Basic solar system advice - max power on a budget

[rbyham]

So I own a Catalina 36 with currently a minimal solar system consisting of a 120watt panel running to a cheapo Amazon/China PCM controller which then feeds a two bank battery system each bank comprised of 2 6v golf cart batteries of 215ah each in series. I am a weekend cruiser occasionally stretching to a week with onboard refrigeration, 3 fans, lights, and 2 pumps being main power draws. I can typically make it a weekend if I run the diesel or an onboard Honda 2000i somewhere along the way. I would like to feel confident for a 4-5 day cruise without needing anything other than my batteries.

My 500lb rated davits currently house the 120 watt panel and with minimal tweaking could easily hold some of the larger (80x40) panels I am seeing in the 420w range. That placement is near perfect as there is zero shading.

Assuming a single large panel is the way to go and for the time being at least my 2 bank battery setup, can anyone recommend what the rest of the system needs to look like? I am thinking some version of mppt controller, some fusing, and a monitor of some sort but the myriad of options and specs make my eyes glaze over.

Also I am a 45 minute drive from SanTan solar in Savannah GA who have both new and used panels in the 420w range for a budget conscious guy like me. They recently had used LG420w panels advertized at $140 and they frequently have deals like that available.

Thanks in advance for any help from thihs knowledgeable group.

[GILow]

Single panels are not the best option for a sailing boat. (Unless something has changed in the last few years.). Systematic testing by credible amateurs has demonstrated that the losses due to shading from the rig can be reduced by having a greater number of smaller panels rather than a few big panels.

As someone who has managed to live entirely on solar power for my boat at reasonably high latitudes I can also advocate a setup involving multiple controllers, one for each panel if possible.

And, of course, Victron MPPT smart controllers really are unbeatable.

I’ve never seen a satisfactory setup that involved cheap controllers from EBay. All have either produced minuscule amounts of power or have destroyed the batteries with poor charging algorithms. (I repair boat electrics now as part of my living, so I see a LOT of these installations.)

In your situation I would try to find a ways of maximising the area of panels on the davits using two or three smaller panels, and give each its own controller.

Also, don’t dismiss the idea of wing panels on the aft safety rails if practical. These can be deployed at anchor and remain stowed when under way. At least one member here has sailed the southern ocean with a wing panel setup.

Finally, don’t waste your money on flexible panels. I’m yet to see any that last even two years in the Australian sun.

P.S. regarding the rest of the system, a Victron Smartsense attached to the batteries and a Victron BMS will give you a totally integrated, reliable and future proof solar charging system for a very reasonable cost.

[smac999]

400-500 watts of solar., victron Mppt's. put the 4 batteries into one house bank and add a group 27 start battery. having 2 golf carts as the start makes no sense. get a victron bvm 712 or smart shunt.

leave the honda at home. it has no place on a boat, ever.

[Franziska]

Use rigid industrial panels instead of marine panels.
They come in different sizes.

We have 3 Trina Solar Vertex S 400W panels, each with its own dedicated Epever Solar controller. No need to buy expensive Victron stuff if you are on a budget.
These panels are much cheaper than dedicated marine panels and made to withstand high winds, vibration and saltspray. They are often mounted along highways where they are subjected to all of the above.

The Honda is great to have when in a pinch.
We have a similar 2500w genset as backup. Mounted under a dedicated housing (gets removed when in use) in the cockpit.
Zero problems with it. Just don't use it inside.

Cheapest battery at this day and age when looking at power to cost ratio is a DIY LiFePo4 setup built with from individual cells, provided you have the skills to built it. Looks daunting at the start bit is less complicated when you actually do it.
Drop in replacements with built in BMS are much much more expensive though.

We live full time onboard and have a DIY 840Ah LiFePo4 setup with Daly BMS. Works great, no problems.
Due to the DIY setup you can built the battery system suited to your needs.

[onewadd]

Originally Posted by smac999

400-500 watts of solar., victron Mppt's. put the 4 batteries into one house bank and add a group 27 start battery. having 2 golf carts as the start makes no sense. get a victron bvm 712 or smart shunt.

leave the honda at home. it has no place on a boat, ever.

Just asking.... why the hateful comment about the Honda. It really does a very good job quite safely. BTW, imho.

[GILow]

Originally Posted by onewadd

Just asking.... why the hateful comment about the Honda. It really does a very good job quite safely. BTW, imho.

Absolutely a bad idea to have carbon monoxide producing devices on boats if you can avoid it.

[Pete7]

If the 420w LG panels are still available and have a recent date on them that would be nice. LG no longer make solar panels because they were made in Taiwan and cheaper Chinese panels swamped the market so selling higher quality panels difficult.

AT 32 degrees N, that should produce all the power you need. We spent a couple of years with 300w of solar which not only ran the boat but also a really good mix of electric cooking plus fridge only topped off with gas occasionally. We now have 600w.

Use this to work out how much power they will develop each month in Savannah https://en.sunware.solar/systemsize/daily_yield#tabelle

If you are weekend sailing, you do not need lots of kit. However a Victron 100/30 MPPT with blue tooth would be a nice fit. Add a simple pure sine wave inverter say 2000w to run power tools, hoover or induction hob and you will be well away. We even use a mains electric pump to inflate the dinghy.

We tend to use Sterling but there are others like Pro Mariner in the US but make sure its pure sine wave.

Finally the Victron BMV battery monitored was mentioned which would be nice but expensive. Any suitable shunt and display will do from about $50 to see what is going on with charging or discharging etc.

Oh and wire the 4 x 6v batteries into one 12v bank as SMAC suggested. They will thank you for it.

Us with 300w.

Pete

[Franziska]

Originally Posted by GILow

Absolutely a bad idea to have carbon monoxide producing devices on boats if you can avoid it.

Don't see any issue if one attaches an exhaust to it and is not stupid enough to use it inside.
Your engine produces carbon monoxide, too. The exhaust takes care of it.

[Mike OReilly]

I prefer multiple panels, run in parallel. A small amount of shading can have a large impact on any one panel, and shading is a constant challenge on any sailboat. So dividing your panels is probably best.

We spend long periods of time at anchor, with little or no dino-charging. My system consists of 400 watts, produced by four panels, all run in parallel to a single MPPT (victron) controller. The optimal setup would have each panel on its own controller, but this adds complexity and cost to the system. I don’t know how much I lose by using only one controller, but it seems inconsequential.

I do carry a portable gas generator; a 1000 watt Yamaha. CO is not a problem. It comes into service if we’ve had a run of heavy overcast weather, accompanied with little wind — we also have a wind generator. Solar accounts for ~85% of my power needs when at anchor, with wind picking up the rest.

[GILow]

Originally Posted by Franziska

Don't see any issue if one attaches an exhaust to it and is not stupid enough to use it inside.
Your engine produces carbon monoxide, too. The exhaust takes care of it.

All valid points. But poor consolation to those have died of CO poisoning on boats.

Personally, the most tragic account I read was of a semi recent event in Tasmania where, if I read it correctly, the boat owner was air lifted off the boat after his daughter became quite ill. Friends sailed the boat back home for him but were not aware of the risks associated with the use of the generator and at least two people died.

I might have got some of the details wrong, but it serves to underline the unpredictable nature of these things. Probably the owner knew exactly how to safely use the system but unexpected events took that critical knowledge away when it mattered.

I do really stand by the logic that it is good to AVOID adding a CO risk to boat if you can. Sure, it may be your only choice, in which case a well thought out, well installed and well alarmed system is the go.

Otherwise, seek alternatives.

And if one of my solar panels falls off, drops on my head and kills me stone dead you have my permission to laugh out loud at the irony. I promise I won’t haunt you.

[Stu Jackson]

Originally Posted by rbyham

...a two bank battery system each bank comprised of 2 6v golf cart batteries of 215ah each in series.
...
I would like to feel confident for a 4-5 day cruise without needing anything other than my batteries.
...

Ditch the two bank system for your cruise requirements. One larger bank is always better. Add a reserve bank of a single start battery and gang your two separate banks together.


Here's why:


IS IT BETTER TO HAVE ONE OR TWO BATTERY BANKS FOR HOUSE USE?
(By Nigel Calder - I DIDN’T write this!!!)

This appears in Calder’s excellent Boatowners Manual. I bought the 2nd edition in 1998.

The [formerly – pre-1990s] popular arrangement of having two house banks alternated in use needs scrutiny before I go any further.

LIFE CYCLES: As we have seen, the life expectancy of a battery in cycling service is directly related to the depth to which it is discharged at each cycle - the greater the depth of discharge, the shorter the battery’s life.

This relationship between depth of discharge and battery life is NOT linear. As the depth of discharge increases, a battery’s life expectancy is disproportionately shortened. A given battery may cycle through 10% of its capacity 2,000 times, 50% of its capacity 300 times and 100% of its capacity around 100 times.

Let’s say, for arguments sake, that a boat has two 200-ah battery banks, alternated from day to day, with a daily load of 80 Ah. Each bank will be discharged by 40% (80 Ah of one of the two 200 Ah banks) of its capacity before being recharged. The batteries will fail after 380 cycles, which is 760 days (since each is used every other day). If the two banks had been wired in parallel, to make a single 400 Ah battery bank, this bank would have been discharged by 20% of capacity every day, with a life expectancy of 800 days, a 5% increase in life expectancy using exactly the same batteries!

But now let’s double the capacity of the batteries, so that the boat has either two 400 Ah banks, or a single 800 Ah bank, but with the same 80 Ah daily load. The two separate banks will be cycling through 20% of capacity every other day, resulting in a total life expectancy of 1,600 days. Doubling the size of the battery banks in relation to the load has produced a 210% increase in life expectancy. The single 800 Ah bank will be cycling through 10% of capacity every day, resulting in a life expectancy of 2,000 days - a 25% increase in life expectancy over the two (400 Ah) banks, and a 250% increase in life expectancy over the single 400 Ah battery bank!

There are two immediate conclusions to be drawn from these figures:

1. For a given total battery capacity, wiring the (house) batteries into a single high capacity bank, rather than having them divided into two alternating banks, will result in a longer overall life expectancy for the batteries.

2. All other things being equal, any increase in the overall capacity of a battery bank will produce a disproportionate increase in its life expectancy (through reducing the depth of discharge at each cycle).

FOR BATTERY LONGEVITY, A SINGLE LARGE (HOUSE) BANK, THE LARGER THE BETTER, IS PREFERABLE TO DIVIDED (HOUSE) BANKS.

[George_SD]

This is odd. I have a single 100w panel, Renogy Wonderer PWM, 3x100AH 12v batteries (but solar feeds only 2 in the house bank). I run 2 fridges (24x7), fresh water pump, gas solenoid and lights in the evening. I have not ran out of power and did not need to run the engine, provided it's sunny outside.

It really comes down to your usage and how far you deplete the batteries (remember - solar typically doesn't feed anything, just recharges the batteries). So you need to ensure you have a big enough bank (single) for house loads. I would imagine that a single 420w panel should be able to recharge a bank big enough to serve your needs.

[rbyham]

Much thanks here folks. Lots of helpful info. I hear the advice to go multi panel. However the davit setup is almost perfectly ready to add one large panel plus I get zero shading ever in that area. I also want to explore the thoughts here about combining my current two banks and adding a start battery. I am pretty set on thee victron mppt controller. As to the Honda it gets worse for the CO concerned folks. The main reason the Honda is onboard is so I can cruise more in our hotter months and sleep with A/C at night. It easily powers a 10.5k A/C newly installed a few months ago.

[GreenWave]

Originally Posted by rbyham

Much thanks here folks. Lots of helpful info. I hear the advice to go multi panel. However the davit setup is almost perfectly ready to add one large panel plus I get zero shading ever in that area. I also want to explore the thoughts here about combining my current two banks and adding a start battery. I am pretty set on thee victron mppt controller. As to the Honda it gets worse for the CO concerned folks. The main reason the Honda is onboard is so I can cruise more in our hotter months and sleep with A/C at night. It easily powers a 10.5k A/C newly installed a few months ago.

Which Honda do you have again? And what kind of run time per gallon of gas do you get typically?

[Kettlewell]

I second Stu Jackson on merging your two battery banks. I then use a regular WalMart marine GP24 starting battery that does nothing else and gets trickle charged from the main bank. I've been using a TrikLStart to do that.