re-modding Serial-Parallel switch

[NickJuice]

Ok awhile ago i built a 5v-3.7v Nicostick(I know its a mess)...it was an overbuilt design but worked well in practice

Now when using the 5v regulator...the batteries are set in a Serial setup (7.4v regulated to 5v), this works great for the 5v setup....but when using it at 3.7v it only drains from ONE battery, this discharges the batteries at different rates and i end up having to keep an eye on that single battery more then the other one...

i'd LIKE to be able to setup the 3.7v as a parellel setup...but can't picture how this would work...any ideas based on the drawing above? Is it just a matter of jumping the other positive and negative terminals?

 

[mnealtx]

Add a third battery. Electrically isolate it from the others. Run a jumper from battery negative to the on/off switch, wire positive to the 3.7v side of the SPDT.

 

[opuscroakus]

Add a third battery. Electrically isolate it from the others. Run a jumper from battery negative to the on/off switch, wire positive to the 3.7v side of the SPDT.

Couldn't you do this?

 

[Guitarslinger]

That looks like it would work to me as well opus, but someone with more expertise may know better. Do you have 2 on/off switches in addition to the momentary switcH?? Just wondering- it looks that way.

 

[mnealtx]

Yes, running parallel batteries and using a booster chip is a better solution for the 5v.

 

[opuscroakus]

Yes, running parallel batteries and using a booster chip is a better solution for the 5v.

Knew that. Was wondering if I had the wiring correct for 5v and 3.7 from parallel batteries. Should be, but of course I left out the capacitors, again.

 

[mnealtx]

Ah... looks right at a quick glance, yes (minus the caps )

 

[j0ker]

So where would you add the caps? Can you add to your diagram?

Great info guys!


Thanks NickJuice, haven't thought of this.

 

[mnealtx]

You need to stack 22uf and 100uf caps and put them between input and gnd, and output and gnd. There's a thread about voltage regulators where it talks about it - look for Nuck's posts or search for 04050C.

 

[j0ker]

Thanx mnealtx...got ya! Just what I needed!

 

[firhill]

Courtesy of Nuck...

 

[j0ker]

Great! Thanks Nuck & firhill!

 

[supertrkre2812]

Now i'm confused.
i thought if you used the TI amplifier, and you wanted a 5v output that you didn't have to use the resistors or caps, that the board just defaulted to 5v.
Is that right?
I don't want to toast my board as soon as i install by batts.

Supertrkre2812

 

[mnealtx]

Without a set resistor, the board defaults to 5v. The capacitors are HIGHLY recommended because they reduce ripple that can trigger the protective IC in the batteries.