Charging circuit for a 7.4V LiPro

Hi. I recently ordered a 7.5V walwart and a 7.4V LiPro battery and a friend of mine said that I can charge the lipro with a charging circuit but I will need a board to handle that.

I'd like to be able to power my device with the walwart when it's plugged in and/or charge the battery. When it's unplugged the battery should be the primary power source.

Can you recommend a board that will do what I need?

Note: the battery has a traxxas connector, and I am about to order a female plug for it that i'd like to hook up to the board for powering my device/charging the battery.

That's a two cell battery, and there should be a three-wire connector for charging (LiPoly batteries require balanced charging). You'll find lots of LiPo chargers for the RC market are available, just make sure you get one that handles 2S (2 in series) battery pack.

Always treat LiPo batteries carefully and look up the correct procedure for charging and disposal. Never charge them unattended.

DO NOT CHARGE A LIPO (NOT LIPRO) , (it's short for Lithium Polymer ) WITH A WALWART ! ARE YOU CRAZY ? Lipo batteries burst into flames when they are over charged and like the previous post said it is a TWO cell battery. That means that the maximum voltage it should be charged to is about 8V. Also , it should only be charged with a LIPO charger. Thousands of cars and houses have been burned down by people doing what you're talking about doing and then walking away and forgeting it's plugged in and eventually the battery gets so hot it explodes in a fireball. Unless you can plug it in outside on a cement patio away from anything flamable don't do it . Get a meter and measure the output voltage of the walwart.

raschemmel: DO NOT CHARGE A LIPO (NOT LIPRO) , (it's short for Lithium Polymer ) WITH A WALWART ! ARE YOU CRAZY ? Lipo batteries burst into flames when they are over charged and like the previous post said it is a TWO cell battery. That means that the maximum voltage it should be charged to is about 8V. Also , it should only be charged with a LIPO charger. Thousands of cars and houses have been burned down by people doing what you're talking about doing and then walking away and forgeting it's plugged in and eventually the battery gets so hot it explodes in a fireball. Unless you can plug it in outside on a cement patio away from anything flamable don't do it . Get a meter and measure the output voltage of the walwart.

So there's no circuit board that can just disconnect the power when the battery is full? If that's true that is ridiculous.

I wanted to integrate the battery into something I am designing so the user could just plug the walwart into the device and charge it without taking out the battery. I am looking for a rechargeable battery with lots of amp hours that is also small, that can deliver 5-9v (doesn't matter how many as long as it's in that range) at 1.2amps. I need something that will last a long time and I can attach to a walwart for charging.

Listen to what I am saying. Lipo batteries are a special technology. Everything Lipo related is governed by strict practices that cannot be deviated from. Everyone who know's anything about Lipo batteries or who uses them or who sells them or in any way comes in contact with them is aware that they can only be charged by a special kind of charger that is certified for use with Lipo batteries. Discussing whether or not you can use some other kind of charger is foolish. These batteries are dangerous and should only be charged with a Lipo Charger which is specifically designed to safely charge these batteries. There is nothing ridiculous about it. If you want to use the word "ridiculous in the same sentence with the word Lipo , then you can say that the internal resistance of these batteries is so low that the amount of current you pull off a 3 cell 2200mAh Lipo battery is RIDICULOUS ! TRY 35 to 50A ! http://www.hobbyking.com/hobbyking/store/__11911__Turnigy_nano_tech_2200mah_3S_25_50C_Lipo_Pack.html

The above battery can discharge at the rate of 25A CONTINUOUS or 50A for a 10 second burst ! That's RIDICULOUS ! If you charge that battery and connect the leads to a switch and then flip that switch and short the leads, that battery will burst into flames. You can say that's ridiculous but you better say it with respect.

Listen to raschemmel. He knows what he is talking about.

LiPo batteries were designed for rc model airplanes and cars. They are designed for high power output and light weight. They can only be charged with chargers that are designed for that battery type. There are youtube videos of them burning from being overcharged on purpose to show the danger associated with careless use of these batteries.

If you don't believe either of us, hook up your wall wart to it and put it under your bed. Darwin will take care of the rest. Send your kids to Grandma's house first.

Sleep tight.

John

If you want any respect for your opinion, you should probably learn to spell the word RIDICULOUS.

Otherwise, your opinions will attract RIDICULE and you will LOSE respect.

If you want any respect for your opinion, you should probably learn to spell the word RIDICULOUS.

Thanks for the heads-up on that Michinyon. Usually when you're trying to save someones life , home, and family, you're not thinking about spelling errors. but I appreciate you pointing that out. I went back and corrected my spelling. Hopefully the OP is still alive to read it .....

raschemmel, I can't believe you misspelled a word. And to think that I was considering counting you as a friend. Well, you can just forget about that. I don't want to hear from you again until you have completed a remedial spelling course and sent me a certificate to prove your competence in that area. I don't care how much you know about the subject at hand.

Shame, shame, shame John

The original poster asked an innocent question, I answered it explaining the safety issues. I don't see why there was any need to shout.

DO NOT CHARGE A LIPO (NOT LIPRO) , (it's short for Lithium Polymer ) WITH A WALWART ! ARE YOU CRAZY ?

Notice how I stopped in the middle of the shout and lowered my voice just long enough to explain the abbreviation ? Also , I stopped shouting long enough to finish the paragraph:

Lipo batteries burst into flames when they are over charged and like the previous post said it is a TWO cell battery. That means that the maximum voltage it should be charged to is about 8V. Also , it should only be charged with a LIPO charger. Thousands of cars and houses have been burned down by people doing what you're talking about doing and then walking away and forgeting it's plugged in and eventually the battery gets so hot it explodes in a fireball. Unless you can plug it in outside on a cement patio away from anything flamable don't do it . Get a meter and measure the output voltage of the walwart.

I'll shout any day if I can save someone's life, home & family by emphasizing the danger of something. I'd rather be thought rude than let someone get away with unplanned suicide.

see following link if you doubt the danger: http://www.amain.com/team/2012/02/the-dangers-of-charging-lipo-batteries/

duncan916:
So there’s no circuit board that can just disconnect the power when the battery is full? If that’s true that is ridiculous.

http://www.all-battery.com/protectivepcbsforli-ionandli-polymerbatterypacks.aspx

You haven’t described your project at all but it may have been a better idea to start with a charge pack designed for use with cell phones.

Chagrin:

duncan916: So there's no circuit board that can just disconnect the power when the battery is full? If that's true that is ridiculous.

http://www.all-battery.com/protectivepcbsforli-ionandli-polymerbatterypacks.aspx

You haven't described your project at all but it may have been a better idea to start with a charge pack designed for use with cell phones.

Thanks, that's just what I'm looking for, everyone has been very helpful. Now I just need to find a LiIon battery pack that's 7.4v and can supply 1.2A and will last for 8-12 hours. I may not need that much continuously but it's what I am trying to find at the moment. I am building an automated camera panner that will need to run up to 8+ hours on one charge.

I may be using a worm gear which would let me turn off the stepper motor between turns, but that is a maybe.

I will probably end up going with a 5V 10000 mAh lithium Ion battery, because 7.4V 20000 mAh batteries are so expensive.

I'd like to spend $20-30 at most. Suggestions? Needs to supply 1.2A

Do you have an old battery pack from a laptop? If you are handy, you can cut it open and it may have several 3.7v LiIon batteries in it. Usually there is one bad one and the rest are good. They will usually be of the 18650 4000mAh 3.7V Rechargeable Li-ion Battery style.

http://www.ebay.com/itm/UltraFire-18650-4000mAh-3-7V-Rechargeable-Li-ion-Battery-for-Torch-Flashlight-TR-/171225202575?pt=LH_DefaultDomain_0&hash=item27ddd13f8f

http://www.ebay.com/itm/171259114562?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

When ordering on ebay, pay particular attention to the Estimated Delivery date. Always assume the later date of the range and you will seldom be disappointed.

When fully charged, they will read 4.1 volts. 3 in series will give you near abouts 12v. 4 Amp-hours is a respectable amount of juice.

John