One of the reasons I chose the t:slim over other options was the rechargeable battery. I use the wall charger, the USB charger on a laptop, a car charger, and a Anker 6000 mA battery pack that itself is rechargeable by any of the three methods above.
While I don’t have a specific number, the 6,000 mA Anker will charge a phone and my t:Slim several times on a single charge.
While I do not live in So Florida, I do live in CA where a major earthquake COULD leave us without power for a week or more and, more recently, our erstwhile utility could shut off power for several days.
Moreover, I’ve been on a liveaboard dive boat for 10 days and cross country skiing in Yellowstone where a generator MAY run 1-2 hours per day for 8-10 days. Rechargeable battery packs are GREAT, in my humble view.
A couple of final comments: only buy QUALITY Li-ion battery packs. I had a cheapo unit that got uncomfortably warm once during charging the battery pack. Fortunately, I noticed it before something bad happened … unplugged it immediately and took it outside to let it cool and never used it again.
Your car battery is a REALLY BIG battery: on the order of 80,000-100,000 mA hours which could recharge your battery pack a number of times even if your car isn’t running or is out of gas. To readily use this, of course, you need a “cigarette lighter outlet” in your car that provides battery power even when the car is not turned on. Some cars have this feature, some cars can be configured to behave this way, and some do not have this feature.
When it comes to recharging my pump, I like options, backups, redundancy, and backups for my redundancy. At this point in time, a USB connector is your best friend.