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Experimental results powering a freezer with batteries

This is a discussion on Experimental results powering a freezer with batteries within the Alternative Energy (Wind, Solar, Hydro etc) forums, part of the Off-Grid Lifestyle category; yah know there is a simpler way called a RV fridge runs on 12 volts--you know the kind found in RV's and campers. sooooooooo check ...

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Thread: Experimental results powering a freezer with batteries

  1. #21
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    yah know there is a simpler way called a RV fridge runs on 12 volts--you know the kind found in RV's and campers.
    sooooooooo check it out a solar charger and a deep cycle truck battery will run the rv fridge cool huh?
    BTW there are several Items that those RV's have like the propane stoves and such and I even found one with a old fashion coal heater in it one time thought it was kind of cool.
    sideKahr likes this.
    nothing to see here, move along.

  2. #22
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    Quote Originally Posted by Medic33 View Post
    yah know there is a simpler way called a RV fridge runs on 12 volts--you know the kind found in RV's and campers.
    sooooooooo check it out a solar charger and a deep cycle truck battery will run the rv fridge cool huh?
    I would love to have a 12 volt freezer. There's one called the "Sundanzer" in the Backwoods Solar catalog that is equivalent in interior capacity to the 120 VAC unit I'm testing: the R-F165 built by ElectroLux. What I find interesting is that the two units consume almost the same amount of energy: 441 watt hours/day per catalog vs my Kill-A-Watt measured 470 watt hours/day for the 120 volt job.

    The R-F165 is more than five times the price of my Kenmore.
    Last edited by sideKahr; 04-19-2017 at 06:08 AM.
    Respect everything, fear nothing.

  3. #23
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    Quote Originally Posted by sideKahr View Post
    I really don't understand how batteries work. I kept track of how much energy was used by the freezer during the test with the Kill-A-Watt meter; it was 970 watt hours. That's fairly close to the theoretical energy available at 50% depth of discharge (800 watt hours for these batteries) using 85% inverter efficiency.

    The batteries just finished charging, estimated by when the smart charger switched to float voltage. The charge required 1740 watt hours. Thats a big difference. What's causing that? I've read that batteries have an internal resistance, but I don't understand why. Could that be the reason they need double the energy to get back to where they were?
    Several factors here so start by telling me how you are converting the generators 120v AC to 15v DC charging current. Probably a LOT of inefficiency there. Is the meter reading the charging volt/amps on the generator or is it on the 12v wire feeding the battery?

    Generally LA and AGM batteries are about 90% efficient at storing the energy they are fed. They are most efficient at absorbing the charge when they are less than around 85% charged and become very inefficient at accepting the current as the get close to full charge. Above about 90% charge they can loose up to half the energy put into them from outgassing of the electrolyte and heat.
    Last edited by John Galt; 04-19-2017 at 12:09 PM.
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  5. #24
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    Quote Originally Posted by John Galt View Post

    Several factors here so start by telling me how you are converting the generators 120v AC to 15v DC charging current?

    Is the meter reading the charging volt/amps on the generator or is it on the 12v wire feeding the battery?
    1. The batteries are charging with an Iota 30 amp converter/smart charger powered by 110 VAC house current.

    2. I'm using a "Kill-A-Watt" meter to monitor the total power input to the charger. The batteries are charged with 4 AWG cable, tinned rings, 3 feet each, and the voltage drop is 0.01 V from the charger terminal to the battery terminal on the positive lead.

    I've been checking the batteries during charging, and they're just barely warm. I can hear the electrolyte bubbling slightly when the charger is in the absorbtion stage (14.6 V), but if the overpressure valves have outgassed, there is no evidence of it. They're supposed to be fully recombinant.

    The charging process seems inefficient, but I've got little experience. Maybe it's normal.
    Respect everything, fear nothing.

  6. #25
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    don't you run sail boats or something sidecar?
    don't those some of those have a fridge or just an icebox?
    you can find used rv stuff in classifieds like craigs list or possibly ebay.
    nothing to see here, move along.

  7. #26
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    Quote Originally Posted by Medic33 View Post
    don't you run sail boats or something sidecar?
    No, that's stowlin who sails up and down the west coast. I'm a landlocked prepper in Pennsylvania.

    I don't actually NEED refrigeration, it was just a test of the battery bank before I get some solar panels up this summer. It's interesting stuff.
    Last edited by sideKahr; 04-19-2017 at 03:38 PM.
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  8. #27
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    The spec sheet for your charger shows 80% efficiency so that's some of your loss, and you know how they like to polish the numbers on spec sheets. http://www.iotaengineering.com/pplib/dls30spec.pdf

    So replacing 970 watt hrs of energy using that charger means the charger needs 1164 watts of 120v AC put into it assuming the charger is 80% efficient. Now lets assume you're really topping those batteries to 100% SOC and they are 80% efficient (average as they charge) at accepting the charge. Now you're up to 1396 watt/hrs of 120v Ac current to fully charge the batteries.

    If you had flooded LA batteries instead of AGMs I'd be interested in checking the SG (specific gravity of the electrolyte) to see if the batteries are really 50% drained or perhaps a bit more deeply drained. When you run an electric motor (like the compressor) the power factor (rippling in the current draw as the armature spins) can be hard for a meter to correctly measure. In an effort to check this set the meter to display in volt amps instead of watts. Volt Amps are a more accurate measure of energy used since it negated most of the effects of the power factor.

    We are nearing the limit of my knowledge, I really don't understand the difference between volt amps and watts but electricians tell me there can be a huge difference when running electric motors. @sideKahr
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  9. #28
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    Thanks for your help, @John Galt . I'm beginning to understand that there are a lot of inefficiencies I hadn't considered. And I've seen the power factor and volt amps setting on the meter, but I haven't puzzled out what those are yet.

    Charging the batteries with solar power is going to be a lot of fun. Ad astra per aspera!
    Respect everything, fear nothing.

  10. #29
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    Quote Originally Posted by sideKahr View Post
    No, that's stowlin who sails up and down the west coast. I'm a landlocked prepper in Pennsylvania.
    **Kauboy looks at sideKahr's avatar picture**
    **Kauboy rereads sideKahr's quote above**
    **Another glance at the picture**

    **scratches head, furrows brow, navel gazes, looks back up, and sighs**
    Semper paratus!

  11. #30
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    Quote Originally Posted by Kauboy View Post
    **Kauboy looks at sideKahr's avatar picture**
    Oh my, a deceptive avatar, go figure, I thought that all avatars were checked by the Administrators ensure they reflected the true character of the character posting here...

    Rancher

 

 
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