[cadmus]

Thanks, you didn't have to do that i found the manual and read that. But that is very nice of you. thanks.

"- I would just get on with it." Yes sir. will do.
I started it several days ago, with rests every hour, but i was drawing so little that it was taking forever. 350 is as close to 400 as she goes. Nothing over it. but that is better than the 100 i was running at before.

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Last edited by cadmus; 06-04-2011 at 07:27 PM.

[cadmus]

Do you know what current the ham radio draws?
it could be as low as 100mA - so again 15+ hours to drain the batteries - why are you insisting on using other unknown devices to drain your batteries when the LaCrosse BC-9009 a $50 charger is designed to do that at settable currents....

Because the $50 charger was taking way to long for my 4 sets of AAs and only one set can be in it at a time. But all is good it is working at 350 now.

...except do NOT allow the voltage to drop below 0.9V - or the battery will be damaged.
I believe the BC-9009 automatically stops discharge when the voltage drops to 0.9V.

Well that is a little scary. thanks.
I have a volt meter and will monitor if i ever resort to the flashlights again.

Thanks for your patience.

[UnknownVT]

Because the $50 charger was taking way to long for my 4 sets of AAs. But all is good it is working at 350 now.

Your $50 LaCrosse BC-9009 was always capable of discharging at higher currents than 100mA.

Doing simple maths - even at a 80% charge at the minimum rated 1900mAh = 80/100 x 1900 = 1520mAh.
Discharge at 100mA would have taken 1520/100 = 15.2 hours.........

I did suggest discharging at 400mA several times.

Now you do realize that discharging at 350mA appears to AUTOMATICALLY follow on with a charge at twice that - (Read the * Manual please!) which means 700mA - this is sub-optimal charging current -
the recommended charging current for eneloops is 1000mA.

[cadmus]

Your $50 LaCrosse BC-9009 was always capable of discharging at higher currents than 100mA.

Correct but the operator was not.

Discharge at 100mA would have taken 1520/100 = 15.2 hours.........

Yeah and rotating between 4 sets every hour it was taking forever without any sign of improvement so i called for support, thanks for the help.

I did suggest discharging at 400mA several times.

I know.

Now you do realize that discharging at 350mA appears to AUTOMATICALLY follow on with a charge at twice that

Yes i was aware of that.

[UnknownVT]

Yes i was aware of that.

Cool! -
good luck to you.

Hope all goes well -
and when you get back please tell us all about it -
and much more to the point show us your pics.

[cadmus]

Hate to drag this out but:
What physically/chemicaly/redoxily (i made that word up) causes damage if you drop below .9 volts?

Also, lets say i had all the time in the world. If i discharged at 100 that kept them at room temp. If heat is our only big fear is there any reason to rest them when draining at such a low speed? (that was the logic behind my hot hot is too hot questions)
As a side note i felt no observable temperature change at 100, 250 or 350.

[UnknownVT]

Hate to drag this out but:
What physically/chemicaly/redoxily (i made that word up) causes damage if you drop below .9 volts?

Deep discharge (to below 0.9V) is not healthy for the battery -
very deep discharge can damage the battery.

I have never done that - so do not know from first hand experience -

I understand getting hit by a car head on at 90 mph can kill you -
but I've never done that to tell you that from first hand experience.

Also, lets say i had all the time in the world. If i discharged at 100 that kept them at room temp. If heat is our only big fear is there any reason to rest them when draining at such a low speed? (that was the logic behind my hot hot is too hot questions)

If you had all the time in the world discharging at 100mA for 15.2 hours -
probably can save you the suggested 1 hour wait
when discharging at 400mA for 3.8 hours

TOTAL time saving = oh, wait it's negative .....
at -10.4hours.

Good thinking Batman!

From the Maha C9000 manual:

As a side note i felt no observable temperature change at 100, 250 or 350.

Have you actually fully discharged sets at 100, 250 and 350mA to be able to say that?
Or are you just switching the discharge currents and feeling for the temperatures?
It's the temperatures toward the end of discharge that matters -
if they are warm - then one ought to wait a while before charging -
really, is it that hard to accept?

That's somewhat like telling the difference between 30 and 40mpg cars -
just by starting the cars in the driveway......

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Last edited by UnknownVT; 06-05-2011 at 12:11 AM.

[cadmus]

...is it that hard to accept?

Yes. I am a scientist. Sorry if I am killing you with questions, you don’t have to answer them, I will read up on it someday. I trust your opinions and like you, so no offense. But, yes, i was looking for the logic. I will follow your advice but i still want to find the logic. Learning the mechanism of an issue and seeing empirical evidence is what lets me rest a question. Maybe the people who write owners manuals do both but they never include it, eh? It could be the manuals are spot on or they are covering up for a poorly designed product.

I DO know many of the ways a 90mph car collisions will kill you, and that makes me a better driver, voter, EMT, person.... It should be included in all drivers ed classes. I have ways to compare and contrast a 30mpg and 40mpg car that is sitting a driveway. And I was wondering is it damage to a AA's membrane, pH changes, or what might cause a <.9v charge to damage a eneloop. Is the deadly temperature a big (palpable) difference, is it the systemic temp or the temp of some small component deep within? Those are good questions and are the types of questions common in these forums. I felt they were perfectly valid.

Have you actually fully discharged sets at 100, 250 and 350mA to be able to say that?
Or are you just switching the discharge currents and feeling for the temperatures?
It's the temperatures toward the end of discharge that matters -

Considering how quickly a AA battery equilibrates to it’s surrounding temp, it’s surface area, the lack of insulation around my charger, etc. I am guessing it reaches a equilibrium temperature long before the final minute of discharging. So after a few (5, 10, 20) minutes of discharging it likely is the same temperature as at the end of the charge. The heat being created is constant and as the temperature increases the heat being dissipated is increased until an equilibrium is reached. That is the case with most batteries (I used to design/build weather stations and remote sensing equipment). I might be way off here. So I was assuming my 40 minute observations at 100, 250 and 350 were sufficient as the temp was either not high enough to palpate or was not increasing in temp after 10 minutes. But as I said I was palpating and only palpating the systemic temp. shooting from the hip here. Is it max temp or duration of heat that matters. Is it systemic temp or temp of a component. Will a lower draw current that is continuous be better than the higher current with rests, these are valid questions but I doubt we will ever know so I will draw low and rest often.

It looks like those rests on that manual are between charging and dischargings. Not during the draining. That could be temperature. Or something chemical, a balance of electrons in the redox equations that needs time to equilbrate? We don’t know from the manual.

Thanks for your time,
Pete

[UnknownVT]

Considering how quickly a AA battery equilibrates to it’s surrounding temp, it’s surface area, the lack of insulation around my charger, etc. I am guessing it reaches a equilibrium temperature long before the final minute of discharging. So after a few (5, 10, 20) minutes of discharging it likely is the same temperature as at the end of the charge.

My understanding is that the more the battery is used the more internal chemical reaction has taken place and the more the battery is likely to warm up
so for the same discharge current a short duration normally would be less indicative of a temperature change than a discharge for a longer time.
(for charging - the battery really only heats up toward the end of its charge)

Also applying your own logic the battery itself has bulk so would take some time for it to reach the same temperature at its surface as it is internally.

The manual from Maha C-9000 is by Maha energy - who are one of the respected vendors on battery technology - I realize that might not pass your exacting muster - but they give good information - the sequence for discharge then charge with a rest in between is where I got the suggested rest from. This rest sequence is a built-in algorithm for the Maha C9000 charger.

As I said they are your batteries so everything is your decision.

A lot of this is on the net where appropriate I had given links which shows enough respect to you so you can check things out for yourself -
just as your manual was - it could have saved you several hours wasted discharging at 100mA.

Must admit I was a bit taken aback you did not figure out the relationship between the discharge current and likely remaining capacity to know immediately discharging at 100mA would take over 15 hours - what you called "taking forever".......

Anyway all the best to you on your trip - hope everything goes well and you enjoy yourself -
I am envious of your trip. Show us your photos please.

[cadmus]

I was well aware of the calculated discharge time and the huge margin of error on charging and discharging time with this thing. 3 days ago it seemed very doable.
It WAS taking forever.