New 10W Solar Panel. Question Regarding Wiring (with pictures)

[arf145]

bevansmith, if this is not an advertisement for the company you linked in there, you need to let us know, because it sure looks like one.

[asdf38]

Originally Posted by hellosailor

Small panel, big battery, no regulator or controller needed. Although knowing the exact capacity of the battery would help make that more specific.

Odds are the controller's output leads are so small because the controller is designed ot be used with a 10W solar panel, which can provide only about 3/4 amp of power at 12-14 volts. The controller has been built to work with a 750mA load, possibly something a little larger, and I'd bet it is not designed to operate with the larger loads on a boat.

I'd keep the load wires on the battery and even get rid of the controller unless you miraculously find the battery is being overcharged without it. (By voltmeter testing the battery.)

I'm going with this plan. I'm kicking myself for not planning for a good solar solution earlier in my re-wiring project and now, after reading a bit more about charging I realized that I really should have a panel. My boat is on a mooring and overall I don't use much power, but given that I only run the engine a few minutes per sail I'm probably never going to be above 80% charge. I didn't realize this and that my battery life will be extended if I can keep them closer to 100%.

Anyway I thought through a few options and decided that I'll simply buy a 5W panel, no controller (I may have been able to get away with 10 but some information I see is conflicting regarding the safety of not having a controller) and wire it into the lighter plug outlet in my cockpit. When I leave the boat I'll plug it in and leave it on the cockpit floor or seat and stow it when I'm sailing.

I'll run a diode protected and fused (at the battery) wire from the lighter plug directly to the house/main battery. The Bluesea charge relay should switch in the starter/reserve and top that off as well.

The lighter plug power is wired to the accessory switch on my electrical panel so as long as this switch is off the solar panel won't backfeed the electrical panel and any loads that are left on (like cabin lights). However it will power any device I leave in the other lighter plug outlet as that's on the same circuit (I could block this with another diode if I really wanted but it may be convenient to be able to flip this accessory switch and read out the solar voltage on the meter).

I'm going with this $20 panel and this diode
SB1245 Fairchild Semiconductor | SB1245CT-ND | DigiKey

Amazon.com: Instapark® 5W High-Efficiency Mono-Crystalline Solar Panel: Patio, Lawn & Garden

Amazon.com: Instapark® 5W High-Efficiency Mono-Crystalline Solar Panel: Patio, Lawn & Garden

[liveincolor]

Originally Posted by asdf38

I'm going with this plan. I'm kicking myself for not planning for a good solar solution earlier in my re-wiring project and now, after reading a bit more about charging I realized that I really should have a panel. My boat is on a mooring and overall I don't use much power, but given that I only run the engine a few minutes per sail I'm probably never going to be above 80% charge. I didn't realize this and that my battery life will be extended if I can keep them closer to 100%.

Anyway I thought through a few options and decided that I'll simply buy a 5W panel, no controller (I may have been able to get away with 10 but some information I see is conflicting regarding the safety of not having a controller) and wire it into the lighter plug outlet in my cockpit. When I leave the boat I'll plug it in and leave it on the cockpit floor or seat and stow it when I'm sailing.

I'll run a diode protected and fused (at the battery) wire from the lighter plug directly to the house/main battery. The Bluesea charge relay should switch in the starter/reserve and top that off as well.

The lighter plug power is wired to the accessory switch on my electrical panel so as long as this switch is off the solar panel won't backfeed the electrical panel and any loads that are left on (like cabin lights). However it will power any device I leave in the other lighter plug outlet as that's on the same circuit (I could block this with another diode if I really wanted but it may be convenient to be able to flip this accessory switch and read out the solar voltage on the meter).

I'm going with this $20 panel and this diode
SB1245 Fairchild Semiconductor | SB1245CT-ND | DigiKey
Amazon.com: Instapark® 5W High-Efficiency Mono-Crystalline Solar Panel: Patio, Lawn & Garden

Glad you revived this thread asdf. It's a year old, but now I can report on how that season went with my setup.

I left the 10W panel connected to the battery all summer, and I never had an overcharge problem. I got in the habit of checking the battery with a cheap analog voltmeter every evening and found the battery never to be over 13V. I used the battery lightly most days (cabin lights, cell phone charging, and a 180 watt inverter when I needed that). However, there were times of absence of 3-5 days and zero battery use (panel connected the whole time) and still never overcharged.

I did make an observation, when the panel was in the light I checked its voltage and got a 17-18 volt reading. I'm confident the battery was never overcharged, but isn't 17V powerful enough to overcharge a 12V battery ? Just curious why I never had a overcharge problem.

The only thing I would question about your plan is, you say that you have a lighter outlet in the cockpit ? Will it be exposed to rain while you're away ? I wouldn't want to leave the circuit compromised by using 12V lighter outlet if its out in the weather.

[Cruisingdad]

Ok, the output on most solar panels is betweeen 17-18 volts. This is an issue if you have a lot of amps associated with it. A good charge controller (esp MPPT) convert that 17v down to the maximum voltage to charge, and thereby increasing the amps. But the amps on your solar panels are so low, I suspect it is not worth the trouble.

The panel size you guys are talking about is nothing to worry about. I am actually surprised you are getting anything positive out of it at all (positive results). If you are, that is super! But I would suspect at best you will only be able to trickle charge the batts and keep them from self discharging as much.

Brian

[asdf38]

Originally Posted by liveincolor

did make an observation, when the panel was in the light I checked its voltage and got a 17-18 volt reading. I'm confident the battery was never overcharged, but isn't 17V powerful enough to overcharge a 12V battery ? Just curious why I never had a overcharge problem.

The only thing I would question about your plan is, you say that you have a lighter outlet in the cockpit ? Will it be exposed to rain while you're away ? I wouldn't want to leave the circuit compromised by using 12V lighter outlet if its out in the weather.

Well it's one thing to measure it open circuit but it's another if you're getting 17 at the battery or at a point electrically connected to the battery? Where exactly did you read it, before or after the controller?

Yes I question it too but I should only be risking the solar panel and outlet and given that it's a $20 panel I think that's ok. I'll put a 1A fuse on it and double check whether I think water could leak into the boat through the outlet.

Originally Posted by Cruisingdad

Ok, the output on most solar panels is betweeen 17-18 volts. This is an issue if you have a lot of amps associated with it.

Sorry to nitpick but statements like this are ambiguous and sometimes I think there is a misunderstanding behind them (not just you, I felt that way reading a lot of these threads). The reason it's ok to put an "18V" solar panel on a 12V battery is because the solar panel is a weak source and it can't actually sustain 18V. Compared to the panel the battery is a powerful load and yanks the voltage down to acceptable levels 13V-14V

If liveincolor is actually getting 17V at the battery I think that's a problem.

A trivia question: You have two circuits, A and B, with identical loads but different sources. One source is capable of 1A and the other 100A. You measure 15V on both loads. How much current is flowing:
A) The same amount of current
B) Depends how many amps the source is putting out

The answer is A (the exceptions are "smart" loads like an electronic device that might shut itself down, or something else that somehow retains a state)

[Maine Sail]

Originally Posted by asdf38

Sorry to nitpick but statements like this are ambiguous and sometimes I think there is a misunderstanding behind them (not just you, I felt that way reading a lot of these threads). The reason it's ok to put an "18V" solar panel on a 12V battery is because the solar panel is a weak source and it can't actually sustain 18V. Compared to the panel the battery is a powerful load and yanks the voltage down to acceptable levels 13V-14V

If liveincolor is actually getting 17V at the battery I think that's a problem.

A battery is only heavy load for a small panel when it is discharged. The over charging, voltage wise, occurs when the battery becomes full. With some batteries it can take less than .05A to maintain a 13.8V float. I have a battery on my bench right now for equalization and to see if it can be saved, it became out of balance with the other battery due to incorrect bank wiring practices. It has been floating a 0.04A of accepted charge current now for over three days, just 0.04A to maintain 13.6V.

On of the posters mentioned he checked the voltage in the evening and still found it into the 13's.. Into the 13's, after the sun is down, is quite high. A fully charged battery is about 12.7V. It is a surface charge really, but why that high many hours after the sun has likely stopped supplying any current? You certainly want to check battery voltage at peak sun..

A 10W panel is capable of about 0.6A which means it can still exceed the "full" acceptance of some batteries. The batteries on my bench are WM/Deka group 27.. Most of the advice that a small panel will not over charge a battery comes out of land based or automotive applications where there is already a small load... If the bank is large, usually not an issue, but who uses a 10W panel on a "large bank" unless trying to simply "maintain"..... Kind of like feeding Rosie O'Donnell a grain of rice and expecting her to feel full...

If the battery actually recharges to 100% with a 10W panel, has no load on it, and especially if AGM or GEL which have very low self discharge, it can cause a battery to reach gassing voltages. Yes the current may be low because the batteries won't accept any more current but this is when the voltage can rise to close to panel voltages. You may not get to 17 or 18 volts because voltage is pressure and increasing the pressure increases the amount of current the batteries will accept slightly.

Last year I connected a 105Ah deep cycle Deka battery to a 10W panel in my yard. The battery was full when connected. In full peak sun I was seeing 16.1V at the battery (measured with a Fluke DVM). This is well beyond a safe voltage for even a deep cycle wet cell and a voltage that would kill a gel cell and most AGM batteries if left to do it day in day out. If you actually use your boat then there would be no issues as the batts would always be drained enough that it would take next to eternity for the 10W panel to actually "re-charge" them enough to hit full..

Over night even a disconnected battery can discharge enough, especially in hot climates, that it can take a few hours the next day to hit gassing voltage again but it can happen and did in my small n=1 experiment...

I was invited up to a well known marine authors house today, by my friend Bruce, as they are conducting some very, very cool experiments with MPPT controllers vs. "cheap" controllers. The set up they built sounds VERY cool! We will likely see this article in Professional Boatbuilder or another mag soon enough. I am anxious to talk to Bruce to see how it went. I am just to busy to join them right now.

[liveincolor]

Originally Posted by Maine Sail

A battery is only heavy load for a small panel when it is discharged. The over charging, voltage wise, occurs when the battery becomes full. With some batteries it can take less than .05A to maintain a 13.8V float. I have a battery on my bench right now for equalization and to see if it can be saved, it became out of balance with the other battery due to incorrect bank wiring practices. It has been floating a 0.04A of accepted charge current now for over three days, just 0.04A to maintain 13.6V.

On of the posters mentioned he checked the voltage in the evening and still found it into the 13's.. Into the 13's, after the sun is down, is quite high. A fully charged battery is about 12.7V. It is a surface charge really, but why that high many hours after the sun has likely stopped supplying any current? You certainly want to check battery voltage at peak sun..

A 10W panel is capable of about 0.6A which means it can still exceed the "full" acceptance of some batteries. The batteries on my bench are WM/Deka group 27.. Most of the advice that a small panel will not over charge a battery comes out of land based or automotive applications where there is already a small load... If the bank is large, usually not an issue, but who uses a 10W panel on a "large bank" unless trying to simply "maintain"..... Kind of like feeding Rosie O'Donnell a grain of rice and expecting her to feel full...

If the battery actually recharges to 100% with a 10W panel, has no load on it, and especially if AGM or GEL which have very low self discharge, it can cause a battery to reach gassing voltages. Yes the current may be low because the batteries won't accept any more current but this is when the voltage can rise to close to panel voltages. You may not get to 17 or 18 volts because voltage is pressure and increasing the pressure increases the amount of current the batteries will accept slightly.

Last year I connected a 105Ah deep cycle Deka battery to a 10W panel in my yard. The battery was full when connected. In full peak sun I was seeing 16.1V at the battery (measured with a Fluke DVM). This is well beyond a safe voltage for even a deep cycle wet cell and a voltage that would kill a gel cell and most AGM batteries if left to do it day in day out. If you actually use your boat then there would be no issues as the batts would always be drained enough that it would take next to eternity for the 10W panel to actually "re-charge" them enough to hit full..

Over night even a disconnected battery can discharge enough, especially in hot climates, that it can take a few hours the next day to hit gassing voltage again but it can happen and did in my small n=1 experiment...

I was invited up to a well known marine authors house today, by my friend Bruce, as they are conducting some very, very cool experiments with MPPT controllers vs. "cheap" controllers. The set up they built sounds VERY cool! We will likely see this article in Professional Boatbuilder or another mag soon enough. I am anxious to talk to Bruce to see how it went. I am just to busy to join them right now.

Thank you Mainesail, good info in there. I was the one who mentioned checking the battery voltage every evening. Although the sun was not set, it certainly wasn't at its peak. I didn't make it a point to check voltage at peak hours because I wrongfully assumed that if the battery had overcharged during the day, it would be reflected by my evening voltage check. So you're saying the battery could have overcharged by day, then as the sun went down the battery discharged back down to give me an approx 13V reading in the evening ?
I will definitely make sure to check the battery voltage while the sun is at its peak to see if I'm overcharging my battery. Many posters here agreed that a 10W panel was not powerful enough to overcharge my 100ah battery, but if what you say is true about maintaining full charge with just .05 amps, then my panels rating of .6 amps should be more than enough to overcharge my battery. I will check my setup asap, and report back what I find.

[asdf38]

Originally Posted by liveincolor

Thank you Mainesail, good info in there. I was the one who mentioned checking the battery voltage every evening. Although the sun was not set, it certainly wasn't at its peak. I didn't make it a point to check voltage at peak hours because I wrongfully assumed that if the battery had overcharged during the day, it would be reflected by my evening voltage check. So you're saying the battery could have overcharged by day, then as the sun went down the battery discharged back down to give me an approx 13V reading in the evening ?
I will definitely make sure to check the battery voltage while the sun is at its peak to see if I'm overcharging my battery. Many posters here agreed that a 10W panel was not powerful enough to overcharge my 100ah battery, but if what you say is true about maintaining full charge with just .05 amps, then my panels rating of .6 amps should be more than enough to overcharge my battery. I will check my setup asap, and report back what I find.

FYI you're a bit past some of the numbers I've seen which is why I stuck with 5W for my ~150Ah total. Sounds like worst case you might just want to add a controller for peace of mind. Some reccomended ones are only about $20. I'll be monitoring my system to see if I think I need to do the same.

Charge Controllers for Solar Electric Systems

Not always, but usually. Generally, there is no need for a charge controller with the small maintenance, or trickle charge panels, such as the 1 to 5 watt panels. A rough rule is that if the panel puts out about 2 watts or less for each 50 battery amp-hours, then you don't need one.

For example, a standard flooded golf car battery is around 210 amp-hours. So to keep up a series pair of them (12 volts) just for maintenance or storage, you would want a panel that is around 4.2 watts. The popular 5 watt panels are close enough, and will not need a controller. If you are maintaining AGM deep cycle batteries, such as the Concorde Sun Xtender then you can use a smaller 2 to 2 watt panel.

I've also seen a number of 1/60, i.e. if your solar can put in 1/60th or less of the battery capacity per day (figured by using roughly 5 hours) you don't need a controller. 10W * 5 hours is ~4AH which says that 10W is only ok for 240AH banks or more without a controller.

[liveincolor]

Originally Posted by asdf38

FYI you're a bit past some of the numbers I've seen which is why I stuck with 5W for my ~150Ah total. Sounds like worst case you might just want to add a controller for peace of mind. Some reccomended ones are only about $20. I'll be monitoring my system to see if I think I need to do the same.

Charge Controllers for Solar Electric Systems


I've also seen a number of 1/60, i.e. if your solar can put in 1/60th or less of the battery capacity per day (figured by using roughly 5 hours) you don't need a controller. 10W * 5 hours is ~4AH which says that 10W is only ok for 240AH banks or more without a controller.

Yea, it seems as though I may have to make some changes to my setup. Now I'm a little anxious to get to my boat and check on it. Thanks for the link.

[Barquito]

A little thread drift question: Would it work to just use a panel indicator LED for the diode protection from a 5W solar panel?