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Author Topic: need help in selecting batteries  (Read 900 times)

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Offline ratulxyTopic starter

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need help in selecting batteries
« on: December 21, 2010, 09:10:40 AM »
i have a DC motor that requires 2 Amp power at 8.4 volts.....what would be the best possible battery(and cheap too)...i need it to power my hovercraft.i use a 7.4 volt,2000mAh battery...but still it does not work....

Offline rbtying

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Re: need help in selecting batteries
« Reply #1 on: December 21, 2010, 09:45:00 AM »
You absolutely require 8.4v? In that case, NiMH is probably the best.  As we don't know your weight requirements, we can't tell you anything about desired weight or etc. 

Is your 7.4v battery a lithium battery? You may want to try adding another cell to make it 11.1v, which should be more than enough for your craft.

Offline Soeren

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Re: need help in selecting batteries
« Reply #2 on: December 21, 2010, 10:12:44 PM »
Hi,

i have a DC motor that requires 2 Amp power at 8.4 volts.....what would be the best possible battery(and cheap too)...i need it to power my hovercraft.i use a 7.4 volt,2000mAh battery...but still it does not work....
You can get get both cheap and very good, but unfortunately not at the same time.
If your "still does not work", is about lift (or rather the lack of it), you need more than a single Volt extra.
Since you haven't got enough lift (still assumed), you don't want to add weight, so you need to go for lithiums (see, cheap and good don't go well together).

You don't need 2000mAh cells for a 2A current draw. The "h" (meaning hours) in the former makes it a capacity spec. not a current spec like the latter.
a 600mAh battery can drive a 2000mA motor for (500mAh/2000mA) around a quarter of an hour (not a mistype/miscalculation, but the capacity falls with large current draws).

All that apart... If you have trouble getting lift, you might wanna reconsider the entire construction, its materials, the motor (type, speed and torque ratings), the skirting material etc. etc.

Best type of motor here is a brushless, considering weight to power relation.


You could post some snaps of what you have build, list its weight, RPM of the motor you have, what do you use for propellor, what building material etc. and you would surely get some advice on what works and what needs replacement.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline ratulxyTopic starter

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Re: need help in selecting batteries
« Reply #3 on: December 25, 2010, 08:44:48 AM »
You absolutely require 8.4v? In that case, NiMH is probably the best.  As we don't know your weight requirements, we can't tell you anything about desired weight or etc. 

Is your 7.4v battery a lithium battery? You may want to try adding another cell to make it 11.1v, which should be more than enough for your craft.
i forgot to add that the rating of the motor is 4.8-8.4 V......and yes it is lithium ion battery....

 


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