Using my solar panel over the winter

[weinie]

I have a small 35w panel w/ controller that I was thinking about using during the winter layup on the hard.
The boat will be shrinkwrapped (with the panel outside the plastic) this year, but I have a small computer fan in the cabin attached to the LOAD terminals of the controller that I would like to use to circulate some air to minimize any potential for mold.
I also want to keep both batteries charged. They are two identical 650 starting batteries purchased at the same time. Over the summer they are both topped off by the onboard AC charger.

Here are my concerns.

1. I would need to put the battery switch to "both" to charge both batteries. Thus they would be charging in parallel. Could this lead to problems?
2. If snow builds up on the panel and there is no sun for days or even weeks, the controller should kill the fan if the batteries drop below 11.3 V as shown below. Charging should then resume and the fan should go back on after the batteries reach 12.5V again. Is this sufficient?

Here are some specs I copied and pasted :

High Battery Voltage System
Shutdown (8 seconds): 15.5 V
• Reset For High Voltage Shutdown (I n s t a n t l y): 14.5 V
• B a t t e ry Equalization: – 15.3 V
• Regulation Vo l t a g e : 14.1 V
• B a t t e ry LVD Voltage (32 seconds): 11.3 V
• Load Reconnect After Low Voltage Disconnect (LVD) ( I n s t a n t l y ): 12.8 V
• Automatic equalization: – 14 days
• Equalization can be triggered (32 seconds): – V < 1 1 . 4 V

[norsearayder]

i let my panels run last winter on the hard.170 watts running into 3 agms =no problems.i went aboard in the winter and turned on everything i could to try and get a demand going, those bats were so full!

[Undadar]

I'm not an expert but it is my understanding that such a small charge (35 watt = maximum of about 2.5 amps) is not going to hurt such a large battery bank even if it is at full charge. So, you are ok there.

Regarding #2. Yes, that is correct. However; 11.3 volts is pretty much a totally discharged battery. Discharging to that level is not good for them. I suspect a tiny little fan would take many weeks to discharge such a large bank so perhaps not an issue. Is it possible to change the voltage level at which the load is cut to something around 50-60% capacity (depending on the state of your batteries, around 12.3-12.4 volts)?

Totally different situation but.... I leave a medium size fan (~1 amp draw) running all the time in my boat in Florida with an 80 watt panel and ~400 amp-hour battery bank.

[mitiempo]

Undadar

It is not a large bank - only 2 smaller starting batteries - maybe group 24 or 27.

weinie

If you are not able to be at the boat often enough to clear snow orient the panel to the south and at a fairly steep angle so the snow will slide off easier - you will want it to be towards the south anyway.

Charging in parallel is not a problem. If the controller is a 2 bank run the wires direct to each battery avoiding the battery switch.

[Undadar]

Originally Posted by mitiempo

It is not a large bank - only 2 smaller starting batteries - maybe group 24 or 27.

Oops, sorry. I read 650 and it went into my head as a 650 amp-hour bank.

[hellosailor]

Equalization every 14 days would seem to be somewhere between totally unnecessary and flat out abuse.

[ebs001]

Originally Posted by hellosailor

Equalization every 14 days would seem to be somewhere between totally unnecessary and flat out abuse.

He definitely does not want to equalize over the winter so I would suggest he disable the auto-equalize.

[rikhall]

My stupid solar panel does not seem to work in the winter. Any suggestions?

Do you think it might be the three feet of snow stopping the sunlight?



Rik

[weinie]

I heard it wasn't supposed to snow up there this year

[noelex77]

If the panel does get covered by snow and the battery voltage drops to 11.3 this will severely shorten the life of the battery. Dead if left at this voltage for long
Computer fans draw very little power however and this will take a long time even combined with the self discharge.. How often will the boat be checked?
The regulation voltage of 14.1 is a high for standby use and will result in some electrolyte loss. About 13.7 would be much better
I would think about a new controller with a proper float voltage and an adjustable load disconnect that could be set to something more appropriate like 12.4V.
Set float to 13.7 with a monthly boost to 14.4V for 1 hr to stir the electrolyte up a bit (this can be done via the equalization cycle if this adjustable)