Solar battery chargers

[That old Mercury]

Hi
I want to get a couple of solar chargers to charge my batteries after a fishing trip.
I keep my boat at a storage yard so i remove my batteries now and bring them home, sometimes i take two and charge them and just do a swap out but i am tired of doing that.
I have a selector switch so i run only one to have a fully charged backup and i want to charge them in boat seperately also.
Batteries 12vdc deep cell , acid .
I normally fish once a week to once every two weeks.
I want something large enough to charge them in less than a week.
Looking at everything i have read so far i think i need at least 150 watt solar panel because i want them to charge in the winter too.
Thanks for any input.

 

[alldodge]

@tpenfield

 

[wn6ngp]

Hi
I want to get a couple of solar chargers to charge my batteries after a fishing trip.
I keep my boat at a storage yard so i remove my batteries now and bring them home, sometimes i take two and charge them and just do a swap out but i am tired of doing that.
I have a selector switch so i run only one to have a fully charged backup and i want to charge them in boat seperately also.
Batteries 12vdc deep cell , acid .
I normally fish once a week to once every two weeks.
I want something large enough to charge them in less than a week.
Looking at everything i have read so far i think i need at least 150 watt solar panel because i want them to charge in the winter too.
Thanks for any input.

Are these batteries used for running a trolling motor? If so how deeply discharged are these batteries when you get back from your fishing trip? In any case if the solar panel rating of 150W is valid then I'd think that it would do the job. 150W at 12V would be well over 10A. The problem you may find is that the spec of 150W is a best case number. What would be the rating for a cloudy day, not directly facing the sun, etc. I think that its worth a try.

 

[That old Mercury]

Are these batteries used for running a trolling motor? If so how deeply discharged are these batteries when you get back from your fishing trip? In any case if the solar panel rating of 150W is valid then I'd think that it would do the job. 150W at 12V would be well over 10A. The problem you may find is that the spec of 150W is a best case number. What would be the rating for a cloudy day, not directly facing the sun, etc. I think that its worth a try.

I use the main battery for cranking and running electronics and sometimes the anchor light until it gets daylight.
I use a trolling motor sometimes but not much.
With my cheap 10 amp charger it normally takes a full 12 hours before the charger goes into the maintaining mode.
The other backup battery i dont use it all . Its just for cranking if i need it.
So i could use a small solar maintainer for it.
I just want enough solar wattage since it will be laying flat and not solar tracking since this will be reducing power input of course.
I would rather be over rated than under rated of course.
Thanks for the help

 

[That old Mercury]

@tpenfield

Hi
Have i done something wrong?
I do not see a response
Thanks

 

[alldodge]

Hi
Have i done something wrong?
I do not see a response
Thanks

Putting someones user name in like I did notifies the user to come to the thread. tpenfield (Ted) is most likely out having fun and will see it when he returns. Ted has installed and is currently using a solar panel on his boat now

 

[That old Mercury]

Putting someones user name in like I did notifies the user to come to the thread. tpenfield (Ted) is most likely out having fun and will see it when he returns. Ted has installed and is currently using a solar panel on his boat now

Oh ok
I did not know that was how it worked.
Thought i did something wrong.
Thanks for the explanation.

 

[tpenfield]

Greetings and thanks for the heads up @alldodge

I'll assume that you have 2 100 Ah batteries, and you generally will discharge them to 50% . . . so 100 Ah of charging

A solar panel will give about 65-75% of its rated capacity, based on my experience. The resting voltage of the batteries is going to be about 12.7 volts, so 12.7 x 100 amp-hours is going to be 12,700 watt-hours

If you want to charge during the week (5 days), you will want 12,700/5 = 2,540 watt-hours/day. If you assume 10 hours per day charging @ 65%. . .
2,540/10/0.65 = 390 watts of solar panel. (so call it 400 watts)

If your batteries are less capacity, you can factor down accordingly vs. the 100 Ah assumption.

You will need a solar controller so that you don't over charge the batteries, etc. A solar controller that has MPPT would be best to maximize the efficiency of the solar charging.

 

[tpenfield]

And, yes - out on the boat today.

 

[That old Mercury]

Greetings and thanks for the heads up @alldodge

I'll assume that you have 2 100 Ah batteries, and you generally will discharge them to 50% . . . so 100 Ah of charging

A solar panel will give about 65-75% of its rated capacity, based on my experience. The resting voltage of the batteries is going to be about 12.7 volts, so 12.7 x 100 amp-hours is going to be 12,700 watt-hours

If you want to charge during the week (5 days), you will want 12,700/5 = 2,540 watt-hours/day. If you assume 10 hours per day charging @ 65%. . .
2,540/10/0.65 = 390 watts of solar panel. (so call it 400 watts)

If your batteries are less capacity, you can factor down accordingly vs. the 100 Ah assumption.

You will need a solar controller so that you don't over charge the batteries, etc. A solar controller that has MPPT would be best to maximize the efficiency of the solar charging.

Hi tpenfield
I have 2 -100 Ah batteries, i only use one of them for everything and the other one is only ever used for emergency cranking only .
I am assuming a normally solar maintainer would be ok to keep it topped off.
I always try to make a fairly long run so i have a long run back to let the motor do some charging.
On my math i was also using 50% discharge.
Charge controllers for the lead acid battery is my next question
Reccomended charging is 13.5 volts reccomended charge amps 5 to 15.
I dont want to boil the battery or sulfate it.
How are these varibles handled when solar output is dropping in the evening ? Or when the output is low when the sun is rising?
Thanks for the help.

 

[tpenfield]

A solar controller will manage the charging. When there is enough sunlight, the solar charger will start charging, and stop when the light diminishes. The charging will fluctuate based on clouds passing by etc.

The solar controller will put out the amperage that it can, based on how much sunlight there is. This is the main difference as compared to a charger powered by house current, as you get a constant supply of power from the house outlet.

Your choices are to allow more time to charge up the batteries, or have more solar panel.

I would expect a 150 watt panel in full sun to yield about 8 amps into the battery(ies). you'll get less amperage in the early AM and later PM hours. If you are charging just one battery, you might get the battery fully charged in 2 days vs. the 10 amps and 12 hours that you are seeing now.

Depending on the controller, you can set the maximum charging amps, so you don't cook the batteries. Generally, a small solar panel (100 - 200 watts) will not have enough power to damage the batteries.

 

[That old Mercury]

A solar controller will manage the charging. When there is enough sunlight, the solar charger will start charging, and stop when the light diminishes. The charging will fluctuate based on clouds passing by etc.

The solar controller will put out the amperage that it can, based on how much sunlight there is. This is the main difference as compared to a charger powered by house current, as you get a constant supply of power from the house outlet.

Your choices are to allow more time to charge up the batteries, or have more solar panel.

I would expect a 150 watt panel in full sun to yield about 8 amps into the battery(ies). you'll get less amperage in the early AM and later PM hours. If you are charging just one battery, you might get the battery fully charged in 2 days vs. the 10 amps and 12 hours that you are seeing now.

Depending on the controller, you can set the maximum charging amps, so you don't cook the batteries. Generally, a small solar panel (100 - 200 watts) will not have enough power to damage the batteries.

Great information.
I think at this time i need to get a battery health monitor to see what % my battery is in after loading it on the trailer since i will be using the tilt and trim with the motor off and check it a few times.
Maybe i only need a small maintainer.
I will be back to this post latter in the month to let you know what i come up with.
Thanks for everything

 

[That old Mercury]

Hi tepenfield
After buying a battery percentage meter and checking my main battery after a short trip today i check my main after loading it on the trailer the meter showed 12.4 volts and the battery at 65%.
This wasnt a worst case , so the 50% used during a trip would be a good assumption.
So i can follow your advice on what i need.
On the house battery i think a good solar trickle charger with low solar voltage shut down should work.
What would be my best option?
Both batteries were fully charged the day before.
Thanks for the Awesome Help.
It is Greatly appreiated

 

[tpenfield]

I think 'we' had sized the solar panel at 400 watts (which seems a bit large), so maybe you can start with a 200 watt and see how that goes. To charge a 50% depleted battery in a few days time via solar will take more than a trickle.

Check out the solar controllers from Renogy and/or EPEver. EPEver has some models with dual outputs, the second being a trickle charge.

 

[That old Mercury]

Thanks
I was only thinking about the trickle charger for my backup battery that i never use, that is why i was thinking about the trickle charger for it to just keep it topped off.
My main battery i run everything on and from everything i have researched
I think a 250 watt is doable in Summer , but border line to No
In the winter. I could go with a 24 volt to keep both charged but i would prefere a cable that i would manually put on and take off instead of a bunch of switches to put them in parallel.
I am just concerned about winter charging since the solar hour is around 2.39 if i remember right and it wont have solar tracking.
I see now why thier are so many horror stories about lead acid battery damage with Diyers solar install.
It has to be done right with lead acid batteries.
The lithium and agm batteries are more forgiving.
I have a lot more research to do for sure.
I will study on this awhile and look into the information you have provided.
I have been an insustrial electrican and installer and Plc programmer for 30+ years, but solar is new stuff to me.
Thanks for the Awesome help!

 

[That old Mercury]

I need to make a correction after rereading my post after i had copied and pasted everything into my notes.
I am old and i got too hot fishing today!
I meant wiring battery in series.
Sorry