[Elecraft] Using the KX1 on Solar Power

[Don Brown]

Hi

Thanks for your input and this is exactly the method I use to check my 
panels. I just suggest the resistor method because some DVM's do not have 
current ranges and the possibility of damage to the current ranges if the 
wrong range is used. Measuring current with a DVM is always a possible 
problem if you forget the meter is on current and then measure a voltage 
source. Most meters are now protected with a fuse but it is a hassle if the 
fuse blows. The resistor method is safer but not necessarily better.

Don Brown




----- Original Message ----- 
From: <G3VVT at aol.com>
To: <DolfinDon at msn.com>; <elecraft at mailman.qth.net>
Sent: Wednesday, June 22, 2005 12:20 PM
Subject: Re: [Elecraft] Using the KX1 on Solar Power


>
> In a message dated 22/06/05 15:26:09 GMT Daylight Time, DolfinDon at msn.com
> writes:
>
> You can  test the output current by connecting a 10 ohm 5 watt resistor
> across the  panel and measuring the output voltage
>
>
> Reply: .....................................................
>
> In practice you do not even need to do that.
>
> During some commissioning of a large solar powered microwave system I was
> involved with about 5 years back that used up to 15kW of solar power  at 
> each
> site (200 x 75W 12V solar panels), the contractors who installed the 
> system
> tested the output by connecting an ammeter effectively directly across 
> the solar
> panel output terminals. When I raised the question would this not  cause
> damage? They came back quite rightly, no, the current will limit at what 
> the
> solar panels are capable of providing. In these installations  the total 
> array was
> divided into 12 banks of 48V sections with panels in series  and parallel 
> to
> make up the arrangement. As the current involved was  considerable the 
> method
> involved was to place a heavy gauge piece of wire after  the solar panel
> breaker and when the bank was activated measure the  resulting current 
> through the
> piece of wire with a calibrated AC/DC clamp type  current sensor and a 
> DVM.
>
> With the type of solar panels normally used by hams, probably a  DVM on a
> suitable current range direct across the solar panel terminals would do 
> the job.
> You have to take care that the panel being tested is isolated from all 
> other
> power sources such as batteries, but at the end of the day the panel will
> not supply any more than what it is rated to give.
>
> Don, KD5NDB was very correct on the need for a blocking diode to be 
> inserted
> in series with each solar panel when multiple panels are in use, 
> otherwise a
> panel in shade where the other(s) are in illumination, could  absorb the
> power being generated by back feeding into this panel.
>
> Larger sized panels normally have the blocking diode included inside the
> panel assembly or terminal box. In addition they have  internally what I 
> believe
> are called bypass diodes to prevent the  panel limiting the voltage within
> itself when part of the panel is in  shade where the rest is illuminated.
>
> Bob, G3VVT