How awesome can a 750Ah Lithium + 1-2kW solar boat be?

[Canuck Sailor]

Erik:
What kind of Solar Charge Controller are you using with your 500 Watts of solar panels? It seems that there is something missing in your usage figures. 500 watts in your area should be giving you 20 - 35 amps of power/hour over a five hour or more day of sunlight. You shouldn't have to run your generator that much.

We have 450 watts of solar with an MPPT SCC that provides 15 - 30 amps on good days. That's a lot of battery charging. We use with TV watching anywhere from 60 - 130 AH overnight. The solar charge makes that up usually before three o'clock on the high end. We can run our water maker during the day on the low end and still make up all the power.

Your AGM will provide you with 25% of useful capacity and we had that with 890 AH of AGMs. Our voltage overnight was never less that 12.6V in the morning with fridge/freezer (3.9Amps per hour), fans and electric toilet. At that time we had 400 Watts of solar power and the same SCC.

The last three years we have used our 500 AH 12.8V LiFePo4 battery in 5S configuration. They have been great and waking up with 13.2v on the meter is always reassuring, knowing that it is equivalent to 12.6V with AGMs. (13.0v is cause for concern and we look for additional charging).

It cost me more from my AGMs to be shipped to where we were than the LiFePo4 package. AGMs were sea freight and LiFePo were air freighted in.

[Zai]

We have 600 amp hour battery bank (Lifeline AGMs) with 600 watts of solar. (thanks to information/suggestions from this forum).
We run the watermaker (not every day maybe every two to three days depending if we run the washing machine or wash the deck with fresh water) and make hot water from the inverter.
We have just one cooler, which uses about 4.5 amps when running. We use phone/computer/internet router chargers round the clock. So far we have not needed to run the engine or use shore power.
I contribute this to the factor that our solar is sized correctly in connection with the size of the battery bank. (I think this is very important).

[Moontide]

First, the fact that your batteries jump back to 12.6 after you turn off the loads is the key. The voltage under load, or being charged, really does not give you any indication of the charge level. For real accuracy the batteries have to be "rested" which may mean hours of no charge or use. Obvioulsly not very practical. It does sound to me likeyou are running the generator than necessary.

The fast acceptance rate for the AGM and Li batteries is a very nice feature over FLA's, but certainly comes at a price. If you increase your solar panels to cover the loads during the day then you really only need battery capacity to hold you for the 12-14 hours when the panels are not producing much energy.

Running your heavy loads when the sun is strong helps a bunch since you may be using "excess" solar power that otherwise would be wasted.

I have 720 watts of solar. Regularly get over 240 ah a day from them, and sometime over 300 ah (we run a lot of stuff). I put a limit on the controller of 60 amps and see that occasionally in the summer. Usually put out something over 40 amps for several hours every day Of course the more charged the batteries the less amps are being sent to the batteries (This is where the AGM or Li are nice.)

From the way you describe your usage I am guessing that with more solar you would be fine and not need to run the generator. If you still need the generator I would definetly get a larger charger and run the generator early in the morning before the solar really kicks in. Running the generator when the batteries are at there lowest charge is more efficient than when they are fuller.

There's my 2 cents.
Bill

[barnakiel]

FREAKING awesome.

You lucky duck.

Cheers,
b.

[JimsCAL]

Two comments:
1. Look at improving the efficiency of the refrigerators. They're your biggest loads.
2. Consider adding a wind generator. Would give you charging at night and on cloudy days.

[travellerw]

Originally Posted by arthur.watson.1

If your reefers are pulling a constant 10+ amps, I can't help wondering if you should check how well the boxes are insulated. Two additional inches of foam all around could make a big difference -- and even possibly offer a far more economical solution for you!

Art Watson

I'm not sure I agree. I suspect his 450 has "off the shelf" fridges that are working fine. Sure if you have space you might be able to add some insulation around the fridge, but it won't improve it much. The "dorm" fridges that are being sold as marine are just crappy!

Our boat has 1 "off the shelf" fridge and a factory installed freezer. We draw 6-9 amps (depending if 1 in cycled in or both).

[tomfl]

Originally Posted by exitstrategy

SNIP

Additional solar, going from 500W to something huge like 2kW would in theory give me 160A from solar, enough to fill 600-700Ah of Lithium house in 3 hours or so. So we could use inverters during the day for washer/ice/water right?

Cheers,
-Erik

My situation is different, I have 2 215 watt panels and 440 amps of flooded house batteries. I run a Frigaboat in the galley with a small freezer compartment and an Engle in the cockpit for drinks and daily needs. I am able to restrict opening the Frigaboat to once a day or less and open the Engle a few times a day. My total 24 hour energy consumption is between 45-50 amps a day. Normally I am dumping power by 10:30 AM and when I start dumping power I charge computers, camera batteries, cook with 120 stuff, and in general use excess power instead of dumping it.

Living in the Keys/Bahamas there is normally plenty of sun for the solar array. One thing you need to keep in mind is where your boat is affects how much power your solar array generates.

[Three Sisters]

Originally Posted by smac999

how big is your battery charger? with 1000ah and a 5k gen you should have 200a of charging.

if you have a little dinky 40a charger you are just wasting gas and time and barely charging in 2-4 hours of gen running. and you are never getting charged batteries each day.

I would question the 10-13a with everything on. that is pretty low.

In post #10 the OP replied that there is a 40a alternator.

The battery charger ? Who knows.

[TheThunderbird]

I dont put 10k $ in any new technologies. Lithium prices should drop soon,too.

I would start with Additional mini lithium system, a bigger charger of 80/100A, more insulation, and easier life style with less ice

[valhalla360]

Originally Posted by exitstrategy

But it does seem like the 40A alternator is way too small for a 1050Ah house bank. But if I switched over to Lithium, then the generator would become effectively bigger with the linear charge curve.


Cheers,
-Erik

I think this is your biggest issue and it would far simpler and cheaper to get a bigger charger.

Bulk charging is usually around 25% (in amps) of the amp-hr rating, so you could bump up to 250amps (even 100-150amp continuous duty alternator would drastically cut your engine run time).

I don't think the Lithium with the 40amp charge source will gain you much. That's only 4% of the amp-hr rating, so even as you leave the bulk charge range on the current batteries, your system is still able to absorb a good percentage of the amps the little 40amp charge source is putting out.

Even better, if you get a big alternator and do bulk charging in an hour in the morning, the solar putting out 20amps, can to the top up work during the day.

One other question regarding the engine charging: Is this just a standard 40amp alternator which is designed to put out the peak rating for a few minutes before scaling back after recharging a starting battery or a continuous duty alternator that can put out 40amps for hours.

It really sounds to me like you have a solution looking for a problem and you are ignoring the more logical solutions. (given that you said you have a relatively new set of batteries, it makes little sense to replace them)

[smac999]

He runs his gen for 4 hours a day and it doesn't charge his batteries

Why does everyone keep mentioning alternators. His issue is likely battery charger size. Which he still hasn't answered my question. If he rarely runs his engine a bigger alt won't help much. But we know he does run his gen daily

[valhalla360]

Originally Posted by smac999

He runs his gen for 4 hours a day and it doesn't charge his batteries

Why does everyone keep mentioning alternators. His issue is likely battery charger size. Which he still hasn't answered my question. If he rarely runs his engine a bigger alt won't help much. But we know he does run his gen daily

Snip: "But it does seem like the 40A alternator is way too small for a 1050Ah house bank. But if I switched over to Lithium, then the generator would become effectively bigger with the linear charge curve."

This is from the OP's second post.

It's a bit unclear exactly what his charging system but given the 2-4hrs it takes him to charge, it makes sense that he is calling a 40amp alternator a generator or vice versa. Logically, he isn't using a generator connected to a 200amp battery charger or it shouldn't be taking 4-5hrs to charge the bank unless he is pushing for that last 5% when the solar should fill that roll if he bulk charges in the morning with the generator/alternator.

If his usage is really around 150amp-hr per day, the 500w of solar panels should be producing around 100amp-hr and the generator should only need to provide around 50amp-hr. In bulk charge mode first thing in the morning at 40amps the batteries should soak up most of that 40amps, it should take around 1.25hrs and then the solar panels should fill in the rest. 2hrs generator time should be for a day when there is no sun and the solar panels don't keep up.

I think the first thing the OP needs to do is an energy audit to figure out what he is really using. I suspect he has an oversized battery bank and an undersized charging system and may be consuming more power than he thinks. I also suspect he is reading the charging voltage, so it looks like the batteries are full and within an hour or so of removing the charge voltage in the evening the bank slips back to the voltage that corresponds to the actual state of charge (ie: he's never getting the bank up to 100%) or it's possible the bank, although relatively new, is damaged.

[exitstrategy]

Thank you all very much for the continued comments and questions and links.

A little more context:
We bought the boat new 4 years ago in France, cruised for 3 months, then placed her in charter in the BVIs. We did sail one month a year over the last four years, but starting 2 months ago, we are now full-time cruisers. So, I am behind on knowing my boat and now coming up to speed. I apologize for my poor understanding making the thread more difficult than it should.

We have a FlexMax 60 MPPT configured for 24vdc input.

The real stinker is the battery charger is not the 40A I thought, but a CRISTEC CPS3 12V-25 Amp charger. <<< This is the weakest link in the system for sure?

We only run the icemaker, water maker and washing machine off of AC when the genset is running with virtually zero use of inverters. Although I would like to use inverters for laptops at will.

The fridges are the factory fridges that come from Lagoon that side open and lose all of their cool air whenever someone opens the fridge (too often) and of course build a ridiculous amount of frost from the humid tropical air. I would love to add insulation around them, but as they are factory fit to the cabinetry this would be so much work, I think I would rather rip them and the cabinetry out and replace them with a top loading fridge, and a separate top loading freezer.

Yesterday at peak sun, the mains reached 13.1, and this morning to my happy surprise we made it to the morning with still 12.4 and now climbing again with solar. (Last afternoon/evening we were all off the boat on a beach BBQ, so I am thinking w/o people opening the fridges we saved some power?)

1) The first order of business should to to replace the 25A battery charger with a 200A charger? (Looking at Mastervolt and Xantrex and Cristec online all I see are chargers <= 100Ah, anyone have a suggestion?

2) Next an arch to extend the rear of the boat above the davits to hold 6 more 250W panels?

3) Finally install the Lithium? 600-900 Ah?

Cheers,
-Erik

[smac999]

you won't find a 200a 12v charger. you just need more then one. I would start with one, and see what happens. at 25a you are definatlly not charging the batteries. the boat probably uses near that so you are just breaking even while running the gen and not charging.

if you don't already have a good inverter now is the time to buy a good inverter / charger. IE magnum ms2812. has a 125a charger. if you don't need (more) or want inverter power then the mastervolt 12-100-3 is a good charger.

a 100a charger will draw about 16-17a of AC. with a 5k gen you can run 2 for fast charging but it'll require a bit of manual control if you are trying to run other big loads as well. this is where the inverter / chargers are good becaus they will load share and cut down the charger when other things turn on.

a combo of the inverter / charger and mastervolt will give you ~200a, and load that 5k gen up, and be good charging for a 1000ah bank.

[exitstrategy]

Smac99, thank you very much for the direction. Really appreciate it. Looking into logistics now...