Lithium Battery Charging
Cargo Master
Joined: Mar 2007
Posts: 2,822
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Same way with me. I do know the times where we were not, my wife did not complain about anything. She figured we were just plugged in. That was the goal. Even the microwave does not even lose time. So far, I've gone 4 days and was at 60%. I figured I could go a week. Obviously with no A/C. I suspect I could run the A/C for about 5-6 hours, but I don't think there would be a time where I would do that.
Fleet Mechanic
Joined: Jul 2018
Posts: 1,617
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From: Black Hills of SD
Our Microwave and AC are not connected to the inverter so I need shore power for those. I run our generator if those are needed. The batteries only run the fridges and a couple extra outlets (TV/Sat/etc.) when we are not plugged in....
Mountain Pass
Joined: Dec 2020
Posts: 233
Likes: 126
From: Western NC
Victron orian xs 12/12 50. Mount it preferably near your battery, but you'll need to intercept the charge wire off your 7 pin. In the victron app limit the incoming current to 10 or so amps. Depending on your truck, I went on the safe side at 10a. Spend the money on the xs so in the future if you want more charging you can wire from you truck battery through an Anderson and charge up to 50a.
Unless I'm running air conditioning off the batteries 10a has been plenty in my experience. I personally wouldn't even attempt more than 20a on the 7 pin.
Unless I'm running air conditioning off the batteries 10a has been plenty in my experience. I personally wouldn't even attempt more than 20a on the 7 pin.
Getting ready to have a DC to DC charger installed. If I understand this correctly, I can intercept the 7 pin charge wire using the Victron App?
Thank in advance.
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From: Home Base Nebraska
Denny
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From: Home Base Nebraska
Denny
Cargo Master
Joined: Mar 2007
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You are forgetting about the length. I don't know, but I can see that wire being 20-30 feet [from the alternator to the trailer battery]. I am just pointing out something that I don't think that is being looked at. Just an opinion. Maybe you have. I know, there is no way I would have that small of a gauge at that length. E
The DC/DC charger just does not magically make more voltage without sucking more current.
https://www.cerrowire.com/products/r...pacity-charts/
The DC/DC charger just does not magically make more voltage without sucking more current.
https://www.cerrowire.com/products/r...pacity-charts/
Moderator
Joined: May 2004
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From: Home Base Nebraska
The charger limits the current draw so the max is 20 amp on mine. I would never go over 20 amp on stock wiring.
Denny
I will add I replaced the wimpy cord end on my 7 pin cord with a replacement that has larger contact area.
Denny
I will add I replaced the wimpy cord end on my 7 pin cord with a replacement that has larger contact area.
Last edited by rvpuller; Nov 9, 2025 at 11:00 AM.
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Cargo Master
Joined: Mar 2007
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Yes, it will only deliver 20A, but how much will it suck to make that 20A?
If you understand how electricity works, on long runs, there is a voltage drop. With more current, there is more of a drop. If you loose 1V from the alternator to the DC/DC converter, how do you think the converter makes the voltage go up AND provide 20A? It has to draw more current. A voltage drop test is very simple and if you system is indeed up and running, you should test the circuit out. Under full load conditions. If there is no current draw, there would be no voltage drop.
Don't get made at me, it's just how electricity works. That is why the longer the circuit, the larger the gauge to keep the voltage drop lower.
If you understand how electricity works, on long runs, there is a voltage drop. With more current, there is more of a drop. If you loose 1V from the alternator to the DC/DC converter, how do you think the converter makes the voltage go up AND provide 20A? It has to draw more current. A voltage drop test is very simple and if you system is indeed up and running, you should test the circuit out. Under full load conditions. If there is no current draw, there would be no voltage drop.
Don't get made at me, it's just how electricity works. That is why the longer the circuit, the larger the gauge to keep the voltage drop lower.
Cargo Master
Joined: Mar 2007
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Then you should understand that the limit is somewhere. The chargers are rated at output, not input. If you got 20A output, there is an efficiency loss, so it has to take more than 20A to make that happen. Then you look at the drop in voltage, which makes the draw even more.
As a retired electrician [I'm just a dumb auto mechanic for 40+ years] you would know that if the input voltage is 12v and the output voltage is 14v, something happens to the current. If you are sucking on a straw to get the most out of your Big Gulp, if the straw is 40 feet long, you are not going to suck that much, certainly less than a 10 inch straw of the same diameter.
As a retired electrician [I'm just a dumb auto mechanic for 40+ years] you would know that if the input voltage is 12v and the output voltage is 14v, something happens to the current. If you are sucking on a straw to get the most out of your Big Gulp, if the straw is 40 feet long, you are not going to suck that much, certainly less than a 10 inch straw of the same diameter.
Last edited by 1Butcher; Nov 9, 2025 at 11:27 AM.
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From: Home Base Nebraska
The current is limited on the input so it won't overload the input wiring.
I wasn't sold on it when I first bought it but after checking all the voltage drops to the charger I was surprised when the output charging voltage was 13.6 with input voltage at 10.9 under load, truck was at idle.
Denny
I wasn't sold on it when I first bought it but after checking all the voltage drops to the charger I was surprised when the output charging voltage was 13.6 with input voltage at 10.9 under load, truck was at idle.
Denny
Cargo Master
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That is what they do. It's a great idea. There are a systems in cars that do the same thing. Mercedes made a few models with a brake by wire system. It would have a backup battery that was designed to always give system voltage to the brake controller, no matter how low the main battery was. You don't want the brake system to stop working because of low voltage.
I certainly can see that there are safety measures on the input side as well as the output. Victron makes some high quality stuff. Too rich for my blood.
So what was the current when the input voltage was at 10.9v?
I certainly can see that there are safety measures on the input side as well as the output. Victron makes some high quality stuff. Too rich for my blood.
So what was the current when the input voltage was at 10.9v?
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Joined: May 2004
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From: Home Base Nebraska
Mine is a Renogy charger that doesn't have bluetooth so I can't monitor input or output current, I just do it the old fashion way with a voltmeter and fuses to protect from over current. My 2000 watt inverter was bluetooth so I could monitor the voltage going down the road but that part of it died so I use the volt meter inside the trailer when we stop. I been using it long enough I don't really pay that much attention to it anymore.
Denny
Denny
Cargo Master
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What is the term used on the internet? Friends don't let friends buy Renogy.
I have a Renogy 3k inverter. My first one was a dud. It took weeks to get this warrantied. I was going camping too. I ended up buying a new Renogy 3k inverter and sending my bad one back for the return. It was the only way I could get one back in time to go camping. Their warranty system seems to revolve around asking you to do a bunch of work, make videos, etc before they even think that their product is bad. Sadly, I'm not their employee. I get that many don't know that much about electronics, but it is pretty basic. I had 4 0 cables that were less than 2 feet from the 600ah batteries, fused too. No AC out. How hard can it be?
So, because of their warranty policy, I will not ever buy their product again.
I have a Renogy 3k inverter. My first one was a dud. It took weeks to get this warrantied. I was going camping too. I ended up buying a new Renogy 3k inverter and sending my bad one back for the return. It was the only way I could get one back in time to go camping. Their warranty system seems to revolve around asking you to do a bunch of work, make videos, etc before they even think that their product is bad. Sadly, I'm not their employee. I get that many don't know that much about electronics, but it is pretty basic. I had 4 0 cables that were less than 2 feet from the 600ah batteries, fused too. No AC out. How hard can it be?
So, because of their warranty policy, I will not ever buy their product again.