Proprietary batteries a problem?
 

Where I live in SE asia, they sell electric bikes, and my understanding is that the batteries are proprietary. Some of these bikes are made by companies I never heard of. If the company goes out of business, where do you get a new battery when your battery dies? Are electric bike batteries interchangeable, even if they come from different manufacturers? Is this a serious concern?

I don't think there's much standardization between ebike batteries in North America. The technology is changing so fast what was leading edge last month is obsolete this month. What most folks do here is rebuild the battery pack or simply start over with new cells and custom build a replacement pack. After voltage/current demands have been met, it's a just a matter of choice regarding chemistry, capacity and cost. Plus your own technical capability, of course.

As they age - I've been finding more and more nice eBikes with bad batteries for sale. In many cases the motors/controllers are quite advanced. technical folk can grab 'em cheap and make a new battery pack - have a nice eBike. With today's battery chemistry choices they're often better than when the ebike left the factory.

Or go low-tech and use SLA batteries.

okay some of this is too technical for me. Are you saying that you can always somehow make a new battery, or find someone who can make one for you (maybe even a better one) if you're not technically inclined, so it's not a concern that the bike manufacturer might disappear?

How many charges do you get out of a new battery before it dies?

Must battery packs are made up of a number of 12 volt battery packs. All ya have to do is open the battery case, take out the 2, 3 or 4 12 volt batteries that are inside and replace them with something SUITABLE. Please note, you must replace them with something suitable. Not all types of batteries can be used in any battery pack. If you want to change the type of battery chemistry you MAY have to change the electronics in the battery or even the charger.

The number of charges you can get from a battery depends on the chemistry. SLA's usually only last 200-300 charges. I have seen Li-ion advertising 2000-3000 charges. Another issue is that as the battery ages it will give you less and less power, especially the SLA type.