Relocating Batteries

[ScottK]

I am considering relocating my pair of Costco Golf Cart Batteries from the tongue, to the rear of the camper under the bunk area.

I'm just in the exploration phase of this idea and I still need to get the camper fully loaded and off to the scales before I decide, but I have a strong suspicion that I will want to reduce my tongue weight if I want to put anything in the back of the truck.

I weighed the tongue (I have a Sherline scale) with the camper pretty much empty, with the standard WD system still on, 1 full propane tank, 2 batteries on the tongue, & empty water tanks, I was at 1000. I didn't go to the scales yet to weigh the camper. I would like to see the fully loaded tongue sitting around 900-1100 or 12%-14% of my goal fully loaded traveling weight of 7500-8000lbs With the front pass through storage, all the bedroom storage, another full propane tank and the Hensley, I think it will be very easy to creep up around 1300-1400 or maybe even more.

I suspect moving 100-120# of batteries off the tongue to the back would put me right where I need to be. Again, we'll see how it all works out when I finish up cleaning and maintenance items and get it loaded and weighed, but I'll be surprised if I don't find myself wanting to reduce the tongue weight.

So I would obviously need to put the batteries in a sealed, secured and vented battery box - no problem. The new battery location would be located right next to the charger/converter, so wiring would be very convenient. I also have a 140w solar panel (that I built) that I will be installing and this new battery location would make easier to wire up, as well. I'll make a separate post on the solar module build another time, but I included a few pics just for fun.

Question: Is rewiring the batteries in a new location, as simple as I think it is? Battery negative bonded to the frame and Battery Positive to the 2nd lug of on the charger/converter circuit board (see picture)? I would also add a battery disconnect near the new battery location, like we have up front. It seems to me I should leave all the existing wiring to the front, in tact, as to easily return to the original setup if desired and to keep power to the front junction box. Is there something I am forgetting to consider here?

[ScottK]

Just found something very interesting. I had been measuring the tongue weight at the jack. The Shurline manual says this is close enough. Today as I was playing around with weight and moving the batteries around, I thought I would try measuring right at the actual tongue instead of the jack. Wow! The difference between the weight at the jack and the weight at the actual tongue is 200 pounds different! 1000lbs at the jack and 800 at the ball. When I move the batteries to the back of the camper the weights change to 800 at the jack and 600 at the tongue.

Surely I was doing something wrong. I checked & double checked about 4 times in several ways and I keep getting the same readings. Considering the Hensley Arrow hitch adds about another 12" of length to the tongue and maybe another 100lbs, so I will be very curious to see what the true tongue weight will be once the Hensley is installed. So many factors in play, but it's looking much less likely that I will need/want to move the batteries, to the back. We'll see...

[mainah]

It's all about the leverage and the balance point! ! As far as your wiring I would leave it in place but not use it a voltage drop at 12 volts is a big one so use the larges possible wire you can and the shortest run.

[ScottK]

Has anyone else measured weights at both the jack and the actual tongue? If so I'd be interested in your results.

[JohnB]

Scott, your 200# seems off.

Give me these numbers and I can confirm what the weight change between the tongue jack to the ball coupler is.

1. Distance from the center of front axle on TT to the center of the ball coupler

2. Distance from the center of the ball coupler to the center of the tongue jack.

To get the front axle to the ball coupler, you can plumb bob down at the coupler center to the ground and then tape measure straight down the center of the camper to the front axle and plumb bob down there too. If you are within 1/4" to 3/8" on this long a dimension it will be "good enough". The ball center to the tongue jack try to get better than 1/4". Within 1/8" to 1/16" is good enough

I'll do the calc's on your distance and then we can figure out what may be going on. I have a Sherline too and you have to watch you are not putting it in a bind by accident. Need to do 3 setups and have the same number repeat to have higher confidence the number is good. It does not take much to put it in a bind.

John

[jim44646]

By moving batteries inside have you gave any consideration to venting. Batteries give off hydrogen gases which can be explosive.

[ScottK]

Originally Posted by JohnB

Scott, your 200# seems off.

Give me these numbers and I can confirm what the weight change between the tongue jack to the ball coupler is.

1. Distance from the center of front axle on TT to the center of the ball coupler

2. Distance from the center of the ball coupler to the center of the tongue jack.

John

1. 202-3/4" (+/- 1/8") (double plumb bob method as suggested)

2. 9-1/2" (+/- 1/16") (plumb bob to middle of jack)

I repeated the measurements several times with various blocks and posts making sure I wasn't binding. I bled the scale and even talked to the owner of the company. He agreed with you and I that the variation seemed too much. Just not sure what is going on. One thing I realized this morning, that could be a factor, is that the slide was out. Not sure how that would effect this, but I suppose it could.

[JohnB]

Originally Posted by ScottK

One thing I realized this morning, that could be a factor, is that the slide was out. Not sure how that would effect this, but I suppose it could.

Scott, I'm running the numbers now and saw you where on. YES, the slide being out will change the tongue weight. The slide being out will change the center of gravity of the camper. Basically there are only 5 points supporting the camper from the ground. (known as force reactions)

The 4 tires and the 1 tongue or jack post. When the slide is in and the stabilizers up, the camper level, then those 5 places have a certain load on them being supported by the ground. When the slide is out, the camper tips and shifts weight. Some of the 5 points loose weight, others gain weight, all 5 still add up to the same weight but the split is different.

Location of the slide makes a difference too on how much effect occurs.

Be back soon

John

[JohnB]

Originally Posted by ScottK

1. 202-3/4" (+/- 1/8") (double plumb bob method as suggested) Center of ball to center of TT front axle

2. 9-1/2" (+/- 1/16") (plumb bob to middle of jack) Center of ball to center of tongue jack.

Using those figure it goes like this.

Subtracting 202.75 - 9.5 = 193.25" for the distance the jack post is from the front axle. Summating moments about the front axle:

0 = 193.25 (1#) - 202.75(X) Solve of X

193.25/202.75 = 0.953 OR

For every 1# of weight at the tongue jack, there will only be 0.953# of weight at the tow ball when you lift the tongue jack and support by the ball.

Substituting some figures in for this: Using 1,000# weight at the tongue jack what is it at the tow ball on your camper?

1,000# at the jack x 0.953 = 953# at the tow ball. Or it is 47 #'s less at the ball than the jack post.

Your 200# does not work to explain any of this. There is something else shifting ~ 150# more weight.

Explain more about the slide and when you took what set of numbers to get this 200# difference.

Hope this helps

John

[ScottK]

Thanks John. I'll try weighing again with the slide in tomorrow. The slide was out when I did all my measurements, so I would think it should still be a 95.3% difference, but let's try it and make sure.

Thanks for the explanation on the math as well.

[JohnB]

I looked up your floor plan. The slide is over the axles. I "think" the 2 left side tires are about at, the front axle is under the rear dinette seat and the rear axle is under the front part of the sofa.

The slide being that far from the tongue will make a good difference being out or in when determining real tongue weight that will be seen by the truck when towing.

If both weights where 200# apart and both with the slide out, well h'mm. I'll have to think about that one. With the slide out the left side of the camper is getting a lot heavier, the right a lot lighter and the tongue area will it will depend on how much weight is fore or aft on the slide from the axles. That is not that simple to pre-calculate as we have no idea what the slide it self weighs and then the rest of the camper.

Ah yup, bring the slide in, try again and report back.

[ScottK]

I must have been really precise and consistently INaccurate in my first attempt at measuring the tongue in the 2 places. Must have been binding. Last time I chose not to use the center pin on the scale because it wouldn't reach all the way up inside the coupler. This time I used the center pin but only threaded it half way so it would reach. For consistency I used the center pin under the jack too. Measured as expected...950 at the coupler and 1000 at the jack (at least 3-4 measurements in each location). And there's the 95%! Whew! Just for fun, I put the slide out and measured it again. No noticeable change.

Ok, so now the Hensley Hitch extends the overall length of the tongue by about 12" I think. But weights about 150#. So do you suppose that will reduce or increase my tongue weight?

I realize the true number will be earned when I go to the scales and weigh the truck with and without the camper...but I lie in bed at night thinking about these things.

[JohnB]

Scott, thanks for reporting back. Good to know I have not lost it on doing the hand calc's. It's good to do it to not loose it... That is the down side of all the new high end software, click a few key and, there it is.

The Hensley and tongue weight, there has been a lot of discussion by some if it adds to camper TW or not.

Here are my thoughts.

The HA (Hensley Arrow) is supported by the truck through the shank. This is the same as a standard WD hitch head on the shank.

The weight of the HA will add more weight to the TV, rear axle and the TV GVW. Here that heavy weight hanging off the back of the truck can have an impact of the truck rear axle carrying capacity. You are for sure going to see that weight show up on the RA.

So is the HA considered part of camper TW? Well the parts of the hitch that mount the A frame and hangs from those mounts are part of TW.

The parts of the HA that are supported on the shank are part of the truck, just like a normal WD hitch head, just in this case the HA weighs a lot more than the standard WD head

When you tighten up the WD bars on the HA, it transfers weight off the TV rear axle like the conventional WD hitch, just it has more weight to transfer as it weighs more.

So folks might say the HA adds TW which is partly true. The point is the truck rear axle has to deal with that weight of the HA regardless if it is considered part of TW or TV weight aft of the rear axle.

When people go the truck scale with a HA, when they go to get a truck weight, often they they unhook the hitch box and have the stinger in the truck and leave the beast of the hitch head on the TT. In this case they are not getting an exact true truck weight or camper weight as they left part of the heavier hitch on the camper.

On a conventional WD hitch, the shank and the head stay with the truck and not left coupled to the camper.

The general reason that they do the 2 different is it is such a bear to unhook the HA at the coupler and leave it hang in the truck receiver like they do with standard WD hitch.

Hope this helps

John

[ScottK]

After a trip to the scales right after a camping trip with all the stuff/people still in the truck/camper, and made 5 passes through the scale to compare how the numbers changes with the batteries on the tongue and the batteries in the back, I decided it was the right move for me. I really wanted to make sure I had a solid handle on the numbers as I didn't want to end up with too little tongue weight as that can be very bad.

So I moved the batteries to their new home in the rear of the camper. They are in a sealed plywood box. The access panel has rubber weather stripping all around. I added a vent through the back of the camper using the same vent and hose used on the vented battery boxes. The line to the batteries is 6 gauge with a 60amp fuse and a new disconnect. Plenty of extra cable so I pull the bank out of the box to for maintenance.

While I was at it, I added a cheap 1200watt inverter with remote panel which i mounted up above the fridge, and a switched volt meter mounted in the same area. 4 gauge wire for the inverter from the battery.

We're now on the road for a month and everything is working great so far! Very happy with the results and given the proximity to the electrical service panel it was quite simple to make the connections.

Hole saw for the vent.





New location


Enough wire so batteries can slide out easily for maintenance and removal.


Fuses added








Added 1200w inverter and hid it next to the service panel. Added access door.




Outlets for inverter and switched voltmeter. I tied the voltmeter in at the lugs for the inverter.