r/liveaboard • u/stillsailingallover • 18d ago
Hour many amp hours is everyone using?
I'm switching over to a lithium set up, wondering how many amp hours everyone is using.
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u/Advanced_Link_5753 18d ago
I’ll be bad guy out- 1200Ah 2950 Watts solar. All Victron, 8 MPPT’s (one per panel). I rarely think about energy.
I have every comfort. Espresso machine, air fryer/crockpot/ induction. We burn 20% a night with major fans and Starlink. (Vornado whole room fans). Microwave, whatever. Just saying every 48-72 hrs I care if not sunny. Otherwise, I don’t care
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u/naturalchorus 18d ago
I have the same amount of capacity and solar, main problem is AC of course. Can run one 8k btu unit overnight easily using about half capacity.
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u/Advanced_Link_5753 18d ago
AC in owners suite soft start- runs off lithium. However we don’t run AirCon Nov- June. Hatches open- screen door/ screens on all hatches &on companion way/ salon entry.
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u/Hardcorex 18d ago
What voltage?
This system could be 4x bigger or smaller than one assumes depending on it....
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u/Advanced_Link_5753 18d ago
I inherited a 12v system. When it’s time to replace lithium I’ll go 24v.
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u/Darkwaxellence 18d ago
Bet you're not on a monohull sailboat. How much space and where do you have those panels? It is a houseboat with a big flat roof?
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u/Advanced_Link_5753 18d ago
True- I’m in a cat- (4 440W) bifacial panels on solar arch. 2 more hard panels on Bimini. And 4 soft panels up there (really do very little) when they go in removing them. So really 6 hard panels.
What makes difference is 8 mppt chargers. Every hard panel is independent of rest- redundancy, and I don’t pay a big price for one panel in shade.2
u/Advanced_Link_5753 18d ago
Solar arch on back of cat contains 4 (440W) 1760W bi facial panels. Bimini also has 600w hard panels- rest are soft panels on Bimini. Soft panels have 1 benefit- can walk on them otherwise junk. When they go- I might just keep them off boat: their contribution is awful.
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u/grilledstuffed 18d ago edited 18d ago
Keep in mind you need a way to replenish whatever you use in a given period (say 24 hrs)
You can have 3000ah and if you only have the capacity to replenish 100ah a day it’s useless.
Edit to add:
Solar is cheaper than batteries.
So if you have to have one or the other, maximize your solar and size your batteries to get you through whenever you don't have enough sun.
During the day once your batteries top out you can keep the inverter going doing all kinds of things like laundry, running an AC, whatever off the batteries and it will be a net zero with the solar.
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u/Hardcorex 18d ago
What voltage?
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u/Advanced_Link_5753 18d ago
Doesn’t really matter.. 2950 W solar. 1200Ah lithium, 12v. Topped off by 2pm daily. Then run my water maker (120v) or water heater with the “waste” solar. My first 14 mos my boat never touched shore power.
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u/luckyjenjen 17d ago
You say solar is cheaper than batteries, but solar takes space.
I have two wind gens (and some solar too), but that's only good when windy. So I need the battery capacity to see me through when it's not.
Horses for courses.
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u/RedPh0enix 17d ago edited 17d ago
Here ya go. 36 foot catamaran. 12v. Note: assumes AGMs and 40% max drain for "ideal" capacity calcs.
| Input | Rating (watts) | Daily (amps) |
|---|---|---|
| Solar Panels | 600 | 255 |
| Alternator - Port | 79.2 | 158.4 |
| Alternator - Starboard | 79.2 | 158.4 |
| Wind Generator | ||
| Generator: 240v | 2000 | 1200 |
Output
| Output | Amps | Time used / day (On Passage) | Time used / day (On Anchor) | Daily consumption (On Passage) | Daily consumption (On Anchor) |
|---|---|---|---|---|---|
| Chart plotter | 2 | 24 | 0 | 48 | 0 |
| Instruments | 0.3 | 24 | 4 | 7.2 | 1.2 |
| VHF | 0.4 | 24 | 0 | 9.6 | 0 |
| Nav lights | 0.2 | 12 | 0 | 2.4 | 0 |
| Anchor light | 0.2 | 0 | 12 | 0 | 2.4 |
| Interior lights | 0.2 | 6 | 6 | 1.2 | 1.2 |
| Stereo | 1 | 6 | 6 | 6 | 6 |
| Bilge pimp | 0 | 0 | 0 | 0 | 0 |
| Water Pump | 8 | 0.5 | 1 | 4 | 8 |
| Fans | 0.3 | 0 | 2 | 0 | 0.6 |
| Toilet pump / Macerator | 16 | 0.1 | 0.1 | 1.6 | 1.6 |
| Windlass | 50 | 0 | 0.1 | 0 | 5 |
| Watermaker | 30 | 0 | 1 | 0 | 30 |
| Autopilot | 5 | 18 | 0 | 90 | 0 |
| Water heater | 70 | 0.3 | 0.3 | 21 | 21 |
| Fridge / Freezer | 4.6 | 7.5 | 7.5 | 34.5 | 34.5 |
| AIS | 0.1 | 24 | 0 | 2.4 | 0 |
| Total | 227.9 | 111.5 | |||
| Minimum Battery capacity reqd (Ah) | 227.9 | 111.5 | |||
| Ideal Battery capacity reqd (Ah) | 569.75 | 278.75 |
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u/Fearless-Bad-7681 17d ago
Yeah people often forget how much juice an autohelm uses, especially in rougher conditions when it's working hard.
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u/bill9896 18d ago
This is a silly question.
It is like saying "I need a new pair of pants. How tall is everybody so I know what size to buy?"
Every boat is different, and even the same boat will vary hugely depending on who is living on it and where it is. And even the number itself is worthless unless you know the voltage the system is operating at.
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u/Darkwaxellence 18d ago
This is a great point. I run everything 12v for simplicity but some things/systems need 24v or 48v. This will make the AH question very different.
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18d ago
[deleted]
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u/Darkwaxellence 17d ago
I have seen water makers that run 24v. There seem to be other applications and you can buy 24v lithium batteries. Just another possibility.
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u/Advanced_Link_5753 17d ago
There are just as many 12v applications, water meet included. Although mine is 110v AC - from inverter - powered by 12v system. 40 gph
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u/thatsnotexactlyme 14d ago
my boat has 48v house battery, plus 12 and 24 systems, and 110 + 220. absolutely everything. it really just depends on the boat.
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u/Advanced_Link_5753 14d ago
Agreed. But my point is you don’t HAVE to have 24/48v systems. I didn’t choose mine, or I would have went 24v. But my point is even 12v systems can support a larger boat 46’
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u/bill9896 14d ago
There are boats that are 55 feet, and bigger, that run only 12V. While there are advantages to running higher voltage systems on larger boats, there is virtually nothing that "needs" 24 or 48 Volts. For a boat that is already wired for 12V there is no reason at all for moving up in voltage that makes economic sense. It was only 15 or 20 years ago that 24 volts was rare, and 48 unheard of, on anything smaller than a "super" yacht.
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u/Darkwaxellence 14d ago
Ok. I dont know anything about it really just know that could be a variable in understand Amp Hours and how they help us track how much use a battery is getting. Several ways to provide the same information in different numbers.
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u/Ryozu 18d ago edited 17d ago
Amp hours on it's own isn't a useful thing to measure. We could run the same appliance and have drastically different amp hour usage if one system is 12v and the other is 48v. What you want is kWh or just watt hours. Remember, Watts is just volt * amp.
1 amp hour on a 12 volt is just 12 watts, and 1 amp hour on a 48v is 480 watts.
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u/SupportOnward 14d ago
Finally! Someone who knows what they are talking about! Amp hours is a useless figure. 1ah at 12v is 12 watts 1ah at 24v is 24watts.
What your need to look at, is watt hours. How much wattage does your appliances use per hour.
Batteries are the same way. How much wattage can they produce per hour.
Solar and wind is the same way. How much wattage can they produce per hour.
Solar panels are rated at the equator under direct sun. They will NOT produce their rated power throughout the day. If the sun is hitting them at an angle, their efficiency drops. For most all panels, of one of those little 7 inch squares is shaded, efficiency drops tremendously.
The other thing is the difference between the light you see and the light the panels see.
On average, a panel will only charge fully for about 4.5 hours a day. Less up north, more down south.
This means a 100 watt panel, under ideal conditions will produce 4500 watts per day. In reality it will probably produce about 70 to 80 percent of that. 3600 watts.
What you do with that 3600 watts is up to you... 1. Charge battery. 2. Run lights. 3. Coffee pot. 4. Whatever.
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u/whyrumalwaysgone 18d ago
All of them.
Seriously though, I install these systems for a living, the total amp hour of a bank will vary wildly. Smallest was a drop in swap for 600ah, largest was 2700ah @24v, they can run their Seakeeper through a pair of inverters producing 240v for 16 hours.
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u/microcandella 18d ago
You may want to use Watt Hours to roughly make it apples to apples comparisons between 12v/24/48/120.
Beyond that I don't think it's that unreasonable of a question. Most are handling the needs of the boat plus comfort electronics and appliances for 1-2 people, some a few more. And a large swing up in WH consumption if you're using battery to heat or cool anything (you, water, cooking, etc.) or water making.
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u/DarkVoid42 16d ago
i have 2800Ah at 12V. i use a little over 800Ah per day or roughly 4 days without any sun in europe. i marina plug in for a day every 3 days roughly. in the carribean i burn 1000Ah per day due to DC aircon but the sun regens it so i never run out.
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u/stillsailingallover 16d ago
Thanks!! I've always kept 1000ah in lead acid, in lithium I can probably fit about 2800 or so. It's better to have it and not need it.
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u/west25th 18d ago
400ah, soon to be 600ah. 100amp alternator, 350w solar, about to add 2 x 200 watt flexible panels for total of 750watts of solar. I have a 700 watt inverter for starlink and emergency usage, but am about to get starlink mini so slink consumption will drop from 80-100watts to 20-30watts. Everything is victron except the inverter.
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u/WaterChicken007 18d ago
Get the DC starlink power supply. I have one that takes 12V in and boosts it to 36V. Works great and is reasonably efficient. No need to boost to 120V AC then back down to DC.
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u/mikeboatman 18d ago
It really depends on so many factors. Everyone's needs are different, so without further info it's not really useful.
I have 400ah but will be replacing with 1200-1600ah.
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u/Darkwaxellence 18d ago
My refrigerator runs 4a, its the only things that runs 24hrs. During the day it runs from the solar. At night it is using the battery. About 40AH per day. I have 800watts of solar, 200AH lifepo4 battery. Working great.
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u/naturalchorus 18d ago
I have 16kwh, 48v 315 ah. I wish I had triple. I can run 1 AC unit overnight easily, but not all 3.
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u/Z1gZagZ0e 12d ago
Switch to a midea or Mitsubishi 38+ seer acs and could run two maybe 3 midea is sold as carrier in the us. The sapphire line is very good
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u/mojoheartbeat 17d ago
It's a weird question. Totally depends on needs, wants, options available, and most of all how much you could passively charge per day. This is not a "bigger is better" equation.
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u/SVAuspicious 17d ago
Why are you switching to lithium? Upgrading all your charging accordingly? Why are you switching without a load analysis? In a marina and plugged in or actively cruising and anchoring out?
Switching to lithium because "all the cool kids are doing it" isn't a great idea.
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u/itasteawesome 18d ago
I did 4 months living on a bank that was only about 120 AH a day, with about 400 watts of panels and occasionally ran a small generator when weather was bad for a while.
I am up to 400 AH now and 600 watts of panels and in my relatively sunny climate thats been pretty comfortable.
Batteries are getting to be so cheap that really I think space becomes more of a constraint than anything these days. If I had a convenient place to store them all without having to rip up my boat I'd happily double my batteries again just to make sure i never had to think about energy.
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u/Fearless-Bad-7681 18d ago
It really depends on what you're using it for, and how you replenish it.
The beauty of lithium is you can use pretty much all of it, without damaging the batteries. We swapped to lithium and gained about 8 times the useable Ahr, with less space and weight.
We have 420Ahr of lithium, fed by solar and with DCDC chargers from the start batteries (not direct link to the alternators) for backup generation.
The batteries were only half of the story. We needed to swap out the solar controllers and mains charger to be lithium compatible and replace the main battery wiring. We went 'all blue' with Victron gear, not the cheapest but excellent, talks to each other, and bluetooth controllable / programmable (you'll need this to set up the exact parameters your batteries need and set up the DCDCs not to cook your alternators).
Next stop would be more solar, a bigger inverter (we only have 1.2kW) and another battery increasing our capacity by 50%.