This post may cause some eye-rolls, but Im willing to risk looking foolish by explaining my own shortcomings in understanding if it might help other forum readers. Until recently, I *thought* I understood why bottom-balancing was relevant, but thought it was appropriate only for EVs, not RE systems, due to differences in usage patterns. Yesterday I encountered a reason to change my mind.
I occasionally find time to watch some of the archived EVTV episodes by Jack Rickard. One episode -- I am pretty sure I chose it because SunKing specifically mentioned it on this forum -- discusses why bottom balancing LiFePO4 packs is best. Many here already advocate this, but the video explained it a little differently. There is also a demonstration involving wooden sticks that, I must say, helped me visualize the situation.
Mr. Rickards argument is built upon the assertion that LFP cells are much more tolerant of over-charging than over-discharging. He states (emphatically) that he has only ever killed a cell by over-discharging, claiming they tolerate significant over-charging without degradation. He also cites the early death of cells in three separate, carefully top-balanced, EV packs as compelling evidence that top-balancing (and shunt-based balancing chargers) are not satisfactory. However, the video is from Nov. 13, 2009. Id like to get some comments from the experienced folks here on the validity of that decade-old statement.
If it is true, the motivation for top-balancing an RE install disappears. While an RE system doesnt get *regularly* cycled to empty like an EV does, that battery capacity is nonetheless there for a reason, and some days it will surely get used. When circumstances do dictate a full discharge (emergency, freak weather, generator failure), the motivation to fully discharge an RE system is greater than with an EV because it's your whole house that is going offline, not just a car. This tendency to fully-discharge is also higher if your RE installation is on an RV (as mine is). While the battery pack does get taken to "full" and held there almost-daily, this allegedly presents little risk to the cells.
I am therefore considering re-balancing my pack to the bottom, but that is predicated entirely upon Mr. Rickards statement about the relative risks of over-charge vs. over-discharge in real-world applications. Since 2009, has this been proven or disproven?
The video I mention above can be found at (near the bottom):
- Jerud
------------------------------------------------------------
Please excuse the infantile punctuation; forum software doesnt like MacOS ; )
1220W array / 1000Ah LFP house bank
MidniteSolar Classic, Magnum MS2812
ME-RC, Trimetric, and JLD404
Yep, made some bad design decisions but learned my lesson and now making the best of it
Full-time 100% electric boondocking (no propane, no genny) since 2015
2001 Fleetwood Prowler 5th wheel 25 foot, self-rebuilt
I occasionally find time to watch some of the archived EVTV episodes by Jack Rickard. One episode -- I am pretty sure I chose it because SunKing specifically mentioned it on this forum -- discusses why bottom balancing LiFePO4 packs is best. Many here already advocate this, but the video explained it a little differently. There is also a demonstration involving wooden sticks that, I must say, helped me visualize the situation.
Mr. Rickards argument is built upon the assertion that LFP cells are much more tolerant of over-charging than over-discharging. He states (emphatically) that he has only ever killed a cell by over-discharging, claiming they tolerate significant over-charging without degradation. He also cites the early death of cells in three separate, carefully top-balanced, EV packs as compelling evidence that top-balancing (and shunt-based balancing chargers) are not satisfactory. However, the video is from Nov. 13, 2009. Id like to get some comments from the experienced folks here on the validity of that decade-old statement.
If it is true, the motivation for top-balancing an RE install disappears. While an RE system doesnt get *regularly* cycled to empty like an EV does, that battery capacity is nonetheless there for a reason, and some days it will surely get used. When circumstances do dictate a full discharge (emergency, freak weather, generator failure), the motivation to fully discharge an RE system is greater than with an EV because it's your whole house that is going offline, not just a car. This tendency to fully-discharge is also higher if your RE installation is on an RV (as mine is). While the battery pack does get taken to "full" and held there almost-daily, this allegedly presents little risk to the cells.
I am therefore considering re-balancing my pack to the bottom, but that is predicated entirely upon Mr. Rickards statement about the relative risks of over-charge vs. over-discharge in real-world applications. Since 2009, has this been proven or disproven?
The video I mention above can be found at (near the bottom):
- Jerud
------------------------------------------------------------
Please excuse the infantile punctuation; forum software doesnt like MacOS ; )
1220W array / 1000Ah LFP house bank
MidniteSolar Classic, Magnum MS2812
ME-RC, Trimetric, and JLD404
Yep, made some bad design decisions but learned my lesson and now making the best of it
Full-time 100% electric boondocking (no propane, no genny) since 2015
2001 Fleetwood Prowler 5th wheel 25 foot, self-rebuilt
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