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I could not find any info on this so I am posting it here. Does anybody know how well rechargeable CR123 batteries perform in the new Apex Pro model? I am looking to purchase some rechargeables since the throw aways are $10 for 2 of them but I don't want to waste my money on them if they are going to drain much faster than normal disposables would.

The "disposables" are primary batteries.
The rechargeables are 4.2 volts not 3 volts like primary batteries.
You should be okay but your run times will be shorter due to two tings:
1. lower capacity
2. protection circuit cutting out at 2.75 volts per cell.
DO NOT USE unprotected cells. or at least DO NOT try to recharge unprotected cells that have fallen below 2.75 VDC.

The low capacity of rechargeable lithiums just don't make them very caver-friendly at this point in time.

Your best bet would be to order batteries in bulk instead of buying them in a store.

These people have treated me very well and have good prices (and free shipping): https://www.fenix-store.com/index.php?cPath=53_59

Your other alternative would be to sell the Pro and get the standard Apex that can take rechargeable AA's.

I buy Batterystation 123A batteries for $1.00 or $1.50 ea depending on the quantity.