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 04-16-2016, 06:20 AM   #1
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 350
Voltage Drop when Fridge on DC

We have a brand new Norcold NX841 3-way refrigerator in our AS and I was experimenting with running it purely off of DC. When I switched it over to just DC I noticed that the battery monitor went from 12.8v down to 11.2 right away (also noted fridge was drawing 15 amps and about 175 watts). I have 4 x 6v batteries (Duracell EGC2 golf cart batteries) wired in series parallel (460 amp-hours capacity), and 6 gauge wire running about 10 feet from the battery to the refrigerator.

My question: is it normal for the battery bank voltage to drop that much under a big load (like refrigerator)? If so, what's the physics behind this behavior?

At any rate, the refrigerator flashes a "DC LO" message and won't function on DC alone due to low voltage, hence my question.

Thanks for any input!
trekerboy is offline   Reply With Quote
Old 04-16-2016, 07:26 AM   #2
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 6,014
Images: 2
Blog Entries: 5
Voltage Drop when Fridge on DC

I would check all of the connections. Sounds like you have a serious voltage drop.
Where is the monitor connected in the system?
Does the reading go back to 12.8 volts when you switch to propane?
11.2 volts is a dead battery in my book. But again it could be a bad connection.
TG Twinkie is offline   Reply With Quote
Old 04-16-2016, 07:33 AM   #3
Rivet Master
 
mimiandrews's Avatar
 
1966 22' Safari
Hilltop Lakes , Texas
Join Date: Jun 2008
Posts: 1,764
Unless there is indeed a bad connection, which increases the resistance in the circuit, Ohm's Law says your voltage drop is normal. Gas absorption fridges running on DC draw a heck of a lot of current.

I think that DC fridge function is intended for when you're on the road with the TV's alternator supporting the current draw of the fridge. Even then, make sure it doesn't overload your alternator.
mimiandrews is offline   Reply With Quote
Old 04-16-2016, 12:15 PM   #4
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 6,014
Images: 2
Blog Entries: 5
If you lose 1.6 volts. 11.2 down from 12.8 drawing only 175 watts. It's a bad connection or bad battery(s). Or perhaps the battery bank is not wired correctly and you don't have the full 4 battery capacity you think you have.
TG Twinkie is offline   Reply With Quote
Old 04-16-2016, 12:31 PM   #5
Rivet Master
 
HowieE's Avatar
 
1991 34' Excella
Princeton , New Jersey
Join Date: Aug 2003
Posts: 7,070
Images: 12
Check the batteries with a hygrometer. You may have a bad cell.
__________________
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles

HowieE is offline   Reply With Quote
Old 04-16-2016, 12:56 PM   #6
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 350
Quote:
Originally Posted by TG Twinkie View Post
I would check all of the connections. Sounds like you have a serious voltage drop.
Where is the monitor connected in the system?
Does the reading go back to 12.8 volts when you switch to propane?
11.2 volts is a dead battery in my book. But again it could be a bad connection.

Yup, goes back to 12.8 when the fridge isn't using DC.

Battery Monitor is connected to positive terminal of the battery bank and a shunt which is connected to the negative terminal of the battery bank.

Haven't found any bad connections...
trekerboy is offline   Reply With Quote
Old 04-16-2016, 03:09 PM   #7
Rivet Master
 
Al and Missy's Avatar
 
2002 30' Classic S/O
Fleming Island , Florida
Join Date: Nov 2013
Posts: 4,667
Quote:
Originally Posted by trekerboy View Post
Yup, goes back to 12.8 when the fridge isn't using DC.

Battery Monitor is connected to positive terminal of the battery bank and a shunt which is connected to the negative terminal of the battery bank.

Haven't found any bad connections...
Measure the voltage between the plus and minus battery terminals. Sounds like you are getting too much drop across the shunt, or the shunt is wired wrong.

I think there should be two wires connected to the shunt, one on each side. The monitor should be measuring voltage between the positive and negative posts and calculating current from the shunt resistance and the voltage across it.

Al
__________________
“You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins
Al and Missy is offline   Reply With Quote
Old 04-16-2016, 03:22 PM   #8
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
Was the original refrigerator a 3 way one, that is could it operate on 120 volts, 12 volts, or propane? 12 volt operation of absorption refrigerators takes a lot of power, 15 or more amps as you have noted.

I suspect your original refrigerator only used 12 volts for powering the electronics or even just the light in the refrigerator, and thus has only very small wires running to it, and they are not designed for the 15 + amp load you have put on them.

12 volt operation of the cooling portion of a refrigerator is a huge load on the trailer system, and will kill any battery quickly in any event. It has primarily been used in motorhomes where there is an engine driven alternator system to keep power to the refrigerator coming, without relying on the batteries. The system in my 1983 AS 310 had a 3 way refrigerator system, but had about #10 or #12 wires to the refrigerator, not the little ones typically found on trailer installations.

But, as noted in posts above it could be a poor connection, however, I think you are just overloading the wires that are already in place.
idroba is offline   Reply With Quote
Old 04-16-2016, 06:12 PM   #9
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 350
Quote:
Originally Posted by Al and Missy View Post
Measure the voltage between the plus and minus battery terminals. Sounds like you are getting too much drop across the shunt, or the shunt is wired wrong.

I think there should be two wires connected to the shunt, one on each side. The monitor should be measuring voltage between the positive and negative posts and calculating current from the shunt resistance and the voltage across it.

Al

Voltage at the positive and negative terminals of the battery bank read the same as they do from the battery monitor.

Yes, there are two wires connected to the shunt (Victron Energy Battery Monitor system by the way), well technically 3:

1. Incoming negative bus wire
2. Outgoing negative bus wire (to negative terminal on battery bank)
3. Comm wire (to battery monitor display)
trekerboy is offline   Reply With Quote
Old 04-16-2016, 06:17 PM   #10
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 350
Quote:
Originally Posted by idroba View Post
Was the original refrigerator a 3 way one, that is could it operate on 120 volts, 12 volts, or propane? 12 volt operation of absorption refrigerators takes a lot of power, 15 or more amps as you have noted.

I suspect your original refrigerator only used 12 volts for powering the electronics or even just the light in the refrigerator, and thus has only very small wires running to it, and they are not designed for the 15 + amp load you have put on them.

12 volt operation of the cooling portion of a refrigerator is a huge load on the trailer system, and will kill any battery quickly in any event. It has primarily been used in motorhomes where there is an engine driven alternator system to keep power to the refrigerator coming, without relying on the batteries. The system in my 1983 AS 310 had a 3 way refrigerator system, but had about #10 or #12 wires to the refrigerator, not the little ones typically found on trailer installations.

But, as noted in posts above it could be a poor connection, however, I think you are just overloading the wires that are already in place.

The original fridge was also a 3 way unit, yes.

My AS is a complete renovation; I ran 6 gauge wire from the 12v panel to the fridge knowing that it'd suck a lot of juice.

I'm wondering if it's not something with one of batteries in the 4 x 6v bank... Even with just one fantastic fan on and 1 phone plugged in to charger, the voltage drops from 12.8 to 12.26 at full charge... Seems like the bank should be able to sustain these small things without that much drop, right?
trekerboy is offline   Reply With Quote
Old 04-16-2016, 06:36 PM   #11
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
Quote:
Originally Posted by trekerboy View Post
The original fridge was also a 3 way unit, yes.

My AS is a complete renovation; I ran 6 gauge wire from the 12v panel to the fridge knowing that it'd suck a lot of juice.

I'm wondering if it's not something with one of batteries in the 4 x 6v bank... Even with just one fantastic fan on and 1 phone plugged in to charger, the voltage drops from 12.8 to 12.26 at full charge... Seems like the bank should be able to sustain these small things without that much drop, right?
OK, you do understand the power requirements of the 12 volt part of the refrigerator, and had one in the original installation.

So, it does now sound like the batteries are not doing what they should. I would measure each 6 volt battery under a load, and see how close they are to each other. Most likely you will find one of the batteries in each pair to have a lower voltage across it, compared to the other. Possibly you will only find one of the four with a lower voltage, and it is dragging on the other set. Measure the voltage at the battery terminals, not someplace else in the system.

How old are the batteries, and what charging system have you been using to keep them up during the renovations?
idroba is offline   Reply With Quote
Old 04-16-2016, 07:26 PM   #12
4 Rivet Member
 
Tn Traveler's Avatar
 
2006 25' Safari
Signal Mountain , Tennessee
Join Date: Jan 2016
Posts: 450
Images: 5
Quote:
Originally Posted by trekerboy View Post
Voltage at the positive and negative terminals of the battery bank read the same as they do from the battery monitor.

Yes, there are two wires connected to the shunt (Victron Energy Battery Monitor system by the way), well technically 3:

1. Incoming negative bus wire
2. Outgoing negative bus wire (to negative terminal on battery bank)
3. Comm wire (to battery monitor display)
I think there should be another small gauge red wire connected to the positive battery terminal to power the monitor. At least mine has it.
__________________
Don
'06 Safari 25 LS
'18 GMC 2500HD Duramax/Allison
TN,”Greenest State in the Land of the Free”.Davy Crocket
" America is not a place;it's a road." Mark Twain
Tn Traveler is offline   Reply With Quote
Old 04-16-2016, 07:34 PM   #13
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 350
Quote:
Originally Posted by Tn Traveler View Post
I think there should be another small gauge red wire connected to the positive battery terminal to power the monitor. At least mine has it.

Doh! You're right, there is. So 4 wires total connected to the shunt.
trekerboy is offline   Reply With Quote
Old 04-16-2016, 07:38 PM   #14
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 350
Quote:
Originally Posted by idroba View Post
OK, you do understand the power requirements of the 12 volt part of the refrigerator, and had one in the original installation.



So, it does now sound like the batteries are not doing what they should. I would measure each 6 volt battery under a load, and see how close they are to each other. Most likely you will find one of the batteries in each pair to have a lower voltage across it, compared to the other. Possibly you will only find one of the four with a lower voltage, and it is dragging on the other set. Measure the voltage at the battery terminals, not someplace else in the system.



How old are the batteries, and what charging system have you been using to keep them up during the renovations?
Batteries are almost 2 years old. Been using the integrated charger/inverter/transfer-switch combo unit (AIMS Power PICOGLF20W12V120VR 2000W Pure Sine Inverter Charger) to keep batteries topped up.
trekerboy is offline   Reply With Quote
Old 04-17-2016, 09:44 PM   #15
Rivet Master
 
TouringDan's Avatar

 
1966 24' Tradewind
1995 34' Excella
Lynchburg , Virginia
Join Date: Jun 2006
Posts: 4,225
If you are using 175 watts when operating your fridge on 12v, this sounds like the power requirement of operating the fridge heating element. When on 12v the heating should be by propane and not electricity. 12v should only be used for fridge control electronics. Heating of the chimney should be electrical when plugged into 120v or by propane when 120v is not available.

Dan
TouringDan is offline   Reply With Quote
Old 04-17-2016, 10:04 PM   #16
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 6,014
Images: 2
Blog Entries: 5
Voltage Drop when Fridge on DC

I believe they call it a 3 way because it can cool with propane, 120 volt AC or 12 volt DC.
175 watts on 12 volts is almost 15 amps. Probably more when you figure in the losses. If the element were powered continuously it would reduce a battery's capacity in short order.
It would be relatively easy to duplicate the load of the refer by turning the refer off or putting it in another mode.
The start the furnace, the water pump ceiling fan; stove exhaust fan and every 12 volt light in the coach. Furnace= 6-8 amps; water pump 3-4 amps; fans combined 4-6 amps.
Try this to see if you get a similar voltage drop.
I still say it is a bad connection or battery or something is not wired correctly. The #6 wire you are using should be more than adequate to power the refer.
TG Twinkie is offline   Reply With Quote
Old 04-20-2016, 09:23 PM   #17
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 350
The results are in

Quote:
Originally Posted by TG Twinkie View Post
I believe they call it a 3 way because it can cool with propane, 120 volt AC or 12 volt DC.
That's correct, this fridge can cool using either 120v, propane or 12v as a power source.

Quote:
Originally Posted by TG Twinkie View Post
It would be relatively easy to duplicate the load of the refer by turning the refer off or putting it in another mode. Start the furnace, the water pump, ceiling fan, stove exhaust fan and every 12 volt light in the coach. Furnace= 6-8 amps; water pump 3-4 amps; fans combined 4-6 amps. Try this to see if you get a similar voltage drop.
Ok, started with 12.9 volts then had 3 ceiling fans, 1 hood vent exhaust, 1 bathroom ceiling exhaust, 14 LED lights, 2 USB wall chargers all going at the same time: 194 watts, 17 amps (fridge only was 175 watts, 15 amps). Voltage dropped to 11.5v (lights dimmed a little, you could hear the pitch of the fans change).

So, in summary, to answer your question, I think this qualifies as a similar voltage drop to the fridge. Does this point to culprit? I guess this means it's not a problem specific to the fridge or its' wiring per se...
trekerboy is offline   Reply With Quote
Old 04-21-2016, 07:36 AM   #18
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 6,014
Images: 2
Blog Entries: 5
Again; bad battery(s) or bad connection.
Have you checked the ground/common connection at the point where it connects to the frame or skin.
TG Twinkie is offline   Reply With Quote
Old 04-21-2016, 09:10 AM   #19
3 Rivet Member
 
SpitFireRX's Avatar
 
1979 31' Excella 500
Florida , Florida
Join Date: Jul 2014
Posts: 119
Do the lights ever dim or flicker?
SpitFireRX is offline   Reply With Quote
Old 04-21-2016, 09:26 AM   #20
Rivet Master
 
TouringDan's Avatar

 
1966 24' Tradewind
1995 34' Excella
Lynchburg , Virginia
Join Date: Jun 2006
Posts: 4,225
I don't see a problem here. Any time you put a load on a battery you will get a voltage drop. The bigger the load, the higher the voltage drop.

Dan
TouringDan is offline   Reply With Quote
Reply


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
Combining 4" drop reciever to Hensley 8" drop shank Rascal0729 Hitches, Couplers & Balls 18 07-20-2015 05:52 AM
Voltage Drop/GFI trip jcanavera Electrical - Systems, Generators, Batteries & Solar 7 06-08-2011 10:09 AM
Acceptable voltage drop on 12V? ESCAPE POD Batteries, Univolts, Converters & Inverters 16 02-24-2011 09:41 AM
voltage drop projector Batteries, Univolts, Converters & Inverters 6 09-16-2010 02:24 PM
voltage drop in storage? boondockdad Batteries, Univolts, Converters & Inverters 28 02-01-2009 12:05 PM


Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by the Airstream, Inc. or any of its affiliates. Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.



All times are GMT -6. The time now is 05:29 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.