Renogy DC-DC Test Results-UPDATE 4 (Better!)
Updates 23 June--new test with Renogy input exposed for voltage readings Update 25 June more readings Update 4 - 27 June-- fewer amps with fat wire were noted this time! ----- I have the 20 ampe...
Forum Discussion
Decided first to check input voltage at the Renogy with things the way I had them before the OP tests. So no ammeter inserted outside on the pos input wire (7-pin) --- did not take this before because no access to Renogy input terminals, now have access.
Got 10.42 volts input, output was 19.4a on Trimetric on battery, meaning 20a at the Renogy termninals allowing for voltage drop. Amps held steady, no tapering this time.
So actually, it works right the way I had it. I blame the additional R of the ammeter and its connections for the lower input voltage during the test, and the tapering, but:
The Renogy specs say it works with 8 -16 volts input and it has a low voltage shut-down at 8 volts input and it did not shut down during the OP test. I had a 1 volt drop from the ammeter to the Renogy input and 9.88 volts at the ammeter, so assume 8.88 at the Renogy.
So it was near the low input limit but not to 8 and shut-down and output amps tapered. It did ok with the test 11.84 (assume 10.84 at Renogy) with the fat wire test.
With this test of as it was set-up, 10.42v input and it worked compared with that assumed 10.84v that worked.
On the "shared negative ground" issue, there is nothing about that in the manual that came with my unit, but there is in the manual you get linked to here:
https://www.renogy.com/content/RNG-DCC1212-20-BC/DCC1212-204060-Manual.pdf
So beats me. I guess the 7-pin neg connection is good enough whatever the electrons are all doing there.
I can add fatter wire to input and improve my installation for output now I have it all exposed, but it appears I don't really need to. I am getting the steady 20a out, no tapering. I don't care what the amps draw is--assume 30 amps as seen on the ammeter.
My owner's manual does not suggest the draw would be less with fatter input wiring. It just says flat out, that with max output amps the draw will be 50% higher. That is what I saw with the test when I switched to fatter wire--still 30 amps.
Got 10.42 volts input, output was 19.4a on Trimetric on battery, meaning 20a at the Renogy termninals allowing for voltage drop. Amps held steady, no tapering this time.
So actually, it works right the way I had it. I blame the additional R of the ammeter and its connections for the lower input voltage during the test, and the tapering, but:
The Renogy specs say it works with 8 -16 volts input and it has a low voltage shut-down at 8 volts input and it did not shut down during the OP test. I had a 1 volt drop from the ammeter to the Renogy input and 9.88 volts at the ammeter, so assume 8.88 at the Renogy.
So it was near the low input limit but not to 8 and shut-down and output amps tapered. It did ok with the test 11.84 (assume 10.84 at Renogy) with the fat wire test.
With this test of as it was set-up, 10.42v input and it worked compared with that assumed 10.84v that worked.
On the "shared negative ground" issue, there is nothing about that in the manual that came with my unit, but there is in the manual you get linked to here:
https://www.renogy.com/content/RNG-DCC1212-20-BC/DCC1212-204060-Manual.pdf
So beats me. I guess the 7-pin neg connection is good enough whatever the electrons are all doing there.
I can add fatter wire to input and improve my installation for output now I have it all exposed, but it appears I don't really need to. I am getting the steady 20a out, no tapering. I don't care what the amps draw is--assume 30 amps as seen on the ammeter.
My owner's manual does not suggest the draw would be less with fatter input wiring. It just says flat out, that with max output amps the draw will be 50% higher. That is what I saw with the test when I switched to fatter wire--still 30 amps.
