60w solor panel enough?

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magic_mtn
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60w solor panel enough?

Post by magic_mtn » Tue Mar 27, 2018 6:32 pm

Hey all.
This is my first post. I am thinking about buying a 60w panel to charge A 12V deep cycle battery around 100ah. I am a little confused about the math.

The 60w panel is rated for 18v at 3 amp Max
Will this be sufficient for charging this type of battery?

I have seen a range of sudgeestions estions.
Was thinking maybe something like this:
https://www.amazon.com/gp/aw/d/B07432VB ... PR7O&psc=1

Will that charge my 12v battery.

Mainly wondering if this would work. And how fast it may charge the battery... Maybe I could get away with a smaller 50ah battery if this pannel will subsidize enough power.

Thanks for any advise.

My load on the battery should be about 2 amps for about 5 hours a day.

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XPTom
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Re: 60w solor panel enough?

Post by XPTom » Tue Mar 27, 2018 11:32 pm

Many good points to your question.

For small 12 volt charging system throw away almost a third of the panel's rated watts. True that 18ish volts @ 3+ amps = 60 watts, but you can't put 18ish in your 12.9 volt battery. The charge controller will pass the same 3+ amps to the battery at lower voltage and give you a net of 40ish watts.

In the Black Rock sun, if you lay your 60W panel flat and keep excessive dust off it you will get the rated 3ish amps for 10 or so hours ...... or about 30AH. .... about 1/3 of your battery capacity..... if you tilt it and point it toward the morning/noon/evening sun you will get almost 40AH for the day.

That should stay ahead of your 2 amps times 5 hour load, but add a few extra watts and you will wear the battery down.

Most would advise you have too much battery for too little panel, but that is a good side to err on if you have a typical lead battery. My 100w panel (5+ amps) rapidly charges my 70AH battery ....at first.... but the charge curve slows down and full charge never happens before sunset. It is quicker to half charge a big battery than fully charge a small one.
How many old burners does it take to change a light bulb? Just one to change the bulb..... and five more to reminisce how good the old bulb was....

flexibility is the key to success....... and poor planning is the key to flexibility

magic_mtn
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Re: 60w solor panel enough?

Post by magic_mtn » Wed Mar 28, 2018 7:55 am

Wow awesome, thanks for the info.

A few follow up questions on this topic.

It sounds like for a 12-volt battery I would only be using net 40ish volts for charging it.
Would it then make sense that I could use the 2nd output (USB) on this panel rated at 5v 2a to utilize the additional 20 Watts?

To me, those numbers add up but I am not sure if it would work. I am thinking my panel may operate at 15- 20 percent utilization at times.
If I could charge a few lights and or USB battery banks off this panel that would be an added benefit.

Would anyone have a solar charging controller they would recommend?
smaller is better as I may need to carry it in checked luggage.
Preferably something that deals with the heat well.

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XPTom
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Re: 60w solor panel enough?

Post by XPTom » Wed Mar 28, 2018 10:25 am

USB devices are great storage devices. They charge fast, but the amps they draw at 5v is simply the panel voltage cut down to 5. They will count against your panel's total amperage output. Failsafe way to get a real 60 watts is to buy a 100W panel. Then add a small fan (and water spray bottle) to your output because you'll be far enough above your 2 amp target you will have power to enjoy a breeze.

Last year I introduced a small charging problem by unknowingly buying a panel with a built in controller for the roof of my camper. The panels' 18ish output was reduced to 13.9 charging voltage on the roof, and then I was losing another .5 or .6 to thin wires on the long trip down to the battery. That half volt drop may only sound like 5% of the big picture, but slowed down the charging as battery voltage came up near full charge. This year's plan is to put the controller right at the battery so the wire loss happens before the controller does it's job.

Are you bringing a vehicle? ...and jumper cables? ... minutes of idling equals hours of solar trickle in case you need a backup plan.
How many old burners does it take to change a light bulb? Just one to change the bulb..... and five more to reminisce how good the old bulb was....

flexibility is the key to success....... and poor planning is the key to flexibility

magic_mtn
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Re: 60w solor panel enough?

Post by magic_mtn » Wed Mar 28, 2018 1:41 pm

Yes, I will have a vehicle and access to jumper cables. Right now I am more just interested in the solar thing as a hobby and I am thinking with a few experiments I may be able to run my swamp cooler purely off solar and have some juice left to power batteries when I am not using not cooler.

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spacetime
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Re: 60w solor panel enough?

Post by spacetime » Fri Apr 06, 2018 1:01 pm

I really like this panel. Suaoki 100W 18V 12V Solar Panel Charger SunPower Cell Ultra Thin Flexible with MC4 Connector Charging for RV Boat Cabin Tent Car(Compatibility with 18V and Below Devices)

Considering a second for this year

Dazey77
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Re: 60w solor panel enough?

Post by Dazey77 » Mon Jul 16, 2018 7:21 am

I think there are some things missing from this thread.

Firstly the solar sizing is based more on your load than the battery. A 60w panel could charge a 2000ah battery given long enough and no load.

Secondly you don't say when your load is. You say your load is 24w for 5hrs (or 10ah of energy/day). If the load is daytime, then the solar panel should be able to provide the load so you only need a really small battery for dust storms and the like. If the load is night (which is more likely I guess), then you need the battery to provide the power in the evening and the solar to recharge in the day.

I would go for the smaller battery, its still oversized for your needs and will be lighter, cheaper and faster to charge. You should easily get 10ah out of the 60w panel in a day.

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