12 v to 48 volt dc boost converter 300 watt

Why? Will it provide enough capacity? You are much better off using 4 smaller batteries in series.

Bob

 

Yes it is technically possible, but not very practical. I hate depending on Chinese product specs (which are sometimes wrong) but this might work:
https://www.ebay.com/itm/uxcell-Vol...o-DC48V-10A-480W-Car-Truck-Boost/333124189559

Due to the wattage this would require the boost converter to handle close to 30A input current, accounting for some inefficiency and rounding up, plus you will not get good battery runtime from a 30A drain rate unless it is a very large and heavy battery.

You could construct a parallel series Li-Ion battery pack which handles 30A acceptably with lower size and weight, but it and the charger for it will be much more expensive, and you could just construct the pack for 48V instead. I suppose this is why you are trying to do it differently than just using the battery pack and charger designed for the vehicle?

300W isn't much of a motor for an adult sized vehicle, you probably want the far lighter weight Li-Ion 48V pack to help with speed, range, size, and if it's a bicycle to reduce the center of gravity and wear on the tires. A big 12V lead acid battery might not even be safe to mount on a bicycle frame due to the weight. If you wanted to just use a small 12V lead acid battery, it will have disappointing results.