Solar Charging of Wet Cell Batteries.

[skip1930]

Word to the wise...the battery is being charged all day long, everyday under the hot sun so you can have something for the weekend.

Check under the battery caps to MAKE SURE your not boiling the water away. [ breaking down the H20 with electricity into gases ] This lowers the water level in the cells exposing the plates to air, which must be kept wet. I did this back in 2010. Trashed a good battery by exposing the plates to air. She was making about 8 to 9 volts with what was left of the chemical reaction's ability after being over cooked. The solar cell was making about 18 volts DC and about 300 milliamps. Unregulated.

Note: A battery does not 'Store a Thing', even though some call it a storage battery. It's a instant chemical reaction that occurs when a circuit is completed. And far more energy is needed to replenish the battery than was ever used from the battery. Save every electron you can.

I'm using one 75 amp hour deep cycle battery and monitoring the water on my CP-19 as the solar cell continues to trickle charge and cook my battery.

skip.

[Salty19]

We've talked about this before.  You need a charge controller to limit damage. Much cheaper than new batteries and a whole lot safer.  Do yourself a favor and get one

[Shawn]

http://www.emarineinc.com/products/SunGuard-SG4.5--4.5A%7B47%7D12V-charge-controller.html

and even a few dollars less on Amazon. This is for a full PWM controller, not just a diverter.

Shawn

[wes]

I quit using a solar charger altogether after much web research about the potential damage to batteries. Since I mostly just use my depth sounder, plus GPS occasionally when I'm at the coast, I get many daysails from a full charge on my 225 Ah battery. I've installed a smart on board charger and just plug it into dock power every few weeks. A couple of hours of charging takes care of it.

Wes

[Koinonia]

A good source for solar panels is wholesalesolar.com.  Thats where I got my 135 watt kyocera panel, also genasun.com sells great MPPT charge controllers thats are more efficiant than the competition.  Ive got this setup with a victron energy battery monitor so I can see exactly whats getting used.  This setup is alot bigger than currently being discused but the rules are still the same.  When staying on the boat we have the refrigeration running, 12v box fan to help keep comfortable running all night while sleeping, watching movies on the tv, anchor light and other cabin light usage and will use anywhere from 25 to 35ah through the evening and night.  My batteries are usually fully charged by 11am unless there is total cloud cover.  Even with cloud cover I dont have to worry a bit about having enough power, during the day in south FL on vacation it was raining every afternoon so when we would leave the boat the only open spot was the companionway.  I would leave the box fan running to get that cooler outside air in the boat just in case it rained which it usually did.  If we spend a month in the bahamas in a couple years I may put a watermaker on the boat as well and run it during the peak hours of the day when there is more than ample extra power not being used to keep the water tank full and not have to be so anal about water usage.  Other than vacations on the boat the club where shes docked the rest of the time doesnt have power so its nice to have cold drinks on the boat at all times and not have to worry.  To think how far solar energy has come and its only getting better, and cheaper to.

[Shawn]

"A good source for solar panels is wholesalesolar.com.  Thats where I got my 135 watt kyocera panel"

Wow, that is a good price on that panel. How do you have the 135 mounted?

I have the Kyocera 40w panel on my companionway hatch with a Sunkeeper charge controller.

Shawn

[Koinonia]

Its on top of my bimini behind the split backstay to get maximum unshaded sun.  I may fabricate some a new davit setup off the stern for the dingy, If I do it I will relocate the panel on top of the davits.  Id like them to be a good height but still be under 13.6ft from the road while on the trailer. 

[skip1930]

So I took some readings after work from the solar cell working on my boat yesterday.

Battery charge was 12.46 to 12.47 volts with solar panel hooked up. Of course I'm reading battery voltage as the solar cell is diode protected. Juice running from solar cell to battery and not from battery to solar cell. The reading was taken down stream of the diode pak.

When disconnected the solar cell was making 15.79 to 15.80 volts D/C.

And the solar cell was making 0.01 amps. Which is a higher amp reading than I expected. [I was looking for 300 miliamps].

The cell mounts on cane tips, for air circulation under it, right over the forward hatch on my CP-19.

I wounder if this is worth it?

skip.

[wes]

Skip - 300 mA is 0.3 amps. Your actual reading of 0.01 amps is 10 mA, so was much lower than expected. Assume you put the ammeter in series with the battery and charger circuit so current could continue to flow.

Wes

[Allure2sail]

I was surprised to find that my batteries in my last boat would need distilled water every 3 or four weeks. Was not savvy enough to put a controllers on them (two panels). I do now!!! I have a switch where I can switch the panel back and forth from starting to house and they get switched every couple of days. I have one panel for the battery mounted up front on the cabin roof for the windless (isolated from other the other two batteries) and only plug it in for a few days after I use the windless. It is mounted on the starboard side in a battery box under the vburth. One other thing I found noteworthy was the voltage output from the two different brand controllers I use was that they vary on output voltage by up to.4 to .5 volts. One does 12.8 volts and the other one does about 13.2. Don't know why, I switched the panels and got the same numbers so it is not the panel. One came from West Marine (small yellow box) and the other one came from Defender (rectangular blue box). I would have to go put a meter on them to see which one was which. Like the other posts said KEEP THEM FULL OF WATER, I keep a two quart bottle of distilled water (three batteries to monitor) on the boat. I actually disconnected the on board charger when I cleaned up some wiring issues in the engine compartment this season. The panels work out so well I don't need it, I am in a slip but the panels work fine for me.

[Shawn]

"One does 12.8 volts and the other one does about 13.2. Don't know why,"

May simply just be where they have their float voltage set to. Can you adjust the controls for the type of chemistry in the battery? That should change the charge and float voltages.

Shawn

[Salty19]

There is your problem skip.  15.7 volt output is too much.   Amps are fine but volts are too high.

Each type of battery (lead acid, AGM, Lithion Ion, LiFe, etc) all require different charge rates.  Thus why the charge controller needs to be either made for the battery type or can sense and adapt to the type of battery installed.

It's likely you need around 13.7 volts for your lead acid battery..and no more than this... as a charging rate.  Less..probably 13.1 or so as the battery reaches close to capacity, then about 12.7v or so to float/maintain it.  Most modern charges do exactly this.  Note these figures are from memory so may be off a bit. Driving a constant (during daylight hours) 15.7 volts is the reason for the battery cooking.

Yep, a charge controller is indeed wise to have if you're charging onboard with solar, drag prop, wind prop, etc.

I just carry my battery home every 2-3 months to charge it.  LED nav and cabin lighting, and the occasional cell phone charging just don't draw much power.  then it sits on the battery tender all winter long.

Reminds that I need to check the voltage of the battery to make sure I shoulnd't be charging it more frequently.

[skip1930]

" It's likely you need around 13.7 volts for your lead acid battery..and no more than this... as a charging rate.  Less..probably 13.1 or so as the battery reaches close to capacity, then about 12.7v or so to float/maintain it.  Most modern charges do exactly this.  Note these figures are from memory so may be off a bit. Driving a constant (during daylight hours) 15.7 volts is the reason for the battery cooking. "

That cooks it! Dab nab it all anyway. No solar cell for me. Off she comes. I ain't got the $20+ bucks to spend controlling the volts on my boat.

skip. And thank you very much again...I'm just dumb as a box of rocks.

[Salty19]

Skip--On the contrary my friend...you may not know batteries but your knowledge in other areas more than makes up for it.

[wes]

Salty and Skip -

Skip reported the 15.7 volt measurement at the output of the solar cell, with no battery connected. This is an open circuit measurement and I would not consider it reliable. All voltage sources will tend to float high when they are unloaded. With the battery load connected, he measured less than 13 volts which seems normal to me.

Wes