Autonomy with two 100w panels 54 amp-hour battery

[francois.lavoie]

Last year I wanted to be completely autonomous in terms of energy consumption on my Catalina 250 sailboat.
https://www.cruisersforum.com/forums...ls-215877.html
It was concluded that I could meet my energy needs with one 100w panel thru a mmpt controller plugged to a unique 54 amp-hour battery. Also, I was better to go for a cooler and ice solution than to go for a compressor driven cooler and even worse with a peltier driven cooler. The latter system being even less energy efficient device:
For the next summer my conditions will change. I will always be at a marina, but might go for some lenghty sailing trips on the St-Laurence river east of Quebec city. This means that I might drop the anchor in a bay for a day or two.

My situation.
Two 100W solar panels with a mmpt controller (which could accomodate 4 panels)
54 amp-hour battery (1)
No generator, but the electricity provided at the marina most days.

I intend to buy an aspenora compressor driven 37 quarts cooler which depending on the ambient temperature could spend 1.4 amp-hour.

I am wondering how I could augment my autonomy. Would there be a better alternative to the Aspenora?

Comments are appreciated.
Thanks

[tkeithlu]

Hmmm. You don't say much about your energy needs. Some of us are not ready to sacrifice hot showers, some are. Generally, your ways of adding to your energy budget, if you are scraping along at the minimum are more solar panels and adding wind, both of which work at anchor. At the fringe of similar efforts is towing an impeller that turns a generator, either as an independent system or as regeneration on an electric propulsion motor. Using that at anchor would be dependent on having a strong current. Both wind and water generation interfere with sailing performance. Only solar is "free."

The other side is reducing use. Make sure that every single light on the boat is LED.

Finally, if "independence" really only means maintaining the comforts of life for a few days away from the marina, add batteries and soak up more reserve energy while at the dock.

[Mirage35]

From this and the previous thread it appears that the cooler is by far the biggest load. If the one you are proposing draws 1.4 amps (I think that's what you mean) then, even if it runs continuously, it will use maximum 34 Ah per day.

Your 200 W solar is probably perfectly adequate but this feels like it might be pushing the limit of your battery capacity. In terms of autonomy for your circumstances - picture anchoring overnight, followed by a cloudy day, and another overnight anchor. By that time your battery would probably be dead.

As an example: on a modestly equipped 35 footer, I estimate we use 70 Ah per day (60% of that is the fridge). With a single 100 W panel I'm fine spending two or three nights at anchor, unless it's really cloudy. But I have a 210 Ah house bank to draw on, and a separate starting battery if I need it.

[francois.lavoie]

I was thinking of adding a second battery. I wonder what total capacity in terms of Ah I should aim? How is your fridge doing in term of electricity consumption?

[Mirage35]

My fridge draws 3.5 amps when operating and I estimate a 50% duty cycle. (It's probably more than that on a hot day.)

So: 3.5A times 12 h/day = 42Ah consumption over a typical day.

Do the calculation for your proposed setup and estimate how long it would take to use half of your battery's capacity - that will give you a sense of how long you can go without any charging source without killing the battery.

Without doing any calculations my gut feel is that increasing battery capacity would be the best thing to do in your circumstances.

[thomm225]

I have two 90 AH batteries in parallel with usually 115 watts of solar from two different panels charging them thru two separate controllers.

I also have two 20 watt panels that I either hook up directly to the batteries when sailing or thru one of the controllers.

They power my computers, inverter, autopilot, depth, VHF, HDTV/monitor, lights, etc.

When these batteries fail I'll probably go with 6v golf cart batteries or high AH 12 Volt batteries. Some golf cart batteries rate 255 AH.

https://www.batteriesplus.com/produc...SABEgIXIvD_BwE

[SV__Grace]

One 54 amp hour house battery is pretty tiny, even for a small boat, unless you have minimal electrical needs (such as an icebox instead of running a fridge compressor and little to no inverter use).

Are you aware that you have to plan for using no more than 50% of battery capacity (unless lithium) before needing to recharge? You will kill your battery quick by regularly discharging more than that.

You also need to plan for cloudy days. With little to no excess capacity you will have to watch your SOC carefully and supplement your solar more often than with a larger house battery bank.

[Scubaseas]

Originally Posted by francois.lavoie

Last year I wanted to be completely autonomous in terms of energy consumption on my Catalina 250 sailboat.
https://www.cruisersforum.com/forums...ls-215877.html
It was concluded that I could meet my energy needs with one 100w panel thru a mmpt controller plugged to a unique 54 amp-hour battery. Also, I was better to go for a cooler and ice solution than to go for a compressor driven cooler and even worse with a peltier driven cooler. The latter system being even less energy efficient device:
For the next summer my conditions will change. I will always be at a marina, but might go for some lenghty sailing trips on the St-Laurence river east of Quebec city. This means that I might drop the anchor in a bay for a day or two.

My situation.
Two 100W solar panels with a mmpt controller (which could accomodate 4 panels)
54 amp-hour battery (1)
No generator, but the electricity provided at the marina most days.

I intend to buy an aspenora compressor driven 37 quarts cooler which depending on the ambient temperature could spend 1.4 amp-hour.

I am wondering how I could augment my autonomy. Would there be a better alternative to the Aspenora?

Comments are appreciated.
Thanks

1.4A usage may be optimistic as the unit is rated at 35W or 2.9A. But if it's sunny out 200W solar should run it fine. Really depends on how much you open it and what the ambient temperature is. A power pack/jumper box (12Ah to 18AH) might be an idea to supplement what you have and run the cooler off the USB cable. Then use it on your car in the winter.

[guyrj33]

Block ice will last several days in a good cooler.
If you simply must have mechanical refrigeration, add a second battery bank composed of 2 6v GC batteries as an earlier poster suggested.

[Martkimwat]

Originally Posted by SV__Grace

One 54 amp hour house battery is pretty tiny, even for a small boat, unless you have minimal electrical needs (such as an icebox instead of running a fridge compressor and little to no inverter use).

Are you aware that you have to plan for using no more than 50% of battery capacity (unless lithium) before needing to recharge? You will kill your battery quick by regularly discharging more than that.

You also need to plan for cloudy days. With little to no excess capacity you will have to watch your SOC carefully and supplement your solar more often than with a larger house battery bank.

I agree and would add that you also need to bear in mind that to get the last 10% or so of charge into your batteries is often not possible so in fact your batteries may only be 90% charged, meaning that you only have 40% available before reaching 50% SOC, so in his case only 22 amps available. Also most batteries Amp hr rating is based on a 20 hr discharge cycle , so in the case of his 54 Amp Hr battery, that's an assumed discharge rate of 2.7Amps. If he draws a higher rate than that, he will see less than a 54 Amp.Hr capacity. I suspect his coolbox that he mentioned has an average of 1.4Amps/Hr but may be as much as 4.5 Amps draw with a 20~30% duty cycle which is not unusual for a refrigerated coolbox. That sort of current draw, on top of other possible usage at the same time, will mean he will not see 54 Ampacity. In my own case, I have around 170watts of solar from five panels feeding through three individual MPPT controllers. I have a house bank of 220Amps of SLA batteries and up till last year ran a small compressor coolbox which drew 4.5Amps but it's duty cycle was typically 20~25%. With only LED lighting and modern low power draw instruments and Autopilot when sailing, I was generally OK for power but there were a few occasions when after several dreary days with no direct sunlight, I was getting a bit anxious and watched my usage like a hawk. I am in the process of upgrading the inbuilt 64Litre passive coolbox to a refrigerated box with hi-tech 25mm VIP panels (supposedly equivalent to 6~8 inches of blue foam) I have sold the portable coolbox. It will be interesting to see what my power usage will be.

[seandepagnier]

Originally Posted by SV__Grace

One 54 amp hour house battery is pretty tiny, even for a small boat, unless you have minimal electrical needs (such as an icebox instead of running a fridge compressor and little to no inverter use).

I have a 40 amp hour battery, power several computers, my 3d printer, and I also motor the boat using an electric outboard. This is actually plenty of capacity, and the lithium battery is much more efficiency and effective capacity.

You also need to plan for cloudy days. supplement your solar more often than with a larger house battery bank.

I use only solar only for last 12 years. I have seen more than 30 amps in direct sun, however in overcast I produce 3-4 amps. This way, I always have enough solar power despite the weather. The idea to "supplement solar" doesn't make much sense. From where do you supplement the solar?



So the advice is as usual backward. Most people have batteries banks that are too large powering inefficient things that they don't need. The self-discharge of a large bank alone is significant wasted power. The same people have not enough solar panels. Figure out how much power you need. For example, if you need 20 amp hours per day, divide this by 6 (hours in day) multiply by 12, and then multiply by 10 (to get 10 times as many solar panels and then you will have enough even in overcast)


So for 20 amp hours available per day, install 400 watts of solar.

[sailorboy1]

Need more battery!

[Martkimwat]

Originally Posted by seandepagnier

I have a 40 amp hour battery, power several computers, my 3d printer, and I also motor the boat using an electric outboard. This is actually plenty of capacity, and the lithium battery is much more efficiency and effective capacity.



I use only solar only for last 12 years. I have seen more than 30 amps in direct sun, however in overcast I produce 3-4 amps. This way, I always have enough solar power despite the weather. The idea to "supplement solar" doesn't make much sense. From where do you supplement the solar?



So the advice is as usual backward. Most people have batteries banks that are too large powering inefficient things that they don't need. The self-discharge of a large bank alone is significant wasted power. The same people have not enough solar panels. Figure out how much power you need. For example, if you need 20 amp hours per day, divide this by 6 (hours in day) multiply by 12, and then multiply by 10 (to get 10 times as many solar panels and then you will have enough even in overcast)


So for 20 amp hours available per day, install 400 watts of solar.

Cannot make sense of this, would you mind explaining where these various figures you have quoted come from, I think I get the six hour figure (it's the effective amount of power you will get from a solar panel per day based on its wattage rating, although some sites state 5 hours rather than 6 depending on your geographic location) but the other numbers don't mean a thing, you need to explain how you come up with those figures. Also, you have stated that you have a 40 Amp Hr battery but then go on to explain that it's a lithium battery, well if so it's equivalent to roughly a 80 Amp hr SLA. since you can discharge it to almost 0 SOC. unlike an SLA which can only be safely discharged to 50% SOC. An 80 Amp hr SLA is more than 50% larger than a 54Amp Hr battery and is quite common on small boats. His 54 Amp hr battery is the equivalent of a 27 Amp hr lithium pack. I have couple of 27 Amp Hr lithium packs (golf cart lithiums ) which I use for my electric outboard. they will each I've me a bout one hour of continuous running time at economical power (not full power) pushing my 8' foot dink at about 3.5 knots, so 3.5 Nm range for each. not a great deal, so unless you are only using your battery for local runs ashore, I think your figures are suspect.

[Greg K]

Originally Posted by francois.lavoie

I am wondering how I could augment my autonomy. Would there be a better alternative to the Aspenora?

Comments are appreciated.
Thanks

Yes, skip the fridge altogether. You don't need it. Sailed across the Atlantic without a fridge and now cruise with my wife on a 28 ft boat in the Med for weeks at a time without one. Perfectly fine. Zero energy issues.

[smac999]

Originally Posted by seandepagnier

I have a 40 amp hour battery, power several computers, my 3d printer, and I also motor the boat using an electric outboard. This is actually plenty of capacity, and the lithium battery is much more efficiency and effective capacity.



I use only solar only for last 12 years. I have seen more than 30 amps in direct sun, however in overcast I produce 3-4 amps. This way, I always have enough solar power despite the weather. The idea to "supplement solar" doesn't make much sense. From where do you supplement the solar?



So the advice is as usual backward. Most people have batteries banks that are too large powering inefficient things that they don't need. The self-discharge of a large bank alone is significant wasted power. The same people have not enough solar panels. Figure out how much power you need. For example, if you need 20 amp hours per day, divide this by 6 (hours in day) multiply by 12, and then multiply by 10 (to get 10 times as many solar panels and then you will have enough even in overcast)


So for 20 amp hours available per day, install 400 watts of solar.

Avg 30-40’ boats use 150-200ah a day. So your solution is 4000w of solar? Yah Great. I’ll just tow it on a barge.