Chassis vs House (Coach) solar charging

[Oregon Coyote]

I spun this discussion off from the current [no pun intended] discussion about "electrical problems" because we seem to be straying into the world of solar charging.

I am a bit concerned about Audrey's thinking that her coach needs a 50W solar panel just to maintain the chassis batteries (2). [I don't have an Alpine electrical schematic-- so please jump in here if I am incorrect.]

Assuming the engine's alternator has been working properly and the chassis batteries are fully charged when the engine is shut down, the key is NOT in the accessory position, and all exterior coach lighting (headlights, tail lights, marker lights, etc.) have been turned off, there should be very little continuing draw on the chassis batteries. A coach clock or anti-theft device is about the only things I can think of. Unless the coach is going to be idle for months or it is really cold-- no supplemental charging is even needed.

Otherwise, the 10W solar panel is more than adequate, even on cloudy days, to maintain the charge in the chassis batteries. An unregulated 50K solar panel is not only unnecessary- but will tend to overcharge the chassis batteries thus causing premature failure.

If one does not have the 10K solar panel, an easily available and inexpensive portable solar panel that plugs into the cigarette lighter (assuming you have one) will be more than adequate. The house/coach batteries are an entirely different problem because Audrey is probably afraid to sleep in the dark.

Norm

[Oregon Coyote]

I spun this discussion off from the current [no pun intended] discussion about "electrical problems" because we seem to be straying into the world of solar charging.

I am a bit concerned about Audrey's thinking that her coach needs a 50W solar panel just to maintain the chassis batteries (2). [I don't have an Alpine electrical schematic-- so please jump in here if I am incorrect.]

Assuming the engine's alternator has been working properly and the chassis batteries are fully charged when the engine is shut down, the key is NOT in the accessory position, and all exterior coach lighting (headlights, tail lights, marker lights, etc.) have been turned off, there should be very little continuing draw on the chassis batteries. A coach clock or anti-theft device is about the only things I can think of. Unless the coach is going to be idle for months or it is really cold-- no supplemental charging is even needed.

Otherwise, the 10W solar panel is more than adequate, even on cloudy days, to maintain the charge in the chassis batteries. An unregulated 50K solar panel is not only unnecessary- but will tend to overcharge the chassis batteries thus causing premature failure.

If one does not have the 10K solar panel, an easily available and inexpensive portable solar panel that plugs into the cigarette lighter (assuming you have one) will be more than adequate. The house/coach batteries are an entirely different problem because Audrey is probably afraid to sleep in the dark.

Norm

[AlpineH&H]

Yes you are correct, the key is having good batteries. If your batteries are 24 - 30 months old they probably need replacing. Your 10 watt charger will keep them charged and ready for your next trip.

Make sure your check fluid levels is not self contained, most starting battery are self contained though.

[Jim&MaryJo]

I've wondered too. Seems we need to know what is the "parasitic" load on the coach batteries.

I recall EgrMike took ammeter readings and posted such load. If so, knowing such load would help determine how much solar charging is needed to stay ahead of it.

I suspect the pararsitic load includes:
-dash radio (memory & clock)
-lp co sensors
-maybe some ecu dormant load

The solar controller WRV installed appears to prevents battery over-charge.

[Audrey & John]

I calculate that our chassis batteries would use a float charge of 2.7A

A typical 50W panel generates about 3A at maximum power.

I measure a parasitic drain on the chassis batteries of about 0.5A using a clamp-on DC ammeter.

Given a calculated float charge of 2.7A, the conditions needed for a typical 50W panel to produce 3A, and our parasitic drain of 0.5A, I decided a 50W panel would not overcharge the chassis batteries even without a controller (which we would install anyway).

John

Here is how I calculated the float charge for our Interstate Workaholic CCA 660 chassis batteries:

Each battery is rated RC = 160 minutes @ 25A
I could not find the AH rating for our chassis batteries so I estimated the AH from the RC rating with this calculation (the batteries likely have a higher AH rating than what I calculate which puts the float charge calculation on the conservative side):
2 batteries * 25A * (160 minutes / 60 minutes per hour) = 133AH

Float charge for wet cells (according to our Xantrex RS200 manual) is 2% of the amp-hours rating.
The float charge = 2% * 133.33AH = 2.67A

PS. Audrey claims that I occasionally make a mistake so please post any corrections.

[Oregon Coyote]

[Signing this "John" is not going to fool anyone, Audrey. Everyone on this forum knows you Alpine alone with a man-size blow-up possum you call John. But, hey, I will play along ]

"John": I yield to your calculations because even though I worked for Exide battery 42 years ago, I have discovered that my brain is porous and that far more knowledge leaks out than seeps in. All I remember is that the larger post is pos.. or is it neg...?? and the red wire is ??????? hmmm, or is the other way around??? [Ever notice in the movies that the bomb squad guy always ponders whether to cut the red or the green wire? Don't those bombmakers ever use other colors just to fool the bomb squad?]

Anyway, .5 amps is about twenty times the typical parasitic load on passenger cars. So you well may be correct that a trickle-charger is insufficient in an Alpine to cover the float requirement plus the parasitic. How you would adjust a 50W solar regulator specifically for the Interstate batteries might be something else to ponder but that is for another discussion.

Norm

[Ted III]

There are a lot more little parasitic guys pulling off the batteries. The Allison transmission pulls off it and everything in it that is electronic. It does create a fairly substantial load

[Buddy and Beverly]

When we attended a seminar at the FMCA Convention in Charlotte, we were told that there was enough pull on chassis batteries for them to go dead in about a week.

Beverly

[SteveS]

I replaced my chassis batteries about a year ago and while I had everything disconnected I measured the static current draw with an in-line ammeter (I don't have a DC clamp-on). It measured about 250 ma. Since my coach is older than John's (or is that Audrey's) I wouldn't be at all surprised if 400 - 500 ma are being drained from all the new-fangled items the coaches come with nowadays.

Speaking of who's coach it is, When God established marriage He said that they shall leave their father and mother and the two shall become one...the problems started then when they couldn't decide which one.

[Audrey & John]

Oh you silly people!

Here we BOTH are (John's the one in the back in case you needed help figuring out which one of us is which) enjoying our new (well 1 month old) coach in May of 2005.
It's OUR coach - both names are on the title.

Believe you me - consider it a minor miracle that John has not only posted once, but twice on the forum this month. Don't discourage him! The guy's a fountain of wisdom (and I love it when he posts things himself instead of telling me what to say).

Audrey

[Buddy and Beverly]

Audrey and John,

Thanks for putting faces to names.

Well, I know we have the same yr, length, floor plan, and exterior and interior colors, but do we even have the same rug on the floor? It certainly looks similar, if not the same--I bought mine at TJ Maxx, and it goes beautifully with the Meadowlands colors. Oh, we have a recliner and not the Euro chair, so there is one thing different.

Beverly

[Audrey & John]

We bought our runner at Linen's and Things. I think it's the Verona Sage Green rug by Marcella - 26" by 83". Kind of matches the interior colors although it's a bit darker.

Audrey

[Jim&MaryJo]

Thank you John, that was very helpful!