Understanding the conversion of a chargers output to time to charge

[dealer of aces]

I'm trying to understand the theoretical components of time to charge for a device.  Let's assume that a battery is 2000 mAh.  Power = Voltage * Amp.  So lets take a charger that charges at both 24v 1 amp and 12v 2 amps.  That provides us with a 24 watt output on both.  Everything I've been able to find talks about discharge time being battery size divided by discharge rate.  I want to know the reverse.  How do we get from a 24 watt charger to filling the capacity of the 2000 mAh battery.  As far as charging rate goes is there a difference between 24v 1 amp and 12v 2 amps?  How can I take the wattage of a charger and convert that into mAh?

 

Regards

 

I had some electrical engineering courses in college so speak as technically as you would like.  Unfortunately I don't remember some of the specific content do to a head injury but I understand conceptually most things.

[BrinkGG]

23 minutes ago, dealer of aces said:

I'm trying to understand the theoretical components of time to charge for a device.  Let's assume that a battery is 2000 mAh.  Power = Voltage * Amp.  So lets take a charger that charges at both 24v 1 amp and 12v 2 amps.  That provides us with a 24 watt output on both.  Everything I've been able to find talks about discharge time being battery size divided by discharge rate.  I want to know the reverse.  How do we get from a 24 watt charger to filling the capacity of the 2000 mAh battery.  As far as charging rate goes is there a difference between 24v 1 amp and 12v 2 amps?  How can I take the wattage of a charger and convert that into mAh?

 

Regards

 

I had some electrical engineering courses in college so speak as technically as you would like.  Unfortunately I don't remember some of the specific content do to a head injury but I understand conceptually most things.

So you're missing something important here: Voltage of the battery. 

To be able to do any math here, you need 2 out of the 3 (voltage, wattage, or amperage). 

if the voltages of the battery and the charger output voltage is the same, it's just total amp-hours of the battery, divided by amperage output of the charger. Example: 12v 2000mAh battery, and the charger is 12v / 2A, The equation that I remember is as follows: 2000 mAh / 2000 mA (converting to same unit) = 1h. You do have efficiency loss thanks to heat and resistance, which usually works out to around a 1:1.4 ratio. So at the end of the equation, multiply your hour by 1.4 and that will give you an estimate. 

 

If it's different voltages, I THINK you just convert both to watts, then divide again, then multiply by 1.4. 

[dealer of aces]

Just now, James Evens said:

You can't do this. Batterys are not charged with constant current. It is lowered if the battery is at higher charge. Also don't forgett the efficincy.

I understand there are many factors that play into Ohm's law when applied but I was looking for the theoretical calculations just to understand the idea behind how it works better as @Brink2Three answered wonderfully.  

 

I believe the issue was I remember just enough of the basics to confuse myself.  When searching for my answer I wasn't typing in the correct information which led me down a rabbit hole.  Thanks for the answers!

[BrinkGG]

9 minutes ago, dealer of aces said:

I understand there are many factors that play into Ohm's law when applied but I was looking for the theoretical calculations just to understand the idea behind how it works better as @Brink2Three answered wonderfully.  

 

I believe the issue was I remember just enough of the basics to confuse myself.  When searching for my answer I wasn't typing in the correct information which led me down a rabbit hole.  Thanks for the answers!

No problem. Glad I could help! Sorry about the head injury. I have LTMR (Long term memory loss) caused by Lyme's Disease so anything over about 10 years old I just don't have anymore, so I know the feeling. 

[dealer of aces]

48 minutes ago, Brink2Three said:

No problem. Glad I could help! Sorry about the head injury. I have LTMR (Long term memory loss) caused by Lyme's Disease so anything over about 10 years old I just don't have anymore, so I know the feeling. 

I understand that completely.  It can be very frustrating to try to recall certain bits of information when you know you knew it at one point but just can't make that connection.  My injury was due to my motorcycle being struck by an 18 wheeler.  Fun times!

[Mira Yurizaki]

I think this page should help explain the basics, at least for a type of lithium rechargeable: https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries, but the overall process is described at https://batteryuniversity.com/learn/article/all_about_chargers

 

However what really affects the charging time is the C rate, or the amps you feed into the battery vs. its capacity. A higher C rating lowers the charging time, but also introduces problems like current heating. Voltage has nothing to do with it because you're usually providing a fixed voltage to the battery, typically at or slightly higher than its open circuit voltage. If you give the battery too much voltage, you could break down the composition in the battery, leading to a catastrophic failure.

[dealer of aces]

On 10/15/2018 at 3:59 PM, M.Yurizaki said:

I think this page should help explain the basics, at least for a type of lithium rechargeable: https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries, but the overall process is described at https://batteryuniversity.com/learn/article/all_about_chargers

 

However what really affects the charging time is the C rate, or the amps you feed into the battery vs. its capacity. A higher C rating lowers the charging time, but also introduces problems like current heating. Voltage has nothing to do with it because you're usually providing a fixed voltage to the battery, typically at or slightly higher than its open circuit voltage. If you give the battery too much voltage, you could break down the composition in the battery, leading to a catastrophic failure.

Thank you!  Those links are very informative.