Anchoring Amps/Day

JC522

Member
95
22
Based on past experience and some 3rd grade math, I calculate that I use about 140 amps/day at anchor. Does that seem about right to you? It assumes no major effort to conserve, so both reefers are running, and there is reasonable use of the stereo, TV, cabin fans, cabin lights, anchor light, etc. How does 140 amps/day compare to your calculations or experience on the hook?
 

slug zitski

Super Anarchist
7,089
1,465
worldwide
If you use a freezer your daily consumption will be very high

rechargeable electronic gizmos consume plenty of power

tv…yup plenty

150 amps is possible if you have these consumers
 

Jud - s/v Sputnik

Super Anarchist
6,507
1,870
Canada
Based on past experience and some 3rd grade math, I calculate that I use about 140 amps/day at anchor. Does that seem about right to you? It assumes no major effort to conserve, so both reefers are running, and there is reasonable use of the stereo, TV, cabin fans, cabin lights, anchor light, etc. How does 140 amps/day compare to your calculations or experience on the hook?

It compares considerably higher than my experience: no TV, one fridge (and that I requently turn off at night), anchor light only on sometimes (if no one around, frequently the sorts of places we anchor, don’t use it), stereo only intermittently.

Just randomly found this - there’s a better, downloadable Excel sheet somewhere out there: https://newcontent.westmarine.com/content/documents/pdfs/WestAdvisor/Elecbugt.pdf
 

JC522

Member
95
22
I've been looking at what it would take to justify switching to lithium batteries. So far it doesn't compute.

I measured both the RV refrigerator and the built-in refrigerator at 4.8 amps each when the compressor is running. Assuming the compressors run 50% of the time, that adds up to 115 amps/day or 80% of my electrical usage. Everything else (lights, stereo, etc) is insignificant.

At 140 amps/day I get roughly 3 days out of my 3 8D AGM batteries (405 usable amps). I usually stay at a marina and recharge every 3 or 4 days, or I can partially charge the batteries with my Honda 2200 if necessary, but that practice cuts into AGM battery life. So far, for my situation the AGM batteries are adequate and I can't justify spending ~$6000 on lithium batteries to get an additional 200 amps. I guess the argument for lithium would flip at something around 5 days at anchor. At that point, running the generator enough to keep up becomes annoying.
 
Last edited:

JC522

Member
95
22
It compares considerably higher than my experience: no TV, one fridge (and that I requently turn off at night), anchor light only on sometimes (if no one around, frequently the sorts of places we anchor, don’t use it), stereo only intermittently.

Just randomly found this - there’s a better, downloadable Excel sheet somewhere out there: https://newcontent.westmarine.com/content/documents/pdfs/WestAdvisor/Elecbugt.pdf
I made a similar spreadsheet that has the amperage draw of every electrical component on the boat, the amount of time that each of them are used at anchor or under sail, etc. It comes down to the reefers. That's where there could be a significant payback if they could be made to run more efficiently.

I guess it might help to turn them off at night, but these refrigerators can take a long time to recover just a few degrees when you turn them back on. I keep empty space filled with water jugs, and I added Merlin II speed controllers to the Danfoss compressor control boards. I haven't found anything else that can be done except adding insulation. I doubt that the payback for that justifies the effort.

At some point the lithium batteries must start to be cost justified, but I'm not there yet.
 
Last edited:

accnick

Super Anarchist
3,507
2,504
Based on past experience and some 3rd grade math, I calculate that I use about 140 amps/day at anchor. Does that seem about right to you? It assumes no major effort to conserve, so both reefers are running, and there is reasonable use of the stereo, TV, cabin fans, cabin lights, anchor light, etc. How does 140 amps/day compare to your calculations or experience on the hook?
That may be low, depending on the size/type of your refrigerators, and the general size/type of boat. It is a no-brainer to reducing lighting power consumption by about 80% by switching to LEDs for everything. Modern televisions use a surprising amount of energy, once again depending on size/type.

What do you do for hot water on the hook?

Refrigeration is the biggie, unless you have a custom refrigerator/freezer with efficient insulation. Few production boats have that. On our last boat, we had engine-driven refrigeration with AC-powered back-up. But we also had such a well-insulated reefer/freezer that the cold plates easily held for more that 24 hours in the tropics on about an hour/day of engine running, which was also used to charge batteries.

This is not the most effective use of a main engine, although ours was small enough that the hp required for the compressor and large alternator placed a reasonable load on it.

With the big engine I have on my current boat --425 hp--we have a small generator for battery charging, and a relatively smart charging system

On the hook for extended periods, you either need a watermaker or easy access to water. 12vdc watermakers draw a fair amount of power, and AC-powered watermakers are realistically going to require a generator or some other substantial source of AC. Few boats have the battery capacity to run power-hungry AC equipment off an inverter for extended periods of time.

This is where system design becomes critical. Almost every cruising boat consumes a fair amount of electricity, and one way or another, you are going to have to keep batteries up. Modern solar panel installations have come a long way, providing you have a practical location to install them.
 

2airishuman

The Loyal Opposition
1,000
464
Minneapolis area
The case for lithium batteries can be driven by various combinations of these drivers:
  • Continuous daily cycling without full recharges most days. Lead acid batteries have a short life in this environment. Lithium batteries are unaffected.
  • A requirement for shorter charging times.
  • Particular concern about weight, as with racing or catamarans.
  • Local cost of replacement AGMs. Generally, lead-acid batteries are cheaper in the USA than elsewhere, while lithium batteries cost the same worldwide.
  • And yes, a goal of fitting more energy in available space.
Keep in mind that a properly installed and maintained LiFePO4 bank will, on the average, last considerably longer than a properly installed and maintained AGM bank.
 

Jud - s/v Sputnik

Super Anarchist
6,507
1,870
Canada
The case for lithium batteries can be driven by various combinations of these drivers:
  • Continuous daily cycling without full recharges most days. Lead acid batteries have a short life in this environment. Lithium batteries are unaffected.
  • A requirement for shorter charging times.
  • Particular concern about weight, as with racing or catamarans.
  • Local cost of replacement AGMs. Generally, lead-acid batteries are cheaper in the USA than elsewhere, while lithium batteries cost the same worldwide.
  • And yes, a goal of fitting more energy in available space.
Keep in mind that a properly installed and maintained LiFePO4 bank will, on the average, last considerably longer than a properly installed and maintained AGM bank.

I have the opportunity to replace my old golf carts soon, with all these considerations in mind. I’m still caught up on the safety aspect of them - the very recent (few weeks ago) fire/explosion/sinking of a Route du Rhum competitor boat.

Granted, it was a situation in extremis - ballast tanks apparently broke, saturating the batteries, then explosion/fire. But it certainly should make one think. Apparently some races forbid them, I read (the GGR), but don’t know if that’s accurate. And, of course, race boats/race scenarios are quite different from cruising boat ones...still, makes you think of the risk.
 

Jud - s/v Sputnik

Super Anarchist
6,507
1,870
Canada
Those batteries and the associated installation are eye watering expensive

Yes, I’m well aware :). An engineer friend is keen on me getting some, since he doesn’t have to foot the bill for them :)

Best way is to be sponsored by various manufacturers...

D18D55F3-0B36-435D-BA9F-06DFB8D415E0.jpeg
 

DDW

Super Anarchist
6,698
1,228
At that point, running the generator enough to keep up becomes annoying.
For your neighbors, it is annoying from the start.

140 - 150 is about right with a fridge and freezer. 50 without. Turning them off at night won't do anything for you - the heat gain in them continues on or off, and has to be removed in the morning which will cost more or less the same in energy done now or later.

For the use you describe, the big advantage of LFP is you can recharge them partially without harm. To fully recharge AGMs takes around 6 hours - doesn't matter how big your charger is - and this must be done every week or so or you will kill them.
 

slug zitski

Super Anarchist
7,089
1,465
worldwide
In many parts of the world you can’t buy ice cubes..the local custom is to take 1 liter plastic bottles of water and deep freeze them..when you go for shopping you buy two of these frozen bottles of water and put them in your refer

substaintial stored energy in the frozen bottles …greatly reduced refer run time
 

accnick

Super Anarchist
3,507
2,504
The case for lithium batteries can be driven by various combinations of these drivers:
  • Continuous daily cycling without full recharges most days. Lead acid batteries have a short life in this environment. Lithium batteries are unaffected.
  • A requirement for shorter charging times.
  • Particular concern about weight, as with racing or catamarans.
  • Local cost of replacement AGMs. Generally, lead-acid batteries are cheaper in the USA than elsewhere, while lithium batteries cost the same worldwide.
  • And yes, a goal of fitting more energy in available space.
Keep in mind that a properly installed and maintained LiFePO4 bank will, on the average, last considerably longer than a properly installed and maintained AGM bank.
I've never had to buy batteries outside the US, so can't really comment on international cost. I had four Rolls EIG-262 conventional lead acid batteries on my last boat. They lasted six years of very heavy use over 40,000 miles, but were ready for replacement after I got back to the US.

My current boat has a house bank of two 8D conventional AGM batteries, so just under 500 Ah nominal capacity. I put those in back in 2016, and they are getting near the end of their useful life, although I could get another year out of them. Those cost about $650 each in 2016, and are $750 each today.

My plan was to replace them next spring, and depending on the final cost of the new main engine installation, I may still do that. With this boat and at this stage in boat ownership, I will stick with AGM batteries. If I were building a new boat, so that the entire electrical system was being designed and built from scratch, I would certainly consider something else.

I have a fair amount of experience around big lithium batteries on race boats. Their performance is impressive, but they are also removed from the boats and re-charged daily in specialized, purpose-built steel charging/shipping containers.
 

JC522

Member
95
22
For hot water, I run the engine or a Honda 2200 for 30 to 60 minutes. I've found that there is no good time to run a generator in a quiet anchorage, and it doesn't do much to charge the batteries in that amount of time.

All lights are LED. The TV isn't on much. The refrigerators are the biggest factor. They account for 80% of the daily amperage draw.

I do coastal cruising (The North Channel), so every 3 or 4 days I stay at a marina where I can fully charge the batteries overnight. That works for me, so far. If my cruising habits change there could be a better argument for lithium batteries, but I still have reservations about them from a safety standpoint.

On the other hand, one of my FLA batteries shorted out after 5 years. The charger saw that as a low battery and just kept pumping. All 3 house batteries boiled over. It didn't cause a fire, but it seemed like it could have. Over the last several years the same thing happened to 3 other boats on my dock. In each case the FLA batteries were 5 years old.
 
Last edited:

steele

Super Anarchist
1,756
242
Land of the locks
We are in a similar situation but with a smaller boat, one fridge, and much smaller house bank. I also looked at lithium, but the total cost including batts, new battery charger, beefed up alternator and belts, etc. did not make sense. Like you the goal was not to be energy independent for weeks, but rather be able to spend 3-4 days at anchor without using the motor. The solution was to add solar. A single 110W flexible panel is enough to run the fridge during the day in sunlight and also have some left over power to charge the batts. In overcast conditions it is much less helpfull, but will still let us squeeze another day or so out of the batts. We have limited deck space and only need solar for cruising so the panel is stored under the aft berth most of the time. Total cost including wiring, panel and charge controller was under $500 for good quality name brand stuff.
 
Last edited:

Latest posts




Top