Charging while towing

Anything electric, AC or DC

Re: Charging while towing

Postby capnTelescope » Wed Sep 25, 2013 11:17 am

@KennethW, :idea: or if the TV has front Daytime Running Lights (DRLs), which don't necessarily turn on the tail lights, you have an automatic on/off source at the headlights. This would be useful for almost any Charge While Towing scheme. Again this is newer vehicles, and not even all newer vehicles.

I think the DRL headlights are an even better solution as the wires are much easier to find and get to. Thanks for the idea, Kenneth.

We need some sort of light bulb smiley for "you gave me an :idea:".
I'll burn that bridge when I come to it.

Brad
ImageImage

My Build
User avatar
capnTelescope
Lifetime member
 
Posts: 1094
Images: 360
Joined: Sun Jun 27, 2004 3:44 pm
Location: Round Rock, TX

Re: Charging while towing

Postby ntsqd » Mon Sep 30, 2013 12:02 pm

While being a viable solution, the inverter > charger method is terribly inefficient. Whole lot of power losses going there that really don't need to happen for the TV to charge a camper/TD battery. I do not think that this is a good idea or a good solution, just one that does happen to work.

Much is made of not hooking different battery chemistries together. The regulator for the TV's alternator isn't that smart. It doesn't know what kind of battery or batteries it is connected to, and more importantly it can't change it's charging settings if it did. In short, they're pretty stupid. Since the alternator is the highest voltage source in the system (unless you have unregulated solar) it rules the system when everything is connected and the TV's engine is running. Once the TV's engine is not running and the alt is not charging those different chemistry batteries do need to be separated.

IMHO not enough concern/care/thought is given to voltage drop. There just isn't enough voltage delta available to carelessly give away any of it.
thom

Where does that road go?
ntsqd
Teardrop Builder
 
Posts: 26
Joined: Mon Sep 21, 2009 2:09 pm
Location: So. CA

Re: Charging while towing

Postby dean_petley » Sun Dec 22, 2013 6:46 am

i worked in a camping store for a few years and always got dragged out of the shop to see if products will fit in peoples set ups from push bikes to huge ex army equipment one of the best iders i ever seen was a trailer that had extra battery's but the charging was inboard instead of the normal free spinning wheels / hubs he ran a differential

and had the the input flange connected to an alternator that was mounted underneath and that charged his battery's i think he sayed he was photographer and he used a lot of power and this was the simplest way to charge as he went with out having to think
have funn
dean_petley
Teardrop Builder
 
Posts: 47
Joined: Tue Jul 09, 2013 7:32 am
Location: Sydney AUS
Top

Re: Charging while towing

Postby ntsqd » Sun Dec 22, 2013 2:01 pm

Interesting that this thread should pop back up. I just recently stumbled onto this connector pair:
http://www.delcity.net/store/Single-Pol ... ors/p_8595
It's 300A rating is overkill, but at least then you can use a wire gauge large enough to avoid any voltage drop.

I've been toying with putting a battery back on our TrailBlazer (took them off when the then Optima's were DOA) and have been pondering a charging method. I think that I'll move the single sensing VSR from the pop-top camper to the trailer and put a dual sensing VSR in the camper. That way the solar about to go on the camper will also charge the truck's batteries once the camper batteries are full. With the single sense VSR on the trailer I just need to supply it with wire from the alternator and I can do that by tapping into the camper's charge wire via the above plug and receptacle.
thom

Where does that road go?
ntsqd
Teardrop Builder
 
Posts: 26
Joined: Mon Sep 21, 2009 2:09 pm
Location: So. CA
Top

Re: Charging while towing

Postby capnTelescope » Sun Dec 22, 2013 2:42 pm

@ntsqd -- If that one's not big enough, you really need to rethink :thinking: just how much juice you think you need. Or build your tear on the back of a mobile welder. :)

@ Dean -- Your photog friend's setup is pretty ingenious, but I bet it really impacts gas mileage. Something like the 4WD penalty you pay whether you use 4WD or not.

Some of us, and I'm only speaking for myself, wisht we could build a tear that's ultra light, has enough juice on board to light up a small town, and able to pump enough water to put out a forest fire. For cheap. You just gotta set your priorities.

:lightbulb: I don't think anyone in this thread has proposed running a small gas generator in your tear while towing. (Tongue mostly in cheek.)

It would look something like this: :vroom: :cigar:
I'll burn that bridge when I come to it.

Brad
ImageImage

My Build
User avatar
capnTelescope
Lifetime member
 
Posts: 1094
Images: 360
Joined: Sun Jun 27, 2004 3:44 pm
Location: Round Rock, TX
Top

Re: Charging while towing

Postby capnTelescope » Sun Dec 22, 2013 3:13 pm

ntsqd wrote:I've been toying with putting a battery back on our TrailBlazer (took them off when the then Optima's were DOA) and have been pondering a charging method.


Battery-inverter-charger-battery2 works. See above. :thumbsup:

Any opinion what caused the Optimas to die young?
I'll burn that bridge when I come to it.

Brad
ImageImage

My Build
User avatar
capnTelescope
Lifetime member
 
Posts: 1094
Images: 360
Joined: Sun Jun 27, 2004 3:44 pm
Location: Round Rock, TX
Top

Re: Charging while towing

Postby GuitarPhotog » Sun Dec 22, 2013 4:09 pm

capnTelescope wrote:
ntsqd wrote:I've been toying with putting a battery back on our TrailBlazer (took them off when the then Optima's were DOA) and have been pondering a charging method.


Battery-inverter-charger-battery2 works. See above. :thumbsup:



But it is less efficient than tow vehicle generator -> battery1 -> battery2. Why give away 15-20% of your energy just for convenience and a couple of connectors?

<Chas>
:beer:
GuitarPhotog
Silver Donating Member
 
Posts: 1665
Images: 55
Joined: Tue Feb 08, 2011 12:52 pm
Location: Grants Pass Oregon
Top

Re: Charging while towing

Postby ntsqd » Sun Dec 22, 2013 5:43 pm

The point of the large charging cable & connector isn't high current, it is for the low voltage drop that a large conductor will have at relatively low ampacities. See my post on the previous page.

My cheap 150W inverter pulls almost 20A. That is a ~20% loss right there. I agree that stepping up the voltage is a good way to transmit electrical power over a distance (power companies live by this), but the DC > AC and then AC > DC conversion losses are unacceptable to me. Expensive technology can reduce those losses, but there are other, more economical methods.

The Optima's didn't die young. They were dead and unrecoverable when we got the trailer, but had been on the trailer without much maint. for nearly 7 years. Infrequent charging and no solar on board killed them.
thom

Where does that road go?
ntsqd
Teardrop Builder
 
Posts: 26
Joined: Mon Sep 21, 2009 2:09 pm
Location: So. CA
Top

Re: Charging while towing

Postby eamarquardt » Sun Dec 22, 2013 11:32 pm

E=IR. What this means is that the more current that is flowing the higher the voltage drop will be. When you first start to charge a discharged battery there will be significant current flow and the voltage drop will also be significant. However, as the battery voltage climbs the current will drop, and with it, the voltage drop will drop. So depending upon how long you drive it may or may not make much of a difference on how high your battery will get charged when using a wire that is, to one degree or another, undersized.

If you start out with 12 gauge wire, a twenty foot run, nominal voltage of 12 volts, and 20 amp current you get a voltage drop of 1.27 volts, 10.58%, and end up with 10.73 volts. That is significant.

I've never seen a battery take that much current for more than a few moments when connected to any battery charger I've ever had.

If you get the battery charged up a bit and the current drops down to one amp the voltage drop drops to 0.064 volts, 0.53%, and you end up with 11.936 volts. Hardly what one would consider significant.

The voltage drop for a 16 gauge conductor running 12 volts at one amp for twenty feet at one amp is .16 volts, 1.33%, and you end up with 11.84 volts. Again, IMHO, an insignificant voltage drop.

See: http://www.calculator.net/voltage-drop- ... &x=64&y=14

It's kinda like the wire is a voltage regulator which will allow the charging voltage to climb as the battery becomes more and more charged. Yup an undersized wire may slow things down a bit but I don't think the effect is nearly as important as some folks do. As as the battery voltage increases the charging current is gonna drop more because of the batteries state of charge and the maximum voltage of your tow vehicle's alternator/regulator than because of the voltage drop in the wires used to charge the battery.

You gotta remember that the battery in your tow vehicle doesn't normally require a lot of voltage to drive a high charging current because is isn't designed to be discharged more than small amount when starting the engine. My vehicles usually start with about one second of cranking time. If you assume yer starter draws 200 amps that works out to be 0.055 amp hours. That means at even one amp your battery will require about three minutes to replace the juice you used to start the car. Yup you have a 60, 80, 120, or whatever amp alternator but that current is never directed at the battery but to the electrical loads of your vehicle. The current the battery receives is typically a small fraction of your alternator's capacity even when the battery voltage is really low.

I kinda think one ought to have a good quality dedicated 120 volt charger for one's trailer. When you leave home your battery ought to be fully charged. Relying on your tow vehicle as your only means of charging when camping seems a bit inefficient and less than optimum to me. Better to have some method of charging your battery properly over the course of the day (not exceeding a current that is 10% of your battery's amp hour capacity). The best alternatives, IMHO, are shore power and solar power. A generator or tow vehicle will require a lot more run time than is, again IMHO, cost effective, convenient, and easy on the ears.

Just my two scents.

Cheers,

Gus
The opinions in this post are my own. My comments are directed to those that might like an alternative approach to those already espoused.There is the right way,the wrong way,the USMC way, your way, my way, and the highway.
"I'm impatient with stupidity. My people have learned to live without it." Klaatu-"The Day the Earth Stood Still"
"You can't handle the truth!"-Jack Nicholson "A Few Good Men"
"Some people spend an entire lifetime wondering if they made a difference in the world. The Marines don't have that problem"-Ronald Reagan
User avatar
eamarquardt
Silver Donating Member
 
Posts: 3179
Images: 150
Joined: Sat Nov 11, 2006 11:00 pm
Location: Simi Valley, State of Euphoria (Ca)
Top

Re: Charging while towing

Postby capnTelescope » Sun Dec 22, 2013 11:39 pm

Hi, GuitarPhotog and ntsqd. Yes, the Battery-*nverTer-CHarger-batterY2 (follow the caps) method is inefficient. But what are we doing here? Having an efficiency contest? If we are, I lose. I just want to charge my battery. AND I want to charge my $150 AGM deep cycle battery the way it wants to be charged, not by any old way to throw some watts back into it. It ain't what it used to be, but $150 is still a goodly chunk of change in my book. I want to take care of my expensive battery. Also the semi-expensive hunnert-buck TV battery, too.

There are a couple of convenience considerations here. One is the convenience of not having to remember to disconnect or turn something off when I turn off the TV. The second is the convenience of having the charger on board to plug in at a powered campsite or at home between trips, to give the Tear battery a nice big drink of electrons. Since I am going to have my charger on board anyway, I might as well use it while I'm driving.

So We're all working to the same end, but with different goals along the way.

The B*TCHY method works, (which is important) and works best for someone who's traveling all day and camping for the night before moving on. For a long-term boondocker who wants to throw some quick juice into the battery, the B2B method is just fine.

Important points I've learned about battery charging are: 1. Don't parallel batteries of different sizes/types/chemistries/ages/etc. So, for instance, it's fine to parallel two of the same batteries in your Diesel pick-up. It's even standard equipment on some makes. Otherwise, battery isolation is necessary to prevent over/under charging. 2. The average factory charging system on cars and light trucks is best suited to quickly recharging the starting battery, but is completely ignorant of how to charge an AGM, for example. Maybe there's an app for that, but it's not in your stock Engine Control Module. 3, Automotive batteries are not well suited to deep cycle camping usage. 4. Deep cycle batteries are not well suited to automotive charging systems. 5. I know from experience that a smart charger with a maintenance cycle will prolong the life of a battery that gets occasional, not daily, use. 6. There are battery isolators, and then there are Battery Isolators. The first kind are less expensive, but are lossy in their own right. The ones with FET power transistors are low-loss, except for your wallet.

So, in conclusion, You guys win the efficiency award, I get to use my battery for longer. You pays your money and you takes your choice. I hope I answered your questions.

I see Mr. Marquardt posted while I was expounding. I'm going to go see what he has to say. :)
Last edited by capnTelescope on Sun Dec 22, 2013 11:56 pm, edited 1 time in total.
I'll burn that bridge when I come to it.

Brad
ImageImage

My Build
User avatar
capnTelescope
Lifetime member
 
Posts: 1094
Images: 360
Joined: Sun Jun 27, 2004 3:44 pm
Location: Round Rock, TX
Top

Re: Charging while towing

Postby capnTelescope » Sun Dec 22, 2013 11:50 pm

eamarquardt wrote:... Just my two scents.


Yeah, like he said. :thumbsup:
I'll burn that bridge when I come to it.

Brad
ImageImage

My Build
User avatar
capnTelescope
Lifetime member
 
Posts: 1094
Images: 360
Joined: Sun Jun 27, 2004 3:44 pm
Location: Round Rock, TX
Top

Re: Charging while towing

Postby capnTelescope » Mon Dec 23, 2013 12:09 am

@ntsqd -- Yes, voltage drop at high current can be important. For example, the Chrysler 300/Dodge Charger & Magnum of the just past generation had their batteries in the trunk. The red wire going to the starter was as big around as my thumb. What that wire must have cost! $> :frightened:

Can't have low voltage burning up your starter motor. Leads to customer dissatisfaction.
I'll burn that bridge when I come to it.

Brad
ImageImage

My Build
User avatar
capnTelescope
Lifetime member
 
Posts: 1094
Images: 360
Joined: Sun Jun 27, 2004 3:44 pm
Location: Round Rock, TX
Top

Re: Charging while towing

Postby dean_petley » Mon Dec 23, 2013 6:16 am

capnTelescope wrote:

@ Dean -- Your photog friend's setup is pretty ingenious, but I bet it really impacts gas mileage Something like the 4WD penalty you pay whether you use 4WD or not.



i honestly dont think old mate was worried about mileage his tow car was an OKA
Image

i also remember hearing the sweet sound of a big block as he drove out it was one hell of a set up
have funn
dean_petley
Teardrop Builder
 
Posts: 47
Joined: Tue Jul 09, 2013 7:32 am
Location: Sydney AUS
Top

Re: Charging while towing

Postby bdosborn » Mon Dec 23, 2013 11:17 am

You know, I charge while driving all the time.

Image

Of course I'm only about 16% efficient, does that mean I win? :lol:

Bruce
2009 6.5'X11' TTT - Boxcar
Image
Boxcar Build
User avatar
bdosborn
Donating Member
 
Posts: 4214
Images: 450
Joined: Wed May 05, 2004 11:10 pm
Location: CO, Littleton
Top

Re: Charging while towing

Postby ntsqd » Mon Dec 23, 2013 11:19 am

I don't have to remember to turn on or off anything either. By using a Voltage Sensing Relay or Automatic Charge Relay it makes or breaks the connection depending on if the alternator is charging or not. Simple to connect, efficient, and dedicated - no remembering to grab the charger out of the garage. Cost is about the same as having a second charger.

The above calcs forget two important numbers, minimum charging voltage for most batteries (13.6 VDC) and the typical alternator charging voltage (14.4 VDC). Apply those voltage drops to these numbers and notice that you're not always charging even though the alternator is trying to. By simply going to an 8 ga. or larger wire this problem pretty much goes away entirely. Strongly suggest reading the Handy Bob blog.
thom

Where does that road go?
ntsqd
Teardrop Builder
 
Posts: 26
Joined: Mon Sep 21, 2009 2:09 pm
Location: So. CA
Top

PreviousNext

Return to Electrical Secrets

Who is online

Users browsing this forum: cabezon and 1 guest