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Re: (ET) charger voltage




On Fri, 28 Jul 2006, Elie, Larry (L.D.) wrote:

Actually, the more cells, the greater the likelihood of one bad actor.
I've seen them actually reverse charge.  Let's see how well you can
bring the pack up when one cell is at -2.3V....  You are lucky to get
the others to 60% charge.

I'd think though that if that happens, you should just replace the battery. :)

Mr. Landis and I have disagreed on this in the past.  His charger works.
The ET charger works.  They don't work in exactly the same way.  If the
ET charger stopped at even 40V you will not get a full charge.  Harry's
charger will pump it up again a number of times after the battery cools
which gets the job done.  It won't be as fast, but if you want to just
leave it on for months it's superior.  There are other techniques

That's sort of what I'm saying - that a higher voltage will let you charge faster, but you *could* get a complete charge with a lower voltage (as long as it's still a good bit above the voltage of a fully charged pack). But, that may not be convenient for most people. That said - I checked the capacitance of the cap on my charger about a half hour ago, and it is indeed toast (read no capacitance at all - which now has me wondering how the charger is putting out a fairly stable 39.5V with an apparently dead cap). So, I'll be replacing it. But, I still am looking to find out exactly what the voltage of a fully charged pack should be, so I can decide whether to up the set point voltage on the Landis controller, and if so, to what. I don't want to leave it plugged in permanently when not in use - so I'd rather not have it shut the charger off *right* when the pack first hits 38V, if it can charge up higher than that.

available as well.  Remember, the ET charger can put out lots of current
when the batteries are low because it is a simple constant voltage
design; you dropped the peak voltage the current it would put out at
lower voltages is also reduced.

Yup, thus slower charging.

Another factor you are leaving out is that 38.2V is the room temperature
voltage 90 minutes or more after charging.  The voltage at the pack at

I'm not leaving that factor out - I don't know that factor. :) My initial question on this was asking what the voltage of a fully charged pack should be. If it only drops to 38.2V 90 minutes after charging, then apparently a fully charged pack just after charging should be higher - and that's what I want to know. I figure I could bump the set point on the Landis up to a smidgen under that fully charged voltage, at least for during the summer, and if I don't use the Elec-Trak in the winter, I could move the set point back down to 38V.

the end of the cycle on an ET charger will be over 42V, with the
batteries well above room temperature.  If you really want to see where
to cut off, measure each battery with a DVM and see if they are all at
least 6.4+V.  Frequently, you have one still at 5.9V with others at 6.5V
at the 38V level.  By the time you are at 42+V, the worst battery is
usually near 6.4V.  Try it yourself and see.

Can't try it right now, since my charger is only putting out 39.5V. :) And of course the Landis is shutting off the charger when the pack is at 38V. So, what should I bump it up to? 39V? 40V? 42V? Of course, I'll need to replace that capacitor first....

Mike