Adding a solar panel plus Solar controller

[Lordgeorge]

I have a Lunar Solaris, this has a mains battery charger and integrated 12 volt charge input when being towed from the tow car. I have added a solar panel (35W) on the roof, and this connects onto a solar controller in the wardrobe. My question Is:- Can I just connect the 'battery' output terminals from the controller (This is what I have done!) onto the caravan 12 volt cigar style outlets? Alternatively can you recommended a more appropriate / better method of ensuring that the leisure battery is not overcharged, nor that any solar generated power is wasted either when towing or if connected to a site hook up point?
Thank you
George

 

[JTQ]

I have a Lunar Solaris, this has a mains battery charger and integrated 12 volt charge input when being towed from the tow car. I have added a solar panel (35W) on the roof, and this connects onto a solar controller in the wardrobe. My question Is:- Can I just connect the 'battery' output terminals from the controller (This is what I have done!) onto the caravan 12 volt cigar style outlets? Alternatively can you recommended a more appropriate / better method of ensuring that the leisure battery is not overcharged, nor that any solar generated power is wasted either when towing or if connected to a site hook up point?
Thank you
George

Yes but it is most probable that after towing the van's habitation relay will have isolated the Cig -lighter socket from the battery, so the solar panel will contribute nothing till the Dc is switched on again. Then having it on will drain the battery, so self defeating. By far better to connect to the battery directly or via a dedicated solar input if one features on your van's control unit. Such a small panel will struggle to offset the 12 volt system natural drains if the latter is switched on.
Putting the solar controller in the wardrobe is not a wise decision as unless it is a very crude one it will feature battery temperature sensing, and in the wardrobe it will get too hot confusing and backing off the charge voltage. The solar controller for this and voltage drop reasons should be as close as possible to the battery, but ideally not in its enclosure on safety grounds.

 

[ProfJohnL]

Hello George and welcome to the forum.

I'm far from fully conversant with Solar charging systems, as there are so many on the market now. But without having more details (e.g. make and model) of the system you have, I will offer a few comments.

Most of the fairly basic solar charge controllers monitor the storage battery voltage, and simply disconnect the solar panel to prevent overcharging. Some more sophisticated controllers actually control the charging current from the panel to maximise the charge efficiency but these are usually for much bigger installations than you would find in a caravan.

Unless you have a particularly comprehensive control system it's unlikely there will be any interaction of the individual control systems for each of the charging methods to preferentially select any particular source. Essentially if you have solar and car charging active (when towing) or mains (ehu) which ever source has the highest output voltage will attempt to charge the battery.

So this most likely means means you will waste some solar charging current.

Just an observation, a 35W solar panel will help to extend your battery usage and it will keep it topped up whilst in storage, but normally we reckon you need a minimum of 50W or more to become totally self sufficient.

 

[Lordgeorge]

Thank you. You are most helpful. my solar controller is such that it will reduce charging current, but has no temperature monitor. When on site, I will as you recommend, have the option of directly connecting via a separate controller an additional solar panel source from a selection of either one or two 40 watt or an alternate pair of 50 watt panels. My on board leisure battery was declared as not fit for purpose at my last annual service, so I have purchased two larger capacity replacements, leaving the original for now as an always on charge from the mains charger while maintaining a dehumidifier throughout the winter. My wardrobe is well ventilated, and the entry point for the solar cable is conveniently positioned adjacent to the TV aerial also physically above the internal wardrobe
George

 

[Lordgeorge]

I follow your concern, and appreciate your reply, but I have no solar input on my van's control unit, and by mounting the controller close to the solar cable entry point, can readily change the battery connection from my in situe leisure battery, onto a backup that could be on the floor, or through the window. It could well be a crude controller, but does have a range of interesting timing features for the 12volt output. I believed that with only 35w available any overheating would be minimal. My way forward may well be to locate a controller that does incorporate a solar input connection. I know of no source.

 

[ProfJohnL]

............... while maintaining a dehumidifier throughout the winter. .............George

Hello George.
I couldn't help but notice the above comment in your posting.

Using a dehumidifier full time whilst in storage is actually pointless, and is costing you money. Once the moisture content of a caravan has been reduced to the ambient environmental level, there is absolutely no point in running a dehumidifier. The best and simplest and cheapest course of action is simply to make sure the caravan is well ventilated and because caravans always do have some fixed ventilation, all the dehumidifier is trying to dry out the county your caravan is in, as new air will and should be constantly circulating inside the caravan.

If you do have a damp problem, then I suggest its more cost effective to try and solve the source of the water ingress rather than just the symptom.

 

[Lordgeorge]

I am interested to hear that I may well be attempting to take the moisture out of the local environment. I have since owning a caravan tried leaving bowls of salt and occasionally using an electric fan heater to eliminate any dampness that effects such items as bedding or upholstery cushions. The introduction of a basic mains powered dehumidifier has kept all fresh and as good as if straight from the airing cupboard.I will on your advice reduce the useage & check how much the running cost has been.