In a message dated 24/11/2008 05:43:49 GMT Standard Time, yuri@ostry.ru writes: I simply put large rechargeable Lithium-Vanadium pentoxide coin cell with appropriate charging circuit to GPS carrier board and forgot about this question... Another solution is to put CR123 battery holder to carrier PCB, stuff it with a good quality cell and it will probably last for 15+ years, driving just clock and CMOS RAM during power outages.. ---------------- And if it's important that the whole system stays working for reasonable length drop outs, lead acid gel batteries on a master 12, 24 or 48 volt (nominal) power supply, again forgetting batteries at board level, are still hard to beat. regards Nigel GM8PZR