When the battery was received by the shipper it had about 30% charge remaining. I plugged it in and within less than two hours it was at 100% charge. Then I tested the new CPAP and battery for two nights at home. Perfect. Recharged the battery to full charge and left for an off-grid tent camping trip. I've used it for two nights off-grid in fairly mild evening temps. After two days without a recharge, my Breas Z2 has used only 22% of the charge for 15.5 hours sleep time.
As an industrial design...