12v charger efficiency

Hey guys, new here. I'm getting ready to get started on my second EV and I'm thinking about ways to keep the cost down. Anyway, having spent $850 on a used BC-20 and boost transformer for my last car, I got to thinking about using a whole bunch of those $25 cheapo 12v chargers, like 10 or 12 depending on pack voltage, one for each two batteries.

Anyway, I was wondering if this setup would be tremendously less efficient than a hi-voltage charger, and if there are any other significant problems.

Anbody else out there tried this?

Thanks!
Andrew