12v solar and chest freezer to fridge conversion - what went wrong?

[sensij]

That's the question I was hoping to have answered.

AzRoute66 asked some questions that were intended to help. "Charging too fast" is a symptom of a sulfated battery. Maybe your "new" battery sat in a warehouse for 6 months before you bought it, I don't know. MCA testing isn't going to translate to Ah capacity very well, but everything else you've said is consistent with a bad battery.

Putting AGM batteries in parallel is asking for trouble... if you want to recreate your setup, try measuring the current discharging from each of the batteries while the fridge is cycling, and see how balanced they are.

[J.P.M.]

this thread reminds me more and more of the well known joke: http://www.design.caltech.edu/erik/Misc/balloon.html

Not bad. I need stuff like that when I take myself too seriously.

[max2k]

Jeez man. Read my original post again. Then read your replies. You missed so much I can't believe you'd talk about attention to details. Case in point - it was a /temporary system/. I was looking for information to satiate my curiosity, not shortcuts.

I'm sure you have a lot of useful knowledge, but if you don't take the time to understand the system as it's been described and the question as it's been asked, you're just wasting your time any everyone else's. What value can you have here if you're not paying attention to those things?

this thread reminds me more and more of the well known joke: http://www.design.caltech.edu/erik/Misc/balloon.html

[paulgareau]

To be fair, it sounded (to me at least) like he was buying ice to keep his food cold.

Yes - I thought it was obvious too. I was using ice and a cooler. Got tired of buying ice so converted a chest freezer to a fridge. Thanks!

[paulgareau]

you don't believe in miracles that OP realizes his ignorance and amount of details involved in reliable design and comes around? I don't- I bet he's now searching Net up and down for quick-n-dirty shortcut. Trouble is there's none and with just little patience and attention to details he could accomplish what he is after. Oh well.

Jeez man. Read my original post again. Then read your replies. You missed so much I can't believe you'd talk about attention to details. Case in point - it was a /temporary system/. I was looking for information to satiate my curiosity, not shortcuts.

I'm sure you have a lot of useful knowledge, but if you don't take the time to understand the system as it's been described and the question as it's been asked, you're just wasting your time any everyone else's. What value can you have here if you're not paying attention to those things?

[paulgareau]

Really light on the panels. Why does everyone go cheap on panels? They cost far less than batteries. I've been using a chest fridge for years ( five months at a time), first with a 5CF and then with a 7CF when that outgassed. I use only a single car battery and a little more than a KW of panels. Fridge only operates during the day and will only start when battery is at least 13.7V. Cold is stored in mass liquids and electronically controlled to 33F. A mechanical thermostat is asking for disaster.

I'm glad that's working for you, but I doubt many people would call that a well designed system. You're pushing a huge amount of amps into that battery. Also, it doesn't help if you want to run a fridge 24x7, which was my goal. Also, I said my batteries were floating by noon, so I'd say the panel was adequate. The thing that surprised me was that a battery bank that was 300ah shouldnt be able to charge from <50% to 100% in such a short amount of time with the size panel I was using. That's the question I was hoping to have answered.

[J.P.M.]

To be fair, it sounded (to me at least) like he was buying ice to keep his food cold.

Maybe, but it sounded to me that the duty was about making ice in a recycled or some such freezer, and then using the ice to keep food (or more importantly beer ???) cold.

Either, or any way, it takes as much energy to melt ice as it does to make ice. Just reverse the direction of the heat flow.

As for keeping any box and its contents cold, at any given (steady) temp. diff., ambient to cold box, once cooled down, the heat loss/gain will most entirely only be f(cold box heat loss rate), with some additional consideration for cooling added warm contents, opening/closing door(s) or, indeed, making ice or freezing things in a possible freezer section. That is the cooling duty that the application needs to be designed to meet.

Startup transients in compression equipment are an important issue, but confined mostly to the battery/PV system design particulars and are in addition to and different from considerations of making and keeping stuff cold to prevent spoilage.

[jflorey2]

Sorry man, but I told you what batteries I was using. I also said I got them because I needed a quick and dirty system. You're still not answering the question. And are you saying it's OK to buy junk after I've done math?

In some cases, yes. If you have an application where you need short-duration high power discharges (i.e. periodic opening of a garage door or something) with no steady loads then "junk" (in this case a starter battery) might just work. How do you know if you can use a battery like this instead of a better deep cycle battery? You do the math; figure out the loads, how many watts and watt-hours you are going to need and go from there.

[sdold]

To be fair, it sounded (to me at least) like he was buying ice to keep his food cold.

[Logan5]

Cognitive dissonance

[J.P.M.]

you don't believe in miracles that OP realizes his ignorance and amount of details involved in reliable design and comes around? I don't- I bet he's now searching Net up and down for quick-n-dirty shortcut. Trouble is there's none and with just little patience and attention to details he could accomplish what he is after. Oh well.

NOMB. Besides, some folks you just can't reach. All the best to the OP and A.M.F.

[max2k]

I thought I read in your 1st post that you got tired of buying ice ?

In any case, the way I learned it, it's perhaps a good idea to identify the loads and the duty before designing a system to meet those loads and duties.

You obviously have that all well in hand

If you consider such information as I provided as having nothing to do with your situation, forget I wrote anything. Sorry to have bothered you.

you don't believe in miracles that OP realizes his ignorance and amount of details involved in reliable design and comes around? I don't- I bet he's now searching Net up and down for quick-n-dirty shortcut. Trouble is there's none and with just little patience and attention to details he could accomplish what he is after. Oh well.

[J.P.M.]

OK, I'm fairly new here so maybe I didn't ask my question the right way. BUT. This is about a chest freezer to refrigerator conversion using a johnson controls thermostat (see orig question and follow ups). I'm not making ice. This is probably good info for someone but has nothing to do with my situation or question.

Also have provided the startup and running wattage....

I thought I read in your 1st post that you got tired of buying ice ?

In any case, the way I learned it, it's perhaps a good idea to identify the loads and the duty before designing a system to meet those loads and duties.

You obviously have that all well in hand

If you consider such information as I provided as having nothing to do with your situation, forget I wrote anything. Sorry to have bothered you.

[AzRoute66]

Really, brand new from the store? And the other batteries that had been working successfully? I'm done with the project now, it was for 6 weeks as I've said a few times.

I don't know when you bought them, I only know you've been charging them with a 250W panel. You said, "...so I used Walmart 24DC marine, deep cycle batteries." Tell us more about which batteries, when you got them, how you wired them, what changed when you put them in, and what changed from then to now... I'm pretty much on board with max2k in post #15. Those "other batteries that had been working successfully", weren't them the ones floating by noon?

[PNPmacnab]

Really light on the panels. Why does everyone go cheap on panels? They cost far less than batteries. I've been using a chest fridge for years ( five months at a time), first with a 5CF and then with a 7CF when that outgassed. I use only a single car battery and a little more than a KW of panels. Fridge only operates during the day and will only start when battery is at least 13.7V. Cold is stored in mass liquids and electronically controlled to 33F. A mechanical thermostat is asking for disaster.