diy solar

diy solar

Same old question...

Hillbillybuddha

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I've looked through a bunch of threads and there have been a lot of threads on this.

My boat has almost nothing right now. Nav lights, a couple interior lights, a VHF Radio, a depth sounder. It runs off the start battery and uses the alternator as its only charging system.

I'm transitioning from a day sailor back to a live aboard (live aboard was on a different boat)

So I'm going to add, over time, the conveniences of life. A refrigerator, radar, Autopilot, fans, electric windlass, a computer, AIS, MFD, a couple water pumps (salt water, fresh water, deck wash down), you know, cruising stuff.

I was thinking I'd start with 400ah LFP and 600w solar and probably a small wind gen and a small Honda style gas gen (just in case). Does this seem like a reasonable amount of power to start with? What do I need to know about keeping the system expandable?

I know the answer is depends on how much power I use, but I have nothing to gauge that on.
 
What do I need to know about keeping the system expandable?
"expandable" can be interpreted in a lot of ways.

At the highest level you have 3 options:

1) Buy components that handle the future needs (At the extreme, if you do this with all of the components.... you have already purchased the bigger system...... I don't imagine that is what you want.

2) Buy extra of the various components as you need more of it's function. As an example, today you could buy a controller that handles the 600W of panels and in the future buy another charge controller for any additional panels you buy. This works fine for home systems, but can get kinda cluttered when you have 4 different versions of something but could have done with just one. On a boat, space tends to be at an extreme premium, so having multiple of the same thing can be a problem.

3) Replace components with larger versions as your needs change..... this can be expensive but it keeps the system smaller and simpler.

The reality is that you might do a mix of things. You might buy a large inverter that you will grow into but update the charge controller as you add more panels.

The most important thing is to think way ahead and have a good idea what the end system might look like. As an example, if you want to end up with a 24V system, start there..... don't start with 12V and switch later. (System voltage tends to be the hardest thing to change on a boat because of the high current devices like the windlass)

To get that vision of what the final system might look like, you need to do some energy planning. List out all the things you think you might have on the boat and what the energy needs would be. Then design a system that would meet those needs. From there you can figure out where you want to cut back and where you want to buy for the future need.

There are a lot of energy planning tools on the internet, but this is the tool I use:

 
The first big question is the boat’s use profile. For a occasional daytimes underway, the frig will be the 24hr energy hog, and it should be possible to estimate its daily amp hour usage from the spec sheet, add in computer, cabin lights, other regularly used items and you’ve got your usual 24 hr budget. Just throw in a bit more for the occasional use of everything else underway. If instead you are thinking multi-day offshore passages, all the other stuff is on 24x7 and can run up the energy budget substantially.
I’d try to size solar to more than meet your 24hr anchored budget ( running generator in quiet anchorage is a bummer). but sizing for offshore is probably impractical and everyone seems to have to run the engine or generator on passages.
 
Another consideration is there's an argument for keeping the Ah on LifePo4 cells down when used in the marine environment. I can't begin to tell you what the logic was, I was just surprised when I came across an article explaining why. Wish I had the link, but I'm afraid it didn't apply to me daily so I didn't save it.
 
The only way to size the system is to do an energy audit. You can estimate that even before you buy anything, just by checking the specs of the equipment you want. As a rough starting point, for many years the common setup for many long distance cruising boats was 4 6V T105 batteries, for a total of 450Ah of Lead Acid. Only 50% of that was usable, so that is 225Ah of available storage. This would typically run all of the boat systems, refrigeration, Autopilot, watermaker, etc. 400Ah of LiFePo4 is considerably larger than that, so should be plenty.

I would guess that you would average 200Ah per day from 600W of solar. That is a good fit for the AGM bank with only 225Ah usable. It would also be a good fit for a 400Ah LiFePo4 if your usage is less than 200Ah per day.
 
I have a 40ft (older) powerboat and have just gone to the LFP conversion. I added a Multiplus 12/3000 and went with a custom 326ah LFP pack with 250a BMS - NO Solar currently. Once all installed I did a quick test of how long the system would stay up on battery alone. The boat wasnt being lived on and was running - Engel 90l Fridge, 210 Chest freezer converted to fridge and microwave both via inverter (ambient temps in Perth at mo between 22 and 10 degrees c) 4g Router, Raspberry PI (running Venus OS), Gas detector, radio standby, USB charger (5 port high current model on idle) and 12v TV on standby.. All up the system got to 6% SOC and lasted 78 hours... before I chicken out and switched the multiplus from inverter only to charger on..

Discharge was between 2.7a and 12a

Not sure if this helps... but the above gave me confidence I could get a full 24 hours while on the boat without much care of what we are doing.. including boiling the kettle, using coffee machine and microwave... Solar will help further which will be a project taking place soon.. probably 300-400w of panels.. if I can find them to fit! I may even be able to heat the hot water with it.. then I really wont need the genset..

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My 5th wheel RV is sort of my practice sail boat. I've been modding away on it with an eye toward that cruising boat at some point.

I suggest grabbing a Victron smart shunt now and adding that next. It'll let you monitor what's happening and the bluetooth app works great. $130 and the info will guide you as you add solar/wind/etc.

The real key is of course, load management. Weather you have 2kwh or 30, the discharge rate is the key!

Any compressor fridge will do well , but one that runs on DC simplifies things as you don't need an inverter all the time.
I really like the Dometic line (waeco in australia) of 12/24v cooler fridges. I use mine as a deep freezer in my 5th wheel much of the time. It's very efficient. (The big ones are 1k, so no judgement if you buy cheaper)

Fit as much solar panel as you can reasonably. I'm of the opinion that wind generators are great backups as well for bad solar days. I think you're on the right track there.

Honestly, the only time I really run down my battery is when I run my A/C all night long.
During my testing, I had a bad solar week and it was a useful learning experience!

I'm also a fan of the victron VRM portal for getting data. If you maintain internet access on your boat you can keep an eye on it from the sky, so to speak.
 
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