A friend of mine asked my advice on using cheap car batteries to put together an electric motorcycle. This video about lead acid batteries is pretty helpful in explaining why car batteries are not ideal for energy storage on electric vehicles:
The important thing to pay attention to is the energy density vs. power density comparison. Your typical car battery is built for outputting a large amount of cold cranking amps (CCA) for a brief duration to start your engine. From there it is immediately recharged by your alternator once the car is running. For that reason, the lead plates are very thin. If you ask a car battery to continually discharge over a long period of time to a very high depth of discharge (DOD), you will permanently damage the plates and the battery’s ability to hold energy.
Lead acid batteries are a good way to build an inexpensive electric vehicle, but it’s pretty important to use a deep cycle battery. Odyssey batteries don’t count, either. They are sold as “deep cycle” batteries, but they are absorbed glass mat (AGM) that are even more susceptible to damage from deep discharging. The way to go is golf cart batteries since they are designed with much thicker lead plates to safely discharge a large percentage of their stored energy. The EV community seems to favor batteries from the Trojan Battery Company. Your best bet will be to try and arrange a batch buy at a local dealer since they’ll be really expensive to ship due to weight. Generally speaking, lead acid batteries will give you a much cheaper battery pack compared to lithium ion, but you only get about half the benefits in terms of weight, discharge performance and longevity. They also need constant maintenance in terms of needing to be watered with steam distilled water about once a month. I would recommend doing a lead acid battery EV on a light truck so you can mount the heavy batteries (somewhere in the neighborhood of 1200 extra pounds) between the frame rails or in the bed and because there will be a lower performance expectation. Another thing to keep in mind is that we’re currently able to recycle lead acid batteries very well simply because they’ve been around for a long time.
Source: Engineer Guy Video on YouTube