Battery Recharging Circuit Assistance

Thread Starter

Stovie

Joined Feb 17, 2020
5
Hello, I am currently working on a subsystem of a project and have ran into a roadblock of sorts. I need to make a rechargeable battery circuit (12V using a battery pack of 8 AAs is what is being used currently) that will activate in the event of the 12V main power going down. Ideally, when not in use, the battery circuit will be able to charge via the main power source. The current design I have allows for the batteries to charge, but there is nothing in place preventing it from overcharging, causing damage. Is there some sort of solution for this? The ideal solution I am looking for, if it exists, would be that the batteries would be charged to 12V, then stop charging. To put it simply.
 

MisterBill2

Joined Jan 23, 2018
5,242
Some types of batteries have a specified "float" voltage which can be applied constantly and not cause an overcharge, while stll holding them at full charge. For that you need a stable regulated supply that is set to the correct voltage.
 

Thread Starter

Stovie

Joined Feb 17, 2020
5
I am currently using Ni-Mh batteries. I was hoping someone had a circuit schematic that may work as a solution.
 

Picbuster

Joined Dec 2, 2013
990
Hello, I am currently working on a subsystem of a project and have ran into a roadblock of sorts. I need to make a rechargeable battery circuit (12V using a battery pack of 8 AAs is what is being used currently) that will activate in the event of the 12V main power going down. Ideally, when not in use, the battery circuit will be able to charge via the main power source. The current design I have allows for the batteries to charge, but there is nothing in place preventing it from overcharging, causing damage. Is there some sort of solution for this? The ideal solution I am looking for, if it exists, would be that the batteries would be charged to 12V, then stop charging. To put it simply.
Look at the lt1513-2

Picbuster
 

Thread Starter

Stovie

Joined Feb 17, 2020
5
8 Ni-Mh batteries has a nominal output of about 9.6V.
You need 10 cells to give 12V.
True. After checking the load (electric lock actuator), the nominal voltage of 9.6V is enough to activate the lock. It functions fine, I just need to have something in place to keep the batteries at nominal voltage.
 

crutschow

Joined Mar 14, 2008
24,403
NiMh batteries can be continuously trickle charged with a current no greater than 0.05 of the battery Ah rating.
That should be sufficient to keep the battery charged if the battery is only used infrequently.
 

Thread Starter

Stovie

Joined Feb 17, 2020
5
NiMh batteries can be continuously trickle charged with a current no greater than 0.05 of the battery Ah rating.
That should be sufficient to keep the battery charged if the battery is only used infrequently.
thanks for the info! The only issue now would be the overcharging prevention
 

MisterBill2

Joined Jan 23, 2018
5,242
The charge current can be kept indefinitely at 0.05 of the Ah rating or less without overcharging.
That can be done with a proper sized resistor to the charging source.
I suggest also having a voltage regulator before that "properly sized resistor to assure that variations do not lead to an overcharge situation.
 
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