Need help charging a battery. - Page 1
Forum section: electronics / beginners

author: skysurf76
author_rank: Regular Contributor
timestamp: June 01, 2013, 01:54:17 am
content: I recently quit smoking and switched to e-cigs and the company I bought the equipment from didn't send me a charger. I need to charge an AW brand IMR 18490 3.7V 1100mAh lithium ion battery. I ordered a charger but its not going to be here for another several days.I have an Owon ODP3032 programmable bench power supply and was wondering if there was any way to safely charge one of these batteries with it. It has constant current and voltage settings. The rate of the charge doesn't matter. I remember seeing on one of Dave's videos a long time ago that you can safely trickle charge lithium batteries.I don't have the knowledge to know if this is safe or not so I figured I had better ask.

author: IanB
author_rank: Super Contributor
timestamp: June 01, 2013, 02:17:52 am
content: It's completely safe and straightforward. Lithium ion cells are charged using a CC/CV algorithm. To charge your IMR 18490 battery, set the voltage limit to 4.2 V and the current limit< 3 A< 1 A or so, connect up the battery and start charging. The charging is complete when the current has decreased close to zero, say below 100 mA (this is not critical).The only advantage of a dedicated battery charger over such a bench power supply is the convenience.(With all lithium ion cells, it is a good idea to place the battery on a non-flammable surface, far from any combustible materials when being charged. Although IMR cells are "safe chemistry", it is still advisable to take precautions.)

author: skysurf76
author_rank: Regular Contributor
timestamp: June 01, 2013, 02:19:29 am
content: Thanks so much Ian. I have researched it a little on the internet but just wanted to check. I'm just not in the mood for a fire or explosion tonight.

author: skysurf76
author_rank: Regular Contributor
timestamp: June 01, 2013, 02:53:26 am
content: Quote from: IanB on June 01, 2013, 02:17:52 amGotcha. Full anti-Murphy measures!

author: digsys
author_rank: Unknown
timestamp: June 01, 2013, 03:28:11 am
content: Quote from: skysurf76I'm afraid I'm going to have to disagree with part of this. You run Constant Current at up to C_Rating_MAX up until the current dropsby about 1/10 - 1/20, then you swap to C_Voltage. You can mess with the change-over point, but if you stay at a higher current,you WILL reduce cycle life and have reduced capacity. But MOST important is the amount of BULK energy you put into the battery !!That figure varies per battery type, and how fast you charge it, but it may be around Capacity (C) +20%In other words - many types of LiION can NOT be trickle charged after bulk energy limit is reached. You can degrade cycle life at a rapidrate or worse, have a melt-down. It's not worth the risk.I do know a bit about LiION charging, I make BMs for Solar race cars, and we sometimes DO push the Bulk limit to gain abit more energy, AND we pay the price for it.Your best bet it to work out how long it will take to top-up at the CV point, which should be pretty constant, and put in a timer shut-off.All dedicated LiION chips have CC-CV, Capacity and Temp profiles included.

author: IanB
author_rank: Super Contributor
timestamp: June 01, 2013, 03:51:40 am
content: Quote from: digsys on June 01, 2013, 03:28:11 amIt's not like this. Constant current means constant current. The current is constant, set by the charger. It won't drop to 1/10 or 1/20 because in constant current mode it won't drop at all!What happens is that you charge with constant current and as you do so the cell voltage climbs. Eventually the cell voltage reaches the set voltage limit (4.2 V) and the charger automatically switches to constant voltage for the remainder of the charge, andthenthe current starts falling. This is where you wait for the current to fall to say, 5% of the initial value, and then you can stop the charge.QuoteExcept you have no control over the change-over point. The charger decides this based on the voltage and current settings you use.QuoteAgain, you can't stay with the higher current unless you exceed the maximum charging voltage, which you (which the charger) is not supposed to do.QuoteReally not. The charging efficiency of lithium ion is fairly close to 100% and does not vary a lot with the charge rate.QuoteThis isn't what happens. You charge until the end of the CV phase, andthen you stop charging. If you mean it is harmful to keep charging a fully charged battery, then of course this is bad. Don't do that!QuoteIt always pays to watch the charging process and make sure it is going to plan. The advantage of a bench power supply is you can see the voltage and current readout on the screen throughout the charging process. You can therefore see if anything is not working much more easily than with a "black box" charger.Temperature is not part of a typical lithium ion charging algorithm, other than to detect excessively high temperatures as a fail safe and abort the charge if so.

author: Dave
author_rank: Super Contributor
timestamp: June 01, 2013, 04:00:37 am
content: Edit: This post is obviously a reply to digsys. Ian just cut in between while I was typing it up.---------------What you just wrote is a load of bull excrement. If you are pushing CC into the battery, the current never drops to 1/10 -1/20 C, because it's CONSTANT. You also can't force the power supply into an operating mode, it just does what the load dictates.You should charge your batteries with a constant current (max current determined by the C rating - preferably you should use 1/2 C or so), until the battery reaches the maximum voltage (4.2V), at which point the power supply will go to CV mode. The charging should be continued in CV mode, until the current drops to 1/10 - 1/20 of the set maximum current. That's when the charging is done.

author: digsys
author_rank: Unknown
timestamp: June 01, 2013, 04:11:19 am
content: Yes, I assumed everyone knew that you STILL SET a Max_V limit, I credit people with some understanding.As for all the rest of the diatribe, YMMV. Have a nice day :-)

author: ConKbot
author_rank: Super Contributor
timestamp: June 01, 2013, 07:25:28 am
content: Quote from: IanB on June 01, 2013, 02:17:52 amAn 18490 in IMR chemestry will most likely be ~1AH. So 3A might be a tad steep, a 3C charge on an IMR probably wont set your room on fire, but you wont be doing anything for cycle life. 1C would be taking it easy on the battery for long life. Though there is plenty of power tool lithium chargers which do a full charge in 30 minutes, so maybe 3C for 20 minutes and ~10 minutes of CV isnt so horrible. If youre not in a rush though, no need to rush things, imo.

author: IanB
author_rank: Super Contributor
timestamp: June 01, 2013, 07:52:00 am
content: Quote from: ConKbot on June 01, 2013, 07:25:28 amOh, you are right. I thought I had looked up a data sheet for this particular cell and seen a max charge current of 3 A listed, but I looked elsewhere and this time I saw 1.5 A. Since the battery is 1100 mAh it would be more gentle to limit the charge current to 1 A.

author: amyk
author_rank: Super Contributor
timestamp: June 01, 2013, 10:57:34 am
content: Lots of information here:http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries1C is usually the maximum current lions should be charged at, unless they're special types designed for higher rates; keeping the current a little lower will make them last longer too. (Same with voltage - if you don't mind slightly lower capacity, charge to 4.1 instead of 4.2V to increase cycle life.)

author: eKretz
author_rank: Frequent Contributor
timestamp: June 01, 2013, 04:16:21 pm
content: I have been charging Li-ion batts for a couple years now with a bench supply. I never exceed .5-1C in CC mode, it works great. Set the voltage to 4.15 and short the cables to set CC limit, (my supply doesn't have a preview function) then hook up and go. I have a battery holder set up to charge 6 18650 cells at a time in parallel. CC runs until it drops, then switches to CV. When the current drops to .1-.2A I shut it off. Nary a problem in 2 years worth of battery use and charging.

author: skysurf76
author_rank: Regular Contributor
timestamp: June 01, 2013, 11:07:43 pm
content: I've just been charging the batteries at a constant current of 500mA, and once the voltage gets to 4.15V I take them off. The charge has been lasting plenty long, and I wanted to play it safe and baby them. Its been working great. I don't need to really fully charge them, just enough to make them usable, and its just a stop gap measure until I get the charger on Monday.

author: IanB
author_rank: Super Contributor
timestamp: June 01, 2013, 11:56:48 pm
content: What charger are you getting? You may find it strange to know, but your bench power supply may do a better job than your charger.The bench power supply is, after all, much more expensive

author: skysurf76
author_rank: Regular Contributor
timestamp: June 02, 2013, 01:19:01 am
content: I think the one I ordered is a Tenergy. I'm really not sure. Its just a $17 cheapo they had.I want the charger though because it took me 20 minutes last night to figure out how to get wires from the power supply in contact with the batteries terminals. My final solution is pretty comical. I should upload a picture. The battery goes into a tilted spool of wire with a banana plug under it that makes contact with the negative battery terminal, and the positive power supply wire is a banana plug with an alligator clip on it connected to the positive battery terminal. Rube would be proud.

author: IanB
author_rank: Super Contributor
timestamp: June 02, 2013, 02:01:44 am
content: Quote from: skysurf76 on June 02, 2013, 01:19:01 amMagnets. Battery terminals are made of steel. Those tiny-but-ever-so-powerful neodymium magnets stick ever so well to batteries and to alligator clips.

author: skysurf76
author_rank: Regular Contributor
timestamp: June 02, 2013, 02:15:39 am
content: You're a genius Ian. I have a stack of 10 little dime size super magnets too. I got them in an order from Electronics Goldmine once. Figured they might come in handy. I figured someone might have some slick idea like that, but I didn't want to look completely helpless. Should have just swallowed my pride and asked lol.

author: skysurf76
author_rank: Regular Contributor
timestamp: June 02, 2013, 02:33:38 am
content: I have another question that pertains to all this. My power supply has a constant current setting, constant voltage, overcurrent setting and over voltage. To charge the battery I have CC=500mA, CV=4.15V, OCP=800mA, and OVP=4.2V. The first time I charged it the power supply started in constant current mode, but when I came back the power supply was beeping and OVP was flashing and it had shut off the power.I assume as it charged at 500mA the voltage slowly rose, but for some reason it didn't switch over to constant voltage. Any ideas as to what happened?

author: IanB
author_rank: Super Contributor
timestamp: June 02, 2013, 04:47:39 am
content: It depends on the quality of the power supply. For instance:https://www.eevblog.com/forum/testgear/comparing-two-power-supplies/Look at the horrible voltage overshoot of the Extech in these tests.I don't know how that Owon performs, but perhaps it isn't perfect. Maybe you set the OVP threshold a bit too low compared to the CV setting? Try setting OVP at a value more like 4.5 V and see what happens. Watch the power supply closely around the point of transition.

author: skysurf76
author_rank: Regular Contributor
timestamp: June 02, 2013, 05:02:03 am
content: Ok, that makes sense. I'll give it a try.

author: SeanB
author_rank: Super Contributor
timestamp: June 02, 2013, 05:37:50 am
content: No duct tape?I have done that often to charge odd cellphone batteries to check if it is the battery pack or the phone that is giving the no charge problem.

author: skysurf76
author_rank: Regular Contributor
timestamp: June 02, 2013, 05:49:56 am
content: Quote from: SeanB on June 02, 2013, 05:37:50 amAs a man I'm embarrassed to admit duct tape never dawned on me. =P

author: SeanB
author_rank: Super Contributor
timestamp: June 02, 2013, 06:37:07 am
content: I have used it for many things , up to using as a bandage on a cut ( lost a little hair during removal though - ouch) and using it for anything but for ducting, where I use an aluminium backed adhesive tape.

author: peter.mitchell
author_rank: Super Contributor
timestamp: June 03, 2013, 11:11:33 am
content: Quote from: SeanB on June 02, 2013, 06:37:07 amThis sentence is probably the single most truthful comment on the EEVBlog forum.