wes wrote: > On Fri, Feb 19, 2010 at 10:42 AM, Tim Wescott <[email protected]> wrote: > > >> Keith Lofstrom wrote: >> >>> On Fri, Feb 19, 2010 at 10:01:25AM -0600, Fred James wrote: >>> >>> >>>> "but not with a 0V battery" - I don't know - from the documentation one >>>> might expect the BBU to shutdown leaving some "reserve" power in the >>>> >> battery >> >>>> Now, Verizon "tech" did say the aux port wasn't hooked up, but APC >>>> couldn't understand that statement - i.e.: APC's documents contradict >>>> Verizon's statement - but I don't know how to verify that either way? >>>> >>>> >>> Verizon is not in the business of telling the truth. They are in the >>> business of keeping their equipment safe from hardware hackers like us. >>> Obviously, there are risks, starting with some clown hooking a car >>> battery backwards into that port. If I was programming an Indian call >>> center, I would have them say whatever was necessary to keep people like >>> us from fooling with the customer equipment. I'm grateful that they >>> were willing to help me plug into the ethernet port on the ONT, rather >>> than route through the Actiontec cable modem as originally installed >>> (another story). They could have told me to jump in a lake. >>> >>> The aux port does hook up to the aux indicator light, and there is a >>> 12.5V threshold, so it is not just a matter of an otherwise-unconnected >>> LED and resistor. I imagine that under the right circumstances, the >>> port will provide power though the BBU. >>> >>> I'm guessing that replacing the good battery with an almost-but-not-quite >>> discharged one will cause the main BBU to draw power from the aux port. >>> The BBU control circuitry that does the switching may be powered off the >>> main internal battery, drawing a trickle of current. >>> >>> If the external APC unit has a charger, then that is good news, because >>> it means the main APC unit is not trying to charge it, and probably >>> does not care how big the external battery is. Car batteries are much >>> cheaper per watt-hour than the small gel cells, and you can keep them >>> on a trickle charger. In extremis, you could even power the unit from >>> the battery in a car, BUT DO NOT CONNECT IT WHEN THE CAR IS RUNNING, >>> the ignition spikes would likely kill the APC BBU. >>> >>> >>> >> If you're looking for inexpensive lead-acid batteries for this service, >> look to deep discharge marine, RV or golf cart batteries. Car batteries >> are optimized to generate LOTS of current for a short time, and are >> presumed to rarely get deeply discharged. This is because that current >> is needed, and they generally still have considerable remaining capacity >> when they're too 'dead' to turn an engine. As a consequence of being >> optimized for low price and high current output they don't do a good job >> controlling where the material plates on during charge after a deep >> discharge, so they tend to suffer an early death if they go through too >> many deep discharge/charge cycles. >> >> There is considerable collected wisdom on this subject in the amateur >> radio literature, from folks building emergency-power stations suitable >> for the aftermath of fire, flood, and earthquake. They all say "don't >> use car batteries". >> >> Anything called "deep discharge" will (well, should) be designed to be >> deeply discharged -- and recharged -- on a regular basis, and will >> probably severely compromise cold cranking amps while doing so. >> >> -- >> Tim Wescott >> >> > > The more common term that I've seen used is "deep cycle." > > I knew I was getting that term wrong!
-- Tim Wescott Wescott Design Services Voice: 503-631-7815 Cell: 503-349-8432 http://www.wescottdesign.com _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
