Batteries and charging options

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Batteries and charging options

Post by Labexpress » Mon Jul 23, 2018 10:17 pm

We have a Mars Extremo hard floor camper. We had a second battery connected in the factory so it’s running I think dual 55a/h batteries. The trailer has Anderson plug for connecting to solar panels, but at the moment we don’t have the Anderson connection in the tow vehicle. My questions are around charging options:
1. can we use a solar panel to charge the battery, whether we’re at home of on the road?
2. should we disconnect the batteries when storing trailer during winter (Jul to Sep)?
3. Presumably we need some kind of adaptor to connect 240v mains power in a caravan park to charge battery (if this is possible)?
We know during use we shouldn’t let batteries go below 25% or so, and will generally only be powering a fridge and small LED light strips inside trailer. We have separate lighting for annex at the moment.
Advice gratefully accepted. 8-)

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Re: Batteries and charging options

Post by robcaz » Tue Jul 24, 2018 9:52 pm


First up is there a DC to DC charger installed next to the batteries in your camper trailer? If so what make, model & amp output? What make & model batteries do you have? This will allow us to answer your questions in detail.

1. In general you can use solar panels to charge the batteries when camping or at home.

2. Deep cycle batteries have minimal self discharge, so you do not have to isolate them. You will find it of benefit to put your solar panel out to fully charge the batteries once a month if the camper is not in use. However to get the best life from your batteries a 240 volt multistage charger around 10% to 15% percent of the battery capacity is recommended. That is two 55 amp hour batteries wired in parallel (110 amp hours) require a 10 to 15 amp multistage charger.

A 240 volt multistage charger is also handy to fully charge your batteries after several days of bad weather on a powered site at a caravan park. The recommended 105 to 15% will usually get your batteries to capacity overnight.

The positive of the chargers (240 volt or 12 volt ie DC to DC) are connected to a positive of one battery while the negative of the charger is connected to the negative on the opposite battery, so both batteries are being charged as one. The fuse block is connected to the same terminals. You will find a diagram in the link below above the 'our setup' heading.

3. If you want to connect to a 240 volt outlet at a caravan park the safest way is to have a 15 amp inlet along with a 15 amp breaker installed by a licensed electrician.

A good rule of thumb to follow for best battery life is not to discharge your deep cycle battery below 50% capacity or 12.2volts. Using a voltmeter to check the state of charge of a deep cycle battery while it is charging will only show the surface charge. When discharging a deep cycle battery the voltage will be below its true state of charge. You need to allow the battery to 'rest' for at least a couple of hours, preferably eight, for the surface charge to dissipate.


You will find some useful info in my article on the tech tips page ... e_draw.htm
happy camping
Rob & Carol
Australian CamperTrailers Group co-owner

We're just two lost souls swimming in a fish bowl, year after year

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