Hi Mega Brain,
I'm hitting the woods in a few weeks and I want to bring my wee freezer. Its a lil danby I got second hand for 60$ a few years ago when I started buying meat farm direct. I keep it in my back shed, winter and summer. Screw the fridge, but I can't live without a freezer...especially since I will be in quarantine for 2 weeks after arriving at said woods. Won't be popping out to the farmers market on the weekend...gotta come prepared.
We will have a generator for tools (...mostly skillsaw, grinder, heavy duty drill...this is a building trip) but I hate the idea of running it constantly.
I have a blue top 55Ah 12v battery from work..it was bought for a project, didn't get used, wasn't being maintained so I went on mission and took it to maintain (and use) until we need it at work again. Its been on a trickle charger the past 8 months and occasionally used with a cheap small inverter to run my internet stuff when the powers been out.
My idea was to upgrade the inverter, which I just did with another cheapish 1500w (3000w peak) modified sine wave inverter (just a motomaster...was on sale) and charge the battery off the generator whenever we're using tools using the same lil charger.
I've been testing it with the freezer the past couple days...here is what i've found.
-the inverter shuts down when the battery voltage drops below 12v, so no worry about over discharging.
-the inverter draw an unspecified amount somewhere under 2amps which is a lot of loss ! That's from the documentation which does not specify at what voltage that current is drawn and I can't easily measure it right now my contactless meter is at work, where covid prohibits me to go !
-the readout on the inverter reads 80watts when the freezer is actually running.
-I can run the freezer, with it doing its thing for about 6 hours on a full battery before the battery drop to just under 12v under the load
-It takes at least 7 hours on the wee charger to pump the battery back up to full.
At this rate, I will have to run the generator more than more than 1/2 of the time and won't be able to get through a full night without it IF i want this freezer to be a freezer.
Then I thought...
What if the inverter and freezer are ONLY on during when the freezer pump has to kick in? I estimate the duty cycle of the freezer to something like 10% actually running, 90% just chilling (
) ... The inverter came with a contact closure remote on/off switch on a phone cord. I was thinking I could wire a phone cord to a passive thermostat, inside the freezer somehow...but in reverse...so that everytime it goes OVER x degrees the thing would turn on as opposed to off (I assume the switch is a closed = ON open = OFF...need to look closer)
I'm betting that given the mad waste of the inverter itself, as well as whatever is consumed by the freezer in standby (not pumping) i could likely save a lot of energy this way, and gains would total least 30% of the battery charge which would get me through 8 ish hours, or a full night sans generator. I would hope that I can actually take it to 200% for 12 hours, and not have to run the battery down that low ever.
I'm also thinking that I could up the ante on the insulation. I could add 2" of foamboard inside...it would reduce capacity but there would definitely be gains in terms of performance.
What if i take that a step further and throw a bunch of hay bales around and on top the thing ? I know that these things should produce heat when they do their thing, but this one never seems to be warm on the outside.
If a combo of these ideas doesn't give me a 200% improvement in efficiency my next best option is probably to just buy a better battery but as per the title of the thread, quick n dirty's the game here, so that would not ne ideal right now. I also realize a few hundred watts of panels would go a long way to keeping the battery topped off as well, but that's more expense not just for panels, but charge controller etc. Maybe money is better spent on some kind of quicker charger for the battery, though it seems debatable whether a quicker charge is good for a lead acid battery (10A for instance - they exist though, and compared to another battery, they're pretty affordable).
any thoughts on this ?
anybody every do the thermostat in the freezer move before ?