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Old 06-10-2005, 10:49 AM   #1
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Harbor Freight has a sale on 45W solar array

The online store link is:

http://www.harborfreight.com/cpi/cta...emnumber=90599

My question is, has anyone used this specific model before? Any comment, cautionary oe otherwise would be welcome. Is this a good deal compared to the other internet suppliers?

I know from my reading to be realistic about the total amp-hr yield to expect from any solar array despite the rating.
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Old 06-10-2005, 02:30 PM   #2
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A key item on this one is the peak voltage of "23.57" volts. This means it is into the solar power category and not the solar charger category (which maxes out at about 15 v). In other words, the panel would need a good charge controller to be truly useful. Cheap controllers for a panel this size can be had for under $50 but a good one is likely to be a bit over $100.

As for price comparison with https://secure.westhost.com/secure/r...rform.htm#Kits as a reference, 45 watts for $200 is $4.44/watt versus $5.7/watt for an equiv size or $4.81/watt for a double that size. From this, it appears that the sale item is a fairly good value as far as solar energy is concerned. Sounds typical Harbor Freight.

45 watts will do to keep a battery charged during storage - if you have a good controller that knows about float and equalization. If might also work for very light use such as summertime needs for occasional lighting.

The rule of thumb for most RV purposes is that you need a minimum of a watt of solar power for each amp hour of battery you have and you need enough amp hour batteries to meet your needs for a typical weekend camp outing. For trailerists, this usually means 200 AH of batteries and 200 watts of solar panels.
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Old 06-10-2005, 08:19 PM   #3
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Thanks Bryan. So with 4 27D I'll need a semi full for panels.
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Old 06-13-2005, 03:48 PM   #4
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A friend recommended this one to me to charge up the battery or keep the charge steady.

http://www.harborfreight.com/cpi/cta...emnumber=41144

It is pretty inexpensive, but will it be usefull and do the job?
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Old 06-13-2005, 04:12 PM   #5
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5 watts - that's less than half an amp - and only with good sunshine. Seems to me it would be an awfully weak trickle charger.

I somebody suggest smoozing a VW dealer - he said they include such a trickle charger with some of the new cars but a lot of folks don't want them. So the dealers are supposed to be floating in them just waiting for some smooth talking RV nut to talk them out of one or two. Sounds kinda' doubtful to me but might be worth checking if you have a VW dealer handy.

If you are looking at something to maintain your wet cell batteries during storage, the best bet is going to be something that knows about equalization like Battery Minder or Battery Tender or the IntelliPower Charge Wizard and can supply at least a few amps. More expensive up front but you'll get better battery health and life to make up for it over time.
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Old 06-13-2005, 06:42 PM   #6
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Is there a way to tell how many watts a solar panel puts out? I just got one from my father in law and it measure 42 volts with my voltmeter, but thats all I know about it.

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Old 06-13-2005, 07:21 PM   #7
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How big is it? You get about 100 watts for every square yard of panel.

42 volts seems kind of high. That implies 84 cells in the panel. The ones for RV's are usually 36 cell panels or 18v. This high a voltage means you should get an MPPT type controller that can handle a high voltage input.

To actually measure power, use a sample load like an extension cord. 10 guage wire is a milliohm per foot so a 50' heavy duty cord would provide a 0.1 ohm load going down and back (short two conductors on one end to make a loop). Measure the current the panel can supply through that to get an idea of what power (current squared times resistance) the panel can supply. If I remember right, 12g wire has twice the resistance and might be easier to come by.
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Old 06-13-2005, 09:36 PM   #8
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It measures 16x13 - it has 36 1/2 round thingies on it - if thats what cells are - you can see I really know alot about this..... I really did measure 42 volts, but that was with no load. I have to re-try with the extension cord.....

So since it has 36 cells, do I still need a controller? And... is it worth using?

Thanks for you help

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Old 06-13-2005, 11:06 PM   #9
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I would also have to asked the question, how are they constructed?
Will they survive a road trip on the back of an Airstream.
Most solar cells are constructed for stationary use, not bouncing down the road.
Beware, the cell connections are sometime pretty rigid and will not take much bending, they need a stiff mount in order to last.
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Old 07-11-2005, 06:49 PM   #10
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Leipper, I have 1.619 ohms /thousand feet for 12 gages versus 1.018 ohms for 10 gages.
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Old 07-11-2005, 09:20 PM   #11
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If it is the red solar charger from HF I bought 2 and threw both of them away after they let my battery drain under no load and no sun for several days. I don't think they had a diode to stop the battery from discharging thru the panel or a high leakage diode

The ones I bought had a sale price of around $10. The link on your post goes to HF but I guess the SC is no longer on sale since it said item not aval.

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