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solar cells

I have 5x 110amp hoise batteries and 1x 120amp starter battery. I am returnimg to Australia for 3 months in early December and am considering solar cells to trickle feed batteries and hopefully ensure they are not ruind by an unforseen cold snap. What size cell will I need to do this? Will I need two- one for domestic and one for starter?

Asked by: peter osullivan  | 4.44pm, Wednesday 19 September

WW says:

It is possible to independently charge both the starter and the domestic batteries from one solar panel if you use a solar charge controller. These regulate the charging current and can be set to divide the current between the two batteries in a selected ratio.
Working on about 4 hours of good daylight per day in the winter, the minimum size of solar panel required to compensate just for the self discharge of your batteries would be about 30W. It would however be better to double this to around 60W if possible, as this will put more into the batteries and keep them in good condition, rather than merely compensating for their self discharge losses.

Rupert Smedley  | 6.43PM, Wednesday 19 September

Some of the solar controllers you can buy (and off the Internet there are some good bargains) which allow you to choose the proportion of charge which goes to each battery bank. This means that you might choose say, 25% to the engine battery and the rest to the domestic bank. Some also show state of charge and allow you monitor charge put into the bank, which gives a
Very accurate method of analysing the performance of the solar panels.
I agree with Rupert- a 60W panel would be much better, though 30W would be the bare minimum, as the panels performance deteriorates over years- though slowly. Also, a flat mounted panel is far less efficient than one mounted at an angle to the sun, so a bigger panel is a useful investment for the extra £20 or £30 involved.

Mark Langley  | 2.51PM, Thursday 20 September

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