Re: Charging telemetry data--take 1

[Seth <vze3v25q@verizon.net>]

A couple things:

12.8 is pretty full, especially for worn out Hawkers. For fresh gel
batteries, I would expect 13.00-13.03 per 12V module. But I am not as
familiar with Hawkers. My 1996 vintage GP38EV10 are full at
12.78-12.85V. Full being defined as a day of 13.6V then a day of rest.

400V float seems a bit high. 250ma/ string seems high for 26 Ah
batteries. I might suggest closer to 100 milliamps max.

Mid 290V sounds fine for full power. That's ~11.8V which is good for a
low current, higher voltage AC traction system that trades modest power
for reasonable battery life. On fresh batteries I would expect the
voltage to be more like 305ish at max power.

The gauge reads 1/2 full because the old batteries only have ~60% of
original capacity. So 50% discharged is really 85% or thereabouts. 

Did you mention the date code on the Hawkers? I suspect they are at the
end of their calendar life, ignoring battery neglect.

Seth


Christopher Zach wrote:
> 
> Ok, I came home, and plugged the PC into the Dolphin. Then I powered up.
> 
> The Dolphin has a counter that controls the fuel gauge. Currently it reads
> 100%. The battery pack voltage at rest was 320 volts (25 12 volt batteries
> per string, 2 strings.)
> 
> Works out to an average of 12.8 volts per cell. Hm.
> 
> I then plugged in the charger. When at 100%, the controller brought the pack
> voltage to 400 volts at about .5 amps. This appears to be the "trickle
> charge" mode designed to equalize the batteries (high voltage, low current)
> 
> I then fired up the car and drove up and down the steep driveway hill.
> Voltage at full power was in the high 290's (I have to check) with a power
> output of about 35kw (120-130 amp draw). From a 52amp/hr pack how is that
> for sag?
> 
> At the end of a few ups and downs, the pack was down to 97.5% by the
> counter, and still at about 320 volts at rest (ok, 319).
> 
> I then plugged in the charger. After a few minutes to let it get up to steam
> (normal) it was reading a pack voltage of 331 volts with a charge current of
> 3.3 amps for a 1.1kw charge. Line voltage was 111 volts (down from 121 idle)
> at 12.8 amps (the max the controller will take, I can adjust this)
> 
> The batteries are now 97.8% full. Here is what I am wondering:
> 
> What if the problem is this: The system has this neat counter that watches
> current go in and out of the batteries. When the *counter* reaches 100%, it
> declares the batteries "full" and does 8 hours of trickle charging at 400
> volts/.5 amps. Then it shuts down. This will keep the controller from
> overcharging the batteries.
> 
> But over time, the counter becomes out of whack with the "truth" of the
> batteries. The counter thinks "full", but the batteries will still want a
> bit more charge. But they don't get it. Time passes, and the max charge of
> the batteries becomes less and less.... This sort of bears up in my test;
> after 30 miles the gauge read half full but the batteries were tired.
> 
> Now, being the guy I am, I apparently can reset this number to anything I
> want. The question is should I reset it to something like 90% when it thinks
> it's full to give it another 10% of "overcharge"? Will I run the risk of
> damaging the batteries? At what voltage should this pack read "full"?
> 
> To be honest, the pack might be only 60% full. And the fact that it's
> happily sucking max power right now (3.3amps) makes me wonder about that.
> I'll watch it and see if it goes to trickle simply because the counter hits
> 100%.
> 
> Thoughts and comments from the battery crowd? The biggest thing I may have
> going for me right now is that this pack only has 1,800 miles on it; it
> might be saved...
> 
> Chris

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