Charging the trailer battery while towing
Steve S.
vehicle to allow it to recharge the trailer's battery while driving.
The Jayco manual and dealer state that you should wire up a constant
12V to one of the trailer harness pins (through a fuse). This seems
totally wrong to me (possibility of running the t.v.'s battery down if
you leave it plugged in and no maximum current control).
I'm thinking of setting something up where I use a relay to turn the
power on only when the tv's engine is running and also include some
sort of current limiter to around 30 A (or whatever the
connector/wires can handle).
What solutions have you seen/used?
Steve
the old anarchist
have is another battery hooked up to the tow vehicle. And unless you have
something running in the trailer, there won't be a draw to drain the
batteries.
the old anarchist
"Steve S." <Steve_...@hotmail.com> wrote in message
news:2b0c768f.03041...@posting.google.com...
Glenn Heslop
the brakeaway controler battery. Seems to work fine.
Glenn.
"Steve S." <Steve_...@hotmail.com> wrote in message
news:2b0c768f.03041...@posting.google.com...
Larry Nail
than the vehicle battery, they will equalize. Had it happen to me & went
back out after a stop for dinner & not enought juice to start. Granted this
happened after a weekend of dry camping so the trailer battery was
discharged quite a bit... In response to that incident, I put a heavy duty
relay in the circuit controlled by the ignition & never had a problem since.
BTW, this happened on my first dry camping adventure with my popup a month
ago...icle is not running, it will not be charging. All you will
jbr...@aros.net
for safety, and for peace of mind.
Its probably no big thing, but consider the adage 'if anything can go
wrong, it will, at the worst possible moment'
If one of them develop a weakened cell, that would lower the voltage on
both batteries, or the reverse, neither will fully charge.
If the house battery is a marine or a deep cycle, charging it from the car
alternator can damage it, so the above is certainly a possibilty. It is
also advisable to consider the method of charging a marine or deep cycle
battery, and you will shorten it life by holding it at the higher voltage
that the TV regulator will deliver. It is not always in the best interest
of the battery to let the voltage get that high. Better to fully charge
it, and disconnect it. If the battery is fully charged when you start out,
and you drive for 8 hours, that is a lot of abuse for a battery that
probably doesn't want to be pulled up over 14 volts, especially for a long
time. Car batteries are different from Marine/Deep Cycle one.
The wire is probably only about 14 awg and the house battery is sure to be
8 to 10 feet from the alternator. You won't pull more than maybe 6 or 8
amps through that without taking out the wire. Its a nice fuse, and if
there is any momentary short, that little wire is history. Not fatal, but
certainly a bummer.
Having a relay that you control is a nicer option for making sure
everything goes according to plan. That way you know that your house
battery will be safe, and can get you started if you need to use it.
John
Glenn Heslop
Glenn.
"Larry Nail" <ln...@attbi.com> wrote in message
news:Xaola.405421$L1.116355@sccrnsc02...
John Laughlin
with a 30A fuse. I think I used 12 gauge wire. The setup did not
work very well and I could not get a good charge. I soldered as many
connections as possible, but with each non-soldered connection and
with the wire run all the way back to the battery I suspect there was
significant voltage drop.
It took several hours to set up, since I had to run the wire myself.
In the end I was disappointed, so in my current tow vehicle I opted
against setting up a charge line. Instead, I bring along my charger
and top off my battery if needed.
John Laughlin (remove the x to e-mail).
2001 Starcraft 2406
2001 Astro
Larry Nail
"Glenn Heslop" <wiseid...@hotmail.com> wrote in message
news:39pla.696604$Yo4.60...@news1.calgary.shaw.ca...
Steve S.
without modifying the alternator (it's a single wire, internal
regulator). The best off the shelf product that I've found looks like
a battery separator such as Sure Powers.
http://www.surepower.com/Products/batsep.asp
I've also got a lot of people saying both the battery won't charge
well and others saying it will overcharge. I'm not sure if
overcharging is actually a problem, most of the people I've talked to
say the problem is it won't get enough charge.
I think it's still worth wiring up (even if it can't produce a full
charge), since it would be nice to operate the fridge off 12 V instead
of propane while towing.
Here's my current thinking:
- 4 gauge wire from tv battery to rear of car (already there with 60A
fuse for amplifier).
- Sure Power 1315 battery separator in trunk
- 30A auto resetting circuit breaker on line to trailer wiring
I figure this should:
- at least help charge the trailer battery when towing
- provide enough power to run the fridge
- stop a low battery at either end from discharging both (12.5V
cutoff)
- allow me to charge the tv battery from the trailer's power converter
if req'd
One flaw I see is if the trailer battery is flat, the circuit breaker
could keep cutting out and not let the battery start to charge. I'd
rather find some sort of current limiter as opposed to a breaker.
Steve
"Larry Nail" <ln...@attbi.com> wrote in message news:<aSqla.85957$ug3.1...@rwcrnsc51.ops.asp.att.net>...
jbr...@aros.net
>and others saying it will overcharge. I'm not sure if overcharging is
>actually a problem,
If you want the maximum life, and consistently max charges, you shouldn't
overcharge the battery. Undercharging simply gives you less reserve,
overcharging cuts into battery life and capacity. Its a trade off.
>I think it's still worth wiring up (even if it can't produce a full
>charge), since it would be nice to operate the fridge off 12 V instead of
>propane while towing.
Keeping it simple is always a factor.
>- stop a low battery at either end from discharging both (12.5V cutoff)
My god man! Are you inferring that the voltage level has anything to do
with the state of charge?? :-) Eeegads, flame war alert. Run for the
hills!!! Hide the flammable materials.
:-)
Good luck,
John
Gerry Pierce
the 20 or so ft run. I believe that 6 or 8 is what is needed, but have not
sat down to do the math. I am sure there are some engineers in here that can
spout off the correct size, but me, as a technician, would prefer to have
the largest wire possible going back there.
My previous TV, a ford E-150 came wired from the factory, don't know what
size the wire was, but it would not charge the battery effectively on the
short trips we were on, especially if the fridge was on.
Gerry
--
Gerry & Robyn
99 Mesa
01 Sporttrac
Jacksonville, FL
"John Laughlin" <jaxla...@columbus.rr.com> wrote in message
news:3e961e30.300949302@freud...
Dick
voltage regulated at about 14.5 volts at the tow vehicle battery it will
take hours to put much of a charge into the trailer.
The best you can expect is to be able to travel with a 12 volt refrigerator
on and not discharge the trailer battery.
To push more into the trailer battery you would have to trick your regulator
into putting out voltages like you can get from battery chargers.
Also remember the return is just as important as the 12 volt line. Most
vehicles use the frame. Anyway a 10 gauge wire is plenty good. It is 1.018
ohms per 1000 feet. About .02 ohms for 20 feet. At 10 amperes that would
result in about .2 volts drop. 8 gauge is .8 ohms/1000 which would give .16
volts drop.
If you use your batteries a lot the best is to get a small generator. I use
golf cart batteries and during heavy usage (cold weather when I use the
furnace a lot) run a small generator for about an hour each day. That gets
the batteries back up to about 90% state of charge. The last 10% would take
three or four more hours.
"Gerry Pierce" <Cruzr...@comcast.net> wrote in message
news:b793fb$c7dja$1...@ID-51206.news.dfncis.de...
Tom Shaw
with AWG 12 or AWG14 with 20 or 30 amp circuit breakers. I can see no way
that you would need AWG 6 or 8 to run from the tow vehicle to the pop up. I
think the answer lies in Dick's post...i.e. it is not the voltage drop which
is killing you.
TS
"Gerry Pierce" <Cruzr...@comcast.net> wrote in message
news:b793fb$c7dja$1...@ID-51206.news.dfncis.de...
Cass
Tom,
You are not realizing or understanding the relationship of voltage, current
and power with respect to wire size and length of run and resistance per
foot.
Cass
"Tom Shaw" <a000...@airmail.net> wrote in message
news:A1E9CA6D040D2AC7.94B73CE9...@lp.airnews.net...
Randy
> the 20 or so ft run. I believe that 6 or 8 is what is needed, but have not
> sat down to do the math. I am sure there are some engineers in here that can
> spout off the correct size, but me, as a technician, would prefer to have
> the largest wire possible going back there.
Generally speaking, if you're using stranded copper wire, the average
current handling capability is: (increase the gauge size to next
largest value if you think you are close to max current to avoid
voltage drop)
GAUGE MAX CURRENT/AMPS
14 15
12 20
10 30
8 40
6 65
Yes, there are variations depending on temperature and distance, but
these ratings should be good ballpark numbers to go by. I was just on
my way to the hardware store to get some wire because I neglected to
grab some at the office!
Randy
Dick
for 20 feet. Then if he is running his refrigerator which draws about 10
amperes he would not have much left over for charging. including the drop
in the return there could have be a half volt drop. Then what ever current
the battery would take would result in even more drop.
On the other hand tests I have done measuring current shows that even with
the full 14 volts back to the battery, it develops a surface charge rather
rapidly and the charge current then drops off.
In addition, the battery manufacturers do not recommend charging at high
currents. For long battery life 110 ampere hour Deep Discharge battery
should not be charged with currents greater than 11 amperes. If you could
somehow keep that much current going it would take over five hours to charge
a battery from 50% state of charge. No way can you charge or would you want
to charge a battery with short trips. For long battery life you should not
discharge below 50% state of charge.
To prevent sufation Deep Discharge batteries need higher charge voltages
than with standard automobile batteries. These voltages are higher than you
will ever get with a standard alternator.
"Tom Shaw" <a000...@airmail.net> wrote in message
news:A1E9CA6D040D2AC7.94B73CE9...@lp.airnews.net...
Randy
There is also a difference between the conductivity of your house
wiring compared with vehicle wiring. Most vehicle wiring is stranded,
house wiring is solid. This will have an affect on the current and
voltage characteristics, so comparing the two are not necessarily
accurate.
Randy
"Tom Shaw" wrote in message
Randy
jbr...@aros.net
>I do not understand the deal here about the wire size. Your house is
>wired with AWG 12 or AWG14 with 20 or 30 amp circuit breakers. I can see
>no way that you would need AWG 6 or 8 to run from the tow vehicle to the
>pop up.
You won't be able to push 10 amps at 12 volts through a 14 gauge wire for
any significant amount of distance. There are enough tables in the library
and on the web to show the max wire lengths required for defined amounts
of current and voltage. If only you were right, then I could have saved a
fortune wiring the solar panels to the batteries with house wire :-) Plus
that 2 guage stuff is hard to bend!
To oversimplify:
Ohms law explains that current is equal to the voltage divided by the
resistance.
I=E/R
If you want 10 amps to the battery, look how the R changes if you use 120V
instead of 12V.
10 =120/12 if you are wiring your house. The total resistance in the ckt
can be 12 ohms.
10=12/1.2 if you are wiring your trailer. The total resistance in the ckt
can only be 1.2 ohms. To paraphrase the police chief in Jaws, 'you're
gonna need a bigger wire.' :)
There is a reason why the power companies boost the voltage in order to
transmit it long distances. (there are other reasons too, but good luck
building towers to support 00 awg wires <g>)
>I think the answer lies in Dick's post...i.e. it is not the >voltage
drop which is killing you.
It is likely the voltage drop, mixed with the expectation that one can
recharge a 110A battery that is at 50%, in a matter of a few hours.
The proof is in the seeing, so grab a meter and measure the current in,
and the voltage at, the battery, in a discharged state, with the engine
running and see if you have the numbers needed to recharge that thing. The
numbers are defined by the type of battery, its capacity, and the state of
charge.
HTH,
John
the old anarchist
are DC. You need some transformers to step up the volt or it does drop. What
you may want to do? Why not just a pair of 30 dollar jumper cables? Just
once a day in the morning, pull the TV up, put the cables on and run it for
20 to 30 minutes.
the old anarchist
"Randy" <km...@arrl.net> wrote in message
news:137ded44.03041...@posting.google.com...
Marc
regaurd to wiring capacities. Also will give
the proper techniques required to make a solid long term electrical connection
that can withstand more aggressive conditions. ( if it can survive the salt
water marine enviorment - it can survive in the camper).
The voltage itself plays a big role on determining what the overall voltage
drop is for a giving wire gauge size, with a given length, with a given load on
it.
For a given wire size, load, length, the voltage drop is far more pronounced at
a lower voltage say 12v vs 120v.
Just the load on the electric fridge is enough to drop the availavle voltage on
the 'charge wire' to a point where it's not sufficiant to effectively charge
the camper battery.
Dick
solid wire. I think what some of you might not be taking into account is
that your house wiring is 120 volts.
When you put 20 amperes through a length of wire you get the same drop
regardless of the voltage. If you get a 2 or 3 volt drop on the 120 it is
not too noticable but a disaster on a 12 volt system.
"Randy" <km...@arrl.net> wrote in message
news:137ded44.03041...@posting.google.com...
Cass
Anarchist, if you don't understand electricity, why tell others stuff that
just isn't true? You do others a disservice as they go off with incorrect
info.
A.c. is no better at distribution than d.c. Also, you cannot step up d.c.
with transformer/s.
Now, power companies use a.c. since it CAN be stepped up with transformers
and there are other more in-depth technical reasons.
The best way to charge the trailer battery without having to worry with
diodes, isolators, etc., is to simply use a relay that is energized when the
ignition is on and use HEAVY cable.
Cass
"the old anarchist" <shawves...@comcast.net> wrote in message
news:W7GcnQDdE8I...@comcast.com...
John Laughlin
The 12v line to the fridge is totally separate from the rest of the
camper wiring. Some brought this up as a possible explanation for
lack of power, but for my camper it does not apply.
I thought one of the original reasons why Edison's DC power
distribution scheme lost to AC was the advantage AC had to transfer
power over longer distances....
One possibility that I've considered but never tried is to use an
inverter (I have a 300W) to power my charger, and then hook the
charger up to the battery while I tow. Never tried it, but maybe it
could work. I guess the worst that could happen is that I could blow
a fuse.
When I'm desperate for power I just find an outlet somewhere on the
campground and plug in my charger for a while. We usually like
camping sites that don't have electricity. These sites are usually
quieter and there's more selection because most people opt for the
electric sites.
Dick
> My camper is set up with separate wires for battery charge and fridge.
> The 12v line to the fridge is totally separate from the rest of the
> camper wiring. Some brought this up as a possible explanation for
> lack of power, but for my camper it does not apply.
>
> I thought one of the original reasons why Edison's DC power
> distribution scheme lost to AC was the advantage AC had to transfer
> power over longer distances....
very high voltages. Then when it gets near your house it goes through
another tansformer to bring it back to 120 volts.
However, DC is not totally dead. There are sevearal high voltage lines
around the world. One, called the Pacific DC Intertie, runs from
Washington State to Los Angeles. The voltage is near 1 million volts. The
advantage of DC is that there is not as much loss due to what is called
inductive coupling. You might think of it kind of like a transformer
coupling to ground. There are big expensive conversion stations at each end
of the line.
>
> One possibility that I've considered but never tried is to use an
> inverter (I have a 300W) to power my charger, and then hook the
> charger up to the battery while I tow. Never tried it, but maybe it
> could work. I guess the worst that could happen is that I could blow
> a fuse.
Some do exactly that. It does give better charge voltages than you get from
alternators.
jbr...@aros.net
>I thought one of the original reasons why Edison's DC power
>distribution scheme lost to AC was the advantage AC had to transfer power
>over longer distances....
Edison vs Tesla. Politics, financial influence, good luck, bad luck and
even some science thrown in to make it interesting. What a story, huh?
>One possibility that I've considered but never tried is to use an
>inverter (I have a 300W) to power my charger, and then hook the charger
>up to the battery while I tow. Never tried it, but maybe it could work.
>I guess the worst that could happen is that I could blow a fuse.
This is a better method than just running an highly uncontrolled 12V from
the alternator into a battery. Just make sure to keep the charge rate low
enough that you don't overload the whole TV electrical system. Besides,
shoving more than 10 amps into the battery just shortens it life and
capacity anyway.
John
John Laughlin
>
>>I thought one of the original reasons why Edison's DC power
>>distribution scheme lost to AC was the advantage AC had to transfer power
>>over longer distances....
>
>Edison vs Tesla. Politics, financial influence, good luck, bad luck and
>even some science thrown in to make it interesting. What a story, huh?
Thanks (and thanks to Dick too). Another tidbit I remember is that at
one time Edison tried to discredit AC as dangerous by supporting its
use in capital punishment. Not sure if my memory is correct, though.
>>One possibility that I've considered but never tried is to use an
>>inverter (I have a 300W) to power my charger, and then hook the charger
>>up to the battery while I tow. Never tried it, but maybe it could work.
>>I guess the worst that could happen is that I could blow a fuse.
>
>This is a better method than just running an highly uncontrolled 12V from
>the alternator into a battery. Just make sure to keep the charge rate low
>enough that you don't overload the whole TV electrical system. Besides,
>shoving more than 10 amps into the battery just shortens it life and
>capacity anyway.
Great! My charger can be adjusted to three different current levels
(2, 10, and 20A) so I think I may try this on a long trip sometime.
There's a plug in the back of the van where I can power the inverter.
Tom Shaw
very high AC transmission line voltages were prohibitive. Insulators for
120VDA are smaller than those needed for 120VAC since the peak voltage in
the AC case is 1.414 x 120, nearly 170 volts.
TS
"Dick" <hrli...@att.net> wrote in message
news:u4pma.59262$ja4.3...@bgtnsc05-news.ops.worldnet.att.net...
Tom Shaw
wonderful Lionel electric train. Guess what? House current in that neighbor
hood was DC and I guess they didn't sell anything to fix the problem so I
never did get to run that train. :-(.
TSnews:3e9aa76e.598227275@freud...
Cass
How prohibitive in cost were the insulators and at what point did they
become so?
Have you ever seen or heard of an insulator that is fine for 120 vdc but not
for 170 v.a.c.?
Cass
"Tom Shaw" <a000...@airmail.net> wrote in message
news:36F2925CF64DD633.EE0CDADE...@lp.airnews.net...
Dale Farmer
about power transmission lines, tens or hundreds of KVA are the norm,
and the difference up in that area are really large.
--Dale
Steve Silverwood
shawves...@comcast.net says...
> If the tow vehicle is not running, it will not be charging. All you will
> have is another battery hooked up to the tow vehicle. And unless you have
> something running in the trailer, there won't be a draw to drain the
> batteries.
True. And we found out the hard way that there was something running
all the time in the trailer as long as power was applied. It was the
propane detector, I think. The drain was small, but we found that the
battery was completely flat after a few months' storage. Pulling that
fuse out of the battery line was all that was required in order to
preserve the charge. There's also a charging circuit in the trailer so
that whenever we are on external AC power there's a charge going to the
battery, so I just plug the trailer in to the power in the garage a
couple of weeks before the first trip of the season, and we're good to
go.
--
-- //Steve//
Steve Silverwood, KB6OJS
Fountain Valley, CA
'97 Voyager minivan towing '96 Jayco 8' Eagle tent trailer
Email: kb6...@arrl.net
Web: http://home.earthlink.net/~kb6ojs_steve