It is clearly important that you purchase the most suitable size battery powered toy vehicle for your kids or grand kids. 12v batterry vehicles make great Electric Gifts for Children which are usually suitable for ages 3 years to 7 years of age. However, often the power required is dependent upon the weight of the driver. Our customers will clearly see on all our kids electric toy product descriptions state the suitable age ranges for each kids ride on toy. As kids ride-on toy batteries range from 6v to 48v the battery size is all about the amount of speed and power the vehicle will be capable of achieving. If your kid or grand-kid is much smaller of larger than the average child for their age then you would need to use your personal knowledge as to whether it may be better to buy a kids electric toy that is a larger size than recomended or indeed smaller size? Potential customers can always email our dedicated customer service team us at sales@kidselectriccars.co.uk if you have any questions you may like us to answer about 6v electric toys for kids which make great Electric Gifts for Children