You aren't supposed to connect LiFePO4 batteries together?

I have two of them connected together in my bike, to make 24v. I was looking at LiFePO4 batteries on eBay, said to contact them if you want to connect them together, so they can educate you.

LFP: Can I buy another of the same LiFePO4 batteries to double the voltage or capacity?
Bioenno Power recommends that you purchase a single battery that meets your voltage and capacity requirement to avoid any potential problems. Problems may arise if you attempt assembly of a larger capacity battery from multiple smaller units. The risks incurred may result in injury depending on output of battery. It is important to understand that LFP batteries are not like Legos – you should not attempt to wire them together as such. Our batteries are all computer controlled and should not be confused with the more common SLA, AA, AAA, and other such basic batteries which do not have any type of computer chip control. If your requirements should fall beyond our standard product lines, we have the capability of manufacturing most custom orders. Our experienced staff will assist you to the best of our abilities.

Surprised it works then, and I haven’t blown myself up yet. That’s not who I bought my batteries from though. It’s a SLA replacement battery.

That FAQ is from bioennopower.com.

Need more power?
Combine the batteries in series or parallel for higher voltages or more capacity. Dakota Lithium batteries scale up to build your own battery bank or portable power pack.

No wonder it worked. From here.

I have two of those. If I get a 48v scooter, I’ll need four of those, that’ll be $400. Almost a thousand dollar scooter after that.

Get the $700 scooter, only 36v, but comes with a lithium battery. Don’t know if it’s LiFePO4 or some other lithium. The other scooter is around $500, then the LiFePO4 batteries are $100 a piece, you’d need four. And you’d have to find somebody that knows how to connect them correctly. And that one is 800 watts, instead of 500. Voltage might matter more for going up hills though.

Make sure it’s under 1000 watts, or you need a license.