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

[exitstrategy]

High-level request for advice and opinions on changing over from AGM to Lithium.

I have been reading the massive Lithium thread, but at nearly 300 pages after hours and hours I still feel like I would like the help of a crisper summary of Lithium applied in the cruising environment.

Here is my simple summary understanding:

• Lithium is much more expensive upfront, but might be competitive if you factor in lifecycle.
• Lithium can use 80% of the Ah in the batteries vs 50% for lead
• Lithium charges linearly instead of asymptotically
• Lithium is much lighter
• Lithium can be packaged in drop-in battery formats (e.g. SmartBattery and StarkPower)

Here is the power system I have now:

• House bank: (5) Lifeline AGM 210Ah batteries= 1050 Ah nominal (1-year old, but boat just came out of charter)
• (2) 250W Kyocera Solar Panels
• 5kW Onan Genset

[B]Usage:

• A Lagoon 450 with 5 people living full-time as a family cruising (tropics)
• 2 small fridge/freezers that are drawing about 10 amps 24/7
• Fans, lights and water pump that are no big deal
• Every morning we are down to 12.0-12.3 v from just the fridges and lights (no DC powered inverters in use)
• Every morning we run the generator for 2-4 hours depending on how much water/laundry/ice we need making, and charge the laptops/phones/toys during this time
• During the day, the solar will often keep the house up past 12.7v and sometimes even go over 13v.
• But by late afternoon we are often back to 12.2v, again no inverters, no water making under DC, music rarely played. Lights, fans and the 2 small side-opening fridges
• So we run the generator again, do more water/ice/laundry if we need it.

It seems to me that we are running the generator too much no?

With the nominal 1050 Ah house bank, we should have 500 Ah right? And all-in the lights/fans/water-pump and fridges show 11-13 amps on the battery monitor. Call it 13A x 12 hours = only 150 Ah of usage, but why does the house get down to 12.0-12.2 by the morning with that size bank? Yes, when I turn off the fridges it will jump back to 12.6. So does that mean that I have misunderstood how to manage my batteries? Do I charge when it is at 12.2v under the load at the given moment, or do I have to keep turning off all the loads and then check what is the voltage on the house and if is > 12.2 w/o load it is still good? <<< This is a key question.

Going forward with the assumption that I am only getting about 150Ah out of these batteries, I am thinking of Lithium.

Is it as simple as StarkPower suggests? I buy 7 of the 125Ah (750Ah) deep cycle batteries that weigh just 240# vs #670 for the current set of AGMs. They cost $1440 each or $10k. I pull the AGMs out, pop the Starks in and save 430# of weight. And now I only have to run the generator about 1/4-1/3rd as much?

Now, the 750 Ah bank would get fully charged with the 5kW genset in what roughly 1.5 hours? And it would much more efficiently suck up the solar during the day right? And presumably stay fully charged so we would no longer need the evening genset cycle. Unless we wanted to run the AC appliances = water/ice/laundry.

Then, jumping the shark, if I were to add an arch on the back of the 450, and extend towards the aft a row of additional solar panels, I think I could comfortably carry 6 more, to have a nominal 2kW system. That seems like it would be enough to start indulging in some inverter use, and keep several 85W macs plugged in, and perhaps judiciously use the water or laundry or ice maker? And perhaps getaway with not needing to run the genset at all on normal sunny days?????

Please if you have the patience to give me links to [better] existing threads or sources. But at the highest-level, aside from the money involved, can I run the boat off of just solar with a Lithium house bank? <<< This is what I really want to know - how awesome can I make the boat from a power point of view (setting aside upfront costs). How realistic of expectations can I indulge in?

Many thanks in advance for any and all help,
-Erik

[arsenelupiga]

i will run off solars only and engine chargers in emergency.

Have 2 x 180 W , and plan to add watermaker. Playing with idea of using petrol watermaker 140 l / h to avoid stressing batteries.

I may upgrade solar to 2x 250w, but so far see no need for that.

may change my thinking but at present cant imagine why one needs sooo much power.

[kmacdonald]

I don't think lithium is a lot more expensive up front but depends somewhat on what needs to be upgraded as far as your charging systems.
To my knowledge, there are no reliable "drop in" lithium replacement batteries.
Make sure all your lighting is LED and a 400 Ah lithium bank should work for you. You will need a 150 to 200 Amp alternator or charger and the appropriate regulator for the alternator and solar array.

[kmacdonald]

Here is a link to the bible on lithium batteries: LiFePO4 Batteries - Thoughts & Musings Photo Gallery by Compass Marine How To at pbase.com

[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.

[alctel]

That power consumption seems high as well - 11-13 amps for just fridge/fans/lights?

Have you thought about switching all your lights to LED? With 500watts of solar and that big a battery bank I'm surprised at having to run the genny for 4 hours every day

[mbartosch]

Some real-world numbers from our boat. Maybe this helps judging if going LiFePO4 is suitable for you.

400 Ah LiFePO4 (4P4S)

Charging sources:
425 Wp Solar Panels
150 A Balmar 6 type alternator, throttled to about 90 - 100 A via Balmar MC614 Belt Manager.

Most significant loads:
1 fridge unit. In use permanently/never switched off; in addition we daily swap four large eutectic plates to cool down the ice box, essentially that provides a second cooled storage but puts additional cooling load on the primary fridge : about 80 - 90 Ah per day
1600 W Inverter, liberally used whenever needed
LED interior lighting
LED navigation lights
Autopilot
Navigation electronics (2 B&G MFDs, 4G Radar, VHF, AIS)

Load scenario 1: moored/anchored
Liberal use of interior lighting
Liberal use of inverter mainly for the following purposes:
- electric kettle, used daily for making coffee (draws about 4 Ah per 0.5 l boiling water)
- single induction cooking plate
- chargers for devices which don't charge from 12 V

Daily consumption moored is about 120 Ah
Solar input often over-compensates daily use, typically we gain about 20 Ah daily when moored in good weather. Under normal conditions we get away about even.

Too lazy to use shore power for this reason even when docked.


Load scenario 2: cruising/sailing, no engine
All of the above, minus induction plate (not swiveling, too dangerous), plus
- navigation lights
- auto pilot
- navigation instruments
- radar

Daily consumption cruising is about 240 Ah.
Daily shortage: about 100 Ah.

Remediation: run engine for about one hour daily on average. Aligned with sailing conditions, we run the engine when the winds are not good.
On some days this may mean not at all, accepting 100 Ah "withdrawal" on the battery bank.
On other days, motoring is required for a longer time, compensating for several days of cruising.
Out of habit will not sail into the night with less than 40 % SoC, run engine if this happens.

[iliohale]

Check out the Sailing Wilding blog here: https://sailwildling.com/2014/11/08/...er-of-lithium/

Doug has been running on Lithium for some time now and can likely give you some good advice. My understanding on Lithium is that the devil is in the details in terms of your charge controller and battery monitoring.

[sailingfarmer]

With the advent of lithium batteries and more efficient solar panels.... life is going to change on a cruising boat..... especially if they find a cheap mining source for more lithium. Lead batteries will eventually go out like the horse and buggy.

Marrying electrical systems together is a real task. I see even experienced companies screw up regularly. Sounds like you have it handled pretty well... would love to hear about the aftermath.

[exitstrategy]

Thank you everyone for the replies and links. Really appreciate the real-world data.

We have 100% LED lighting.

When we are at anchor in the day, we are using that 10-13A and it is virtually dominated by the 2 fridges. Besides the fridges there is the water pump, 12V fans (2-3) and lights.

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.

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

[Emerald Sea]

Considering your energy needs and nr of people living onboard your on track. I personally don't think 400Ahr of lithium is sufficient as if you choose this amount you wont have any, or much, redundancy. We have 720Ahr LiFePO4 on our 450 with similar energy demands but only two people living onboard and we find this is fine ie we can go three days without charge should this happen. Regarding your solar, 1.5 to 2k of modules should be your minimum. While on sunny days and all conditions right,you'll fill your bank before noon but on the cloudy days when your efficiency drops you'll still get some 40-60A in. You will also need to replace your factory installed bat charger as its likely not compatible for the lithium charges and its too light. We have a Mastervolt 100A and works as it should. This was Mastervolts recommendation noting our lithium system is also Mastervolt.

[exitstrategy]

Awesome, thank you, love direct - real quotes.

Originally Posted by Emerald Sea

Considering your energy needs and nr of people living onboard your on track. I personally don't think 400Ahr of lithium is sufficient as if you choose this amount you wont have any, or much, redundancy. We have 720Ahr LiFePO4 on our 450 with similar energy demands but only two people living onboard and we find this is fine ie we can go three days without charge should this happen. Regarding your solar, 1.5 to 2k of modules should be your minimum. While on sunny days and all conditions right,you'll fill your bank before noon but on the cloudy days when your efficiency drops you'll still get some 40-60A in.

[sailingfarmer]

Erik ....when you are done could you redo my electrical system too? lol

[reed1v]

My 2 cents: While lead/acid batteries are outdated, they do withstand a lot of abuse. Would check on how well those lith. batts withstand massive drawdowns, way overcharging, and wide temperature ranges. Quality lead battery companies like Rolls had charts showing the range of abuse before their batteries were compromised. Hopefully your Lith company does the same.

[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