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Old 10-10-2022, 12:01 AM   #1
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Brand: Thor Motor Coach
Model: Windsport 29m
State: North Carolina
Posts: 521
THOR #9553
Change to LiFePO4 Considerations

Quote:
Originally Posted by 16ACE27 View Post
You mean Renogy battery monitor?



Why would the shunt need to take AHs from the chassis battery into account? They're not coming out of the house batteries.

I have the Renogy battery monitor above and it always displays the exact status of my two LiFePO4 house batteries.
I'm not a electrical genius so when I saw that you use the Lithium batts I wanted to ask you about switching my 3 flooded NAPA RV/Marine batteries in the battery box of my 2018 Thor Windsport 29m. I want to know if the system that came in this coach from the factory will work with the Renogy LiFeP04 batteries. More importantly, will my system fully charge them. I guess I could call Renogy and tell them what I have but how can you advise me going from flooded to Lithium. I converted my Norcold absorbtion fridge to a 12v system with a compressor from JC Refridgeration and it takes a lot more amps so I added a 3rd battery. It lasts over night but 3 batts are very heavy and I think the right pieces would be much better of a system!!!

Thanks; Bob Trice

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Old 10-10-2022, 12:25 AM   #2
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Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 14,128
THOR #7035
Hey Bob - I moved your post to its own thread to keep from hijacking the other thread.

You will need a LiFePO4 charger to fully charge the new batteries on SP. It is unlikely that your converter will have the ability to charge the LiFePO4 batteries properly. A FLA specific charger will only keep the lithium batteries charged to 60 - 70%, which is fine for storage, but you do want to charge them fully (100%) before boondocking. This can be done by the engine alternator through the BIM or BIRD or by using a LiFePO4 specific charger such as this 20 amp charger:
https://www.amazon.com/gp/product/B074X1QK2R

But if you leave that lithium charger connected you may overcharge the chassis FLA battery though the BIM/BIRD. You can install a simple switch in the control line for the BIM or Trombetta to disable/enable this battery bank connection.

Charging from the engine alternator can be a heavy load on the alternator charging the lithium batteries, especially if they are low to start. Replacing your current BIRD/BIM with a Li-BIM prevents overloading the alternator and shortening its life. It also helps prevent overcharging the chassis battery when charging the LiFePO4 batteries on SP.
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Old 10-10-2022, 04:28 AM   #3
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Brand: Thor Motor Coach
Model: Windsport 29m
State: North Carolina
Posts: 521
THOR #9553
Quote:
Originally Posted by 16ACE27 View Post
You mean Renogy battery monitor?



Why would the shunt need to take AHs from the chassis battery into account? They're not coming out of the house batteries.

I have the Renogy battery monitor above and it always displays the exact status of my two LiFePO4 house batteries.
Would you mind telling me How many Renogy batteries I need to provide several days of power to run my 2018 Thor Windsport 29m. I went with a 12v fridge that draws 7.5 amps at start up and I need enough to go at least 2 days boondocking. I don't think the charging system I currently have will work and provide 100% charge. You sent me a email but can you tell me please every component I need to get to do a proper install. I now have 3 NAPA RV/Marine group 27 flooded at 125 Ah I think and I can go overnight but it drops to 12.3 or 4 a lot and below 12.2 will damage them I've read??? Thanks for your help with this brother!!! Bob Trice

You sent me a email on this but can you tell me how many lithium batteries I need to use to go several days boondocking with a 12v fridge that uses 7.5 amps start up and will drop my volts to 12.3 or 4 overnight. Below 12.2 I'm told can cause damage to the batteries. My 2018 Windsport 29m has 3 group 27 125Ah flooded batts and they are heavy!!! The charging system as is I don't think will charge them 100%. Thanks for your help with this my brother; Bob Trice
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Old 10-10-2022, 05:41 AM   #4
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Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 14,128
THOR #7035
Your NAPA group 27 batteries are only about 90 AH each when new; so 3 gives you 270 AH, of which only 135 AH is usable in a FLA battery (50%).

LiFePO4 batteries come in various sizes but a common replacement is a group 29 size at 100 AH each. 2 of those will exceed what you have now in usable capacity.

Fridge starting current is not used to calculate available runtime. There are too many variables involved:

How many is a "few days"?
Ambient temperature?
Running current?
Duty cycle which depends on ambient temperature, fridge insulation, and door opening cycles.
What other loads are drawn from the battery bank?

to answer your question with any degree of accuracy.
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Old 10-10-2022, 12:20 PM   #5
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Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
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THOR #20289
If you are going to install lithium batteries you might as well do it right. As ACE has noted, it will take a new charger and possibly a new BIM as well as the batteries.

But first install a shunt based battery monitor and collect some good data. The Renogy one shown above is a good one. A cheaper but serviceable one is sold on Amazon under the name QWork for about $48 including all connecting cables.

After you have some good usage data, we can figure the amount of batteries you will need.

David
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