How much of an effect on cell life would it be if a battery had a constant draw but was also constantly being charged? For example, running a computer directly off a Li-polymer battery pack which has the charger attached.
Li-polymer constant charge / constant draw
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MolaKule
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If the charger is working correctly, then the battery is being charged as the computer is operating. There should be no net battery discharge.
Well what I'm thinking is this - the power pack cuts power output completely whenever it switches from "charging" to "discharging" (i.e., whenever the cord is pulled). My laptop has no battery in it, so every time this happens when I haven't put it on standby first, it shuts off. The four cells in the battery pack output 16 V, my laptop takes 12 V, and the power pack manufacturer (also the manufacturer of the laptop) says the only way to use the pack is with 19 V output. What if I wired the +ve output of the cells directly to the output pin of the connector? The computer would run off the batteries and the power pack would recharge itself when it notices the batteries are getting drained. I would have to keep from completely discharging the cells, but with a 9-hour runtime I can handle that.
I would not charge a li-polymer battery with anything but the proper charger, which is not the power brick for the laptop. There are charging circuits inside the laptop.
I wouldn't be touching the charging circuit. What I want to modify is the output circuit. So when the power pack is in "discharge" state, the 19 V output line is severed and delivers no charge - the laptop will run directly off the four cells. In the "charging" state, 12 V from the laptop brick is used to charge the pack through its own charging circuit.
Are you trying to avoid the voltage drop between the 19V output of the external battery and the 12V requirement of the computer? The computer's power input circuit might be a switcher, and fairly efficient. Yes, it would be more energy efficient to connect the external pack's cells directly to the computer, like it's internal battery used to be, but that might be a bit of trouble to do.
You'd probably have to take apart the external pack, and wire its cells in place of where the regular batter pack cells go. It probably also has a temperature monitoring circuit that would have to be transplanted.
You'd probably have to take apart the external pack, and wire its cells in place of where the regular batter pack cells go. It probably also has a temperature monitoring circuit that would have to be transplanted.
No, I'm trying to avoid the cut in power whenever I remove or plug in the power brick to the external power pack. Without a battery in my laptop, this means it would still shut down due to a power outage or someone tripping over the brick. I'd like to make the switch instantaneous like how a laptop immediately switches to battery power when the plug is pulled, without shutting off first.
Is this correct? You have:
1. laptop computer with no internal battery
2. power supply for laptop
3. external Li polymer battery pack that plugs into the same hole as #2.
4. charger for #3
But for some strange reason #3 output shuts off whenever you unplug its charger?
1. laptop computer with no internal battery
2. power supply for laptop
3. external Li polymer battery pack that plugs into the same hole as #2.
4. charger for #3
But for some strange reason #3 output shuts off whenever you unplug its charger?
Yup, that's exactly right. The external power supply is an Electrovaya PowerPad 90, and the laptop is an Electrovaya Scribbler SC3000.
I've heard of that company before. How did you end up buying one of their laptops?
I tried running my celeron M based laptop on a 12V battery, and no go. Three 6V tractor batteries in series for 18V might work to keep it running for a few days.
Does the external pack shut off its output permanently when you plug in it's charger? Maybe the charger can only handle the load of recharging the pack, and nothing more, so they did this to protect it. I suppose you *could* connect the original laptop power supply through a blocking diode, and plug the p/s into the wall through a UPS.
Or get 18V of lead/acid storage, use the 19(?)V laptop p/s as a charger, and connect that battery through a diode to the computer. Fourteen nickel-m.h. cells in series might work with that p/s, without blowing up, if you work out a good circuit.
I tried running my celeron M based laptop on a 12V battery, and no go. Three 6V tractor batteries in series for 18V might work to keep it running for a few days.
Does the external pack shut off its output permanently when you plug in it's charger? Maybe the charger can only handle the load of recharging the pack, and nothing more, so they did this to protect it. I suppose you *could* connect the original laptop power supply through a blocking diode, and plug the p/s into the wall through a UPS.
Or get 18V of lead/acid storage, use the 19(?)V laptop p/s as a charger, and connect that battery through a diode to the computer. Fourteen nickel-m.h. cells in series might work with that p/s, without blowing up, if you work out a good circuit.
I got their laptop (tablet, actually) for the battery life. It comes with a 75 Wh battery which lasts around 9 hours at conservative power settings. After the original battery got used up, they kept being out of stock so I got a PowerPad external battery instead - same price for an extra 15 Wh.
The PowerPad output doesn't shut off permanently - it's just for one or two seconds. I think I hear a relay in there clicking when it switches over to the charging circuit.
The PowerPad output doesn't shut off permanently - it's just for one or two seconds. I think I hear a relay in there clicking when it switches over to the charging circuit.
ok, you might get away with a BIG capacitor to cover the temporary outage. But I'm not sure if the battery pack needs to have 0 volts on its output for any reason. You could wire the capacitor to the computer power plug through a diode that conducts when the capacitor is discharging, and a resistor to charge it back up slowly off the power pack/charger current. Maybe a giant capacitor could be wired directly across the power pad output, but I don't know if the circuit would like it.
Originally Posted By: oilyriser
I tried running my celeron M based laptop on a 12V battery, and no go. Three 6V tractor batteries in series for 18V might work to keep it running for a few days.
I have a 12V power adapter for my celeron M notebook. It steps 12V up to 18V. I paid about $20 (shipped) for it from an Ebay seller who had a lot of them for sale. It's intended for powering the notebook from a cigarette lighter but you could connect it to any 12V battery.
I just checked Ebay and there are a lot listed. For example see Item number: 110229120700 -- this is identical to the one I have.
I tried running my celeron M based laptop on a 12V battery, and no go. Three 6V tractor batteries in series for 18V might work to keep it running for a few days.
I have a 12V power adapter for my celeron M notebook. It steps 12V up to 18V. I paid about $20 (shipped) for it from an Ebay seller who had a lot of them for sale. It's intended for powering the notebook from a cigarette lighter but you could connect it to any 12V battery.
I just checked Ebay and there are a lot listed. For example see Item number: 110229120700 -- this is identical to the one I have.
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How big of a capacitor would I need? I don't work with electronics often so could you give me an idea of how big it is physically as well? The battery pack doesn't have a lot of spare room in the case - maximum would be maybe 2 cm x 2 cm x 2 cm.
you'd have to measure the power consumption of the system. then time for how long the power pack loses power. Test the system to see how low the voltage can go before it stops working, then maybe allow 1/3 of that drop. Use this data to calculate the capacitance, using the energy formula 1/2 CV^2. Maybe there's an ultracapacitor that would fit inside the old battery case, but it would have to be able to take the full voltage.
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