Which solar panel for an auto bilge pump system?

[anoccasionalyachtsman]

I'd like to fit a pump to a dayboat just to deal with rainwater, and my first thoughts are a small Rule 500 auto pump drawing 1.6A for a notional 30 litres/min at 0 head. Next thought is a 12V 7A motorcycle battery and so I thought a 5W panel would do the job. Given that the worst I've seen in a week is about 100l I don't think it'll be too highly taxed. I use the boat at least once a week, and so the job of the panel is really just to keep the battery happy rather then running it down too far and killing it before manual recharge (river mooring).

Where I'm completely out of my depth is the panel. I don't want a Rolls Royce solution, because the odds are that it'll get nicked, but I don't want to buy cheap and twice either. Do any come with a reasonable controller giving a suitable output for charging lead/acid? What's a good panel technology without being bleeding edge?

 

[William_H]

First question is do you really want a battery in the boat. Save on costs, batteries don't last for ever. If you go solar to pump. A 1.6 amp solar panel is going to be around 30 watts. Solar only will of course only pump when sun shines. If you go more solar power you will need a regulator to bring the potential higher voltage of the panel to 12 to 14 volts. Something like this will do.https://www.ebay.com/itm/DC-DC-Buck...659085?hash=item3f8636830d:g:5GYAAOSwwpdW3ZZM
If you go for a battery to power the pump then a smaller panel may do the job. The success ends up being entirely dependent on the amount of water which must be shifted. So probably OK with the small battery you propose although an old car battery might be cheaper and more capacity. You will need a charge controller for a small battery but not for a larger battery with smallish panel. Look on ebay for Chinese suppliers I think you will find them OK. Best IMHO in small panels are the all resin types. Well sealed and no ali to corrode. Something like this https://www.ebay.com/itm/18V-6W-Sol...m=263057042774&_trksid=p2047675.c100005.m1851 might be OK without a controller on a 7AH battery.
Do note that with the small battery if you really need to move a lot of water you could end up killing the battery and still have water in the boat. But that is a remote risk it sounds like. ol'will

 

[Mr Cassandra]

I had a small vacuum pump on my old boat it worked on wave action . Cannot remember it's name.
Also good for getting cold beer in the fridge up to your glass on your deck , when new.

 

[anoccasionalyachtsman]

I didn't want to delete it, bliddy 'phone...

Long reply short

Love the idea of wave power, but there are only ripples in my bit of The Hamble. Tide power ...?

I'd like to keep the battery in to deal with nighttime rain, I'm getting osmonoia with respect to bilgewater.

 

[pcatterall]

Sounds like a ( reasonable!) plan!
Incorporating a simple voltage cut out ( as sold in camping stores etc) which ensures your battery level can't fall below ( say 11.6v ?) will preserve your battery.