Using a chest freezer and temp controller for battery temp control

[efficientPV]

I run a chest fridge. Some have the condenser coils on the top and others on the bottom. Both can cause a lot of temperature stratification. I use a small computer fan to circulate air to keep it even. Turn the compressor on for only timed periods and let the fan do its job. Otherwise the batteries will see wide temperature swings. My current fridge has the condenser coils on the bottom and everything down there freezes even with the fan.

 

[Browneye]

Look up freezer temp controller. A johnson controller would work.

An upright freezer is another option, and they have a bottom drain for any coil condensation. I too am a home-brewer and have two of these, and two of the Johnson controllers - they're outstanding. I keep one at 65* for fermenting, also our bread, fruit, and alkaline batteries live in there. The other is at 33*, and holds up to four 'corny kegs', or 5gl beer kegs, with CO2 piped in, and taps in the door. Also takes overflow refer items from the big kitchen fridge.

The additional benefit of an upright is the ease of servicing and placing your lifepo cells. For me, lifting 6gl carboys over a chest freezer would be nigh impossible from past shoulder and back injuries.

These 'live' in my living room. Yes, we drink a lot of beer. LOL
Well, our friends do anyway.

Oh, and they've been running on a controller for the past four years, so compressor life doesn't appear to be an issue. They were both used freezers picked up off craigs, one was $100, the bigger one was almost new and $150. The controllers are about $60. You just set the freezer to full-cold. There are other more fancy electronic ones, but they cost more and I like the simple analog/mechanical approach to these. They're extremely reliable.

OTO, we just got one of those 5cubic foot chest freezers for extra storage in the garage, and it pulls 100w when it runs, about 20% duty cycle. At zero degrees F. Simply amazing. My Delta Mini can run it in a grid-down event.

Controller...it plugs into the wall, the freezer plugs into the adapter plug, and the controller powers on the refer when it needs to cool:





My 'kegerators'...Browneye Brewing Co. ?

 

[Bluedog225]

Good info here. Esp about the drain hole and lifting issues for chest freezers.

Server rack batteries in an upright makes sense.

 

[burgerking]

I am so tempted to do this myself.
A chest type freezer large enough for 32 pcs of 280AHs costs no more than $400.
But cost of raw material to build a 2 rough boxes would cost me $200... Hmm

 

[Samcat]

Thermoelectric and liquid cooled plate under the cells with good insulation around is the best solution....no need for top cover ( unless needed for esthetic reasons) . It may be complicated but small liquid pump, Thermoelectric unit ,cooling plate and hoses is all you need. There are aftermarket affordable solutions available. Implementing thermostat and analog switch boards are easy and reliable solution. Just my thoughts.
I usually always go for split air conditioning with variable speed compressor if there is inverters Mppt and other components that produce heat. This way you have batteries and everything else under temperature you like to see 24/7

 

[Bluedog225]

There was a reply in another thread where a guy who claimed refrigeration experience said running a freezer at ambient temps would screw the compressor. Seemed credible.

 

[Browneye]

My used freezers have been in use for five years with external controllers without issue.

What is the difference with using a thermostat or power shut off on the compressor?

 

[Bluedog225]

Here is the response. I’d be very interested in knowing if this was the case.
@shopman

 

[Browneye]

I would not buy an $800 freezer to house your batteries. I would put them in an air conditioned room and set it to 85*.

 

[Warpspeed]

I doubt if condensation will ever become a problem.

Sure, when you open the lid, humid air will enter and condense over everything inside.
But once you close the lid again, the temperature inside will fall, the wet cells will quickly dry out, and the water will re-condense on the coldest object it can find, which will always be the be the evaporator.

The cells will always dry out, as they will always be well above freezing !

As the compressor cycles, the evaporator will drip where there is usually a drip tray and a drain provided for that purpose.

The unusually high load on the compressor at start up is definitely not ideal, but if the lid is normally left closed, short cycling of the compressor should never occur.
The insulation is so good, and the temperature differential between inside and outside so low, the compressor duty cycle should be unusually low.

I think its a splendid idea.

 

[Browneye]

The temp controllers have enough delay built in as to prevent frequent cycling. And if the temp is set to be the same as ambient then what's the point?
Everyone is WAY over-complicating this as usual.

 

[Bluedog225]

I thought his point was that the freezer compressor was designed to operate a freezing internal temp. And that it was (much) more stressful on that system design to run it at a higher temperature (around 75 F).

I don’t know enough about the topic to know if that is true.

 

[Browneye]

How does the compressor know what the temperature is?
I'm calling BS. Sorry.

Yes, if you use a controller that switches a freezer compressor on and off frequently you'll likely cause it to fail. No argument there.

The PENN by Johnson Controls is very popular and used by home brewers for converting freezers to kegerators or keezers, and have been for YEARS. They're about $60. Do freezer compressors fail? Sure. Often? No. Guaranteed to fail? No.

If your average ambient is over 100 degrees and you're running a freezer compressor to keep it 75 or 80, I just don't see a problem. Will it run more frequently that a freezer set for zero? Probly. Will it burn it out? I doubt it. Since you can buy a used freezer for under $200, who cares?

If you have mega-thousands wrapped up in lifepo4 cells that run a danger of being ruined for temperature, I would choose another method for climate control - put them in an air conditioned room. [shrug]

 

[Warpspeed]

In a sealed compressor unit, the entering refrigerant gas first passes through the motor windings for cooling purposes. If the ambient inside the freezer is already below freezing, the motor windings receive better initial cooling than if the freezer is starting off at room temperature.

A second factor working against you is the refrigerant pressure and mass is much greater starting off at room temperature. So you have the unhappy combination of the piston compressor demanding much higher torque, and at the same time the motor receiving less than its usual cooling.

Its not BS, its a common cause of failure for sealed compressor units.

Airconditioners are expected to start up and run in high ambient temperatures, and the design of the whole system is based on that.

Freezers are designed to normally run continuously below freezing (on the evaporator side) under normal working conditions.
The OCCASIONAL short overload is not too serious, but running it like that all the time may shorten its life.

Its like fitting a half horsepower motor to something that requires two horsepower to drive it.
It will probably run fine for a short time.

 

[Warpspeed]

Having said that, our "battery cooler" only needs to pull the temperature down by a relatively small amount.
And the insulation is excellent.
So our compressor only has to run for a very short time, and starts off stone cold every time.
It then can rest for a period long enough to cool right back down again.

So although we will definitely be overloading the motor, hopefully the motor temperature rise should not become excessive.
I expect it should work quite well, as long as you remember never to run the compressor continuously with the lid open for an extended period.

 

[acdoctor]

In a sealed compressor unit, the entering refrigerant gas first passes through the motor windings for cooling purposes. If the ambient inside the freezer is already below freezing, the motor windings receive better initial cooling than if the freezer is starting off at room temperature.

A second factor working against you is the refrigerant pressure and mass is much greater starting off at room temperature. So you have the unhappy combination of the piston compressor demanding much higher torque, and at the same time the motor receiving less than its usual cooling.

Its not BS, its a common cause of failure for sealed compressor units.

Airconditioners are expected to start up and run in high ambient temperatures, and the design of the whole system is based on that.

Freezers are designed to normally run continuously below freezing (on the evaporator side) under normal working conditions.
The OCCASIONAL short overload is not too serious, but running it like that all the time may shorten its life.

Its like fitting a half horsepower motor to something that requires two horsepower to drive it.
It will probably run fine for a short time.

Not to mention the differences in low temperature refrigerant versus medium temperature refrigerant. Compressor compression ratios are about the same and that is where the similarity ends.

 

[No Idea]

I have related experience for cooling a 900L outdoor aquarium with 1000L sump in Bangkok. I started out on the freezer path but found it all boils down to the insulation, compressor HP, and efficiency of heat transfer. Plenty of online forums about marine aquariums are further along the discussion than this forum.

My target water temp was 24C to 27C in air ambients >40C in hot season and it worked fine.

Mine was a highly insulated aquarium except for front and the cooler AC power source controlled by temp probe with wider set points than the chiller had.

I know water (and glycol mix in cold countries) is not ideal to bathe a large battery bank in and I recognise ground source cooling has been discussed a lot. However has anyone looked at an aluminium watertight case to sit the battery banks in a temp controlled fluid bath?

My chiller has been sitting unused for 3 years but I am hanging on to it for this future battery cooling purpose and on my list is learning to weld aluminium. I would have aluminium sheet spacers between the cells and all sides except top in contact with the aluminium.

Thinking you can avoid condensation issues by not having extremely low air temperatures from a freezer that needs to compensate for air being your cooling medium.

My chiller is overkill - they do much smaller ones.