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Old 05-19-2020, 09:14 AM   #1
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Protecting Lithium Battery While Towing

I have a lithium battery installed in my Sport 16 and everything works fine except when towing. The lithium battery can significantly discharge while towing due to the voltage difference between the TV and the trailer. Is there a simple solution to prevent this discharge? I don't care about charging the battery while on the road but I don't want to impact the function of the brakes or lights. Can a cutoff switch be installed in the trailer that would interrupt the DC circuit to the TV?

I tried searching on Lithium Discharge Towing as well as a few other things and got no relevant results. Please feel free to suggest another search or point me to any existing threads. I know there must be a few.

Thanks.
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Old 05-19-2020, 09:48 AM   #2
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Welcome to the forum!

In my layman's opinion, there is some larger issue at play, if your lithium battery is discharging while you tow. The tow vehicle and trailer are all based on a 12-volt standard.

Yes, your lithium battery requires a different charger/converter, with its own charge profile, but that is a separate issue, as I understand it.



Above my pay grade to diagnose, but the numerous electrical experts will show up soon IMO. Curious to hear their insights.

Good luck,

Peter

PS -- What year is your Sport 16', and does everything else electrical work OK? Any chance you have a short-circuit someplace which is draining the battery? I think I would unplug from shore power, turn off all 12-volt appliances/lights/radios/speakers/etc. and measure the current flowing from the battery. Your propane detector, if any, should be the only thing drawing 12-volt current IMO.
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Old 05-19-2020, 09:55 AM   #3
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What is your tow vehicle. Often there is a fuse in the charging line you can just pull and leave it out. Check your owners' manual for the fuse box diagram.
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Old 05-19-2020, 11:23 AM   #4
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What is your tow vehicle. Often there is a fuse in the charging line you can just pull and leave it out. Check your owners' manual for the fuse box diagram.

Larry


Agree with this as the simplest solution. If you disabled the charge capabilities of the 7-pin, you canít discharge either. Assuming you donít need to charge through the TV alternator, should be fine.
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Old 05-19-2020, 11:29 AM   #5
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Thread on the topic.

https://www.airforums.com/forums/f37...as-202328.html

Short answer, you need a DC to DC power supply between the TV and the AS. One that accepts LA Battery voltage levels from the TV and provides LI charging voltages to the AS. I have been very pleased with the install of a Renorgy DC to DC to do this.
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Old 05-19-2020, 02:40 PM   #6
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Thanks for that link.

Peter
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Old 05-19-2020, 04:06 PM   #7
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My TV has a fuse dedicated to the charge inline on the 7 pin. I simply pulled it. (option 1)

Otherwise you can do a DC to DC charger, they are a couple hundred bucks, and you will get a charge from the alternator. (option 2)

Option 1 costs nothing
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Old 05-19-2020, 04:27 PM   #8
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get a victron DC DC converter

it ensure that power only goes one way TV -> As and not our from the AS -> TV
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Old 05-19-2020, 06:10 PM   #9
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get a victron DC DC converter

it ensure that power only goes one way TV -> As and not our from the AS -> TV
Hi,
could you advise the model number?

Thanks,
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Old 05-19-2020, 06:26 PM   #10
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i use their Cyrix-CT along with the Orion-TR 24/12-30
it allows up to 30 A into the AS from the TV, one way only

this is my schematic
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Old 05-19-2020, 06:38 PM   #11
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Thank you! how to connect is still a little fuzzy to me, but I'll study your schematic. Very helpful!!
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Old 05-19-2020, 07:18 PM   #12
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Thank you! how to connect is still a little fuzzy to me, but I'll study your schematic. Very helpful!!
Steamy1, there are battery isolators (to keep the TV and trailer batteries separate) and DC-DC chargers that include an isolator. Renogy and Redarc (Aussie company) make several models depending on the output you need.

The beauty of these are they support Lithium charging that won't hurt your TV alternator. That is a know problem if you're not careful.

Check out this one from Renogy (there's a video on the page)

Redarc models include a solar input with a MPPT controller that will balance the charge between available solar + TV alternator.

Good luck!
Jeff
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Old 05-19-2020, 07:21 PM   #13
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Thank you Jeff!

I just installed two Lion Energy UT1300 LiPo batteries and would like to protect the investment.
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Old 05-19-2020, 07:25 PM   #14
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My 2010 Tundra has a dedicated relay and fuse for the trailer charge pin. Pulled out the relay and put it in the glove box.
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Old 05-19-2020, 07:25 PM   #15
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Steamy1, there are battery isolators (to keep the TV and trailer batteries separate) and DC-DC chargers that include an isolator. Renogy and Redarc (Aussie company) make several models depending on the output you need.

The beauty of these are they support Lithium charging that won't hurt your TV alternator. That is a know problem if you're not careful.

Check out this one from Renogy (there's a video on the page)

Redarc models include a solar input with a MPPT controller that will balance the charge between available solar + TV alternator.

Good luck!
Jeff
Hi Jeff,
Do you think the 20A model is robust enough for the two UT1300s?
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Old 05-20-2020, 07:14 AM   #16
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Hi Jeff,
Do you think the 20A model is robust enough for the two UT1300s?
Hi Steamy1,

According to the Lion specs, your batteries can charge at a rate of up to 100A. You could use the Renogy 20A model but it will take longer to charge (not unlike charging from the 7 pin with your original batteries but still a lot faster).

If you want faster charging, the new Renogy 60A model would be better. Just bear in mind you need to run large gauge wire from your tow vehicleís engine compartment underneath to the rear by your hitch. Itís not difficult and there are several YouTube videos of how to do it.

GMFL, another Forum member installed a Renogy DC-DC unit in the Long, Long Honeymoon coupleís Airstream as part of their big solar project. That video is also on YouTube. Itís the best way to charge up the Lithium batteries on the road quickly without solar.

Good luck!
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Old 05-20-2020, 09:19 AM   #17
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Hi Jeff,
Do you think the 20A model is robust enough for the two UT1300s?
Many tow vehicles don’t supply even that much to the charge line of the 7pin connector. My late model F150 only has 18 ga wire going to it! I’m limited to around 10amps. If you can find the fuse for the trailer connector that might give you an idea of the absolute maximum. I’d limit your current to half that.
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Old 05-20-2020, 09:20 AM   #18
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LAPowers there might be something else going on to drain your batteries. Most Lithium setups are around 13.5 volts or so when charged. Most tow vehicles alternators will be running about 14 volts. Since you don't mention your tow vehicle the alternator might be different.

If these generalizations apply then something isn't working correctly on your TV or you have something like the inverter turned on while towing putting a load on the trailer batteries.
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Old 05-20-2020, 10:04 AM   #19
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What year is your sport 16? I have a 2018, with two solar panels. I am in the middle of trying to figure out how to implement a Delta 1000 solar generator (goal zero clone) as my power source and eliminate my lead acid batteries.
What other modifications have you done?
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Old 05-20-2020, 10:39 AM   #20
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What year is your sport 16? I have a 2018, with two solar panels. I am in the middle of trying to figure out how to implement a Delta 1000 solar generator (goal zero clone) as my power source and eliminate my lead acid batteries.
What other modifications have you done?
Sport 16 STL, you might want to check out what Pteck did with a GZ and a bypass switch. He documented everything really well here: https://www.airforums.com/forums/f37...um-196422.html

Itís an idea Iím keeping an eye on. You could install a Redarc DC-DC charger with the solar option that has a built-in MPPT controller. The beauty of that solution is it will use solar first and make up the difference with your TVís alternator power when on the road. Really cool option...
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