diy solar

diy solar

Solar enthusiast trying to replace diesel generator on yacht

Since I’m running both engines, each with an alternator, I suspect I’m not using a huge amount of energy they output. They are tied into the original battery isolator, which I’m sure is the old diode type, which I understand wastes even more energy.
So based on your comments, here’s what I’m thinking. Replace one of my alternators with a high output, 24V, regulated alternator which can directly charge the lithium banks. Keep the other 12V alternator in place to charge the house battery bank…no need for a battery isolator? Does that make sense, or is there a better solution?
 
Nothing definitive yet. My first step is to measure the ambient temperature in the engine room while underway to see if the environment is too hot for locating the LiFePO4 battery banks there. The twin Diesel engines generate lots of heat, but there might be adequate ventilation to keep the temps below 40 C while cruising.

If that test reveals that the LiFePO4 batteries would be ok in the engine room, I‘ll buy the 3.2V cells off Aliexpress to build my own 24V bank.

Still trying to decide whether to charge the lithium banks with a 24V alternator (they are expensive…about $1200 with external regulator), or put 1200W solar on the roof, or both. I’m leaning towards the 24V alternator, as the installation would be straightforward (ha, I just jinxed myself).

Does anyone know if the Balmar external regulator from the 24V alternator could charge the lithium bank directly. Seems I read that one can set the regulator output specifically for lithium.
 
If that test reveals that the LiFePO4 batteries would be ok in the engine room, I‘ll buy the 3.2V cells off Aliexpress to build my own 24V bank.
So you have decided on 24 volts?
Sorry was conflating 2 very different builds.
 
No, it has nothing to do with the propulsion system…I have a pair of 375 HP Caterpillar engines for propulsion. 24V battery bank seems the one most recommended for solar/off grid generators.
 
As far as 24V alternator: do not lose the 12V redundancy. It’s generally not difficult to add a second alternator to one engine- that would be best; system integrity and redundancy, good 24V accessory charging.

I’d probably still put some solar in place. Nobody has ever said, “wow, I just wish my batteries would discharge more.”
 
I’d probably still put some solar in place. Nobody has ever said, “wow, I just wish my batteries would discharge more.”
But think about it: if you want to charge efficiently 24V batteries from solar with MPPT, you need at least 36Vmp panels, the higher voltage, the better.
With smaller panels ~100W that are usually 18Vmp you may use boost MPPT controllers. e.g. that one : boost MPPT controler
On a boat, it is better to use paralleled panels, when you have to deal with shades.
 
Oh man I'm curious now.

With two alts and DC chargers you could put a lot of power into a battery bank pretty quickly, to the point where the solar essentially becomes the backup just with normal cruising time.

Even if it's a matter of upgraded alternators.
There's a lot of potential there.

I know enough about boats to know they're cool and I have no business working on their electrical but I'm still gonna comment to get notifications on your progress.

Share some photos if you are willing to?
 
you could put a lot of power into a battery bank pretty quickly, to the point where the solar essentially becomes the backup just with normal cruising time
Exactly! If you anchor off at noon and set on the hook for a day or two, the limited solar could potentially keep the batteries from not lasting through the peaceful two-day mini vaca is what I was thinking.
Plus when tied up it can keep the batteries on float reducing your carbon flip-flop footprint.
 
For a backup it will be too weak, but to keep the batteries at float, the solar might be useful.
I mean. He did say up to 1200w of panels. That's hardly "weak".

Even 800w of solar is a useful amount of power if you're capable of cutting back during the hard times.

Let me tell you how h'wat. 800w coming in would be a gross luxury for my setup. Hell. I'd have an ice maker.
 
If you want to do this correctly:

Go 48V. Add a 100A 48V Balmar 96 series alternator to each engine. Use that to charge a 48V house battery pack of suitable size to get the capacity you need - as you mentioned 2 days without shore/engines running.

We do these installs all the time into older boats like yours. Great setup to get some better usability out of them.

Combined with a pair of Quattros and you can get reliable shore charging as well under all the shitty conditions you might find at a marina. Marina's typically have worse power than RV parks!

You can also add a couple panels to help recoup some power during days you are not running engines or on shore power; but don't expect miracles here.

A small generator is also never a bad thing to have if you are somewhere without shore power, rough seas, and no solar -- running the generator is a way to keep things functional.

Read this for more insight: https://www.balmar.net/wp-content/u...UDY-Silent-Running-A-Case-for-48V-Systems.pdf
 
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I mean. He did say up to 1200w of panels. That's hardly "weak".

Even 800w of solar is a useful amount of power if you're capable of cutting back during the hard times.

Let me tell you how h'wat. 800w coming in would be a gross luxury for my setup. Hell. I'd have an ice maker.
1200W of panels on a boat will pretty never produce 1200W.
And never ever that power over 24H a day!
On a boat, you are not controlling the orientation of the panels, and have plenty of shades...
Expect reasonably 1Kwh per day, maybe 2Kwh on average...
 
1200W of panels on a boat will pretty never produce 1200W.
And never ever that power over 24H a day!
On a boat, you are not controlling the orientation of the panels, and have plenty of shades...
Expect reasonably 1Kwh per day, maybe 2Kwh on average...
I'm aware. That's why I talked about 800w.

You're really on the wrong forum if you are going to sit here and argue against the merits of solar or whether that's useful at night.

Even 400 watts of solar for a few hours during the day is enough to keep a medium size refrigerator cold and a ventilation fan running 24 hours without issue.

That said, 1kwh a day from 1200 of solar? Lmao I get more than half that from 150w of solar while spending the morning in the shade. You're way off base.
 
400 watts of solar for a few hours during the day is enough to keep a medium size refrigerator cold
Agreed. I’m running everything on 400W right now. Basically vertical, too!
Includes a small-medium fridge. I do get sun all day (barring cloudy days), however.

^^^ a hardtop cruiser like OP’s will not have much shade. Even flat panels on a dinghy like that would put out pretty good imho. 3s3p would probably be much more impressive than expected. Minus the bird leavings.
 
Why put the lithium in the engine room? Why not with the house bank?
As for batteries, get GOOD ones.
Designed for use in RV or boats.
I would not recommend "blue sleeve" cells and diy... go with high capacity packaged sets. Warranty, and marine rated. I wouldn't go with a growatt or mpp either.
Victron, sol-arc etc... you want DEPENDABLE solid low frequency transformer based systems.
And even with a dedicated 24v alternator, you still want a dc to dc controller. No alternator can handle the discharge demand of lithium cells.
 
You're really on the wrong forum if you are going to sit here and argue against the merits of solar or whether that's useful at night.
I am just recommending to plan conservatively: rainy days with 5% output exist and on a boat you don't control orientation.
Even the thin shade of the pole from the yacht anchored next to you may be enough to jeopardize your harvesting.
 
As the OP, I am overwhelmed with the gamut of ideas you all have shared. Thanks a bunch! I shared some of them with my first mate (wife), and she is supportive to make the transition to electric generation. Happy wife…happy boating!

Some observations and questions:

1. I measured the ambient temperature in the engine room yesterday while cruising, it was 90 F, on a 85 degree day. That suggests that there is adequate ventilation in the engine room, and would not be oppressive to LiFePO4 cells. BTW, my house batteries (Lead Acid) are in the engine room as well, which is really the only location for battery banks.

2. I have a 6’ x 12.5’ flat, unshaded roof on my boat, so I think I could mount some substantial solar panels up there. Question: what would be the optimal size and arrangement to charge a lithium bank?

3. 12V, 24V, 48V system? People have differing opinions on this. My boat is 12V wired, as well as 12V alternators. Is going to 24V or 48V that much more efficient to warrant buying extra equipment to make the voltage conversions?

4. Batteries: do I really need to buy marine lithium batteries? They seem twice the price as building and creating one’s own from the prismatic cells, which also are available at higher Ahr capacities.
 
As the OP, I am overwhelmed with the gamut of ideas you all have shared. Thanks a bunch! I shared some of them with my first mate (wife), and she is supportive to make the transition to electric generation. Happy wife…happy boating!

Some observations and questions:

1. I measured the ambient temperature in the engine room yesterday while cruising, it was 90 F, on a 85 degree day. That suggests that there is adequate ventilation in the engine room, and would not be oppressive to LiFePO4 cells. BTW, my house batteries (Lead Acid) are in the engine room as well, which is really the only location for battery banks.

2. I have a 6’ x 12.5’ flat, unshaded roof on my boat, so I think I could mount some substantial solar panels up there. Question: what would be the optimal size and arrangement to charge a lithium bank?

3. 12V, 24V, 48V system? People have differing opinions on this. My boat is 12V wired, as well as 12V alternators. Is going to 24V or 48V that much more efficient to warrant buying extra equipment to make the voltage conversions?

4. Batteries: do I really need to buy marine lithium batteries? They seem twice the price as building and creating one’s own from the prismatic cells, which also are available at higher Ahr capacities.

1) Engine room is not a great place for house batteries for many reasons, heat being one of them. If you can find somewhere else it is preferable. If you can't you need to ensure the temps are kept under the limits for the batteries you are using. Note you battery life will be degraded at their max temps.

2) Sounds like plenty of space. I suggest as much solar as you can reasonably fit. Stainless unistrut works well for such retrofits with selective bolting to existing structure with suitable doublers, etc.

3) Read the link I attached above. Some real benefits to going to 48V in efficiency, cable size, alternator efficiency, etc. Since you were talking about adding 24V it would cost about the same, perhaps a bit less, to do 48V instead. It would be a no-brainer to go 48V unless you already had all the 24V equipment.

4) Can prismatic cells work? Certainly. if you go this route then #1 is even more important to keep the cells well inside their operating range, as well as a properly designed battery box with compression, etc, etc. I see a lot more Winston cells then the blue wrapped cells in use in marine applications.

Other:

You can keep your existing 12V invertor as the emergency backup to save a few bucks, and therefore only need one new 48V unit. Go Victron if possible as it will give you years of trouble free operation if setup properly. I'd also do a Victron SCC and Cerbo to monitor it all.

Depending on what 12V loads you have a 48V to 12V convertor might be an option to power them as well without having to swap stuff out.
 
If you use a lot of 120V stuff for extended periods and at high Amperage it’s pretty reasonable to decide on 48V storage.

However, if you don’t need/use a lot of 120VAC and your typical 120V demand is under 10A tops or maybe even 15A, a 12V battery bank can make sense in my opinion. Because everything is already set up that way. If it’s working fine now at 12V it will be at least as good probably better with new technology.

The panels on the other hand… a charge controller that can handle 24V, 48V, or even (96) 100V and output that to charge 12, 24, or 48V is really not difficult, not that much more expensive (likely less), and doesn’t make sense to do otherwise. You could series/parallel for two, three or four ‘groups’ of matching panels and get redundancy and tons of power. (Which is what I would do.)
 
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