Solar -- some real world data

[Boatwright]

With the keeping it simple philosophy:

We have 2 - 100 watt GreeSonic semi-flexible panels mounted on a light 1"x2"mahogany frame on top of the Bimini. Good airflow underneath, and so unobtrusive that most folks don't even notice unless I point them out. The wiring is concealed under a zipper panel, along the Bimini frame, through the deck in two simple sealing glands. There are cartridge fuses in the wiring harness and a 50A rotary on-off switch under a cockpit hatch. The panels are wired in parallel. The whole rig takes about 1 hour to hook up in the spring. The surface has little pyramids molded into the plastic "glazing" said to focus the sun at low angles. These panels see a fall-off in efficiency after 4 or 5 years, I suspect from the plastic surface losing clarity. They were very inexpensive to replace which we have done once in eight years.

During our cruising season, May to October on the northern Great Lakes we see a consistent average input of 1 KWH per day to the batteries, 440 AH @ 12.8V from 4 Trojan T105 lead/acid golf cart batteries. Input is from a Renogy 50A MPPT controller - larger than required but we liked the big heat-sink when mounted inside the engine space. We also have the MT-50 Remote Monitor, a bit quirky to figure out the menu and set up features but very good at logging and keeping an eye on what's going on in real time. The state of charge feature is a weak point -- it will indicate a full charge OK with an automatic balancing feature; the partial charge shown on a bar graph is not very useful. We have an accurate digital voltmeter, that with a bit of experience gives me a solid state of charge reading first thing in the morning. With switches and solar turned off for 1/4 hour while I do the morning checks. By the time I'm ready to fire up the stove and make coffee, the resting voltage will have settled down to a reliable SOC reading. Having seen folks fussing around with expensive SOC systems, that seem to be designed around the problem of true SOC, with stuff turned on, by including input and output amp monitoring shunts, combined with a bunch of other programmed and measured variables. Again KISS and about the same amount of input from the user combined with a bit of experience gives very reliable SOC info.

The boat: 35' 1978 Hinterhoeller Niagara 35

Electrics design for efficiency:

All LED lighting.

Basic Helm Electronics - Log; Depth Sounder; Wheel Pilot Compass Display only, Raymarine Wheel Pilot Autopilot-- used only under power so N/A with solar.

PC based GPS navigation with AIS receive. I personally think that this system which uses raster images of the real NOAA charts with all the details, instead of the low-detail charts in the Garmins. It is full featured, with easy to use course and distance, planning, anchor alarm, AIS, etc..

Raytheon VHF

Isotherm BD-35 compressor refrigeration in a very well insulated top-loading box with a small freezer compartment. The freezer section maintains a temp of 15-18deg F, with the main box @ just above freezing.

Propane 3 burner with oven; Aladdin propane tankless hot water

Espar diesel forced-air heat.

1000 watt inverter which we use infrequently. Small vacuum cleaner, small power tools, and a blender for those essential frozen rum drinks.

Our total 24 hour energy budget is 800 -900 WH. During sunny wx, we usually start the day at about 85% SOC. After a typical summer rainy day about 75%. After protracted dark weather, we might fire up our 46 year-old trusty Volvo MD11c for an hour or two @ 1,400 engine rpm using a Sterling Advanced regulator that maintains 50-60A into the batteries throughout the bulk charge. We have a 115A Delco alternator. In our normal cruising we use the engine enough that this is rarely needed. Also the MD11 Volvo is rated at 10hp at 1,400 rpm, so worries about running a diesel with no load aren't a real problem. Our Delco alternator puts out about 50% of its rating without any overheating issues. The Sterling system's controls provide voltage and temperature info as well as a very good charging profile with starting, bulk, timed automatic balancing and float.

This is real-world experience over eight years of active cruising in northern waters. We approached having a comfortable, easy to use system, with an eye to efficiency and reasonable cost. The equipment listed was carefully researched with value and quality in mind always following the Keep It Simple Stupid plan. It is completely possible to equip a medium-sized, diesel-powered cruising sailboat with a very high level of comfort and modern convenience with a modest budget and 200 watts of solar.

[s/v Jedi]

A dedicated controller for each oanel is actually the best setup, but with your panels in an array that is aligned and unshaded like one big panel, it doesn’t provide more output than on one panel. Each panel you have is actually configured as multiple smaller panels (called strings) in series, with a bypass diode for each string.

Assuming you have both controllers installed next to each other, it is very simple to test both panels on one controller and compare daily production. You can even try parallel vs series IF your controller can handle the double voltage

An option would be to switch to a single controller as that would handle your setup, then pack the other in a box and put it in stores as a spare

[Wandering1]

Originally Posted by Nicholson58

We have been living abroad in the Caribbean for eight years. We are always on anchor, never in a marina or at the dock. We have been through several electrical refits and upgrades. This last season we finally reached off grid self sufficiency. Data for ROXY is:

Daily consumption is about 130 amp hours at 26 volts
24 volt Frigaboat freezer, air cooled. Runs 24-7
24 volt Frigaboat refrigerator, air cooled. Runs about 50%
Spectra small output watermaker 6gal/hr, 6 amps @26 volts. 12 hours/week
Watchmate 850 as anchor alarm, 7 watts or less
DC-DC 12 volt power supply runs 24 hr/day
Cabin lighting is all PWM LED. Total power consumption is negligible.
Cooking = propane
VHS radio is on except while we sleep. Idling power is nil.
ICOM SSB 30 watts on a dedicated DC-DC supply is on 10 minutes/day
Raymarine ST60+ wind, depth, tater temperature is always on. Small drain.


Batteries are Blue Heron LiFePo. House and start are in parallel, always on.
House 3 X 210 amp hours = 630 AH@ nominal 24 volts.
Starting 110 amp hours
Total 740 AH @ 26 VDC

3 kw VICTRON charger-inverter is seldom used. Shop vac and big tools
300 watt full sine inverter is seldom used. Charging specialty items and small appliances.

SOLAR

Solar panels were selected with high open circuit voltage in order to maximize MPPT control output.
Three X 220 watts Panels with 54 volts open circuit (VOC) are above the cockpit. Each panel has three circuits connected with diodes. Diode separation minimizes shading issues. The three panels are independently wired through two-pole breakers and then combined in parallel to the MPPT Morningstar solar charge controller. Morningstar output is direct to the main house bank but through a two-pole

On a very good day the MPPT has harvested 830 watts from the 660 watt namerated panels.

The single solar panel at the dinghy davits is 325 watts and it’s separate MPPT charge controller is also wired direct to the main house bank.

The total 985 watts of solar will easily fully charge all of the batteries by mid day including the Frigaboat evaporator system and the watermaker. I try to shut down some of the panels at around 90-95% full charge.

I frequently shut off breakers for some solar panels when we reach full charge early. Sometimes I take the opportunity to run the watermaker with the surplus. We now have the ability to live independently at anchor and also are able to run all day and night under sail without battery worry.

Why not add induction cooking and use up that surplus capacity. No need to get anywhere near 100% charged every day

[Wandering1]

We have 720w of fixed solar and 200w of poor performing flexi panels.
With 585Ah of lithium at 24v we do the vast majority of our cooking on the induction hob. The gas oven gets used occasionally.
The 220v watermaker is run from the 3kw inverter for 15mins each day to make our 50/60 litres of water. We also use the immersion heater for a tank of hot water. We typically harvest 3 to 4.5kw from the solar depending on how much cloud we see. As a back up, we have a 5kVA diesel genset that can run the watermaker, immersion heater or charge the batteries at 115A@24v. We have just gone over 1 month without using the generator.
We will replace the poor performing flexi panels this winter for something better

[Boatwright]

Adding a few details to previous post, in real-world 45deg N conditions, cruising season May to October.

Our inexpensive semi-flexible panels -- now available from Renogy. 100 rated watts @ $140 each from Amazon. These panels have been criticized for poor performance, which is true compared to the better glass glazed ridged panels. However they are cheap and on our boat they do the job with minimal mounting gear required.

We launch in late May, hook up the solar, turn on the refrigeration and a few minor standby loads, and on the mooring the solar handles 100% of the power needed with no worries until we haul out in mid-October.

These panels are about 50% efficient in average conditions, dawn to dusk with some intermittent shading from the rig. Our panels are mounted aft of the boom.

With the sun directly overhead, midday, no shading in early summer we see a peak output of 140 watts from our 200 watt set, 70% of the rating. A thin line of shade from the backstay will reduce midday output to 130 watts.

At home unattended on the mooring, the panels are a popular seagull roost, Seagull s**t degrades performance. We arrange a net of whipping twine from the backstay to the panel frame to interfere with the bird/s landing
maneuvers. This works - forget the plastic owls.

Installing the system required careful planning and a couple of weeks of work. This was concurrent with a complete renewal of our boat's wiring and plumbing, installation of refrigeration, rebuilding of the icebox, new lighting, etc, etc.. Fortunately thanks to our Espar heater, I was able to do a great deal of this work over two winters.

[FlyingScot]

Originally Posted by Boatwright

...
These panels are about 50% efficient in average conditions, dawn to dusk with some intermittent shading from the rig. Our panels are mounted aft of the boom...

A confusing and non standard way to use panel efficiency.

https://www.energy.gov/eere/solar/so...and-efficiency

I think you are tyring to say they make half of the rating. Important but completely different thing.

[Boatwright]

Feel free to correct as some of you will. You are right that efficiency and percentage of panel rating actual output, while related, are not the same thing.

Corrected my post should say: In average summer conditions the panels deliver 50% of their rated output, etc.

Efficiency refers to the % of energy in the incident sunlight converted to electricity. For example: For a given area, glass glazed high performance monocrystalline panels are more efficient than the best semiflexible panels. <or> On a weight basis, semiflexible panels may be more efficient than heavier glass glazed panels, etc.

I also intended easy to understand answers for most folks who are interested in what works for someone who has actually cruised with a low-cost KISS philosophy solar system.

There are other approaches: Kilowatt sized arrays; very large lithium batteries; induction cooking; water-makers; air-conditioning; big freezers; washing machines; Balmar alternators; Gensets; etc.. And lots of theorizing about this and that.

We have chosen simple, and like it.

[newhaul]

Originally Posted by Boatwright

Feel free to correct as some of you will. You are right that efficiency and percentage of panel rating actual output, while related, are not the same thing.

Corrected my post should say: In average summer conditions the panels deliver 50% of their rated output, etc.

Efficiency refers to the % of energy in the incident sunlight converted to electricity. For example: For a given area, glass glazed high performance monocrystalline panels are more efficient than the best semiflexible panels. <or> On a weight basis, semiflexible panels may be more efficient than heavier glass glazed panels, etc.

I also intended easy to understand answers for most folks who are interested in what works for someone who has actually cruised with a low-cost KISS philosophy solar system.

There are other approaches: Kilowatt sized arrays; very large lithium batteries; induction cooking; water-makers; air-conditioning; big freezers; washing machines; Balmar alternators; Gensets; etc.. And lots of theorizing about this and that.

We have chosen simple, and like it.

Honestly IMO you would be way ahead in the game if you were to switch to lifepo4. The next time you need to replace your house bank heck you could get by easily on 200ah .
Considering for longevity sake your 440 of T105s only provides 220ah usable on a regular basis . And 200ah lifepo4 would provide about175ah usable at night and take much better advantage of your available solar. ( myself I would go 300ah)

[Boatwright]

LiPo's would be great and costly. 300 AH Victron - $3,200 + shpg from Defender

Our well cared for Trojans are in their eighth year, are normally never discharged past 75% SOC. We have a battery watering system that enables topping off the electrolyte in a couple of minutes with the squeeze of a hand bulb. They are still going strong with no sign of any significant reduction of capacity. Cost for the set of four about $700 today. In 2026 we paid less than $600.

All batteries, including lithium, have a limited number of cycles. Lithium's also have unresolved thermal runaway issues -- some chemistries safer than others.

For now, no need to change.

[newhaul]

Originally Posted by Boatwright

LiPo's would be great and costly. 300 AH Victron - $3,200 + shpg from Defender

Our well cared for Trojans are in their eighth year, are normally never discharged past 75% SOC. We have a battery watering system that enables topping off the electrolyte in a couple of minutes with the squeeze of a hand bulb. They are still going strong with no sign of any significant reduction of capacity. Cost for the set of four about $700 today. In 2026 we paid less than $600.

All batteries, including lithium, have a limited number of cycles. Lithium's also have unresolved thermal runaway issues -- some chemistries safer than others.

For now, no need to change.

Why victron they are the most overpriced batteries on the market the name is just a sticker .
Hell I can replace your whole 400ah with 400ah li time batteries off of Amazon for under a grand their warranty is just as good as victron or Battleborn.

I built my own bank for 600 all in 250ah .
As to the thermal issue lifepo4 don't have that . They are safer thermally than your Trojans. But your boat your choice . Explosive hydrogen and all.

[Wandering1]

Originally Posted by Boatwright

LiPo's would be great and costly. 300 AH Victron - $3,200 + shpg from Defender

Our well cared for Trojans are in their eighth year, are normally never discharged past 75% SOC. We have a battery watering system that enables topping off the electrolyte in a couple of minutes with the squeeze of a hand bulb. They are still going strong with no sign of any significant reduction of capacity. Cost for the set of four about $700 today. In 2026 we paid less than $600.

All batteries, including lithium, have a limited number of cycles. Lithium's also have unresolved thermal runaway issues -- some chemistries safer than others.

For now, no need to change.

You can build a 280Ah lithium battery for €550 using the best grade A cells and JK BMS. I would be ever go back to my Trojan T105s. Lithium is a different world

[senormechanico]

Originally Posted by newhaul

Honestly IMO you would be way ahead in the game if you were to switch to lifepo4. The next time you need to replace your house bank heck you could get by easily on 200ah .
Considering for longevity sake your 440 of T105s only provides 220ah usable on a regular basis . And 200ah lifepo4 would provide about175ah usable at night and take much better advantage of your available solar. ( myself I would go 300ah)

I did exactly that 13 years ago, and never regretted it for a second.
The cells are still performing at 100%.
Maintenance? If you consider checking the security of the connections about once a year, there's that.

[FlyingScot]

Originally Posted by Boatwright

LiPo's would be great and costly. 300 AH Victron - $3,200 + shpg from Defender

Our well cared for Trojans are in their eighth year, are normally never discharged past 75% SOC. We have a battery watering system that enables topping off the electrolyte in a couple of minutes with the squeeze of a hand bulb. They are still going strong with no sign of any significant reduction of capacity. Cost for the set of four about $700 today. In 2026 we paid less than $600.

All batteries, including lithium, have a limited number of cycles. Lithium's also have unresolved thermal runaway issues -- some chemistries safer than others.

For now, no need to change.

Victron dropped prices on a lot of items in the last year. The best battery they make is on Amazon for $1654 USD. That's 330Ah single battery. You could find it for less, or get 5% back if you use Amazon credit card.

LiFePO4 do not have any more unresolved run away issues than your Trojans. Maybe less so. See what happens when your automatic watering system fails and the batteries overcharge due to a faulty charger.

Not saying Victron Lithium is the answer for you but at least be truthful about the reasons.

[Boatwright]

As to the thermal issue lifepo4 don't have that . They are safer thermally than your Trojans. But your boat your choice . Explosive hydrogen and all.

I am in my late 70's now. If I were to start over Lithium/Iron batteries would be the likely choice. To switch over now would require in addition to the battery: A new inverter/charger; a new alternator regulator; a new BMS; and finding a battery that will fit in the available space.

BTW: Yes, lead acid batteries can be quite dangerous in a short circuit condition. Their low internal resistance can result in very large current flows across the short. I have seen melted screwdrivers and dramatically swollen battery cases from dropped tools, and mis-connected jumper cables. It is incorrect to call this a thermal runaway like what happens to lithium batteries when they short out internally. No matter what your battery chemistry, the safest thing you can do is to have battery terminal fuses per ABYC regs.. Sadly, too many of my fellow sailors who have looked at our system see the terminal fuses (Blue Sea) and ask what they are.

We also have an automatic 12v biscuit fan that ventilates our batteries whenever they are being charged.

This will be my last reply here, as it is getting rather tedious to fuss over who has the "best" set-up. The intent of my original answer to the original question asked in this thread was to provide a real world example of a proven, safe and practical solar system in an older cruising sailboat.

I am also surprised that folks would rather tell me how wrong I am than ask specific questions about things like the power budget of our refrigeration or what software we use for our PC navigation, etc..

[Statistical]

Originally Posted by Boatwright

BTW: Yes, lead acid batteries can be quite dangerous in a short circuit condition. Their low internal resistance can result in very large current flows across the short. I have seen melted screwdrivers and dramatically swollen battery cases from dropped tools, and mis-connected jumper cables. It is incorrect to call this a thermal runaway like what happens to lithium batteries when they short out internally. No matter what your battery chemistry, the safest thing you can do is to have battery terminal fuses per ABYC regs.. Sadly, too many of my fellow sailors who have looked at our system see the terminal fuses (Blue Sea) and ask what they are.

LFP do not have thermal runaway was the point he was making. some non-LFP lithium chemistries like NCA and NMC do.

Side note if you ever do upgrade to LFP those terminal fuses (MBRF) need to go. They may be the safest option for FLA or AGM but they lack the AIC (current limiting) needed for LFP.

LiPo's would be great and costly.

LiPo are something completely different and nobody is proposing using them on boats. Normally I wouldn't be pedantic but when you use incorrect term and them associate incorrect behavior then in this case maybe incorrect terminology is leads to incorrect understanding.