Measuring and Recording Refrigerator Temperatures

[Cate&Rob]

The only measure that makes sense WRT energy consumed (or battery power used) is Ah (amp hours). Amps is an instantaneous measure of the current being drawn at that moment in time. 3 amps for an hour is 3 Ah. 30 amps for 10 hours is 300 Ah.

Rob

[TucsonJim]

The only measure that makes sense WRT energy consumed (or battery power used) is Ah (amp hours). Amps is an instantaneous measure of the current being drawn at that moment in time. 3 amps for an hour is 3 Ah. 30 amps for 10 hours is 300 Ah.

Rob

Yep - And in regards to my battery bank. When I've used 300 amp hours, I'm empty. That could be in two hours or two weeks.

Jim

[Yattr]

Wow - Those results really demonstrate a few things.

1. It would be good to have a circulating fan running to even out the temperatures.
2. You can certainly see the small spikes of when the unit went into cooling mode.
3. I think I can tell when you opened the door.

It appears to have an ~20 minute cycle. We are currently in Grover Beach, CA at an elevation of 23' with temperatures between 40s and 60s.

Yes, opening the door does have a significant effect with a slow recovery time for the lower refrigerator section.

It will be interesting to compare these result to our other 367BHS Dometic 4-door this coming summer when we are back in Eagar, AZ (May through October). Only had it for a few weeks before winterizing it.

It is interesting that this unit never cooled well. This last summer it started acting up so I went through thermistor then circuit board replacements. Hard to believe that changing the circuit board could have such a major impact. The original circuit board must of been marginal...

[howson]

The only measure that makes sense WRT energy consumed (or battery power used) is Ah (amp hours). Amps is an instantaneous measure of the current being drawn at that moment in time. 3 amps for an hour is 3 Ah. 30 amps for 10 hours is 300 Ah.

Rob

So when I see a percentage on my BMV-712, it is reflecting the aH I have left in the batteries, right? For example, I'm usually around 35% after a full day towing with the refrigerator on. That means I have 140aH left in my 400aH battery pack (4 ea 100aH Battle Borns). If that's not right I've been royally dorking up my documentation...

My initial reaction is if that DC refrigerator only consumed 63aH in 24 hours I should forget about tapping power from the truck or adding solar--I should swap out my refrigerator! That alone is going to save a LOT of power.

To figure out how much I'm going to run my Dometic tomorrow and attempt to duplicate TucsonJim's experiment.

I can't duplicate exactly as I only have one measuring device. It will also deviate as I'll measure during the refrigerator's cool down cycle (should be maximum consumption) and only for ~10 hours as I think that's the maximum I can get on inverter power only. (I guess I could hook up my Kill-A-Watt but I'd rather measure the DC consumption.)

[Cate&Rob]

So when I see a percentage on my BMV-712, it is reflecting the aH I have left in the batteries, right?

This assumes that you set up your Victron Battery Monitor with the parameters of your battery bank. The battery monitor is measuring amps in and amps out and presenting whats left as a percentage of the number that you entered as bank usable capacity.

Rob

[howson]

This assumes that you set up your Victron Battery Monitor with the parameters of your battery bank. The battery monitor is measuring amps in and amps out and presenting whats left as a percentage of the number that you entered as bank usable capacity.

Rob

I'm 99.9% sure I've got it right.

[Cate&Rob]

I'm 99.9% sure I've got it right.

I'm 100% sure that you do .

Rob

[Country Campers]

Cate&Rob , TucsonJim , howson

Could you all pull out this battery info and start a post on battery usage and control? This may be helpful to all of us with little understanding of the actual operation of a battery.

Brian

[Guest]

What an interesting project. The graphical representation is very cool. Pun intended.

Jim

[howson]

TucsonJim
I cooled down the Dometic overnight. I started with a completely shut down refrigerator. I put in six 12 oz drink cans that were pre-cooled in the house and three ice packs in the freezer. The sensor went on the top right shelf.



The chart below shows the results.



The 358aH consumed over the 10.37 hours is "normal" based on the tracking I've done while towing. On average, historically my setup consumes ~30a/H. (!)

I'm still in shock that the refrigerator you're testing only consumed 63aH over 12 hours! Edit: As noted in Jim's post below the timeframe was 24 hours, not 12! Even more amazing.

Note the slight discrepancy from the BMV-712 reported aH consumption (360-2=358) to my calculation (400-(400aH * 7%) = 372). I suspect the percentage shown causes a rounding error.

Addendum: I turned off all the circuit breakers in the distribution panel other than the mains and the refrigerator. Obviously the inverter is responsible for some of the power consumption. In addition, I have extra fans running (via ARP's Fridge Defend), but the results above are consistent with previous experience.

[howson]

[USER="4"]The chart below shows the results.

Cate&Rob -- you did note I added C to the chart in addition to the "archaic" F, right?

[Cate&Rob]

Cate&Rob -- you did note I added C to the chart in addition to the "archaic" F, right?

I did notice that .

BTW, your fridge power draw is in line with the (smaller) residential fridge that we have on our boat. Through the inverter it draws about 30 amps at 12VDC when the compressor is running. This is typically a 50% duty cycle, but in cool down mode (as you tested) the compressor could easily run continuously for 10 hours, consuming something like 300 Ah.

Rob

[TucsonJim]

I'm 99.9% sure I've got it right.

Howard - According to Battle Born's Blog, the battery capacity should be set at 99Ah for each battery. So a bank of four batteries would be set at 396Ah. Here is a link to the blog:

https://battlebornbatteries.com/conf...etooth-dongle/

Jim

[TucsonJim]

TucsonJim
I cooled down the Dometic overnight. I started with a completely shut down refrigerator. I put in six 12 oz drink cans that were pre-cooled in the house and three ice packs in the freezer. The sensor went on the top right shelf.



The chart below shows the results.



The 358aH consumed over the 10.37 hours is "normal" based on the tracking I've done while towing. On average, historically my setup consumes ~30a/H. (!)

I'm still in shock that the refrigerator you're testing only consumed 63aH over 12 hours!

Note the slight discrepancy from the BMV-712 reported aH consumption (360-2=358) to my calculation (400-(400aH * 7%) = 372). I suspect the percentage shown causes a rounding error.

Addendum: I turned off all the circuit breakers in the distribution panel other than the mains and the refrigerator. Obviously the inverter is responsible for some of the power consumption. In addition, I have extra fans running (via ARP's Fridge Defend), but the results above are consistent with previous experience.

howson

Howard - The 63 amp hours used was over 24 hours, not 12!
I've performed several other tests so far, with some pretty good results. One that is pretty eye opening is my 24 hour worst case experiment.

I set the refrigerator and freezer sections to "5" which is the coldest setting, and set the fireplace at 90°F. It only used 92 amp hours.

Then, I turned on the solar charging and just let the refrigerator run with a setting of "3". The solar bank brought the batteries up to full charge each morning, and maintained them throughout the day. During the night time hours, the refrigerator drew about 30 amp hours.

Unfortunately, this is only a single door refrigerator with about 10 cubic feet of space. So it wouldn't fit into your four door refrigerator space.

Jim

[OffToHavasu]

Wow. If they can only make a replacement (or modification) for the double door Norcold.