Matching solar panels to batteries to consumption

[DawnTreader]

Our only means of charging the battery bank is a 55w panel on a solar tracker. We run variously lights, fans, computer, iPad, vhf/ais, delorme inreach, and AA and AAA battery chargers. We replaced all lights including Nav lights with LED. This is a huge saver.

Brian
www.sailingdawntreader.com

[Sauntress]

Thank you all for the crash course in LED/solar. I am much the wiser and able to take things from here on my own.

[reed1v]

First, try for a 20% plus efficient solar panel. New technology gives way more charging capacity. Second back up solar with wind generator and an in water generator(can be attached to transom). That way you will charge at anchor, while sailing in cloudy conditions, and even in the middle of the night. Flexible panels are the way to go. While ugly, a friend put panels along his sides. Got enough reflective light to get a decent charge.

[socaldmax]

Originally Posted by Sauntress

This question concerns an engineless wooden yacht of modest proportions (28' x 8' x 4'10") sailed fairly adventurously (meaning long distances) with minimal electrical power requirements. Specifically I would appreciate advice on the solar power needed where

1. The vessel is now fitted with two new MK50-12-SLD M batteries on which are written

12V-42.5AH/5HR
12V-50 AH/20HR

Which appears to mean 50 amp hours each? They have to run, all night, every night, the following

Masthead 25 watt 12 volt lamp (giving 2.1 amps?)
Compass light 0.1 amp
And very occasionally a cabin lamp, chart table lamp or galley lamp each at 12V x 10 watt (or 0.8 amps?) for a few minutes at a time (night lighting aboard Sauntres is by oil lamps)

The question is what solar panel set up do I need to keep that lot going indefinitely on passage. (I am replacing here, a 30 years old Unisolar MBC262 rated to produce 15 to 29 amp hours PER WEEK, but measures 15" by 26" which is a very useful size.
Thank you

The first thing I'd recommend is to replace all lights with LEDs, huge power savings right off the bat.

The 2nd thing I'd do is replace those low cap. batteries with a pair of golf cart batteries. You'll get double the cap. for the same amount of batteries and they're cheap, about $85 ea. near me.

The 3rd thing I'd do is get a 200w to 250w solar panel and a $100 20 A MPPT solar controller. It's not much larger than a 100 w panel and for the cost of mounting a panel on some sort of frame, you might as well get a decent amount of power out of it, not to mention 200 - 250 w is the sweet spot for cheap panels. There are local vendors selling 208w Sharp panels as low as $65 ea.

This way, not only can you power everything, you can think about powering some additional items like autopilot, chartplotter, etc. No sense living like you're in the 18th century.

[Paul Elliott]

Most LED navlight replacement bulbs are not *certified*, but they may still be compliant with the requirements. You have to decide if the potential issues of non-certification (after an accident) are worth the cost of a certified fixture.

There have been many reports and tests showing that some LED tricolors (or LED replacement lamps) can interfere with VHF and AIS radio. The proximity between the masthead VHF antenna and the tricolor can make even a small amount of LED regulator noise be a big problem.

Some LED tricolors use extremely radio-quiet regulators. I have the "Amazonia" tricolor and have measured no noise, and experienced no interference. The design is particularly RF-silent: Optolamp Amazonia Mirim 111 - LED Tri Color Navigation Light, Anchor and strobe, Auto on/off Boating Gear fit for the King

Marinebeam also makes radio-quiet fixtures and replacement bulbs. These use switching regulators that have been designed for quiet operation. I haven't tried their tricolor, but do have one of their bi-color bow lights and it puts out virtually no noise: https://store.marinebeam.com/

And don't be persuaded by charts showing that a particular fixture passes FCC Part 15 interference requirements (or the European equivalent). This requirement is a general one and absolutely does not guarantee interference-free operation when the VHF antenna is adjacent to the fixture. This requirement is a good start, but hardly sufficient. A fixture needs to pass this requirement by a *very* large margin to be safely put next to your VHF antenna.

[subs57]

This website is quite useful. Provided you are ok with elementary maths - which I'm sure you are - this can act as a good guide.

How to calculate battery run-time when design equipment using batteries; Battery Technical Resources for Design Engineers from PowerStream

[Martkimwat]

Take a look at the NASA Marine combined tricolour/anchor light in UK, it's about £160 or less. I fitted one two years back, no problems with RF interference. Also you need to consider that useable power out of your batteries is between 50% charge and 80~85% charge since to fully charge them off solar panels is well nigh impossible in practise so in your case useable power is just 30~35Ahrs.

[Sauntress]

Since this is the first time I have asked a question on this forum, as opposed to browsing, I am impressed with the response, varied in nature though it is.

I had better come clean. I took the engine out of the boat many many years ago (mid 90's) and have sailed, engineless over most of the European Atlantic seaboard from Norway to Spain ever since with no more than described in the original post. So I am by nature a bit mad, and perfectly happy in the 18th century.

However, I now have my eyes on more distant horizons and part of the planning for that (a small part in truth) is the business of electricity aboard. Having digested the advice from various quarters a LED masthead light is a must and I have tracked down replacement bulbs (thank you Mr moderator for your extra comments) tricolour. That is the biggest drain on the batteries by far. The rest, so far as I am concerned is optional. I use paper charts, sextant, hand held battery powered GPS, radio (looking now at short wave) and have little space for solar panels. In fact the only place is on the afterdeck immediately aft of the cockpit where, regrettably the shadow of the tiller, will muck up the charging.

So I will keep the new batteries, add the 50 or 70watt or whatever physically will fit monowhatitsname panel and see how we go. Trailed generators (at which I had a look) are beyond my pocket, would probably tangle with the Walker log and have very mixed reviews on this forum. Some love them. Some hate them.

But thank you, all of you, for your comments, which I am absorbing like the proverbial.

[foufou]

There are new and less expensive navigation lights coming out all the time. I recently bought a red and green 2NM lights through Amazon for about $17 US each. Stern light and steaming light (which you don't need) same price. So for the three $51 free shipping if you have amazon Prime. Of course not certain you can get the same deal where you are. F

[newhaul]

Originally Posted by foufou

There are new and less expensive navigation lights coming out all the time. I recently bought a red and green 2NM lights through Amazon for about $17 US each. Stern light and steaming light (which you don't need) same price. So for the three $51 free shipping if you have amazon Prime. Of course not certain you can get the same deal where you are. F

Unfortunately there is a big difference between the nav side lights and a tri color masthead light.

[sailinglegend]

Originally Posted by foufou

There are new and less expensive navigation lights coming out all the time....

You should be aware that in the UK the Maritime Agency responsible for Safety at Sea have banned replacement LEDs for use in Navigation lights that were designed for Tungsten Bulbs. Your insurance may be invalid if you have an accident at night.

Replacement LED units with the correct lenses are fine - but expensive.

[roland stockham]

Absolutely understand your issues, I also run a traditional wooden boat. Most people have started by saying 'look at reducing consumption' and yes, this is an essential first step. I would add that with a very small electrical set up you may also want to consider going the way the Pardy's did and run things off individual batteries. So set up an LED nav light with its own battery that has enough charge to run it for 2 nights. You can even do this by running 3 separate lights in traditional wooden boxes and run them off rechargeable AA cells so you can carry some prime cells as backup. Do this for all your essentials (nav lights GPS, radio) and they you can run the luxuries like cabin lights if and when you have power. It will not be the 'most efficent' system but it may be a better solution than trying to scale a modern big boat system to fit you boat.

[Ironman162]

Here's a lateral thought.
Your sail will cast a shadow over your solar panel and you will run low on power.

Would you perhaps consider a small wind turbine to suppliment the solar panel?

The 3:4:5 ratio works well for me: 300W solar, 400W wind and a 500A battery bank on a 10m boat and I havent run out of power yet.
In your case it roughly translates into ideally 100w solar, 130w wind and 160A battery

Also bear in mind that in time the mini maxi grows into a super maxi!
You may start modest but as time goes by one tend to add equipment to make life easier...like a phone charger or a small inverter to charge a cordless drill or a computer/tablet etc... not to mention maybe a small refrigerator later on...who likes warm beer on a sublime evening?

Anyway thats my contribution and I wish you well with powering it all up!

[Littlechay]

Originally Posted by Sauntress

That is most helpful. I have looked at the product details and the one thing I cannot find is the dimensions?

Google produced this as the first hit https://www.renogy.com/renogy-50-wat...#tab_prd-specs

Your batteries give you 100Ah... you can assume that 30Ah is usable therefore you need to make your consumption fit that.

One thing that you don't say is the duration of your trips and the length of period that the boat is unused between trips.

If your trips are just a few days duration (I don't know what you mean by longish - for me that would be 14 days or more) with 4 or 5 days between ie. typical weekend use; then you could get away with a smaller panel that won't quite bring the batteries back to full charge over the weekend but will fully recharge them ready for the next weekend.

[mitiempo]

Generally 80% is considered the limit for charging with the engine. It is very inefficient to charge above that approximate point as the batteries internal resistance climbs and they accept less and less current.

But with solar the charging can continue as long as there is sun. With enough solar wattage and a sunny location the batteries can be fully charged in one or two days. Depending on battery bank size vs solar wattage the bulk charge will often continue until the batteries are over 90%.

This won't happen with a large bank and a small solar array but it is entirely possible that a 100 AH battery bank can be charged in one day with enough solar. I think it would require over 100 watts of solar in this case, 150 watts is probably enough in the right (sun all day) circumstances.