Analog Based Battery Balancing System

Thread Starter

CircuitRust

Joined Aug 29, 2016
1
Hi,

I'm trying to build a purely analog based battery balancing system. So far, I'm having a hard time building a circuit that would just be analog based since most system out there rely on some kind of microprocessor that monitors voltage.

Here's a my thought process so far

Two Battery Cells > Compares two voltage w/ voltage comparator > Switch (Need to be analog) > Add voltage through capacitor/inductor > Repeat

So far, In order to detect the voltage of the cell battery, i chose to go with a voltage comparator. I've been digging around and can we use transistors as a management to switch between the capacitor/inductor back to the cell?

Any feedback is welcome! Just looking at what kind of components I can use to make this happen!

Cheers
 

AnalogKid

Joined Aug 1, 2013
10,987
Two Battery Cells > Compares two voltage w/ voltage comparator > Switch (Need to be analog) > Add voltage through capacitor/inductor > Repeat
Are you talking about load balancing or charge balancing? Very different animals. Also, you don't "add voltage" to a battery. You add charge by connecting the battery to a voltage source or current source.

Don't know your background, so just to make sure... By "voltage source" and "current source" I mean two different types of power supply circuits.

ak
 

inwo

Joined Nov 7, 2013
2,419
Keep us informed on any progress. I would like to actively balance 24s.

If you have any interest in shunt balancing, I'll send you a 12s pcb. Could use some input.

Might try dissecting a <$10 7s balancer.

What rate are you shooting for?
 

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ronv

Joined Nov 12, 2008
3,770
Hi,

I'm trying to build a purely analog based battery balancing system. So far, I'm having a hard time building a circuit that would just be analog based since most system out there rely on some kind of microprocessor that monitors voltage.

Here's a my thought process so far

Two Battery Cells > Compares two voltage w/ voltage comparator > Switch (Need to be analog) > Add voltage through capacitor/inductor > Repeat

So far, In order to detect the voltage of the cell battery, i chose to go with a voltage comparator. I've been digging around and can we use transistors as a management to switch between the capacitor/inductor back to the cell?

Any feedback is welcome! Just looking at what kind of components I can use to make this happen!

Cheers
I'm not sure exactly what you want to do but I think I do. :D
Several years ago I built a switched capacitor balancer for my golf cart. Basically what it did is this: It would switch a large capacitor across the first battery and allow a little time for it to charge. Then it would switch that capacitor across the next battery in the string. If the first battery was at a higher voltage the cap would discharge into the second battery or vice versa. There was no change to the original charger so it managed the total voltage/current as it did before. I left it on all the time as it drew very little current. I probably still have a schematic somewhere if this is what you are looking for.
 

ian field

Joined Oct 27, 2012
6,536
A short time ago was written quite a bit on shunt-balanced charging in this thread: High current shunt circuit
For some years now, I've been using TL431 based shunt regulators on single lithium cells for an e-cigarette.

There are some applications in consideration that require multiple cells, the TL 431 could work, but they need a resistor divider that will leak a small current even when the battery is not in use.

My idea so far; is to switch in the shunt regulators with a multi pole relay energised by the charger - when the charger is off or unplugged, the relay drops out and isolates the shunt regulators.

The TL431 can handle 100mA, for moderate current it can be boosted by a PNP power transistor in a hybrid Szicklai arrangement. More current can be accommodated if the TL431 current develops a voltage across a small resistor to drive an common emitter PNP signal transistor - that in turn drives the gate of a logic level power N-channel MOSFET that carries pretty much all of the shunt load.
 
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