Thread: Camper Battery

Originally Posted by DiscoMick

A DC-DC is useful if the current flow is less than 20 amps. I have one in the camper to compensate for voltage drop from the engine bay down the vehicle and through the trailer plug to the camper. That's a different situation to in the vehicle with the alternator pumping directly into the batteries.

Hi Mick and again this is a misunderstanding of how batteries charge.

By simply using decent cabling between your cranking battery and your camper trailers house battery, you will still charge the battery in your camper trailer faster, direct from your alternator.

Contrary to most people's thinking, if you have a decent cabling setup, all in good condition, then yes you may still have voltage drop at the house battery.

But you need to understand what is causing the voltage drop in the first place.

If you have say 10m of twin 6B&S cabling running to your camper battery, and you have a low 120Ah battery in your camper, it might be causing over a 1.0v voltage drop between your cranking battery and your house battery.

Now this may sound pretty bad, but it's only half the story.

If your house battery is low, it could be drawing 35+ amps and a 35 amp current draw over 10m of 6B&S twin is going to cause a 1.0v voltage drop.

In this setup, the voltage drop is irrelevant because the battery is still drawing ( being charged with ) 35 amps.

So as above, knowing the voltage is only half the story.

Further more, if you were to connect your 20 amp DC/DC device to the same low battery, where the voltage at the battery from your alternator ( at 14.4v ) is going to be around 13.4v, your 20 amp DC/DC device will only be delivering 20 amps at less than 13.0v. Most people o not know this!

In both cases, the voltage at the house battery terminals will rise as the battery charges, but as your alternator is delivering a higher current right from the start, your battery will reach a fully state of charge far sooner than what your DC/DC device can do.

NOTE, this all relates to moderate to high house battery capacity usage.

If you are just topping a battery up then yes, a DC/DC device will do it sooner, but it's not hours sooner, it is more likely to be no more than 20 minutes sooner.

So if it takes your DC/DC device 60 minutes of driving, to top up your battery and your alternator takes 90 minutes but you are going to be driving for 2.5 hours, where is the advantage????????????????

Sorry folks, in the vast majority of setups, these devices are a poor second rate form of charging when compered to what decent cabling and your alternator can do.

Hi Trout, mate be very careful of anything Collyn Rivers posts up. He is NOT an authority on anything to do with automotive electrics, and is a devout liar.

For an example, he states that "A vehicle's starter motor is designed to work with a 70%-80% charged starter battery"

The battery size used in any vehicle is based on the CCA of the battery. The CCA of a battery is based on that battery being able to supply that CCA at 40% of the battery's total capacity and to do so at a temperature of 0F ( 32C ).

So he he has no idea what he is talking about and you can prove this yourself. If you ever end up with a cranking battery that has, for what ever reason, been discharged down to 40% SoC or 11.9v, you will have no problem starting your motor, because that is what the vehicle manufacturers has set their minimum battery requirements for any given vehicle, but this still leaves a good safety margin.

In reality, you can start a motor on any modern vehicle with a battery as low 11.58v or 20% SoC.

This sort of voltage level has absolutely nothing to do with how batteries are charge in an automotive setup and Collyn is doing nothing more than trying to muddy the waters to try to confuse people into thinking the alternators can not full charge any battery connected to it.

Collin is not interested in the truth, because he has his own hidden agenda, and one he has been caught at many times, as he is out to promote DC/DC devices for one of the vendors.

Now for some facts. There are now more than 4,000 D3, D4 and RRS vehicles fitted with my systems world wide, and the vast majority of those towing camper trailers and caravan, DO NOT have DC/DC devices fitted in their trailer or caravan, yet they have no problems charging and maintaining any number of batteries in their trailers and vans.

This is an E-mail I received a while back and demonstrates the need to get RELIABLE info before equipping a vehicle with a DBS that actually works and not rely on what so called experts in this field claim.

These guys fitted their own DBS and had no problems yet the fifth guy got his DBS "professionally" installed, and look at the results.

Note, the D2 has a constant voltage alternator, the D3 has a variable operating voltages, and the D4s have Regenerative Braking Voltage operation.

This covers just about every type of alternator operation.

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Hi Tim

Sorry for the long email - in the second half of the email my mate with a 200 series wants to know if you can help him

It seems like only yesterday that we installed your dual battery kits in 4 vehicles (D3, 2 x D4, D2) ready for a big trip. We've been back a while so I just wanted to give you an update on how the battery kits went.

In short, they were brilliant. We installed all 4 kits you sent us in one day. Aside from the fiddly process of removing trim pieces and working in the tight confines of a Land Rover engine bay the installation was straightforward with your instructions.#
Throughout the trip the kits never missed a beat - and others on the trip had lots of electrical issues.

On a few occasions the battery guard did it's job cutting out the fridges, but this was usually when we were camped in one spot for a few day (very little or no driving) in very hot weather (making the fridges run almost non-stop). It took surprisingly little driving to provide a good bulk charge back into the batteries.

We travelled the Tanami Track, Gibb River Rd, Kalumburu Rd, Mitchell Falls NP Road and the Great Central Road and nothing rattled loose or played up in any way.

Our friends in a 200 series Land Cruiser, on the other hand, did not fare so well when it came to electrics. Following local advice he had a Ctek DC-DC charger installed professionally by a very large and well known auto electrician here in Newcastle. They also installed an auxiliary circuit for his fridges and accessories etc connected to the aux battery.

In short the system never worked properly. Initially the DC-DC was installed in a very hot part of the engine bay making it cut out once the engine warmed up. We repositioned it behind his grill but even then he only got a useful charge on big driving days. On days where we did short trips around camp he was always having problems with a flat aux battery (including the extra aux battery on the trailer). To further add to his woes the auto elec did NOT install any form of low voltage protection on the circuit for his fridges and accessories. He ran his batteries far too low a few times and it didn't take long for the aux in the engine bay and the aux on the trailer to both die completely.

He couldn't believe how well our systems worked. So he was wanting to find out a little more:

Feel free to use my feedback as a testimonial if you wish.

Thanks

The guy with the Toyota has now had one of my DBS in his vehicle for a year or so and has not had one of the problems he suffered with, when he had the DC/DC device fitted.