Lawrence Rhodes wrote: > The charger chip that senses current and voltage is a nice feature. > Can these chips be added to a charger like the B&W or maybe a variac > bad boy.
Most of these chips are designed for small low-voltage low-current battery packs, as used in laptop computers etc. It's not going to be easy making them work correctly with a large EV pack. The shunt to measure current is often inside the chip. This is simply too small for a big pack. On some, you can use an external shunt, but they still assume relatively low currents, and so designed for a shunt with a large voltage drop, like 0.25v at full current. If you tried this charging at (say) 25 amps, the shunt would dissipate P = 0.25v x 25a = 6.25 watts. The chips are usually powered from the pack voltage, which is usually 12v or less. You have to provide some kind of low voltage supply for the chip. This can be complicated because some chips sense battery voltage via their supply voltage. Most have on-chip temperature sensors. This works fine for small batteries, where the chip is mounted right inside the battery pack. It does not work for EVs, where the chip is far away from the batteries and so not at the same temperature. Finally, the algorithms designed into these chips are often very specific, designed for one particular type of battery. In some cases, I swear neither the chip manufacturer nor their customers have any clue as to what good charging algorithms are. For example, they are designed charge fast, without regard to battery life. Or, they don't worry about charger efficiency, and use linear regulation. Or they don't provide delays for state-switching, so they abruptly switch modes due to momentary glitches in AC line voltage or momentary loads on the EV's battery (like opening a door so the dome light comes on, so the DC/DC converter kicks in, loading the propulsion pack. When you close the door, the sudden drop in propulsion pack current falsely triggers a mode change from finish to float). -- Lee A. Hart Ring the bells that still can ring 814 8th Ave. N. Forget your perfect offering Sartell, MN 56377 USA There is a crack in everything leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
