solar panel amps

Submitted: Sunday, May 28, 2006 at 14:56
ThreadID: 34341 Views:2009 Replies:7 FollowUps:5
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Afternoon to everyone,

Just a quick question regarding specs on solar panels. For example the voltage at load is 16.5 and 4.8 amos for a 64watt panel. If you were to then put a voltage regulator between panel and battery, say 14.1 volts regulated, would the may amps also be lower as you are droping the voltage.

I was told a few days ago that the may amps is at 12 volt but that seemed strange to me, or is it normal for the 4.8 amps as stated to be at 12 volt which would mean I would bet the full benifit of the panel.

Cheers

Chris
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Reply By: rooster1070 - Sunday, May 28, 2006 at 14:57

Sunday, May 28, 2006 at 14:57
Sorry about the spelling, big night last night.
AnswerID: 175186

Reply By: Alloy c/t - Sunday, May 28, 2006 at 15:10

Sunday, May 28, 2006 at 15:10
Your maths is "out" enough to cause problems ,, 64w divided by 16.5v = 3.87 amps....your regulator would /should have provision to change from wet cell battery to gel /agm/ batteries as different voltages are required ,,
AnswerID: 175188

Reply By: Bonz (Vic) - Sunday, May 28, 2006 at 15:15

Sunday, May 28, 2006 at 15:15
Umm the may amps are higher than the april amps but not as good as the june amps. At any rate the amps as quoted are at a rated nominal amount os 13.33 volts i.e. 64w/4.8a=13.33volts or so Ohm said in Septmeber 1836 (they would be Sept amps)

You couldnt get 4.8amps at 16.5volt from a 64watt panel regardless of month (although I am still not sure about March, I never trusted March)

As top a regulated voltage I would assume that the regulator would reduce both voltage and amps as it would consume a small amount to work itself. How mux I am not prepared to venture.
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AnswerID: 175189

Follow Up By: Member - Blue (VIC) - Sunday, May 28, 2006 at 15:43

Sunday, May 28, 2006 at 15:43
You leave March alone Bonz... I'm a March baby! BTW, Ohm said it in September but he measured it in MARCH...
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Reply By: rooster1070 - Sunday, May 28, 2006 at 15:29

Sunday, May 28, 2006 at 15:29
Thanks for the help, if i was to get 64 watt in a perfect situation and the power was regulated to 14.1 volts, would the following equation apply.

64/14.1=4.5amps, or am I getting totally confused, the unisolar panel specs state that it short circuits at 4.8 amps

cheers
AnswerID: 175192

Follow Up By: Bonz (Vic) - Sunday, May 28, 2006 at 15:52

Sunday, May 28, 2006 at 15:52
nope youre spot on, never mind the month
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Follow Up By: Alloy c/t - Sunday, May 28, 2006 at 17:47

Sunday, May 28, 2006 at 17:47
The maximum output of a Unisolar 64watt panel in perfect conditions is ,,,,,,,,,,,,, wait for it ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, time for another scotch ,,,,,,,,,,, 3.78 amps ,,,,,,,,,,, never mind the V x A = W or W divided by A = V or A x V = W or any other combination ,,a Unisolar 64 gives out 3.78 amps ,, the only way the actual voltage varies is due to the regulator ,,maters not 1 iota 1f the battery likes 14.2v or14.8v the maximum amps the panel will produce is 3.78Amps per hr in perfect conditions.
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Follow Up By: Member - Mike DID - Monday, May 29, 2006 at 17:27

Monday, May 29, 2006 at 17:27
. . . . exactly.

People would get a lot less confused if they thought of a Solar Panel putting out constant current (at a particular light level and temperature)- whether its connected to an 18 volt battery or a zero volt battery.

Mike
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Reply By: greenant - Sunday, May 28, 2006 at 17:11

Sunday, May 28, 2006 at 17:11
What about the 1st April no amps no volts
AnswerID: 175211

Reply By: GaryInOz (Vic) - Sunday, May 28, 2006 at 17:24

Sunday, May 28, 2006 at 17:24
.......and leap years??????

64 watt panel will deliver a peak of 64 watts at a certain voltage in full sunlight. If you connect a battery across the panel, then the "output" voltage of the panel is reduced, along with the current, and therefore the total power output of the panel is reduced (not in a linear fashion, see you spec sheet on the power curves for the panel). Rely on about half to two thirds of the "rated" output.

Regulator will not increase the current, it actually dissipates some of the power as heat in the process of regulating the voltage output from it into the battery. There may be some switchmode regulators that are capable of increasing the current marginally as a tradeoff for reducing the voltage, but it wouldn't be worth the extra cost.
AnswerID: 175214

Reply By: Derek from Affordable Batteries & Radiators - Sunday, May 28, 2006 at 20:06

Sunday, May 28, 2006 at 20:06
Here is a graph on my BP80 panels.



You can see heat does affect the amps but not a lot. Your biggest factor is that as the battery charges up it will absorb less amps. The final charge cycle could take quite a long time.

Remember that although the amps may be around 5 amps on a 80w panel your battery will not absorb the full 5 amps all day.

Regards Derek.
AnswerID: 175251

Follow Up By: rooster1070 - Monday, May 29, 2006 at 09:36

Monday, May 29, 2006 at 09:36
Thanks derek, very helpfull

Chris
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