Question about battery power

[carstenb]

Originally Posted by Na Mara

Carsten your consumption figures are a bit on the high side if you ask me for a standard cruiser. I count on roughly double my anchor usage including the autopilot when underway.

Offshore the plotter is often running dark (screen illumination off), the depth sounder is off, the radar is on standby, etc. Mostly all you need is your AIS, the occasional GPS fix, your VHF and autopilot plus tricolour.

Also in heavy weather a wind gen will be pumping out 20+ amps (assuming it’s a good one that doesn’t cut out over a certain wind speed) so they tend to work well with autopilots, ramping up production just as the pilot increases consumption. That’s not so much the case after the blow has gone through where the sea state lags the lull in wind but still on the whole the autopilots power usage will generally coincide with the wind gens power output.

Alternatively you can fit a hydro generator that will produce 15-25 amps so long as the boat is moving. I’m not doing this as I am the typical 85:15 sailor and I want something that produces power more than 15% of the time, but if you are regularly doing long trips then a hydro generator can be worth the trouble.

I agree my numbers for passage sailing are on the high side - it is a worst case assumption.

We also run with our chartplotter dark etc and save as much juice as possible. We almost never run radar - but we've had to when we were enveloped by fog (yes there was wind also) for several days.

Even at say half my numbers (350Ah) the batteries will be run down through the night - just start the engine for an hour or two.

This isn't rocket science - but better to have too much juice than too little

[valhalla360]

Originally Posted by Drek4

Yes I agree, research in progress, but the best information is from actual usage in the field, or might I say ocean. I think I will be on the higher end of consumption, being land locked for now it will take time to shed my excessive habits, I also read a lot of negative information of wind generators, but I was hoping that some models might be worth it, I guess I will concentrate on solar and go the route of 3 or 4 high amps good quality batteries or lithium.
Thank you, much appreciated.

Usage numbers from others can be useless. Unless they have the same usage pattern, it could cause you to overbuild or underbuild your system.

Far better to do an energy audit of your expected usage if you don't have the boat and the ability to measure YOUR usage.

As far as deep cycle vs automotive batteries, they are night and day different.
- Automotive starting batteries are designed to put out a lot of amps but for a short period of time (translation minimal amp-hours).
- Deep cycle batteries are designed to put lots of amp-hours but not a lot of amps (relative to starting batteries of the same size...no harm in using them to start a small sailboat motor if they can put out enough amps though)

[Drek4]

Originally Posted by valhalla360

Usage numbers from others can be useless. Unless they have the same usage pattern, it could cause you to overbuild or underbuild your system.

Far better to do an energy audit of your expected usage if you don't have the boat and the ability to measure YOUR usage.

As far as deep cycle vs automotive batteries, they are night and day different.
- Automotive starting batteries are designed to put out a lot of amps but for a short period of time (translation minimal amp-hours).
- Deep cycle batteries are designed to put lots of amp-hours but not a lot of amps (relative to starting batteries of the same size...no harm in using them to start a small sailboat motor if they can put out enough amps though)

Well I know that I'm more in the upper category of consumption (200ah+ anchored/docked), this maybe not the best comparison, but in my house I consume on average 12kw/day during the week and 20kw/day on the weekend and this is without air conditioning and/or heating because this is for the months of may and june, I only use the air conditioning in july and august, once it hits 27oC inside the house.
Heating october to april.
Electricity is relatively cheap where I live, if you compare to other countries.

[valhalla360]

Originally Posted by Drek4

Well I know that I'm more in the upper category of consumption (200ah+ anchored/docked), this maybe not the best comparison, but in my house I consume on average 12kw/day during the week and 20kw/day on the weekend and this is without air conditioning and/or heating because this is for the months of may and june, I only use the air conditioning in july and august, once it hits 27oC inside the house.
Heating october to april.
Electricity is relatively cheap where I live, if you compare to other countries.

So where did the 200ah come from? If that's actual measurements while anchored, it's a good starting point. Just need to update if you expect your usage to change in the future. It's just a number pulled out of your...., go back and do the energy audit.

Household consumption is really not comparable or relevant. There are lots of ongoing draws in your average house that would not be acceptable running on battery.

PS: Units count when doing engineering calculations. It's 12 "kwh" not "kw" per day. 20kw/day implies if you start the day at 0 kw draw it gradually increases to 20kw over the course of 24hr. Sloppy units often result in mistakes.

[Drek4]

Originally Posted by valhalla360

So where did the 200ah come from? If that's actual measurements while anchored, it's a good starting point. Just need to update if you expect your usage to change in the future. It's just a number pulled out of your...., go back and do the energy audit.

Household consumption is really not comparable or relevant. There are lots of ongoing draws in your average house that would not be acceptable running on battery.

PS: Units count when doing engineering calculations. It's 12 "kwh" not "kw" per day. 20kw/day implies if you start the day at 0 kw draw it gradually increases to 20kw over the course of 24hr. Sloppy units often result in mistakes.

Sorry the 200ah+ is an extrapolation from the feedback of others.
The kw should be kwh as per my electric bill, sorry for the typo.
But in the night the tv is always on, laptops x2, cellphone x2 charging, use water frequently, open fridge on a regular basis (thermostat set on colder), so on.

[valhalla360]

Originally Posted by Drek4

Sorry the 200ah+ is an extrapolation from the feedback of others.
The kw should be kwh as per my electric bill, sorry for the typo.
But in the night the tv is always on, laptops x2, cellphone x2 charging, use water frequently, open fridge on a regular basis (thermostat set on colder), so on.

Yeah, do an energy audit...extrapolating from what others use is likely to be wildly off.

On each device will be a sticker with the power consumption. I prefer to work in watt-hours, so you don't have to worry about voltage (you can use kwh but 1kwh is just 1000wh but makes more sense for the limited power in a battery bank).
- 5hr at 60w for TV = 300wh (update duration and wattage for your devices and expected use)
- 6hr at 50w for laptop = 300wh
- 4hr at 15w for cell charger = 60wh
- 0.25hr at 100w for water pump = 25wh
- fridge...
- lights...
- vhf....
- etc...

Add them up and you get the total watt-hours you need to generate each day.
- If it's an AC device add 10-20% to account for losses due to energy conversions
- Rule of thumb for solar is it puts out 4 times it's rated wattage in watt-hours (ie: a 100watt panel will generate 400 watt-hours each day). So your daily watt-hour consumption divided by 4 will give you a good lower limit for solar array size. In reality, it would be good to bump that up by 10-20% to account for
efficiency losses.
- Assuming lead-acid batteries, you don't want them below 50% charge, so if you have 200amp-hr 12v battery bank, you have 200amp-hr *12v * 50% = 1200wh of usable power if starting from a full charge. (lithium has more like 80% usable from the rated amp-hr but costs more and has some other complications setting up the charging system).
- How willing are you to start the motor and let the alternator top up the batteries if you have multiple overcast days? Say you want to go 3 days with the solar producing minimal amounts, triple your daily watt-hr number when sizing the battery bank. Also, you want to up the size of your solar array, so that it can catch up on the following sunny days.

This will give you a much more realistic starting point for setting up your system rather than SWAG (Scientific Wild Ass Guess) based on the size of other peoples systems.

[Drek4]

Originally Posted by valhalla360

Yeah, do an energy audit...extrapolating from what others use is likely to be wildly off.

On each device will be a sticker with the power consumption. I prefer to work in watt-hours, so you don't have to worry about voltage (you can use kwh but 1kwh is just 1000wh but makes more sense for the limited power in a battery bank).
- 5hr at 60w for TV = 300wh (update duration and wattage for your devices and expected use)
- 6hr at 50w for laptop = 300wh
- 4hr at 15w for cell charger = 60wh
- 0.25hr at 100w for water pump = 25wh
- fridge...
- lights...
- vhf....
- etc...

Add them up and you get the total watt-hours you need to generate each day.
- If it's an AC device add 10-20% to account for losses due to energy conversions
- Rule of thumb for solar is it puts out 4 times it's rated wattage in watt-hours (ie: a 100watt panel will generate 400 watt-hours each day). So your daily watt-hour consumption divided by 4 will give you a good lower limit for solar array size. In reality, it would be good to bump that up by 10-20% to account for
efficiency losses.
- Assuming lead-acid batteries, you don't want them below 50% charge, so if you have 200amp-hr 12v battery bank, you have 200amp-hr *12v * 50% = 1200wh of usable power if starting from a full charge. (lithium has more like 80% usable from the rated amp-hr but costs more and has some other complications setting up the charging system).
- How willing are you to start the motor and let the alternator top up the batteries if you have multiple overcast days? Say you want to go 3 days with the solar producing minimal amounts, triple your daily watt-hr number when sizing the battery bank. Also, you want to up the size of your solar array, so that it can catch up on the following sunny days.

This will give you a much more realistic starting point for setting up your system rather than SWAG (Scientific Wild Ass Guess) based on the size of other peoples systems.

That is an awesome and very detailed reply.
So according to all the wonderful information above, my night consumption will put me around 2600wh, thus requiring 2.2x 200ah batteries, so with 3x 200ah batteries in my bank I'm good to go and make sure to go lithium to have that extra reserve of power and a better durability.
Now for the solar panels that would bring me smack on 4x 200wh for a total of 800wh that will give me after loss around 2600wh of recharge power in a sunny day.
Thanks a million, I feel much better now, knowing this.

[Na Mara]

Valhalla’s numbers are good.

200W of solar in standard conditions will get about 800Wh of energy into your battery on an average per day and assuming a large enough battery this is about what a single wind turbine will do in 10kn average wind zones. Also his advice to look at the wattage of all your items and multiply them by the hours per day used is also an excellent way to calculate consumption. I would simply add that you should do this twice: once for at anchor and once for underway and dimension your system accordingly.

[Drek4]

Originally Posted by Na Mara

Valhalla’s numbers are good.

200W of solar in standard conditions will get about 800Wh of energy into your battery on an average per day and assuming a large enough battery this is about what a single wind turbine will do in 10kn average wind zones. Also his advice to look at the wattage of all your items and multiply them by the hours per day used is also an excellent way to calculate consumption. I would simply add that you should do this twice: once for at anchor and once for underway and dimension your system accordingly.

Well thank you, I will most certainly keep that in mind.

[akopac]

Unplug from the dock, use the boat for a 24 Hr day and see what your consumption is. Plan on rebuilding the frig./freezer box if you haven’t. Just my 2 cents. What’s cheaper foam insulation or batteries and charging resources?

[Drek4]

Originally Posted by akopac

Unplug from the dock, use the boat for a 24 Hr day and see what your consumption is. Plan on rebuilding the frig./freezer box if you haven’t. Just my 2 cents. What’s cheaper foam insulation or batteries and charging resources?

Yes I guess I could investigate insulating the sides that don't have the heat dissipation coil better for the refrigerator and freezer, after all they're a big chunk in the equation. They're both built in thought, remains to be seen how successful this endeavour would turn out, portable refrigerator/freezer are easier to insulate with a thick thermal blanket cut out to the right size and for the fan an opening.

[carstenb]

Originally Posted by Drek4

Yes I guess I could investigate insulating the sides that don't have the heat dissipation coil better for the refrigerator and freezer, after all they're a big chunk in the equation. They're both built in thought, remains to be seen how successful this endeavour would turn out, portable refrigerator/freezer are easier to insulate with a thick thermal blanket cut out to the right size and for the fan an opening.

if you are planning to sail in the tropics, convert your fridge to keel cooled. otherwise you air cooled compressor simply can't get rid of the heat since there will be little temperature difference between what it is trying to get rid of and the ambient temp in the boat.

[Drek4]

Originally Posted by carstenb

if you are planning to sail in the tropics, convert your fridge to keel cooled. otherwise you air cooled compressor simply can't get rid of the heat since there will be little temperature difference between what it is trying to get rid of and the ambient temp in the boat.

Thank you for the information.
I will have to research a little more before opting to change from air cool to water cool thought. Seems like time consuming, but maybe I'm wrong.

[sailorboy1]

Originally Posted by carstenb

if you are planning to sail in the tropics, convert your fridge to keel cooled. otherwise you air cooled compressor simply can't get rid of the heat since there will be little temperature difference between what it is trying to get rid of and the ambient temp in the boat.

Same can mostly be done with a fan to blow air from the bilge area to where the compressor is. I installed a $15 6" quiet fan for this and it has been running full time for 3 years. Much less trouble and cost than installing a keel cooler.

Just an option.

One of these days I will wire that aux fan to the aux circuit of the Danfoss control panel, but it would only save around 0.2A per hour

[Drek4]

Originally Posted by sailorboy1

Same can mostly be done with a fan to blow air from the bilge area to where the compressor is. I installed a $15 6" quiet fan for this and it has been running full time for 3 years. Much less trouble and cost than installing a keel cooler.

Just an option.

One of these days I will wire that aux fan to the aux circuit of the Danfoss control panel, but it would only save around 0.2A per hour

That's a great idea, Thank you very much for your input.