Main over Aux battery power supply

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: Main over Aux battery power supply

Hi longdog and while your on the right track, there is no harm in using up to 50% of the cranking battery’s reserve capacity, but unless you have a specially programmed Redarc, the normal operation of a Redarc means it actually uses less than 10% of a cranking battery’s reserve.

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

Re: Main over Aux battery power supply

Fair call longdog, and your right, it is beneficial for me to run the car daily, if I cant keep the tikes out of the fridge, but where we camp and visit we dont usually stay put, we normally are visiting places, sight seeing etc, so it does get a charge up any way, I suppose at the moment the longest we have been away for is 4 days (believe me longer would be nice) but didn't have a problem, just out of interest if you are running the fridge and acc off the aux, and god forbid the headlights get left on during the day and the main goes flat, what back up do you run, yes I can obviously see that running part of 1 battery and more off the other will last a lot longer than 1 battery, but having that totally isolated spare battery for me is a good reassurance. Also, what is the average price of a RedArch system. Thank you for your imput, its great to hear and see both sides of the fence.

[longdog Member Find all posts View Profile Close longdog]

Re: Main over Aux battery power supply

Hi drivesafe,

You may indeed be correct on that 10% - I never really questioned what I had heard once, which I'm pretty sure was either 30% or 1/3rd of main will discharge before redarc disconnects. Now that I look at the redarc website, it mentions a 12.7V cutoff, which would be less than 10% discharge depending on current draw (and temperature I believe). From time to time I've tested the voltage of both batteries while camping, and the main generally seems to cutoff between 12.53V and 12.58V in my vehicle, so I'm probably getting only somewhere around 10-15% discharge out of the main, I'm guessing. So I certainly stand corrected.

Was interested to note on the redarc website that you can get the redarc cutoff voltage modified for a small fee but only prior to purchase - which I guess is what you meant by "specifically programmed'.

And Dippa - agreed - your setup is more failsafe than a redarc, indeed. Probably counts if you're camping remotely without other vehicles - I generally don't, and always carry a set of jumper cables, so I'm not highly concerned about that aspect.

Cheers all, ld.

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

Re: Main over Aux battery power supply

So does the Redarc (and other electronic systems for that matter) protect the Aux from fully discharging? If it does, to what level?

If it did, it would mean the Main is protected so that it draws down 10% so that if the Main went flat for other reasons [kids leaving lights on etc] the Aux would still be able to jump start the Main as it was protected to "?" V, enough to start the car.

If it just continually draws down off Aux until it is flat, I see why Dippa's system is worth considering. AT least you have a back up.

I wonder how many people with a "normal" dual battery system have ever had both batteries fail at same time. I had Dippa's type of setup in last 90 series and used it to jump start me out of problems quite a few times when the main went flat for "out of the normal" reasons. My batteries were Main >4 years and Aux >5 years old each when I sold the car. With that type of system though, I would be worried if I had two dissimilar batteries as they are charging at the same time and one of them may not ever charge to its maximum [from what i have been told] - cheers....

[longdog Member Find all posts View Profile Close longdog]

Re: Main over Aux battery power supply

No, the RedArc doesn't protect the aux in any way. It will let you completely flatten it. My Waeco fridge does have an auto-cutoff to protect the aux battery, and I can change the voltage level (lo-mid-hi) at which the fridge will cut off. If you are running the fridge off the starting battery, you should set the fridge to "hi", otherwise you can set it to "lo" if running of an aux battery (according to the fridge manual). So another method of making sure the aux battery can still help start the car is to set the fridge to "hi" (or "med" might work) - but you would be reducing your fridge run-time available. If you are running additional devices other than the fridge then you are back to zero protection.

Not sure what you mean by the charging issue - the RedArc also charges both batteries in parallel (although it charges the starting battery first until it reaches 13.2V, then it charges both in parallel). There isn't any problem with charging dissimilar batteries in parallel that I am aware of - there may be a problem if you are charging with a 3-stage intelligent charger, but as far as I know the Prado charging system is pretty much constant voltage charging (although it does reduce the voltage slightly after 15 mins or thereabouts) - I could be wrong about that, I'm no expert.

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

Re: Main over Aux battery power supply

Well thanks to all who had input to this thread, its great to throw ideas around get various opinions.
I will let you know if this system pops up any issues, or if any unexpected benefits are found.

There are certain benefits for both systems so anyone wanting a couple of different systems can get some more info.

[bdaearth Member Find all posts View Profile Close bdaearth]

Re: Main over Aux battery power supply

hey Dippa

One thing I would like to know about the setup you are running is how it would handle a full time fridge in the back as my engel lives in there and is always on.


Brenden

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

Re: Main over Aux battery power supply

Hi Brenden, I have an 80ltr Weaco that practically lives in the back, generally I will be driving every day at some time or even every second day. I have never had the fridge stop on me, that would be the end of it if I had warm beer.
Haven't had an issue so far.
The Weaco has 3 power options so I just put it on the lowest voltage cut out and no issues.

I think it totally comes down to ambient temp, how often your in the fridge and how long between runs. Have a good N70ZZ main and a 550 to 650cca Aux battery and you wont have an issue.

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

Re: Main over Aux battery power supply

HI Dippa

these are photos of the same setup i had when i had a 90 series prado. Looking at doing same in the 120 if i get enough time to start on it [thanks for the sketch you sent me. i could read or work out most of it, but i may give you a call when i get closer to doing mine again]





cheers mick

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

Re: Main over Aux battery power supply

Man the 90's had a full engine bay, please feel free to call if anything not clear, after Brenden message am seeing how long I can leave the fridge on for, so far4 hrs., get back to ya

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

Re: Main over Aux battery power supply

42 hrs and we had to go out, the fridge was still running and car started no issues, that was with an outside ambient temp during the day of about the 27deg mark, so probably around the high 50s in the car, windows up.

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

Re: Main over Aux battery power supply

bdaearth - if the engel is always on in the back, and if you use your car often it will be fine. It will go even better from a decent charge when you go on a good long run. I had a switch on my dash with this setup so I could manually turn aux to charge or not charge and also another switch for a 12 volt monitor connected to both batteries which helped me keep up to when it needed a long charge. I found it benefited from a good long drive rather than the short stop/start type.

I run my waeco in the back connected via a waeco raps unit. that way it just stays on and i dont have to worry about when to turn it off. the raps has thicker cable and also 2 plug in fittings. the standard cig type or the hella fitting that i use by sliding the red tip off the waeco lead plug, that way it locks on secure. you have 2 choices for power cut off - with engine on/off or low voltage. engel have a similar product to the waeco raps if you look for it - i seen them in repco last year. they are so simple to fit and can be easily moved to another car as a complete kit when you sell like i have done. If you only have the starter battery it can be connected to that, and when/if you get an aux batt just relocate it to that one if you want to, cheers....

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

Re: Main over Aux battery power supply

Just a qulick up date, I was noticing that my main battery was not lasting as long as normal, less than 24 hours and flat, what I have noticed is the batterys are not charging enough even after a 3 hour drive.
I have just invested in one of those voltage boosters so will see how that helps.
The rest of the system is still working a treat.
Will let you know what difference the voltage booster makes.

[bdaearth Member Find all posts View Profile Close bdaearth]

Re: Main over Aux battery power supply

42 hrs and we had to go out, the fridge was still running and car started no issues, that was with an outside ambient temp during the day of about the 27deg mark, so probably around the high 50s in the car, windows up.

Dippa it all seems to be going well for you then? I have a 32lt Engel that has lived in the back for close to 6 months and have never missed a beat. I give it a good flogging with hot cartons of beer going straight in and also a lot of freezer use. Like you my prado is often parked in the full sun with the windows up (I am in the earthworks game) I don't have a monitor and have only put a multi meter on it once and can't remember what it was reading ops: but do remember them both being very close.

If this type of setup does work well like you say there are a lot of people out there that could save a few bucks or put it to something else 8)

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

Re: Main over Aux battery power supply

Just fitted the new voltage booster, went from 13.6v to 14.2v when cold, hopefully both battery's get a good charge now. Going away for a couple of weeks through the south west should be a good test. Stay tuned.