Thanks for your thoughtful suggestions.
In my limited knowledge of electronics incl LA batteries [=LAB], I am of the understanding that the life of LABs is dependent on their health, which is worn out by few factors
- State of Charge [ low = shorter battery life ]
- Number of (deep) discharge cycles [ high = shorter battery life ]
- (Sustained storage at) Temperature [ low = short battery life ]
- Time spent at deeply discharged state [ more = shorter battery life ]
With that in mind, and information from Russell Graves at
Syonyk's Project Blog: Tesla Model S 12V Battery Analysis ( full disclosure, I did exchange a few emails with him on this topic) it appears that the 12V in a Tesla MS goes through multiple deep cycles many times a day and is then topped by the Traction battery [TB]
Personally, for me, the above combined with the fact that my MS sits in a non heated garage [ today the temperature was negative 10 degree Celsius in my garage ] and is driven an average of 1x/week in winter, it makes sense to me to hook the 12V Batt to a external Charger with 2
potential advantages:
- for the 12V Battery: If the external charger can supply all the amps for whatever drains it, this will decrease number of discharge / charge cycles, and it cannot supply all the power, it'll lower the depth to which it discharge. In case of latter, it'll take less time for TB to bring it to optimal voltage and this will reduce the amt of time 12V spends at lower level of charge. All of these will lead to less TB discharge
- Lessen Vampire Drain on the main TB and hence preserve range
some one made an argument that one could just 'plug the car in' and let the car do its thing, which only solves [2] above and though acceptable but does not prevent the discharge cycles on the 12V.
I plan to keep my MS for as long as I can, so I see no disadvantage to hook it to a Battery Tender. After much research I got a NOCO 7.2Amp unit.
If anyone had any critique on above or ideas on how to measure TB drain automatically or to see if this intervention had any outcome with hard data, I am open to suggestions and a constructive discussion