my aux. 12 volt plan

[Flyinbronco]

I am preparing for a week long trip to Cabo San Lucas Mexico this April and I'm planning on buying an ARB 64 qt. 12 volt fridge for the trip. I want to add an aux 12 volt battery to power the fridge independent of the trucks batteries. I have enough space alongside my drawer system in the bed to mount a 125 amp hour agm battery. To charge the aux. battery I'm leaning towards the Redarc BCDC1225 12 volt DC to 12 volt DC charger. The aux. battery will also power an ARB dual air compressor for the on-board air system and I'm leaning towards a Xantrex prosine 1800 watt inverter for 110 ac power.

This stuff is all way over my head but through my research I think this should be a good system for me. I'd appreciate any input from those with experience with these systems.

 

[DiploStrat]

Out of curiosity, why do you think you need a secondary regulator, especially one not sold in the US? If you must use a B2B, consider the CTEK D250S, which is readily available in the US. But there is very little reason to use these beasts if your alternator charges at 14v or above, as most modern vehicles do.

A 125 Ah battery is, as these things go, tiny. Why not simply install a Blue Sea ACR, sized to your alternator, and be done? Simpler and much less expensive. And it has the advantage of much higher ampacity.

And, if that is too expensive, read this thread: http://www.expeditionportal.com/for...ke-a-cheap-isolated-dual-battery-setup-for-50

 

[jonyjoe101]

Thats alot of money to spend for a mppt controller. Unless you have a massive panel on your vehicule (200 watts or larger) you wont get a big improvement over a many times cheaper pwm controller. 25 amps is alot of power thats equivalent to 2 x 250 watt solar panels at midday. That kind of solar will easily keep a 125 ah very happy.

The 12 volt danfoss compressor fridges are very thrifty in the power use if you keep them at 40 degrees (my edgestar fp430 used a total of 26 amps in a 24 hour period). I had a 20 dollar pwm solar controller, 120 watt panel, and 75 ah battery maintain that nonstop 24/7 for months at a time. Your air compressor while power hungry probably will be used on rare occasions. The inverter would be consider too large for your battery but as long as you only use it occasionally and turn it off between uses it should be ok, the problem with the large inverters they use power even when in standby.

If you have a very small solar panel and want to augment the charging to your house battery than your best bet is to get a "smart isolator" what it does it connects in the engine compartment and one wire goes to start battery and another to your house battery. What it does is when the battery voltage on your start battery shows its full (it smart circuitry monitors the voltage), the isolator will allow current to flow to your house battery topping it off. When you shutoff the engine it disconnects from the house battery to isolates them, so you dont drain the start battery. the reason its consider smart is because it monitors battery voltage and only allows the aux battery to be charged when the starting battery has reached full charge which is its priority. They are also much easier to install.

One thing about me I know about solar panels and both pwm and mppt controllers. why I mean that mppt doesnt improve output is from my own expierence. I own both small and large panels and both pwm and mppt controllers and tried them both to check performance.

example a
120 watt panel pwm = 7 amps output
120 watt panel mppt = 6 amps output

example b
240 watt panel pwm = 6 amps output
240 watt panel mppt = 12 amps output

Most solar charge requlators are pretty good at not mistreating your batteries, they all can charge agm's which are pretty rugged batteries as far as charging them. The Redarc BCDC1225 seems to do what the all controllers do but also does isolator duty but you pay a very high premium.

To me it would be preferable to have a seperate isolator and a seperate charge controller, that way if one fails, at least you have the other.

 

[dwh]

Thats alot of money to spend for a mppt controller.

Yea it is.

But, it's not *just* an MPPT controller. It's an MPPT controller that can charge from *either* solar or vehicle chassis electrical bus, which is sort of a neat trick.

Wired to draw from the vehicle bus, it's a 25a DC-DC charger. It draws power from the vehicle's electrical system (battery and alternator), steps it up as need be, and does a 3 stage charge on the aux battery - bulk to 14.5v (gel/agm) or 14.9v (fla), absorb at the same voltage until amps drops below 4a for 30 seconds, and then float at 13.3v.

Unfortunately, from looking at the manual, it can't do *both* at the same time. You can rig it with a relay so that when ignition is off, it's in solar charge controller mode, and when the ignition is on, it applies power to the "source select" wire, which causes it to go into DC-DC charger mode.

But not being able to do both at the same time is not a deal-breaker in my book. If the engine is running, you don't really need solar at the same time if the solar is small. For a large array, I'd want both at the same time.


I have to agree with Diplo on this one. The CTEK 250s is half the price to do the same job. It's also a multi-stage DC-DC charger - only 20a as opposed to the Redarc's 25a but I think that's not enough of a difference to squawk over, and it also has an MPPT solar charge controller in it. Plus the CTEK is fully marine rated and waterproof. And doesn't require any special wiring relay setup to switch between DC-DC and solar modes.

 

[dwh]

Oh, and the Redarc can also do 24v on the input side to 12v on the output side. So for a truck with 24v chassis wiring, the Redarc would win out over the CTEK.

 

[con kso]

Mr. Bronco,

I'm the least knowledgeable about the technical side of this stuff, but I can tell you that you can do the Cabo trip with a much more basic set up then you are proposing.

I know because I just did it.

We spent 21 days living out of our Callen camper mounted on my Tundra 4x4- I surfed all over southern Baja, had a great time, blasted my truck's stereo all day long, ran my 52L ARB at -13 and never depleted my battery's starting capacity. I brought a AntiGravity lithium jump pack with me- never needed (which was good because it was non-functioning when I checked it a week into the trip).

For charging my laptop/camera battery/iphone we used a simple inverter made by duracell that plugs into the cigarette lighter- my girl bought it at Costco and I didn't think it would work but it charged our stuff just fine. We only used it when the vehicle was running but for about twenty bucks it was great.

I installed a 100 amp/hour battery into my truck and ran a 10 guage wire from it back into the camper to power the ARB. For some reason, the ARB would not function properly off the power provided by the cig lighter in the cab of the truck so having a dedicated, fused, circuit to power the ARB was key.

I charged the battery whenever I could by deploying our 120 amp solar panel (made by ZAMP) - it juiced everything up just fine. I really liked it because I could move it around easily in the sun.

You can see pics and read a little bit about our trip here: http://www.expeditionportal.com/for...ttery-solution-or-good-thing-I-have-AAA/page4 and if you want to read about the whole trip check out www.paddlesurf.net where I'm writing the trip up chapter by chapter.

Good luck!

 

[dstock]

I am considering the CTEK 250s as well. Despite modern vehicles putting out 14.0 volts or better, some of us are finding the output is variable, despite what the gauge reads and they are not able to fully charge the aux battery, in my case a Diehard Platinum AGM. I have the National Luna system which is doing it's job of engaging and disengaging but does not do any conditioning, or boosting of the charge level which seems to be what the AGM batteries require to stay healthy over longer periods of time. What I believe is happening in my system is once the aux battery isn't getting fully charged, it starts dragging down the main battery and then they are both in poor shape.
Basically, what I am getting at is you are probably better off going with a DC to DC charger for your system, like the Ctek 250S dual, and then you will probably still need an additional external charger to maintain the batteries over time.
There are smarter heads than mine in this thread but thought I would share my current experiences.

 

[DiploStrat]

Really Guessing Here

dstock,

If you have a 2013 vehicle, as I do, I would almost be willing to bet money that your starter battery is some form of AGM. If your camper battery is not getting a proper charge, I would check first:

-- The gauge of wire between you starter battery and your camper battery. Assuming that both are under the hood, it should be at least as large as the factory wiring between the starter battery and the alternator.

-- Proper functioning of your relay. There have been enough threads here about problems with the National Luna relay to double check it.

-- Charge time. The most likely problem, more important than the exact voltage or wire gauge, is simply that you are not driving long enough to fully recharge your camper battery. Remember, maddeningly enough, the higher battery's state of charge, the longer it will take to complete the process.

If charge time is the issue, as I suspect it is, the a B2B won't help that much. More important would be installation of a solar kit or proper shore power charger.

Before you spend a lot of money on a B2B, read this: http://www.smartgauge.co.uk/facts.html

N.B. I paid hundreds of dollars to install and then dismount an A2B, ending up with an intelligent relay system.

If you must use a B2B, Sterling make a 50A model: http://www.sterling-power-usa.com/SterlingPower12volt-12volt45ampbatterytobatterycharger.aspx (Friend of mine uses a pair of these on his Unimog, which really does have a low voltage alternator.) (May be available from Defender Marine for a much better price.)

As always, YMMV.

 

[Flyinbronco]

Thanks for the replies everyone. I guess I still have some thinking to do. The reason I was thinking of the 12 vt. DC to 12 vt. DC charger was to keep the agm battery happy with the stepped up charge, float etc. Using the Redarc model may be a problem as I have yet to hear back from them after I sent them an e mail. I'll check out the CTEK stuff. I'm really not as worried about saving a few bucks as I am in having a reliable system and I liked the Redarc unit. A wise man once told be to "Buy the best first and only cry once." We'll be driving the truck 8-10 hours a day so the aux battery should have no problem getting a good charge through the day enough to keep the fridge happy at night.

 

[dwh]

There are a few people around here that use the CTEK - from what I gather, they are generally happy with it. One thing is, they pretty much all say, "it's a lot bigger than it looks in the pictures."

 

[dstock]

dstock,

If you have a 2013 vehicle, as I do, I would almost be willing to bet money that your starter battery is some form of AGM. If your camper battery is not getting a proper charge, I would check first:

-- The gauge of wire between you starter battery and your camper battery. Assuming that both are under the hood, it should be at least as large as the factory wiring between the starter battery and the alternator.

-- Proper functioning of your relay. There have been enough threads here about problems with the National Luna relay to double check it.

-- Charge time. The most likely problem, more important than the exact voltage or wire gauge, is simply that you are not driving long enough to fully recharge your camper battery. Remember, maddeningly enough, the higher battery's state of charge, the longer it will take to complete the process.

If charge time is the issue, as I suspect it is, the a B2B won't help that much. More important would be installation of a solar kit or proper shore power charger.

Before you spend a lot of money on a B2B, read this: http://www.smartgauge.co.uk/facts.html

N.B. I paid hundreds of dollars to install and then dismount an A2B, ending up with an intelligent relay system.

If you must use a B2B, Sterling make a 50A model: http://www.sterling-power-usa.com/SterlingPower12volt-12volt45ampbatterytobatterycharger.aspx (Friend of mine uses a pair of these on his Unimog, which really does have a low voltage alternator.) (May be available from Defender Marine for a much better price.)

As always, YMMV.

Some background here....and I don't want to Hijack the OP's thread although hopefully he will find this useful.

No camper involved here, it's a dual battery system, side by side in my 2013 Jeep Wrangler, which is a daily driver featuring an hour commute each way, each day. Wiring is as large or larger then factory. Batteries are Diehard Platinums.

Well aware of the NL issues, started one of those threads myself http://www.expeditionportal.com/forum/threads/135771-National-Luna-Split-Charge-System-Charging-Issues All components have been replaced by NL.

I have a solar setup for when we are camped that now has upgraded wiring and solar charger controller but of course won't help me day to day.

Having to do the recovery cycle to get my batteries back up to snuff, started with aux and then will swap out for main and do that one as well.

So what did you end up using for an intelligent relay?

 

[DiploStrat]

We'll be driving the truck 8-10 hours a day so the aux battery should have no problem getting a good charge through the day enough to keep the fridge happy at night.

CTEK certainly has a better reputation in the US, if only because they offer service after sales. And, as noted, the CTEK offers the advantage of an integrated intelligent relay, which is what you really need for a fast charge.

But if you are driving that long, with a battery that small, you certainly don't need a B2B. I have a 600Ah battery bank, routinely use 150Ah overnight, and I have never found a need for a B2B.

Good luck!

 

[dstock]

There are a few people around here that use the CTEK - from what I gather, they are generally happy with it. One thing is, they pretty much all say, "it's a lot bigger than it looks in the pictures."

Haha! Yes, this is one of those items I will be purchasing locally if I go this route, 1) to see if it will fit in the space I have available, and 2)local support, just in case something...ahem..goes wrong.

 

[teotwaki]

another vote for the 250S Dual

I've had mine in for a while and it has been very reliable. As pointed out, the voltage out of the alternator will vary quite a bit depending on engine RPMs and how the OEM designed the circuitry. It is not likely to provide a dependable charge regime to a secondary deep cycle battery if the engine is not run enough hours to put the amp-hours back into the deep cycle battery. The alternator is optimized for recharging a single starting battery. As DWH pointed out the 250S also has a good solar charge controller included and is a multi-stage charger.

Why an 1800 watt inverter? Hopefully not for running a hair dryer! I've never needed more than a 300 watt inverter.

 

[DiploStrat]

So what did you end up using for an intelligent relay?

Blue Sea ACR. https://www.bluesea.com/products/76...rging_Relay_with_Manual_Control_-_12V_DC_500A

E-Mail me and I can walk you though the whole saga. In the meantime, I really recommend that you chat with docmaas about his CTEK install.