Terrible Tom <silvereightynine@aol.com> wrote:
> jon@dakota-truck.net wrote:
>>
>>
>>
>> I'm not 100% sure on this, so don't go wiring anything just on my
>> say-so :-) but my gut tells me it would probably be possible to hook
>> two 12v batteries up in series (Battery A + to Battery B -) such that
>> you get 24v by hooking your winch to Battery A - and Battery B +, but
>> charge them individually with your 12v alternator(s).
> ok here is a question for ya - lets say you take two 1000 CCA rated
> batteries - 12 volt... and wire em up for 24 volts in series. Does
> that give you a 24 volt battery rated at 1000 CCA? What happens to the
> battery ratings when you series'em?
Yes, when wired in series, the amperage is that of the lowest
rated battery; in your example, the "24v battery" would still be rated
at 1000 CCA. (If you were to wire a 500 CCA and a 1000 CCA battery in
series, that "24v battery" would be rated at 500 CCA.) This is
because the current path is flowing first through one battery and then
through the other, so in the example of a 1000 and 500 connected
together, if the 500 can only provide 500 CCA by itself, it isn't
going to be able to provide more than 500 CCA wired in series either,
because all of the current still flows through that battery with no
alternate route. Its basically a chain, and its only as strong as the
weakest link.
When you wire them in parallel however, the amps are additive. Two
1000 CCA batteries wired in parallel basically act as one 2000 CCA
battery (assuming that the wiring is beefy enough to carry the
current). This is because you can basically draw 1000 CCA from each
battery simultaneously. Unlike in a series which is a chain, the
electricity can take the path of least resistance, which causes the
load to be spread evenly between the batteries; all the current
doesn't have to flow through each battery individually. In a parallel
setup, if you had a 500 CCA and 1000 CCA battery, it would act like a
1500 CCA 12v battery. (Its generally recommended to stick with
similar batteries though, whichever method you use to wire them
together.) Wiring in parallel also gives you more capacity. If a
particular load would drain a 1000 CCA battery in 5 hours, wiring two
1000 CCA batteries in parallel would allow you to run that load for 10
hours. (I use the "CCA" designation here just by way of an
illustration; once you start to talk about running loads off of a
battery and increasing capacity and such, they are usually referred to
in terms of amp-hours. For example, a 10 amp-hour battery can run a
10 amp load for 1 hour, or a 1 amp load for 10 hours, or a 2 amp load
for 5 hours, etc.)
Although you don't gain additional capacity in the form of amps
when wiring batteries in series, because the voltage doubles, you get
the benefit of doing the same amount of work with half of the current
(amps). Work is watts, and watts = volts x amps. So a 240 watt load
run on 12 volts takes 20 amps, whereas that same 240 watt load run on
24 volts takes only 10 amps. The big benefit there is the ability to
get the same amount of work out of the same size battery system while
being able to use smaller gauge wire, perhaps less expensive switches
and relays due to lower amp requirements, etc. (Although I don't know
this for sure, I suspect this is why the electric utilities use high
voltage to transport electricity; in order to reduce the size of the
cable required; if their transmission lines were 120v, the required
cable gauge would be obseen!) :-)
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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