Scamp 12v Charging on Road Question - Page 2 - Fiberglass RV
Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 08-14-2014, 10:56 AM   #21
Senior Member
 
Glenn Baglo's Avatar
 
Trailer: Escape 17 ft
Posts: 8,314
It is unlikely that you have a #10 ground unless you specified it. My installer charged me an extra $25 because he had to buy #10 wire, which is not normally used.
__________________
What happens to the hole when the cheese is gone?
- Bertolt Brecht
Glenn Baglo is offline   Reply With Quote
Old 08-14-2014, 12:05 PM   #22
Moderator
 
Name: RogerDat
Trailer: 2010 Scamp 16
Michigan
Posts: 3,731
Quote:
Originally Posted by Glenn Baglo View Post
It is unlikely that you have a #10 ground unless you specified it. My installer charged me an extra $25 because he had to buy #10 wire, which is not normally used.
Same with my installer of my 7 pin plug on the TV except that they did not want to go and purchase the #10 and went with #12.

Going to scrap yard you can often get good #10 or #8 wire cheaper than you can buying it new.
RogerDat is offline   Reply With Quote
Old 08-14-2014, 12:34 PM   #23
Senior Member
 
fusedlight's Avatar
 
Name: gary
Trailer: 16' 1998 Scamp
Minnesota
Posts: 676
Registry
Quote:
Originally Posted by honda03842 View Post
We have found that in general it's not necessary to run the fridge when driving. It stays relatively cold. If you're concerned put some ice into a sealed container and it will keep the fridge cold enough.
Not so much when you are traveling across Nevada in the summer! With the outside being OVER 100F and the refrigerator side of the Scamp in the sunlight the 'fridge struggled to stay cooler than 40F even when set to "MAX". We do, though, always "cold soak" the refrigerator for a couple of days before heading out.
fusedlight is offline   Reply With Quote
Old 08-14-2014, 12:51 PM   #24
Senior Member
 
Steve L.'s Avatar
 
Trailer: Casita Spirit Deluxe 2003 16 ft
Posts: 1,899
Registry
Quote:
Originally Posted by RogerDat View Post
Think of your battery as a reservoir being filled by your TV charging system, your fridge is drawing from the reservoir as it is being filled. If you draw more from the reservoir (battery) than flows in (from TV charging) the level in reservoir drops...
Or think of this fine gentleman, think of your alternator as filling the cup (the battery charge). If he's drinking faster than.... Oh never mind.
Attached Images
 
Steve L. is offline   Reply With Quote
Old 08-14-2014, 02:32 PM   #25
Senior Member
 
CampyTime's Avatar
 
Name: Wendy Lee
Trailer: Scamp 13' Standard
New York
Posts: 1,070
Registry
Dear Bob,

No doubt I explained everything incorrectly, and would be hard pressed to correct. My knowledge does not even approximate any replies I read, and so I am just a learner. A lot to soak in, if you will.

My Scamp is a 2012. 13er. I will ask my mechanic to change out ground wire to #10 when I speak to him next. I will probably wait to buy new battery as it will just sit all winter anyway.

Thank you for teaching me some. I understand things theoretically, but not deeply as you gentlemen can.

What is the difference between group 24 and 27 batts? Everyone calls the 27 an upgrade, so when I buy I should get that?


Sent from my iPhone using Fiberglass RV
CampyTime is offline   Reply With Quote
Old 08-14-2014, 03:20 PM   #26
Senior Member
 
Bob Miller's Avatar
 
Trailer: Class A Motorhome
Posts: 7,912
Paying your mechanic to install a larger ground wire is no assurance of, and has almost no chance of, fixing what is a much larger problem that has yet to be easily resolved in the RV community as a whole.

But it sounds like you may have the newer type of converter, but I am confused about the mention of an ON/OFF switch of some sort. Can you tell us the name on the front of the converter, it could be either 'American" brand or "Progressive Dynamics". The American brand will have about 5-6 fuses positions, the Progressive about 10-12 fuse positions.

Bottom line, running the refrigerator on 12 volts while under way is not a viable option for at least 98% of RV'ers. To that end, many RV refrigerators are 2 way, 120VAC and LP only and almost none are offered as 12VDC and LP except for large truck applications.

Is there some concern with using LP while under way? If so. voice your concerns.

BTW: A Group 27 battery is the next size larger from a group 24 and has about 50% more reserve capacity, meaning it's sorta like having an extra 1/2 of a battery. BUT, as it has a higher capacity, it can draw more from you alternator to recharge while towing.



Bob Miller is offline   Reply With Quote
Old 08-14-2014, 03:24 PM   #27
Senior Member
 
honda03842's Avatar
 
Name: Norm and Ginny
Trailer: Scamp 16
Florida
Posts: 7,513
Quote:
Originally Posted by RogerDat View Post
Wire size matters due to voltage drop, longer and thinner the wire the more the voltage will drop between the alternator and the battery end. You can only "push" charge into a battery if the charging voltage is greater than the battery voltage.

The heating element on the fridge does not care as much about the voltage as long as it can get the amps. Fridge would probably run fine on 11.9 volts where battery with only 11.9 volts of charging voltage would not really get charged much over ~40% charge. Once the battery gets charged to 11.9 volts the "pressure" is equal between the battery and 11.9 volts on charging line. Not much current would flow to battery to increase the charge
It's true that the fridge wants to see amps but amps come from volts and power is amps times amps.

As to wire size, the nice thing about small trailers is that wires are short and it's the combination of length and diameter that counts. The difference between these wire sizes #8, #10, #12 over 20 feet is about 0.1 volts between sizes.

I might use a larger wire if wiring from scratch but I doubt that I would spend time replacing a #12 with a #10 for a tenth of a volt improvement.
__________________
Norm and Ginny

2014 Honda Odyssey
1991 Scamp 16
honda03842 is offline   Reply With Quote
Old 08-14-2014, 05:03 PM   #28
Senior Member
 
Bob Miller's Avatar
 
Trailer: Class A Motorhome
Posts: 7,912
Amps times Amps = ???
Power Formula sez: Amp times Volts = Watts
Voltage drop over a distance is relative to current flow and is not a fixed value.
I (current) x R (resistance) = E (voltage drop)



Bob Miller is offline   Reply With Quote
Old 08-14-2014, 05:25 PM   #29
Senior Member
 
Bob Miller's Avatar
 
Trailer: Class A Motorhome
Posts: 7,912
Selfie

Quote:
Originally Posted by Steve L. View Post
Or think of this fine gentleman, think of your alternator as filling the cup (the battery charge). If he's drinking faster than.... Oh never mind.
Errr... Steve... Is that a recent or an older selfie?



Bob Miller is offline   Reply With Quote
Old 08-14-2014, 05:59 PM   #30
Moderator
 
Name: RogerDat
Trailer: 2010 Scamp 16
Michigan
Posts: 3,731
I'm pretty sure I sort of butchered my explanation. But from the alternators perspective the house battery is a load, the TV accessories are a load, the TV battery is a load.

If the alternator can't produce the amps for the regulator to maintain voltage greater than charge voltage of house battery it won't gain charge, if the load is running high enough the alternator output won't be able to maintain voltage above house battery and battery will lose charge.

Fridge heating element won't stop being a load no matter what the voltage is, it won't get as hot at lower voltage so fridge won't work as well and below a certain threshold probably won't cool much if any.

Going from #12 to #8 won't improve the alternator output so it won't "solve" an alternator power deficit. In terms of just charging the house battery going down the road that .2 volts is all benefit. Roughly 8% higher voltage near as I can figure. Especially useful if the stock alternator is designed to meet the load of the vehicle accessories which are running and your trying to put a charge in the house battery you just spent the last couple of days running down.

I thought I read that the more amps one runs through a wire the greater the voltage drop. If I have it correctly #12 would have around twice the voltage drop as #8 at 10 amp draw. This does not take into account the alternator/regulator working to keep the voltage at a constant target voltage. Not sure how that all plays out, especially if I have to do math.

I am not an EE or even electrician so this is just my somewhat fuzzy understanding. I would rather have folks with more knowledge clarify my fuzzy so I can learn than have bad information out there.
RogerDat is offline   Reply With Quote
Old 08-14-2014, 06:14 PM   #31
Senior Member
 
Name: Russ
Trailer: Scamp 16' side dinette, Airstream Safari 19'
California
Posts: 588
10 gauge is wimpy. Use 8 for ground and B+ if you want to run a high draw fridge. You want all those yummy volts coming out of the end of the wire. You may have to trim some strands off the 8 ga. to fit into the 7 pin connector, but it won't hurt the performance, since resistance is additive by length.
Russ
ruscal is offline   Reply With Quote
Old 08-14-2014, 06:20 PM   #32
Senior Member
 
Name: Russ
Trailer: Scamp 16' side dinette, Airstream Safari 19'
California
Posts: 588
Quote:
Originally Posted by Steve L. View Post
Or think of this fine gentleman, think of your alternator as filling the cup (the battery charge). If he's drinking faster than.... Oh never mind.
Steve,
I think he is getting a full charge! He learned a long time ago you need large diameter hoses.
ruscal is offline   Reply With Quote
Old 08-14-2014, 06:40 PM   #33
Senior Member
 
Bob Miller's Avatar
 
Trailer: Class A Motorhome
Posts: 7,912
I think you are on the right track, it's all about sensed voltage. As the alternator senses that the combined voltage of the two batteries in parallel with each other reached optimum value, it starts reducing it's output voltage, therefore it's charging current.

As a vehicle battery will reach full charge quickly after a starter cycle, the higher voltage of the vehicles battery raises the average voltage of the two battery's and reduces the voltage (and available current) to the coach battery, resulting in a lower than desired charge current to the coach battery.

This, combined with the 8-10 amps needed by the refrigerator, results in drawing down the coach battery while, at the same time, the charge voltage (current) to the coach battery is lower than needed. phew.....



Bob Miller is offline   Reply With Quote
Old 08-14-2014, 07:02 PM   #34
Senior Member
 
sokhapkin's Avatar
 
Name: Sergey
Trailer: 2014 Scamp 16 layout 4, 2018 Winnebago Revel 4x4
SW Florida
Posts: 835
Gauge 10 12v wire running from TV battery to 7 pin connector (about 20' in length) runs 3-way refrigerator and charges trailer battery just fine while driving. #10 ground wire to 7 pin connector comes from the closest ground point in the trunk area of the TV.
__________________
Sergey
sokhapkin is offline   Reply With Quote
Old 08-14-2014, 07:13 PM   #35
Moderator
 
Name: RogerDat
Trailer: 2010 Scamp 16
Michigan
Posts: 3,731
I think that is the nub of the question. What is the perceived voltage by the alternator. Followed by its capacity to raise that voltage. Someone mentioned Kirchhoff's voltage law as determining the voltage at the charge wire. Might that determine the voltage being responded to by the regulator?

When I think of the batteries as load the TV battery becomes a non-load pretty quickly in that it gets up to the voltage the regulator is shooting for in a short period of time. Except absent a diode one way bridge what keeps the TV battery from contributing voltage if the circuit voltage is lower than the battery.

Put another way without isolation how would the house battery go dead and not the TV battery?

Someone needs to start filling my hat faster. If I'm going to have this headache I should have had more beer.
RogerDat is offline   Reply With Quote
Old 08-14-2014, 07:39 PM   #36
Senior Member
 
CampyTime's Avatar
 
Name: Wendy Lee
Trailer: Scamp 13' Standard
New York
Posts: 1,070
Registry
Ok gentlemen, I'm completely lost. But I am most definitely smiling and completely entertained with your cerebral banter.

What a bunch of great guys!


Sent from my iPhone using Fiberglass RV
CampyTime is offline   Reply With Quote
Old 08-14-2014, 07:41 PM   #37
Senior Member
 
sokhapkin's Avatar
 
Name: Sergey
Trailer: 2014 Scamp 16 layout 4, 2018 Winnebago Revel 4x4
SW Florida
Posts: 835
Quote:
Originally Posted by Bob Miller View Post
As a vehicle battery will reach full charge quickly after a starter cycle, the higher voltage of the vehicles battery raises the average voltage of the two battery's and reduces the voltage (and available current) to the coach battery, resulting in a lower than desired charge current to the coach battery.

This, combined with the 8-10 amps needed by the refrigerator, results in drawing down the coach battery while, at the same time, the charge voltage (current) to the coach battery is lower than needed. phew.....
Raising vehicle battery voltage increases current flow to the trailer's battery and refrigerator. The Ohm's law. Sure the charge voltage on the trailer battery will always be slightly lower than TV battery voltage because of refrigerator's draw, but it will be enough to continue the charging. The thicker the wires are, the lesser will be the difference in voltage.
__________________
Sergey
sokhapkin is offline   Reply With Quote
Old 08-14-2014, 08:51 PM   #38
Senior Member
 
floyd's Avatar
 
Trailer: 2004 13 ft Scamp Custom Deluxe
Posts: 8,425
Registry
We have a deep freeze at home. We stock 64oz juice bottles filled with water(or tea) in the freezer.
We chill the fridge on shore power before a trip then place some of these bottles in the fridge along with food stuff.
We often still have ice after 5-7 days.
We also have cold water, iced tea or lemonade to drink as they thaw!
I almost never use the 12V setting on my fridge.
My Tow vehicle does keep my battery charged for lights, television, DVD, furnace, fantastic fan, etc.
floyd is offline   Reply With Quote
Old 08-14-2014, 09:30 PM   #39
Senior Member
 
honda03842's Avatar
 
Name: Norm and Ginny
Trailer: Scamp 16
Florida
Posts: 7,513
Quote:
Originally Posted by Bob Miller View Post
Amps times Amps = ???
Power Formula sez: Amp times Volts = Watts
Voltage drop over a distance is relative to current flow and is not a fixed value.
I (current) x R (resistance) = E (voltage drop)
With reference to the fridge heating element.
My point is that as the Voltage drops the Current decreases.

As a result the power decreases because Power = Current times Voltage.

Also Voltage equals Current time Resistance.

As a result by substitution power equals Current times Current times Resistance.

The effect of dropping voltage is felt twice because when the voltage drops the current drops as well. Regardless power is also equal to current times current times resistance.

Roger and others,
I agree you want to be as efficient as you can be but to go from #12 to #10 wire only buys you a 1/10th of a volt at 10 amps.

To me it's not worth replacing wire to get a 1/10th of a volt on 20 feet of wire. If we're talking about an even shorter ground line it makes less sense.
__________________
Norm and Ginny

2014 Honda Odyssey
1991 Scamp 16
honda03842 is offline   Reply With Quote
Old 08-16-2014, 04:45 PM   #40
Senior Member
 
Timber Wolf's Avatar
 
Name: Tim
Trailer: '88 Scamp 16, layout 4
North Florida
Posts: 1,547
I don't know about charging, but I know I have 12V running back from my Tug to the Scamp (while under way). I have not had a battery hooked up since getting the Scamp several months back. Feeling that the A/C might work better with a little more air flow across the coil I installed a smallish auxiliary fan behind the unit. It is 12v and I put a switch up in the closet so it could easily be turned on and off. Last week leaving our last camp I forgot to turn it off, but since I do not have a battery it quit when I unplugged from shore power. I never knew it was running the whole time going down the road as it stopped each time I stopped the tug along the way, Had I not made a quick stop and not shut the Tug off I would not know it was running yet (when under way).
Timber Wolf is offline   Reply With Quote
Reply

Tags
scamp


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Battery Charging While Driving Question...? Boots Electrical | Charging, Systems, Solar and Generators 4 11-23-2011 09:56 PM
Battery charging question Joe in MN Problem Solving | Owners Helping Owners 5 09-25-2010 05:29 PM
Battery charging question Kent I Problem Solving | Owners Helping Owners 4 12-29-2008 06:30 PM
1977 scamp interior light question/12v ? Flygal Problem Solving | Owners Helping Owners 6 06-18-2008 10:03 AM
Another battery charging question Sonny Care and Feeding of Molded Fiberglass Trailers 8 09-30-2006 08:14 PM

» Upcoming Events
No events scheduled in
the next 465 days.
» Featured Campgrounds

Reviews provided by


All times are GMT -6. The time now is 11:28 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.