Quote:
Originally Posted by BobG
Here is an interesting thing. When I pull up the battery history it shows 27 cycles and 1 full discharge. The full discharge was last July when I checked the capacity of the battery. It is rated 170Ah. Although the history only shows 27 cycles, the batteries have been operating for many more cycles than that.
Except for the last few days I have not been on shore power since some time in December. The batteries have been in constant use and during the past few months they have been taking some pretty big hits from the air conditioner and electric teakettle. Charging has been from solar only.
Obviously there have been more than 27 cycles, some down to 20% SOC yet the Victron SmartShunt says 27 cycles. It looks to me that it somehow converts all the partial cycles to full cycle equivalents?
It doesn't really matter to me but is kinda interesting. I guess I can compare the cycles the shunt logs against the number of cycles the battery manufacturer claims and maybe know about how much life is left.
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Yes, the Thornwood does something similar. Much to learn about what it calls a cycle and a full discharge.
To your point, our trailer sits a lot more than it gets used so has many small daily cycles. I want to believe these daily small discharge/recharge cycles are insignificant WRT degradation but I admit my ignorance.
I suspect the spec'd battery cycle life assumes "full" discharge cycles and real life is too complicated for mere mortals... lots of assumptions and calculus for sure. Basically, how many mini-cycles is equivalent to one full cycle? And the answer will clearly be different for every battery chemistry.... probably even for every unique battery construction.
I also guess an empirical estimate of charge behavior (ie delta AH/delta V) over time is how the SOH algorithms might work.
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