Vehicle fridge temperature impact in frunk

[sac602]

It turns off the 12v after 30 sec or so when there is no draw on it. When the fridge turns off (when it gets to temp) the battery does not sense any draw, it is so turns off. In my RTT I have a little let reading light on all the time to keep a draw. The Bodgga has a USB port on the control panel. I tried using a low profile led USB light, but it but that was not sufficient to keep it awake.

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[Brewbud]

It's strange that the power bank turns off the 12v output at all. If you look at the Li-Ion cells that make up most of these small power banks they are connected in a 4S, 12-14.6v arrangement. Outputting 12 volts could literally come straight from the cells without any boost or buck conversion. All you would need is a low cell voltage cutoff device to disconnect when cells get below 2.6 volts. Outputting 12-14 volts is the easiest thing the power bank can do.

You are assuming 4S but that is not the case. My GZ Lithium 1000 is 3S.

Some power banks out there will output a regulated 12V because some devices, such as fridges, will shut off early to protect the battery source. My ARB has 3 settings to protect the power source. Even at the low setting it would trip the fridges power protection circuit pretty quick.

 

[NY_Rob]

^ I'm assuming by the price-- your power bank is one of the better ones?
One negative to using a 3S arrangement is when you charge the cells to 3.6V (nominal level for Li-Ion cells) you only get 10.8v and are forced to run that through a boost converter to get 12V output where a 4S arrangement charged to Li-Ion "nominal" values of 3.6V (much easier on Li-Ion cells) to get 14.4 volts naturally.

The more common/inexpensive types use a 4S arrangement.. like the Jackery that uses a 7P4S arrangement as seen in the teardown video below:


I've watched teardown's of quite a few of the $300-$500 range power banks and they all use a 4S battery arrangement.

And that's why I find it odd that they cut the 12V power so quickly on the linked power bank when it senses no load, it's very easy and efficient for a 4S power bank to output 12V as that's very close to it's nominal cell voltage.

 

[Brewbud]

^ I'm assuming by the price-- your power bank is one of the better ones?
One negative to using a 3S arrangement is you have to charge the cells to 3.6V (max level for Li-Ion cells) to even get 10.8v and then run that through a boost converter to get 12V output where a 4S arrangement can be charged to Li-Ion "nominal" values of 3.2V (much easier on Li-Ion cells) to get 12.8 volts naturally.

The more common/inexpensive types use a 4S arrangement.. like the Jackery that uses a 7P4S arrangement as seen in the teardown video below:


I've watched teardown's of quite a few of the $300-$500 range power banks and they all use a 4S battery arrangement.

And that's why I find it odd that they cut the 12V power so quickly on the linked power bank when it senses no load, it's very easy and efficient for a 4S power bank to output 12V as that's very close to it's nominal cell voltage.

Mine is the Goal Zero 1000W Lithium with the 1500W/3000W peak inverter. It has a MPPT solar charger. I was surprised it was 3S when I first bought it.

 

[NY_Rob]

^ yes, 3S for a power bank is not really optimal as most of the energy in li-ion batts is stored and delivered at/near it's "nominal" voltage of 3.6V which means in a 3S config your running at 10.8V nominal voltage and everything (except 5V DC for the USB ports) has to be boost converted up which is energy inefficient and also severly current limiting.

I have built "power bank" units that fit in the Harbor Freight 50cal plastic ammo boxes that can deliver 75Ah at 12V or 375 amps at 12V for 10 sec. Try that from a boost converter running off 3S li-ion cells... it will not happen.

I just ordered four of these... should make a great jump starter/power bank:
https://batteryhookup.com/products/new-4-pack-eve-3-2v-75ah-240wh-lifepo4

 

[bowhunter]

We've had some high temperatures the past few days and I wanted to see how my powered cooler performed in an enclosed space in hot weather. I plugged the cooler into the 110 AC outlet in the gear tunnel to ensure it was constantly powered.

Below are 2 graphs. The top one is the temperature inside the gear tunnel and the bottom one is the temp inside the cooler.

Sunday had a high of 98 and today had a high of 94. The exterior temperature peaks around 6 pm. The cooler had 1 layer of beverage cans standing vertically. I placed them in the cooler warm Saturday evening which is why the cooler shows the slow decline Saturday night. I'm not quite sure why the temp jumped a couple degrees this morning, but it coincides with when I drove the vehicle.

On Sunday the vehicle was in the shade until about 4 pm whereas today it was in the sun all day (cabin heat was reporting 131 degrees at one point when I looked at it). The temp dropped at 5:30 pm today after I had opened the gear tunnel and cooled the cabin to drive.

Interestingly the tunnel stayed 5 to 10 degrees below the exterior temperature when the vehicle was parked in the shade leading me again to conclude the fridge generated heat is negligible in the enclosed space and was happy to see that It was able to keep the temperature under 40 degrees through the heat.

 

[DJG]

We've had some high temperatures the past few days and I wanted to see how my powered cooler performed in an enclosed space in hot weather. I plugged the cooler into the 110 AC outlet in the gear tunnel to ensure it was constantly powered.

Below are 2 graphs. The top one is the temperature inside the gear tunnel and the bottom one is the temp inside the cooler.

Sunday had a high of 98 and today had a high of 94. The exterior temperature peaks around 6 pm. The cooler had 1 layer of beverage cans standing vertically. I placed them in the cooler warm Saturday evening which is why the cooler shows the slow decline Saturday night. I'm not quite sure why the temp jumped a couple degrees this morning, but it coincides with when I drove the vehicle.

On Sunday the vehicle was in the shade until about 4 pm whereas today it was in the sun all day (cabin heat was reporting 131 degrees at one point when I looked at it). The temp dropped at 5:30 pm today after I had opened the gear tunnel and cooled the cabin to drive.

Interestingly the tunnel stayed 5 to 10 degrees below the exterior temperature when the vehicle was parked in the shade leading me again to conclude the fridge generated heat is negligible in the enclosed space and was happy to see that It was able to keep the temperature under 40 degrees through the heat.

What make/model fridge and what temp was the fridge set to? That's still quite a spike in fridge temp that might be undesirable but hard to rule without knowing what the target was.

Does your fridge experience similar spikes in a "normal" non-conditioned environment (i.e. outside), or is this spike caused by the limited ventilation/circulation environment in the tunnel? Higher quality fridges would never see spikes like that, even in 100+ temps in the sun.

Depending on the answers to these questions, a fridge may or may not be viable in the tunnel. For example, if it was set to 32-33, a spike to 39 would be unacceptable if it meant that if I set it to 38 it could spike to 45 and ruin the contents (assuming a constant value of "spike" which isn't a given).

I'm also really curious about what almost appears to be an immediate spike in fridge temp Monday morning, when according to the graph, the tunnel temp was still in decline and didn't start a gradual rise until later. Even if the tunnel temp had already spiked, the fridge should be able to stretch out a temp rise.

 

[DJG]

^ I'm assuming by the price-- your power bank is one of the better ones?
One negative to using a 3S arrangement is when you charge the cells to 3.6V (nominal level for Li-Ion cells) you only get 10.8v and are forced to run that through a boost converter to get 12V output where a 4S arrangement charged to Li-Ion "nominal" values of 3.6V (much easier on Li-Ion cells) to get 14.4 volts naturally.

The more common/inexpensive types use a 4S arrangement.. like the Jackery that uses a 7P4S arrangement as seen in the teardown video below:


I've watched teardown's of quite a few of the $300-$500 range power banks and they all use a 4S battery arrangement.

And that's why I find it odd that they cut the 12V power so quickly on the linked power bank when it senses no load, it's very easy and efficient for a 4S power bank to output 12V as that's very close to it's nominal cell voltage.

Jackery updated the unit shown in that video (which was from 2019). It now has a regulated 12v plug. I tested it on my fridge, running it down to 1%. Voltage measured on the fridge was planted at about 13.3v the entire time (it actually spiked slightly to 13.5-13.6v at around 6% for a brief moment), and the fridge never shut off.

 

[bowhunter]

What make/model fridge and what temp was the fridge set to? That's still quite a spike in fridge temp that might be undesirable but hard to rule without knowing what the target was.

Does your fridge experience similar spikes in a "normal" non-conditioned environment (i.e. outside), or is this spike caused by the limited ventilation/circulation environment in the tunnel? Higher quality fridges would never see spikes like that, even in 100+ temps in the sun.

Depending on the answers to these questions, a fridge may or may not be viable in the tunnel. For example, if it was set to 32-33, a spike to 39 would be unacceptable if it meant that if I set it to 38 it could spike to 45 and ruin the contents (assuming a constant value of "spike" which isn't a given).

I'm also really curious about what almost appears to be an immediate spike in fridge temp Monday morning, when according to the graph, the tunnel temp was still in decline and didn't start a gradual rise until later. Even if the tunnel temp had already spiked, the fridge should be able to stretch out a temp rise.

It is an Alpicool C20. The target temp is 37 in "max mode", but even under normal conditions it doesn't hold tight to that and spends most of its time between 33 and 35. The spike is interesting as it did it again this morning coinciding to when I drove it. I plan on putting an energy monitor on the outlet to see if anything unexpected is occurring with the power supply.

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