How to balance charge 12V worth of Ni-MH batteries automatically in circuit

Projects General Guidance
1

Hi. The following website explains how to make a 12V NiMH battery float charger.

https://www.eeweb.com/blog/extreme_circuits/float-charger-for-nimh-cells

Below I will post in order

  1. My circuit (which works)
  2. The float charger circuit (12V version - 10 cells)
  3. My proposed circuit which will charge the batteries whenever the DC plug is attached.

I'm 97% certain that something will be wrong/inadequate, so I am looking for ways to make it work.

I have a feeling that the charger circuit does not do balance charging, due to the lack of mosfets.

The added circuitry needs priority over the charging circuit, but I feel like having the charger and circuit in parallel, they are both going to just draw the current they both need.

Note: my circuit draws 47uA when only the PIR is active and up to 200mA when the Arduino is on (the mosfet turns it on).

I would go ahead and try it if my stuff was not in storage right now.

See "proposed circuit.png".

Thanks!

working circuit.png

Float_charger_NiMH_Cells_Circuit_Diagram-1366318812.jpg

proposed circuit.png

2

Any thoughts? The power pack should charge the batteries and power the circuit at the same time right? They are in parallel. Will the batteries being in series like this get wrecked quickly? The current is still limited, which is what I think they mean by constant current (CC). Low currents from time to time (taken by the circuit) will damaged the batteries?

3

It seems that no person who is an expert on charging NiMh cells has noticed your Thread.

Charging batteries safely is outside the scope of this Forum. Have you asked advice where you got the link you posted?

...R

4

There is a lot of information about battery charging at the Battery University website.

This page is specifically about NiMH cells.

I can't see anything mentioned about them requiring a balance charging, maybe that is something only required by Lithium cells.