individual cell vs. putting smaller battery packs together

Sad story: I bought an electric bike here in Beijing about 2 months ago. 2 days ago it was stolen. Partly my fault - I usually haul the battery up with me to my apartment every night, but during this time of the year almost any kind of ebikes are stolen. I have found a way to chain another bike to a substantial pole - I think that is going to prevent another theft. I am looking at buying a second hand bike and upgrading it. The first upgrade I want to do is the battery. It currently has a 48v sla battery - I think it is 12 amp.

My question: It is possible to build a battery using battery packs that have already been assembled, i.e. 8 x (12v,10amp packs) to give me a 48v 20 amp pack. What are the advantages of using a pack that is built cell by cell, vs, battery pack by battery pack? keep the bms in mind.

Yes it is possable. Many around here have done it. The main considerations are these:

You need to use the same kind of battery's when mixing many packs to make one. SLA's to SLA's. Lipo to lipo. LiFeP4 to LiFePO4 etc.

The condition and age of the cells should be of the same condition. Do not mix old and new batteries.

What kind of batteries were you considering mixing?

Thanks! I have just finished reading a lengthy thread on battery building and feel I am up to it. I have done some spot welding, soldering, etc.before. now it is time to put everything together. I was looking at 18650s from Panasonic but I am open to suggestions. I am thinking of building a small pack first to shake the bugs out and then proceed to a 60v 40a pack.

Ok. If all your 18650 batteries are new. And they are all have the same "C" rating. And they all have the charge value (3.4v or something close) then you should be able to combine them with out much problem.

If the cells have different "C" ratings, you might end up with problems.

Eventually I will put new LiFes but now I would like to add more SLA's to give it more amps.

I would like to first build a 30 amp 48v battery. then after 3 months of refurbishing the scooter, I would like to rebuild the battery pack so that it has 72v and 30amps. I plan to use identical batteries from the same vendor. but I need something to get me around in those three months.