Is this lithium-polymer battery pack DOA? - Page 1
Forum section: electronics / beginners

author: derGoldstein
author_rank: Regular Contributor
timestamp: August 16, 2017, 10:26:24 am
content: I ordered a few lipo battery packs from hobbyking. They all have a sticker on them saying "shipped at 30% charge, return to storage charge asap". Luckily I remembered to check the cell voltages on all of the packs and they were at around 3.65V on average (I mean the individual cells). I charged them to full charge one by one, until I reached a battery pack with these voltages (image attached).If the photo is not clear, the values are: 1.86V, 1.04V, 1.54V, and 3.75V. I checked them with a multimeter as well to verify, and those are indeed the voltages.As I understand it, a cell that goes under 2V should be discarded even if it was only left that way for a few days. The shipping of the batteries took about 8 or 9 days, so it's been sitting at those voltages for over a week.What should I do at this point? My first instinct is to immediately connect the battery pack to a charger and charge it very slowly until they reach ~3.7V, and then charge them normally all the way up. But considering the voltages the cells are at, I'm wondering if that's even safe... Should I just leave it alone and request a refund, or is this salvageable?

author: Rerouter
author_rank: Super Contributor
timestamp: August 16, 2017, 10:41:46 am
content: If they have been sitting at sub 2V for more than a day, they are likley toast, trying to charge them will likely result in the cells failing shorted. With only 1V on the cell it wont be explosive if charged at less than 0.1C, but i am predicing the outcome will not be worthwhile for youI am confused how you charging them led to them being at this low voltage? I am going to assume you over discharged it in a device with no cell monitoring,In general if you over discharge a pack, if you can start it on a 0.1C charge within the hour it will come good, after about 8 hours it will have a fair amount of capacity loss (more than 10%), and after a day its likely to fail shorted if you try and bring it back up to full voltageThis is specific to lipo, liion seems to come back from the dead much better than lipo.

author: Zero999
author_rank: Super Contributor
timestamp: August 16, 2017, 10:55:22 am
content: Quote from: Rerouter on August 16, 2017, 10:41:46 amI thought that at first but re-read the post again and that wasn't the case. The original poster purchased a few Li-ion packs and measured the cell voltages, to verify they're were OK, before charging them. At least one of the battery packs failed the cell voltage check and the question was whether or not it's worth trying to revive it?I agree, it's not worth attempting to recharge a dead pack, especially in this case, as it was the seller's fault. Return the back pack and ask for a refund.

author: derGoldstein
author_rank: Regular Contributor
timestamp: August 16, 2017, 11:23:20 am
content: Quote from: Hero999 on August 16, 2017, 10:55:22 amYeah, I didn't touch this one yet at all, just checked the voltages. They all had a sticker on them saying "shipped at 30% charge, return to storage charge asap", so maybe they over-discharged them before shipping. I guess I'll find out how hobbyking handles DOA packs...

author: Rerouter
author_rank: Super Contributor
timestamp: August 16, 2017, 11:28:38 am
content: They dont actually charge them or discharge them before shipping,When a lipo cell is created from the factory it will have about 30% charge floating on it, they do this to maximise shipping times,There is 0 chance hobbyking would charge / discharge test them prior to shippingWhat you are seeing is a failed pack, in other words 3 of the cells are leaky (cells 1-3), The ones in the past i have seen was cells 1-2 leaky, I partly suspect they are over heating the cells on 1 side when they are shrinking the labeling.

author: stmdude
author_rank: Frequent Contributor
timestamp: August 16, 2017, 11:34:05 am
content: Quote from: Rerouter on August 16, 2017, 11:28:38 amFun, off-topic, fact. Whilst hobby batteries aren't charged before shipping, we used to (and still do) charge the batteries in cellphones to 80% (or, more accurately, the CC/CV switch point) to maximize the shelf-life of the products (aka, the time they can be stored on a shelf before they're sold).80% was determined to be the sweetspot, as any more charge would negatively impact the capacity of the battery if they spent too long in that state (don't store your lithiums fully charged kids), and any less would decrease the shelf-life.

author: sleemanj
author_rank: Super Contributor
timestamp: August 16, 2017, 11:35:58 am
content: > I charged them to full charge one by one, until I reached a battery pack with these voltages (image attached).What do you mean? You charged the cells individually assuming through the balance lead one by one to full charge? And then after that you checked the voltages and 3 of the cells had lost their charge? If they have lost that through self discharge, then yes they are DOA. But if you have been charging them like this, it doesn't seem impossible that you flubbed up connections somehow and accidentally discharged some cells while charging others.Bigclive did some research on overdischarged cells recentlywhile a high current pouch cell is a slightly different thing, charged and tested safely and properly there is no reason to believe that cells that happened to arrive at your door with a very low voltage are rubbish.For what it's worth, I just salvaged some 18650's from out of a laptop pack that I found out in the shed and had probably been there for a few years, 1.7v when I took them out, charged, and discharge tested to 2.1Ah.~~~ Edit ~~~QuoteAh ok that makes more sense then. I would agree that because the cells are so vastly mismatched that there may be something fishy with those low cells beyond just having been shipped out at a low voltage.

author: Rerouter
author_rank: Super Contributor
timestamp: August 16, 2017, 11:40:33 am
content: Please don't mix chemistries, li-ion can be recovered from 1V after 6 months depending on the additives, (cobolt varients are more immune to the effect),18650 cells are down to such a science that good long life and hard to kill cells can be pumped out for nothing (dell doesn't want there laptop batteries dead after sitting a year at 0% charge (i know not 0V)But hobby li-po is cost cut to the point where any prolonged over discharge has them dead.

author: Neilm
author_rank: Super Contributor
timestamp: August 16, 2017, 07:12:21 pm
content: Quote from: stmdude on August 16, 2017, 11:34:05 amI thought that the shipping regulations had changed to say that batteries had to be shipped at no more than 30%. Or does this only apply to spare batteries?

author: stmdude
author_rank: Frequent Contributor
timestamp: August 16, 2017, 07:35:23 pm
content: Quote from: Neilm on August 16, 2017, 07:12:21 pmShipping wasn't really my specialty, but I know that the ODM I worked for still do it. I'm _guessing_ that rule applies when you ship just batteries (i.e, a much higher energy-density for the pallet).

author: amyk
author_rank: Super Contributor
timestamp: August 17, 2017, 02:14:46 am
content: Quote from: Rerouter on August 16, 2017, 11:40:33 amThis is a misconception. The only difference between "li-po" and "li-ion" is the packaging. The chemistry (cobalt, manganese, etc.) can be the same. What you mention about additives makes sense, however.

author: Audioguru
author_rank: Super Contributor
timestamp: August 18, 2017, 12:59:51 am
content: On the hobby forums, most people say that Hobby King sells cheap Chinese junk. I have some curves of Li-Po batteries discharging and Hobby King new Turnigy batteries are dead in a few second while all the other ones with similar ratings last for minutes.

author: Beamin
author_rank: Super Contributor
timestamp: August 18, 2017, 06:08:30 am
content: I thought when they built the cells they were at 30% charged as I don't see Chinese factories actually making the effort and time to put them on chargers. Its my understanding that lipo cells operate between 30% and 80% of 0v and a full charge. When you battery is "dead" its at 30% and the device or battery circuit cuts off. When it fully charged its at 80% of what it can really hold. Above or below these values the cells tend to explode burn. Maybe only 1 in 1000 will burst at 90% charge but when you are making 1000's of unit you don't take that chance as every pallet of batteries would catch on fire. I imagine they sit around for weeks or months with just the charge that assembling them gives them. It takes along time for a battery to get from some rural Chinese farm house/battery factory to the ship,then to the US, to the wholesaler, to the retailer, then to the customers battery charger.

author: Beamin
author_rank: Super Contributor
timestamp: August 18, 2017, 06:40:26 am
content: Here is the chemistry: The lithium in the electrolyte is lithium salts; LiClO4 Lithium perchlorate, LiPF6 Lithium phosphohexaflouride, LiBF4 Lithium borotetraflouride, in ether (the solvent). All of these form the electrolyte. The anode is carbon (graphite), and lithium cobalt oxide (LiCoO2) is the cathode.The lithium in the electrolyte turns into a Li+1 cation and an electron; then it migrates to the anode where it meets up electrons flowing out of your circuit. The voltage potential of the Li+ ion and the electron is 3.6 volts; 1.8 volts on each terminal.

author: derGoldstein
author_rank: Regular Contributor
timestamp: August 18, 2017, 10:10:17 am
content: Quote from: Beamin on August 18, 2017, 06:08:30 amThis brings up a related question -- is the "store lithium-ion batteries at 3.75V" a myth?There's this article on battery university:http://batteryuniversity.com/learn/article/how_to_store_batteriesBut they're been proven an unreliable source (they don't properly check references).If you get one of the typical "4 button balance chargers", many of them have an option to "store charge", which, depending on the charge state of the connected battery, will either charge or discharge in order to get each cell to around3.75V. (EDIT: I just tested my Turnigy Accucell-8150, and the "storage voltage", by default, is around ~3.83V-per-cell)However, power-tool lithium-ion packs are stored at full charge, even when they're just sitting on the store shelf. I think I read that phones/tablets are stored at 4V-per-cell, but I can't find a reference for that anywhere.For long-term storage, in what charge state do you leave lithium-ion batteries, and is there a difference here between the cylindrical 18650 type of cells and the flat lithium-"polymer" (most of which aren't polymeric) versions?

author: amyk
author_rank: Super Contributor
timestamp: August 19, 2017, 12:14:31 am
content: Here is a very good thread about lion chemistry and its characteristics:https://www.eevblog.com/forum/projects/diagnosing-lithium-cells/(The posts by Siwastaja are very much worth reading.)