It is most certainly possible. The only difficulty is that the charger in the current unit is designed to manage NiCad batteries, which have a different charging characteristic from that required by Lithium ion. It would be relatively straight forward to design and construct a 'smart' charger for Li-ion, the chief requirements being tight control upon the charge voltage (4.2V/cell, +/- 50mV) and accurate current monitoring, terminating charge when current has dropped to <3% of rated charge current specified for the cell. Rather than 'trickle charging to maintain >85% charge, a 'top up' charge cycle is initiated when voltage across the cells has fallen to 3.8V; (when battery is holding about 60% of full charge) again terminating when current drops below 3% of rated. A good site dedicated to everything about batteries and chargers can be accessed here:- http://batteryuniversity.com/learn/article/sharing_battery_knowledge Good Luck! On Mon, Jul 16, 2012 at 1:35 PM, Dave wrote: > Nimh cells hate trickle charge and outdoor temperatures > > YES NOPE9 wrote: > > >> > >> On Jul 16, 2012, at 1:26 PM, mail@crcomp.net wrote: > >> > >> The controller of my old Rain Bird sprinkler system uses a 9V NiCad > >> battery for backup in case of power outages. > >> > >> Is it possible to replace a NiCad with a 9V1 advanced Lithium? > >> > >> TIA. > > > >It is likely that your Rain Bird has some kind of circuit to charge the > NiCad battery. This charge circuit will NOT be compatible with a lithium > battery. The simplest thing to do is replace the NiCad with another NiCad= .. > Otherwise , you likely will destroy a lithium replacement ( and more stu= ff > as well ). You can modify the circuitry to support lithium batteries ...= .. > that is not trivial. > >Best Gus > >-- > >http://www.piclist.com PIC/SX FAQ & list archive > >View/change your membership options at > >http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 Perry Curling-Hope Research and Development --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .