current and/or voltage, depending on the state of charge of the aux battery.

Swings and roundabouts.

Thanks NJ SWB, just on your second paragraph are we still talking about NM-NP models will their basic alternator?

[Sparky3975]

Hi,

If you have upgraded to a BCDC from a battery isolator, keep it and use it as a battery link relay. I used the redarc wiring diagram to setup a battery link as well as my BCDC. I have a spare laser cut bracket for the Redarc 1225D if interested (mounts behind the passenger side headlight). The alternator in the NP's (not sure about the NM) are a temperature compensated alternator, but even the 1225D will cut the voltage if too hot.