Adapting power output

[jujuteux]

hi there

i'm making a phone watercooler since mine can get up to 58° in various situations
so i made a simple system consisting of a water pump 3V 0.1A, 4 micro fans: 3V and 0.15A each, a 3.7v polymer battery wich holds 1800mAh
the thing is:
i'm dumb as F*ck when it comes to electricity and i do not know how to adapt the output voltage i'll be giving to my electronics so to say: setting that 3.7V output to a 3V
i think it can be a very simple thing to do, for sure, but i have no idea what it is
inb4: no i don't really wanna use resistors since they can eat a lot of power and i don't know how to use them

 

[kellys_eye]

The fans and pump will probably work ok at the slightly higher voltage of 3.7V over their rated 3V but if you want to be safe and sure then fit a diode (1N5407) in series with the battery output. It will drop somewhere between 0.6 and 0.7V across it, leaving 3V (near enough) to the fans etc.

 

[jujuteux]

The fans and pump will probably work ok at the slightly higher voltage of 3.7V over their rated 3V but if you want to be safe and sure then fit a diode (1N5407) in series with the battery output. It will drop somewhere between 0.6 and 0.7V across it, leaving 3V (near enough) to the fans etc.

but does it consume power?
i searched that diode and it says something about 3A and 800V, What? i odn't really understand

 

[Kabelsalat]

That is just the diodes ratings that means that under normal load situations, you probably within the diode limitations.

 

[kellys_eye]

The diode forward voltage drop multiplied by the current draw will reveal the power dissipated. So approximately 0.6 x ((4 x 0.15)+.1) = 0.42 (under 1/2 watt power loss). This will be the same as using a resistor (near enough) but the alternative would be to fit a buck converter (electronic supply converter) that would have, at best, an efficiency of 80% and add unnecessary complication.

The K.I.S.S principle applies (keep it simple, stupid) and the difference in power savings over cost and complication are hardly worth the effort.

 

[jujuteux]

The diode forward voltage drop multiplied by the current draw will reveal the power dissipated. So approximately 0.6 x ((4 x 0.15)+.1) = 0.42 (under 1/2 watt power loss). This will be the same as using a resistor (near enough) but the alternative would be to fit a buck converter (electronic supply converter) that would have, at best, an efficiency of 80% and add unnecessary complication.

The K.I.S.S principle applies (keep it simple, stupid) and the difference in power savings over cost and complication are hardly worth the effort.

ok, thanks!
i have one last concern: i use a 3.7v 500mA li-po charger module for this, does it mean it only charges batteries that have 500mAh or that charges all batteries at 500 mA/h?
here's the link for it:https://www.sparkfun.com/products/10217

 

[kellys_eye]

It'll charge all 3.7V lithiums but only at a certain charge-rate - in your case 500mA. Larger capacity batteries will (obviously) take longer to charge using that charger.

 

[73's de Edd]

Messr jujuteux . . . . .

Appeler un chat un chat . . . .do you think that those fans will even CARE about receiving an extra 0 .7 Volt ?
I know that the pump MOTOR, will just love it.
If that battery that you specify, is being a "pouch" type Li ion battery, a hard metal cased 18650 would be a much better and proven type choice.
(Unless there is being a physical size constraint.)
I might surmise that the last item shown in the "pixel" illustration would be the charger for the unit ?
500 ma would be taxing that specified cell quite hard . . .feel the heat . . . that is the absolute MAX that would subject my 18650 cell to. I settle for a cool 150 ma instead, and give it the required time. . . .it then rewards me with LONGEVITY.
If that phone is subjected to such a high ambient temperature, where do you live . . . . Nîmes ?


73's de Edd
.....

 

[jujuteux]

Messr jujuteux . . . . .

Appeler un chat un chat . . . .do you think that those fans will even CARE about receiving an extra 0 .7 Volt ?
I know that the pump MOTOR, will just love it.
If that battery that you specify, is being a "pouch" type Li ion battery, a hard metal cased 18650 would be a much better and proven type choice.
(Unless there is being a physical size constraint.)
I might surmise that the last item shown in the "pixel" illustration would be the charger for the unit ?
500 ma would be taxing that specified cell quite hard . . .feel the heat . . . that is the absolute MAX that would subject my 18650 cell to. I settle for a cool 150 ma instead, and give it the required time. . . .it then rewards me with LONGEVITY.
If that phone is subjected to such a high ambient temperature, where do you live . . . . Nîmes ?


73's de Edd
.....

hi
i'm not a pro around batteries and charging things buti think that 150mA is just ridiculously small
like my phone charges itself at 2048mA, so its 4000mA battery only needs two hours
yes i need a flat cell because i don't want my cooler to be more than 1.5cm thick
so it's a 1800mA cell, charging it at 150mA is just too slow for its use since the 3 fans and pump requires 2.3Wh
if i need 12 hours to refill a battery that only lasts less than 3 hours then it's not going to be anything near good, like how am i sensed to find 12 hours in my day?
i know about theses 18650 battery cells, i could MAYBE cut my promise short and sett hat max to 2cm but the thing is i find theses onlines offers just too fishy, a 4 pack 12000mAh 3.7v battery?! for 2.82€?! a 4 pack 5000 mAh 3.7v battery cell for 6.44€?!
the thing is i do not know whom are the scams and whom aren't, i just don't know what are the statistics for standards 18650 batteries and fancy 18650 batteries.
if you do know some offers that are legit ones(like if you already bought some) and have high capacities, i do not care for how much they are sold, i've already spend a good 70$ on that little prototype or 500$ if i count the printer for the case and RnD
btw i do not live in a hot place, i just have a BV8000, a fancy brick that is as tough as strong (like wHAT?! 6gigs and an octocore 2.2GHz?!) and that can get really hot while playing top graphics games at max settings

oh, and i also searched for lipo since they have wires, who on earth has 18650 battery holders

 

[Bluejets]

oh, and i also searched for lipo since they have wires, who on earth has 18650 battery holders

Ebay for one..................

https://www.ebay.com.au/itm/Battery...l1313.TR3.TRC1.A0.H0.X18650+battery+case.TRS0

 

[Bluejets]

These were used in a review I watched recently on radio control transmitter battery replacement.

I've ordered some to try so can't really say on quality etc. BUT it is usually fairly reliable when R/c reviewers use them, especially this bloke.

It was pointed out once before that when some of the 18650 sellers start claiming unbelievable capacities at low price then it is time to cut and run so that might be a bit of a guide. i.e. if it seems too good a deal etc........

https://www.ebay.com.au/itm/Trustfi...0+3.7V+battery&_from=R40&rt=nc&LH_TitleDesc=0

 

[kellys_eye]

OK, your phone gets hot..... but if it was a problem then the manufacturers would have addressed it else it is of 'poor design'. Is this heat a particular issue for 'you' or for the phones operation in general? Does it fail? Does it burst into flames?

If you are doing this to satisfy your own peculiarity for handling anything 'hot' then fair enough - assuming you can still hold and pocket the thing after the mods are fitted! If you are doing this as a potential after-market device you're going nowhere.

 

[jujuteux]

OK, your phone gets hot..... but if it was a problem then the manufacturers would have addressed it else it is of 'poor design'. Is this heat a particular issue for 'you' or for the phones operation in general? Does it fail? Does it burst into flames?

If you are doing this to satisfy your own peculiarity for handling anything 'hot' then fair enough - assuming you can still hold and pocket the thing after the mods are fitted! If you are doing this as a potential after-market device you're going nowhere.

well there is two reasons why i'm making it:
-the phone is hot and i don't like it when it's hot
-i'm in Engineering Studies, it's good for my resume if i show a personal project wich ends successful

ps: all the phones i had always reached something like 45-50 at times, same for the people around me so it's not bv8k only