Solar Trickle Charger Question

[thinkbig]

Hi,

I am looking to purchase a solar trickle charger for the battery
in my boat. It is a 90 hp motor and I have a 12V car battery as
opposed to a marine battery (it came with the boat).

If I don't use the boat for several days to a week the battery gets
weak and needs to be recharged. It's a real pain running extension
cords outside to use my charger and also time consuming waiting for
it to recharge. I'm hoping to find something that will maintain it.

I have been looking at them on amazon.com and noticed that most
of them come with a cigarette liter plug?? This is throwing me off
because the way I understand it is that the charger would hook up
directly to the battery, get the energy from the sun and feed it
directly to the battery, so why would they come with lighter plugs?

Is there anything else I would need to hook up besides the charger
to the battery? I also noticed that they come in different amp
strengths??

I know practically nothing about this, so any help would be appreciated (-:

If anyone can recommend one on Amazon or anywhere else online,
that would be great.

Thanks in advance for your help!!

[thastinger]

Is there some drain on the battery? Do you have a battery disconnect switch? The bilge pump is wired directly to the battery so if the boat has a small leak and sits in the water, the bilge pump may be drawing the battery down between uses.

Just trying to save you some money as you shouldn't need to continually charge a boat battery like that. Either the battery is on it's last leg or you have a draw on it.

Trickle charging is different than recharging. The conditions you describe is recharging which would take more panel. Do you know the amp hour capacity of the battery or can you break it down to percent drain per day on the battery? To get the proper size panel you're going to need to know how much you need to put back in it IOT keep it charged.

[SunEagle]

Given he mentioned it was a "car" battery I would say it is having trouble holding a charge or may not be getting fully charged when he is running his boat.

[thinkbig]

Thanks for your responses.

The battery is only 2 years old, so I hope it's not on it's last legs.
If it is, there is probably some time left on the warranty. I'll have
to check.

To me , it does sound like there is something draining it, but I've
checked everything I know of (pretty much the light panels) and they
are off. The bilge pump is manual so it only goes on when I flip
the switch. I don't have a battery cut off switch, but that may be
a good solution.

"Do you know the amp hour capacity of the battery or can you break it down to percent drain per day on the battery?"

No , and am not sure to figure that out. If I use they boat every
day or even every other day the battery is fine. It only drains
after several days to a week.


These (below) are some of the solar chargers I've been looking at.
The 1st one is the only one that says it is weatherproof for use outside
(not sure about the others), and says it is for 12V batteries, but mentions
nothing about car batteries.

The prices are very reasonable so if it works it will be well worth it.

Thanks again!!!


http://www.amazon.com/gp/product/B00...=ATVPDKIKX0DER


http://www.amazon.com/NPower-Amorpho...attery+charger

http://www.amazon.com/Battery-Charge...attery+charger

http://www.amazon.com/6-Watt-Solar-B...attery+charger

[thastinger]

None of those are going to work for what you describe. Lets use some generalities to get you in the ballpark. Typical deep cycle marine batteries are usually around 100Ah battery, if you drain it in 3 days then lets say that is a 33% needed input per day. That is going to put you at about a 100W panel via a PWM charge controller because you're not talking about "trickle" charging the battery. You are talking about RECHARGING the battery.

I would have the battery tested. Once you have a known good battery, get a battery disconnect. Both of those will be far less expensive than recharging your battery from a PV panel.

[SunEagle]

[QUOTE=thinkbig;78188]Thanks for your responses.

The battery is only 2 years old, so I hope it's not on it's last legs.
If it is, there is probably some time left on the warranty. I'll have
to check.

To me , it does sound like there is something draining it, but I've
checked everything I know of (pretty much the light panels) and they
are off. The bilge pump is manual so it only goes on when I flip
the switch. I don't have a battery cut off switch, but that may be
a good solution.

Most car batteries in good condition can sit there for weeks without draining to the point of not being able to start the car.

When a battery drains quickly it is because of some "load" that is connected (like a dome light or radio). Or the battery is no longer in a condition that it can hold its "no load" charge for any time.

Get the battery checked out and look for a way to disconnect it when it is not in use. A battery cut off switch is less than $10 and will save you the headache of recharging after a few days of just sitting there.

[thinkbig]

Great, thanks, will do.

There has to be something draining it so the cutoff switch should stop it.

Is this what you are recommending or similar?

http://www.amazon.com/BATTERY-CUTOFF...cut+off+switch

Thanks again!!

[thastinger]

http://www.amazon.com/Perko-8501DP-M...battery+switch

This is what my boat has. My boat also has 2 batteries so you can use this switch to switch/start/charge them in any configuration that works for you. This one is nice because all of the connections are within the case and it is designed to be bulkhead flush mounted.

[thinkbig]

Thanks.

[PNjunction]

When used with a typical car/marine battery, those dinky little solar panels are more accurately called "maintainers", and only serve to to help compensate for self-discharge. You want to start out with a *fully* charged battery, otherwise, you'll just be maintaining it at the state of charge that the panel found it.

Yes, legally they do "charge", but not of any consequence in the real world with a large battery. Use a 5ah agm alarm battery, and it will be more of a real charger.

Since the current they are capable of providing is well below the C/100 range, most don't even need a charge controller.

Your best bet would be to get a quality automotive charger to make SURE your battery is doing the best it can before storage with the dinky solar maintainer. Note that there are ac powered "maintainers" as well, which sure enough do the same thing - maintain your battery *AFTER* a full charge with a higher-powered charger.

Yes, if you wait 3 or 4 days, those "maintainers" might put enough charge back into a battery eventually but it is not healthy for the battery to be charged at under the typical C/12 minimum rate. In other words, choose the right tool for the right job - a C/12 minimum charger for charging, and a maintainer for maintaining.

[thinkbig]

I do have a charger that charges at 10 Amp or 2 Amp and has a 50 Amp jumpstart,
and that is what I've been using to recharge it. But, it does need to be done every
time the boat sits around for a few.

I was planning on using the solar charger to keep it maintained, but I do agree with
Thastinger "the battery is either on it's last leg or there is a draw on it."

But now thanks to everyone who replied, I have a few ideas on where to start.

I think the easiest way will be to charge it up and use the cutoff switch to stop
whatever may be draining it when not in use. If that doesn't work then it is
probably time for a new battery (-:

Thanks again for everyone's help!!

[PNjunction]

Sounds like a plan. By all means look for a parasitic draw, or do the total disconnect when not in use, and recharge often.

Be mindful of the C/100 rule. Many of the places that sell the little 12v solar maintainers, typically 5watt panels or less, also sell slightly larger panels like 15 watt versions along with some cheap controllers.

Example: On my 55ah (at the 20hr rate) battery, I would choose a panel that had less than a maximum of .55a (550ma) total output for use with no controller. If all your battery has is the "RC" or reserve capacity rating, multiply that RC * .6 to get an approximation of the 20hr rate.

BUT, if you cross that C/100 line, you are going to want a quality controller, and not the typical on/off ping-pong types that go with them. In other words, if I chose to put a larger 15 watt panel (about 800ma) on my 55ah battery, that is crossing the C/100 rate and I'll want a controller. Instead of the typical junk controller usually sold with them, choose something higher quality like the Morningstar SunGuard 4.5a. The charge controller is no place to go cheap.

AGM NOTE: Personally I wouldn't use a small panel without a *quality* controller on an AGM battery. The reason for this is that like most 12v nominal panels, they are actually rated near 18v ocv. Some agm manufacturers warn that even with very very low currents this high of a voltage will eventually blow the seals. The other factor not usually mentioned is that a high voltage even with low currents can lead to internal corrosion over time. Battery Tender solar maintainters have these built in, or you can DIY with Morningstar, etc.