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Author Topic: Build-in battery charger?  (Read 4125 times)
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Hi all,

this is isn't exclusively Arduino-related, but I can't find any entry-level info on Google...

I'd like to be able to charge the battery in my Arduino device a) without removing the battery pack and b) while the device is switched on and operating. Same behavior as a cell phone or ipod.

I guess this requires a charging circuit in the device, a circuit decoupling it from the arduino while powering it at the same time, and a regular DC adapter. But don't really know how these would be implemented.

Can somebody point me in the right direction to learn more about this?

Thanks a lot!
« Last Edit: January 16, 2008, 03:16:14 am by mymonkeyandme » Logged

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What type of battery first?
NiMH, NiCad, Li-ion or Lead Acid?

Charging while the circuit is on is simple.
You dont have to do anything special, just hook up the charging circuit.
The charger will power both the circuit and charge the battery at the same time.
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Thanks.

Probably NiMH, maybe Li-Ion. Is there a difference in complexity for the circuit depending on the type used?
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Yeah each type of battery needs a different type of charger.

Lead acid is easiest, Li-ion is hardest.
There are plenty of tutorials around though.
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Maxim has an IC specifically designed to charge a lithium ion battery from USB (+5V).  Could be a good fit for a USB Arduino shield.

Is it the MAX1555?  can't remember.  I think Sparkfun has them, and of course the Maxim web site will find it.

-j

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If you want the battery to power the board while on charge, make sure that the voltage of your fully charged battery is less than 6 volts. If you decide to use NiMH cells then don't forget that a full charged fresh  four cell battery can exceed this.

In my app i wanted more than 5 volts to drive some servos so used a 5 cell NiMH pack and replaced the 7805 5v regulator  with a LF50CV low dropout part (http://www.mouser.com/Search/Refine.aspx?Ntt=511-LF50CV) to ensure the chip was protected.

My charging circuit consists of a 10 ohm resistor that provides trickle charging current from the external power supply to the battery.
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I need a simple charging circuit for a 9V NiMh battery. but i cannot find any online anywhere smiley-sad its all NiCad and i dont want that..

can anyone help? i need it so i dont have to fork out for non rechargeables
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For a simple charging using constant current, you can use the same circuit as for nicads.

However, charging circuits that detect peak voltage do need to be different for NiMH cells.
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Quote
What type of battery first?
NiMH, NiCad, Li-ion or Lead Acid?

Charging while the circuit is on is simple.
You dont have to do anything special, just hook up the charging circuit.
The charger will power both the circuit and charge the battery at the same time.

Ummmm.... I'd be very careful about that assumption.  I have a set of 6v NiCd batteries, and the charger puts out 12 volts.  Also, (at least for NiCd) the charger supplies LESS current than the battery, unless you have an "instant" charger.  Hooking my NiCd charger to the power supply would a) fry it from over-voltage and b) not have enough current to run everything.

That's not to say that some chargers won't work this way, but you can't assume that they will.
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Ni-Cad and Ni-MH chargers are similar. You often get chargers with a switch to change between them.
I dont know the differences though.
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i just need a really simple digram (and i mean Simple smiley ) that i can throw together and charge my 9v cells (uniross 160 mAh 8.4v) most i find are for AA cells and the like.. smiley-sad
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If you want the battery to power the board while on charge, make sure that the voltage of your fully charged battery is less than 6 volts.
Could you please explain to me why this is required? Thanks. smiley

--Phil.
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What I meant was that if you power the board directly (not via the regulator) then the voltage must be less then 6 volts.

If powering through the regulator then that's not an issue, but the battery voltage must be greater then  the regulators dropout voltage.
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What I meant was that if you power the board directly (not via the regulator) then the voltage must be less then 6 volts.

Ah, I follow you now.

In relation to your original comment, you wouldn't actually want to power the board directly from the battery due to it being an unregulated supply, would you?

--Phil.
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Quote
What I meant was that if you power the board directly (not via the regulator) then the voltage must be less then 6 volts.

Ah, I follow you now.

In relation to your original comment, you wouldn't actually want to power the board directly from the battery due to it being an unregulated supply, would you?

--Phil.
I have various equipment in my radio control gliders that use embedded mirocontrollers that are connected directly to a battey without a regulator. I would think an arduino would not be a problem on a battery as long as there were no significant power spikes.
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