Charging tablet in a car

[VanJ]

Hi,

I would like to charge two pipo (M6) tablets in my car. Instead of buying 2 chargers and a 12V socket splitter, I would like to build a charger with 2 outputs.
As far as I know the PiPo tablet charger provides 9V with 2,5A. Does anyone any experience with other (universal) charegers with pipo tablets?

[coolicool]

Hi,

I would like to charge two pipo (M6) tablets in my car. Instead of buying 2 chargers and a 12V socket splitter, I would like to build a charger with 2 outputs.
As far as I know the PiPo tablet charger provides 9V with 2,5A. Does anyone any experience with other (universal) charegers with pipo tablets?

it is hard to buy 9V 2.5A car charger, but if you want to buy,maybe i can help you to find it in Huaqiangbei,shenzhen,china.

[giouncino]

Hi,

I would like to charge two pipo (M6) tablets in my car. Instead of buying 2 chargers and a 12V socket splitter, I would like to build a charger with 2 outputs.
As far as I know the PiPo tablet charger provides 9V with 2,5A. Does anyone any experience with other (universal) charegers with pipo tablets?

You will probably need a charger with 9V and more than 2.5A to charge the tablets in parallel, but if you disconnect on of them before the other you risk to damage the battery of the remaining tablet for the overcurrect... I definitely suggest you to buy 2 x 9V chargers to avoid any risk of battery damage! You can easily find suitable charger for m6 on pipomall for 6$ or a little bit more. The car charger with 1,5A could be enough for one tablet. The 2,5A is the perfect one.

[Tybalt39]

.... risk to damage the battery of the remaining tablet for the overcurrect...

Is this a problem with Pipo tablets? I was under the impression devices only draw the amount of current required by their charging system (up to the maximum of the charger). For many years, I have charged various phones, accessories, and single-core tablets using 2.1A chargers. The phones especially like it, as they charge much faster than with the factory chargers.

I have problems charging when the current is too low to both run the tablet and charge it at the same time. My 2.1A chargers can't keep-up with my Pipo without powering-down.

Did I miss something regarding chargers, batteries, and current capacities?

[giouncino]

Li-ion battery can be charged faster giving higher current, this is good, but the battery life is reduced so much that it is not a good idea to use charger with higer Amps than the original.
I prefer a slow charge but a longer battery life!

Of course if you use a charger with lower Amps than the minimum required by the tablet to stay on you cannot keep the tablet on during charging!

I don't know which is the minimum required power to keep the M6 on during charging. But I think it's not far from the 2.5Amps of the stock charger, for the reason above...

[TriA]

giouncino, sorry but you aren't right here.
(I have education, corresponding to this topic)
Extra current capability of power supply can't do any damage to the tablet in any way.
Charge current is set by charge controller inside the tablet, not by power supply.
It is safe to use power supply of 2.5A and any higher amperage, but weaker supply isn't recommended.
What is critical about possible damage - is voltage - it should strictly correspond to one stated on the tablet. Say, 12V power supply will damage the tablet for sure.

So, VanJ, if you can find, order or make a 9V, 5+A DC power supply with two appropriate jacks (with proper polarity: positive inside, negative outside) - you can use it safely

[giouncino]

giouncino, sorry but you aren't right here.
(I have education, corresponding to this topic)
Extra current capability of power supply can't do any damage to the tablet in any way.
Charge current is set by charge controller inside the tablet, not by power supply.
It is safe to use power supply of 2.5A and any higher amperage, but weaker supply isn't recommended.
What is critical about possible damage - is voltage - it should strictly correspond to one stated on the tablet. Say, 12V power supply will damage the tablet for sure.

So, VanJ, if you can find, order or make a 9V, 5+A DC power supply with two appropriate jacks (with proper polarity: positive inside, negative outside) - you can use it safely

You are definiterly right about the voltage: low voltage Power supply are under threshold and cannot charge the tablet at all, higher than 9V power supply will damage the tablet for sure!

But are you sure that the tablet is able to control the amount of current necessary to charge the tablet?
I'm not sure that our cheap tablets can control also the current....
This is why I wrote that before!

[TriA]

But are you sure that the tablet is able to control the amount of current necessary to charge the tablet?
I'm not sure that our cheap tablets can control also the current....

Current control circuit is mandatory for lithium batteries, because it should stop charging when battery is fully charged (4.2V). Without charge controller the battery will continue to charge forever (because of huge voltage difference: 9V supply vs 4.2V battery) and eventually burn up! And, charge controller is simple and cheap IC, so not a problem even for cheapest devices.
(by the way, lithium batteries are very sensitive to level of max voltage, and will not last over about 100 cycles if 4.2V is exceeded even slightly. Moreover, if battery is not charged to the max every time, its life expectancy will grow in 1.5...2 times, so personally I recommend not to charge lithium batteries over 90% in cases when this isn't critical)
Ah, devices based on Ni-Cd or lead acid batteries may not have the charge controller, because these battery types are not so sensitive. But size and weight of such batteries are not fit into tablets in any way

[giouncino]

Current control circuit is mandatory for lithium batteries, because it should stop charging when battery is fully charged (4.2V). Without charge controller the battery will continue to charge forever (because of huge voltage difference: 9V supply vs 4.2V battery) and eventually burn up! And, charge controller is simple and cheap IC, so not a problem even for cheapest devices.
(by the way, lithium batteries are very sensitive to level of max voltage, and will not last over about 100 cycles if 4.2V is exceeded even slightly. Moreover, if battery is not charged to the max every time, its life expectancy will grow in 1.5...2 times, so personally I recommend not to charge lithium batteries over 90% in cases when this isn't critical)
Ah, devices based on Ni-Cd or lead acid batteries may not have the charge controller, because these battery types are not so sensitive. But size and weight of such batteries are not fit into tablets in any way

Good to know, thank you!
But pay attention M6 battery are rated at 7.4V and the charger is 9V

[TriA]

ah, that means fully charged voltage should be 2*4.2 = 8.4V

[Tybalt39]

If I'm not mistaken, battery charging is accomplished by "forcing" a somewhat higher voltage into the battery than the battery supplies. This reverses the charge/discharge condition of the battery. This also explains why a 4.2V LIoN battery uses a 5v charger and an 8.4v tablet uses a 9v charger.

Again, these recollections are decades old, I could be mistaken (too lazy to search).

[TriA]

nominal voltage of one-cell lithium batteries is 3.6-3.7V, 4.2 is maximum. Some extra voltage (up to 4.7-5.2V) is needed for charger circuitry to mantain proper charging current, taking into account internal resistance of battery and losses in wires and circuitry itself.

[Tybalt39]

Thank you for the clarification!