Topic: Microtracker battery options

[Todd R]

You're correct -- you should have at least a 2v differential, so at least 7v input for a 7805 5v regulator.  Doug Oade has suggested putting one or two diodes in series with the + output rather than using a voltage regulator.  I think each diode drops it by 0.6v (though it might be 0.7v, you should check).  So two diodes in series would drop the voltage of 2 alkaline AAs by 1.2v, so 6v down to 4.8v.  I have no idea if that will work.  But NiMH AA's are 1.2v each, so 4.8v for four and WifiJeff reported that NIMH AAs didn't work the greatest, I'm not sure that alkalines plus a couple of diodes would work any better.  Something to experiment with, but using a 7805 5v voltage regulator off of 6v is not recommended and probably won't work too well.

[kskreider]

You're correct -- you should have at least a 2v differential, so at least 7v input for a 7805 5v regulator.  Doug Oade has suggested putting one or two diodes in series with the + output rather than using a voltage regulator.  I think each diode drops it by 0.6v (though it might be 0.7v, you should check).  So two diodes in series would drop the voltage of 2 alkaline AAs by 1.2v, so 6v down to 4.8v.  I have no idea if that will work.  But NiMH AA's are 1.2v each, so 4.8v for four and WifiJeff reported that NIMH AAs didn't work the greatest, I'm not sure that alkalines plus a couple of diodes would work any better.  Something to experiment with, but using a 7805 5v voltage regulator off of 6v is not recommended and probably won't work too well.

I actually bought a pack of 5.1v zener diodes when I got the rest of the parts and I was going to try one of those too. 

I will still try to run the lm7805 off of a 6v SLA and see what happens...just for shits and giggles.  It the meantime I am including a connector for a RC pack, so I can do 9.6v or 7.2v straight in.

[cmoorevt]

Thanks guys.  Very informative stuff. 

I asked because radio shack has all those supplies for one of the usb packs and I was going to try making one with the idea of using 4 AA.

WiFi Jeff reported in one of the other threads that today he used 4 lithium AA in the USB battery box and was at 8 hours of power and counting.  Pretty sure lithiums are 1.5 volts, so 6 total. That USB batt box must be using something to ramp it down to 5 volts, but maybe not the 7805 chip.  Of course they could be using diodes or something else, and we probably can't tell without taking one apart.

[Nick's Picks]

that slick ass voltage regulater from wallmart looks like a no brainer. 
I like no brainers.  suites me.

I have one that takes a 12v source and drops it down to 9.6, 7.2 and 6v.  but not 5.

[WiFiJeff]

The USB battery box with 4 lithium AAs (plus fully charged internal battery) ended up lasting just about 10 hours.  I don't know how good the voltage regulation of the box is, since even when the voltage dropped too low to run the MT the green light on the USB box was still glowing (as it was for the 1.2V NiMH cells, even when they pretty quickly stopped running the MT).  The lithium cells read okay but just on the border of okay/replace on my Radio Shack battery meter, when new they spike the meter all the way to the right.

Chris at SP is thinking of throwing one of these boxes in with orders for the MT, and is working on getting a custon shorter USB cable to connect them.

I have cycled the battery four or five times now, and am testing to see if there is any improvement in the life before testing regular alkaline cells.

Jeff

Edit: I got 3 hours from the MT without USB power again today.  No loss evident from the USB on/off cycling, no gain from coinditioning (or else they cancel out!!!)   

[oleg]

  the voltage can stay 6v but you dont have enough current to power your device .
the littium dont drop in voltage until they finally collapse , the same is with ni-mh they stay 1,2 v until 99% of their capacity , the meter can still read 6 vor 4,8) with nimh while there not  no enouth juice( power) in  the batteries at all .
the regullar alkaline , go down very fast  down in  voltage  under load , so it can be that even you use 4 that give you 6 v on open circuit they will very fast go under the minimum that usb need ,so actually you will not use all the capacity from the battery.
http://www.nimhbattery.com/delkin-rcr-123a-rechargeable-charger.htm
you can use these ( you need 2) in your box , the benefit of rechargeable lithium ion, they dont have big self discharge curv, less then 10% per year , so you dont have to remember to charge it if you did it ones and dint use it , the ni mh must  to been charge every time before use since drop very fast in self  capacity( the v stay 1.2)

[jason]

I mentioned this in a previous thread... I think most AA Lithium batts are between 1800-2200 mAH and coupled with the USB pack Jeff was able to get ~10hrs of recording.  The pricey $110 rechargable lithium USB power pack here: http://www.socketcom.com/product/AC4009-541.asp  is rated 7200 mAH (nominal 4400 mAH, I have no idea what the difference is between nominal and rated capacity) but even if its 2x what you get with normal lithiums, that would be approx 20 hrs of recording.   I'm realizing that the microtrack is probably less $ than one would end up spending compared to battery and CF card supplies...

[WiFiJeff]

I mentioned this in a previous thread... I think most AA Lithium batts are between 1800-2200 mAH and coupled with the USB pack Jeff was able to get ~10hrs of recording. 

The Battery Station lithium AAs ($1 each in packs of 20), which are supposed to be clones of the lithium Energizers, are labeled 2900 mAh.

Jeff

[F.O.Bean]

The USB battery box with 4 lithium AAs (plus fully charged internal battery) ended up lasting just about 10 hours.  I don't know how good the voltage regulation of the box is, since even when the voltage dropped too low to run the MT the green light on the USB box was still glowing (as it was for the 1.2V NiMH cells, even when they pretty quickly stopped running the MT).  The lithium cells read okay but just on the border of okay/replace on my Radio Shack battery meter, when new they spike the meter all the way to the right.

Chris at SP is thinking of throwing one of these boxes in with orders for the MT, and is working on getting a custon shorter USB cable to connect them.

I have cycled the battery four or five times now, and am testing to see if there is any improvement in the life before testing regular alkaline cells.

Jeff

could you just toss in another 4xAA's and do you think the MT would keep running or would the MT battery be too low to really start charging again at that point

[WiFiJeff]

could you just toss in another 4xAA's and do you think the MT would keep running or would the MT battery be too low to really start charging again at that point

I think you can just pull the USB box off and let it run on the internal battery, assuming you don't go right down to zero, and clip on another box or just put in new AAs and reconnect the old box.  NOT NiMH AAs, but lithiums.  I will test alkalines as soon as I finish testing whether I am getting better time from the internl battery alone.  (Doesn't look like it 1 hour into the test, though     )

Jeff

[jason]

I remember being told to discharge and recharge batts like laptop/cellphones etc...  and was wondering if by plugging in the USB power pack you are essentially simultaneously discharging/recharging the internal lithium batt of the MT - would that have an affect the life span on the batt since you're basically in a constant state of cycling??  I guess it also depends on whether it discharges faster than it recharges via USB.

[F.O.Bean]

+T jeff

great point jason, id def let the batts FULLY discharge then FULLY recharge!

[it-goes-to-eleven]

great point jason, id def let the batts FULLY discharge then FULLY recharge!

Unlike nicads, deep discharges are not good for lithium batteries.

[jason]

Even if they are not deep/complete discharges, is a state of constant cycling OK for lithiums??  I know for my laptop, I've always tried to keep a habit of disconnecting the Li batt when I have the lappy plugged into AC... I really have no idea, just curious.

[it-goes-to-eleven]

The big concern with lions in laptops is HEAT.  Lions really really hate heat. It greatly shortens their life.  So baking them while you're on a/c shortens their life due to the heat. Same thing about keeping them in a hot car.  They also don't last as long when kept fully charged.  But if you keep them in the fridge, fully charged is not so bad.  Also, Lions have a finite number of charge cycles.

I don't think most charging circuits would be constantly cycling as you describe.  But to operate and charge, the unit needs enough current.  That's why the internal battery stayed charged during the test with the lithium cells but not the nimh.


Great Lithium info:

http://www.batteryuniversity.com/parttw

Well.. No fedex micro tracker yet.. I want to get that thing on the charger for the show tonight (which is late but I want to get in early)!  Now I'm starting to wonder if I can feed it 5.0v from my jb3 setup (SIMA) and still run tonight..