Measuring V loss during charging
I know that a discharged battery can pull down the voltage at the charger. I was trying to measure voltage loss in my converter wiring, switches, etc. The two 105 AH batteries were 12.13v prior to ...
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I used the voltmeter trick (Salvo taught me this) to get the R by adding about 25 ft of speaker wire to one of the voltmeter leads (doesn't matter which one you pick) and alligator clamp ends.(you can't be in two places at once :) ) That long speaker wire did not affect the voltage readings.
I got my amps from the Trimetric for converter-battery paths.
This let me measure between the "battery lugs" at the DC fuse panel inside the trailer out the door and up to the batteries in front.
You get one R for the positive path and another for the neg path. The neg path could be much less than the positive path because it uses the trailer's frame, and the positive has that skinny wire and maybe a switch. (switches and fuse holders are bad for R) It is the total of the two Rs that counts for what amps you will get to the battery from the converter.
First priority is to reduce the R of the positive path which is the big R. You can also make some improvements to the neg path if there is any corrosion at the frame contact points for the short neg path wires.
Progress was measured by the increased amps when R was reduced. There is a limit where there is no point in reducing R anymore once the converter is at its max amps.
It is better not to use the batteries for this testing because they have so much R themselves (more on that below) and it keeps changing. Best to get a big draw on the batts from the inverter running a kettle and see the amps for that, then turn on the converter and see how many amps the Trimetric shows then.
Eg, converter off, kettle on, Tri shows -90amps. Turn on converter, kettle still on, Tri shows -60amps. Means the converter is doing 30 amps. I was able to reduce total R by various means so that the 7355 was doing 56 amps. However on the same paths total R with actual battery charging on low batts, the amps start off at more like 45a and taper quickly to the 30s-mid 20s. That is way better than before though! And at 13.8v too.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26711816/srt/pa/pging/1/page/3.cfm
I got my amps from the Trimetric for converter-battery paths.
This let me measure between the "battery lugs" at the DC fuse panel inside the trailer out the door and up to the batteries in front.
You get one R for the positive path and another for the neg path. The neg path could be much less than the positive path because it uses the trailer's frame, and the positive has that skinny wire and maybe a switch. (switches and fuse holders are bad for R) It is the total of the two Rs that counts for what amps you will get to the battery from the converter.
First priority is to reduce the R of the positive path which is the big R. You can also make some improvements to the neg path if there is any corrosion at the frame contact points for the short neg path wires.
Progress was measured by the increased amps when R was reduced. There is a limit where there is no point in reducing R anymore once the converter is at its max amps.
It is better not to use the batteries for this testing because they have so much R themselves (more on that below) and it keeps changing. Best to get a big draw on the batts from the inverter running a kettle and see the amps for that, then turn on the converter and see how many amps the Trimetric shows then.
Eg, converter off, kettle on, Tri shows -90amps. Turn on converter, kettle still on, Tri shows -60amps. Means the converter is doing 30 amps. I was able to reduce total R by various means so that the 7355 was doing 56 amps. However on the same paths total R with actual battery charging on low batts, the amps start off at more like 45a and taper quickly to the 30s-mid 20s. That is way better than before though! And at 13.8v too.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26711816/srt/pa/pging/1/page/3.cfm
