Re: Individule battery chargers

[John Bryan <jbryan@micron.net>]

Hello EV folks,	

	I really shouldn't get involved with this, I did wait a long,
long time....got prodded some by a fellow EVer who couldn't believe
my silence on this topic, and finally decided to say one or two things
about individual (modular) chargers.

	First of all, I use them on a daily basis and not only have I
never had a problem with them, but I'm also just blown away (astounded)
by how well they work. When batteries are held at the very same voltage
for a long time, they become so well matched that it's uncanny. I sometimes
check individual battery voltages of the Optimas after they have been
sitting off charge for a day or two, and it's not unusual for them to be
within just .01-.02 volts of each other. I used to be amazed at this, but
have gotten used to it and now expect this level of equality between my
aging prototype Optima YellowTops.

	Now, going to Woodburn and leaving the EV sitting off charge and
out in the sun for a full month is a different case. I would not have been
surprised to see substantial variation between battery voltages after sitting
for this length of time. One of the great attributes of Optimas, and all AGMs
is a very low rate of self discharge which this data also shows. Checking the
four batteries under the front hood, I found their individual voltages after
resting for a full month to be:

	#1 13.81
	#2 13.82
	#3 13.82
	#4 13.83

I'll respond to a couple of comments made by my friend, Lee Hart:

> Yes, it's a good idea, and has been enthusiastically debated on the EV
> list before (check the archives).

	That's me :^)

> Bad points:
>  - lower reliability (one charger fails, and you can't drive)

	I'm not familiar with the failure modes of individual regulators
of any brand, but there must be some chance of failure (multiplied by # of bats).

>  - higher cost (N small chargers cost more than one big one)

	This can be avoided by using lots of cheap, low quality chargers. ;^)
Actually, the chargers I use (ZAP) are designed to run reliably inside a plastic 
case without any cooling. Removing them from the case, making a fine adjustment to
the voltage, and running them with a powerful cooling fan probably increases
their lifespan considerably. My fans come on when the charger heatsinks reach
110 degrees and turn off when they get down to 90 degrees. As the batteries reach
a full charge, the chargers go cold and the fans turn off.

>  - bigger, heavier chargers

	This is partly true, my arrangement is quite heavy. However, being
made of small parts made it easy to install in otherwise useless space in
my small car. Also, a new generation of small chargers are available that are
much more sophisticated, efficient, and lightweight.

>  - lots of wires to connect

	Isn't that something that pretty much all EVs have in common? :^D
Individual regulators would seem to be have this drawback as well. I'm using
universal post Optimas, which allow the chargers to be attached to the
battery sides, keeping the wiring neatly hidden away.

> You may come out one morning and find one of the batteries
> didn't get charged because its charger failed. Or, you may not discover
> it, and try to drive anyway. The one dead battery is soon ruined.

	Over many 100s of cycles, I have yet to have this happen, although it
obviously could. Glancing at the indicators before driving would prevent you from
damaging a battery. A circuit could be designed to check them for you, and report with 
an indicator light on the dash, and/or next to the charging socket.

Seeya,
John