Hi Bruce (and all),
Bruce, thanks for digging up the links. A nice trip in the Wayback
machine. :-)
brucedp5 via EV wrote:
When I look at its schematic, it reminds me of what I cut my teeth on,
way-way back in grade school talking electronics with my Lockheed Engineer
Dad... ( : old : ).
But purists forgive me, this is achiest technology, long before the
switching circuitry designs of today. Its old saturated transformer
windings, and chopped/spiky current output design can't be more than 50%
efficient. That means a lot of the power pulled from the AC (L1) outlet is
wasted and does not go into the pack.
It's actually a pretty efficient design; around 85%. Nothing gets hot
(notice there's no fan). SCRs *are* a solid-state switching device.
An L1 outlet can supply (120VAC*12A= ) 1.4kW, which means only 700W goes
into the 48VDC PbSO4 pack (700/48= ) an average of 14ADC charging current.
The fuses are rated higher to handle the spiky currents.
The issue you are alluding to is Power Factor (not efficiency). This
design has a low PF of about 0.6. This means you get about 60% of the
power out that a perfect device could have supplied from a 120vac 120v
L1 outlet.
The "missing" power isn't lost to heat, and you're not paying for it in
your electric bill; it simply is not drawn from the AC outlet. A power
meter would show that the input voltage may be 120vac at 12a; but the
power input is only about 60% of 1440w = 864 watts. Then, the charger's
85% efficiency means it turns that 864w input power into 864w x 0.85 =
734 watts out. That's 52.5v at 14 amps.
Sure enough, a 6v battery on charge will be about 6.7v. 6.7v x 8
batteries = 53.6v. :-)
David's Delta-Q idea is a good one as an upgrade path.
Yes indeed; Delta-Q chargers are a good option. They are not only
efficient (about 85%), but also have a high power factor (about 0.95).
to maximize the amount of charging power you can get from an L1 outlet.
That's about 22 amps of charging current at the same voltage.
A search
https://www.ebay.com...
Watch out for cheap chargers from no-name sources. There are some really
terrible ones on the market! Most people just buy on price and flashy
advertising... and get junk.
One advantage of the olde-skool designs like the ComutaCar is that they
are very reliable, and easy to fix. Many of the new ones will be dead
and unrepairable in a few years.
--
In software development, there are two kinds of error: Conceptual
errors, implementation errors, and off-by-one errors. (anonymous)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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