Measuring output from Solar Panels

Submitted: Saturday, Jan 15, 2005 at 19:14

ThreadID: 19405 Views:7919 Replies:2 FollowUps:6

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Member - Moggs

Sorry if this sounds stupid but if you never ask you will never know....

...I have recently purchased some solar panels and a digital multimeter. My question is how do I actually (and safely without shorting anything) measure how many Amps the panels are putting out at any given time???

I also have a Waeco fast charge kit wired to the alternator that terminates at a Hella plug in the rear. How do I measure how many amps this is putting back into the battery???

Any info greatly appreciated.

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Reply By: David Au - Saturday, Jan 15, 2005 at 19:45

Reply By: Eric Experience. - Saturday, Jan 15, 2005 at 22:15

Saturday, Jan 15, 2005 at 22:15

Moggs.
A very easy way of monitoring battery current is to measure the the voltage on the battery negative terminal compared to the chassis. the voltage will be only milivolts but it is simple and does not require cutting or buying. Eric.

AnswerID: 93307

Follow Up By: David Au - Sunday, Jan 16, 2005 at 13:53

Sunday, Jan 16, 2005 at 13:53

Eric Experience you may like to enlighten everybody on this method of yours. Please give a detailed explanation so everybody can understand the methodology.

FollowupID: 352386

Follow Up By: Member - Sparkie (QLD) - Sunday, Jan 16, 2005 at 14:37

Sunday, Jan 16, 2005 at 14:37

I am afraid you lost me as well?????????????

Sparkie(IE not Y) ;-)

FollowupID: 352395

Follow Up By: Mainey... - Monday, Jan 17, 2005 at 01:28

Monday, Jan 17, 2005 at 01:28

0zi,
is Eric Experience a really good mate of yours, I have never seen you be so nice, calm and even polite to a post that is so far off base?

I would want to know what Eric is using to actually measure the battery power with, if (Quote) "and does not require cutting or buying" (end quote) is correct ?

Bugga me I'm in agreement with 0zi....{better pop anutha pill} roflmfao.

FollowupID: 352486

Follow Up By: Wok - Monday, Jan 17, 2005 at 07:19

Monday, Jan 17, 2005 at 07:19

Hello,

EE suggested this method yonks ago on a post about battery monitors.
It requires measuring the impedance of the ground return, then using [V sq/R] = W or Ohm's Law to get the current.
Problem was a milliohm meter is not a common tool in most kitbags.

It got filed into the 'Too-hard-basket'

EE's method is valid......just hard to implement.

cheers

FollowupID: 352495

Follow Up By: Eric Experience. - Wednesday, Jan 19, 2005 at 22:04

Wednesday, Jan 19, 2005 at 22:04

Gentle men I am happy to give more detials of the easy and safe way to measure battery current. In a comercial amp meter there is a very low value resistor called a shunt and there is a meter that goes on the dash which is wired across this resistor, what the meter on the dash measures is the milivolts drop across the shunt. The major problems with this set up are, 1. fire risk and 2, voltage drop. The fire risk is because you have a high current cct which all the battery current must pass through and therefore you can not fuse it, you then have wires from it to the dash. The inclusion of a common resistor in series with a battery causes a small voltage drop but that voltage with its variations, like for example injector pulses, is imposed on all other ccts. If you measure the voltage across the earth lead of the battery the mili volt meter is near earth so has no fire risk. The voltage drop still exists but it is one that is already there and you are not adding to it. There is no shortage of milivolt meters they are called varius things but a "centre zero 100ma meter" is the cheapest form, To callibrate your meter add resistance in series to reduce the reading or use a slightly longer earth strap to increase the reading. Eric,

FollowupID: 352951