10 Watt Solar Enough?

[Cheechako]

Is a little 10 watt solar panel enough to keep the batt's topped off while dry stored? 5 watt?

[barnakiel]

Trickle charger?

[Cheechako]

Yea, just looking for something to keep em up for maybe as much as 6 months...

[barnakiel]

Look up Calder's book - he gives the proper size. Still I would think - how do we know how much sun there will be ??? So maybe just the bigger solar and a small solar regulator / rather than the smaller solar direct?

b.

[Cheechako]

It's in Florida. There would essentially be no draw... everything off but the bilge pump, but the boat doesn't seem to accumulate any water now even in the torrential Fl rainstorms... yea I was wondering if using a 5 watt with no regulator would be OK... thought maybe someone out there has done this....

[barnakiel]

I hope you get the answer by tomorrow. But if not, I will look up the book tomorrow (I have it in my friend's boat) and write up. The discharge is related to temp and the type of battery you have. And it cannot be done to gels.

b.

[Portobello]

I have a 10 watt solar panel on my boat - our winters can be quite gloomy (especially the one just gone) and it keeps my batteries well topped up. We are 42 degrees south here so the winter sun is weak.

[Cheechako]

you using a regulator?
I have two 8D batteries, wet cell.

[barnakiel]

We used to use a 80 W solar into 160 Ah, no reg. But it was when cruising and then we used the engine only to make sure the engine was nicely oiled and ready. No other sources. Wet, deep cycle buckets.

In port it is different - the panel overcharges (as it well should). We disconnected the panel and plugged in the 4 stage (3 stage plus supply) charger.

I believe the discharge for normal (wet, deep cycle, not the newer low-discharge that you can buy from Vetus ao.) is up to 1% per day in hot climes.

This would call for 1 Ah daily charge per 100 Ah of the battery bank. If you consider a 4-5 hr sun it means 1/5 times 12 = 3 W panel (per every 100 Ah of battery bank). There is some loss too (and 12 Volt is not enough), so say 5 W.

But have you ever seen a say 5W panel with 36 cells ..... ???

So my way would be - a bigger panel with a regulator or a trickle charger from the shore.

[elf]

We have a 10w panel that keeps our batteries charged just fine for months at a time here in NC.

[GordMay]

Charge Controllers (voltage regulators) are not generally required on Solar Cells that produce less than 1.5 to 2% of the Battery’s Amp-Hour capacity, so an unregulated 10 Watt PV Charger will be acceptable on a battery as small as 40 Amp-Hour capacity.

A Flooded Lead Acid battery has a typical Self-Discharge rate of about 4% to 6% of Amp-Hour capacity per week. Accordingly, a 125A-H battery might self-discharge as much as 7.5 Amps/week.

Since a 10W solar panel might be expected to produce between & 10A 30Amps/week, it should more than suffice in maintaining a small battery bank.

[avril25]

I have three solar panels for a total of 105 watts... two 125 amp hour batteries, lead acid type, and a charge controller. This set up has served me well all summer in sunny New England. I use my boat every weekend, lights, radios, dvd player, chart plotter etc with out thinking too much about it. by the time I leave for home, the meter is in the red. When I come back on friday night th meter is in the green. Lets do it again
I say....

[barnakiel]

As per Gord, just make sure you find a (so small a) panel that will deliver the trickle voltage - not easy if we are talking 5-10 W units.

b.

[Hurricane Harry]

It works here 57N 58N to use solar in winter to keep batterries fresh and we do not have many hrs of sun in dead of winter. But Im not sure about capacity of cells or batteries./ Harry

[Cheechako]

any reason this wouldnt work? RAMSOND NEW 10 W WATT 10W SOLAR PANEL BATTERY CHARGER - eBay (item 400074089598 end time Sep-23-09 14:53:37 PDT)