Right, so I just want to know what exactly I need to do to put a switch in there, possibly with diodes so I can have one battery, then plug in another one, then switch, for a millisecond or two they will both be plugged in, and in that small time, I don't want to overload anything, backwards, or however. I look to do it with relays maybe in the future off the parallel port or something nice that monitors the battery status then changes as needed, with multiples hooked up at once, with many switches. They are small and nice so... I know that it is just about impossible mechanically, per my understanding, to switch them exactly simultanieously so I don't get "no voltage" for a split second, then power again, as that might cause an obvious problem, computer rebooting. Thanks for all the input, its something everyone should think about to get max uptime. Bryan In article <361733D9.40B8DAF3@rochester.rr.com>, R. Paul McCarty <rpmc@troi.cc.rochester.edu> wrote: >Guillermo Dubrovsky wrote: >> >> hurley bryan (bhurle1@umbc.edu) wrote: >> : everyone seems to be worrying about the battery life of one single battery >> : or battery pack of many large batteries. Has anyone built a manual or >> : autoswitching pack to go between many batteries as need arises, to go all >> : day? >> >> why do you need to switch? why not wire them up all in parallel? (This is >> not a rhetoric question, if this works or doesn't for some reason, i'd be >> interested n knowing) >> chau >> AlejandroDubrovsky > >yes, this will work, but there are all sorts of problems with batteries in >parallel; the most dangerous being that no two batteries discharge at the same >rate, so when the voltages of batteries in parallel start to differ the battery >with the higher voltage discharges into the lower voltage batteries in reverse >(read bad). The way to get around this is to use diodes to prevent reverse >current through batteries in parallel, but diodes have an intrinsic voltage drop >around 0.4-0.7 volts which reduces the power of your batteries. > >i.e. 2x7.2 volt Li-Ion camcorder batteries have 3amphour cap. each alone, or in >series, giving you 2x7.2x3=45.2watthours, but in parallel you only get 7.2-0.4v >=6.8v x2x3=40.8watthours, so you lose almost 10percent of the power capacity by >using batteries in parallel. > >-Paul >
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