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Answer by Dan
Conrad, if this were me looking, I would want a panel with a 12 volt, 2amp/hour output.

You might be able to get by with less, depending on how much sunshine you get where you are, and how much your bilge pump draws.

Regards,
Dan

Answer by hot rod
You also want to have overcharge protection on the battery in case of constant full sun. What this will do is sense when there is enough charge and shut down the panel, while turning the panel back on when charge is needed.

Answer by Audio God™
Hi Conrad

Assuming your bilge pump draws about 2.6 amps, I’d recommend using a solar panel with an output of 5 to 5.5 watts. (They’re on sale here in Canada a few times a year for about $ 50)

These provide 0.3 amps/hour which will easily maintain your battery charge and will not require a charger limiter.

Hope this helps.

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Answer by Sean
rechargeable AA baterys do not realy last that long and if u dont fully discharge b4 fully charging u can shorten the amount of life the battery has even more

Answer by J S
87% of the charge is not very much. A good 12V battery will actually read 14V when charged, and stay at that level for a long time. By the time it shows 10V or so, it’s probably nearly 80% drained.

Answer by roderick_young
Two thoughts, which might or might not be right.

The panel might not be putting out as much power as you think. Most likely, the panel is just out there in one orientation, not following the sun. If it’s just basically the panel wired directly to the battery, then I suspect the charging current is actually quite small. You could verify this by connecting an ammeter in place of the battery.

My second thought is that whatever is indicating the say of charge on the battery is not at all accurate.

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Answer by Roushfan5
Why would you? Thats what the alternator is for. Unless you could generate enough power to get rid of your alternator (and I doubt you could) there would be no point.

Answer by tod m
doubtful
a regulator controls over or undercharging.

Answer by wildmanny2
Yes,but it requires a easy blocking diode to prevent the current from flowing in reverse when the panel is not producing.

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I guess I need some device I can hook the alligator clamps to that has a 115V plug on the other end I can plug the battery charger into?

Is there more to it than that?

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Answer by gintable
You need a device called an MPPT charge controller. A device that monitors the electrical characteristics of the PV module, and then regulates the output voltage to the battery bank.

MPPT = maximum power point tracking. It is a technology that adjusts the electrical load on the PV module, so that the PV module can always output all electrical energy that it generates.

You can get away with a non-MPPT charge controller, but you will waste a lot of energy. I.e. just a easy diode that regulates voltage to remain below a certain value.

You probably DON’T want the AC charge controller that comes with it. That is specially designed to handle AC signals. The native output of PV modules is a DC signal…but there is a dynamic behavior to the PV module due to varying cell temperature and varying sun irradiance as the day progresses.

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Answer by Gryphon Noir
Look up Electroveya. They build batteries for laptops and are currently working on building an electric car. They might be able to help you.

Shares in the company are cheap, and will very likely make you a bit of cash in the future. Check out EFL on the TSX. Purchase and hold.

Answer by electricpole
Industrial deep cycle batteries should work correctly in that application. Electric Forklift batteries can last for 10 years or more. Deep cycle batteries have a different plate structure than automotive ones. They do not need to produce massive amounts of of current in a short amount of time, but are made for a steady, known amperage. An important point is that one does not drain them past 1/2 their Ah (Ampere Hour ) capacity prior to recharging. Battery manufacturers have technical data that gives metrics on the Ah rating, reserve capacity, and # of cycles of recharging a battery will take,

Answer by ldunbarl
There are some additional energy storage possibilities working towards being cost effective for off grid uses. In 1999, I obtained a device called an electric double layer capacitor, it looked very promising back in the day, and since 10 years has elapsed, I believe the cost of the devices are falling into the reach of many consumers. There are disposal issues for SOME double layer capacitor designs, whereas popular lead-acid batteries are not only very HEAVY in weight, they also have to be disposed of correctly, unlike the balance of double layer capacitors. According to one manufacturer (nesscap: http://www.nesscap.com/products_advantages.htm ), the double layer capacitor should last 25 times longer versus a battery (they do not mention which kind of battery, though).

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I checked all the wires and I connected it correctly…

Thax

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Answer by Øyvind
Polarities in the turbine might have swapped places, turning it into a motor. Not sure how that would happen.

Answer by FirstnameL
Looks like the power is reaching the turbine turning it into a motor. Something might be broken.

Answer by Bill M
If you are using a DC generator, you need a rectifier to keep current from flowing from the battery to the generator.

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Answer by Robin
Yes, not sure why you’d want to but it can be done.

Depends a lot on how it is wired. If for example you exceed the voltage/current charge limit on the battery at ideal the electrolytic (likely an acid) will boil releasing a poisons flammable gas. Worst case has explosions…

The systems can be wired as to not interfere with each other or exceed battery limits. For example high end new RV’s mix solar and alternator charging.

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Answer by Wordward Nerdlinger
As long as it has the proper voltage and sufficient current.

Current is current – no matter the source.

When you shop, check the specs (in comparison to the battery specs) and ask the sales engineers about your intended use.

Answer by Ivy Vine
Definitely! This is being done all the time, for instance, automatic radio equipment in remote locations, such as mountain tops.

You need a solar panel which produces enough current to keep the battery charged even if you have a couple of cloudy days. You will also want a charge controller to prevent overcharging the battery. These devices monitor the charge on the battery, and disconnect the battery from the solar panel to prevent damage to the battery.

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Answer by texasmaverick
You will need a blocking diode in the wire from each device before they are connected together.

This will not be perfect, but it will work as long as the solar panel ‘s output voltage is greater than the battery’s voltage.

Another option, is to place a DPDT contactor (relay) in the solar panel’s output circuit., Connect the motor to the common terminals of the contactor , connect the battery to the normally-closed terminals of the contactor and connect the solar panel to the normally-open terminals of the contactor. The coil of the contactor will be connected to the solar panel. As long as there is voltage being produced by the panel, the contactor will be energized and the motor running off the panel. If there is no voltage (enough to energize the contactor0 the motor will be running off the battery.

EDIT
Forgot to tell you that a blocking diode must be installed in the line between the solar panel an the point where you connect to the contactor coil. This is to prevent the battery from enrgizing the coil.

TexMav

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Thank you!
I would need to charge it in 6 to 8 hours

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Answer by billrussell42
The missing factor is time. If you want to charge it in an hour or so, you need a much larger panel than you would need if you could wait for 2 days.

Also, batteries are not rated in amps or mA, they are rated in amp-hours or mA-hours. Assuming this is 400 mA-hours.

Disregarding losses, if you want to charge it in 4 hours, you need:
400 mA-hours / 4 hours = 100 mA

100 mA at 4 volts is 500 mW, so that is the power level you need. To counter losses, you probably need a 1 watt unit capable of 4 volts open circuit.

.

Answer by Vikkor
Your battery capacity is 3.5 Volts * 0.4 Ampere-hours = 1.4 Watt-hours.

Assuming a charging efficiency of 66%, the charger will consume 1.4/0.66= 2.12 Watt-hours

You want to charge it in 6-8 h, so you need a panel that provides between 2.12/8=0.265W and 2.12/6=0.35W.

You could just purchase a panel that is rated around that power, but if you actually want to estimate the surface,

5.5kWh/m2/day = 687.5 W/m2 (assuming 8 hours of strong daylight)

Current solar panels have an efficiency around 15%, so

Area = Power / Radiation / efficiency = 0.35/687.5/0.15 = 0.0034 m2 = 34 cm2 (approx 6×6 cm)

It’s kinda small, but it’s a small battery too.

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