solar panels

[Sirus]

Have been looking at maplin.co.uk at solar panels for recharging my domestic batteries,have posted before that I have no access to shore power and was wondering if a 15watt panel would be of any use to charge two 120amp batteries and how long would they need to be used to make any difference to the state of charge.
Thanks for any replys......

 

[ccscott49]

Sorry, 15 watts isn't going to do it, especially in UK waters, where the sun isn't shining much. You will have to get advice from a solar panel type person, but I do remember an article in PBO explaining it all. I'm sure theres lots of guys on the forum who will exlain things, but I would expect for two 120ah, batteries you will need at least 30watts to keep them topped up, maybe even more.

 

[halcyon]

If you only want to maintain the batteries at the level you left the boat, 15 watt may be ok. Doubtful if you will get any recharge of low batteries of that size, with 15 watts in the UK.


Brian

 

[Shanty]

I've been using a setup consisting of two 110aH batteries, each having a 10w panel connected to it for the past 12 years. For daysailing use once / twice a week, the panels keep the batteries fully charged. When I go away for longer periods, panels plus a boost from the engine seems to cope. The only time this setup hasn't coped was during a four day spell stormbound in Canna harbour - had to run the engine to charge the batteries.

A bonus is that during the winter months, I leave the setup connected, and this keeps the batteries charged.

 

[vyv_cox]

It depends on the demand on the batteries, any users when the boat is unattended and the state you leave them in. I have a 40 Watt panel charging 2 x 105 Ah domestic and a 105 Ah starter batteries. Since I always use my engine for at least 15 minutes entering my berth, the batteries are reasonably well charged on leaving them. The panel ensures that all are kept up to maximum level all the time, a significant factor in prolonging battery life. Voltage is always over 13 when we arrive on Friday night, summer and winter.

In mid-summer, when sailing to the max and using engine to the min, the panel cannot cope with all drain, including instruments, lights, domestic water pump and refrigerator, but it does help a great deal. Without the refrigerator it would probably keep everything charged full time. Highest current we have ever seen from this 2A unit was 1.7A, midsummer. 0.6 - 0.8 A would be a more realistic figure. The beauty of them is that at this time of year they are producing for up to 16 hours a day and even at small current outputs this can be enough to replace all useage. Except the refrigerator.