LiFePo4 lithium battery charging questions
TL DR – I have some questions related to charging 12V LiFePo4 lithium batteries:
*How to best use my solar to charge batteries?
*Assuming I usually keep the lithium batteries at a partial SOC, what if I want occasional 100% SOC?
*What about charging from my tow vehicle?
*What about charging with OEM converter?
Full version:
Hello all. It has been a long time since I've posted here! Current project, my 10-year-old quick and dirty wiring job for inverter install on my TT is due for an overhaul. My exposed-to-the-elements inverter wiring needs replacing along with the 2 x 6V GC batteries.
Here is what I have now:
*2 x 6V GC batteries in series (~200 Ah total)
*2 x 140 12V solar panels mounted fixed and flat
*Morningstar Tristar PWM controller
*1500 watt PSW inverter
*OEM WFCO converter (55 amp)
I’m thinking that since I want to replace the batteries and some wiring, I want to relocate the batteries from on the tongue to the pass through storage alongside the other electrical components. So I am considering a switch to a single lithium (LiFePo4) 12V battery 100Ah. Current top candidates are Renogy, Battleborn, and Dakota. I am contemplating my charging options if I do this swap.
How to best use my solar to charge batteries? The Morningstar controller is fully programmable and I downloaded a suggested lithium battery charging profile from their website. It relies on the concept of never bringing the lithium battery to 100% SOC as this can be stressful to the lithium battery. From what I’ve learned, lithium works great at partial charge levels vs FLA which should be kept at 100% SOC as much as possible for best health. So the Morningstar config actually does away with the voltage regulating features and changes it to an on-off switching controller via high voltage disconnect (HVD) and reconnect (HVDR) in order to avoid any absorption or float charging. The HVD is 13.8V and HVDR is 13.3V. So controller is in bulk charging mode until the HVD setpoint of 13.8V is reached, then charging is stopped (disconnected) until the voltage drops below 13.3V at which time the charging turns on again and this cycle repeats indefinitely. They say this should get a lithium battery to ~90% SOC and no further, allowing for many cycles without stressing the battery by bringing it to 100% SOC.
But what if I want occasional 100% SOC? My thought is if we’re heading out camping for the long weekend, then I do want to recharge to 100% just prior to and if possible during each camp day. It seems like a few of the lithium battery manuals say that FLA charging profiles that can reach 14.4V and an absorption phase will work fine to fully charge. I think I can put together a “while camping” charging profile based around 14.4V absorption setpoint to accomplish this. 13.3V float?
What about charging from my tow vehicle? My tow vehicle delivers 12V via the trailer plug. No upgrades in wiring or anything there, just whatever the OEM setup is for the 7-pin trailer connector. But I confirm that it brings the trailer battery voltage up to the alternator voltage of 14.2-14.4V. Since this is on the upper end of lithium charging voltage, and considering that I probably don’t want the alternator trying to push 14.4V indefinitely while driving, should I be disconnecting this charging source? Or maybe consider it sort of a topping off charge for the typical 1-2 hr drive to the camp spot?
What about charging with OEM converter? My OEM converter is a WFCO 55 amp model. I have one time ever seen it charge at 14.4V, every other time I have ever used it I see 13.6V. I usually have it switched off via the breaker panel and let solar do the work. I expect I would continue this practice. But it seems like I could use it if I wanted and assuming it continues to only charge at 13.6V, it should be fine for partial charging?
Thanks for any feedback!!
Ed
*How to best use my solar to charge batteries?
*Assuming I usually keep the lithium batteries at a partial SOC, what if I want occasional 100% SOC?
*What about charging from my tow vehicle?
*What about charging with OEM converter?
Full version:
Hello all. It has been a long time since I've posted here! Current project, my 10-year-old quick and dirty wiring job for inverter install on my TT is due for an overhaul. My exposed-to-the-elements inverter wiring needs replacing along with the 2 x 6V GC batteries.
Here is what I have now:
*2 x 6V GC batteries in series (~200 Ah total)
*2 x 140 12V solar panels mounted fixed and flat
*Morningstar Tristar PWM controller
*1500 watt PSW inverter
*OEM WFCO converter (55 amp)
I’m thinking that since I want to replace the batteries and some wiring, I want to relocate the batteries from on the tongue to the pass through storage alongside the other electrical components. So I am considering a switch to a single lithium (LiFePo4) 12V battery 100Ah. Current top candidates are Renogy, Battleborn, and Dakota. I am contemplating my charging options if I do this swap.
How to best use my solar to charge batteries? The Morningstar controller is fully programmable and I downloaded a suggested lithium battery charging profile from their website. It relies on the concept of never bringing the lithium battery to 100% SOC as this can be stressful to the lithium battery. From what I’ve learned, lithium works great at partial charge levels vs FLA which should be kept at 100% SOC as much as possible for best health. So the Morningstar config actually does away with the voltage regulating features and changes it to an on-off switching controller via high voltage disconnect (HVD) and reconnect (HVDR) in order to avoid any absorption or float charging. The HVD is 13.8V and HVDR is 13.3V. So controller is in bulk charging mode until the HVD setpoint of 13.8V is reached, then charging is stopped (disconnected) until the voltage drops below 13.3V at which time the charging turns on again and this cycle repeats indefinitely. They say this should get a lithium battery to ~90% SOC and no further, allowing for many cycles without stressing the battery by bringing it to 100% SOC.
But what if I want occasional 100% SOC? My thought is if we’re heading out camping for the long weekend, then I do want to recharge to 100% just prior to and if possible during each camp day. It seems like a few of the lithium battery manuals say that FLA charging profiles that can reach 14.4V and an absorption phase will work fine to fully charge. I think I can put together a “while camping” charging profile based around 14.4V absorption setpoint to accomplish this. 13.3V float?
What about charging from my tow vehicle? My tow vehicle delivers 12V via the trailer plug. No upgrades in wiring or anything there, just whatever the OEM setup is for the 7-pin trailer connector. But I confirm that it brings the trailer battery voltage up to the alternator voltage of 14.2-14.4V. Since this is on the upper end of lithium charging voltage, and considering that I probably don’t want the alternator trying to push 14.4V indefinitely while driving, should I be disconnecting this charging source? Or maybe consider it sort of a topping off charge for the typical 1-2 hr drive to the camp spot?
What about charging with OEM converter? My OEM converter is a WFCO 55 amp model. I have one time ever seen it charge at 14.4V, every other time I have ever used it I see 13.6V. I usually have it switched off via the breaker panel and let solar do the work. I expect I would continue this practice. But it seems like I could use it if I wanted and assuming it continues to only charge at 13.6V, it should be fine for partial charging?
Thanks for any feedback!!
Ed
