I just wanted to thank everyone that replied. I am walking away from this 2014 S deal as I can't seem to get enough answers on the history of the bike. Since the on board chargers seem to the weak point, it would be nice to know if it had been replaced in the last 21K miles. I also realized that I am more interested in a FXS model as the range would be fine with me and would probably like the ergonomics better. If anyone is interested, I'll talk to the guy and see if he is agreeable.
Having a charger that was not replaced or is malfunctioning should not be a deal-breaker. Think further about how you would attempt a repair if the Main Bike Board goes bad? That could be a disaster on an old and new bike alike. In fact, before
AF1Racing opened up their catalog of Zero Motorcycles parts to online ordering there was kind of a grey market for finding dealers who would order parts for customers (or not!) - some dealers who were willing couldn't figure it out and there were warehouse problems for logistics that Zero Motorcycles used in past years repeatedly returning to haunt new parts orders. If you could even get a brand new proprietary part like the Main Bike Board specific to your make and model year it then needs to be programmed and the tools to do so are not for sale. There is no mail order service for getting proprietary Zero Motorcycles parts serviced.
The value proposition here needs to be compared with something that is maintainable.
If you break something on a $4000 Sur Ron X there's a dozen online retailers where you can swap parts; there are no mysterious proprietary parts that will stop you from spending time and money to repair it. Anything specialized needing programming tools for cobbled-together import products out of China like the Sur Ron can be mailed away to get programmed and return-mailed. The same is not true for Zero Motorcycles vehicles, the manufacturer actively prevents owners from obtaining the proprietary repair tools for maintaining and repairing their bikes, and the support through an authorized network of dealers has been rocky at best for most owners I know personally. If your dealer is outstanding and does well you may never have a problem in the first place and wouldn't notice any troubles for 10 years of ownership, but the horror stories begin about dealer service and repair on Zero Motorcycles vehicles and never really end as there are some number of unsatisfactory results even when the manufacturer intervened (which they have done to positive effect a whole lot more then they ought need to) to try to make it right for the owner.
However for something like the Sur Ron X you'd be daft with a deathwish to try and ride that more than a mile or two on interstate highway. The Zero FX is the next level up and is about the minimum you'd want to dabble with over 45mph speeds. For that you have to make some concessions about price and some parts being proprietary and not user replaceable.
So maybe it was good to walk away from a 2014 Zero S? However it could also be the kind of bike if ridden hard that there are well-known problems. It's better for Zero Motorcycles owners to have a bike with well-known problems (anything besides proprietary programmed parts like Main Bike Board, Sevcon motor controller, the motor itself) than a new one on warranty service with mysterious problems and a dealer network that isn't quite taking care of business (or no dealer in your area at all). It would be like having had a test pilot for all those years working for you to find the problems, and then giving you the test bike when you cut their paycheck
Since you're interested in an FX style bike though just have a look for a FX 7.2 and see if that's in your budget. If the charger is bad just remove it and DIY your own better replacement (same could be of course said for the 2014 Zero S but factor that into the price any DIY charging upgrade worth doing is $1000+). It could have been dropped and flipped and so on but if it accelerates without a hiccup it's probably good to go. Get some seat time, and when the 2021 model year is announced see if they have managed to make an improvement to the ZForce battery. The 2013 Zero was offered with a ZForce 8.5 as a larger physical battery similar to what we see on ZF14.0 bikes now. If they can squeeze out an improvement on the ZF7.2 for 2021 at half the mass and half the physical size of the 2013 ZF8.5 it will be a wonderful milestone. An FX ZF8 would be amazing, but the FX ZF7.2 is a fine bike and nothing else really can touch its value proposition as a machine capable of highway speeds.
Say you're not ever needing to go on highway, then it's maybe more sensible to grab a Sur Ron X? It's not a motorcycle but it's also way less dependent on finding a manufacturer authorized dealership that doesn't suck.
The 2014 Zero S might still be interesting at $5k I think it's not a bad value. You need to do some research about a local authorized dealer though, even though Hollywood Electrics maintained the bike and they are in fact excellent it really doesn't matter because they are not the local dealer where you would go to get the bike proprietary stuff serviced.