Keeping Batteries charged

Keeping Batteries charged.

When we bought our Autoquest some of our friends had a 50W stand-alone solar panel which they found adequate. As our camping at that time was often in places where we were around to turn the panel towards the sun we bought one ourselves, from Solar Solutions. It featured a fly-lead with 7 pin 12N plug & socket. The fly-lead was permanently attached to the leisure battery terminals and coiled out of the way when the panel was not in use. Because a stand-alone panel can be moved to face the sun at a better angle, a 50W panel is roughly equivalent to an 80W roof mounted panel.

The Autoquest was wired to top up the leisure battery from the alternator/starter battery when driving but had no circuitry for topping up the starter battery at all. During the first winter we had the Autoquest the starter battery was flattened by the alarm (and possibly not switching the radio off completely). I tried a Solar-Powered 12V 1.5W Battery Trickle Charger from Maplins (Ł9.99) but found it impossible to set up so as to be pointing towards the sun for long enough to make a difference. Later (and much more successfully) I used a Tronic T4X charger (from Lidl) on the starter battery from time to time in winter when it tended to run down through powering the alarm. I could attach the crocodile clips to the battery and plug the unit into one of the van sockets, power to the van being supplied from a socket in our garage via the hook-up lead. Subsequently I fitted a Battery Charge Manager (BCM 12) from CAK Tanks which kept the starter battery topped up, in addition to the leisure battery, when on mains hook-up or when the solar panel was in use.

The Burstner has an Elektroblock EBL 99 Transformer/Rectifier fitted so was already wired to keep both batteries topped up when on hook-up. We decided to have an 80W solar panel mounted on the roof. We had the job done by Dave Newell who we had known for several years – we always said that if we trusted anyone to make holes in our van it would be Dave. He was able to wire the panel into the Elektroblock so the panel also keeps the starter battery topped up once the leisure battery is fully charged. I still plug into the mains from time to time over winter to make sure both batteries are topped up because the panel doesn't receive enough winter sun to maintain both on our drive.

	Another method of topping up the batteries that we found interesting was wind power. Horizontal axis turbines, though, are expensive, awkward to transport and mount and can be noisy. At one rally a friend was using a vertical axis wind turbine (VAWT) which was virtually silent but, unfortunately, was also very expensive. In about 2010, Maplins started selling a VAWT which was much cheaper, at Ł150, but the Autoquest didn't have an appropriate place to fit one nor roof access to put it up and take it down regularly. Both of those factors were overcome with the Burstner but Maplins discontinued the model. However, I was able to obtain a second hand VAWT from a friend in April 2015. I mounted the VAWT by using U bolts to fix a plate to the horizontal rails at the top of the ladder. The VAWT was bolted to the plate to ensure that it did not move. The cable fixed to the VAWT is only short so I made up an extension lead which was permanently attached to the leisure battery (with in-line fuse) and connected to the VAWT using an in-line N-type plug & socket.
	The output is only 4A/50W max so there is no need for a regulator. It doesn't seem much but it was intended merely as an add-on to the solar generation with the hope being that it would provide that little extra during the winter months which have less sunshine but tend to be windy. The theory was that even if it averaged only half an amp per hour on such days that would be 12 amp hours to add to what the solar panel generates, which is a significant amount in terms of our usage. Unfortunately we found that the wind wasn't reliable enough, especially at night, so the VAWT contributed very little. It was also a bit of a pain to transport and to put up and take down so we soon stopped using it.

Some control panels have a switch which allows leisure circuits to take power from the starter battery rather than the leisure battery. The purpose is to provide power for short periods if the leisure battery is flattened somehow. Using power from the starter battery for extended periods will soon flatten it, especially if there are no recharging arrangements in play - we know because we did it inadvertently in the Autoquest once.

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Last updated: 26 May 2016