Jeep Grand Cherokee - Battery isolator lessons

[Macropod]

Hi all, Just a quick post for those putting in a Redarc battery isolator in their New Jeep Grand Cherokee - beware !

Having just bought our new 20.63.1 OB I had a Redarc battery isolator fitted to the jeep by a reputable auto electrician recommended by the Jayco dealer. The intention was for the isolator to disconnect the van from the battery when the volts fall below 12.7 volts (so when the motor is off) and reconnect the van to the battery when the volts go above 13.2 volts (when the car is running) - pretty standard stuff really. BUT....Jeeps don't play by the same rules as most other cars and the smarts in the jeep doesn't necessarily pump 13.2 volts to the battery when running - it varies the charging volts depending upon what is required.

SO...when we picked up the van the jeep felt that it would charge over 13.2 volts so all was well - the ESC light indicated it was OK, the fridge automatically switched to 12 volt supply - all was nirvana. BUT...the next time we went to tow - no esc/no fridge. So after some research - found out about the Jeeps battery charging "smarts" and disconnected the ESC from the Redarc and went straight to the battery. Not too worried about the fridge at this stage - but its pot luck if the Redarc will activate. You can override the Redarc using an override switch - which is on the cards for me.

SO... if you have a van with ESC, and tow with a Jeep Grand Cherokee, and have a Redarc battery isolator fitted, and your ESC is on the switched side of the Redarc......chances are you wont have the ESC when you need it, and your ice cream will have melted !

Happy for someone with more grey matter to correct me on any of the above as its always fun to learn !

 

[Antman]

Hey @Macropod i think you might be talking about most of the new cars that now have the smart alternators that actually limit the voltage output under acceleration?? Not sure though? Anyway, i have a new Pajero MY14 VRX model. The alternator on these cut the voltage down under acceleration. Mine goes down anywhere to 12.1voltes. So essentially if you install a standard isolator, you get the issue you have mentioned above where as the alternator will not charge you secondary battery - in your care your van battery.

The solution is basically to install a DCDC charging setup rather than a standard isolator. Redarc and CTEK both put out units that will do this all but pricey.

The other way them i have read you can "Trick" the cars alternator is to run around with your headlights on. This will cause your alternator to push out full charge.

So the question begs, Why do the new alternators do this? The reason is to do with emissions control apparently.

Anyway, if this is basically your issue and you want to know more, let me know.
Cheers mate
Ants

 

[Macropod]

Hi Antman. I would be keen to know more about the DCDC charging setup - not sure running around with headlights on is going to work for me. Any info you can pass on would be greatly appreciated.

 

[DaveS]

check this mob just got this in the e-mail yesterday, not a bad price for a dc2dc charger
http://www.australiandirect.com.au/buy/matson-20amp-dc-to-dc-charger/MA20DC

 

[twscoot]

The other option which I have adopted successfully after taking delivery of one of the first MY2014 JGC (and writing about this on other forums) to use an isolator with a variable disconnect.
This Jaycar product works well for me. Cut-in and cut-out voltages are independently adjustable with 10 set-points each.
Mine is set to 'release' the voltage at 13 volts rather than 13.2v. This means there is always voltage available for the fridge. Of course a (more expensive) DCDC charger will do a better job at charging your battery if that is your main concern.

Details here: (edit 1/8/2016 the link takes you to a 24 volt unit. The one I have is of course a 12 volt one). http://www.jaycar.com.au/productView.asp?ID=MB3682
Cheers
Andrew

 

[Antman]

Hey mate,

We have the CTEK D250S purchased from the linked ebay seller. This unit also allows a solar setup as it has the regulator built in.
Ours will be up and operational within about a week or so, Just have to get it to an auto sparky to install the relay into the start wiring (somthing I didn't want to do myself). The CTEK will allow a battery bank of up to 300AH (amp hours) so we have it setup to run the 2nd battary in the car and then I have heavy guage wiring running down the car to my anderson plug to my van battery. Where you have to be careful in this setup is matching your batteries in size. Reason being, if you have a bank of 2 batteries, 1 being say 60ah and one being 100ah, the 60ah battery will get overcharged (limiting its life time) and the 100ah will always be undercharged - i don't know if undercharging will cause any issues except less running time and a higher risk of draining your battery and damaging it that way? The CTEK unit actually takes the voltage input and increases it to the requirement of what it is charging. It is a 5 stage charged. I would suggest to do some reading on how it works as im certainly not qualified to explain it.

The matson one above that @DaveS posted is a little bit cheaper but i don't believe it has the solar capabilities nor i don't think it charges in the same way as the CTEK but not sure on this?

The red arc equivalent is more expensive but has a higher temperature threshold before it starts to scale back the charging.

Hope that helps, I spent hours trying to figure this out and come to the most cost effective solution to my problem whilst staying with quality gear.

Cheers
ants

 

[Macropod]

Hi Twscoot and thanks for your advice. I am keen to look at the Jaycar unit in more detail. Where did you mount this unit in the Jeep. Not much room in the battery well under the seat.

Cheers..John

 

[brotys]

Hi all, Just a quick post for those putting in a Redarc battery isolator in their New Jeep Grand Cherokee - beware !

Having just bought our new 20.63.1 OB I had a Redarc battery isolator fitted to the jeep by a reputable auto electrician recommended by the Jayco dealer. The intention was for the isolator to disconnect the van from the battery when the volts fall below 12.7 volts (so when the motor is off) and reconnect the van to the battery when the volts go above 13.2 volts (when the car is running) - pretty standard stuff really. BUT....Jeeps don't play by the same rules as most other cars and the smarts in the jeep doesn't necessarily pump 13.2 volts to the battery when running - it varies the charging volts depending upon what is required.

SO...when we picked up the van the jeep felt that it would charge over 13.2 volts so all was well - the ESC light indicated it was OK, the fridge automatically switched to 12 volt supply - all was nirvana. BUT...the next time we went to tow - no esc/no fridge. So after some research - found out about the Jeeps battery charging "smarts" and disconnected the ESC from the Redarc and went straight to the battery. Not too worried about the fridge at this stage - but its pot luck if the Redarc will activate. You can override the Redarc using an override switch - which is on the cards for me.

SO... if you have a van with ESC, and tow with a Jeep Grand Cherokee, and have a Redarc battery isolator fitted, and your ESC is on the switched side of the Redarc......chances are you wont have the ESC when you need it, and your ice cream will have melted !

Happy for someone with more grey matter to correct me on any of the above as its always fun to learn !

Howdy mate i am fitting redarc isolators every day to new cars i do have problems with the new ford rangers but you can take it to ford and they can turn something over in computor of charging . i have fitted a few redarc units to the new jeeps with no problems and have even fitted dual battery set ups to these cars not sure if you take car to jeep if they can plug in to it as well

 

[twscoot]

Hi Twscoot and thanks for your advice. I am keen to look at the Jaycar unit in more detail. Where did you mount this unit in the Jeep. Not much room in the battery well under the seat.

Cheers..John

Hi John.
It is mounted on the floor in the battery well under the seat. Tight fit but it works. Just!
Cheers
Andrew
(ps the link to the unit I posted is the 24v unit. Obviously mine is the 12v one - same size though).

 

[TTBRIDGE]

@Macropod , As @Antman has said most moden day cars have this voltage issue. The current Landcruiser also has the issue. I cannot speak for jeep, but i know there is an easy fix on the market for most.

If you search "Alternator Voltage Booster" on ebay a little fuse looking thing will come up. These are designed to go in the Alternator fuse slot in the main fuse box under the bonnet. From my understanding they are essentually a diode that tricks the circut, resulting in a constant voltage boost.

I had one on my LC100 as it used to drop and it worked well, i have fitted the same unit to the LC200 but yet to actually test the result. I am running the old school style solinoid isolator from ABR Sidewinder and it seems to be liked all the time so far. I prefur the old style over the DCDC as you are not limiting the charge to your van to 20 amps as the CTEK does. The simple diode has been spoken about at length on the LCOOL forum site and many report of it working.

However, if you want to link solar into your car, then the CTEK DCDC is probally the best option.

Not sure if one of these units is offered for Jeep, but i know the Mitsubiti, Colorado, Prado, LC, Nissan are available. Might be an easy fix for you.

Good Luck,
Tim

 

[DaveS]

I've seen these of fleabay as well, but was a bit wary. i assume they have a diode or such so the alternator can't "see" the battery volts so assumes it's low and pumps out max. but for a diode to work they use a bit of power (usually about .6volt) so you won't get full volts going out even if the alternator thinks it's pumping it out, and then does it turn into unregulated charging due to no feedback from the battery?
and if it is dummying the alternator to run flat out, then it has to use energy to do this, that energy will be dispersed as heat and something the size of a fuse can't waste that heat easy without a heatsink

i could be 100% wrong but it doesn't sound right as a cure, maybe i need to buy one and see whats in it and is it still a fuse anyway?

 

[twscoot]

Hi Tim.
I've heard you can do this on a Jeep and my local battery world showed me the fuse with the diode across it after I arrived at my current solution. But I declined the offer. Too many electrics on the car and for the 5% of them time I am towing I figured it wasn't worth it.
Cheers
Andrew