Adetheheat
Member
When the engine off how long could we expect to run a small fridge on a boat ? Overnight or just a few hours. The boat is a Beneteau antares 750
Fridge powered by boat battery
- Thread starter Adetheheat
- Start date
PaulRainbow
Well-known member
Impossible for anyone to answer that with any real accuracy.
Need to know what the fridge draw is and how many AH the battery is., plus, how long does the fridge run for in an hour.
So let's say the fridge draws 4a and runs for 1/3rd of the time, in 24 hrs it will run for a total of 8 hours at 4a, = 32ah.
If your battery is 100ah it will technically be able to supply 50ah to a depth of discharge of 50% (the most you'll want to go to). In the real World, allowing for some inefficiencies and the likelihood the battery isn't brand new and perfect, so won't deliver it's full 50Ah, 24hrs would be your lot.
Substitute my "assumptions" that the fridge draws 4a, runs for 1/3rd of the time and you have a 100ah battery with real figures and you can work your answer out.
ChromeDome
Well-known member
When you know the consumption (see fridge specs) and the available battery type & capacity, it is a matter of calculation.
Most fridges have a built-in feature to shut it off when the voltage drops to a certain level, to prevent the battery from going flat (and potentially prevent starting the engine.
It is quite common to install separate battery banks for domestic consumption and engine needs, separated by a switch (pref. automatic).
Btw a battery bank can consist of only one battery, but it is recommended to use battery types designed for the use. The demand is completely different on consumption (low, long time drain) and starter (big, short time drain) batteries.
Most fridges have a built-in feature to shut it off when the voltage drops to a certain level, to prevent the battery from going flat (and potentially prevent starting the engine.
It is quite common to install separate battery banks for domestic consumption and engine needs, separated by a switch (pref. automatic).
Btw a battery bank can consist of only one battery, but it is recommended to use battery types designed for the use. The demand is completely different on consumption (low, long time drain) and starter (big, short time drain) batteries.
wingcommander
Active member
Would need a tad more information, ie battery bank size and power consumption of fridge
Edit . Too slow at typing
Edit . Too slow at typing
jac
Well-known member
So many variables, size, efficiency, temperature, battery size etc - as an approximation - ours used 5 amps when the compressor was running which was roughly 1/3 of the time so about 40 Ah use in 1 day in summer.
You then need to work out what else will be drawing from the battery and how big the battery is, remembering that once the battery gets down to 50% SOC it is dead and you will do well to get it much over 80% - 85% on a day to day basis with the boat in use.
So if you figure that you have roughly 1/3 of the nominal battery capacity available then 120 Ah of battery will power the fridge for 24 hours if nothing else is running
You then need to work out what else will be drawing from the battery and how big the battery is, remembering that once the battery gets down to 50% SOC it is dead and you will do well to get it much over 80% - 85% on a day to day basis with the boat in use.
So if you figure that you have roughly 1/3 of the nominal battery capacity available then 120 Ah of battery will power the fridge for 24 hours if nothing else is running
Boater Sam
Well-known member
If its an adsorption type, not very long at all
ChromeDome
Well-known member
Might be, but the calculation is the same, regardless of the consuming device. Compressor fridge, absorption cooler, heater, TV, lamp etc.
LadyInBed
Well-known member
Also not forgetting at what temperature you set the thermostat to will dictate how often the fridge power cycles.
seumask
Well-known member
Small boat and small fridge in the absence of charging on a reasonable average 100 AH battery in my book, a day would be fine but 2 days would be too long and the hotter and less well insulated your fridge is the the less time you have. Overnight should be fine .
If the battery is old and worn out you may find you only get a couple of hours.
If the battery is old and worn out you may find you only get a couple of hours.
Momac
Well-known member
As already said really....
One 100Ah battery (i good order) per fridge per day.
Maybe longer in cool weather
Maybe less time in hot weather
.
One 100Ah battery (i good order) per fridge per day.
Maybe longer in cool weather
Maybe less time in hot weather
.
Adetheheat
Member
Thanks all
GHA
Well-known member
No maybe about it ? , temperature can make a huge difference, the more insulation the better ..
mattnj
Well-known member
The best solution on that boat is fill the roof with solar panels, I have 200w on my roof and happily runs the fridge 24/7 in the summer time...i leave it on 7 days a week.
wingcommander
Active member
Also keep it full , always replace the larger tins with bottles of water until you re-stock with more larger
vyv_cox
Well-known member
I run my Danfoss 35 powered fridge 24/7 for months in Greece. When I had a 2 x 110 Ah domestic bank its voltage was down to 12.0 first thing in the morning. Increasing to 3 X 110 Ah the morning voltage is 12.4.