Charging while playing - Howto

HazmatB · Post by **HazmatB** » Wed Aug 06, 2008 11:49 am

Hey guys,

If and when I ever get the time to actually make a portable, I really want it to not be a hack. That is to say, I don't want to have 50,000 switches, one for powering from the wall, one for charging, one for playing from batteries, and so on. However, I am not sure how to set up the circuit.

Essentially what I am asking, is if some of the elec-engineers around here could show a general circuit that would run to the control circuit for a li-ion, and to the power source for the portable, and fully charge the batteries while possible, and then when charged would power the portable.

This may not be possible either, and if I haven't made myself clear, please let me know.

kasar · Post by **kasar** » Thu Aug 07, 2008 2:22 pm

my project only have one switch.

when I plug the charger it go to the li-ons PCB , you also can play meanwhile playing, when the li-ons are fully charged it just stop drain power.

IÂ´m using a charger from a broken laptop 3,15 A 20v I installed a 12v regulator board for the system (tv + gc) the voltage for batteries is unregulated (them need more than 12 for charge. it just do fine his job.

the only weird circuit IÂ´m using is the one for protect li-ons batteries, so I think you dont need others.

you also need a higher power suply (more Amperes- for charge batteries and play at same time)

it depends the system you have, the batteries ...... you should get the correct power suply for charge/play the system

I hope this help

Turbo Tax 1.0 · Post by **Turbo Tax 1.0** » Fri Aug 08, 2008 6:41 am

just buy a smart charger and a protection circuit and you can charge while playing

It is the setup I use for most of my portables

HazmatB · Post by **HazmatB** » Fri Aug 08, 2008 11:27 am

Thanks guys!

Rekarp · Post by **Rekarp** » Fri Aug 08, 2008 12:09 pm

According to the spec sheets of most protection circuits I have seen it warns against charging and discharging Lithium batteries at the same time. Though I have played my SNES V1 (which has lithium) and charged it at the same time with no ill effects.

HazmatB · Post by **HazmatB** » Fri Aug 08, 2008 12:38 pm

Rekarp wrote:According to the spec sheets of most protection circuits I have seen it warns against charging and discharging Lithium batteries at the same time. Though I have played my SNES V1 (which has lithium) and charged it at the same time with no ill effects.

I have read this before, so I was wondering if I should build a circuit that charges the battery and uses the mains power to power the portable. (If both are needing power...)

Website · Post by **Life of Brian** » Fri Aug 08, 2008 2:38 pm

Turbo Tax 1.0 wrote:just buy a smart charger and a protection circuit and you can charge while playing

It is the setup I use for most of my portables

Using the stuff from batteryspace? How often have you done this? And if it works just fine, then cool! That instantly adds another feature to the ZN-40 SNES portable I just finished! I have more skills than I realized

But, like Rekarp said - I've read warnings against that so I dunno...

HazmatB · Post by **HazmatB** » Sat Aug 09, 2008 7:20 pm

Sorry to bump, but just wondering if I could get a definitive answer on how much damage this does to the battery. I can only seem to find FUD or confusion on this subject.

GonzoMPM-1 · Post by **GonzoMPM-1** » Sun Aug 10, 2008 3:50 pm

HazmatB wrote:Sorry to bump, but just wondering if I could get a definitive answer on how much damage this does to the battery. I can only seem to find FUD or confusion on this subject.

The battery manufacturers say not to.

So you shouldn't, in my view.

But you can get around it by the wonder of semiconductors.

You can wire up the device so that when a + voltage from the charger is present, the battery --> game connection is cut off and the voltage from the charger is the only thing that is presented to the drain represented by the game boards and screen.

I'd have to think about it more, but I think you'd use a P type FET to shut "off" the connection from the batteries to the game when a high signal is introduced at the gate from the + pole of the charger through a diode, and then two legs from the charger (one to battery + and one to your game regulator/boards) each isolated from each other via FET based synchronous rectifier configurations (to get over the problem with forward voltage drop that would result from just using pure diodes). This is what takes place on some level in a laptop when you plug it in.

The problem, as I see it, is that most LIPOLY set ups I have seen charge the cells on a per cell basis, so the charging voltage will only be 4.25 volts anyway. and wired to the cells in your array parallel to each of them.

For all the work involved, I don't think its worth it. I'd think a switch with a "charge only" mode would be best.

If you set up a good battery set up, you should be getting a couple/few hours of battery playing time, and then just let it rest while it charges.

If you must play with it plugged in, simply add a second jack with an old fashioned AC adaptor. And a switch that completely separates both ground and + of the batteries from the rest of the system when charging.

ShockSlayer · Post by **ShockSlayer** » Sun Aug 10, 2008 4:18 pm

http://forums.benheck.com/viewtopic.php ... sc&start=0

Probably what I would tell you.

SS

HazmatB · Post by **HazmatB** » Sun Aug 10, 2008 7:51 pm

GonzoMPM-1 wrote: You can wire up the device so that when a + voltage from the charger is present, the battery --> game connection is cut off and the voltage from the charger is the only thing that is presented to the drain represented by the game boards and screen.

Isn't that exactly what a transistor does? Could I wire something like this?

GonzoMPM-1 · Post by **GonzoMPM-1** » Sun Aug 10, 2008 8:10 pm

HazmatB wrote:
GonzoMPM-1 wrote: You can wire up the device so that when a + voltage from the charger is present, the battery --> game connection is cut off and the voltage from the charger is the only thing that is presented to the drain represented by the game boards and screen.
Isn't that exactly what a transistor does? Could I wire something like this?

Well, your drawing won't do it, but lets get first things first:

How many cells are you using, and does your set up charge the batteries in series or in parallel using only single cell voltage. That's going to be the main issue here.

HazmatB · Post by **HazmatB** » Sun Aug 10, 2008 8:53 pm

I realized that my drawing won't work, I'm re factoring it right now, doing some research.

GonzoMPM-1 wrote:Well, your drawing won't do it, but lets get first things first:

How many cells are you using, and does your set up charge the batteries in series or in parallel using only single cell voltage. That's going to be the main issue here.

as far as this goes, I would rather not get into the details. All of that stuff is implementation specific, and a general solution is what I am looking for. Suffice it to say that the set up is essentially:

1. A DC line (lets say 7V).
2. A set of lithium ion batteries which are charged and balanced using a protection circuit (Just to make everything nice let's have those output ~7V at full charge).
3. A console which takes a single DC 7V input.

What we want:
If the DC line is not present:
- If the console is on:
- The batteries power the console.
If the DC line is present:
- If the console is on:
- The DC line powers the console, and the protection circuit (which only draws when needed)
- If the console is off:
- The DC line powers the protection circuit.

It shouldn't really matter what the protection circuit is protecting should it?

Edit: Hmm, I think this might be what I need.

timmeh87 · Post by **timmeh87** » Mon Aug 11, 2008 10:08 am

Diagram is still a bit cryptic...

Are those NPN or PNP? Do you know the difference?

Also, use MOSFETS, as those old-school BJT transistors have a small current going through them at all times, your batteries will drain faster when it is off.

Also why the diode?

HazmatB · Post by **HazmatB** » Mon Aug 11, 2008 12:23 pm

Sorry about it being a bit cryptic.

The 'diode' is actually meant to be a NOT gate.

I did that drawing on some very preliminary research, but would now do it differently. The upper of the 2 transistors would be a PNP transistor, and the NOT gate would then be unnecessary. The lower of the 2 transistors would be NPN.

As I understand it MOSFETS also draw current all the time, but really the amount drawn would be near negligible. I could solve this problem with removable batteries. Also, I didn't realize that the symbol I used would carry the connotation that it was not a MOSFETS type.

Update: