Charging a Li-ion Battery of 25.9 V and 5.5Ah

[bobparihar]

My aim is to develop a charger of a Li ion Battery of the following specification
voltage 25.9V
capacity 5.5Ah
i dont know how much cell it contains..nor i am having any document where i could find this.
i want to charge it by the means of energy conservation.. for that i selected a piezoelectric charging system by shoes..it can charge a standard Duracell 9V battery of capacity about 500-600 mA
now how much time and battery of such 9V require to charge that Li on Battery of 25.9V?

 

[alec_t]

How long does the piezo charger take to fully charge the 9V 500mAh battery?

 

[audioguru]

You cannot charge a Duracell Copper top or Quantum alkaline disposable cell. Duracell does not make a 9V Ni-MH re-chargeable battery.

 

[Bob Parihar]

You cannot charge a Duracell Copper top or Quantum alkaline disposable cell. Duracell does not make a 9V Ni-MH re-chargeable battery.

Obviously I need a rechargeable battery I was just giving a example of 9v Duracell for its capacity and voltag

 

[audioguru]

Why did you say that somebody used a piezo in a shoe to charge a 9V/500mAh battery?
1) A piezo produces an extremely low current so it takes a very long time to charge a much smaller battery. The link or video I posted used a huge piezo in a shoe to charge a tiny 8mAh battery after millions of steps.
2) Nobody makes a 9V/500mAh rechargeable battery. The Energizer 9V Ni-MH battery is only 175mAh.
3) Somebody installed hundreds of piezos on a sidewalk where thousands of people walked every day. A little battery was charged to light an LED at night like a cheap little solar garden light.

EDIT: Any document about Li-Ion batteries say that they are charged to 4.2V per cell and the load should be removed when the voltage has dropped to 3.2V. Then they say the average voltage is 3.7V per cell. Your battery averages 25.9V so how many cells does it have??

 

[bobparihar]

ok i think i have to skip the idea of charging using Piezo
and, now i am thinking of doing it using generator which will generate the voltage by means of paddling
but i have no idea that what specification of motor i need.. and i have to develop a charger which must have the following feature
a) Over Voltage Protection:
b) Output Reverse Protection: The charger will be cut off when the battery polarity is
wrongly placed.
c) Short Circuit Protection: The charger will be cut off automatically when a short circuit
is detected.
d) LED indicates the charging status.
e) Built in IC to cut off power automatically when the battery is fully charged

please suggest me some circuit diagram according to my need

 

[audioguru]

Paddling on a road??
Do you mean a paddle wheel in a river? Many river generators are turbines. A windmill would be easier. Or use solar panels.
Do you still want to charge a 7-cells 29.5V/5.5Ah Lithium battery? Then use a battery charger IC made to charge a Lithium battery.

 

[alec_t]

I suggest a trip to www.batteryuniversity.com to research the charging profiles required for various battery types. Lithium batteries, in particular, require proper charging/discharging to avoid fires and exploding batteries.

 

[bobparihar]

Paddling on a road??
Do you mean a paddle wheel in a river? Many river generators are turbines. A windmill would be easier. Or use solar panels.
Do you still want to charge a 7-cells 29.5V/5.5Ah Lithium battery? Then use a battery charger IC made to charge a Lithium battery.

yes the target battery is still 7 cells 29.5V/5.5 Ah Li-ion battery
i cant use solar or windmill..
i have to use a system like a gym bicycle that stands stationary at a place or like a sewing machine paddling machine

 

[alec_t]

If the 7 cells are permanently in series you will need a complicated charger to ensure charge balancing. Do the cells have safety circuits to ensure no cell gets over-charged or over-discharged?

a sewing machine paddling machine

I'm guessing you mean a treadle-operated sewing machine?

 

[bobparihar]

If the 7 cells are permanently in series you will need a complicated charger to ensure charge balancing. Do the cells have safety circuits to ensure no cell gets over-charged or over-discharged?

I'm guessing you mean a treadle-operated sewing machine?

Exactly i was planing treadle-operated sewing machine..
actually i don't know that my battery has 7 cell in series or not..how to find that?

 

[audioguru]

i don't know that my battery has 7 cell in series or not..how to find that?

Then you know nothing about Pi-Ion cells. Any document about Li-Ion batteries say that they are charged to 4.2V per cell and the load should be removed when the voltage has dropped to 3.2V. Then they say the average voltage is 3.7V per cell. Your battery averages 25.9V so how many cells does it have??

 

[Bob Parihar]

Then you know nothing about Pi-Ion cells. Any document about Li-Ion batteries say that they are charged to 4.2V per cell and the load should be removed when the voltage has dropped to 3.2V. Then they say the average voltage is 3.7V per cell. Your battery averages 25.9V so how many cells does it have??

What are the other possibilites of the battery.. I mean it is mendetory that my battery must have 7 cell in series? What are other possibilities

 

[audioguru]

As I said before, a Lithium-Ion battery with 7 cells in series produces 22.4V when the battery is almost dead and should have its load disconnected. It is 29.4V when the battery is fully charged. It averages 25.9V during a discharge.
Two 12V lead-acid batteries in series will average about 26.4V during a discharge.

 

[Bob Parihar]

As I said before, a Lithium-Ion battery with 7 cells in series produces 22.4V when the battery is almost dead and should have its load disconnected. It is 29.4V when the battery is fully charged. It averages 25.9V during a discharge.
Two 12V lead-acid batteries in series will average about 26.4V during a discharge.

Thanks for your cooperation sir
I have an idea of charging the li ion battery using an alternator of 24V i have researched that a 24V alternator gives 28.4 V output.. I think this voltage is sufficient to charge my 25.9 V battery..
I want to rotate the alternator with a bicycle.. Will this idea of charging will work? what addition should i have to do?

 

[audioguru]

You also need a Lithium charger IC that does a lot of things to prevent the Lithium battery from catching on fire. You do not want to be near an extremely hot Lithium fire that is almost like a Magnesium fire (flares are Magnesium).

 

[alec_t]

According to Wikipedia, "adults of good average fitness average between 50 and 150 watts for an hour of vigorous exercise. A healthy well-fed laborer over the course of an 8-hour work shift can sustain an average output of about 75 watts."
On that basis, let's assume you can average an output of 70W while cycling.
Your 25.9V 5.5Ah battery stores ~ 142Wh of energy, so if we assume 50% efficiency in converting all your cycling energy to electrical energy (i.e. you are using a static cycle, not one on the road) it would take ~ 2 x 140/70 = 4 hours of continuous cycling at maximum speed to charge the battery fully with that alternator!

 

[Bob Parihar]

According to Wikipedia, "adults of good average fitness average between 50 and 150 watts for an hour of vigorous exercise. A healthy well-fed laborer over the course of an 8-hour work shift can sustain an average output of about 75 watts."
On that basis, let's assume you can average an output of 70W while cycling.
Your 25.9V 5.5Ah battery stores ~ 142Wh of energy, so if we assume 50% efficiency in converting all your cycling energy to electrical energy (i.e. you are using a static cycle, not one on the road) it would take ~ 2 x 140/70 = 4 hours of continuous cycling at maximum speed to charge the battery fully with that alternator!

Thanks for informing sir...
I will use some kind of gear mechanism which will generate more rpm as compared to normal..
I heard from some electrician that alternator has inbuilt IC circuit which will automatically detect that its a li ion battery and charge according to it...., is it??

 

[alec_t]

I heard from some electrician that alternator has inbuilt IC circuit which will automatically detect that its a li ion battery and charge according to it...., is it??

I'd be very surprised if that were the case.
Good luck with all your cycling. Should keep you fit .

 

[Bob Parihar]

I'd be very surprised if that were the case.
Good luck with all your cycling. Should keep you fit .

Update me if u find something