Cut-off voltage

Which is the cut-off voltage of the JetBook Lite?

This message was edited 1 time. Last update was at 01/01/2010 03:48:57

I second the inquiry because in the Lite it seems the battery meter is either defective or calibrated to alkalines. With rechargeables, I get a critical warning one or two hours after the meter goes to half. I never reaches the 1/4 point.

I hope they can correct it with firmware. I had a little program on my Palm III that let you tell the device what type of battery was installed so the meter was calibrated.

Yes, I think that, too. I had experience of immediate power-off after few hours with rechargeable batteries (NiMh) when the indicator was 3/4. Perhaps the batteries were defective, but maybe the cut-off voltage is not low (and the indicator not calibrated for NiMh batteries).

And which is the max voltage it support? I could buy NiZn batteries from PowerGenix (Amazon link) if needed, but they can provide 1.85v when fully charged (and 1.7-1.6 in normal conditions).

Wow- I thought all NIMH batteries were 1.2V. Alkalines, where the book reader meter is probably calibrated, are 1.5 volts.But if you only got a few hours TOTA out of NIMH, it sounds like you have a bad battery.

I'm testing mine now with alkalines, writing down time used, to see if I get the 25 hours Ectaco claims, but more to see if the battery indicator acts more normally by dropping to 1/4 then zero before getting the critical warning. If it does, that will mean that the voltage detection value is correct for alkalines but incorrect for NIMH. You should be able to TELL the bookreader what type of battery you have installed so it can set the battery meter appropriately like on my PalmIII. I guess Ectaco has not got there yet-I'm hoping they will. I am not a software engineer, but some of these things are fixable with a few lines of code.

Probably they suffered from voltage depression caused by a recharge when they were partially charged. Standard NiMh batteries suck very much. I see two possible solutions:
- Ni-Mh Hybrid/LSD batteries (1.2v)
- Ni-Zn batteries (1.7v)

I'd like a suggestion from Ectaco, since they know better than me how much the JetBook drains and the voltage range supported.

Dear Customer

Jetbook-Lite is supplied by 4 AA Alkaline batteries, with a total voltage of 6V. At this case unit must work for a week or at least 25 hours of non-stop work.
It must be recharged when voltage gets less than 5V. You will see warning on the screen when it happens.
Jetbook-Lite is totally discharged when average voltage is less than 4V.
Unit will not turn on.

Best Regards,
Pavel - technical support
Ectaco INC,

green wrote:It must be recharged when voltage gets less than 5V. You will see warning on the screen when it happens.

WTF, 4 x 1,2v rechargeable batteries provide 4,8v, are you saying that I have to recharge new batteries?!
What's the max voltage supported?

alexdupre wrote:WTF, 4 x 1,2v rechargeable batteries provide 4,8v, are you saying that I have to recharge new batteries?!
What's the max voltage supported?

Actually, 1.2 v is their median voltage. Their discharge curve varies somewhat with the energy draw.

This is from another site, where the person tested a 4-pack of NiMH batteries with a 0.5 A draw. I am not sure, but I think the draw is somewhat less for the jetBook-lite.

NiMH batteries stay at their median voltage for longer than alkaline batteries, so although it will be below the warning voltage fairly quickly (assuming that the info given is accurate) it will not turn off for quite a while.

I have a set of NiMH batteries that I just charged up and will be using starting at the end of the week (when the alkaline batteries that were supplied with the unit run down) I will let you know how well they last.

What about running with three NiMH and one Alkaline, that would have a starting voltage of 5.1 rather than 4.8 -- would that help?

kirbinster wrote:What about running with three NiMH and one Alkaline, that would have a starting voltage of 5.1 rather than 4.8 -- would that help?

Mixing batteries can cause leaks because of imbalance as they discharge.