Author Topic: Towed vehicle charging  (Read 6035 times)

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greenkarson

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Towed vehicle charging
« on: October 27, 2012, 06:30:04 AM »
Not sure if this is the appropriate category or not but I'm desperate.  My uncle a full time RVer is visiting for a couple days. He came to me with a problem. That I can't find a straight answer for anywhere online. Here's the problem they tow a late model gmc van behind there rv on a dolly.  With only the vans front wheels on the dolly. So the dolly has its own trailer lights.  But the vans ignition has to be on to keep the steering unlocked so it can turn properly. But after a few hours of driving the van battery goes dead. So he bought a little windshield solar panel (only 1.5watt) not knowing any better thinking that would work. It doesn't

So I was thinking since the dolly only uses the 4 pin trailer plug on the RV.  Why can't I make a nice cord to go from the constant power on his unused seven way plug with battery clips on the van end he can clip right onto the van battery. Or maybe get a little fancyer and put in a quick connect out through the van grill. But either way will this overcharge the battery?  Or will the rv voltage regulator take car of this?  For sure I'd put a inline fuse but what gauge wire do u guys think would be appropriate I was hoping to be able to use a nice piece of industrial extension cord. I can buy that local by the foot   But I think it's only 12gauge. Would this be enough since its only maintaining the battery not charging it from dead?

That's again you guys have been a big help many times in the past!!

bob g

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Re: Towed vehicle charging
« Reply #1 on: October 27, 2012, 09:33:18 AM »
i have never seen a front wheel toe dolly that required the steering to be unlocked, most require them to be locked once strapped down.

unless you are talking about a tow bar? wherein all of the towed vehicles tires are on the pavement?

if that is the case, i would use a battery disconnect on the towed vehicle, and an extension cord from the trailer to a set of magnetic lights for the back of the towed vehicle.  that way you could disconnect the battery and leave the key on, so it will steer, and extend the lights from the trailer to the rear of the towed vehicle

but then again, you mention lights on the back of the trailer? so there is no reason to have the steering unlocked!

hmmm

need more info on this one, something is not right at all.

bob g
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greenkarson

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Re: Towed vehicle charging
« Reply #2 on: October 27, 2012, 10:23:01 AM »
Actually on most dolly the part that the wheel strap too pivots so the van wheels don't have to. But this one the the deck the tires strap to does not pivot. So the van wheels have too. But that being said I'm not for sure. If it is the way I discribed would the cable to the van from the rv be ok in your opinion?
Thanks

dnix71

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Re: Towed vehicle charging
« Reply #3 on: October 27, 2012, 10:35:56 AM »
If you tow with the van front wheels locked, turning can pull the dolly wheel tie-down straps loose. That's why you leave the van wheels unlocked. Disconnect the negative battery terminal for long tows and connect the towing harness from the RV to the dolly.

If you need lights on the back of the van for legal reasons or night driving, buy a light bar and hook that up to the RV, too.
http://www.towmart.com/towmate-wireless-tm3l Wireless LED with rechargable battery. Put the pair whereever they need to be.

greenkarson

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Re: Towed vehicle charging
« Reply #4 on: October 27, 2012, 11:03:45 AM »
Don't need the lights just need the key on to unlock the steering. I don't really want to cut any van wires to put in a disconnect switch. I would if it was my own though. Undoing the connection is not really fesible either for them. So I was thinking the cable would be the way to go for now. Do you for see any issue electrically speaking?  If I use the rv power straight to the van battery?

Larsmartinxt

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Re: Towed vehicle charging
« Reply #5 on: October 27, 2012, 12:41:48 PM »
I don't see any problems with doing what you said. Make sure that the draw from the "dolly cable" doesn't fry the fuses for the taillights. (make sure that the battery of the van is fully charged when connecting to the RV)

birdhouse

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Re: Towed vehicle charging
« Reply #6 on: October 27, 2012, 01:07:32 PM »
i think what you're scheeming would probably work.  the rv plug is obviously strong enough to power light for about any type of trailer.  my only question is weather to leave the van battery in the loop or not. 

assuming the RV is a 12v system, while running it will be ~14.4v.  plug in a resting van with a battery of unknown age ~12.1-12.8??  and an inrush of current could go to the van, thus heating up wires/connections ect. 

if it were me, i'd temporarily take the van battery offline to take one more item out of the "what if" bucket, and run the vans electrical system directly off the RV trailer plug. i see no reason that this situation would give any grief.  some 12/2 SO cord would be good for atleast 20A, probably 30A if you went by a chassis wiring (short lengths) amp chart.  20A would yield a minimum of 240W.  with headlights off, that should be more than enough for the van rear lights. 

if the van is fuel injected, there may be a slight surge when the key is first turned on to build pressure behind the fuel injectors....  aka, the van thinks it's about to fire up, though it isn't. 

obviously make sure the heater blower/radio/ect is all turned off. 

good luck!

adam

Frank S

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Re: Towed vehicle charging
« Reply #7 on: October 27, 2012, 01:29:17 PM »
I still question the need for the steering to be unlocked'
 I've built several tow dollies. some with Akerman linkage steered axles, some with center pivot, both with and without brakes, and have seen 100's of others but I don't remember ever seeing one that was any good that needed the towed vehicles front wheels to turn. only tow bars need that feature
 Never tow a vehicle without tow lights at the rear you need stop and turn even in the day time.
 Many states now require inertia or electric brakes if the tow vehicle weighs over  certain percentage of the prime mover. the brakes are often required for any towed vehicle over a certain weight anyway. All dollies with brakes installed are required to have automatic break away.
 Towing a vehicle with the steering  un-bound can be dangerous as this allows a whip action  sway to set up
I live so far outside of the box, when I die they will stretch my carcass over the coffin

bob g

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Re: Towed vehicle charging
« Reply #8 on: October 27, 2012, 09:36:29 PM »
all i know is what i have rented from uhaul,
their units are center pivot with a set of straps that winch the front tires down so damn tight that there would be no way the steering is going to go even a silly millimeter.

i can think of no reason to have the steering unlocked!  there is no reason for it to be unlocked in any design that suspends the front tires off the pavement.

i question the legality of any design that would require the steering be unlocked!  that would tell me that there would be movement in the cradle, any movement would be strictly forbidden by the DOT in my opinion, as it would represent an unsecure load.

got a picture of this thing?

how is the vehicle secured to the tow dolley unit?

this sounds to me to be a carry over of the old tow bar arrangement wherein you must have the steering unlocked so the wheels will follow in a turn, of course that is with all wheels on the ground.

this is the first time i have ever heard of such a need,  and have never seen anything like you describe on the road.

bob g
research and development of a S195 changfa based trigenerator, modified
large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
www.microcogen.info and a SOMRAD member

greenkarson

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Re: Towed vehicle charging
« Reply #9 on: October 28, 2012, 07:12:19 AM »
On non a pivoting Dolly the towed vehicles steering must ABSOLUTLY be unlocked. (Google it).  My only question is about using the Rv to maintain the vans battery and any issues this could cause electrically

Thanks

thirteen

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Re: Towed vehicle charging
« Reply #10 on: October 28, 2012, 10:43:12 AM »
they might be able to talk with the dealer about an alternet way unlock the steering.13
MntMnROY 13

ghurd

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Re: Towed vehicle charging
« Reply #11 on: October 28, 2012, 04:53:37 PM »
I do not see any reason the van battery could not be connected to the RV system.

I had a small camper that's trailer road light system was connected to the house battery.
The idea was, I think, to keep the house battery charged while towing when the fridge was running on 12V.
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Frank S

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Re: Towed vehicle charging
« Reply #12 on: October 28, 2012, 06:03:59 PM »
I was thinking that most of the newer vehicles all you had to do was start the engine then just barely turn the switch until the engine went off but no to full lock position
I live so far outside of the box, when I die they will stretch my carcass over the coffin

bob g

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Re: Towed vehicle charging
« Reply #13 on: October 28, 2012, 06:33:41 PM »
geometrically there is no reason to run with the front wheel steering unlocked!

you drive the car up the ramps into the cradle and put the tie down straps over the front tires and lock it down tight. then you should also be putting on safety chains to the chassis of the car to the dolley.

there is absolutely no way for the wheels to turn once tied down and if they did you would have a non secure load, just ask a DOT inspector.

tow dolly's come in two versions, one is the center pivot platform type
much like a fifth wheel  or a converter dolly on a semi pup trailer the dolly wheels follow the draw bar around a corner while the car's nose stays more or less straight ahead.

the other version has steerable dolly wheels that use tie rods, this allows the car to be strapped down tight and the dolly wheels do the turning.

there is absolutely no way for the cars steering do do anything once strapped down in either version.

there is so much confusion out there when it comes to whether to lock or unlock the front steering of the towed vehicle, but if you draw up on paper what happens in a turn it becomes apparent very quickly that the towed cars steering has no play in what is happening, nor should you want it to.  if it were to play it would work the straps loose very quickly and something bad is going to happen.

if you need proof of concept just go strap down the car on the dolly, lock the steering wheel and take it out on a parking lot, make a hard  turn and see what happens, the straps won't work loose.

then unlock it and see what happens, the straps still won't work loose.

now drive forward straight and make a sharp left turn and stop mid turn
take a look at the front wheels and you will find they are still pointing straight forward, whether they are locked or not.

then take a look at the platform, and see if it swiveled as in type 1 above, if not then look to see if the dolly wheels are turning to follow the tow vehicle like type 2 above.

one of the two is going to happen.

but the towed vehicles tires will be pointed straight ahead.

bob g
research and development of a S195 changfa based trigenerator, modified
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bob g

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Re: Towed vehicle charging
« Reply #14 on: October 28, 2012, 06:56:24 PM »
here check this out

http://auto.howstuffworks.com/auto-parts/towing/equipment/accessories/tow-dollies3.htm

down about the end of the 3rd paragraph

or you can read a bit of the confusion here

http://forums.woodalls.com/index.cfm/fuseaction/thread/tid/24021206.cfm

a pdf from budget page 16 onward

https://www.budgettruck.com/Portals/0/Towability_Guide.pdf

from ehow.com
http://www.ehow.com/how_5844361_use-tow-dolley.html

bottom line you don't want the front wheels to move about at all, they will only loosen the straps and will do nothing for steering on a dolly anyway.

bob g
research and development of a S195 changfa based trigenerator, modified
large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
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greenkarson

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Re: Towed vehicle charging
« Reply #15 on: October 28, 2012, 07:32:06 PM »
Make that three types of dollies   swiveling deck, stearable axle, and fixed or non swiveling

Iv had experience with all three. with the first two kinds your right on.  the third non swiveling non stearing kind you drive on like normal then a harness fits over each front tire and gets tightened down so the wheels cant move at all on the dolly. but the car stearing is unlocked so the vehicle pivots instead of the dolly.  If the vehicles stearing is left locked when you make a sharp turn you would be dragging the dolly axle side ways.

Its not the best system by any means but its what he has.  If the rain ever stops i will try to take a picture of it before they leave.

I went ahead and made the cable to maintain the battery seams to work nice.

greenkarson

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Re: Towed vehicle charging
« Reply #16 on: October 28, 2012, 07:45:36 PM »
http://www.irv2.com/forums/f85/tow-dolly-steering-100828-2.html

Heres a link where they talk about them.  Looks like it may be a older stlye

bob g

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Re: Towed vehicle charging
« Reply #17 on: October 28, 2012, 09:52:21 PM »
green:
it really is of no consequence to me, so i will only address this



"Iv had experience with all three. with the first two kinds your right on.  the third non swiveling non stearing kind you drive on like normal then a harness fits over each front tire and gets tightened down so the wheels cant move at all on the dolly. but the car stearing is unlocked so the vehicle pivots instead of the dolly.  If the vehicles stearing is left locked when you make a sharp turn you would be dragging the dolly axle side ways.:"

if the wheels are strapped down to the dolley, and the dolley does not pivot in the center, or have a tie rod steering system built into the dolley, there is no way on earth for the cars steering to allow the unit to make a corner!  it cannot happen as described

the cars steering will not allow the car to bend around the corner,

the only way for this to possibly work, would be to make a very complex table system that not only would have two tables, one for each wheel but they both would have to swivel, and they would both have to traverse forward and backward on the dolly chassis.

when a car goes around a corner the inside steer tire only goes a very short distance, while the outer must travel a much larger distance. if you strap the wheels down to a common line (the cradles are inline with one another) this would preclude either wheel from traveling further than the other, they would have to travel the same distance no matter what because they are strapped down and the car does not bend in the middle.

you can try this if you like to prove my point, load the car on the dolley
turn the steering all the way to either the right or the left and lock it down there, then strap it down tight, and drive off straight. you will find the car will go just fine following the tow vehicle just fine. now make a left turn and it will turn just fine.

if you don't want to try that, just cut out a little cardboard T and put a model car on it, and then turn the end of the T, and see where the tires go.  allowing the tires to steer will not make a difference, the wheels will still move off the T, one forward and one backward, which depends on direction of the turn.

this whole leave the key on or unlock the steering is a throwback to the towbar days when you had to do so if all wheels are going to be on the ground.

anyway, this is all a sidebar i realize
as for charging the towed vehicle off the tow vehicle, you won't  overcharge the towed unit, if anything you will be undercharging it, or at best maintaining the charge, because of the voltage drop in the cord from the tow unit to the towed unit. 

many of the motorhomes use a lower set point regulator because the unit is going to be on the road over longer distances, not city start and stop generally, so... it is not uncommon to see a setpoint of 13.8 or so at the alternator, drop another volt in transmission via a 12gauge wire and you will be just about what it takes to keep from taking anything from the towed vehicle battery, not enough to do any real charging, but maybe enough to run the lights.

you would still need some means of stop, turn and hazard to the rear of the tow vehicle anyway, so i would think maybe instead of worrying about powering the tail lights off the towed vehicle battery, simply disconnect it if necessary and run a separate set of remote magnetic mount lights from the tow vehicle to the mount at the rear of the vehicle in tow.

sorry for the argument, 
i just don't want any part of propagating something that might end up getting someone hurt down the road. i am not saying it is the case here, but there might be others that read this and think it correct to unlock the steering when there is clear evidence to the contrary.

if that makes sense?

thanks
bob g
research and development of a S195 changfa based trigenerator, modified
large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
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halfcrazy

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Re: Towed vehicle charging
« Reply #18 on: October 29, 2012, 04:53:53 PM »
I say I can see no way that unlocked steering could help. Think about it if you go around a left hand corner and the dolly is fixed to the car and the right tire would have to physically slide back on the dolly or the left would have to slide forward. Draw this out and if you drove a car onto a fixed bed and physically lock the tires in place then bend the car and deck see what happens to the spacing fron to back on the tires they can not physically stay in the same spot front to back??

Ryan

bob g

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Re: Towed vehicle charging
« Reply #19 on: October 29, 2012, 10:45:27 PM »
Ryan,, you have it right
if the thing is strapped down tight, and there is no swivel center pivot platform or tie rod controlled steerable wheels on the dolly, all that can happen is grinding the tires off of the dolly as it is pulled around a corner.

now if the car's wheels were allowed to move back and forth, technically it could work, however you would not have a secure load any longer.  not unless there was a sliding saddle on each side that the tires are strapped into.  however that is such a complex design, i can see no reason why anyone would want to built it, it would be too expensive just to be different.

in my opinion the center pivot platform style is probably the simplest, and safest of the two designs.  only one major moving part and no issues with alignment with the dolly tires.

i am still trying to keep an open mind, however it is very hard to imagine any other design being practical and successful, let alone safe.

so until i see a picture of something that would require the wheels and the car to steer while being securely strapped down to any part of the dolley, i just ain't buyin into it.

a picture would sure be nice,  at this point i would love to be proven wrong, it's one way i learn things!

bob g
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large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
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greenkarson

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Re: Towed vehicle charging
« Reply #20 on: October 30, 2012, 06:08:50 AM »
I see what your saying about the wheels not steering. I never got back to see it before he hit the road again. So I phoned him to warn him about it. He said in the instruction book that cam with the dolly it stressed that steering had to be unlocked.

So I'm wondering if it has something to do with keeping pressure off the locking mechanism?

halfcrazy

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Re: Towed vehicle charging
« Reply #21 on: October 30, 2012, 06:46:09 AM »
Sounds scary to me..

southpaw

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Re: Towed vehicle charging
« Reply #22 on: October 30, 2012, 07:12:29 AM »
The only reason i could see a need for the Ignition to be unlocked would be if the van was rear wheel drive or all wheel drive
 the ignition would need to be unlocked to put the transmission in neutral.

Frank S

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Re: Towed vehicle charging
« Reply #23 on: October 30, 2012, 07:46:12 AM »
Southpaw you bring up another good point. there are a select few vehicles actually designed to be towed Nissan makes one Ford used to make one i'm talking about vehicles that have an automatic transmission that has a full disconnect system built in so the transmission is not trying to spin If he has a GM product only Cadillac used to have a model in their SUV lineup.
 Lincoln navigator used to boast being designed to trail behind a MTR Home
 Ugo and Hyundai had a towable model
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greenkarson

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Re: Towed vehicle charging
« Reply #24 on: October 30, 2012, 12:59:57 PM »
It is a awd drive van