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05-03-2021, 12:53 PM
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#1
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Rivet Master
2005 30' Classic
Kingston
, Washington
Join Date: May 2011
Posts: 699
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Switch to LiFePo without DC-DC Charger?
Hello. What are the risks if I do not get a DC to DC charger between the truck and the trailer if I switch to LiFePo batteries? I'm thinking it will be a non-issue since the new solar panels on the roof will be charging the batteries at the correct voltages while driving down the road (and maybe even the truck battery). The truck is always unplugged from the trailer while camping too.
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05-03-2021, 01:02 PM
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#2
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Rivet Master
2017 27' International
Wasilla
, Alaska
Join Date: Feb 2018
Posts: 540
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maybe no problem
I recently installed a DC to DC charger in part to prevent what some, but not all, LiFePo users reported as a drain of TV batteries. Might not be an issue depending on your TV circuitry, and certainly not an issue if unplugged while camping.
There are some what-ifs: if your TV doesn't isolate when the ignition is off and you are in Walmart reprovisioning and it has been rainy and overcast for a while... might not be happy for the TV battery.
Browse the DC-DC treads for more detailed what ifs, as well. Part of the reason I installed the Victron in spite of the other options available was the bluetooth monitoring and its capability to condition the flow of electrons according to the app.
__________________
2017 Int'l Serenity 27FB
2020 F250 powered by converted solar
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05-04-2021, 02:35 PM
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#3
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Rivet Master
2005 30' Classic
Kingston
, Washington
Join Date: May 2011
Posts: 699
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Thank you for the reply. i read some of the DC-DC threads, makes me want to get one, but I think I will go without for now and see how it goes.
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05-04-2021, 02:42 PM
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#4
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3 Rivet Member
2021 30' Globetrotter
East Northport
, New York
Join Date: Sep 2016
Posts: 141
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Quote:
Originally Posted by 10Smiles
Thank you for the reply. i read some of the DC-DC threads, makes me want to get one, but I think I will go without for now and see how it goes.
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I passed on the DC to DC charger as well. To isolate the truck I just lifted the 7-pin charge wire off the battery bus bar.
__________________
James
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05-04-2021, 02:44 PM
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#5
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4 Rivet Member
2016 27' Flying Cloud
Hartsburg
, Missouri
Join Date: Dec 2015
Posts: 465
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Suggest that without the DC-DC charger you just disable charging from your tow vehicles and rely on solar.--Frank
__________________
Frank & Fran
2016 27' FC FB with 600 W solar
2016 Ford F150 EcoBoost
Equalizer Hitch
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05-04-2021, 03:01 PM
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#6
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Rivet Master
2022 25' Flying Cloud
NCR
, Ontario
Join Date: Feb 2017
Posts: 3,104
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you need a dc-dc THE CHARGE FROM tv TO as
The TV voltage is not high enough to charge the Lion. as well , The Dc-DC prevents back feed power to drain the battery
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05-04-2021, 03:06 PM
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#7
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Rivet Master
2005 30' Classic
Kingston
, Washington
Join Date: May 2011
Posts: 699
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Yeah, I've thought about that too. I think I will just leave it for now, that way, the solar can trickle charge my truck battery too. I am not worried about either battery (truck or trailer) being depleted (like when it is dark out), the voltage potential between the two types of battery is around one or two volts.
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05-11-2021, 05:11 PM
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#8
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2 Rivet Member
2019 22' Sport
Margaritaville
, Florida
Join Date: Jun 2020
Posts: 44
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Opted for intelligent relay
Instead of a DC-DC charger, I installed a Victron Cyrix-Li-ct relay that disconnects the lithium batteries from the tow vehicle based on the voltage sensed at the TV. It works fine.
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05-11-2021, 05:52 PM
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#9
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2 Rivet Member
2016 22' Sport
WALNUT CREEK
, California
Join Date: Oct 2018
Posts: 99
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I have two Battleborn LiFePo batteries and solar charging on the roof, but have never gotten around to installing a DC-DC charger or other isolation device. Knock on wood, I have never had any problem with TV battery discharge, in spite of the fact that we often don't disconnect when stopping in route for just a night. Maybe just lucky, or perhaps some unique situation with wiring of the TV or trailer.
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05-11-2021, 08:23 PM
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#10
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Site Team
2017 30' International
Broomfield
, Colorado
Join Date: Apr 2009
Posts: 3,555
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I simply pulled the 30A fuse in my truck for the trailer 12v power line in the 7-way. I have enough solar and batteries so I don't need additional charging source.
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05-12-2021, 06:51 AM
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#11
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Rivet Master
2020 28' Flying Cloud
2017 23' Flying Cloud
Hiawassee
, Georgia
Join Date: May 2017
Posts: 1,415
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Quote:
Originally Posted by jmickow
I have two Battleborn LiFePo batteries and solar charging on the roof, but have never gotten around to installing a DC-DC charger or other isolation device. Knock on wood, I have never had any problem with TV battery discharge, in spite of the fact that we often don't disconnect when stopping in route for just a night. Maybe just lucky, or perhaps some unique situation with wiring of the TV or trailer.
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I don’t understand why there would be an issue discharging the TV batteries since they’re going to be at 12.7v and the trailer batteries are at a higher voltage (13.5?). It seems the issue would be discharge of the trailer batteries into the TV.
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05-12-2021, 09:23 AM
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#12
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Rivet Master
2004 28' Classic
Monument
, Colorado
Join Date: Nov 2015
Posts: 1,566
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Quote:
Originally Posted by KK4YZ
I don’t understand why there would be an issue discharging the TV batteries since they’re going to be at 12.7v and the trailer batteries are at a higher voltage (13.5?). It seems the issue would be discharge of the trailer batteries into the TV.
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Lithium batteries have a very low resistance to charging (unlike LA). If they are below full charge (even a small amount), they will pull power from the lead acid battery in your TV. If they are significantly "empty" they will very quickly pull your TV battery down to the point that TV battery can be damaged. The DC-DC charger isolates the two systems. Or, you can simply disconnect the positive side from your TV to the trailer.
This is a non-technical answer. I am sure there are others here that can give you a more technical explanation.
__________________
DaveP
2004 Airstream Classic 28 "Willard"
2023 Ram 3500 4x4
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05-12-2021, 09:56 AM
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#13
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3 Rivet Member
1982 27' Excella
Harrisburg
, Oregon
Join Date: Dec 2020
Posts: 191
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Quote:
Originally Posted by DaveP
Lithium batteries have a very low resistance to charging (unlike LA). If they are below full charge (even a small amount), they will pull power from the lead acid battery in your TV. If they are significantly "empty" they will very quickly pull your TV battery down to the point that TV battery can be damaged. The DC-DC charger isolates the two systems. Or, you can simply disconnect the positive side from your TV to the trailer.
This is a non-technical answer. I am sure there are others here that can give you a more technical explanation.
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This is true. Lithium batteries can charge or discharge at a ferocious rate, and if connected directly to the tow vehicle's charging system they not only can discharge the TV's batteries quickly enough to damage them, but the alternator on the TV will work its absolute hardest to recharge the TV batteries at essentially a 100% duty cycle, overheating the alternator and potentially damaging it too. Some alternators on large luxury cars are water cooled to try to prevent damage, and some pickups have two alternators as an option to charge trailer batteries, but even these water cooled alternators and dual alternators can be damaged by the ferocious charge rate of a bank of Lithium Ion batteries. The DC-to-DC charger can protect the TV's battery and alternators from damage.
Also, remember that "dumb" Lithium batteries can charge quickly enough to catch fire, something that just can't happen on lead-acid batteries. Be careful with Lithium batteries.
Scott
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05-12-2021, 04:39 PM
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#14
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Rivet Master
2020 28' Flying Cloud
2017 23' Flying Cloud
Hiawassee
, Georgia
Join Date: May 2017
Posts: 1,415
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Quote:
Originally Posted by DaveP
Lithium batteries have a very low resistance to charging (unlike LA). If they are below full charge (even a small amount), they will pull power from the lead acid battery in your TV. If they are significantly "empty" they will very quickly pull your TV battery down to the point that TV battery can be damaged. The DC-DC charger isolates the two systems. Or, you can simply disconnect the positive side from your TV to the trailer.
This is a non-technical answer. I am sure there are others here that can give you a more technical explanation.
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Got it. Thanks!
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05-12-2021, 04:57 PM
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#15
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Rivet Master
2015 23' FB International
2007 19' International CCD
Steamboat Springs
, Colorado
Join Date: Nov 2007
Posts: 1,020
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I installed a Renogy 20 amp DC-DC charger as part of my LiFePo upgrade. I do not have solar installed, though I do have a 100W Renogy suitcase.
I went with the 20 amp as I wanted to use the existing 10AWG wires from the 7-pin plug.
Just returned from a trip to Utah and can now report on how it performed.
We camped for 4 days at Lake Powell and drained the batteries to about 66% of 210 AH. This was taking two showers a day, running the fans, lights, invertor to power a 750w hair dryer, coffee grinder, etc.
Then drove about 2-hours to Capital Reef. The batteries re-charged to about 88%. We camped there for three days and drained the batteries to about 75%.
We drove home, but by Green River, the batteries were fully re-charged.
The DC-DC charger worked as hoped it that it would help maintain the batteries when traveling while using 10 AWG. I did install a 30amp fuse as protection.
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05-12-2021, 07:18 PM
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#16
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Rivet Master
2004 28' Classic
Monument
, Colorado
Join Date: Nov 2015
Posts: 1,566
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Steamy,
We are taking our first trip with the 20 A DC-DC Renogy next week. I am looking forward to observing their performance with our new Renogy lithium batteries. I have already measured 24 amps to the batteries at idle in the driveway. Should work well for charging!
__________________
DaveP
2004 Airstream Classic 28 "Willard"
2023 Ram 3500 4x4
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05-13-2021, 08:13 AM
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#17
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Rivet Master
2015 23' FB International
2007 19' International CCD
Steamboat Springs
, Colorado
Join Date: Nov 2007
Posts: 1,020
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Quote:
Originally Posted by DaveP
Steamy,
We are taking our first trip with the 20 A DC-DC Renogy next week. I am looking forward to observing their performance with our new Renogy lithium batteries. I have already measured 24 amps to the batteries at idle in the driveway. Should work well for charging!
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Hi Dave,
did you use the existing 10AWG wires? It seems to work just fine in my configuration.
I considered a RADARC unit or a higher amp Renogy, but did not really want to run separate cables from the vehicle battery to the trailer. It seems like the 20amp unit is a good compromise and value for the money.
I am please with it so far. Good luck on your trip!
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05-13-2021, 05:51 PM
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#18
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Rivet Master
2004 28' Classic
Monument
, Colorado
Join Date: Nov 2015
Posts: 1,566
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Quote:
Originally Posted by Steamy1
Hi Dave,
did you use the existing 10AWG wires? It seems to work just fine in my configuration.
I considered a RADARC unit or a higher amp Renogy, but did not really want to run separate cables from the vehicle battery to the trailer. It seems like the 20amp unit is a good compromise and value for the money.
I am please with it so far. Good luck on your trip!
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Hi Steamy,
I decided to run new 4 gauge wire with a 30 A fuse. But I come from the overkill department of electrical engineering. Seems like your 10 gauge and my 4 gauge work just fine! I'll let you know how it works out on my trip.
__________________
DaveP
2004 Airstream Classic 28 "Willard"
2023 Ram 3500 4x4
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05-13-2021, 06:46 PM
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#19
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4 Rivet Member
2019 30' Flying Cloud
Grass Lake
, Michigan
Join Date: Aug 2018
Posts: 280
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Quote:
Originally Posted by wulfraat
I simply pulled the 30A fuse in my truck for the trailer 12v power line in the 7-way. I have enough solar and batteries so I don't need additional charging source.
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X2. I did the same. Cost =$0.00.
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05-27-2021, 06:43 AM
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#20
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Rivet Master
2004 28' Classic
Monument
, Colorado
Join Date: Nov 2015
Posts: 1,566
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Steamy,
On our trip this last week, the DC-DC generator worked great. We left the campground Monday morning with a 70% SOC. When we arrived home 1 1/2 hours later, the SOC was 83%. Very pleased!
__________________
DaveP
2004 Airstream Classic 28 "Willard"
2023 Ram 3500 4x4
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