|
|
07-26-2016, 08:59 AM
|
#21
|
Senior Member
Name: Gordon
Trailer: 2015 Scamp (16 Std Layout 4) with '15 Toyota Sienna LE Tug
North Carolina
Posts: 5,155
|
Quote:
Originally Posted by BonesD
... but do have a antiwar bar. ..
|
Yes I agree.. make love, not war
|
|
|
07-26-2016, 09:07 AM
|
#22
|
Senior Member
Trailer: Trillium 2010
Posts: 5,185
|
The voltage drop of the charge line is always the difference between the two batteries and is independent of the wire gauge. What the wire size does determine is the charging current and thus in part how long the trailer battery will take to charge. No matter what size wire is present, sooner or later both batteries will reach the same voltage. Raz
|
|
|
07-26-2016, 09:42 AM
|
#23
|
Junior Member
Name: Dick
Trailer: Casita
Texas
Posts: 25
|
That would have been my guess. It may mot be in a full blown charge mode to the loss in wire capacity but anything is better than nothing . With shore power, and a generator this gives me a third option. Just about anything I can do to insure a succesful outing is a good investment.
Thank you
|
|
|
07-27-2016, 06:47 AM
|
#24
|
Member
Name: Dan
Trailer: Scamp
Iowa
Posts: 93
|
Quote:
Originally Posted by Tom Trostel
Many Casita owners are not happy with the ability of the tow vehicle to charge the trailer battery while towing. DC loses a lot of power running thru 20' of 12 gauge wire to reach the Casita. Some owners upgrade the charging wire to 6 gauge but lots of work. YMMV.
|
Not to go off topic, but when you say this do you mean they upgrade the wire IN the TV or from the connector to the trailer's battery?
Thanks,
Dan
Sent from my SM-G900V using Tapatalk
|
|
|
07-27-2016, 07:53 AM
|
#25
|
Senior Member
Trailer: 1973 Compact Jr and 1980 Bigfoot 17 ft
Posts: 1,339
|
Dan, I'm not a Casita owner but have read both Casita forums daily for 12 years. Some owners find that their tv charges the trailer battery fine. So many factors are involved; discharge state of trailer battery, output of the tv alternator, how long you drive, etc. Those that are not happy run larger gauge wire from under the hood thru or under the tv, with a cut-off, to get max charge to the trailer.
__________________
1980 Bigfoot 17' & former owner of 1973 Compact Jr
|
|
|
07-27-2016, 11:22 AM
|
#26
|
Senior Member
Trailer: Trillium 2010
Posts: 5,185
|
Just to add to what Tom said, my factory wired Frontier will charge my trailer battery in about 3-4 hours. The charge line appears to be 14 ga but it might be 12 ga. This works for two reasons. My truck is the "work truck" model with minimal electrical demand and we run a small group 24 battery with just led lights, and the water pump for dishes and hand washing ( no shower).
If a battery is not charging fully, the problem is not due to voltage drop. Left long enough the battery will charge fully but since you don't want to spend you're afternoon riding around the campground a bigger charge line may help as it will increase the current and decrease the charging time. The next limiting factor is the alternator capacity and vehicle demand. For example I've found it takes longer to charge my battery if I drive with my lights on.
There are some situations, where folks have a large battery with high trailer demand and the charging system is just not up to the task. They either cut back demand, install a larger alternator, or in some cases add roof top solar Raz
|
|
|
07-27-2016, 12:31 PM
|
#27
|
Senior Member
Name: Gordon
Trailer: 2015 Scamp (16 Std Layout 4) with '15 Toyota Sienna LE Tug
North Carolina
Posts: 5,155
|
Quote:
Originally Posted by Raz
..
If a battery is not charging fully, the problem is not due to voltage drop. Left long enough the battery will charge fully ...
|
Q: Say I have a 100 AH lead acid battery that starts fully charged reading 13.6 volts, that I have discharged 25% and then has a voltage of 12.4 VDC. Say also that I have a charging system where the voltage at the battery is 10 volts (due to high resistance in the wiring or something else). Typical, how long will it take for the battery to be fully charged and back to 13.6 volts? Relating to your statement above, how long is long enough?
|
|
|
07-27-2016, 01:34 PM
|
#28
|
Senior Member
Trailer: Trillium 2010
Posts: 5,185
|
Quote:
Originally Posted by gordon2
Q: Say I have a 100 AH lead acid battery that starts fully charged reading 13.6 volts, that I have discharged 25% and then has a voltage of 12.4 VDC. Say also that I have a charging system where the voltage at the battery is 10 volts (due to high resistance in the wiring or something else). Typical, how long will it take for the battery to be fully charged and back to 13.6 volts? Relating to your statement above, how long is long enough?
|
10 volts?The tow battery (alternator) must be greater that the trailer battery for charging to occur.
Suppose your tow is at 14 volts and your trailer battery is at 12 volts. Then the charging current is (14v - 12 v)/ the charge line resistance. If R charge line is 0.1 ohms you have an instaneous current of 20 amps but only if the tow system has 20 amps to spare. Typically with any source,, as you draw more current loading, a reduction in voltage, occurs. Example. Lights dim when a motor starts. Also, nothing is static. As the battery charges its voltage goes up. This will reduce the charging current. Lots of variables. How long will it take to charge your battery? Don't know. But by knowing your use you can make an educated guess.
|
|
|
07-27-2016, 03:04 PM
|
#29
|
Senior Member
Name: Gordon
Trailer: 2015 Scamp (16 Std Layout 4) with '15 Toyota Sienna LE Tug
North Carolina
Posts: 5,155
|
Quote:
Originally Posted by Raz
10 volts?The tow battery (alternator) must be greater that the trailer battery for charging to occur. ...
|
Oh... I guess we are assuming that the alternator (or other charging source) voltage is higher than, 1. the voltage of the battery when fully charged PLUS, 2. any voltage drop in the system. Otherwise you end up with incomplete charging.
|
|
|
07-27-2016, 03:17 PM
|
#30
|
Senior Member
Trailer: Scamp
Posts: 7,056
|
Quote:
Originally Posted by gordon2
Oh... I guess we are assuming that the alternator (or other charging source) voltage is higher than, 1. the voltage of the battery when fully charged PLUS, 2. any voltage drop in the system. Otherwise you end up with incomplete charging.
|
I believe you mentioned that you're a ham radio operator. Look at your basic electronic stuff. A battery charging profile looks kind of like a capacitor charging. Then look at ohm's law. The difference between the tow battery voltage (13.8 is norm for vehicle systems) and house battery. So your house battery is about 12 volts and you start charging it from the tow it's a 1.8 volt difference you can calculate the current without the losses. As the house battery gets closer to full charge the differential voltage gets less. The IR (wire loss) is so small that even with 12 to 14 gauge wire the loss is so small you won't be able to detect the difference.
__________________
Byron & Anne enjoying the everyday Saturday thing.
|
|
|
07-27-2016, 03:32 PM
|
#31
|
Senior Member
Name: Gordon
Trailer: 2015 Scamp (16 Std Layout 4) with '15 Toyota Sienna LE Tug
North Carolina
Posts: 5,155
|
Quote:
Originally Posted by Byron Kinnaman
... The IR (wire loss) is so small that even with 12 to 14 gauge wire the loss is so small you won't be able to detect the difference.
|
But the effect DOES remain. By now you have probably figured out that I was playing devil's advocate to point out that whether or not voltage drop has any noticeable effect, or even is measurable within reason, it still exists. I think some people may have been left with the impression that line loss does not exists at all with two batteries in parallel being charged.
|
|
|
07-27-2016, 03:40 PM
|
#32
|
Senior Member
Trailer: Trillium 2010
Posts: 5,185
|
There is no IR loss. It's a two source network. The voltage drop across the charge line, connections, what ever is between the battery terminals is always the difference between the sources. KVL
|
|
|
07-27-2016, 03:50 PM
|
#33
|
Senior Member
Trailer: Trillium 2010
Posts: 5,185
|
Quote:
Originally Posted by gordon2
Wire has resistance.. unless at absolute zero. Im done.
|
True. And that resistance determines the current. Replace the trailer battery with a light bulb and now you have voltage loss across the wires. A one source network which results in a voltage divider.
|
|
|
07-27-2016, 04:12 PM
|
#34
|
Senior Member
Trailer: Trillium 2010
Posts: 5,185
|
The mistake folks make is that they wish to multiply the current by the wire resistance and subtract it from the tow battery to get the trailer battery voltage. What they forget is that the trailer battery is also a power source and the chemical reaction in the battery determines it's voltage. Don't treat the trailer battery like a light bulb.
|
|
|
|
|
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
|
|
Thread Tools |
Search this Thread |
|
|
Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
» Recent Discussions |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
» Upcoming Events |
No events scheduled in the next 465 days.
|
|