Is it Beltran who makes them or is it Yaesu?..or are they the same?
The brand name "Battery Tender" belongs to Deltran, based in Florida. Anything else is an imitation.
When they first became popular, in the late 80's, there were a few stories about Battery Tenders causing fires, and boiling out batteries. This was attributed to faulty trickle/cutoff circuit. Deltran stated that they doubted that their product was at fault, as the name "Battery Tender" was being used to refer to any gizmo that you charged your battery with.
In the mid 90's Deltran came out with their second-generation Battery Tender, and it has an even more sensitive circuit for monitoring the state of a battery's charge (enhanced algorithm). What I think is great about Deltran, is that as battery technology changes, they keep pace with their products.
I have dealt with Deltran directly, and I have to say that their customer service, sales, and technical support are first rate. You can buy directly from them, which is great if you are unsure about which product is best for your use, or what accessories you want. However, if you know what you need, you'll probably find better deals on the web.