Controller upgrade

[Mauri Meere]

Hi folks
Does anyone know the name of the company that took over the company that made the NDR-30amp controller (purchased in 1993)? I have questions about voltage settings.

Also, where can I find a spec sheet for a Kyocera 51watt pv panel (also purchased in 1993)? I particularly want to know the Voc and the temperature coefficient so
I can calculate the Voc at -30deg C. I'm looking to replace my NDR-30 with a new controller that will also allow for a little expansion in the future. I prefer an MPPT but realize that a PWM might be a better option.

My system is located in the unheated space under my cabin where the temperature has reached -30deg C. It is used only on weekends. And has the following components:

4 Kyrocera 51watt pv panels in series-parallel
1 NDR-30amp 24volt controller
8 Trojan T-105 6volt 225amp-hr batteries in series parallel
1 Trace U2624 inverter

Thanks for any advice with respect to a replacement controller, new or used, MPPT or PWM, and of course suggestions about my set-up.

Mauri