| Re: Li batteries [message #366447 is a reply to message #366428] |
Thu, 02 September 2021 07:42   |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma:
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Senior Member |
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Tom,
Here is an excellent article about LiFePO4 (LFP) batteries. It's written for boaters, but it applies to RV's as well. Its a few pages, so get a coffee before you start.
https://marinehowto.com/lifepo4-batteries-on-boats/
An LFP battery has a very low internal resistance and needs to be charged with a constant current, then finished with a constant voltage, then its charges. Since LFP has a very low self-discharge, there is no "float" charge required... but since we have equipment connected to the house battery (fans etc), a float charge of about 13.5V is Ok as long as it isn't connected during storage.
Automotive alternators (until recently) are a constant voltage output, so a LFP battery in a lower state of charge will suck all the current the alternator can deliver and quickly burn it out. A BIM is like a long cycle PWM regulator. It connects the LFP battery to the chassis for about 15 minutes, then disconnects for about 20 minutes to let the alternator cool down.
I went with a DC-DC charger instead. It takes the DC power from the chassis (alternator) and converts it to the proper Constant Current/ Constant Voltage/ Float voltage charge curve that the LFP battery requires for longest life.
JWID
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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