Dual Battery + Camper Trailer Help

[Craggles123 Junior Member Find all posts View Profile Close Craggles123]

Hi All

We'll be heading up North mid year with the old mans camper trailer so just adding a few things to the car for it now.

I'm looking to install a second battery setup in my 2012 GX for the following:
- Run lights
- 12v plugs at rear
- Power to Anderson plug at rear

The camper trailer we have also has 2 x 100 amp batteries on board which are charged via the Anderson plug

I'm just trying to work out what I need for the setup?

I'm looking at the following
- Sidewinder / ABR Dual Battery Wiring Kit
- Sidewinder / ABR battery try
- 100 amp deep cycle battery (not confirmed which one yet)
- Anderson plug wiring kit to rear

Is this all I'll need or do I need something else to deal with the batteries on the trailer itself?

Apologies for the sketchy details, just waiting for confirmation on a few things from the old man

Cheers

Craig

[Razorback81 Advanced Member Find all posts View Profile Close Razorback81]

not sure how well it will charge having 4 batteries coming off the alternator ?

i had 3 when i had the camper
1 x start B , 1 x 105A/Hr in the rear of the 120 then another in the camper on the Anderson plug from the 2nd battery

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Perhaps a dc/dc charger in the trailer to pick up the voltage for those batteries? A lot available for a lot less $ than some of the big brands. Also one of the diodes to raise the output of the alternator.

[RBJET Member Find all posts View Profile Close RBJET]

I think you'd be fine with the gear you've listed depending on how long you plan to stay camped each time. If driving every second day you shouldn't have an issue.
Also look at a booster diode as 404pug said for a little extra voltage.

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

You may want to think about how to disconnect the camper trailer from the car batteries when you stop. If you don't isolate the camper trailer from the car batteries (especially the starter battery) then it is possible to flatten all of them. My dad's just had this happen to his car - camper trailer has a DC-DC converter in it which was happily trying to charge the camper batteries when stopped.

I'm about to add an anderson plug to the back of our car - not sure if I'll use a voltage sensitive relay (the ones used to link dual batteries together) or a normal relay hooked up to the "ignition". But there will be something!

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

camper trailer has a DC-DC converter in it which was happily trying to charge the camper batteries when stopped.

The DCDC charger should turn off when the engine is shut off?

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

The DCDC charger should turn off when the engine is shut off?

That's what we thought it should do too... but it didn't... I'll take a look in the coming weeks to work out what went wrong.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

How long was the charger running, might just be the residual surface charge on the cranker
keeping it going.

[Zygarti Lurker Find all posts View Profile Close Zygarti]

2 x 100 amp hrs in your camper is loads if you're only looking at lights and fridges (and charging phones, etc). If you want to run 240V stuff with an inverter, then it is a different story - but you go camping to get away from TVs, laptops, etc, don't you!? Or you save it for when you pull into a park for a shower.

LED light set ups use bugger all (even if you're lit up like a xmas tree), so it's really the fridge you're worried about. With that much battery power in the camper you'll should get 4 days worth safely without moving.

We did a trip up north for a couple of months with only one battery in camper, plus a portable Thumper 48 AMP hr sitting in back (plugged into anderson) which we ran the fridge from when on the move (so it kept running off that when we did short stops). I think we only resorted to solar on one or two occasions to add some charge to the camper battery.

Isn't there an issue with the second battery bay on some prado models which you should check out too?

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

If the DCDC trigger wire is connected to the main feed in then the DCDC won't switch off. My Tvan is wired like this. I presume it is to save cost and the need to run a separate trigger wire to the DCDC. So I fitted an SBi12 under the bonnet on the feed to the camper that way it cuts out at 12.7V and won't drain the main battery. From what I understand this is fairly common.

[Craggles123 Junior Member Find all posts View Profile Close Craggles123]

Hi All

Thanks for the tips so far

Have a bit more info now

The batteries on the trailer are purely to run a fridge, the old man goes away for long stints

We'll only be staying in one place longest of 5 days, most 2-3 with long trips in between

I'm going dual battery at the minute for future use, so whilst the 200amp on the trailer is heaps i want the dual batter in car for future outings

I dont see why the camper batteries would drain both on boards though, if the anderson is wired to the second battery the relay between my starter and second battery should stop that from happening shouldnt it? Only issue I thought was that the 2 trailer batteries might drain the second on board?

Electrical shit is beyond me sometimes :P

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Unplug the camper from the car for overnight stops? Wont his stop the problem?

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

The batteries on the trailer are purely to run a fridge, the old man goes away for long stints

We'll only be staying in one place longest of 5 days, most 2-3 with long trips in between

I'm going dual battery at the minute for future use, so whilst the 200amp on the trailer is heaps i want the dual batter in car for future outings

I'm not sure 200AH on the trailer is going to be enough to run the fridge for 5 days without any extra charging. Assuming you discharge to 50% (recommended so you don't kill your batteries) you have 100AH available. I'm not sure what fridge you have but it probably draws 1-2 A/hr on average over a 24hr period. If you assume best case of 1A/hr and no lighting then 5 days requires 5 x 24 AH = 120AH of capacity. If you assume 2A/hr and no lighting then you need 240AH.

One of the questions to face is how deep you are willing to discharge the batteries. If you discharge to 50% then you'll get around 500 cycles (at which point it has around 60% of the original capacity). If you discharge to 100% you'll get perhaps 250 cycles (that's what a few of the graphs I found say but I thought you killed them faster than that...).

Do you know how much power the fridge uses?

I dont see why the camper batteries would drain both on boards though, if the anderson is wired to the second battery the relay between my starter and second battery should stop that from happening shouldnt it? Only issue I thought was that the 2 trailer batteries might drain the second on board?

It depends on how you hook it all up. I've been recommended by people to put the camper trailer anderson plug on the main battery - others say to put it on the secondary. Unless you put another isolator between the camper & car batteries it may flatten whatever it is connected to. I'd suggest doing what mjrandom did - putting something like a SBI12 between the camper & car batteries so that if you forget to unplug things you don't kill the car battery it's connected to.

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

Unplug the camper from the car for overnight stops? Wont his stop the problem?

It will... as long as you remember. But if the camper has a DC-DC converter that isn't switching off properly it is possible to flatten the car battery while you're out for a stroll (it could easily suck 30A/hr out which doesn't go far on a 75AH car battery!)

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

It will... as long as you remember. But if the camper has a DC-DC converter that isn't switching off properly it is possible to flatten the car battery while you're out for a stroll (it could easily suck 30A/hr out which doesn't go far on a 75AH car battery!)

Really for the price of a SBI12, run this off starter battery to second onboard battery (or box mounted boot battery) and rear charging anderson for trailer, peace of mind that your starter will be in good shape. I put a circuit breaker on each battery so if there is a problem the appropriate one will cut off and not cause disaster.
There is no point having 3 dead batteries because you forgot to unplug or DC-DC didn't shut off properly. This is what I use after being around 12v all my life starting as car audio tech. SBI12, battery box in boot and anderson on tow. You can even run an LED indicator off the SBI12 so you can see what it is doing in the cabin plus add bridging switch to short batteries for more charge for starting if required. Run second battery in parallel with anderson off the SBI12, the boot or under bonnet 2nd battery will get more current voltage as assuming wire gauge is the same it is a shorter run with less connections (read resistance, but won't go into that here), so will essentially take priority over camper. As peter_mcc mentions, 200a/hr wouldn't be enough for 5 days straight (unless lithium batteries that take lower discharge %'s). Best to supplement with solar if you can if you dont want to add more batteries, but if doing this from scratch maybe look at Ctek D250S instead of SBI12, as has dedicated solar input as well as alternator.