Intro to me and my new Ranger 23

[SalientAngle]

7 amp panel is pretty big...over 100 Watts...probably not a grab at the store and go sailing install.  If he means 7 watts, that is only good for replacing self-discharge of the battery, not for doing real work.

Ohm's law comes to mind (I=V/R); and the volt=watt/amp as well... ie, 12volt=84watts/7amps... but, if a 7watt panel, we see over one-half amp...

[Captain Smollett]

A solar panel does not operate at 12volts. It is closer to 16-17. My 85 Watt panel is rated to deliver 5 amps, for example.

[SalientAngle]

A solar panel does not operate at 12volts. It is closer to 16-17. My 85 Watt panel is rated to deliver 5 amps, for example.

absolutely, you need at least 15 volts to even think about charging a battery... 12 volts used simply to illustrate the math... if you had a 100amp hour battery, it would take over 350 hours or more to charge with the small "maintenance" panel and more considering leakage... cheers

[David_Old_Jersey]

Lol! - Amps, Watts (volts?), that's the stuff I get lost on.....amongst other things  ::)

Please don't bother explaining to me.....unless I am doing something it goes in one ear and out the other - non-stick!

[SalientAngle]

Not trying to open another can of nematodes, but, I rarely go anywhere without my small 2000w portable generator inverter... not for regular use, but, has been handy many, many, times...

[David_Old_Jersey]

Actually a small generator instead of solar might work better / cheaper....even if more smelly / noisier / a bit of a PITA....can even use it at night!

[northoceanbeach]

7 watts. So it won't charge the battery?  What is it for?  Who cares if I keep it topped off if I can't use it. I really only want to run led light sometimes ad charge my phone. It's not that small it looks like it would do something.

[SalientAngle]

7 watts. So it won't charge the battery?  What is it for?  Who cares if I keep it topped off if I can't use it. I really only want to run led light sometimes ad charge my phone. It's not that small it looks like it would do something.

designed to keep battery topped instead of the gradual leakage that happens... should be fine for your limited energy budget, but, you will still need to charge the battery, preferably, at around 50 percent capacity.

[Captain Smollett]

7 watts. So it won't charge the battery?  What is it for?  Who cares if I keep it topped off if I can't use it. I really only want to run led light sometimes ad charge my phone. It's not that small it looks like it would do something.

Flooded cell lead acid batteries have pretty high self-discharge rates, so if the battery "just sits," it drains.  These small solar panels are designed to simply put that self-discharge back into the battery so it stay charged.

Think about if you have a boat on a trailer or in a slip that you use once every few months (or an RV or something).  These small chargers are so the battery is actually charged when you go to use the boat/RV/whatever.

So, essentially, your little solar panel is only putting back into a flooded cell battery what it is loosing through it's own "internal short," not really adding back electrons that YOU have taken out to do useful work.

The self discharge rate on AGM lead acid batteries is much, much lower.  So, if you happen to have one of those, you might get some useful 'recharge' from your 7 watt panel, but it won't be much.  

To tell the difference...either look on the label  :) or look for water fill ports on top of the battery.  There are also gel cells, and truthfully, I cannot remember what they self-discharge but I think they are less common on small boats.

A 7 watt panel will give you about 300-350 milliamps.  The rule of thumb for solar is to figure 5 hours of charging per day at the average full output...tops.  You might get less.  Let's say 300 milliamps, or 0.3 amps.  The 7 watt panel gives you about 1.5 amp-hours per day, maximum.  Even if you get as much as 500 milliamps out of that panel (which I doubt), that's still only 2.5 amp-hours per day with MAX charging from that panel.

Cell phones can be electron hungry.  I don't know what yours will take to charge - you should measure it.  That's the only way to know for sure.

A good guesstimate current draw for LED fixtures is about 100 milliamps or 0.1 amps.  Yours may be more or may be less, but that's a good guess to see where you are.  That's each.

How long do you run it?  That's the important question.

If it's a nav light or an anchor light (you did not mention anchor lights...??) that is on 8-12 hours per day, you are looking at up to about 1.2 amp-hours per day or pretty much ALL you can count to get out of your solar panel and none left over for the phone.

On the other hand, if it's a reading light on one hour per day, you should be okay.  0.1 amp-hour per day for the light is pretty insignificant.

Ideally, you want to be able to put in everything you take out every day.  The sun might not be shining tomorrow, for example.  Or for days at a time.  The "rule" with battery systems is to keep them charged as much as possible.  Deep discharges shorten battery life.

When you get a chance, measure your current draws for everything electrical on your boat, and estimate (overestimate a touch) the amount of time each item will be "on" (or charging, in the case of things like your phone).  Multiply amps x time in hours to get amp-hours, then add them all up.

That's your energy budget.

Once you know that, you are no longer guessing about what battery you need or what solar panel you need to keep it healthy.  It's measurement, not guessing.

Hope this helps.

[Godot]

7 watts should be a pretty darn small panel. I have currently installed a 15 watt panel and it isn't that large. I have a bunch of 20 watt panels (well, 4) that I'm going to install on my dodger (I figured more smaller panels would give me more tolerance for the inevitable shade given the location).

That said, for your very minimal needs, and assuming a pretty small battery, I think you will be OK. I'm going to take a wild guess and assume you have a flexible panel. If you can find the room, on a rail or cabin top or someplace out of the way that will get a reasonable amount of sun, a smallish 20 watt crystalline panel might take around the same amount of real estate and give a little bit of extra wiggle room.

Lets work some numbers...

A group 24 battery might have a capacity around 85 amp-hours when new. The self discharge rate is somewhere around 5%/month, or a little more than 4 amp-hours/month, or about .14 amp-hours/day. That is really not a lot on a daily basis. Let's say a quarter amp-hour/day to be conservative.

A seven watt panel, charging at 17 amps for let's say an average of five hours/day (being conservative...clouds happen) should give you a little better than 2 amp-hours/day, subract your .14 amp-hours self discharge and you are just a little under 2.

Are you planning on sailing at night? You will need to run nav lights (I don't know, maybe 3-4 amp-hours using LEDs over an 8 hour evening). That would put you at a power deficit with the seven amp panel that you probably wouldn't have with the 20 amp panel. If you aren't sailing at night and only need a LED cabin light for a few hours, then you will probably be working at a minor surplus. I'm not sure how much your phone will take to charge.

[Godot]

Oh, yeah. Anchor lights. A Bebi Owl LED anchor light would set you back a little less than an amp-hour every night.

Given the criteria you've given and the minimum needed electronics, it sounds like your seven watter will be OK. No VHF radio, though? Even a hand held will draw some amps, although last I checked a radio was not required gear. At least a simple GPS is pretty standard equipment now-a-days as well, although no one says you have to have one (it's hard to believe that GPS is only a couple decades old, and it wasn't all that long ago that people meandered the earth without it).

[CharlieJ]

No VHF radio, though? Even a hand held will draw some amps, although last I checked a radio was not required gear.

Unless you are running any part of the ICW- I don't know if the bridges and locks even remember sound signals- All VHF now. So if on east or gulf coast, have at least a hand held

[northoceanbeach]

I've got a handheld GPS ad a handheld VHF and a drawer full of lithium aaa and aa batteries.  No anchor light.  It's on my to do list but the cords are coming from the mast into the cabin unattached.  Doesn't seem like many boats use anchor lights, but I could get a little lawn solar light and put that in deck and haul it up a halyard each night.

I'm not going to be doing much night sailing since I'm in such a rocky confined area, but should I get stuck out ill need to use them.

[Captain Smollett]

I've got ... a drawer full of lithium aaa and aa batteries. 

Is that a long term solution, or just an expedient?

No anchor light. 

Bebi Owl

Bebi = Best anchor lights on the market.  Bar None.

[CharlieJ]

I've got a handheld GPS ad a handheld VHF and a drawer full of lithium aaa and aa batteries.  No anchor light.  It's on my to do list but the cords are coming from the mast into the cabin unattached.  Doesn't seem like many boats use anchor lights, but I could get a little lawn solar light and put that in deck and haul it up a halyard each night.

I'm not going to be doing much night sailing since I'm in such a rocky confined area, but should I get stuck out ill need to use them.

Go to this link (from here) and read all you ever wanted to about anchor lights- 6 pages of discussion

http://sailfar.net/forum/index.php/topic,524.0.html

[David_Old_Jersey]

For a cheap anchor light I would go with a Hurricane Lamp. Can double for use down below if batteries run flat.

[northoceanbeach]

It's a long term solution I guess.  The VHF I haven't had to change batterie since I got it months ago. The GPS eats them but what choice is there?

Think I need an anchor light on?  I'm not seeing them used all the time. The way you can tell if the boat will turn an anchor light on is how expensive it was. Mine falls into the inexpensive category so I think I've of the hook. Ha ha. I has jokes. I'm ON the hook, but whatever.

[Captain Smollett]

It's a long term solution I guess.

May get expensive.

  The VHF I haven't had to change batterie since I got it months ago.

Are you using it?  I mean transmitting.  Rx does not use much juice, but actually talking to someone uses more.

The GPS eats them but what choice is there?

Don't know what model GPS you have, but there are cables to plug-in or wire them into the boat's battery.

For example, my Garmin 72 uses this:



Data + Power Adaptor

And / or you might consider getting rechargeable AA batteries and a charger.  You can even get small solar ones that people use backpacking and the like.

Think I need an anchor light on? 

Yes, *I* think you do to be safer first and compliant with the law second.

I'm not seeing them used all the time. The way you can tell if the boat will turn an anchor light on is how expensive it was.

Doesn't have anything to do with how expensive the boat is.  The law does not say "only expensive boats have to show proper lights."

What it may say more about is the seamanship of the skippers, but we each make our own decisions on our own boats.

Consider:  In an anchorage with some boats lit and others not, at night while you are asleep, some power boaters comes screaming through too fast to be considered "really in control," do you want to be below asleep on one of the lit boats or one that is not showing an anchor light?

Your call.

[CharlieJ]

Quote-

I'm not seeing them used all the time. The way you can tell if the boat will turn an anchor light on is how expensive it was.

end quote

Quote-

Doesn't have anything to do with how expensive the boat is.  The law does not say "only expensive boats have to show proper lights."

End quote.

For sure- I've been sailing a restored 21 foot trailer boat and I would no way anchor without showing an anchor light, than if I was on a gold plated 50 footer.

DON'T leave port without it

[northoceanbeach]

Alright. I think the idea about rechargeable batteries might be the way to go. I haven't use rechargeable a in forever. When I was a kid they weren't very good.  I remember putting them in my Walkman and they wouldn't last at all buy I've got a feeling they've gotten better.