The International Cessna^® 170 Association

The KLN-88 Loran has an internal lithium battery (as do most RNAV units). I have been told that it's a Tadiran 3.6v Lithium battery, model TL-5135 and can be had from Tri-State Electronics (http://www.tselectronic.com) for about $16.00
For cont'd airworthiness it should be installed by an avionics shop, but who knows what a dedicated cheap-skate might accomplish if the radio is only used for "entertainment purposes."
The KLN-88 will work fine without it, but the user database and saved flight plans will be lost should the 10-year battery die, and each user waypoint/flight plan will have to be re-entered manually each time the unit is powered up.

When my internal battery died in my KLN-88 last year, I took it apart to see if I could locate the battery, and never saw it. I've replace many lithium cells in amateur radio equipment, but once I saw the depth of disassembly required on the KLN-88, I sent it to Bevan-Rabell (sp?) and they did a nice job for under $200 including a full check out and reloading/rebooting the unit once the new battery was in place. The tech told me that even if I had dug down into the unit far enough to gain access to the battery and replaced it, I would still be left with the problem of re-initializing the unit. Any way you slice it though, the KLN-88 is perhaps one of the best values in navigation equipment.