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LiFePo4 charging


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#61 craig333

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Posted 04 September 2019 - 10:37 PM

So if I read this correctly, I should plan on a 100ah LifeP04 being more a 90ah battery in order to keep it happy. Not really a big deal as I already assume my agm's are half their capacity (still in the 50% crowd). Still should be plenty of power for a week of no charging (at my assumed usage rate of 10-15% per day). 


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#62 rando

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Posted 04 September 2019 - 10:43 PM

You may need to tune these voltages a little for your particular battery, but your are correct, the whole point is not to leave the battery fully charged, at least while you are not actively using the camper.    If you set the float at 13.2, it will bleed the battery down to 13.2, then the solar panel will pick up the load.  Based on the power stream data, much above 13.2 any you will end up charging your battery back up to 100%. 

 

Honestly, this is probably all pedantry, and you will get plenty of life if you leave the voltages at the standard lead acid settings.  Most of us will likely have sold our campers before we hit even a reduced cycle life. 


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#63 rando

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Posted 04 September 2019 - 10:50 PM

So if I read this correctly, I should plan on a 100ah LifeP04 being more a 90ah battery in order to keep it happy. Not really a big deal as I already assume my agm's are half their capacity (still in the 50% crowd). Still should be plenty of power for a week of no charging (at my assumed usage rate of 10-15% per day). 

 

 

Pulling out 100Ah now and then is no big deal.  It is still 600 cycles at 100% DOD. Even if you are doing that every single week, it will still last over 10 years. 


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#64 buckland

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Posted 04 September 2019 - 11:24 PM

yup .. It will no doubt "see me out" ... Fun though learning the new stuff on how it works. The weight savings alone allow for a case of beer!


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#65 ClimberRob

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Posted 05 September 2019 - 12:43 AM

Any ideas about "floating" a battery come from FLA/AGM/GEL batteries, which lose voltage at rest. Lithium batteries don't need a "float" stage. If you want to power your electronics off of solar or your AC charger, etc., that's fine, but you would ideally just charge your LiFePo4 battery fully, then shut off the charge current (which is handled by the BMS on most batteries).

 

Drawing your battery down 100 AH really isn't a big deal. How many times have you done that on your laptop or phone?


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#66 Stokeme

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Posted 13 September 2019 - 05:15 PM

Just wanted to follow up with a quick discussion I had yesterday with the lead tech, formally w/StarkPower, now w/TorquePower. It basically mirrors Rando’s post #51 & adds some support to a preferred, lesssr SOC (not critical) when in use & also not in use. As a perceived drop in replacement for LA the “retail” V parameters are stated for 99-100% SOC. It would be a little less stressful, when in active use, & non use more so, to keep full SOC a little, or more, below this %.

When in use he recommended absorption V be set@13.8-14.0. Cell balancing with passive equalization should take about 30 minutes after reaching the highest V setting. So, he recommended setting absorption time to 45-60 minutes. Float V set to 13.5. He estimated for my Batteries this would result in ~95% full SOC. Settings were based on my average usage of 8%(low)-15%(high)/day of my 150Ah capacity. My controller had been set to 14.4 & 13.8 respectively. Time 6hr. This was the auto set for LFP4 with my 100/30 Smart Victron. When not in use, he recommended absorption V be @13.6-13.8, float @13.2-13.5. Monitor how the battery responds to the V setting.

An added note: re min/max temp thresholds. I am not that concerned about the high of ~150F, it seems to me extreme. For low temp of ~20F, I live in the NorCal SF Bay Area. Frigid Storage for me is not a concern. I will be out having adventures in 20F weather, but my Camper will never likely be under 40F. I have not purchased the Victron temp charge control monitor yet. I was told that the battery will generate a slight bit of heat as it discharges in very cold temp, which is safe, (cannot be safely charged) which helps a little bit with the internal temp. I would be curious if anyone has experienced low temp threshold issues with their Battery.

Lastly he conveyed that SOC was less critical to long Battery life overall as compared to the number of times the Battery is drained below 80%. This would limit my Battery to ~2,000 cycles, as opposed to ~3,000-4,000 cycles if kept above this drainage parameter.

Edited by Stokeme, 13 September 2019 - 05:30 PM.

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