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Catalina/Capri 25/250 Sailor's Forums

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Solar Trickle Chargers

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bmelchionda
1st Mate

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63 Posts

Initially Posted - 12/10/2006 : 06:54:03

I’m keeping my Catalina 25 in the water this winter with the proper bubble wrap. I would like to keep the batteries in the boat so the bilge pump can stay operational in case of an emergency. I was looking at the “2W Battery Saver SE - Solar Trickle Charger” which is available at West Marine for only $35.00. Will this satisfy my needs of keeping my two batteries fully charged during the winter months? Logistically, will I be able to connect the panel to both batteries or will I need to choose 1 and bring the other home for basement storage and charge.

Your thoughts and recommendations are greatly appreciated!

Thanks!

'86 Catalina 25 Tall Rig

Edited by - on

OLarryR
Master Marine Consultant

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USA
3465 Posts

Response Posted - 12/10/2006 : 07:58:14

I would say "No".

The guide is a 20 watt solar charger puts out a max of 1.2amps/hr, 10 watt - a max of .6amps/hr and a 5 watt puts out about .3amps/hr.

A battery loses something a bit less than 1 amp/day just sitting around. It differes summer to winter between about .5amps/day to about say .9amps/day. So...let's use .8amps/day to be safe.

If we are talking about 1 battery trickling out .8amps/day and a 5 watt solar charger getting a max of .3amps/hr...would that be enough ? Well...that is the guide...about a 5 watt solar charger for handling the trickling effect of one battery. The reason is that you only get a max of .3amps/hr...so what does it normally put out ? That depends on a number of factors with the biggest being: Obstructions from full sun, number of rainy/overcast days, angle of solar collector to the sun. In general, the .3amps will put out only .3 amps if everything is perfect and they really never are and so best to consider that you will get at max about half or slightly less than half the max amps especially if your solar panel is not tilted to the sun at all times (perpendicular). Figure you will get instead of .3amps, you will get about .15amps/hr.

.15ampshr from a winter sun will give you maybe 5hrs a day for a total of .75amps/day and that is considering no rainy days. Since you may get a bit more than 5 hrs and maybe a bit more than .15amps/hr, then figure that will balance out any rainy days.

If you have two batteries, then get 2 - 5 watt solar panels for charging each separately or less than ideal...but doable is get one 10 watt solar panel for the two batteries.

I have a 20watt solar panel for the 2 batteries because I use the panel all year for some loads such as running lights, etc (see installation info on my website).
But if you use a solar panel more than 5 watts per battery than a solar controller is needed to avoid cooking off the battery water.

Why do they sell a 2watt solar charger ? Well...maybe if it is tilted perfectly toward the sun and during the summer months, the sun is out longer....it would help to trickle charge it but maybe not fully. It would still be of benefit and it is at reasonable cost.

I would check websites for inexpensive 5 or 10watt solar panels. Also, they are not all created equal. The rollout/flexible ones have advantages/disadvantages as do the rigid ones. But that is....another long story altogether.

Edited by - on

OLarryR
Master Marine Consultant

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USA
3465 Posts

Response Posted - 12/10/2006 : 08:44:33

I was doing some checking on Northern Arizona Sun & Light, the supplier of my 20 watt solar panel. I wanted to see what they had to say as to the accruacy of my above posting. In the Section on solar controllers, they have a link to more info on how solar controllers work and in that section, they provide an example regarding 2 golf cart batteries and the use of a 5 watt panel being able to handle trickle charging.

The thinking, however, is the ideal case, because they utilize .3amps/hr as the charging rate produced by a 5 watt panel. That is the ideal rate which is achievable but only under perfect conditions which never exist...that has been my experience.

I originally tested my panel under all conditions with my solar controller so I could see the perfect condition and not so perfect condition scenarios. Under exact perpendiculr to the sun and full sun, no clouds, the panel puts out rated amps. If you put one thimb in the way of the panel or a cloud comes into view or the panel is not exactly perpendicular to the sun, then the panel puts out anywheres between zippo and about 2/3 of the rated amps.

So...based on the baove and my own experiences over the year since installing the panel, expect to get only about 1/2 the rated amps on a regular basis. That's why I used .15amps instead of .3amps in my above posting. If you go with the max rating...well then a 2amp charger...for one battery will work. But in reality...it will probably not maintain full charge due to trickling effect since the only day it will probably see it's rated amps is the day you experiment with it under perfect conditions.

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 12/10/2006 : 09:53:44

Northern latitudes in winter = low sun angles, cloud cover, low temps, short days.

You're probably not going to get much out of solar panels. I think you will have to install quite a bit of extra capacity to keep up... maybe double or triple the published rating of the panels.

Somewhere out on the web there's probably a solar chart for your area.

I take it you don't have shorepower available?

Edited by - on

bren737
Captain

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291 Posts

Response Posted - 12/11/2006 : 15:06:16

Bryan,

I'm not electrical engineer but can tell you from 'real world' experience that (at least here in Texas (i.e. lots of sun)) the 2 watt charger from West Marine works fine. That's the exact same one I've used on my boat for the last three years.

I've got two switched batteries which I set to 'both' before leaving the boat. When I leave I set the charger on the floor of the cockpit. Even in times of relatively little bright sunshine for many days I have always had fully charged batteries next time I get to the boat. Works great in these parts. . .

Edited by - bren737 on 12/11/2006 15:07:39

Turk
Admiral

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USA
736 Posts

Response Posted - 12/12/2006 : 02:44:50

I've owned a 5 watt panel up here in northern Ohio and I've found that it did work well between sailings (every 3-4 days) on one battery. The problem arises when you get behind after a heavy use like staying overnight using running or cabin lights. I "re-thunk" the problem and purchased a 65 watt panel along with a Morningstar controller. It worked very well! It now powers the system on my 250 that has two group 27 batteries with ease. The panel is large though. I set it on the cockpit floor (it actually helps reflect light on to the panel) and it is out of sight, out of mind from visitors to our marina (I'm on a mooring). It is a rigid panel from BP (used cost - about $275) and is about 20 x 47 I think. If I had it to do again, I would say a 30 watt panel at half the size would be perfect for my needs. The smaller panel would be easier to remove from the cockpit to the interior cabin before sailing. My larger panel has to find itself a place in the V-berth and can get in the way at times. I used water tight deck fittings in the cockpit to plug in the panel and remember, the controller stops the power from moving the opposite direction and you cannot use the fitting to power other items like a tiller pilot. I had to add a second fitting for that.

Conclusion: 30 watts is perfect.

Edited by - on

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