Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 17-01-2020, 13:00   #1
Registered User
 
sanibel sailor's Avatar

Join Date: Feb 2013
Location: Sanibel FL
Boat: 1979 Bristol 35.5 CB
Posts: 1,587
Planning/engineering for focused solar/battery system

I am engineering a small, very focused electrical system. I am planning a 300 mile adventure race in Florida in March aboard an engineless Windrider 16 trimaran. I'd like to be able to use my ST1000+ tillerpilot for say 6 hours a day. No other electric draws. Tight budget and no long term plans after this race.

Trying to figure out solar adequacy and battery size.

It says the unit pulls 0.5 to 1.5 amps, (0.04 on standby) but that is for a boat up to 6600lb. I hope that a very light boat will allow a short tiller arm, less motor excursion and consumption will be much reduced. I will need to adjust the gain way down.

1) Am I overly optimistic to hope for 3 amp hours a day usage?

I have a 20 watt rigid solar panel. It will be soft mounted and so I can adjust it to some extent to optimize output. Most likely limited to keeping it out of sail shade rather than perpendicular to the sun. At max output, around 1.5 amps. I will be using a cheapo eBay solar controller.

2) Is it reasonable to expect to get 3 or more amp-hours per day out of it in March in Florida?

Planning on getting a small Sealed Lead Acid battery, perhaps 18AH size, to run the tillerpilot. I will need to make or adapt a battery box as I don't think they are readily found in this size. Weight and volume are important. I don't want too big nor too small. As the battery is only $30 or so, I am willing to accept a short battery life associated with deeply discharging it, but it has to last the week or so planned trip. I will also have a separate small 3-5AH SLA battery charged to keep cell phone and handheld GPS going.

3) Does this seem like an appropriate battery capacity for this scenario?
__________________

__________________
John Churchill Sanibel FL
NURDLE, 1979 Bristol 35.5 CB
sanibel sailor is offline   Reply With Quote
Old 17-01-2020, 15:52   #2
cruiser

Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,304
Re: Planning/engineering for focused solar/battery system

Best to actually measure the Ah per day with a wattmeter / coulomb-counter, and go for a battery 3-4x that size.

Check out the small LFP units sold as motorcycle starter batts.

Yes 20W panel should put 5-7Ah per day into a 12V battery but only in very good insolation conditions.
__________________

john61ct is offline   Reply With Quote
Old 18-01-2020, 13:46   #3
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 13,668
Images: 14
Re: Planning/engineering for focused solar/battery system

We are a bit further north than you, but we never saw more that 1.6A from a 45w solar panel mounted flat on the deck even in good sunshine. I think you need more and a PWM solar controller to keep an eye on things. They are cheap as chips now. We just bought one of these to measure the freezer. Not fitted yet but cheap enough and will enable you to see what is going on and how the solar is keeping up. Must be something similar states side.

https://www.ebay.co.uk/itm/UK-30A-30...72.m2749.l2649

Are you only racing during the day?

Ignore Johns advice (most do) Lithium motor cycle batteries are twice the price of an similar sized AGM and since you have no plans after the race, that is money that can be spent elsewhere.

Buy yourself a cover, the autopilots are not waterproof!

https://www.ebay.co.uk/itm/Raymarine...0AAOSwa39dalkZ

Quote:
Originally Posted by sanibel sailor View Post
I hope that a very light boat will allow a short tiller arm, less motor excursion and consumption will be much reduced. I will need to adjust the gain way down.
Don't think it works like that. Are you aware they are full of plastic cogs and little elastic bands. How fast does this tri go? they work well at 5 knots, we used one for a decade (ST2000+) might be difference at 15 knots.

Photo from Chip Fords website:

http://www.chipford.com/tiller-pilot_problem_2.htm

Pete7 is online now   Reply With Quote
Old 18-01-2020, 16:09   #4
Registered User

Join Date: Jul 2005
Location: Bellingham
Boat: Outbound 44
Posts: 8,248
Re: Planning/engineering for focused solar/battery system

SS
You are getting good advice from Pete7.
Will you have time to do any test runs with the electrical setup before the race?
I'd estimate something like 1.5a draw at 50% duty cycle at 6 hours to get 4.5ah per day usage. Probably a little high, but better to error on the safe side. The entire race sounds like about 10 days, so thats a consumption of around 45ah.
If you could mount two 20w panels, one on one side of the boat and one on the other, this will reduce the time screwing around with moving them while racing and give you much more charging in the hours before and after being on the water. If you can get 1a for 6hrs back into the battery, that should keep you pretty safe with a 20ah battery.
__________________
Paul
Paul L is offline   Reply With Quote
Old 19-01-2020, 10:48   #5
Registered User
 
sanibel sailor's Avatar

Join Date: Feb 2013
Location: Sanibel FL
Boat: 1979 Bristol 35.5 CB
Posts: 1,587
Re: Planning/engineering for focused solar/battery system

Thanks
I will make a cover. Gonna be a wet ride.
I already have the pilot, panel and a PWM controller.
Found a plastic box this AM that will fit the battery and controller perfectly with an area to run wires out.
I am planning on hand steering during day and napping, when safe, on autopilot at night. Much is weather and progress dependent.
__________________
John Churchill Sanibel FL
NURDLE, 1979 Bristol 35.5 CB
sanibel sailor is offline   Reply With Quote
Old 20-01-2020, 04:33   #6
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 13,668
Images: 14
Re: Planning/engineering for focused solar/battery system

Certainly going to be fun. I would put a go pro or something on a pole at the back and film yourself each day. Let us know how you get on.

Pete

https://cdn.filestackcontent.com/A7z...ion=1555379159

__________________

Pete7 is online now   Reply With Quote
Reply

Tags
battery, engine, engineer, grass, solar

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Crew Available: Reliable, Dependable, Focused Sailor Greg Crew Positions: Wanted & Available 1 02-02-2018 13:28
My Quest for Water - Engineering build on a RO system theller Provisioning: Food & Drink 72 23-12-2017 13:29
Need help on a new battery/charger/solar system... Brannon132 Electrical: Batteries, Generators & Solar 0 19-06-2015 14:38
Which solar regulator for duel battery system? Silverback Electrical: Batteries, Generators & Solar 23 07-07-2008 09:35

Advertise Here


All times are GMT -7. The time now is 15:02.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.