For Specialized SL owners. Have you bought the bottle battery and is it helpful to you?

[Stefan Mikes]

I’d draw them both all the time. Less load on the small battery

I'd say the parallel discharging is optimal unless you own more than one Range Extender Then you want to equalize the number of recharges on all the batteries.

However, the "Discharge RE first" does not cause any technical issues. Interestingly, the main batery kicks in sometimes to help the RE match the current power demand (not to put too much "stress" on the extra battery).