Author Topic: Li pack balancer for discharge?  (Read 778 times)

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Offline newInRoboticsTopic starter

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Li pack balancer for discharge?
« on: February 27, 2011, 08:03:03 PM »
Do I need to use a balancer for Li-Ion pack while it's being discharged (connected to the robot), or is it used only for charging the pack?
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Offline rbtying

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Re: Li pack balancer for discharge?
« Reply #1 on: February 27, 2011, 11:18:27 PM »
You need one if you want to charge the battery, or discharge the battery WITHOUT another load (for capacity testing, usually).

For running the robot, you should use the primary power leads, which will have the cells connected probably in series.

Offline newInRoboticsTopic starter

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Re: Li pack balancer for discharge?
« Reply #2 on: February 28, 2011, 09:29:58 AM »
Balancer is for batteries in series, isn't it? Batteries in parallel balances automatically (as far as I know).

So if for any possible reason batteries my not be charged equally (some get overcharged, some undercharged), how come they can be discharged equally?
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Offline Soeren

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Re: Li pack balancer for discharge?
« Reply #3 on: February 28, 2011, 02:22:56 PM »
Hi,

So if for any possible reason batteries my not be charged equally (some get overcharged, some undercharged), how come they can be discharged equally?
They get an even charge because of the balancers, which is there to counter eventual uneven discharge (it's just a little bit each discharge).
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Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
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Offline newInRoboticsTopic starter

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Re: Li pack balancer for discharge?
« Reply #4 on: March 02, 2011, 04:36:23 PM »
They get an even charge because of the balancers, which is there to counter eventual uneven discharge (it's just a little bit each discharge).
I know that batteries get charged evenly because of the balancer, hence we use balancer.My question was: Should I use balancer while battery pack is connected to the robot, or balancer is used only while charging?

And then the second post question was: If battery pack gets unbalanced while charging without balancer, can it get unbalanced while discharging without balancer?
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

Offline Soeren

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Re: Li pack balancer for discharge?
« Reply #5 on: March 02, 2011, 07:19:52 PM »
I know that batteries get charged evenly because of the balancer, hence we use balancer.My question was: Should I use balancer while battery pack is connected to the robot, or balancer is used only while charging?
The answer to that is somewhat intrinsic to what I wrote.


And then the second post question was: If battery pack gets unbalanced while charging without balancer, can it get unbalanced while discharging without balancer?
If the pack is unbalanced when you start discharging it, it doesn't get unbalanced, it IS so already.
It will only get worse each charge and discharge until proper balancing is used at every charge (or it's converted to a fireball, whatever comes first.

Stop playing with lithiums and get a proper charger, it's much safer and judging from some of your posts, I am not too convinced your experience is enough that you could make a safe charger, even if you used a dedicated lithium charger chip.

Grind your fangs on something like NiMH instead, it's much safer and the experience you build along the way will be worth it.
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

 


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