Challenges with Solar on boats

[Pelagic]

I guess all boats have different priorities on Start and House battery design, based on thier layout and size.

For sailboats in the 45 to 65 ft range, my basic understanding was that you placed the Start battery (often 24V) as close to main engine as possible for better cold cranking power due to minimal cable runs.

That those Start Batteries were chosen for their high cranking power more so than the deep cycle capabilities needed for a house bank large charge/deep discharge scenario. So often, were a different model than the House Bank battery.

That while the Start Bank would be further aft in the engine room, .....if possible it was recommended to keep the larger House Bank more centralised midships for better weight distribution and to minimize cable runs and sizes fore and aft to the many consumers..

For isolation and backup, the Start Battery had an on off switch to main engine and an Emergency Parallel switch to the House Bank buss bars.

Many options on how to best charge the two different battery banks, but a simple regulated and dedicated small alternator for Start would quickly charge after starting, but a 2nd smarter, larger more powerful engine driven alternater that would have maximum output at motor sailing RPM (1000 to 1300 rpm) provided the simplest option for quickly recharging House Bank under power when motor sailing.

What am I missing here??

[ramblinrod]

Originally Posted by Pelagic

I guess all boats have different priorities on Start and House battery design, based on thier layout and size.

For sailboats in the 45 to 65 ft range, my basic understanding was that you placed the Start battery (often 24V) as close to main engine as possible for better cold cranking power due to minimal cable runs.

That those Start Batteries were chosen for their high cranking power more so than the deep cycle capabilities needed for a house bank large charge/deep discharge scenario. So often, were a different model than the House Bank battery.

That while the Start Bank would be further aft in the engine room, .....if possible it was recommended to keep the larger House Bank more centralised midships for better weight distribution and to minimize cable runs and sizes fore and aft to the many consumers..

For isolation and backup, the Start Battery had an on off switch to main engine and an Emergency Parallel switch to the House Bank buss bars.

Many options on how to best charge the two different battery banks, but a simple regulated and dedicated small alternator for Start would quickly charge after starting, but a 2nd smarter, larger more powerful engine driven alternater that would have maximum output at motor sailing RPM (1000 to 1300 rpm) provided the simplest option for quickly recharging House Bank under power when motor sailing.

What am I missing here??

I am not sure what the question is?

There are all kinds of things missing, as your first sentence, in general, covers everything, but then the balance is quite specific and may not apply to all.

First, the boating community at large, this forum, and a battery discussion, is much broader than for just 45 - 65 ft sailboats, so you missed about 98% of the vessels on the water today.

Next, of the narrow field defined, there are all kinds of variables missed.

For example, windlass, bow thruster, electric winch batteries.

Some believe (myself included) that house banks should not be in unventilated space under berths and settees.

Some believe (myself included) that storage space in the main salon under the settees is too valuable for daily accessed stores, to load with batteries that only require access infrequently (or as often in the case of modern production boats, tankage).

Historically, sailing vessels with long overhangs were subject to heeling and hobby-horsing (CCA era) if all heavy items weren't located low and central. With modern designs, with flatter bottoms and that carry so much beam aft, not so important.

There are tons of variables.

In my case, the vessel (32 ft) was built with integral boxes for 4 x Grp 24 12Vdc DC batteries, in the starboard cockpit locker, most forward, balancing the diesel tank and water heater in same location to port. They are way higher and less central than I would like, but they fit, are out of the cabin, and don't take up valuable storage space better suited for frequently accessed items.

Everything is a compromise, and there really is no right or wrong, just what is, what isn't, and personal preference.

[hellosailor]

pelagic-
What you are missing is that this is a mass market. A small mass market (does the phrase "giant prawns" sound familiar?(G) but still very much one of production line boats, where the manufacturers try to make "one size fits all" in order to maximize their profits across the entire line.
One design, one alternator not two, and two sets of mounts and wires and wiring time as well. Something cheap and mainly able to do the job for most customers at the least cost.
What you are discussing are engineering issues, and engineering takes a second seat to marketing considerations every time, unless you are building bespoke products for an even more limited and pricey audience.
Bear in mind, 90% of the recreational sailboats are what, under 28' OAL? You think that allows for batteries amidship, at all? Or two alternators on two brackets in the tiny engine space?
Very different from the buyers of new 65' boats, who might, just maybe, have some appreciation for the design issues and be willing to pay for the really higher costs of custom design and assembly, which impact a lot more than just running a few feet of cable and some extra parts.

[Pelagic]

Thanks guys... I did wax on a bit too much [emoji56]
My key question was:
....shouldn't the start Battery be as close to the main engine as possible?

Agree that having batteries venting in the main salon is not good..
.when I first bought Stargazer in 2004 she had 4 x 200ah D type 12v refillable wet cells and you really knew when they were charging!

But I thought the problem was that the Bank was far too small for the loads and was being discharged too much each night.
(confirmed after installing a smart gauge)

So I upped the number to 8 x D type AGM each at 240Ah (series/parallel)

After that, i have never smelled any venting fumes.
Don't know if it is because of the switch to AGMs or that I now maintain a much higher SOC before charging?

Also, as I don't need to access for topping up water, I was able to concentrate all 8 in a smaller footprint on two levels (seat locker and sub floor underneath)
very close to the electrical locker and bus bars.

[john61ct]

wrt loads, put in big-enough gauge wiring, anything can be far from anything as far as power loss & voltage drop is concerned. But huge amps, gotta be careful re chafing vibration etc

Your call when it gets impractical or too expensive.

Charge **sources** however, should be getting a good temp reading for the batts

[hellosailor]

"Don't know if it is because of the switch to AGMs or that I now maintain a much higher SOC before charging?"
AGM's are one type of sealed-valve-regulated lead acid battery. Key word, SEALED. In normal use, you can never smell them because nothing can get in or out of the battery except electricity. If you try really hard, you can overheat them, build up too much internal gas pressure during charging, and then they will blow a spring-loaded safety valve and make a stink, and a gust of unpleasant "steam". And if you keep trying really really hard, you can probably turn that into a dramatic melt-down, too.(G)

AGM's vary in their capacity to recombine hydrogen and oxygen (which are given off as the electrolyte "boils" during hot charging) but if you were frequently boiling the electrolyte in the wet cells, you'd want to check the charge rate for the AGM's as well.

[Pelagic]

Thanks for that Hellosailer.

When I upsized my 24V House Bank from 400Ah to 8 x Fullriver 260Ah AGM's (= 1040Ah @ 24V), my thought was to have enough capacity so as to only consume about 10% in 24 hrs at anchor.

That calculation worked out , so it allowed me to minimize my charge time at Anchor with generator to about 2hrs if I kept the SOC in the 70-80% realm for bulk charging.

I have 2 x 24v Victron chargers
70a & 50a. Tests show that I should start with both then shut down the 50a @ about 75% SOC

Now that I have installed 4 x 327W Sunpower panels, it will be interesting to see how that affects my charging profile when we move back on board after the Rainy/Typhoon Season and get cruising again

[atlantical]

I am running two batteries, one thirty watt panel, all lights LED so don't use much power, besides have shore power. Battery one is connected to the solar, to charge both batteries I switch the main switch to both and feed the charge through the battery cables. One battery charges to a higher voltage than the other, so when I charge both, the voltage in the high battery drops.

I have also had problems with a previous solar controller that was not waterproof, the circuit board stopped working as it became crusted in salt.

Other than that, no problems, well, where to put the solar panel is always a problem, I did want to get another and double up the power, but don't really have space for it, canoe stern, my panel goes just forward of the companion way hatch lid.

[witzgall]

Where was your solar controller mounted, that it got encrusted with salt? Was it from water ingress, or simply salt air?

Chris

Originally Posted by atlantical

I am running two batteries, one thirty watt panel, all lights LED so don't use much power, besides have shore power. Battery one is connected to the solar, to charge both batteries I switch the main switch to both and feed the charge through the battery cables. One battery charges to a higher voltage than the other, so when I charge both, the voltage in the high battery drops.

I have also had problems with a previous solar controller that was not waterproof, the circuit board stopped working as it became crusted in salt.

Other than that, no problems, well, where to put the solar panel is always a problem, I did want to get another and double up the power, but don't really have space for it, canoe stern, my panel goes just forward of the companion way hatch lid.

[Firestorm]

Originally Posted by downunder

Clearly newhaul you are a tiny panel man. Thats your choice.

By the same token if you have 2X 300w panels and one fails you still have 300 watts until you replace it. principle is the same.

I guess I'm with newhaul on this one. I only have room for 3 100 watt panels on my canvas bimini. Bottom line, if you have room for heavy 300 watt panels, good for you. However, for many of us (especially sailors on 40 footers ) 100 watt panels are often the only choice without spending $5k to $10K on ugly stainless framing. Just my opinion.

Cheers.

[Firestorm]

Originally Posted by a64pilot

I don't believe that if your wired in parallel that shade on one panel significantly affects the others, or at least on my installation it doesn't seem to. I have four wired to a combiner box and an Outback 80, I have shading issues but will see 300+ AH on a good day.
However I can see having multiple controllers gives redundancy, if I lose my Outback 80, I lose the whole system

Good point on the loss of a controller. Why not just carry an extra controller in you spare parts? I carry a spare alternator, among many other spares.

Cheers.

[socaldmax]

Because many cruisers are too cheap to buy an MPPT controller @ $90-$100 ea, much less an Outback 80 @ $580 plus tax, so a spare Outback 80 at over $600 would be even farther out of the question.

That's why I like the 20A controller I use for $100. I've never had one fail, but a spare one would only cost $100.

[CapnCrunch]

Hi All:
I've read all 13 pages of this very interesting thread and thought I would float my plan and questions past y'all. I am outfitting a Lancer 44' motorsailor with two perkins 236 diesels. I pulled out the diesel genny and current plan is to have a house bank with one start battery for each engine. I will charge these via 3x 290w (rated at 32v and 9.0A) panels charging via two Blue Sea ACRs and 3x victron 75/15 MPPTs. As a firm believer in overkill and redundancy, I will prolly add a wind genny (not sure what make or cap., yet) with its own controller. And, of course, will have the use of the engine alternators. I will be using a victron 702 monitor. I am wondering if I'm likely to run into any problems during those times when all 3 sources would be charging the batteries.

Also, I read somewhere that the MPPTs can produce significant amounts of heat at times. Is this true and how much of a concern is this in mounting location considering that they should be mounted near the batteries?

Also, with regard to shading on solar panels, does the shadow of a mast, for example, kill the output of the panel or just reduce it?

Any suggestions or criticisms will be appreciated.

[mitiempo]

Originally Posted by CapnCrunch

Hi All:
I've read all 13 pages of this very interesting thread and thought I would float my plan and questions past y'all. I am outfitting a Lancer 44' motorsailor with two perkins 236 diesels. I pulled out the diesel genny and current plan is to have a house bank with one start battery for each engine. I will charge these via 3x 290w (rated at 32v and 9.0A) panels charging via two Blue Sea ACRs and 3x victron 75/15 MPPTs. As a firm believer in overkill and redundancy, I will prolly add a wind genny (not sure what make or cap., yet) with its own controller. And, of course, will have the use of the engine alternators. I will be using a victron 702 monitor. I am wondering if I'm likely to run into any problems during those times when all 3 sources would be charging the batteries.

Also, I read somewhere that the MPPTs can produce significant amounts of heat at times. Is this true and how much of a concern is this in mounting location considering that they should be mounted near the batteries?

Also, with regard to shading on solar panels, does the shadow of a mast, for example, kill the output of the panel or just reduce it?

Any suggestions or criticisms will be appreciated.

For a start the Victron 75/15 is rated for a maximum of 200 watts. At this maximum the output will reach just under 14 amps in ideal conditions.

Better to use the Victron 100/30 for your panels. It's max is 440 watts.

I have always wondered why twin engine boats use a start battery for each engine. One capable battery will easily start both engines and results in one less bank to deal with as well as being less expensive. As far as redundancy you will have a house bank for emergencies. If you still want 2 start batteries parallel them and use the pair to start each engine.

Shouldn't run into problems charging. In bulk the charge sources will see battery voltage, not each other. When the set point (absorption voltage) is reached one source or another will go into float but by then the bank is accepting very little current so it really shouldn't make any difference.

As far as shading it depends on panel cell layout as well as how much shading. You will certainly lose some output but slight shading will reduce not kill the output. Best to keep the panels as shade free as possible in any case.

[CapnCrunch]

Originally Posted by mitiempo

For a start the Victron 75/15 is rated for a maximum of 200 watts. At this maximum the output will reach just under 14 amps in ideal conditions.

I'm not getting this. The Victron 100/15 specs read "Maximum PV power, 12V 1a,b): 200W (MPPT range 15V to 100V)"

My 290w panel specs show "Voc = 38.8VDC/ Isc = 9.58 A. I thought the Victron model numbers represented Voc/Isc?

If panel wattage is the determining factor, it looks like I would have go to the 150/35 at a cost of $295 ea vs. $90 ea for the 75/15. And, since the 150/35 is rated for 650W, I would need two of them . The damned panels only cost $175 ea, so I would be spending more for the controllers than for the panels.

As for your question about start batteries, for me, it always came down to the "oh s**t" factor. If one of two batteries in parallel went bad, it drags the other down with it. Whereas, if a single batty goes bad, I can always jump off the other if I need to start the engine quickly.