4 ms·

> Using a supercapacitor to provide power while shutting down on loss of solar power, instead of the current few minutes of use of batteries. I wonder why this

> Using a supercapacitor to provide power while shutting down on loss of solar power, instead of the current few minutes of use of batteries. I wonder why this is necessary. I've also seen it mentioned in the wiki, but no explanation. Isn't a compressor the only electrical thing in a fridge? I know you must be careful with leaving some time between restarts, but why can't you just shut it down immediately on power loss?

Scoundreller 8y ago
I thought so too. Even if they’re all mechanical, it usually makes sense to keep the fan running across the evaporator to prevent moisture buildup (which will then sit in a place susceptible to freezing). It can also be more efficient to push this residual cold into the vessel. My car’s AC gets funky if I don’t remember to turn off the AC a few minutes before shutting down.
- mulmen 8y ago
  I think there is a drain near the condenser to prevent this, if your car smells nasty after turning off your A/C you may want to make sure that’s not clogged. Also, if equipped on your car replace the cabin air filter.
  - Scoundreller 8y ago
    It drips underneath on a muggy day, so I assume it's draining OK. My main gripe is that they don't auto-run the fan for 3-4 minutes after key-off.
lambda 8y ago
https://fridge0.branchable.com/battery_bank/ https://fridge0.branchable.com/battery_bank/ > Fridge0 does not need a big battery bank, since it stores cold in its thermal mass and runs only when solar power is available. > But, at least a mimimal battery is needed to run the computer control. Probably on the order of 5 watts for a computer like a raspberry pi; this could be reduced more with a more embedded computer like an arduino. > Enough battery to run the fridge for a minute or two is also needed. Consider what happens when the fridge is running, and the sun goes behind a rain cloud. Suddenly, there's not enough power to run it, but it's still turned on. The inverter will try to run with whatever small solar power is still coming in, but it's not enough. Some inverters might manage a clean power off, probably accompanied with loud beeping. Other inverters might fail in more interesting ways. > To deal with this situation, the computer needs to check the incoming solar power frequently, and power off the fridge if there's not enough. The battery is needed to keep the inverter and fridge running until that happens. Basically, it sounds like the answer is because with a solar panel, there are states that are between "off" and "on," you rather just get an amount of power proportional to the amount of sunlight, and there's a concern that those states could cause problems if you don't provide a more constant power supply and active switching to fully shut off the power when your solar panel is not producing enough power for the "on" state.
- nerpderp82 8y ago
  https://en.wikipedia.org/wiki/Hysteresis https://en.wikipedia.org/wiki/Hysteresis and Power Sequencing https://en-support.renesas.com/knowledgeBase/16978575 https://en-support.renesas.com/knowledgeBase/16978575
  - lambda 8y ago
    Thanks for the references! I'm familiar with the concept of hysteresis, but hadn't been familiar with the idea of power sequencing for MOS devices, such as the VDD + 0.6V maximum ratings or latch-up. That's good to know!

Scoundreller 8y ago

I thought so too. Even if they’re all mechanical, it usually makes sense to keep the fan running across the evaporator to prevent moisture buildup (which will then sit in a place susceptible to freezing). It can also be more efficient to push this residual cold into the vessel. My car’s AC gets funky if I don’t remember to turn off the AC a few minutes before shutting down.

mulmen 8y ago
I think there is a drain near the condenser to prevent this, if your car smells nasty after turning off your A/C you may want to make sure that’s not clogged. Also, if equipped on your car replace the cabin air filter.
- Scoundreller 8y ago
  It drips underneath on a muggy day, so I assume it's draining OK. My main gripe is that they don't auto-run the fan for 3-4 minutes after key-off.

lambda 8y ago

https://fridge0.branchable.com/battery_bank/ https://fridge0.branchable.com/battery_bank/ > Fridge0 does not need a big battery bank, since it stores cold in its thermal mass and runs only when solar power is available. > But, at least a mimimal battery is needed to run the computer control. Probably on the order of 5 watts for a computer like a raspberry pi; this could be reduced more with a more embedded computer like an arduino. > Enough battery to run the fridge for a minute or two is also needed. Consider what happens when the fridge is running, and the sun goes behind a rain cloud. Suddenly, there's not enough power to run it, but it's still turned on. The inverter will try to run with whatever small solar power is still coming in, but it's not enough. Some inverters might manage a clean power off, probably accompanied with loud beeping. Other inverters might fail in more interesting ways. > To deal with this situation, the computer needs to check the incoming solar power frequently, and power off the fridge if there's not enough. The battery is needed to keep the inverter and fridge running until that happens. Basically, it sounds like the answer is because with a solar panel, there are states that are between "off" and "on," you rather just get an amount of power proportional to the amount of sunlight, and there's a concern that those states could cause problems if you don't provide a more constant power supply and active switching to fully shut off the power when your solar panel is not producing enough power for the "on" state.

nerpderp82 8y ago
https://en.wikipedia.org/wiki/Hysteresis https://en.wikipedia.org/wiki/Hysteresis and Power Sequencing https://en-support.renesas.com/knowledgeBase/16978575 https://en-support.renesas.com/knowledgeBase/16978575
- lambda 8y ago
  Thanks for the references! I'm familiar with the concept of hysteresis, but hadn't been familiar with the idea of power sequencing for MOS devices, such as the VDD + 0.6V maximum ratings or latch-up. That's good to know!