Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: Blood-man on July 28, 2009, 05:08:51 PM
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i bought an 6v 1400mAh NiMH Battery at ebay: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380124849048 for my $50 robot. I also found old charger. It says 'Output: 6v 600mA. Would it be fine to charge this battery?
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do you have more information on the charger?
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I'm pretty sure it should work fine... it will just take longer to charge.... so like 2 and a half hours charge time?
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and you wont be able to charge to its optimal level...
most batteries use a charging voltage one or two volts higher than their rated voltage to charge.
ever notice how your battery is at 6V5 or 7V when fully charged? thats why :P
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its is fine to charge his battery but not to optimal levels...
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yup, thats what i was saying...
just be sure to monitor the battery the first few times of charging... incase it decides to start a fire...
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of course he could always draw a volt offf of a parallel or serial port
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your kidding right?
for some odd reason that screams "fried port" to me ::)
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I would think it would work... ive drew power off of one to charge my cell phone before... make two jumper wires one in the v+ and one in the ground... for one volt....
disclaimer im not responsible if this does mess your computer up
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lol, parallel port. Seriously, does anyone still have a computer with a parallel port? Even a serial port? Those are getting rare too, especially with USB now. there is usb everything.
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i do on my old computer but my new computer no... but i do have a usb to serial converter... and like 6 usbs, sd card slots and a firewire so im good
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you bagging on my old pc? lol, 6 years and still running strong (with upgrades).
but even some newer pc's still have serials, my mum bought a laptop at the start of this year and it has a serial port.
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I know hps dont have them on there computers anymore... of course to get a good computer you have to build it yourself... the average large company(dell, hp, etc.) needs to be upgraded with in three years because there built to make you repair or have to buy them right after the warranty goes... main reason is money...
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Hi,
I also found old charger. It says 'Output: 6v 600mA. Would it be fine to charge this battery?
It depends...
If you by chargrer mean a "wall wart", the 6V marking is the nominal voltage at a load current of 600 mA (well, it's supposed to be at least), and the unloaded output voltage will be higher.
You have to measure the output voltage when drawing say ~10 mA and eg. ~300 mA to find out for sure whether it can be used as a taper charger for your 5-cell battery.
A fresh charged 5-cell nickel based battery will have a terminal voltage of 7.00V to 7.25V right off the charger.
(It will soon go down to ~6,75V after a light loading or after sitting around for a while).
That means that your charger must put out between 7.00V and 7.25V when a load of 10mA to 15 mA is used and you should limit the current if the battery gets over 35°C at any time during charging (if you burn your fingers touching it, you are damaging the battery).
To measure the battery, apply a load of 680 Ohm (1/4W will do). If you get a reading of 7.0V to 7.25V, you can use the charger. Anything less (or higher) won't help.
With a load of 22 Ohm (2W minimum), you can find if the charger has got enough power for the purpose.
Don't ever, even for a second, consider mixing PC port voltages into the equation - that is a ticket to serious disaster.
When you have measured up the charger, post your findings for a go/no-go evaluatiion.
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Hi,
I also found old charger. It says 'Output: 6v 600mA. Would it be fine to charge this battery?
It depends...
If you by chargrer mean a "wall wart", the 6V marking is the nominal voltage at a load current of 600 mA (well, it's supposed to be at least), and the unloaded output voltage will be higher.
You have to measure the output voltage when drawing say ~10 mA and eg. ~300 mA to find out for sure whether it can be used as a taper charger for your 5-cell battery.
A fresh charged 5-cell nickel based battery will have a terminal voltage of 7.00V to 7.25V right off the charger.
(It will soon go down to ~6,75V after a light loading or after sitting around for a while).
That means that your charger must put out between 7.00V and 7.25V when a load of 10mA to 15 mA is used and you should limit the current if the battery gets over 35°C at any time during charging (if you burn your fingers touching it, you are damaging the battery).
To measure the battery, apply a load of 680 Ohm (1/4W will do). If you get a reading of 7.0V to 7.25V, you can use the charger. Anything less (or higher) won't help.
With a load of 22 Ohm (2W minimum), you can find if the charger has got enough power for the purpose.
Don't ever, even for a second, consider mixing PC port voltages into the equation - that is a ticket to serious disaster.
When you have measured up the charger, post your findings for a go/no-go evaluatiion.
what? I was in high school when I did that... lol :P
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the pc port thing? then its fine, just don't do it with your pc :P
the other option is to put a buck/boost regulator into the equation?
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Hi,
[...] the other option is to put a buck/boost regulator into the equation?
Better to make a better charger - I'd suggest the MAX712 a dV/dT-terminating charger http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1666/t/al (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1666/t/al). It charges from 1 to 16 cells at up to 2A max (and free samples are available).
Look at the app. notes a bit down on the MAX712 page as well (even those using the MAX713), there are stuff to be learned in them.
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Hi,
[...] the other option is to put a buck/boost regulator into the equation?
Better to make a better charger - I'd suggest the MAX712 a dV/dT-terminating charger http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1666/t/al (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1666/t/al). It charges from 1 to 16 cells at up to 2A max (and free samples are available).
Look at the app. notes a bit down on the MAX712 page as well (even those using the MAX713), there are stuff to be learned in them.
I just got that IC with my last digikey order. =P