Adding weight in one corner of RV - Solar install under Dinette?

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Adding weight in one corner of RV - Solar install under Dinette?

January 29, 2021, 02:35:19 pm

Hi again! I am working on a solar upgrade. The easiest and biggest spot I have to install Lithium batteries and an Inverter is under my dinette bench. On my 27 RK the bench is on the far right rear corner of the RV. I'm worried about adding all that weight (perhaps 120-160 pounds) to one spot. Another concern is I would have to run longer wires. I think the only other option is to lose a drawer or two and move the water pump. Any thoughts?

Re: Adding weight in one corner of RV - Solar install under Dinette?

Reply #1 – January 29, 2021, 03:20:42 pm

I just had a solar system installed on my 2002, 26.5 RK. I have 4-190 watt panels on the roof. The 3 Battle Born lithium batteries are stored in the outside compartment just forward of where the old battery box is. There is actually room for one more, but I've been told that would be overkill for my size rig. We stripped out the old battery box to install the new 2000 watt Magnum Inverter/Charger. The remote for the Inverter/Charger was accessed through the wardrobe and mounted on the wall above the furnace controls. The Victron MPPT controller was installed in the large cabinet area beneath the refrigerator.

Now one thing I have to be aware of is charging the lithium batteries if it gets too cold. I don't plan to, but if I wind up in area that is getting below freezing temperatures, then I plan to place a heating pad in the battery compartment, along with some type of insulation.

Hope this helps.

Re: Adding weight in one corner of RV - Solar install under Dinette?

Reply #2 – January 29, 2021, 04:20:41 pm

Some folks have installed extra batteries on racks welded to the frame. I have seen it done on a mid bath directly below the battery box. Simple task for a welder.

Re: Adding weight in one corner of RV - Solar install under Dinette?

Reply #3 – January 29, 2021, 08:18:46 pm

Larry Wade has added a under coach rack: Battery tray- new | Flickr

Chris

Re: Adding weight in one corner of RV - Solar install under Dinette?

Reply #4 – January 29, 2021, 09:12:09 pm

Rick, if you have not yet done so, get your rig weighed at all four corners. Adding weight on the right might better balance your rig. My battery bank (6 big AGM's plus my Magnum whole house inverter) is under my front dinette bench in my Midbath, so just behind the passenger seat. My side to side weighing shows that my left to right weights are nearly identical. Bear in mind that the weight you are talking about is equal to one passenger. I don't think it will matter much where you put your batteries in terms of ride and handling. If you were adding 500 pounds, the weight of my fresh water tank when full, you would be likely to feel that difference. But for 150 pounds, I wouldn't worry too much.

Temperature is another matter. I encourage keeping you batteries inside so their temperature is more uniform. While the cable runs may be longer, and while copper is expensive, you can always jump the wire gauge a step or two to make up for the distance. There are tables available on line that can help you with sizing the cables.

Ken F in NM

Re: Adding weight in one corner of RV - Solar install under Dinette?

Reply #5 – January 29, 2021, 09:16:55 pm

I would be hesitant to put the batteries back there.

The weight is about like a person sitting on the dinette, but it's still way out behind the rear axle and therefore on the end of a lever which would multiply the effects of the weight. The batteries could bounce around quite a bit while driving.

As you probably know, shorter wire runs are more efficient, all else being equal. In addition to getting solar and inverter wires to the back of the coach, you also need to work out something for the convertor wires. It might require a thicker gauge wire for the entire run.

I'd really try to get things between the two axles, preferably close to the fridge if you plan to use the fridge vent as a way to route wires from the roof to the coach.

Is there something wrong with putting the lithium batteries where the current batteries are? One big advantage of lithium is that you get about twice as much usable capacity from the same number of batteries. With lead acid (or AGM) batteries, you get ~50 amp hours of useable capacity from each (half of the rated amount). With lithium, you get closer to 100 each. You're essentially doubling your usable capacity while keeping the same number of batteries.

Rich

Re: Adding weight in one corner of RV - Solar install under Dinette?

Reply #6 – January 30, 2021, 05:46:51 am

Quote from: rich - January 29, 2021, 09:16:55 pm

I would be hesitant to put the batteries back there.

The weight is about like a person sitting on the dinette, but it's still way out behind the rear axle and therefore on the end of a lever which would multiply the effects of the weight. The batteries could bounce around quite a bit while driving.

As you probably know, shorter wire runs are more efficient, all else being equal. In addition to getting solar and inverter wires to the back of the coach, you also need to work out something for the convertor wires. It might require a thicker gauge wire for the entire run.

I'd really try to get things between the two axles, preferably close to the fridge if you plan to use the fridge vent as a way to route wires from the roof to the coach.

Is there something wrong with putting the lithium batteries where the current batteries are? One big advantage of lithium is that you get about twice as much usable capacity from the same number of batteries. With lead acid (or AGM) batteries, you get ~50 amp hours of useable capacity from each (half of the rated amount). With lithium, you get closer to 100 each. You're essentially doubling your usable capacity while keeping the same number of batteries.

Rich

Completely agree. Adding weight way behind the rear axle would add much more bouncing forces to the rear suspension and tires. This is especially true if one lives in upper Midwest where roads are pretty bad due to winter weather. The rear tires are already in a hostile environment due their close distances to the exhaust system.

The best location for heavy batteries is between the two axles. Shorter power cable runs will reduce parasitic loss, another benefit.

Re: Adding weight in one corner of RV - Solar install under Dinette?

Reply #7 – January 31, 2021, 01:00:17 am

Thanks for the input everyone! I live in Wisconsin so I would like to keep the batteries inside the RV (hopefully I won't have to be here too often when it's really cold). I'll figure something out!

Re: Adding weight in one corner of RV - Solar install under Dinette?

Reply #8 – January 31, 2021, 03:06:55 am

I agree with Rich, consider keeping the batteries in the Factory compartment. The battery compartment door can be insulated, sealed and the vents covered. Since lithiums do not need to sealed from the interior, drill large holes in the battery box to allow interior heat to reach the batteries, making cold-weather use more practical.
The lower, exterior compartments are more exposed to the elements and will be much colder in the winter than the battery compartment, especially after sealing and insulating.

Larry

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