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Inge View Drop Down
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Joined: 30 Jul 2014
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Posts: 34 		Direct Link To This Post Topic: Charge duration plugged in vs solar
    Posted: 01 Aug 2014 at 8:14pm
Our r-pod service guy told us that charging the batteries from completely empty to full would take 3-4 days when it's plugged in. I've read that the duration for a 100 w solar panel would be around 6-7 hours. How is this possible? Which one is right?


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Posts: 6128 		Direct Link To This Post Posted: 01 Aug 2014 at 9:30pm
What batteries do you have?

Ohm's Law will give you the answer, but it's simply aH's out, aH's in. Your on board charger can do around 10aH's, a 100w solar panel will do about 3.0 - 3.4 aH's PEAK.
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Posts: 9059 		Direct Link To This Post Posted: 01 Aug 2014 at 9:41pm
Your average deep cycle battery is 100-110 amps.  Since you shouldn't discharge it by more than 50% most of the time so "dead" would need about 55 amps to recharge (plus charging losses).  The converter will recharge it with an overnight charge.  Over a full, good, day a 100 watt PV panel will give you about 18 amps total.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Posts: 34 		Direct Link To This Post Posted: 02 Aug 2014 at 1:22am
The control in our pod said batteries are empty, and the service guys said it will take 3-4 days to charge them. If we shouldn't discharge them by more than 50%, how come we received an r-pod with absolutely empty batteries?
He mentioned the batteries are ok and the converter converts, but the power coming from the TV wouldn't be enough to load them completely.


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Posts: 438 		Direct Link To This Post Posted: 02 Aug 2014 at 5:18am
It is a little difficult to define "full charge".   The WFCO converter used in the rpods will only do bulk mode for 4 hours maximum then it switches to absorption mode for 40 hours more, then it finally goes into float mode.
That may have been what the dealer was referring to.

Bottom line though- yes a 2-3 hour charge mostly charges one battery.


Inge- If you received your rpod with a truly DEAD battery I'd be going back wanting a new battery.  Even one discharge to dead takes a lot of life off a battery.

If it went dead after you got it from sitting, well....  If a RV is going to sit then it either needs to be plugged in or the battery disconnected.     Wouldn't surprise me though if they didn't tell you thisOuch
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Posts: 9059 		Direct Link To This Post Posted: 02 Aug 2014 at 11:50am
The water/waste/battery monitor is largely useless.  The fresh water indicator, and possibly the gray water indicator, usually work ok.  The black water indicator is usually inaccurate in less than a year.

Figuring our your battery's state of charge (SOC) can only be determined by using an accurate voltmeter, or measuring the electrolyte, after letting it rest for at least 3 hours.  Or, by using an expensive battery monitoring system like the Trimetric.  The system in the pod is an inaccurate voltmeter and usually the battery isn't at rest, which is why it is useless.  On a recent trip, with a brand new battery and full charge, it said my battery was at 1/3 (2 lights) when I knew it wasn't.

As Budward said, the battery must be disconnected from the pod between trips.  Otherwise the LPG detector, and possibly other loads, will destroy the battery within a week or two by discharging it too deeply.  Reconnect it at least once a month, and before and after each trip, and then plug the pod in overnight.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Posts: 298 		Direct Link To This Post Posted: 02 Aug 2014 at 11:56am
Originally posted by techntrek

Over a full, good, day a 100 watt PV panel will give you about 18 amps total.


That's part of the reason I got a 100 watt solar panel. In good sun, it outputs about 6-7 amps, so on a summer day, I can produce at least 40 amp hours, maybe even 50.
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Posts: 1797 		Direct Link To This Post Posted: 02 Aug 2014 at 12:22pm
Originally posted by WillThrill

Originally posted by techntrek

Over a full, good, day a 100 watt PV panel will give you about 18 amps total.


That's part of the reason I got a 100 watt solar panel. In good sun, it outputs about 6-7 amps, so on a summer day, I can produce at least 40 amp hours, maybe even 50.


These two numbers are far enough apart to arouse curiosity. How much measured data do each of you have? Doug, are you basing on much older panels? What kind of controllers are being used, PWM or MPPT? I don't have solar but I've always used a rough 6 amp peak current, degraded to 70% at +/- 3 hours from peak if not tracking, from a 100W panel and a 6 hour useful day. Should yield 30+ AH per day.
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Posts: 9059 		Direct Link To This Post Posted: 02 Aug 2014 at 7:47pm
100 watts / 12 volts = 8.33 amps

8.33 amps * 4.5 average solar insolation =  37.5 amps (Google "solar insolation map" to find your area, then round up by .5 to 1 since it will be higher in summer when you are camping; 4.5 is the number for my area, not rounded up)

37.5 amps / 2 = 18.75 amps available from the battery on a perfect day

That last reduction by half takes into account battery charging losses, wiring losses, charge controller losses, etc.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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