Volts and Amps

[FunN4lo]

Buy Phantom 3 - 57W Battery Charger

This 57watt charger is what comes with the P3A... P3S... P3 4k

You are in the wrong forum. This is the P4P forum . We run on 100w chargers. I have forgot more about batt charging than most people will ever know. My major expertise resides in PB and AGM batts. While we run on LiPo, I have also been in RC longer, much longer, than Phantoms have been around. I have been mobile charging that whole time. While these batt mediums are vastly different in many ways, the chemical storage of energy follows the same basic principles. So the answer to the OPs question/scenario is still... aint gonna happen

Now if you want a fantastical mobile charging solution, on a shoe string budget, that works all day, everyday, charging 3 batts and the RC, in more safe conditions than most folks do at home CLICK HERE

 

[sar104]

You are in the wrong forum. This is the P4P forum . We run on 100w chargers. I have forgot more about batt charging than most people will ever know. My major expertise resides in PB and AGM batts. While we run on LiPo, I have also been in RC longer, much longer, than Phantoms have been around. I have been mobile charging that whole time. While these batt mediums are vastly different in many ways, the chemical storage of energy follows the same basic principles. So the answer to the OPs question/scenario is still... aint gonna happen

Now if you want a fantastical mobile charging solution, on a shoe string budget, that works all day, everyday, charging 3 batts and the RC, in more safe conditions than most folks do at home CLICK HERE

Fair point, although to address the original issue, you don't need any particular power (wattage) to charge any of these batteries. As long as the voltage is sufficient to drive current, then supplying a lower current will simply result in slower charging. A 50 W charger would charge a P4 battery just fine, but take approximately twice as long.

Nice truck charger though.

 

[FunN4lo]

Fair point, although to address the original issue, you don't need any particular power (wattage) to charge any of these batteries. As long as the voltage is sufficient to drive current, then supplying a lower current will simply result in slower charging. A 50 W charger would charge a P4 battery just fine, but take approximately twice as long.

Nice truck charger though.

When you are talking powered chargers, that is true. When you are charging battery to battery, the electricity seeks its own level, high to low, much like water between 2 buckets.

For instance, have you ever siphoned water? You can easily move water from one bucket to another with a hose and no power. The full bucket needs to be higher than the empty bucket. That works even if the hose goes up to get out of the full bucket. If the buckets are level, the full bucket will not empty. If the full bucket is lower, the water is going the other way

As an illustration, (a simple illustration, it is somewhat more complicated than this) the charging batt (full bucket) has to be higher than the low batt (empty bucket). In the case of charging batt to batt, the full bucket height that is required, is not a physical height, but the energy potential height.

Power bank chargers have vregs that act as a valve and prevent backflow. (when the empty bucket gets to the same level as the full bucket) But the vreg set level of the charging batt (full bucket) has to be higher than the need (flow) to charge the low batt (empty bucket) in the first place.

Volts, amps, and watts all figure into that "height", to get power to flow the way you want, and to get the charge that you need

 

[sar104]

When you are talking powered chargers, that is true. When you are charging battery to battery, the electricity seeks its own level, high to low, much like water between 2 buckets.

For instance, have you ever siphoned water? You can easily move water from one bucket to another with a hose and no power. The full bucket needs to be higher than the empty bucket. That works even if the hose goes up to get out of the full bucket. If the buckets are level, the full bucket will not empty. If the full bucket is lower, the water is going the other way

As an illustration, (a simple illustration, it is somewhat more complicated than this) the charging batt (full bucket) has to be higher than the low batt (empty bucket). In the case of charging batt to batt, the full bucket height that is required, is not a physical height, but the energy potential height.

Power bank chargers have vregs that act as a valve and prevent backflow. (when the empty bucket gets to the same level as the full bucket) But the vreg set level of the charging batt (full bucket) has to be higher than the need (flow) to charge the low batt (empty bucket) in the first place.

Volts, amps, and watts all figure into that "height", to get power to flow the way you want, and to get the charge that you need

I thought that we were talking about powered chargers.

Anyway, while your analogy is a commonly-used one, and applicable enough to visualize simple electrical concepts, the point I was making, in the terms of that analogy, is that volts, amps and watts (voltage, current and power) do not all figure into that "height"; in your water analogy, height is represented solely by voltage and that is all that is required for a charging current (or water) to flow. How much flows (total charge moved) depends on other factors, but whether it flows does not. As such, even for battery-to-battery charging, the instantaneous relative liquid level in the buckets is all that matters - the difference from powered charging simply being that the level in both buckets changes as the sink bucket fills (source bucket has finite volume), whereas for powered charging the source bucket (unlimited volume) remains at a constant level.

In the analogy, current is flow rate, determined by voltage (height) and a combination of pipe length and diameter (representing resistance but not as simple as Ohm's Law). Power, in the analogy, is related to the rate of change of potential energy of the water, but does not represent an equivalent limiting factor as it does in the electric case since, when an actual current source runs out of power, its voltage drops, whereas water levels to not vary with flow rate. If we were to be more rigorous in an incompressible fluid flow analogy, voltage is not really equivalent to height - it's equivalent to dynamic pressure derived from Bernoulli's principle plus drag.

 

[marios5]

No, not correct. 10,000 mah power bank supplies power at 5volts resulting into 50Whr energy

Whereas each battery is 5870mah at 15.2 v resulting into 89.2 Whr.

Hence battery pack doesn't have enough juice to charge phantom battery. There are 30,000 mah power packs available that with a D.C. Voltage booster may be enough to charge this battery.

Good day, I know this is a very old post. What will happen if I over charge the battery, say 19.1 volts or under charge it say 16.8 volts?

 

[marios5]

The main issue is whether the power bank can sustain its voltage at the required current level all the way through. @HighTechPauper pointed out "17.5 volts @ 5.7 amps is what the charger is rated" as the guzzoutta capacity of the charger. That is supported by the AC mains going in at up to 100W.

A power bank is being depleted and its own batteries are falling in voltage. If the power bank doesn't have a DC-DC converter to hold up the voltage with the current, then it can't charge the P4P battery completely.

Next, capacity. 10,000 mAh at what voltage? What you need is WH in excess of each P4P battery you want to charge as @alokbhargava points out in a round about way. Also factor in conversion inefficiencies.

10,000 mAh @ 5V = 50 WH. The P4P batt is 90 WH. So you'd need in excess of 2 of your 10 AH power banks to charge a single P4P battery (conversion inefficiencies need to be factored in).

Finally of course, how are you going to get your 5V supply up to 17.5 V? Can the power bank output enough current?

17.5V/5 = 3.5 more current so the power bank has to output over 20 A @ 5V into a DC-DC converter that outputs 17.5V (5.7A). (Over 20A because the DC-DC will have conversion inefficiencies).

I know this is an old post, but what will happen if I over or under charge the battery, say 19.1 volts or 16.8 volts?