How to Measure (and Reduce) Voltage Drop in Van and RV Power Systems

[@rosslukeman]

Get the Ultimate Van Power Cheat Sheet: www.rosslukeman.com/vanpower

[@herkko61]

I think this lesson can not be made better by anybody, it's perfect! Thank you.

[@rosslukeman]

Thanks man, I appreciate that!

[@HomebuiltHELP]

Ross - Well done presentation - effectively illustrates the real world relationship between resistance and voltage drop. Not everyone may appreciate the simple relationship described by ohm's law - but your demonstration shows the why and how this is useful in these circuits. Also - a loose connection will be identified by your method of measuring voltage drops across devices. What you are showing could eliminate the need to check lug nut torques on live circuits by simply testing voltage drops across bus bars, switches, shunts, etc. Thanks for the video!

[@rosslukeman]

Thank you! I did want to bring it real-world instead of just doing calculations only. By the way, great channel and super cool website. That is inspiring! Ross

[@ericalanbrody]

Always enjoy watching your video - breaking down complex subjects and illustrating it bit by bit. Thank you for all you do!

[@rosslukeman]

Hi Eric, thanks for tuning in and for the kind words! I appreciate it-

[@Myrune1]

Every RV I've ever owned has had this issue. I usually try to move the charger nearer the batteries, but sometimes you just have to put in larger wires. Most of them come with seriously undersized cables from the manufacturer. I owned one RV where they used 8 gauge wire on a 15 foot run with 4 golf cart batteries and a 70 amp charger. That charger would take more than a week to fully replenish those batteries. (Most people don't even notice because they are on shore power all the time.) I moved the charger and changed the cable to 2 gauge with an 18 inch run. Those batteries would fully charge in much less than a day. Big difference. I've fixed many other's RVs with same way. It's the same problem.

[@jasonbroom7147]

Something implied, but not directly discussed in the video, is how the voltage at the charger was decreased by right-sizing the cable size and length of run, which allowed the full flow of current (amperage) through to the battery. Your charger is more efficient, as is the entire system, when using the right size of wire for the voltage and the total length of the run. It may be self-evident, but this is why you want to keep cables as short as possible, and also why you want similar length of cable runs for both positive and negative cables.

[@sdotperez]

Hey Ross - I’ve watched and learned from your videos and appreciate them. My van electronics and Simarine are 80% complete because of these! Can you make a tutorial of solar panels and charge controller running through Simarine? I’m having issues with my set-up.

[@rosslukeman]

Hi Steve, my next video will be with Simarine VIA and I will look to add a charge controller to that setup. I am tied up for the next couple of weeks but I will get that video out soon. If you need a consult, I do those Thu-Sat each week. www.rosslukeman.com/offerings Thanks for tuning in!

[@sdotperez]

@@rosslukeman that's awesome, thank you! I'll follow the link provided to see what works for me.

[@garymiller7870]

Thank you Ross, Two questions: 1) Normally I would measure the voltage drop from the pos charger terminal to the pos battery terminal and again on the neg side. Does your method provide different data? and 2) Is there a concern if the charger is wired directly to the batery? The charger has an off node and is internally fused.

[@vounovapor]

Great video!! As a beginner I miss two things in this fantastic video: 1) Voltimeter screen embedded video to share with us the measuring mode... I'm used to use it just for voltage messure between positive and negative. No idea on how to use it to measure the voltage drop inside positive side, within all the barriers: bus bat, etc 2) Is there any bad side effect in using a thicker cable than necessary? I mean, it is said that short and thick is better, and I can grasp it related to lengh but what about the cross section of the cable?. Thanks in advance.

[@rosslukeman]

Hey there, thanks for tuning in! Per your points: 1) the measuring mode was DC voltage. I don't have a 2nd camera at this point to capture the device's screen. As long as current is flowing, you can put the prongs on two locations of a positive wire and get the voltage difference between the locations. It's measuring the difference between point A and point B, just like measuring positive vs negative. It's still measuring voltage difference. 2) No there's no harm in using a thicker cable than necessary. It's the same as using a bigger water pipe to carry a certain amount of water. It costs more, but doesn't hurt anything. Hope that helps!

[@keithanderson9606]

Thank you sharing your knowledge. I have that chager and at 30 amps charging the charger gets really hot 130 degrees F. Is that normal? Thank you

[@rosslukeman]

Hi Keith, unfortunately yes it gets pretty darn hot, I was using it yesterday. Just give it plenty of room to breathe I would say. Thanks for tuning in!

[@bybeka1]

Very well explained, thanks!

[@rosslukeman]

Thank you!

[@OdisseiaMundana]

Great presentation! Thanks for sharing this precious information.

[@rosslukeman]

Thank you, I'm glad you got something out of it!

[@dan32one44]

Good 👍 stuff

[@rosslukeman]

Thank you!

[@jimmyjimjim3054]

How do you feel about 24 volt systems for larger Motorhomes?

[@brlowe1]

I do not know how he feels about it but I did a 24v system in my RV and I have 2 items that I have to use converters for to run at 12V. Other than that my system is nice and clean and the larger cables are smaller than what I would have needed for a 12v system.

[@jimmyjimjim3054]

@@brlowe1 That's great. Thanks for taking the time.

[@rosslukeman]

Hey Jimmy, well I would just say what I said in the video still applies. Converter losses and potential trouble with solar. However, with 24V the solar thing is less of an issue. You still have to get your panels above 26 volts (really 31 volts) to start charging so instead of 8am your panels may not reach that until 11am. So you lose some charging hours. If you can wire your panels in series where their nominal voltage is 3x to 4x your batteries, then great, no problems. On the conversions, it's okay if you're running lights and a vent fan. The big issue is converting power for big items that perhaps run for hours and hours. This would be fridges and DC air conditioners. If you can get a 24V version of those, that would help. Otherwise there's no right answer, and the other commenter appears to have a successful 24V system. By the way, thank you for thanking him for his input, we are bringing more courtesy to the internet hopefully. Thanks, Ross

[@rosslukeman]

@brlowe1 thanks for sharing your experience with this!

[@brlowe1]

@@rosslukeman Your the expert and that is way I watch your videos. Your right about 12v stuff on a 24v system, my AC is 12v going thru a Victron 70amp converter and that thing gets hot. I wish I had a 24v AC unit. Maybe in the future

[@OrlandoPaco]

Love the video, comedy and all. But wouldn't it give us a more apples to apples with the same "length" wire. We do know that the longer the wire the bigger the loss.

[@rosslukeman]

Hi Orlando, thanks for tuning in, great to hear you enjoyed the video. On the testing criteria, my goal was to show voltage drop. Every time I do a test like this, people say I should have done the test in a different manner. This is probably a one-off video, just trying to show the concept, but I appreciate the feedback.

[@luidabruin]

He is not happy.... Lol