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10-05-2024, 01:10 PM
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#1
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Member
Texas Boomers Club
Join Date: Apr 2020
Posts: 38
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Storing lithium with absorption fridge
I have a Dometic absorption fridge and have recently gone lithium. I have always left my fridge on 24/7, but storage of the LiFePo calls for disconnecting them. As fridge won't run without 12V, any suggestions for how to keep the fridge on with batts disconnected? In the past, I have typically kept the rig plugged in with charger on float for LA batts. As i understand, I must not do that with LiFePo. Work around? Thx
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10-05-2024, 01:37 PM
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#2
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Senior Member
Join Date: Mar 2022
Posts: 512
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I have a similar setup. My Dometic Model: DM2852 runs all the time, shore power when available and LP when not. LiFePO4 batteries as well.
Myself, I don't think floating at 13.6V is a problem but what I do is turn off my converter and let the refrigerator slowly drain the battery, then fire up the converter (or solar) and recharge. I just looked at the drain and the refrigerator uses about 500mA, so maybe 12Ah of capacity per day.
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2019 Palomino Solaire 147X
2013 Ford F150
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10-05-2024, 01:39 PM
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#3
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Senior Member
Join Date: Dec 2019
Location: America's Seaplane City.
Posts: 1,295
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Lithiums do not like to be floated at 100%. If you're charger has the ability to adjust the float set it to 13.3or 13.2 and leave the batteries connected. This will still provide power for the fridge and other loads but will keep the batteries at a less harmful charge level.
We store our Trek at the house plugged in with the charger switched off so I just look at the battery monitor once in a while to see when it's time to charge.
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1998 Safari Trek 2480, 7.4 Vortec, 132k miles
'15 Kawasaki Versys650LT, well farkled, 111k miles
Mid Flowriduh
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10-05-2024, 01:54 PM
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#4
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Senior Member
Join Date: Jul 2014
Posts: 37,089
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Switch off the batteries and let the converter power the fridge. Converters don't need batteries.
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10-05-2024, 03:15 PM
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#5
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Senior Member
Join Date: Feb 2020
Posts: 821
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Quote:
Originally Posted by twinboat
Switch off the batteries and let the converter power the fridge. Converters don't need batteries.
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This.
I do this all the time with my LiFePo4.
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10-05-2024, 04:13 PM
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#6
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Senior Member
Join Date: Mar 2012
Location: Florida panhandle
Posts: 1,305
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what lithium battery do you have?
I have an ionic 100AH and leave it connected to the converter or solar all the time while absorption fridge is on. I think if the converter, solar and BMS are designed right, it’s fine
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2018 Adventurer 19RD 19’ 11”
Ford E350 V10 Cutaway Chassis Class C
#10050 GVWR, #18500 GCWR Smoke that!
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10-05-2024, 05:22 PM
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#7
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Senior Member
Join Date: Mar 2024
Location: Bohemia NY
Posts: 1,984
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Lithium Batteries management
I think many of the battery storage and usage restrictions are a bit of storytelling and manufacturers having ready excuses to not honor warranties.
For my part I accept that they are consumables and will only do so much to imaginarily extended their life. So, while I have over 40 years' experience with most common battery systems in many sizes and applications, I only have a few years with Lithium for back up and motive (forklift) power applications. What is an unknown is what the features and set points are for the BMS that are part of most purchased self-contained batteries. Most have all of these restrictions addressed, we just need to instrumentation to monitor and adjust if needed.
So, for the 2, 300 A/H LiPuls I installed in my 2008 Nimbus I have observed the following.
For charging, you need voltage above 13.6 volts with the only limit keeping the charging current under the 200 A/H maximum.
As battery state of charger goes above 80% the BMS will begin limiting current if needed. Constant voltage of 14.2 to 14.6 such as from an alternator is perfect approaching this stage.
The alternator trying to maintain 14.2 volts with the Foretravel DUVAC and diode block set up, I observer approximately 120 A/H going into the 600 A/H combined bank. I have a 270 A/H alternator. This works. If I add the 150 A/H inverter Charger, the two sources combined will bring the charge rate to about 200 amps.
After the batteries are fully charged it appears the BMS turns off charging on both batteries as there is only a .34 A/H charge current for the combined batteries. This is with the inverter/charger floating at 13.6 volts. Cycle the charger, goes to 14.6 but the current does not increase or change. Same with starting the engine and adding the alternator. Now here is the fun part. The batteries will not accept a charge again until enough current has been drawn to bring them under 90% SOC.
For my coach power needs to be available for the absorption fridge if I want to leave it on. I also need power for the DC air compressor which manages the leveling system and maintains the slide out room pneumatic seals. Storage for me most likely will not be for more than 1 or 2 months on a regular basis. Also, for my coach the chassis batteries are not automatically charged from the house battery system. I need to make a decision and action for that to happen. I have to turn on the boost switch. My LiPuls each cost about the same as tank of fuel. If they fail in less than 10 years so be it.
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Dennis
Bohemia NY
2008 Nimbus 342 SE Carlyle
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10-06-2024, 08:47 AM
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#8
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Senior Member
Join Date: Nov 2018
Location: Beaver Dam, Wisconsin
Posts: 5,897
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Most modern converter/chargers will work without a battery connected. That will provide the refrigerator with 12 volt power to controls.
Post make and model of converter/charger for better advice.
Follow battery manufacturer's instructions for storing the lithium battery. Disconnect the battery.
Plug into shore power to keep the refer working.
Many inverter/chargers do not work without a battery connected. Post make and model of converter/charger or inverter/charger for better advice.
__________________
Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
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10-06-2024, 10:20 AM
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#9
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Member
Texas Boomers Club
Join Date: Apr 2020
Posts: 38
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Quote:
Originally Posted by Persistent
Most modern converter/chargers will work without a battery connected. That will provide the refrigerator with 12 volt power to controls.
Post make and model of converter/charger for better advice.
Follow battery manufacturer's instructions for storing the lithium battery. Disconnect the battery.
Plug into shore power to keep the refer working.
Many inverter/chargers do not work without a battery connected. Post make and model of converter/charger or inverter/charger for better advice.
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my converter/chg is a Parallax Series 7300. Inverter/chg is a Xantrex Freedom 458, set for AGM. To disconnect the batts, I plan to remove the neg terminal from the smart shunt. i am expecting the fridge control panel to go dark when i disconnect. will fridge operate under those conditions? TIA
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10-06-2024, 10:30 AM
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#10
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Senior Member
Join Date: Mar 2024
Location: Bohemia NY
Posts: 1,984
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Quote:
Originally Posted by budzini
my converter/chg is a Parallax Series 7300. Inverter/chg is a Xantrex Freedom 458, set for AGM. To disconnect the batts, I plan to remove the neg terminal from the smart shunt. i am expecting the fridge control panel to go dark when i disconnect. will fridge operate under those conditions? TIA
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Are you using both the Xantrex inverter/charger and the Parrellax? Why? That is a redundancy that will also provide conflicts in the charging profile. Get rid of the Parrellax.
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Dennis
Bohemia NY
2008 Nimbus 342 SE Carlyle
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10-06-2024, 10:47 AM
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#11
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Senior Member
Join Date: Sep 2020
Location: Shrewsbury
Posts: 449
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Quote:
Originally Posted by SteveJ.
Lithiums do not like to be floated at 100%. If you're charger has the ability to adjust the float set it to 13.3or 13.2 and leave the batteries connected. This will still provide power for the fridge and other loads but will keep the batteries at a less harmful charge level.
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This is what I do. My converter can be set to output 13.2 V so I just leave the coach plugged in and the LIFEPO batteries stay about 60% charged. I've done this for the last 4 years with no issues. I don't leave my fridge running but certainly could without any impact on the batteries.
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retired USCG aviator
2020 Jayco Greyhawk 29MV/2021 MINI Cooper toad
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10-06-2024, 01:00 PM
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#12
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Member
Texas Boomers Club
Join Date: Apr 2020
Posts: 38
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Quote:
Originally Posted by dvspl
This is what I do. My converter can be set to output 13.2 V so I just leave the coach plugged in and the LIFEPO batteries stay about 60% charged. I've done this for the last 4 years with no issues. I don't leave my fridge running but certainly could without any impact on the batteries.
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Like your suggestion. From what i can tell, however, from my converter, i have no options for settings. Will look closer. Thx
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10-07-2024, 08:10 AM
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#13
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Senior Member
Join Date: Nov 2018
Location: Beaver Dam, Wisconsin
Posts: 5,897
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Quote:
Originally Posted by budzini
my converter/chg is a Parallax Series 7300. Inverter/chg is a Xantrex Freedom 458, set for AGM. To disconnect the batts, I plan to remove the neg terminal from the smart shunt. i am expecting the fridge control panel to go dark when i disconnect. will fridge operate under those conditions? TIA
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Parallax Series 7300
According to the Parallax manual, it will power the refrigerator while the battery is disconnected. 120 volt shore power is required. See page one of the manual.
http://parallaxpower.com/wp-content/...ners_guide.pdf
The Parallax will charge at 13.8 volts. That is enough to charge a lithium battery. It may not be enough to internally balance lithium battery cells. See battery specifications for balancing specifications.
Of course if the Parallax converter was disconnected when the Xantrex was installed, it will not power the refrigerator from 120 volt shore power.
https://parallaxpower.com/extras/archived-tech-docs/
Xantrex Freedom 458
Of course the Xantrex will not invert 12 volts to 120 volts without battery power.
I could not find a place in the manual that said it would convert 120 volts to 12 volts without a battery connected.
Test it to see.
The Xantrex will charge a lithium battery. Be sure to disconnect the battery temperature sensor. It will probably not balance the internal lithium cells.
https://xantrex.com/wp-content/uploa...ers-Manual.pdf
__________________
Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
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10-07-2024, 03:13 PM
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#14
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Member
Texas Boomers Club
Join Date: Apr 2020
Posts: 38
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Quote:
Originally Posted by Persistent
Parallax Series 7300
According to the Parallax manual, it will power the refrigerator while the battery is disconnected. 120 volt shore power is required. See page one of the manual.
http://parallaxpower.com/wp-content/...ners_guide.pdf
The Parallax will charge at 13.8 volts. That is enough to charge a lithium battery. It may not be enough to internally balance lithium battery cells. See battery specifications for balancing specifications.
Of course if the Parallax converter was disconnected when the Xantrex was installed, it will not power the refrigerator from 120 volt shore power.
https://parallaxpower.com/extras/archived-tech-docs/
Xantrex Freedom 458
Of course the Xantrex will not invert 12 volts to 120 volts without battery power.
I could not find a place in the manual that said it would convert 120 volts to 12 volts without a battery connected.
Test it to see.
The Xantrex will charge a lithium battery. Be sure to disconnect the battery temperature sensor. It will probably not balance the internal lithium cells.
https://xantrex.com/wp-content/uploa...ers-Manual.pdf
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Thanks Paul. After further searching i found where Parallax will run the fridge with batts disconnected. Para is still operational. I plan to drop the SOC of the batts to about 60%, disconnect from the rig and let them sit, let the Xantrex provide 120V for dehumidifier, and let the Parallax run the fridge. Best laid plans. Will update. Will chk the balance when i unpack for Feb trip from VA to CA.
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