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techntrek View Drop Down
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Posts: 9059 		Direct Link To This Post Topic: keeping hooked up to shore power
    Posted: 22 Sep 2015 at 9:10pm
Didn't get mine onto the Kill-A-Watt yet, even though I spent this evening getting it ready to replace my broken spring.  Fred's test definitely shows the conversion loss + converter's own use, actually it is a bit more than I expected it to be.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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WillThrill View Drop Down
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Posts: 298 		Direct Link To This Post Posted: 23 Sep 2015 at 12:53am
Originally posted by fwunder

I think what the numbers best demonstrate is that if you have well maintained and fully charged batteries, it is very reasonable to keep the pod plugged in 24/7. Someone here, smarter than me, may wish to do the math regarding the relative cost of running the fridge off propane or shore power. BTW, I did just have a new 1000 gallon propane tank filled - 850 gallons @ $1.29/gallon. Bet that would run the fridge for a while!!

fred

I haven't been able to find out exactly how much propane the refrigerator uses, but I can figure out a break-even point.

If the refrigerator consumes 14 watts after its cooled down, that's 336 watt hours per day.  At current electrical rates (~$.10), that's $.0336 per day, just over three pennies.  With propane at $1.29 a gallon, the refrigerator would need to run on one gallon of propane for a little over 38 days to equate to the same cost as shore power.

Given my experiences, a 20 lb. tank will last somewhere around 30 days, plus or minus a week.  That would cost $1.01 with electricity and about $25.80 with propane.

So even if the propane lasts twice as long as my estimate and the refrigerator consumes twice as much electricity as I'm calculating, it's still FAR more expensive to run the refrigerator on propane than shore power.
"Not all those who wander are lost." Tolkien

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fwunder View Drop Down
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Posts: 1676 		Direct Link To This Post Posted: 23 Sep 2015 at 11:17am
Just messing around and having a peek at the Kill-A-Watt every so often...

The fridge does seem to draw about 140 Watts AC when cooling (converter on also). I have it set at the midpoint for cooling, it's empty and inside temp is @ 30 degrees measured with analog fridge thermometer. Doesn't take much opening and closing to make it work and from my overnight measurements I think it's safe to say you will use 85-100 AC watt average running converter and fridge. Of course ambient temp and midnight fridge raids will effect usage. All in all the fridge does seems pretty efficient on AC at our current temps 75/50.

fred
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Posts: 9059 		Direct Link To This Post Posted: 23 Sep 2015 at 1:29pm
Not entirely related to this discussion, I once ran the numbers and found that we use about the same amount of energy per day when camping (mostly due to A/C) as we do at home. Didn't expect that.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Posts: 1676 		Direct Link To This Post Posted: 23 Sep 2015 at 3:18pm
Originally posted by techntrek

Not entirely related to this discussion, I once ran the numbers and found that we use about the same amount of energy per day when camping (mostly due to A/C) as we do at home. Didn't expect that.

It will probably go up a bit when you get indoor plumbing! LOL

fred
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Posts: 9059 		Direct Link To This Post Posted: 23 Sep 2015 at 8:50pm
Love the outhouse in winter.  At -5 F.  In the snow.  At night.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Posts: 1676 		Direct Link To This Post Posted: 23 Sep 2015 at 9:23pm
Page 363-368 Sears Catalog. Washing machine parts. I could spend hours. Still do. Wink

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Direct Link To This Post Posted: 24 Sep 2015 at 7:50am
Originally posted by WillThrill




 I'm not sure what the maximum charging amperage is of the converter, but my guess is it's either 10 or 15 amps.  That would be 120 to 180 watts plus what the converter itself uses, so I'm guessing the total draw would be around 200-300 watts.



[/QUOTE]

The charging amperage of the inverter is something that would interest me. I have not read anything that specifies. I do seem to remember that the inverter will only stay in bulk mode for 1 or 2 hours (don't remember), times out, and then switches to the next lower charge rate. I suppose this is to keep us all from boiling our batteries. When running the generator (in economy mode) I notice the rpms of the generator drop when the inverter switches out of bulk mode.

Sometimes, I use a lot of 12vdc power in a 24hr period - maybe for the furnace, maybe for radio transmitting, etc. I find, if I only run the generator until it switches out of bulk mode, I kind of "fall behind the curve" on the state of charge of the batteries. In other words, I am using it faster than I replace it.

So, does anyone have the inside scoop on the charge rate(s)?

I'm trying to determine the best (least) use of the generator:
Run once per day for a longer period or
Run 2 times per day - each time with it being in bulk mode. I've been playing with this.
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Posts: 298 		Direct Link To This Post Posted: 24 Sep 2015 at 1:50pm
Originally posted by David

The charging amperage of the inverter is something that would interest me. I have not read anything that specifies. I do seem to remember that the inverter will only stay in bulk mode for 1 or 2 hours (don't remember), times out, and then switches to the next lower charge rate. I suppose this is to keep us all from boiling our batteries. When running the generator (in economy mode) I notice the rpms of the generator drop when the inverter switches out of bulk mode.

Sometimes, I use a lot of 12vdc power in a 24hr period - maybe for the furnace, maybe for radio transmitting, etc. I find, if I only run the generator until it switches out of bulk mode, I kind of "fall behind the curve" on the state of charge of the batteries. In other words, I am using it faster than I replace it.

So, does anyone have the inside scoop on the charge rate(s)?

I'm trying to determine the best (least) use of the generator:
Run once per day for a longer period or
Run 2 times per day - each time with it being in bulk mode. I've been playing with this.

A quick note first: inverters and converters are different things.  We've been discussing converters, which take AC to DC.  Inverters take DC to AC and are all after-market.

The maximum amperage of the WFCO converter/charger (it's both and quite pricey) is a very good question, and I've not been able to find out the precise answer despite searching.  I was surprised to see several reports that it's anywhere from 45 to 55 amps, which is quite large for a 12 volt charger.

The WFCO model is a 3 stage charger.  In the process of monitoring the battery's voltage it determines that the battery's capacity is below about 70-80%, it does 'bulk' charging at the highest amperage rating it can.  Once the battery reaches around 70-80% capacity, it switches to 'absorption' charging and significantly fewer amps are sent to the battery, usually 5-8.  Once the battery reaches 93-97% capacity, it finally switches to a 'float' or 'trickle' charge that is usually 1-2 amps or even less.  This overall process is the 'healthiest' way to recharge lead acid batteries, though it can easily take 8-12 hours, depending on the size of the charger, the size of the battery, and the battery's capacity.  I apologize if you already know all of this, but I'm sure that some reading this will not.

However, this process does create some issues to be aware of when you're recharging the battery via a generator.  Mainly, it is a waste of fuel to run the generator to recharge the Pod's battery unless the battery's capacity is low enough for the charger to run in bulk charging mode.  Otherwise, you're producing a minimum of 20% of your generator's rated capacity in power (i.e. 2,000 watt generator can't produce less than about 400 watts) when your charger only needs a fraction of that to charge the battery; the excess power is wasted unless you're using it for something else.

The easiest way to determine this is to monitor the battery's voltage.  There are lots of posts on this site showing various ways of installing a permanent voltmeter for this purpose.  When the battery's voltage drops to around 12.2-12.3 volts, the battery is at about 50% capacity, and it is at this point that you should recharge the battery as letting it go below 50% does excessive, irreparable damage to it (keep in mind that any use of a lead acid battery reduces it's lifespan to some degree).  When the charger is bulk charging, the voltage will be around 14.4.  When it switches to absorption charging (70-80% battery capacity), the voltage drops to around 13.6.  At this point, you should stop running the generator.

So running the generator more often with the charger doing bulk charging each time is far better in terms of minimal overall cost than running it less often and the charger switching to absorption charging for a part of that time.  But once you're doing camping or when you can plug into shore power, you should bring the battery back to 100%.  A battery should never be stored at less than a full charge.
"Not all those who wander are lost." Tolkien

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Direct Link To This Post Posted: 24 Sep 2015 at 4:53pm
Please excuse my slip of the tongue/keyboard - converter 120vac to 12vdc, inverter 12vdc to 120vac.

Thanks for all that you wrote. It is good information. What you wrote leads me to believe my suspicions. I have a feeling the generator is "telling" me the answer. When the converter goes out of bulk mode, the generator returns to idle. It does not "see" enough of a load to do much else. The converter/charger can't be doing a whole lot of work.

Like you, I really doubt that the converter charges at 100% of it's rated output (or even very close). My "wild eyed" guesstimate would be 10 amps. It would be good to know this info.

My situation is rare/unique in that I operate Ham radio portable, often. Next year (2016) is Indiana's bicentennial and I anticipate being portable more than usual, for special events. Sometimes there will be commercial ac power, sometimes not. My transceiver typically requires 15 amps (+ or -) when transmitting. During events, contests, etc., it takes a lot out of the batteries, due to the high duty cycle.
So, I'm thinking it will behoove me to figure out how to cram the most into the batteries in the shortest time possible, when no commercial ac is available. Out of consideration of those around me, I do not want to run the generator all the time.

I have run into times when the days are cold and the furnace (12vdc power hog) really challenged keeping the batteries up. Maybe others have too so, it might be good to know.

Right now it is sounding as if my multiple bulk mode charges in a day may be the best option.

Again, thanks for your thoughtful reply/post.
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