I have just had qty. 4 13.2 volt ones rebuilt. Not cheap but lower than buying new. $150.00 for 4 bat. packs. Yes, the cooler they are the more charge they accept particularly if they are aged. Just a tip: always discharge ni-cads before recharge to overcome the memory problem, however, never run them dead flat as when you recharge your run the risk of one or more cells recharging in reverse polarity; now your bat. pack is foooked.
Spent 13 years working for Chloride/ Exide so been there.