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It can be hard to wrap your brain around... going with one voltage now and adding more batteries for a higher voltage later will give you greater performance as you upgrade for a sporty off the line feel and you will get less line loss so you will increase range by just a little bit, but it will also require either a higher voltage controller now or one later and it will either require a charger that can be adjusted or buying two...
voltage gives you speed, amperage gives you range, so figure out your speed you want and then increase your range as you can... maybe?
Some people say you can piggy back battery management systems by pairing cells up to give higher amp hours, the risk is if you go with cheap cells, a cheap battery management system or have something fail! if you choose to pair up cells to later get more amp hours then plan in adding fuses and either a meter or an LED system that tells you if you have a single cell go bad, it might seem silly now, but people do have cells go bad and the more you push them the greater that risk is, have new and old cells mixed is pushing what they can do, same with undersizing the pack.
If you want to spend the money and have two battery management systems, one for the first string of batteries you buy and one for the 2n string you buy, then you can save your self a bit of trouble, still having a meter between the two packs to tell you if one is laging is a good idea, but the BMS (battery management system) should keep everything safe and keep one pack from killing the other, the draw back is an over all higher cost compared to paring up cells to share a BMS.
You can of course buy lead acid batteries, but the first set of lead acid batteries is going to be the quickest for a new EV owner to kill, so in 3 years you are going to be buying a new set, at that point you will have paid as much as you would have for lithium and your car is not going to have as good of performance.
Most people I talk to say that when they switch from lead to lithium they see at least a 50% increase in range with the same labeled capacity, with fewer watt hours per mile.
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