# Rechargeable Battery Charging - Can it be interrupted and used for driving load

Discussion in 'Homework Help' started by ICD_life, Jan 6, 2015.

1. ### ICD_life Thread Starter New Member

Nov 12, 2014
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Battery Spec: peak voltage - 3.8V, 14mAH Capacity.

During the charging of the battery , could I use the battery voltage say @1V to power up a Charge Pump (18UW power) to aid the charging process?

Kindly let me know.

Thanks.

2. ### MikeML AAC Fanatic!

Oct 2, 2009
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The energy to recharge a battery must come from an external source.

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3. ### ICD_life Thread Starter New Member

Nov 12, 2014
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Yes the input to charge pump is an external energy source ....

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4. ### Kermit2 AAC Fanatic!

Feb 5, 2010
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if your charger is active at the time you use thr battery, the charger will supply the power to ALL loads unless the load draws more current than the charger can supply. at which point the circuit voltage will droop and when it drops low enough the battery will begin to contribute its current to the load. all charging action stops at this point and the battery is being discharged

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5. ### MikeML AAC Fanatic!

Oct 2, 2009
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In your initial question, I thought you were proposing powering the charge pump from the battery being charged thereby making a perpetual motion machine which violates the laws of thermodynamics.

Are you proposing charging the battery using an externally powered charge-pump only when the battery voltage is below 1V? If so, what is magic about 1V? Shouldn't the end-of-charge condition for the battery be more like 4v?

What is the role of the charge pump? Is it in addition to a conventional charger? Or is it supposed to replace it?

6. ### MrAl Well-Known Member

Jun 17, 2014
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Hi,

It sounds like what you are saying is that if the battery voltage is low to begin with (like 1v) then can you increase the charge rate by using another circuit that runs off of the battery voltage itself.

If this is true then this is an interesting question because voltage itself could be viewed as existing in a different dimension than current, and so having voltage to work with could mean we might be able to convert the power to a more useable form for a given application.

However, experience shows that the best idea is to simply convert the input power to a better form and go with that instead of trying to do it later. This means it would be better to simply build a better battery charger to begin with that can utilize the input power to it's fullest extent. If the charger does not work as well as it can to begin with, then the charger itself should be modified rather than trying to tack on an additional circuit.

7. ### ICD_life Thread Starter New Member

Nov 12, 2014
9
0
Hello,

Sorry my question and the background is unclear.

I have an external voltage source 1.2V
The charge Pump Specs: Works at 1V supply with current consumption of 18uA
Now I have to charge a completely drained battery whose Spec is Voltage 3.8V, 14maH capacity.

So I am using a charge pump intermediate which triples the external voltage voltage source 1.2V to 3.8V, There are multiple ways to implement. If I implement like above picture.
Could I Use the battery as supply to charge pump ?

Basically I am asking can a half charged battery be used to aid a load while charging? Or do I have to charge a battery with no load untill it reaches 3.8V?

Regulator in the picture is the Voltage Reference to the Charge Pump.