Always a good idea to search the subject you are enquiring about. I did a search on "Solar Panels" alas not too much to help you: [You must be registered and logged in to see this link.]
Yes the solar panels do work but it depends why you need to charge the battery and then what your options are.
As always with these things I don't know who I'm pitching too so if I insult your intelligence then sorry but it's better to over explain rather than lose you. Also it makes the piece readable by anyone who had not even thought about the subject.
You want the battery to last three days or you would like to possibly be able to go on longer rallies and still have power?
Why you don't have enough power; either the demand is too big, the battery too small, the battery is defective, or it isn't being charged properly.
Battery not charging properly. What do you charge the battery with? If you installed a caravan specific battery charger you may have problems charging. Sig units, TP2s all seem to fixate on the possible danger of the battery gassing if the charging voltage is too high. So they charge at a max of 13.8V and therefore take a long time to charge as the rate of charge depends on the difference between the charging voltage and the voltage of the battery. See [You must be registered and logged in to see this link.]
Also the battery may not charge fully at all.
While the caravan type chargers are OK while you are on an EHU (Why have a battery on if you use EHUs?) and they are connected for days they are not what you want if you are going camping on Friday so just stick the cable onto the Dandy on Thursday. An intelligent or even a dumb charger would be a better option. Also with the intelligent charger you can leave the battery hooked up over winter or stick it on charge for a day or so each month. We are not talking big bucks £13.99 for the Aldi or Lidl charger.
Demand too big: What are you using the battery for? Just lighting and the water pump or loads of electronic entertainment? (There should have been another thread on solar power. I'm sure I've had a conversation with someone who wants battery power to facilitate running a pump for someone with [You must be registered and logged in to see this link.]
) If you have loads of electronic equipment that you want to run then yes you need a larger or more batteries or constant charging. Conversely if you are just using lights and the water pump the battery should last so you are either suffering from another current drain or something is inefficient. Light efficiency improves from Tungsten bulbs, halogen, fluorescent to LED. I'd suggest measuring the load but the demand might be a little too much for a cheap multimeter. If you have over a 2 amp reading on your multimeter you might try to measure the load with different appliances running.
Defective battery or battery too small: We sort of covered improper charging. Next question what did you do with your battery over winter. Batteries don't like being left. How to asses your battery? The load test meters used on car batteries aren't suitable as test the batteries ability to crank a starter motor over. You can test the voltage when charged. After giving the battery a suitable rest period (otherwise a false level of charge is shown) you can measure the voltage across the battery. 12.7V or over indicates a full charge. You can measure the specific gravity of the acid if you want to. I've never used an amp hour meter but measuring individual items then guestimating the time they were in use should give you an idea of the charge used.
You do realise that you should only use about 50% of the charge in a battery don't you? If you have an 80 amp hour battery you should only remove about 40 amp hours. If you have been caning the battery it's most likely knackered. A regular check with a voltmeter helps at 12.3 or 12.2 volts you need to be recharging the battery. The camping and caravanning club guide is OK ish (there is a debate as to whether such a thing as a leisure battery exists) the downloadable PDF shown at the bottom is much better. [You must be registered and logged in to see this link.]
Charging in the field. Yes solar panels work though for many people I'd not recommend them. For most car users who go out for a drive every other day the simple answer is a charging point in the boot. This is especially simple if the car was wired with either a 12S or 13 pin connector. The available amperage from a power point that was pre wired into the boot would have to be assessed.
If you have a big battery it may be a pfaf pulling the battery out and re loading it. But you do then have access to a definite high rate of charge. In your case I realise that you are using a trike. As it has a 2 litre engine I'm assuming a car alternator of 400, 500 watts or more not a small bike alternator of 180 watt. The only problem I see is if you can mount the battery. If you can and you tend to go on rideouts I'd suggest this solution. What you then need is a self sensing [You must be registered and logged in to see this link.]
Solar panels. There are tables you can access that give you projected rates of generation dependent on location and time of year. e.g. a location near Truro would be better than one near Thurso and June is better than January.
I've no idea where this next statement comes from so do check it out. As a ballpark I think I was told not to ever expect better than half the quoted output. So a 40watt panel gives at best 20 watt so with any further losses you are looking at a best of about 1.5 amp hours per hour. Over summer 15 amp hours per day may be more than adequate. I'd always suggest larger is better. prices may be at an historic low. See articles on the EU and China vis a vis China dumping panels. Work out which type you want. See how you are going to mount and prevent theft. Consider if you want the panel to track, then check on the need for a control box.
As per normal I've gone round the houses and you may have known most of the above.
Still keen to see pictures of the Dandy and the trike.
Last edited by Tow Itch on Sun 26 Jan 2014, 8:43 am; edited 1 time in total (Reason for editing : Not Included The C&CC Guide Mentioned.)