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Old 11-06-2014, 17:15   #1
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Back-Up Solar Charger?

Any recommendations for a back-up solar charger? I'm not expecting to run a blender for rum drinks, strictly a back-up way to put some juice in the batteries when there is no other option.

Flexible seems like the way to go. I've done a little looking around and there are a lot of options in the marketplace these days.

Unfortunately, it seems like the ones I might want are a little more than I would want to spend, while the ones in my price range seem a little dubious as to their origin and quality. Any advice appreciated.

Cheers!
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Old 11-06-2014, 19:12   #2
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Re: Back-Up Solar Charger?

Couple questions, in the interim. First, what budget are you trying to stay within, and also, how much charging are you anticipating? Are you looking for something to keep your batteries topped when you aren't on board? Or is it for more when you're out and about and all else has failed? What charging methods do you currently have/use?
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Old 12-06-2014, 05:45   #3
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Re: Back-Up Solar Charger?

The goal would be to provide an all-else-fails method to produce at least SOME power when offshore, if that comes with a battery-topping-off then that's a bonus that would be appreciated. $75 for a 5w panel with a 5w controller works for my budget, +$200 for 15w panel not including a controller not so much.

Problem is identifying a decent quality cheapy, but maybe it's not even worth it to buy a cheap one. I just don't know. Hence my asking.
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Old 12-06-2014, 06:08   #4
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Re: Back-Up Solar Charger?

5W is going to produce ~0.3A. Is this going to be useful? It won't run any instruments, etc if the batteries are low. It won't provide any significant charging of a battery either.

Since you only plan to use this as a backup/emergency, and you will have a very small panel, you will not need a controller. Put any money saved on that into a larger panel.

Frankly, I think you will need a minimum of a 50W panel to have any practical impact.

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Old 12-06-2014, 06:18   #5
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Re: Back-Up Solar Charger?

What I am thinking is ten days out with ten days to go the diesel dies and can't be revived.

Plenty of back-up hand held GPS's and vhf radios, but might be nice to nice to have a way to put some juice back in the house bank to run the nav lights and ship's radio for when you get closer to land and encounter more traffic.

The boat is pretty no-frills without a lot of doodads so the electrical requirements are pretty minimal as it is. I can think of worst things than not having power but maybe 5w is better than none at all?
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Old 12-06-2014, 08:26   #6
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Re: Back-Up Solar Charger?

Like I said, 5W will produce ~0.3A for the 6-8hrs each day of good light you would get on it. That comes out to replacing at most 2.4Ahr/day into your batteries.

Assuming you have zero draw on your battery bank for 10 days, then (ignoring any self-discharge and charging inefficiencies), you would have recovered ~24Ahr at most for when you close land.

This would give you one day of a 1A draw to run lights, etc. If you are using the radio, it will be considerably less time.

If you experienced any cloudy days, or cannot deploy the panel because of conditions, things go south very quickly with the numbers.

Personally, I don't think a 5W panel will make any practical difference in your scenario. Particularly when you need to balance the careful storage of it.

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Old 12-06-2014, 08:37   #7
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Re: Back-Up Solar Charger?

Comments appreciated. Not my area of expertise.

For the couple hundred bucks you would spend on a 15w flexible it sounds like a better approach would be to fit a legit 50w set-up that would actually do something for probably not much more money. The boat's owner is a bit anti-techno so there is not a lot of demand up front.

That said, 5w would get you a charge on a cell phone, or a hand held VHF? Maybe that's worth something.
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Old 12-06-2014, 08:45   #8
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Re: Back-Up Solar Charger?

Quote:
Originally Posted by Delancey View Post
That said, 5w would get you a charge on a cell phone, or a hand held VHF? Maybe that's worth something.
I think they sell little fold up ones just for this purpose (cell phones yes, but maybe not VHF).

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Old 15-06-2014, 13:13   #9
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Re: Back-Up Solar Charger?

I bought one of these yesterday to use for camping.

Guide 10 Plus Adventure Kit - V2 - GOAL ZERO Portable Solar Power - Canada

charge you phone or aa,aaa batteries. so you can charge your cell phone via usp, hand held gps batteries, might be a vhf adapter to take AA,s in your hand held? then you could charge those. it does have a 12v output too you can connect to boats batteries but 7w won't do much.
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Old 15-06-2014, 14:55   #10
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Re: Back-Up Solar Charger?

I'm with Mark. I don't think 5W would keep your nav lights or VHF going for long even if you had full sunlight all day. And any controller on a 5W panel would be a waste in that scenario.

Get the pencil out, add up what the nav lights and radio and one cabin light or the helm compass will need and buy enough panel to supply twice that much, as a minimum.

If that's too expensive just buy a cheap spare battery and disconnect it after charging every fortnight.

But if you're buying solar and looking for cheap, that probably means Chinese solar and if you're going to buy it in the US? Buy it now, Congress just added a 30% tariff.
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Old 15-06-2014, 18:53   #11
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Re: Back-Up Solar Charger?

Quote:
Originally Posted by Delancey View Post
What I am thinking is ten days out with ten days to go the diesel dies and can't be revived.

Plenty of back-up hand held GPS's and vhf radios, but might be nice to nice to have a way to put some juice back in the house bank to run the nav lights and ship's radio for when you get closer to land and encounter more traffic.

The boat is pretty no-frills without a lot of doodads so the electrical requirements are pretty minimal as it is. I can think of worst things than not having power but maybe 5w is better than none at all?
So the problem given is to run "minimal" systems when your current diesel based alternator can't be used.

Again it starts with what you consider essential systems and living with a very tight energy budget.

Nav lights, cabin lights(?) - what about navigation? Are you a paper guy or do you have an electronic plotter? Or is it an iPad or laptop. Autopilot? Who steers at night?

The lights are a big energy hog - LED can help but 3 lights at 40W is an amp X 10 hours is 10 amps a day.

4 hours of cabin light at 2 amps = 8 amps

The radio is probably an amp on stand by and 3-5 when transmitting. It is light duty, can be left off unless needed. So call it an amp a day as an average?

Let's figure 10 amps to charge iPads laptops etc.

If there is an autopilot that steers at night you need a couple amps X 10

So 38-40 amps in minimalist mode.

40 X 12 = 480W / by useful sunlight (8 hours) / efficiency 80% = You need a minimum of 75W panel

You also need a battery bank of at least 80 a/h.

My diesel engine died and is waiting for me to overhaul it. I bought 2 X 15 W panels. Similar to these

RDK PRODUCTS 15W Semi-Flexible Monocrystalline Solar Panel | West Marine

But rigid. I bought them because the would fit on each side of my backstay on top of the bimini. I just zip tied them on wired in parallel with no controller. I have never measured their amp output (only voltage after install) but I expect I am getting a couple amps X 8 hours = 16 amps a day.

I have 210 a/h battery bank. I run lights, Otto, stereo etc. all weekend and then the panels charge the bank up during the week. Late in a 3-day weekend if I have been relying on Otto a lot I will get low voltage and know have over-discharged my battery bank.

It would not keep up with me on a daily basis.
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Old 16-06-2014, 06:09   #12
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Re: Back-Up Solar Charger?

Heres a quick and dirty energy budget, some details might be wrong, happy to discuss usage, but its close enough to get a feel for what wattage panel is a minimum. They Assume portable panels that can be roughly aimed and kept clear of most shadowing.

Click image for larger version

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This is a good sunny day, just enough power to keep up with the basics

Click image for larger version

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Cloudy, starting to have to cut unneeded stuff out. Should be able to keep a battery from getting to badly down in very overcast conditions for a few days or recharge the battery slowly if using this profile on sunny days.

Not alot of slack, and 40 watts is about a minimum for basic battery life support on passage, as I have found works out ok for me over the years. It still takes a rigorous cutting of non essential systems, NO mfd's or other instruments, and no watching videos or autopilots. Needless to say any refrigeration is absolutely impossible to run with this sort of energy budget.
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Old 16-06-2014, 06:49   #13
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Re: Back-Up Solar Charger?

My suggestion go with a used 75 watt panel (to keep costs down) and a Morningstar Sunguard controller SunGuard ยป Morningstar Corporation . at a minimum. You don't really want to just depend on just a diesel engine do you when crossing the ocean.
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Old 16-06-2014, 06:53   #14
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Re: Back-Up Solar Charger?

I don't think he would need a controller at all - even for 75W. He only plans to use it as an emergency backup if all other charging goes south. No way 2-4A for 6-8hrs is going to overcharge a depleted battery bank.

For example, when lightning took out our solar controller, 120V charger and alternator, we connected our 480W of panels directly to our battery bank with no problem with overcharging.

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Old 17-06-2014, 12:13   #15
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Re: Back-Up Solar Charger?

Quote:
Originally Posted by Delancey View Post
Any recommendations for a back-up solar charger? I'm not expecting to run a blender for rum drinks, strictly a back-up way to put some juice in the batteries when there is no other option.

Flexible seems like the way to go. I've done a little looking around and there are a lot of options in the marketplace these days.

Unfortunately, it seems like the ones I might want are a little more than I would want to spend, while the ones in my price range seem a little dubious as to their origin and quality. Any advice appreciated.

Cheers!
Most likely outside the scope and cost of what you want, but I will through it around anyway.. No solar on our boat, installed a fuel cell instead.

For sailors with solar, a fuel cell would be a great augment to the solar (for backup, and for use at night or when the solar may break down). It would be way overkill for an emergency backup.

there is an ongoing thread here.
E FOY Fuel Cell Generator

But at several thousand dollars + fuel, it is likely not what you are looking for. It is way cool though
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