Daily Power Requirements...

Wxx3 · May 13, 2014

my draw for the Vitrifrigo Fridge and Freezer seems to average about 5 amps an hour or 120 amps, 1440 watts per 24 hours.

In the coming days, i will post a more detailed analysis. The addition for the solar panels has also made a huge difference.

sunchaser · May 13, 2014

JDCAVE said:
We are going to be away from reliable food stores for several months at a time so prefer these fridge and freezer units.

Nowhere in the PNW are you away from reliable food stores months at a time. Days maybe, weeks at the most if you're a hermit. The whole area is set up to supply workers and fun seekers on the water.

Years ago we overstocked badly when traveling in the PNW and agonized over how to keep stuff frozen, it turned out to be not a concern and freezer size and needs dropped a lot.

We have some friends on a KK42 who justified a huge freezer for dog food storage :nonono:

different strokes.

FF · May 14, 2014

If I stay with the current size of bank, it would be prudent to fire up the generator after 36 hour or so.

The fastest charge from the noisemaker will come from a large alternator belted on to it with a smart V regulator .

IF your set is over 10KW , a large 150 A or more big buck battery charger Might be able to match the charge of a 135A alt.

The question then becomes TIME.

Will you pay 2x for batts that can accept a higher RATE of charge to lower noisemaker operating hours?

NOT requiring the energy is always cheaper than creating/storing it.

Extra insulation on the reefer?

ksanders · May 14, 2014

In my opinion... This whole power system thing that folks get into tends to miss the point completely from an engineering prospective.

The key to success is to size your battery bank, your charger, and your generator to compliment each other. Daily loads don't much matter from an engineering standpoint unless you have a pre-conceived "cycle time" target in mind, (as long as you can meet your peak load requirements)

Then, and only then is it prudent to look at your actual daily loads in an effort to lengthen your cycle time.

I'm going to use our boat as an example of a properly engineered power system.

We have...

840 amp hours of house bank
150 amp inverter/charger
9 KW generator

Everything is sized to work together.

Our battery bank can accept our chargers full output current, and recharge our battery bank in practice in a reasonable amount of time.

Our generator can supply the full current requirement of the charger, plus all the other loads we have on the boat.

Our actual DC loads are not relevant to this system design for the most part. All they do is determine how often we need to go in to a charge cycle.

JDCAVE · May 14, 2014

FF. Yes, I have insulated the refer units as best as I can. Also added 1inch high density foam on the doors.

House bank is 1125 (10 T-105's). Genset is a near new Entec West 4.1 kW, so it's small and it seems to be able to handle the charger. Inverter charger is an older Freedom 20, 100 amp. I'm expecting to cycle the batteries 50-80% SOC. 1-2 hours on the genset at 0.5 GPH. Will heat the water at the same time.

timjet · May 14, 2014

ksanders;233843 Our actual DC loads are not relevant to this system design for the most part. All they do is determine how often we need to go in to a charge cycle.[/QUOTE said:
Another example:
I have only 420 ah house bank.
100 amp charger.
Daily DC load is about 250 amps per day.

250 amp load will require a genny run time of 2.5 hrs but with inefficiencies probably 3 hrs or more.

So I run the genny 1.5 hrs in am and again in pm.

If I plan on running the boat then the genny gets a rest as the 2 100 amp alternators will replenish the dc amps used in 1.5 hrs.

ksanders · May 14, 2014

timjet said:
Another example:
I have only 420 ah house bank.
100 amp charger.
Daily DC load is about 250 amps per day.

250 amp load will require a genny run time of 2.5 hrs but with inefficiencies probably 3 hrs or more.

So I run the genny 1.5 hrs in am and again in pm.

If I plan on running the boat then the genny gets a rest as the 2 100 amp alternators will replenish the dc amps used in 1.5 hrs.

Exactly!

Your system appears to be well designed, IE everything works together well

If you increased the size of your house bank you would probably want to increase your charger as well for example.

ksanders · May 14, 2014

JDCAVE said:
FF. Yes, I have insulated the refer units as best as I can. Also added 1inch high density foam on the doors.

House bank is 1125 (10 T-105's). Genset is a near new Entec West 4.1 kW, so it's small and it seems to be able to handle the charger. Inverter charger is an older Freedom 20, 100 amp. I'm expecting to cycle the batteries 50-80% SOC. 1-2 hours on the genset at 0.5 GPH. Will heat the water at the same time.

If I'm reading your post correctly...

You intend to cycle between 50% and 80% on your 1125 amp hour battery bank?

So you'll start recharging at 50% or 562 amp hours remaining.
You'll stop charging at 80% or 900 amp hours remaining.
So, during your charge cycle you're planning on replacing 338 amp hours.

Your charger is 100 amps max, but it really wont put out exactly 100 the whole recharge time, but we'll use that number for calculation sake.

You're looking at a generator run time of 3 hours 20 minutes, minimum. You're really looking at probably more like 4 or 41/2 hours.

If you're expecting 1-2 hours (as in your post) of generator run time, that is not possible.

FF · May 15, 2014

Your charger is 100 amps max, but it really wont put out exactly 100 the whole recharge time,

Agreed , most old small chargers are not capable of creating their rating for many minuets , never mind holding 100A for hours!

My guesstimate is at least 4 hours , probably 5 hours to go from 50% to 80% or 85%.

A SOC meter will tell everything required as this is attempted.

After a couple of weeks of cruising I hope the actual results are posted.

Armchair guesstimates relying on company advertising seldom come true.

Will be interesting to learn the percent of charge that is done by the main engine as the boat travels.

JDCAVE · May 16, 2014

Thanks everyone. I've got a better idea of things now, than I had last summer that for sure. I've gone through the power draw calculations again with a cycle time on the fridge and freezer of 12 hours per day. That works out to 120 amp hours per day. Other systems another 60 for a total of 185 amp hours.

The reality is I have a 4.1 kW genny and a 100 amp charger. It seems to run at about 75 plus amps, so that would indicate a genny runtime of 3-4 hours.

Jim

FlyWright · May 16, 2014

This week I conducted a power audit on my dorm-style fridge which sits secured on my countertop. I ran it for 24 hrs full of food on a Kill-a-watt meter with outdoor temps rising into the 90s. It's daily consumption was 900 watts. At 12V, that's 75AH without inverter inefficiencies added, so I'd call it a conservative 85AH daily load on the batteries. That represents about 50% of my daily load of 165-175AH.

ksanders · May 16, 2014

FlyWright said:

Curious....

Nice fridge...

Looks Heavy...

Is it bolted down?

FlyWright · May 16, 2014

ksanders said:
Curious....

Nice fridge...

Looks Heavy...

Is it bolted down?

It's not really that heavy after I drink all the beer inside.

That was an early picture of my initial test. It worked, but needed refinements to secure it and allow the door to clear the fiddling. It is now secured in place with a door latch added.

That counter contains the only equipment powered by my inverter. The rest of the essential equipment is 12V and propane. Soon I'll install a switch to allow easy switching between shore/gen and inverter for that one counter top.

Daily Power Requirements...

Wxx3

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