"Daryl" wrote in message
...
The method of charging is more complicated than the other versions.
NiMH batteries work well if you only have one cell (say, 12 volt
using 4 3 volt cells). But when you are trying to generate 36 volts
to 400 volts, each cell pack must be independently charged. Not
possible in that application.
If YOU don't know how then it must be impossible.
http://www.mpoweruk.com/balancing.htm
"To provide a dynamic solution to this problem which takes into
account the ageing and operating conditions of the cells, the BMS may
incorporate a Cell Balancing scheme to prevent individual cells from
becoming overstressed. These systems monitor the State of Charge (SOC)
of each cell, or for less critical, low cost applications, simply the
voltage across, each cell in the chain. Switching circuits then
control the charge applied to each individual cell in the chain during
the charging process to equalise the charge on all the cells in the
pack."
The balancing circuit is simply a resistor and a FET across each cell
to bypass some of the charging current when necessary. The FETs can be
optically isolated from the control circuit for high voltage packs.
And you haven't seen a burst case either. Bulging, deformed, etc.
case but the juice is contained in the case.
I sure have, it was displayed as a memorable example of how NOT to
design a battery charger. The plate edges were visible through the
crack.
The reason the AGM isn't used in larger applications is that it
cannot be recharged as it is being discharged. You left out a slew
that use Deep Cells.
Daryl
Again, YOU don't know how. A battery monitor circuit that measures
current and voltage can model the battery with a custom microcomputer
to predict its state of charge and tolerance for charging current, at
any point in the discharge cycle. They lose track as the cells age
which is why Lithiums need to be periodically fully discharged and
recharged, to recalibrate the model.
http://www.ti.com/sc/docs/msp/sine_on/batt_mgmt.pdf
Look at how much the bq2060 can do for $4.32. Connect it to a PIC and
you can record the full service and maintenance history of the
battery, like a little Black Box. That's how I know what really hurts
Lithiums.
jsw