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Battery charging - RV to RV


ALLOY
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We are drycamping at beautiful site next to a lake. 

The only thing wrong with the site is the people that pulled in 3 days ago are running a generator (Champion) for 4 hours either morning, afternoon or evening.

The generator is not being loaded which makes me think it is only used to charge batteries.

This situation has me thinking about how a solar system could be used to charge the battries in another trailer that is 200'-300' away.

I'm thinking 110v extension cords from an inverter to a battery charger or the shore power plug in the other trailer.

Ideas?

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It is definitely possible, but it is reliant on the capacity of the the main system being used to charge the other system.  The main system would have to be sufficiently large enough to replenish its own usage and also the usage of the secondary RV.  It is inefficient to go from DC (solar) to AC (inverter) then back to DC (converter in other RV) to charge batteries, so it would have to be a pretty robust system to keep two RV's up and running.  I know of a few people who have large enough systems to do this (and actually have done it), but these systems are the exception in the RV solar world.  Most RV solar charging systems are sized for the RV they are attached to and aren't typically large enough to also support a second RV.  It would be much more efficient to have a portable panel/solar controller system with gator clips or some other quick means of connecting it to the desired battery bank.  This system could be loaned or provided to those that don't have solar on their rigs.

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Alloy, when you're talking about providing charge to an RV 200 to 300 feet away, that pretty well precludes low voltage DC transmission  due to the voltage drop across such a long run and the necessity of using huge heavy expensive copper wires...……

 Being left with using extension cords to run 120 VAC that far also has some voltage drop issues (but less then 12 VDC) PLUS there are double inefficient heat losses when Inverting 12 VDC to 120 VAC (at donor RV) and then again 120 VAC to 12 VDC for charging (at remote RV). 

 NEITHER are very practical certainly not efficient methods even though sure its possible given big enough wire and sufficient batteries, chargers and inverters and solar capacity.

That being said, for relatively low battery charging capacity its easier to carry and pack out a small suitcase style fold out 200 watt panel with its built on/in solar charge controller BUT YOU DONT WANT TO CARRY IT JUST FOR A NEIGHBOR I ASSUME ??

Had you said maybe 50 feet away its more doable, but at 200 to 300 feet low voltage DC (unless there's one huge charger and you use huge wires)  isn't practical while 120 VAC transmission (from donor RV) with a Converter/Charger (on remote) RV might be done but the Converter/Charger and Inverter combined may be loosing at least 20%

 As an Electrical Engineer I just don't like either plan, even if in theory it can work depending on the equipment.  

 John T  

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Thanks Chad and John.

At this time of year we consume +/- 65Ah (845Wh)  from dusk to dawn. Our solar will then bring the batteries into float around 10:00AM. One could say the power for the rest of the day is being wasted. Better to waste it keeping thing quiet. 

I was looking at line losses.  Ten guage wire will carry 10 amps of 120V for 200' with a 5% loss. I'm thinking this might run a 40A battery charger/converter.

Didn't think of the portable solar.  In our last trailer a LED light caught fire close to a Victron 150/100 controller. Insurane wrote the controller it off due to smoke damage but the electronics are sealed and it still works. We already carry portable panels.

This may work!

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I think you could use this type of charging to finish charging the second RV's batteries. Maybe use a robust charger with the generator to do the bulk charging and finish with the 120 volt extension cord method.  Running a generator to top off batteries is very inefficient and time consuming.   We have done this but the solar was was not large enough to do it every day without sacrificing usage in the 1st RV.

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  • 2 years later...

You can recharge the battery using a variety of techniques, the most effective of which is utilizing the RV generator. You no longer have to dread if your battery gets drained while you are in the middle of your camping trip. You just need to prepare your batteries, hook up the generator to your RV and wait a couple of hours to get them running again.

Edited by johnpeters
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John, actually you will charge the RV batteries faster using an external battery charge rather than charge trough the converter/inverter.  Most converters have a limited output charge circuit.  So run the generator, but let it power a external battery charge hooked to the batteries.

To the OP, in regards to the noisy Champion generator, ask them to move it to the opposite side of their RV putting their RV between you and the noise source.  I can knock down the noise ab a considerable amount.  Now it might not be good for the people on the other side of them.

Ken

 

Edited by TXiceman
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11 minutes ago, Kirk W said:

Most portable generators have a 12v output but I haven’t used one to charge a battery. Has anyone done that and if so, how well did it work?

In most cases, plugging in to the 120V output & using your converter will charge much faster.

Edited by vermilye
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Drives you nuts, doesn't  it?  You have the ideal spot, and then a generator moves in, and runs until 10pm so they can watch TV.  Champions aren't the quietest around.

I carry several Hondas and have been tempted to lend one to the generator-dependent rather than sit and stew about it.  Then I have to worry about them leaving with it.

I also would consider running an extension cord to their place, given I have a lot of solar and a  big inverter.

Edited by hemsteadc
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3 hours ago, Kirk W said:

Most portable generators have a 12v output but I haven’t used one to charge a battery. Has anyone done that and if so, how well did it work?

Not well. On most generators the 12 volt current capacity is equal to the 120 volt amperage (they just tap the output coil for the lower voltage), so a 2000 watt generator will have about 15 amps maximum current available from the 12 volt output.  It's also unregulated so the current goes down as the battery gains charge.

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2 hours ago, Lou Schneider said:

Not well.

In all of the time that I had my Honda 200i, I don't remember every using the 12V output I did run a battery charger from the 120V side at least once, that I recall but that was for a friend. I actually used it very little, with the most being to supply power for a few things at my home-base when we were without power from the REA. 

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Typically the 12 VDC output of a small portable genset is NOT extreme high amperage, its designed more for powering small 12 VDC tools and appliances at a fairly constant DC voltage then regulated staged "battery charging".. While sure it may provide some degree of charging, its nothing compared to how a modern regulated so called smart charger can properly charge a battery when using the genset to provide its 120 VAC input power. As far as how fast a battery can be charged, it depends on if you use an industrial shop type battery charger versus a staged regulated smart charger like many RV's use. If the distances are great trying to charge at 12 VDC direct may (subject to wire size and distance) result in excess line voltage drop verus if you use 120 VAC and extension cords. LIKE YOUR EXTENSION CORD IDEA a quality low noise inverter generator plus a charger located at the remote RV,,,,,,,,, or solar is my preferred method over a an open frame loud noisy screaming 3600 RPM construction genset grrrrrrrrr lol   

John T

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I just found some specs for the Honda 2200i at 12V, 100W (8.3A).  That means a pretty slow charge. I also found where the operator's many does state that the DC output is unregulated and a constant current and does not decrease as the battery reaches full charge. Clearly, the way I always did it using 120V to supply my automotive battery charger is much better. I suspect that 12V output is a bit of an after thought. 

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12 hours ago, Kirk W said:

That means a pretty slow charge. I also found where the operator's many does state that the DC output is unregulated and a constant current and does not decrease as the battery reaches full charge.

 

17 hours ago, oldjohnt said:

Typically the 12 VDC output of a small portable genset is NOT extreme high amperage, its designed more for powering small 12 VDC tools and appliances at a fairly constant DC voltage then regulated staged "battery charging".. While sure it may provide some degree of charging, its nothing compared to how a modern regulated so called smart charger can properly charge a battery when using the genset to provide its 120 VAC input power.

That's about what I expected (absent any factory specs or data), thanks for verifying...

John T

Edited by oldjohnt
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12 hours ago, Kirk W said:

I just found some specs for the Honda 2200i at 12V, 100W (8.3A).  That means a pretty slow charge. I also found where the operator's many does state that the DC output is unregulated and a constant current and does not decrease as the battery reaches full charge. Clearly, the way I always did it using 120V to supply my automotive battery charger is much better. I suspect that 12V output is a bit of an after thought. 

Kirk, 

I didn't do any reading or testing other than hooking it up to my truck batteries when it was sitting away from an electric connection for too long. It took a combination of that power, jumper cables from my Isuzu and the mobile battery box from the truck repair shop to get my truck started. I had just walked in asking for an estimate on replacement batteries and told them if it didn't start this time I would be in to purchase the batteries. The truck started and I got about another year from the set before I found one of the batteries with a bad cell.  I now make sure I'm close enough for my trickle charger to keep the three batteries topped off when the truck is sitting. 

 

Rod

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On 9/16/2021 at 10:46 AM, Kirk W said:

Most portable generators have a 12v output but I haven’t used one to charge a battery. Has anyone done that and if so, how well did it work?

My Boliy 3600 inverter series genset has an 8A DC charger, which IMO is rather puny for battery charging. OTOH my Onan 7.5  kw genset powers my Xantrex RS2000 inverter/charger with a maximum output of 100A.

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On 9/3/2019 at 11:26 AM, oldjohnt said:

Alloy, this is one of those situations where if your RV has the capacity (plenty of solar and inverter and battery) and depending on what the remote RV requires,  there's nothing wrong with trying it out even though its NOT perfect or an ideal operation. Hey go for it.

  John T

  

We were back at the same campsite a weeks ago with 2 trailers plugged into ours. It would have been better if they plugged in the first day rather than waiting until the 2nd day. The 3rd day our system was at 76% so I brought out 2 more 330W panels. On the 4th day we were back up to 100%. During this I was also charging two 5Ah batteries for my EGO chainsaw.

Our Starlink dish showed up just before the trip and we were able to change the location to the campsite so everyone tested that out.  At this point Starlink is not as mobile as we hoped. Half of the places we like to go are either full or do not have service.

Edited by ALLOY
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Hey Alloy, I bet you have a lot of friends that want to camp by you so they can plug in lol  Hey I don't blame them sounds like you have an abundance of power, way to go !!!!!!!!

According to Mobile Internet Resource Starlink just started launching more satellites but its gonna be a while before they are at capacity, have patience...  

 Best wishes thanks for the updates

 John T

 

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21 hours ago, ALLOY said:

Our Starlink dish showed up just before the trip and we were able to change the location to the campsite so everyone tested that out.  At this point Starlink is not as mobile as we hoped. Half of the places we like to go are either full or do not have service.

At this  time  it is not designed for mobile use...at least not easily.

Edited by hemsteadc
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