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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