The traditional lead-acid forklift battery is a tried-and-tested technology that is still being improved, and it's still the most common source of power for electric forklifts. However, there's still not a solution for the regular maintenance these batteries require to keep working at their best.
For one, lead-acid batteries need to be topped up with water regularly. When this type of battery is charged, the fluid inside it dissociates into oxygen and hydrogen gas, which results in the fluid level dropping. If it drops enough, the lead plates are exposed to air, and begin to oxidise. This can cause permanent battery damage, and it's one of the main reasons that batteries become defective early.