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The MY14 2nd Battery and DC Thread

42K views 92 replies 21 participants last post by  riccmy 
#1 ·
This thread allows us to talk about wiring up high-current DC into the MY14 GC.
 
#2 ·
When I get my Overland CRD (its actually been allocated to a ship!), then one of the first things to do is fit a second battery. From my reading so far, it seems the options are in the wheel well - small battery - or in a separate tied down box on the floor in the back. It also seems to be highly recommended to use a DC-DC converter, partly to ensure the charging system doesn't get confused, and partly to ensure the right voltage for,say, a fridge. I have yet to determine whether a separate battery isolator is required. Any further suggestions would be greatly appreciated.
I use a DC-DC converter in my Camper Trailer, It's a CTEK D250S-dual. Works very well, though it did die just before warranty was up so it got replaced.

Most DC-DC chargers should shut-off when the input voltage drops below a certain value. This provides battery isolation and should be sufficient unless you want the threshold voltage to be higher. For the D250S-dual it is:

The charger starts charging the target battery when the supply voltage exceeds 13.1V for 5 sec (engine on).
The charger stops charging the target battery when the supply voltage drops below 12.8V for 10 sec (engine off).
Of course, my second battery, along with the D250S-dual are in the trailer(you want the DC-DC charger as close to the battery as possible) but electrically, it's the same, except my cable run is longer hence there is an even greater need for a DC-DC charger.

I did see one site talking about the D250S-dual needing a relay when used with a variable alternator. Might need to do some more research. I don't have my car yet so I have not tested it.
 
#3 ·
I use a DC-DC converter in my Camper Trailer, It's a CTEK D250S-dual. Works very well, though it did die just before warranty was up so it got replaced.

Most DC-DC chargers should shut-off when the input voltage drops below a certain value. This provides battery isolation and should be sufficient unless you want the threshold voltage to be higher. For the D250S-dual it is:



Of course, my second battery, along with the D250S-dual are in the trailer(you want the DC-DC charger as close to the battery as possible) but electrically, it's the same, except my cable run is longer hence there is an even greater need for a DC-DC charger.

I did see one site talking about the D250S-dual needing a relay when used with a variable alternator. Might need to do some more research. I don't have my car yet so I have not tested it.
I too have a camper trailer (new - haven't tried it out yet except in the paddock!), but I was thinking I'd like the option of having the fridge in the car when not towing. Or maybe even when towing. Maybe the ideal would be a self contained (battery plus DC - DC charger) battery box which could be moved from car to trailer at will. I haven't decided what to do about lights in the trailer yet, and that could determine whether the battery needs to be there. Otherwise the fridge could stay in the car.
 
#5 · (Edited)
After reading many threads on the matter I finally put together a 2nd battery system where the battery box can be removed from the car for camping or 240v charging and the cabling can be removed when not being used.

I'd look at isolators and the like, but the Ctek D250S offers full charging of AGM batteries upto 14.6v and can be used with solar panels at camp sites.

I run a 40lt Waeco fridge in the boot, that leaves just enough room for the battery box and Ctek D250S charger to sit in front of it.

There is a Britax RC-1260R 60/80A 12v relay connected to the 12v cigarette socket in front of the gearshift (this is live with ignition - the centre bin is live all the time - I've swapped the fuse to enabled constant 12v for rear cargo). 12v 30A circuit breaker attached to the side of the relay box.



What I didn't understand with this setup was the use of the relay and the diagram provided by Ctek didn't help. Looking at the diagram you're led to believe it switches between solar and alternator, thinking that if you don't have solar you don't need the relay - WRONG. Due to varying output of the Jeep's alternator, you need to use the SOLAR input on the Ctek. This will continue to charge/drain from your source even as your source voltage drops. The relay ensures you're only charging when the car is running...ahhh.


Here are the parts I used
- Repco/SuperCheap large battery box
- Ritar RA12 120SD AGM
- CTek D250S
- Britax RC-1260R relay with connector
- Anderson plugs, cabling, connectors from Jaycar



LINK

INSTALLED PHOTOS TO COME....
 
#7 ·
I installed a Projecta 150A electronic isolator trailer kit. It charges the lithium battery bank in the Kimberley camper trailer in no time without a DC-DC converter and while the fridge is running. The isolator slots in neatly next to the battery in the car.
 
#8 ·
Bob,

I can't get my isolator to supply power to my caravan battery, and to power my caravan fridge. I know the isolator is working correctly, and suspect the problem lies in the voltage drop in my wiring. The car has 6B&S and the caravan 10mm.
I measured the car supplied voltage at the caravan fridge and is showed 12.08V, which I suspect is so low that the isolator can't sense the caravan battery.
I plan to swap the caravan 10mm wiring for 4B&S cable to see if that fixes the issue.
If that fails, I will probably have to install a DC/DC charger.
 
#14 · (Edited)
You are on the right track. The cut-out voltage of my isolator is 12.8V so that wouldn't work on your setup either. The simplest way to reduce voltage drop is to double up the existing wiring. That might do it for you. Your 10mm wire sounds good but it might have more insolation than copper. The 4B&S cable that I have measures just 8.4mm accross the insolation but one knows for sure that it has 21.15mm2 of copper. 6B&S cable has 13.30mm2 of copper. The Projecta 150A trailer kit isolator comes with red and black 4B&S wire for both the car and the trailer. All told, you get 3kg of copper in the kit. I kept wiring lengths as short as possible and used crimped and soldered joints to minimise resistance. Also, the beauty of an electronic isolator is that it acts as its own circuit breaker eliminating the need for additional circuit breakers further reducing voltage drop. I also used a 175A Anderson plugs which I think you have also. The whole point was to minimise failure modes by avoiding circuit breakers, a DC-DC converter and the accompanying terminations.


The trailer is hooked up so I took some readings. With the engine idling and the fridge on, the control panel read, State of Charge 57% drawing 26A at 13.6V. The fridge takes 4.5A so the rest is going into the batteries.

Forgot to mention; best not to rely on body earth return to the battery. Firstly, it may have a higher resistance and secondly, all that current running through the body could cause electrolysis corrosion in places. Although, I note that Jeep uses body earth return from the battery to the alternator (copper isn't cheap:rolleyes:).
 
#9 ·
I'm pretty sure that you will need a dcdc converter. The variable alternator just can't be guaranteed to provide a high enough voltage. As I understand a standard alternator is only ever designed to keep a battery charged to 70-80% anyway. This is due to the limitations of fixed voltage charging. If they made the charge voltage higher, the battery would overcharge.

Bob has an unusual situation as his kk had lithium batteries. Lithium batteries always need complex electronics to charge, else they tend to explode. These electronics are probably designed to cope with lower voltages in fact they likely already have a dcdc converter built in.
 
#12 ·
Dunkit, I've been trying to work out where to run the wires from the main battery. Your pics show your wires coming straight out onto the cabin floor. Did you do anything else to run them back please.
 
#13 ·
As all of my cabling/2nd battery is removable I just ran the cable over the interior carpet, up under the rear seat, into the cargo area. My slush mat covers the cable in the rear foot well. It takes less than a minute to disconnect and remove the 1m length of 6B&S from cargo area to anderson plug near front seat and the activation lead from cigarette plug to relay box.



 
#15 · (Edited)
Hio All,

I have trolled the threads ordered my P3 which I will wire in myself but at the same time I will install the Dual Isolator and run cable to a 50amp anderson on the towbar so I dont have to pull the car apart twice.

My Crewman had a Redarc Dual Isolator which was fine and never let me down, but is there anything better ???

I am also going to install a DC to DC charger in the van, I have 2 X 180 AGM batteries already

I get the car this Wed so havent even looked at cable routes except the pictures on this forum.

So.

1) the DC to DC charger should be installed in the caravan not the car as to stop voltage drop ??
2) would I get away with a combined DC to DC charger/isolator in the car so as to reduce cost ???
3) 6BS dual cable will fit hidden from battery area to tow bar ???
4) If the car DC/DC option is a no go then what would be the recommended dual isolator..

Cheers



PS- Counting the sleeps
 
#16 ·
See the reply in red

Hio All,

I have trolled the threads ordered my P3 which I will wire in myself but at the same time I will install the Dual Isolator and run cable to a 50amp anderson on the towbar so I dont have to pull the car apart twice.

My Crewman had a Redarc Dual Isolator which was fine and never let me down, but is there anything better ???

I am also going to install a DC to DC charger in the van, I have 2 X 180 AGM batteries already

I get the car this Wed so havent even looked at cable routes except the pictures on this forum.

So.

1) the DC to DC charger should be installed in the caravan not the car as to stop voltage drop ?? Yes, and as close to the van battery as possible, or the fridge if you have one.
2) would I get away with a combined DC to DC charger/isolator in the car so as to reduce cost ??? With a DC/DC charger, you may not need a separate isolator. No point in having it in the car, as the DC charger is used to convert a weak voltage, and boost it. Therefore needs to be close to the secondary battery.
3) 6BS dual cable will fit hidden from battery area to tow bar ??? Spot on. I recommend you run it to the back of the car, and terminate it with a fuse or cutout. Then run to both the trailer plug (12pin) and Anderson plug. Get a 175Amp Anderson not a 50A.
4) If the car DC/DC option is a no go then what would be the recommended dual isolator.. Projector do a less expensive than Redarc.

Cheers



PS- Counting the sleeps
 
#19 · (Edited)
To correct some impresions, a DC-DC converter does not "stop voltage drop" as someone said. The power loss in the wiring is the same in fact a little more because of losses in the converter. The converter lifts the voltage to a usable level but it comes at the expense of current. Nevertheless, it is a way of compensating where thicker wiring can't be used. Sorry for being testicle.
 
#20 ·
This is not strictly a towing question, but does seem to be a reasonable place to pose it:
I've been searching the forum and other sites to figure out a good way to connect an auxiliary battery. Most seem to say that a dc-dc converter is the best way to go especially in the case of controlled output alternators,,as it maintains a high enough voltage for charging, and for fridges etc.
However, a disadvantage is that the charge current to the auxiliary battery is limited by the converter, to a lot lower value than if it was directly connected to the alternator when the alternator is producing at the higher level of its voltage range ( resulting in a lot more driving time to charge the auxiliary battery.)
So the question is: Is there a way (or a suitably intelligent converter) to connect the alternator,directly to the auxiliary battery when the alternator is producing a suitably high voltage, but via the converter when the voltage is reduced by the management system?
A related question: given that the alternator output is controlled by the electrical load at any given time, then if the auxiliary load (eg a fridge) was sensed by the management system, then there would be less need for a dc-dc converter to maintain a voltage high enough for the auxiliary load. Since the load must therefore be sensed somewhere after the battery, is it possible/practicable to connect the auxiliary battery and/load after the point at which the load is measured (vs directly from the main battery terminal). If so, where?
And then: are the power outlets in the JGC, especially the rear one, connected in a way that the load they supply is measured by the management system?
Thanks, Russell
You have to consider both voltage and current. I have no doubt tha: the Jeep alternator will adapt to ensure that it supplies enough current for connected loads. The issue is that it will not go to the trouble of supplying enough voltage to charge your remote battery one reason for this is that such a behavior would over-charge is own battery which 1, is connected via a lower resistance (and hence receives a higher voltage) and 2, may have been fully charged to begin with. Actually, the old, constant-voltage method of charging batteries meant that they were really never fully charged, because they needed to pick a voltage that would never over-charge (13.8v), that voltage will also never fully charge, most car batteries sit in the 70-80% charged state. Smart chargers get a around this.

I have a ctek d250s dual which works well for me. Sure it has a limited maximum charge rate. Ctek have an extra module that you can add (I think it's called smart-pass) that can pass through when there is enough voltage to charge at a higher rate but as per my comments above, I think you would be wasting your money because I don't think that this would happen very often as usually the jgc battery should be close to full charge.
 
#22 ·
A follow up question:
In the first instance, I plan to run only a fridge, and add an auxiliary battery later. would it be appropriate to install a ctec d250s up front to provide the correct voltage to the fridge, and add the batteries later?
Thanks, Russell
 
#23 ·
You should not need the ctek for just the fridge. In fact I don't know if it would work without the battery. The fridge should run down to 11.x volts which the jgc will supply. Just be sure that your cable is thick enough to supply start up current, unless you have an engel.
 
#24 ·
I reported a few months back in this thread that I had some issues with getting power to my caravan via the Anderson plug.
The plug was wired though a Projecta Isolator, and when I connected the caravan, The Isolator could not detect the battery in the van, and therefore would not supply current.
I was of the opinion that the problem was due to voltage drop in the Van wiring, as although I had 6B&S in the car to the Anderson, I only had 6mm wiring in the van from the Anderson to the battery. That 6mm run was approx. 7-8Mtrs.
To rectify, I replaced the 6mm with 10mm, heavy duty battery lead. When making the final connections, I noticed that the 6mm earth wire was in fact not connected. The van manufacturer had omitted to make the connection.
In any event, now with 10mm wiring, and now actually connected, the voltage to the van battery is good.
 
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#26 · (Edited)
Good job! It certainly wasn't going work with the earth disconnected :). When ordering my trailer, I specified an 175A Anderson plug. I made no mention of the cabling but all credit to the builder, he used battery cable for both the positive and negative and ran both into the body of the trailer. The actual size of the cable I can't tell because of the sheathing but judging by the weight and stiffness, it is definitely battery cable. Anyone considering wiring up an auxiliary battery with 6mm wire should firstly compare the cross-section of copper in it as against battery cable. It's like comparing ones finger with a piece of spaghetti. Considering an auxiliary battery has to push current two or three times as far, you might want something better than spaghetti.
 
#25 ·
Allypally,

I'd be careful in using a traditional isolator in a vehicle with a "smart" charger/alternator. Isolators work on voltage and you can't be sure that the voltage that the JGC will run the alternator is high enough to trigger it.... all of the time. Sometimes it may be, but perhaps not, if your JGC battery is fully charged when you start your engine. Perhaps your cabling re-run provided just enough to trigger but I'd want to monitor it over time to make sure that this is always the case. It's part of the reason why CTek tell you to use the "solar" input of the D250S dual, fed via a relay(triggered on ignition) instead of the "alternator" input, which basically has an in-build isolator.

To my way of thinking, isolators are basically just a relay that triggers when voltage is close to 13.8 and have some hysteresis. To me, a better solution in the JGC is to just use a relay. I have mine trigger off the wire that supplies recharge to the torch in the back as it appears to only have power when the engine is actually running, i.e. exactly what I wanted!

It all depends on whether the float charge level of the JGC is higher than the trigger for your isolator. I guess you could monitor that over time with a multimeter in the cabin connected to the lighter socket.

I might have mentioned this before, but I put the relay in the rear and broke out 3 anderson connectors:
1) In the cargo area, before the relay. This is permanent 12v in case I want to "careful" run a fridge".
2) In the cargo area, after the relay. General use.
3) At the towbar, after the relay. For the camper.

The bonus is, if I ever want permanent power at the tow bar, I can just connect the two anderson connectors in the cargo area together, bypassing the relay!
 
#27 ·
I'm trying to find a take off point for an accessories switched 12v reasonably close to the battery for an isolator - any views on the easiest approach? I don't relish taking off a lot of trim.
Thanks,
Russell
 
#32 ·
As I mentioned above, I ran mine hot to the cargo Bay with only a breaker under the seat. I put a standard automotive really in the cargo Bay that is triggered by the spotlight chargers power. This works really well for me, to my mind batter than accessories as it is only powered when the engine is actually running. It was easy to take the power of here by poping out the charger and posting a wire down towards the wheel well. Benefit is that I also have hot power in the cargo area of needed.
 
#28 ·
Hi Guys. Don't know if this has been covered or not but there seems to be space under the MY14 Jeep (I think it was used for a space saver spare in Europe) and was wondering if anyone thinks it could be possible to have additional battery/ies located there?

Has anyone done that?
 
#30 ·
Ally is right, think it was over on the Ausjeep forum, about 18 months ago in one of the dual battery threads. Didn't look all that attractive to me.
There is also the option for non QL vehicles to fit a battery under the passenger seat. Takes a bit of cutting out of plastic but has been done.
John
 
#31 ·
In the States the space is used for the urea tank. It certainly is wasted space.
 
#34 ·
Thanks Bob.
I have actually now got it wired to the rear accessory point. Taking the trim of was every bit as hard as I thought.
IT is a Thumper battery and their provided charger, which from what I can figure is an isolator based on whether the car is on or not.
So it has power input leads to the car battery, power output leads to the Thumper, and a trigger wire to the ignition or accessories power. At first sight it seems to work OK.
After our previous discussions about DC - DC converters, VSR's and the like, I was/am somewhat concerned that simply having the batteries in parallel during charging May be an issue. But after asking the question three times, and being assured that it works and there has been no problems with intelligent alternator/AGM set ups, I decided to take the easy route and use their supplied charger.
On a related issue, when connecting to the negative terminal of the battery I noticed that the clamp on the terminal was loose enough to be able to swivel it by hand. The tightening mechanism is a bit odd, but the end result is that the gap which closes when tightened is totally closed, leaving no more tightening possible. I eventually got it tight by ensuring the clamp is pushed down onto the terminal as much as possible, but it seems a bit borderline.
Has anyone else had any problems with this?
Thanks,
Russell
 
#35 ·
No issues found with my battery terminal connections. Not sure if terminals are disconnected during the sea voyage, or during pre delivery when some accessories are fitted, but if so, that could explain.
 
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