LiPO protection/ Charging module  - Page 1
Forum section: electronics / projects

author: SPRX
author_rank: Regular Contributor
timestamp: February 25, 2014, 04:13:54 am
content: I was wondering how reliable and safer to use this LiPO Protection Circuit Module to use with LiPO battery on a hand held test equipment. ( Battery is 3.7V 2200mAh 20C Lipoly, and my board runs at 3.3v and draws about 170mA)www.ebay.com/itm/10Pcs-Protection-Circuit-Module-PCM-PCB-for-3-7V-Li-Po-Li-ion-Battery-1S-3-15mm-/221214647149?pt=LH_DefaultDomain_0&hash=item33816ba36d#ht_1755wt_824I am developing a hand held test equipment, and suppose to use LiPO battery to power the equipment, and hoping to distribute few of those units in the field for testing.After serching on the net i found this on e-bay, and ordered few of those to see how they works (Spec matches the need). But not sure how reliable they are, when handling the LiPO on a hand held equipment safely.What you guys are using in general when using LiPO on a situation like this.

author: I_may_be_drunk_right_now
author_rank: Contributor
timestamp: February 25, 2014, 06:10:24 am
content: Are you buying cells without the protection already in it? Any LiPO that's wrapped in heat shrink already has one. You really shouldn't play with the bare pouches.(And do you expect it to work at -20C? C being Celsius, not some kind of discharge rating. It's winter here, and a "field" is really at -20C right now.)You have a battery pack designed to discharge about 40 amps for RC toy applications, why did you pick that for a 170mA load?You'd be happier with a simple low discharge LiFePo.A 20C LiPO could potentially cause burns and fires if your handheld device malfunctions. The battery will happily discharge dozens of amps before its protection circuit kicks in.A 20C LiPO, IMO, is meant to be discharged quickly and really won't "like" being stored at random voltages. If it's a handheld device, will it come with a battery management system?It just sounds like you're using a small nuclear bomb to power a candle, but trying to fit a large cement shell over it.

author: sleemanj
author_rank: Super Contributor
timestamp: February 25, 2014, 06:26:15 am
content: You're drawing sweet-f-a current, so what about using an already protected 18650 cell (or two) instead of your raw lipo.The metal shell of the 18650 will give some extra physical protection (consider than handheld tools will be dropped, stood on, potentially driven over....), are easier for Joe Bloggs to handle (if you want to be able to swap batteries), and you can get them with protection circuits built in (a small protection circuit PCB Is usually heat-shrunk on top of the negative terminal, makes the battery a fraction longer)).You can also get 18650 holders with the protection circuit in the holder, made for taking unprotected 18650's, but I'd recommend using protected batteries rather than protected holders.Whatever the case, you should of course properly test your protection, don't just rely on what the chinese seller says, make sure it works.

author: amyk
author_rank: Super Contributor
timestamp: February 25, 2014, 10:37:43 am
content: Seconding the 18650 recommendation.High-rate lipos also have high self-discharge and short life, because that's what they were optimised to do - fast charges and fast discharges, not longevity.

author: mcinque
author_rank: Unknown
timestamp: February 25, 2014, 12:14:49 pm
content: Quote from: I_may_be_drunk_right_now on February 25, 2014, 06:10:24 amNot any: in my airsoft and RC hobbies I've encountered always LiPo batteries without any kind of protection circuit.I'm talking not only about cheap chinese models, but also brands like Robbe and Hacker: I've dismantled many of them founding nothing else than cables.Any kind of protection circuit will limit the current that the battery can provide and therefore his performance would be terrible (expecially in RC 3D heli where you require the maximum current possible).

author: sacherjj
author_rank: Frequent Contributor
timestamp: February 25, 2014, 12:22:26 pm
content: Quote from: mcinque on February 25, 2014, 12:14:49 pmIf the batteries don't have SOME type of discharge protection, they will cease to be rechargeable if you push them too far. Lithium cells don't come back from too far of a discharge. For RC, this may be in the receiver/motor controller, but there is some point where voltage is low enough that it won't let power flow.

author: mcinque
author_rank: Unknown
timestamp: February 25, 2014, 12:42:56 pm
content: Quote from: sacherjj on February 25, 2014, 12:22:26 pmExactly. Afaik and in my experience, any LiPo (RC, Airsoft or any without protection circuit) will die if pushed below 3.3V per cell.In Airsoft the most popular protection circuit are "your ears": during the game, as soon you hear a lowering in rate of fire, you must stop playing and change the battery, because its voltage is dropping too much.Someone use an external buzzer circuitry that warns you when the voltage drop below 3.4V per cell, but it doesn't limit the discharging.The point is that the only LiPo batteries with a protection circuit I found (polyfuse or some active circuit) are those coming from cellphones and laptops. Surely nothing that must manage peaks of 40 or 50A.

author: SPRX
author_rank: Regular Contributor
timestamp: February 27, 2014, 12:32:03 pm
content: Thank you for advices, and I am convinced, and decided to use 18650 cells specially because of the safety.