Peakfoto Digital Photo Still n Video wrote:
I been use different light bulbs in serious with my charger to limit
the current to the pack for slow equalizing. I have the EV power
cell regulators and mini BMS.
How much current are your regulators able to bypass? You'll want your
charger to be turned down to some current below what the regulators can
carry while they are bypassing. If the charger is delivering more
current than the regulators can handle, you aren't really limiting the
voltage and the cells are still charging.
What kind of charger do you have? Does is have any means of controlling
the current already that you can tap into or control? Light bulbs in
series are something I would expect when the charger cannot otherwise be
controlled.
Could a fairly simple circuit be used that some kind of variable
resistance/load so I could turn my amps from variably 6.0 to 1.0
amps. My scooter use 22 calbs for like 80 volts while charging?
There are *many* ways to do this. Everyone will have a different
opinion, and they will all work to one degree or another. :-)
For example, your light bulbs are a good simple way to limit the
current. If your regulators can bypass 1 amp, pick a light bulb that
only passes 1 amp or less. Put a normally-closed relay contact across
this light bulb. When the relay is off, the bulb is bypassed and you get
full charging current. When the relay pulls in, it opens the contact so
the lamp is in series. Your BMS should have an output that indicates
when some cell begins to shunt current. Use this signal to pull in that
relay.
If the BMS happens to chatter on/off/on/off, then use a relay with a
second set of contacts (double-pole). Wire the second pole so when the
relay turns on, the second normally-open contact closes and also turns
on the relay coil. This makes the relay latch on the first time the BMS
signals that some regulator has started to bypass.
Balancing and battery baby sitting is a pain.
It sure is. Manual balancing works just fine, but gets old fast. There
is also a risk that you'll forget, or be busy doing something else.
Maybe a power transistor with a pot?
This can certainly be done. However, a transistor (and associated
heatsink, fan, overvoltage overcurrent and overtemperature protection,
and control circuits tends to make it a complicated and expensive way to
make a resistor.
Roland's comment about using SCRs and a phase control circuit is valid
if the current is pretty large. For example, I have a 40-amp SCR charger
that throttles back to 5 amps at the end of its charge cycle. That 5
amps would be a bit high to supply through light bulbs.
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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