Alternator power and battery set up in camper

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

Several weeks ago while on a trip, both the battery in my camper and the auxiliary battery in the Prado died after stopping and leaving the 3 way fridge on 12v for about 6 hours while my batteries were on their last legs anyway (resulting from being away for a week without 240v charge to top up).

This prompted me to consider an upgrade to a new battery system in both the Prado and the camper van. I thought a set up including 2 Fullriver 105AGMs in the van charged by a BCDC 1240 together with a BCDC 1225 in the prado (instead of the current SBI12 simple isolation system currently in use) would work well.

The number of opinions I have had about this proposal has left me more confused than before.

Some Auto Electricians have said that my Prado alternator will die very quickly with this proposed set up as the alternator wont have the power to chuck out an extra 65 amps (40 for the BCDC in the van and 25 for the bcdc in the car).

Others have said just put a 1240 in the car and upgrade the cabling to the tow vehicle while others have said a 1240 in the car will cook the auxiliary battery in the vehicle for charging it too fast.

The most common recommendation after speaking to a bunch of auto electrician has been to install a BCDC 1225 in the tow vehicle with upgraded cabling.

Why I am confused is that I would not think the BCDC 1225 in the Prado could can handle charging 300ah of battery (2 x 105 AGMs in the van + a 90ah lead acid in the vehicle). Further, I thought you couldn't charge different types of batteries using a BCDC charger.

Any advice or recommended installation setups would be greatly appreciated.

Thanks

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

I have a similar requirement. Two 105AH AGM batteries in the camper charged by a BCDC1240. A single 120 AH AGM battery as auxiliary in the back of the 150. This is charged by a BCDC1225 off the main battery through a manual circuit breaker. Power to the camper will be direct from the battery through a manual circuit breaker and an SBi12 and have no connection to the vehicle battery. I will / do make sure all three batteries are 100% before heading camping and I use two separate solar panels to top up each system when the engine is off. I haven't fitted up the SBi12 yet though I have the circuit breaker, SBi12 and cable ready to go. Time poor and laziness. The rest however is complete.

The reason for the SBi12 is that the sensing wire in the camper BCDC40 is connected to the input cable and thus will charge when there is voltage present. This would flatten my main battery because there is no cut out at low voltage. The SBi12 will address that.

Whether the alternator has an issue or not I guess I will find out but there are a number of people who have done this without problems.

You could use your existing SBi12 and do similar. There will be another 800 pages of why not to use a BCDC to follow...

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The reason for the SBi12 is that the sensing wire in the camper BCDC40 is connected to the input cable and thus will charge when there is voltage present. This would flatten my main battery because there is no cut out at low voltage. The SBi12 will address that.

The user manual says this

Q: If I use the BCDC to charge my auxiliary battery do I still need to install a battery isolator?
A: The BCDC incorporates the functionality of a battery isolator, it will turn ON and start charging when it senses that the vehicle has started and similarly it will turn OFF when the vehicle is turned OFF.

Is yours not working as intended?

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

Andrew mine is set up with a changeover relay which requires a trigger wire to accessories to switch the BCDC from one infeed to another. The sensing wire that should be connected to accessories is actually just connected to the battery infeed. I confirmed this by connecting directly to a 12V battery and the BCDC started charging. The battery was less than 12.7V. I then checked with Track who said that is what they do. Hence the need for a voltage sensing device between the two. Otherwise I would just run the manual circuit breaker out the back to an Anderson plug. Saves running the sensor wire forwards to another connector. I guess I could replace the 7 pin plug with a 12 and have a dedicated accessories trigger but firing an SBi12 in line is the easier solution.

Without a changeover relay and solar infeed I wouldn't need the SBi12.

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

I just run 2x160w solar panels on my camper with a single 240ah battery Works perfectly, overkill on sunny days but perfect for cloud and shade conditions.

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Andrew mine is set up with a changeover relay ......

Without a changeover relay and solar infeed I wouldn't need the SBi12.

Ahh that makes sense.

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

First off a three way fridge draws around 15A, it will flatten your 2 100Ah batteries to 50% SOC in around 6.6 hours which is not good, you should be running it on gas three ways aren't meant to run off batteries!

The in car battery doesn't need a DCDC charger, the SBI and a booster diode will do a better job.

If you rewire the fridge so that it is only connected to the cranking battery when the engine is running a they do with caravans with these fridges and run it off gas when camped you won't need a DCDC charger in the trailer either, most likely if you charge the batteries via suitable cable without the fridge connected to them you should be able to charge the trialer batteries ok, then if you must swap the fridge over to them when the car not running but again 3 way frdiges should only be run on 12V whilst travelling and on gas or 240V when stopped.

With one battery in the car and two in the trailer the alternator should be ok.

My opion is forget spending hundreds on chargers, run the fridge on gas when camped and
invest the saved cash in a good solar setup if you don't have one.

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

Thanks All, some great suggestions.

Leigh, just to clarify. Whenever I am camped for the night I am always on gas. I Just stopped to go walkabout for a few hours and didn't think it would kill my battery in such a short amount of time. I don't really think it is a great design to need to open up the camper every time you stop for a couple of hours to put the gas on and light the fridge. I guess in future I will though to avoid a repeat.

Interesting ideas about re-purposing the SBI12. This is something I haddt thought of.

Thanks again.

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

I found when I had a three way as long as the freezer section was full and you didn't open the door
you could get away for a few hours without the fridge running. If you leave it on battery then you
need to watch the consumption, if you have it connected to the batteries your trying to charge then
you will compromise the battery charging if charging directly off the alternator or with a DCDC charger.



Much better to put in a separate circuit to run the fridge when the engine is running, most use either
a fridge switch, or a simple relay switched via an ignition power source.