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Old 18-06-2010, 10:44   #1
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Solar Battery Charging

Ahoy All,

Devante's Dream (a Jeanneau 40.3) has spent most of her life at dock (and on shore power) but now she's transitioning to mooring ball and cruising hook. When on the mooring ball unattended I want to make sure the batteries stay charged to run the bilge.

For normal charging of the 400AH AGM batteries I have an EntecWest 4.2Kw generator and a Xantrex Freedom Marine battery charger/inverter along with the engine alternator.

The boat is checked regularly and the genset and engine run so the batteries are charged during this process. Still, I am considering having either a top off or trickle solar charger to make sure they stay up between checks.

My current needs are quite low as far as I can see. The bilge runs for like two seconds maybe 5-10 times per day plus the normal static drain on the batteries.

I'd like to get some recommendations on solar chargers and how they would be hooked up. Can they go into my Xantrex?

Thx,

Eric
S/V Devante's Dream
Lying Marblehead MA
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Old 18-06-2010, 10:59   #2
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you would need a separate charge controller.
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Old 18-06-2010, 12:43   #3
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Elangley, One good solar panel would probably cover that. Mine go from the panels to a voltage regulator suitable sized to cover the amps, a circuit breaker, a charge controller, then to the bank...My Xantrex measures in and out on the battery so I didn't need to do anything with it to get the solar panels performance on it. Depends a little on the size of the bilge pump and the draw. You probably want to find that out before guessing on the solar panels.

Secondly, It seems a bit wrong that your bilge pumps run so often. You must have some good leaks there or flow back down the bilge drainage pipe. Have you tried mounting the auto bilge switch a little higher. It sounds like the float may be getting activated by the rolling of the boat or at just small amounts of water in the bilge. If its a leak and you have a big bilge pump you probably should find the leak and stop it in case the bilge pump ever fails.
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Old 21-06-2010, 13:45   #4
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Originally Posted by sailingaway221 View Post
Secondly, It seems a bit wrong that your bilge pumps run so often. You must have some good leaks there or flow back down the bilge drainage pipe. Have you tried mounting the auto bilge switch a little higher. It sounds like the float may be getting activated by the rolling of the boat or at just small amounts of water in the bilge. If its a leak and you have a big bilge pump you probably should find the leak and stop it in case the bilge pump ever fails.
Sailingaway, I should clarify that. My reefer drains into the bilge. When I'm on board I keep ice in it that drains regularly, so, the bilge runs more than normal. When I'm not onboard it does not run as much.

One concern I have is hooking up two charging devices to the batteries. Would there need to be any kind of switching device?

Eric
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Old 21-06-2010, 20:59   #5
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Eric-
Usually a shore charger and laternaotr co-exist very nicely since only one or the other is "talking" and charging the batteries at any given time. In theory each one has a voltage sense lead that tells it the voltage level at the battery and there's no conflict since only one is working at any time. Usually.
If both were running at the same time, the question becomes which one is really putting out power? And what is the voltage sense lead really detecting, battery level or the power from the other device? And that's where the problem can come with solar, if the solar panels are putting out power, unregulated, it is often higher than battery voltage.
If the batteries are depleted and really soaking up all they can, they'll eat up that extra voltage and the voltage sense lead from your alternator (or shore charger) will still get a reasonably accurate reading. As they get nearer a full charge...the voltage sense lead can't tell the difference between the voltage coming form the solar panel, and the voltage in the battery, so there's no way to predict whether it will reduce the output (from the alternator or the charger) too much and just waste your charging time.

Far simpler to add a 2-way switch, and leave the solar panel connected for maintenance charging on the hook, while using JUST the alternator or charger at other times.

If your solar panel is only putting out a small charge (i.e., "trickle" chrging) then it needs no controller, the battery can tolerate a certain amount of uncontrolled charging. If the solar panel puts out a relatively high charge rate, you'd be better off with a charge controller on it. Since AGMs can be killed by overcharging, you might want to check the maker's specs to see just how much of an uncontrolled charge they can take without damage. Or, just get the controller to be on the safe side.

"My reefer drains into the bilge. " That's nasty either way. You might consider putting a blivet in the bilge, most restaurants and diners will gladly give you an empty five gallon "mlik bag" from their milk machines, once rinsed out if makes a good way to trap and store five gallons of drain water that you can pour out manually when you get aboard. Or of course you can spend a lot more to buy a Nauta bladder.<G>
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Old 21-06-2010, 21:59   #6
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Eric-

Far simpler to add a 2-way switch, and leave the solar panel connected for maintenance charging on the hook, while using JUST the alternator or charger at other times.

...get the controller to be on the safe side.

"My reefer drains into the bilge. " That's nasty either way. You might consider putting a blivet in the bilge, most restaurants and diners will gladly give you an empty five gallon "mlik bag" from their milk machines, once rinsed out if makes a good way to trap and store five gallons of drain water that you can pour out manually when you get aboard. Or of course you can spend a lot more to buy a Nauta bladder.<G>
hellosailor, Thanks, I think the switch is logical. You can't turn the sun off. Of course I suppose I could just put a switch in the line of the solar panel. If it's off it won't charge, regardless of what the shore power input to the Xantrex is. A controller is logical as well.

I haven't decided between a full panel or just a trickle charge panel. I have room for a full and the extra juice wouldn't hurt. I wouldn't have to run the genset as much I suppose.

Also like the idea about the bladder for the reefer. It is annoying to have the bilge run just for that.

So, if I am to get a small solar panel and controller what manufacturers and models will I be looking at?

Thx again,

Eric
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Old 21-06-2010, 22:49   #7
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We're in the same situation... 4.5Kw Generator and want to add a 135Watt Solar Panel for our 950Ah AGM battery bank.Wouldn't diodes do the trick for the current trying to go "backwards" if the generator or main motor (with high out put alternator) are running?
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Old 22-06-2010, 12:35   #8
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Eric-
"I suppose I could just put a switch in the line of the solar panel. " Yes, but that allows you (or some helpful crew) to forget or throw the switch the wrong way, as opposed to an "A or B" switch that ensures both can't be connected at once.
I'm firmly in favor of idiot-proofing at the hardware level whenever I can. I seem to remember saying "Did I really just do that?" at least once.<G>

Don't know which brands to recommend, models keep changing, prices keep changing...I'd say to do a web search and see what's most effective for you, then check out the rep, warranty and track record from the vendor. Make sure the panels are warranteed for marine usage, some have dropped that because salt air and salt water are kinda rough on panels.
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Old 19-07-2010, 10:50   #9
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Eric,

A non-MMPT charge controller is very cheap, and it will provide the correct voltages and amperage for different charge stages. It will automatically shut off when the battery bus voltage exceeds around 14 volts (ie, when the alternator or genset are providing power). No switch required.
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