help sizing solar for a boat hoist

[pascal]

Hi there, newbie here. Looking through the forum over the last week or two has been great, thanks for all the info!

Looking for an assist putting together a solar charger for a lift-tech 12/24 DC boat hoist motor. I ran some numbers, not sure I got it right though. any advice on controller, panel or battery is greatly appreciated!

Based on some looking around:
motor: 40-80 amps
lift/lower time: 3 minutes per cycle (boat @ 5000 lbs on vertical hoist which slightly larger than mine at 3400 lbs)
assuming average load of 60 AMPs
usage: 2x per day on weekends, on occasion during week

battery:
AutoCraft Marine Battery, Group Size 24M, 800A CCA I use for the winch on my trailer when needed. its advertised as a marine deep cycle but I can't find an amp hour rating
RC: 135 minutes

solar system:
Genasun GV-4 50W 4A Solar Charge Controller with MPPT
ALEKO SP40W12V 40 Watt 12 Volt Monocrystalline Solar Panel
- Operating voltage: 17.5 volts; Open circuit voltage: 22 volts
- Operating current: 2.29 amps; Diode bypass: 1*10 amps

assume 90 amp hours on the battery (no idea if that is right)
motor: 60 amps / 60 minutes = 1 amp/min * 3 minutes/cycle = 3 amps * 4 cycles per weekend = 12 amps
battery: 90 amp hours * 20% = 18 amps available to stay above 80% used

if that is right them I can run the hoist 4 times with no sun and stay above 80% depletion.

to recharge:
2.29 amps from panel * 80% for loss = 1.8
12 amps depleted / 1.8 = 6.7 hours to charge

any help is greatly appreciated!

[Sunking]

Throw all that math out the window. Batteries can only supply so much current before the voltage collapses. For FLA batteries roughly C/8 and for AGM roughly C/4. So the motor draws 40 to 80 amps which is nonsense. Which is it? 40 or 80 amps. Lets say it is 40 amps and you use FLA batteries. would mean you need a 320 AH battery, if 80 amps a 640 AH battery. You had better figure that out real quick because a 12 volt 320 AH battery will cost you $500, and a 12 volt 640 AH battery cost $1000.

For AGM at 40 amps would require a 160 AH and for 80 amps 320 AH. Because AGM cost twice as much as FLA battery cost still runs $500 and $1000.

As for charging a battery must have a minimum charge current requirement which is C/10, So with a 320 AH battery would require 30 to 35 amps. Panel Wattage required = 30 amps x 13 volts = 390 watts, just call it 400 watts. Want a 640 AH battery will require 800 watts. Again you have to nail down discharge current because a 400 wat system with MPPT Controller is going to cost you $800, and a 600 wat system with controller cost $1600. So a 40 amps system cost is $1300, and a 80 amp system is $2600.

So as you can see, all your numbers are based on a system that is used to run a very small load for 24 hours, not 5 minutes like you intend to use it. High power and Solar do not make friends with each other. They are enemies for life with your wallet stuck in between absorbing damage. No big deal for a BOAT OWNER (break out another thou$and) for play time.

[Sunking]

AutoCraft Marine Battery, Group Size 24M, 800A CCA I use for the winch on my trailer when needed. its advertised as a marine deep cycle but I can't find an amp hour rating RC: 135 minutes!

This tells you everything. 800-amps CCA means the battery can deliver 800 amps at 32 degrees for 30 seconds at 7.2 volts. Catch that? 7.2 volts from a 12 volt battery. That number also tells you the Internal Resistance at 32 degrees.

RC = 135 minutes which means the battery can supply 25 amps for 130 minutes down to 10.5 volts from a 12 volt battery. That tells you the capacity at the 2 hour discharge rate. 130 minutes = 130 min / 60 min = 2.17 hours.

25 amps x 2.17 hours = 54.25 Amp Hours. You will need 5 to 6 of those batteries wired in parallel which is complete nonsense. You would use 6 volt 320 AH batteries x 2 wired in series.

[Brian53713]

You can get four hundred watt panels, a 300 amp AGM battery , 30a victron charge controller for approximately $1,500 minus the 30% government rebate if it's still going on.

[pascal]

Thank you for the responses. Interesting a prominent seller of this system recommends a 20w panel for my use.

as for the range of the draw lifting is more effort than lowering. My winch has varied amp numbers depending on load also.

https://www.lakelite.com/boat-lift-charging-sizing-chart/

[JSchnee21]

I think we went off the deep end here somewhere. . . .

The OP stated he only plans to use the winch twice per day, on weekends. Presumably the number of aggregate amp hours at ~80amps @ 3-5min (going up) and ~40amps @ 3-5min (going down) is going to be very small. Similar to an electric tongue lift / jacks on a travel trailer which are easily run from one or two deep cycle RV/Marine batteries.

So, ideally the battery would have enough amp hours to do these 4 operations, maintain a reasonably voltage, and still be 50-70% charged when you're done. Then during the rest of the week, the solar panel system would only need to trickle/float charge the batter back to 100%. If the ~$100-200 battery dies in a year or two, throw it out and buy a new one. It may even still be covered under warranty. Buying a new battery every year @ $150 for 10 years is still cheaper than some of the other options.

That said, depending on the boat and truck (I assume the winch is on a boat trailer? or is it at a dock/dry dock?). Why not either:

1) power the winch from the truck?
or
2) charge the battery on the boat with the generator?
or
3) use shore power?
or
4) take the battery home M-F and charge it at home using a conventional car battery charger

Surely a 20W solar panel is nonsense. But there must be some decent solar based trickle chargers as well? Or you could build one. Does it need to be portable? Is someone going to steal it? Can you mount it on the winch at the dock? Realistically, you'd probably need at least 2 or 3 full-sized 60-cell panels to get your 400-600 watts. At ~1 meter^2 per panel, that's a lot of real estate.

-Jonathan

[pascal]

I think we went off the deep end here somewhere. . . .

The OP stated he only plans to use the winch twice per day, on weekends. Presumably the number of aggregate amp hours at ~80amps @ 3-5min (going up) and ~40amps @ 3-5min (going down) is going to be very small. Similar to an electric tongue lift / jacks on a travel trailer which are easily run from one or two deep cycle RV/Marine batteries.

So, ideally the battery would have enough amp hours to do these 4 operations, maintain a reasonably voltage, and still be 50-70% charged when you're done. Then during the rest of the week, the solar panel system would only need to trickle/float charge the batter back to 100%. If the ~$100-200 battery dies in a year or two, throw it out and buy a new one. It may even still be covered under warranty. Buying a new battery every year @ $150 for 10 years is still cheaper than some of the other options.

That said, depending on the boat and truck (I assume the winch is on a boat trailer? or is it at a dock/dry dock?). Why not either:

1) power the winch from the truck?
or
2) charge the battery on the boat with the generator?
or
3) use shore power?
or
4) take the battery home M-F and charge it at home using a conventional car battery charger

Surely a 20W solar panel is nonsense. But there must be some decent solar based trickle chargers as well? Or you could build one. Does it need to be portable? Is someone going to steal it? Can you mount it on the winch at the dock? Realistically, you'd probably need at least 2 or 3 full-sized 60-cell panels to get your 400-600 watts. At ~1 meter^2 per panel, that's a lot of real estate.

-Jonathan

thank you. The solar setup is for a boat hoist motor on the dock. The reference to the winch is a trailer mounted 8.5K winch I use on occasion that has a battery I can use as I rarely need the trailer winch.

Not concerned about people stealing anything, and charging occasionally on a home charger is fine. The panel(s) would be mounted onto the boat hoist which makes putting up a solar farm a bit tough

The usage of the boat hoist is fairly low, hence the smaller panel - my thought is that we don't use it much during the week so if it can make it through a weekend it likely has the rest of the week to recover.

[SunEagle]

thank you. The solar setup is for a boat hoist motor on the dock. The reference to the winch is a trailer mounted 8.5K winch I use on occasion that has a battery I can use as I rarely need the trailer winch.

Not concerned about people stealing anything, and charging occasionally on a home charger is fine. The panel(s) would be mounted onto the boat hoist which makes putting up a solar farm a bit tough

The usage of the boat hoist is fairly low, hence the smaller panel - my thought is that we don't use it much during the week so if it can make it through a weekend it likely has the rest of the week to recover.

There are a lot of "gate openers" that use a small wattage solar panel to keep the battery charged. They operate a few times a day and work just fine for years.

Unfortunately it sounds like your hoist may consume more power then a gate opener so the battery could be easily drained if not kept charged. A 20 watt panel is really nothing more than a "trickle" charger and will not be enough to keep the battery full if you have multiple cloudy days.

My guess is that you can try a small wattage panel and see how long the battery lasts. Just make sure you have some type of backup power source in case the battery dies when the boat is half out of the water.

[Sunking]

I think we went off the deep end here somewhere. . . .

The OP stated he only plans to use the winch twice per day, on weekends. Presumably the number of aggregate amp hours at ~80amps @ 3-5min (going up) and ~40amps @ 3-5min (going down) is going to be very small.

You are missing a very important point. On paper in theory a 20 watt panel and Flashlight Batteries should work As for energy not so much 12 volts x 80 amps x 0,05 Hours 48 watt hours. A 20 watt panel is over kill and can easily make 50 watt hours in a day. That 20 watt panels is perfect for a cell phone or a 12 volt 10 AH battery. Just one problem, the battery can only supply 80 amps at 3 or 4 volts and would likely damage the battery. A Winch would not operate.

Think of it this way. take 2 x 9-volt Transistor batteries wired in series.for 18 volts. More than enough voltage to start a car. Go ahead and try to start a car with a pair of 9-volt batteries, or while you are at it a battery that is 5 times more energy try a few cell phones to start a car. Will it work? Hell not it will not work and you would be a fool if you think it should work. You might not fully understand why it would not work, but common sense tells you something is not right. If you tried all that would happen is your battery gets real hot for a few seconds and starts to smoke of explode.

Batteries have several characteristics and two of the most important metrics are Specific Power which is a measure of loading capability in weight and volume expressed as Watts / Kilogram (w/kg), and Watts / Liter w/l. Specific Energy which is a how much energy is stored by weight and volume measured in Watt Hours per Kilogram (wh/kg) and Watt Hours per Liter (w/l)

OK if this were me and what I know about batteries, I would use a AGM battery made for extremely high loads and can supply 1C of load current. Not many out there that can do that. I would be looking at a 75 to 100 AH Concorde PVX, or Odyssey Extreme, or even an Optima Yellow Top AGM battery. All three batteries have two things in common. All three are AGM and made from Pure Virgin Lead. You are going to pay up for pure virgin lead AGM battery. Example the best of them is Odyssey 31-PC2150 a 12 volt 100 AH battery that will cost you every bit of $300.

With something like a Concorde, Optima, or Odyssey AGM you do not have to meet the minimum C/10 charge requirement and can get away with away with say a 30 to 50 watt panel backed up by a good small MPPT charge controller you can get this done around $500 to $600 for the panel, controller and battery. Yes the battery is real expensive, but saves you money at the end of the day and will work.

Take note on that Odyssey 12 volt battery . CCA goes up from 800 to 1200 amps.