topology suggestions for 3.5kW batt charger?
- From: "Tesseract" <u35475@uwe>
- Date: Sat, 30 Jun 2007 21:06:25 GMT
Greetings all - just found this site while searching for "boost pfc" and
noticed that Winfield Hill has posted here before so I figure the site can't
be all that bad ;)
I'm just throwing this out as a sort of curiosity-type question. I have
designed quite a few switchmode power supplies over the years but nothing
even approaching this power level (600W is the previous maximum). A friend of
a friend has one of 492 electric chevy S-10 pickups, and the onboard charger
has lost its magic smoke. Frankly, the design of this charger/motor drive
pretty much blows, ihmo, so I'm toying around with the idea of whipping up
something new. "Toying" because there is little financial motivation for
doing this. However, it is an interesting project and that is motivation
enough, sometimes.
There are two banks of batteries in the pack, each containing 26 12V/42Ah
batteries. The manufacturer, Genesis, recommends charging them at the 0.4C
rate up to a maximum of 2.4V/cell (with -20mV/C of compensation). As this
comes out to a rather onerous 6.3kW, I'll either have to go with a less-
ambitious charge rate or force the guy to unplug the range every time he
needs to plug in (or, of course, have a dedicated 40A. circuit installed). As
of now he does have a 240V/20A circuit for this purpose which, if we adhere
to the NEC, gives us *just* enough continuous amperage to charge each bank at
0.25C (10.5A) . This means both banks can be sequentially charged in about 8
hours, which is tolerable.
A linear and/or design using 60Hz magnetics is totally out of the question -
you won't be able to move the thing around without a forklift. The next
simplest thing I can imagine, then, is to use the output of a boost PFC more
or less directly. This has some serious safety issues, but it ain't like I'm
going to be submitting it for UL approval any time soon. So, these are the
various factors/ideas I am contemplating:
quasi-resonant (soft) switching; ZVS or ZCS?
IGBTs or advanced MOSFETs
Boost PFC + full-bridge or some combo to provide isolation
Current mode control is a natural, here. Voltage regulation needs to be
accurate but there's no need for a lot of loop bandwidth (ie - fast transient
response not required). Ideas welcome!
-Jeff
.
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