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Solar sizing help....

Sep 25, 2019
2002 Cat 22 MkII Lake Somerville
Reaching out to the Catalina 22 community for some help in determining what size solar panel and controller I need for maintaining charge on my battery? I'll admit that I know very little when it comes to this subject but I have been reading as many threads as possible (and there's a lot of em' out there) in hopes of getting somewhat educated. However I'm now stuck in the dreaded 'analysis paralysis' stage where I'm thinking I need a solar panel sized somewhere between 5 watts all the way up to Marty McFly's Flux Capacitor. :confused:

When I purchased my used Cat 22 MkII it came with a dead Group 24 lead-acid Deep Cycle battery. The MkII battery box unfortunately is only sized for Group 24. I've been attempting to put together an energy calculation based on electrical items onboard but having trouble determining how many amps certain items pull? Hoping you guys can provide some #'s (or at least a general average) of amps per item:
  1. Cabin lights = ? amps (not LED but will be upgrading)
  2. Running lights = ? amps (not LED but will be upgrading)
  3. Anchor light = ? amps (not LED but will be upgrading)
  4. JBL Marine Stereo w/ 2 Jensen Marine speakers = ? amps
  5. RayMarine ST1000 Autopilot = (owner's manual states 40mA in Standby mode, .5A - 1.5A in Auto mode depending on sailing conditions)
  6. Depth Finder (future item) = ? amps
  7. Iphone Charger (future item) = ? amps
I foresee our power usage will typically be for 3 - 4 hrs one or two days per week for the stereo, autopilot, depth finder and iphone charger. Lights will only be utilized for shorter time periods like coming into marina during late afternoon/evening sails.

I'm looking at purchasing this Interstate Deep Cycle 24DC Marine Battery from Academy (Academy Deep Cycle 24DC Battery). This battery offers 685 marine cranking amps, 550 cold cranking amps, 81 amp hours and a 140 reserve capacity at 25 amps.

Any help or recommendations you guys can provide in regards to panel and controller size to recharge battery will be greatly appreciated! Thanks in advance!

S/V Change of Pace
Lake Somerville, TX
~~ _/) ~
Last edited:
Mar 6, 2008
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
I'm not familiar with the interior of c22
On my H25.5 I added a second battery with switch. If your engine already has built-in alternator it is enough to charge the batteries.
The devices you listed will not all be used at the same time. When anchoring I used flash lights to light the cabin. The anchor light will not drain the battery much overnight.
Dec 28, 2015
Laser, Hunter H30 Cherubini Tacoma
Assuming you can plug it in when at the slip.....I’d put another battery in it instead of solar. To make a difference over that short of a time you’d have to have several large panels that would require a mounting structure. I’d rather have the energy on hand in the batteries compared to hoping you can keep up with a panel in sun. I have ( as like most boats) the same energy consumption as you ( plus refer) I have two 100 watt panels and 4 batteries and in the PNW in the dead of summer the batteries will be recharged by about noon from the dark hours consumption and stays almost full all day.
Dec 28, 2015
Laser, Hunter H30 Cherubini Tacoma
I bought a 4 pack of solar charging led camping lanterns from Amazon and use them all the time as well for a anchor light.
Feb 17, 2006
Lancer 27PS MCB Camp Pendleton KF6BL
Hey @Zinger88, I use a 50 watt solar panel with a 10 amp controller. That is more that enough for my three batteries. Two of the batteries are on the motor side and one is on the house side. While I am out and about I am running VHF, auto pilot, two GPS terminals. When I am on shore power the solar is still aiding in the charge. So with a combination or solar and shore my batteries are always topped up. If you are on a trailer, do an initial charge with house current then let the solar keep the battery(ies) topped up. Just make sure you check them.
Sep 25, 2019
2002 Cat 22 MkII Lake Somerville
Thanks for the reply's thus far. Probably need a couple points of clarification which I now realize I failed to mention in my original post.

I have a manual start Mercury 6hp outboard w/ no alternator so can't get power from it and I also slip my boat at a marina which does not provide shore power. My initial plan has been to mount the solar panel(s) on the stern pulpit similar to how I've seen done on many Catalina 22's. Was trying not to have a bank of batteries as that would entail modification to the battery box. I wanted to move up to a Group 27 size battery for more amp hours but the original molded box that came on the MkII only fits Group 24. We typically try to get at least one sail in after work during the week for a couple of hours and another one on the weekend of longer duration so I've got a few days between sailing events to recharge.

Thanks again in advance for any help or advice provided!

S/V Change of Pace
Lake Somerville, TX
~~ _/) ~
May 23, 2016
Catalina 22 #12502 BSC
zinger....all u need is in this recent thread started by Ritgold:

My advice is to use Gene's excellent plan on panels/controller, etc., If it works for Gene, it'll work for you...he knows his stuff and has done all the research...
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Oct 21, 2008
oday 222 niagara
How will you use your boat? If it's usually 1 or 2 days, or mostly day sails a couple of times a week very little "juice" is needed and can be backed up with flash lights or portable radios. If your going for longer trips, Genes set up would be hard to beat! ( his solar panels mountings are super)
On the other hand, I usually drive to my boat (Oday 222) in the evening, spend the nite then sail the next couple of days. I have a fishfinder for speed, depth, GPS, an LED anchor lite, and a VHF radio that I keep on a majority of the time when sailing. I rarely use the cabin lites as I find it more convenient (don't have to reach as far to turn off ) to use a led headlamp, a cheapie led lantern, and a couple of flashlights. My boats elect. is a Walmart deep cell battery that is now 5 years old and cost under $100. The elect. panel is stock with only a digital voltmeter added. I keep the boat on a mooring so to charge the battery I have a small (18" x 24" solar panel I purchased on ebay for cheap as well as an under $20 controller. They are going into their 6th year. The solar panel is mounted so it is easily removed and is used only when I am at anchor or moored. When sailing it stows under the V berth and out of the way. The battery voltage usually is in the high 13s after a day of charging and rarely drops below the high 12s after using the boat 2 to three days. The few times I sailed farther or longer I took a small garden tractor battery as a back up just in case but never had to use it. Certainly, this is not a set up for extended trips. Most autopilots, for example, would drain the battery on this boat in short order, but for me, the simplicity makes the boat available and fun to sail. To date I have not lost a day of sailing to repairs and only have missed only a great sounding sound system. Maybe this year?