Newbie - Dock Solar Power System ??

System · April 2009

I'm working on installing a solar power system on our dock, apparently a new requirement on Corp Lakes. My need is to handle a boat lift that as I understand takes 1252 watts or 10.6 Amps, typically I would only use the lift on weekends and maybe 5-10 times per day, about 3 minutes per lift.

As always, I typically over do or over size things just because, well, it's a guy thing I guess 8), not to mention I've bought two small generators with the hopes of powering the boat lift only to be disappointed that they won't handle the lift. So this is what I've bought.
Kyocera KC130TM Solar Panel
Xantrex 35 Charge controller with LCD display, with battery temperature sensor
Xantrex (Duracell) 3000 Inverter
Two - Trojan T-105 Batteries wired in series, with water saver vent caps
Plus fuses, disconnects, breakers, bells and whistles (it's a guy thing) 8)

I have a few questions....

1. Does the DC system need to be grounded? Or is grounded to the battery only, sufficient? If required, can it be grounded to the dock frame, water or does it require a ground wire up the ramp to a ground rod?
2. The system will be installed in the dock storage box without ventilation (a 30" wide by 24 " deep by 6 ft. tall box) I've heard you need to install the batteries within an insulated box, if I place the batteries in an old cooler that is fairly tight to the batteries, is that better than just a plastic tub with a lid? I'm concerned this may be to tight and allow the batteries to heat up to quickly.
3. I know I'm supposed to vent the box, but I've not seen what the requirements are for venting. I was thinking of a single 3/4" to 1" PVC pipe of the top of the cooler direct to the outside wall of the cabinet. I could increase the size if recommended.
4. Off the inverter, I was planning on going to a box with two 15 AMP GFCI breakers, one circuit to the lift, the other just an extra for a radio or whatever. Does this need a ground or is the ground back through the inverter OK? Does the AC side need to be grounded to the frame?

I know I'm throwing a lot out there, but just want to make sure I get things right with the metal frame and water surround.

Thanks in advance for your help.

tsanders - Newbie

icarus · April 2009

Re: Newbie - Dock Solar Power System ??

Just at quick glance,,, I would worry about starting current of the motor loads.. 10.6 amps at 120vac is going to be more than 110 amps on 12vdc. My guess is the starting load of the motor might be 5 times that,,, causing you grief with the inverter low voltage disconnect.

Second,,, you projected usage of 10 times a day works out to be ~616 wh/hours or .61kwh (Not counting any starting surge or line loss) Your 135 watt panels,, given our general rule of 50% of name plate available to the inverter net/net, give you only ~400 wh/day. (135X6hours of sun (optimistic) X 50%=40 wh.)

I think you are going to start out in the hole,,,unless you are prepared to run a generator more often I think you will need more panel capacity.

Your 135 watts of panel might put out ~7-8 amps on a perfect day,,Your Trojans would have a AH capacity or ~ 250ah if memory serves about t-105's. Ideally you should have panel capacity or at least ~5% of ah capacity (12 amps) to a maximum of ~13% or 32 amps. I think you are bit low here as well.

I would look carefully at the motor load and see what it's starting and running amps are. Consider testing it with a kill-a-watt meter through a number of cycles then you will have a real number

Tony

mike95490 · April 2009

Re: Newbie - Dock Solar Power System ??

I'd ask:
What kind of motor is it (look at the nameplate)
5-10 x on a weekend day ? Is this personal use, or commercial ?
Can the lift motor be changed for a DC motor, like a Jeep Winch motor ? Skip the 120V conversion

My suggestions
Strongly consider a 48V system, based on 4 12V batteries, & BEEFY Xantrex XW4548 inverter. Yes, it's overkill, but not likely to get smoked like a $800 inverter may be prone to. You are talking LOTS of motor starts here. What's it going to cost to replace the lift motor if the inverter burns it out?
Maybe use a Honda EU1000 generator to recharge the batteries with, instead of solar PV?

System2 · April 2009

Re: Newbie - Dock Solar Power System ??

I don't know that the motor has a name plate, this information was provided by Hydro Hoist, the boat lift manufacturer. The motor is a high speed motor that powers a blower, which fills the air tanks. So I don't think there is a big start draw. I've talked with a few solar power dock installers, the packages they normally install for this type lift has one 130 watt solar panel, two Trojan T-105 225 Ah batteries and typically just a 2,000 watt inverter with a 12v system.

System2 · February 2010

Re: Newbie - Dock Solar Power System ??

Did you ever get this system up and running? I am in the exact same situation, though I am still waiting for the exact requirements of the lift motor, but same type of lift.

Funny that the dock companies sell 10w and 20w solar panels for this application. Luckily I did some research first.

I was actually hoping to use one of the smaller Kyocera Panels like the KC65, concerned if double that didn't work for you.

BB. · February 2010

Re: Newbie - Dock Solar Power System ??

TrikinCurt,

You may try sending Tsandars a PM --- He/she has not logged in since early last year.

Otherwise, if you want to continue the conversation we can try to help you.

-Bill

System2 · February 2010

Re: Newbie - Dock Solar Power System ??

Actually I did install the following system last year, I've had excellent results from the installation, I think I spent around $1,400-1,500 with everything. Just a couple of notes I might make. I did install the batteries in a normal cooler which was then placed in our storage cabinet, it was a good fit, but I did drill a 2" hole through the back wall of the cooler and cabinet to provide ventilation with a 2" PVC pipe and vented cap to keep water out. I was told that 2" may not be large enough, but we've had no problems. We did install a ground rod back on the shoreline just grounding everything to the frame of the dock just for safety sake, not sure we absolutely needed to. My guess is that if you did the two T-105 batteries and you didn't use the lift any more than I typically do, the 65 watt panel would be adequate, you can always add another later if need be. My thoughts when I did this was that with 120v power, we may use more power for other things, it's great for using smaller tools on the dock like drills, chargers, jigsaws, radios etc. One lesson I learned is I had to add a large fuse to support the amp load between the batteries and the inverter, otherwise the inverter would not work.

Kyocera KC130TM Solar Panel
Xantrex 35 Charge controller with LCD display, with battery temperature sensor
Xantrex (Duracell) 3000 Inverter
Two - Trojan T-105 Batteries wired in series, with water saver vent caps
Plus fuses, disconnects, breakers, bells and whistles (it's a guy thing)

tsanders

BB. · February 2010

Re: Newbie - Dock Solar Power System ??

Tsanders,

Nice to see you back and glad to hear it worked out well!

-Bill

System2 · February 2010

Re: Newbie - Dock Solar Power System ??

tsanders wrote: »

Kyocera KC130TM Solar Panel
Xantrex 35 Charge controller with LCD display, with battery temperature sensor
Xantrex (Duracell) 3000 Inverter
Two - Trojan T-105 Batteries wired in series, with water saver vent caps
Plus fuses, disconnects, breakers, bells and whistles (it's a guy thing)

tsanders

So what did you use to mount the panel? Did you buy a specific mount? I am trying to buy now to install in April/May. Getting a new dock for the boat I bought in the fall and excited to get it all going as soon as I can. (the whole cabin fever thing for those stuck in the midwest).

Also, I have heard that for a lot of things you don't need a fancy sine wave inverter, just enough power. I was looking at something like this:

http://www.dcacpowerinverters.com/customkititems.asp?kc=PW3500-0AWG

Anyone know if that is a bad idea?

Also, did you find the LCD to be worth the $80 or whatever as an add-on? I do love gadgets, but after I get this going I have the adventure of trying to beam a WI-FI signal from the dock to my house. I will have plenty to play with...

SolarBeagle · March 2011

Re: Newbie - Dock Solar Power System ??

I found this forum while researching solar power for my boat dock. Like tsanders I'm installing a Hydrohoist boat lift. It comes with a 120VAC blower motor (~9.9A running load). I'm planning to replace the blower with a 24VDC model (Ametek 116515-13 if anyone cares). This was suggested by a Hydrohoist representative. This motor draws 21.5 amps at 24V. The 24V motor will take longer to lift the boat but the simpler system is worth the wait.

So I'm planning a 24VDC system utilizing two 55Ahr AGM batteries (available from a local supplier reasonable price/quality). The Army Corps doesn’t like flooded batteries. Assuming two lifts per day at 5 minutes run time each => 2 * 5 * 25V * 21.5A = 5375 Watt-minutes or about 90W-hr, I’ll use 100W-hr for simplicity.

Assuming 3 days without sun =300W-hr from the batteries => ~25-30% DOD so the battery size should be adequate. Using 10% of the battery Ahr capacity as a bulk charge level suggests ~130 Watts of perfect panels or 170 Watts using the 77% de-rating factor I saw somewhere around this forum.

Where I could use help is with the solar panels and charger. The dock roof faces south and has a ~20 degree pitch with lots of available space. We are located in southern Virginia (~36 degree latitude). Do I really need 170 watts of panel capacity? I’ve seen some inexpensive thin film panels (Kaneka LE-055, Voc = 23V, Vmp = 16.5, Imax = 3.3) who’s major drawback seems to be size. To get the 10% bulk charging current I would need 4 panels in a series/parallel configuration. Seems like a lot. Other suggestions? What sort of charge controller would be appropriate for this application, marine environment, etc? I have looked at a Morningstar SunSaver SS-10 as one possibility. I would have to connect the boat lift directly to the battery vs. using the controller to manage the load.

I would rather err on the larger size. We will probably find other uses for electrical energy at the dock over time (no dock lights allowed at this lake so that won’t be a factor).

John

Cariboocoot · March 2011

Re: Newbie - Dock Solar Power System ??

SolarBeagle; welcome to the forum.

You should go large on the panels. Insufficient panel is problem #1 we see around here. If you want good battery life merely being able to "put back the Amp hours" isn't good enough. You have to put it back fast enough to keep the battery happy. Fortunately this isn't as much of a problem with AGM's as it is with FLA's. Under normal circumstances, 110 Amp hours would not need more than 200 Watts of panel. Indeed the minimum calculation would be half that:

110 Amp hours @ 5% = 5.5 Amps @ 14.2 Volts charging = 78 Watts less 77% derating factor = 101 Watts. That would also harvest about 26 Amp hours per day, which would mean you could run your boat lift for approximately one hour per day. If that's not sufficient time, up the panel Wattage to keep up with consumption. Note that these calculations are based on typical factors like 77% efficiency in panel/charger and 4 hours sun a day. Your actual results may be better - or worse.

i wouldn't bother with thin film panels in this application. One good crystaline unit should suffice and be easier to install.

SolarBeagle · March 2011

Re: Newbie - Dock Solar Power System ??

In the 150 Watt range I have seen some single PV panels with a Vmp around 34-35V. What type of charge controller should I be looking at.

If I understand things correctly a PWM controller will not allow the capture of all the available wattage of the panel. Something like 34Vmp - 28V charge voltage x Imp will not be harvested. The MPPT controllers will find the Vmp and convert the Vmp * Imp = Vcharge * Icharge. Is the difference worth the controller cost difference? I suspect for my small system the difference is not worth the extra cost of the MPPT controller.

What controller models are recommended?

Thanks for all the great information available on this forum

John

BB. · March 2011

Re: Newbie - Dock Solar Power System ??

Yes, you are correct that PWM requires, more or less, match Vmp/Vbatt voltages for optimum power transfer...

All About Charge Controllers
Read this page about power tracking controllers

From smaller to larger MPPT controllers:
Morningstar SunSaver 15 Amp MPPT Solar Charge Controller
Rogue 30 amp 12/24 volt MPPT
Morningstar TriStar 45 amp MPPT solar charge controller
Morningstar TriStar 60 amp MPPT solar charge controller
MidNite Solar Classic MPPT Charge Controller (90 amp?)

And Xantrex / Outback also make MPPT charge controllers that a lot of people like too (typically 60-80 amp).

For example, a 15 amp MPPT controller can economically manage about a maximum panel array wattage of (roughly):

15 amp * 14.5 amps * 1/0.77 derating = 282 watts @ 12 volt bank
15 amp * 29.0 amps * 1/0.77 derating =565 watts @ 243 volt bank
etc...

You can install a larger array, but it will limit array wattage (battery charging current) on cool days around noon... (more array, more time/days in current limit).

-Bill

SolarBeagle · June 2012

Re: Newbie - Dock Solar Power System ??

With the guidance of this forum and other sources I did install a solar system on my dock last year. I replaced the 120VAC motor with a 24VDC motor for ~$100 which eliminated the need for a big inverter (see prior post for details). I bought a single 180 watt panel (~26Vmp) and a ProStar PS-15 charge controller. The system has two 55Ahr AGM batteries for energy storage. This system has worked great. In full sun it takes about 15-20 minutes to recharge the batteries after using the boat lift. I can get 5.9-6.0 amps from the panel during a lift when the battery voltage drops to ~24.0V. The lift motor draws about 21A. At most we may use the lift twice in a day, usually only once.

I have since added a 24 to 12V DC-DC converter to power some small 12V loads such as a radio. I also added a 24V 400W inverter on my boat to power the two trickle chargers I already had installed on the boat. I used two 12V auto relays in series to break the charger to battery connection so the boat batteries don't discharge through the trickle chargers when the 24V power is off. I have a simple timer that turns the 24V to the boat inverter on MWF from noon-2pm. The system kept the dock and boat batteries fully charged all winter.

The total cost of this system was about $1000 (parts only).

I have attempted to upload a diagram of my configuration.

Attachment not found.

icarus · June 2012

Re: Newbie - Dock Solar Power System ??

Glad it worked out. You are experiencing the second law of PV. Loads will always grow!

Tony

vtmaps · June 2012

Re: Newbie - Dock Solar Power System ??

SolarBeagle wrote: »

I bought a single 180 watt panel (~26Vmp)

Thanks for the followup. It looks well thought out, and with a very nice diagram. I'm glad to see all those fuses. I was going to mention that I didn't see how you could charge those batteries properly with a Vmp of ~26, but I looked up those panels in a database and see that the Vmp is actually ~36.
--vtMaps

Newbie - Dock Solar Power System ??

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