Lithium Batteries

[ChrisOlson]

Well guys, I'm not going to be storing my battery in the 'fridge just to avoid the "what the hell is this?" question that I'd be sure to get from my bride when she finds in there. Even after I explained it to her, all I'd get is, "I don't care - there's not going to be batteries in the 'fridge."

But the next time I use the trimmer I'll check the voltage after I'm done with it and see where it's at. Can't figure out how that motor on the trimmer can put out that kind of power and only use 20% SOC out of a 2ah battery.

[Sunking]

PN manufactures only send the batteries out the door at 50 to 60% SOC. Personally I run mine between 20 to 80%, and store them at 60% in the fridge.

[PNjunction]

What is the voltage range from fully discharged to fully charged?

Looks like everything is normal. Here is the rough breakdown per cell. Ours has 5 cells in series. Most suspect the NMC mix, or lithium-nickel-manganese-cobalt, like a Sanyo UR18650W2. In the early days, these tools typically contained the A123 LiFeP04's, but the safety of the NMC is about on par, with a bit more energy-density to boot. Somewhat in between the lifepo4 and the unstable lico02.

Sunking - we need you to take one of these apart. I just don't have the torx head or whatever it is to do it myself. A side benefit of all this is that my yard is looking better than ever. Little do my neighbors know that while I detest yardwork, I convince myself that I'm only doing cycle testing, which is far more interesting.

Here's a quick / rough breakdown on SOC, but this assumes you have a voltmeter of at least the accuracy of a Fluke 87V or *better*. We are hoping that by fully charging the pack, the battery's internal pcb is also doing top-balancing. These are ballpark values since the chemistry mix, age and use patterns will modify it a little bit. Since I don't know the actual cell manufacturer, this is what I go by.

Individual cell resting ocv: (multiply by 5 for our packs)

4.2v = 100%
4.1v = 90%
4.0v = 80%
3.85v = 60%
3.77v = 40%
3.7v = 20% < -- about the lowest I'd go for maximum cycle life
3.6v = 10% < -- you can go here, but it will cost you
< 3.6v = approaching the LVC.

This may save the pack from catastrophic damage, but one shouldn't rely on the lvc for normal use. Kind of like using a lead-acid ac inverter's lvc of 10.7v on a regular basis. Nobody in their right mind would want their Pb battery to go to 10.7v in normal cycling.

Yesterday I picked up the drill, and the battery was from 2012. It had an out-of-box pack voltage of 18.37v or about 3.7v per cell. That's about right - if they come charged from the factory at about 40-60% SOC, and two years of self-discharge and heat during retail storage, I just about made it before things got nasty. I'm sure the single ones still sitting on the shelf from 2011 would be into the deep discharge knee, and recovery a bit iffy. A different retailer had fresher ones, so it's always wise to check.

I'm changing my plan according to use vs convenience, and incorporating cold (but not freezing) storage during periods of non-use to help cut down on parasitic reactions.

For the blower / trimmer, I'll just let it charge to full, and store in the fridge with a ziplock, and give it an hour to thaw before weekend use. I gotta' get out there and get the job done, so I'm not going to wait for a full charge in addition to thawing by going obsessive over lowered-voltage storage. I'll just buy a battery a bit sooner.

For the drill, if I only drill 5 small holes every other month, it makes no sense to always keep it fully charged prior to storage in the fridge. I'll monitor the soc, and if it is above 50% DOD, I'll leave it be and put it back into the fridge. Once it reaches 50% DOD or a little bit more, I'll either full-charge it again, or maybe just a bit of a boost and back to the fridge. If I envision a heavy duty session, then of course I'll be sure to fully charge first. Since this is just for home-type stuff and not daily construction work, this is the plan so far.

Time / optimum storage voltage / convenience - pick any two depending upon application.

[Sunking]

What is the voltage range from fully discharged to fully charged? It took exactly one hour to recharge the battery to solid green after the normal use. That's only .4ah according to the amount of current it says the charger puts out. Since the battery is 2ah I must've drawn it down to only 80% SOC (less losses in charging, but the battery never got warm during the charging). It was 20.7V on those two sockets, just like yours, when it went solid green.

Chris what lithium chemistry are they? Lithium batteries will not heat up much under charge unless they are charge in excess of 1C or over charged. They have very low internal resistance, thus not much heating. If they are getting warm something is wrong.

Anyway the voltage range depends on chemistry. I suspect LiPo, 4.2 @ 100%, 3.0 @ 0% but never take them below 3.3.

[ChrisOlson]

One way you can check is that you can measure voltage across the two uppermost outside edge clips. Fully charged, mine read about 20.7V (4.14v per cell unloaded) on a Fluke 87V. That's a little high for my tastes, but perhaps the B&D / battery vendor engineers seem ok with that.

What is the voltage range from fully discharged to fully charged? It took exactly one hour to recharge the battery to solid green after the normal use. That's only .4ah according to the amount of current it says the charger puts out. Since the battery is 2ah I must've drawn it down to only 80% SOC (less losses in charging, but the battery never got warm during the charging). It was 20.7V on those two sockets, just like yours, when it went solid green.

[PNjunction]

Before even opening the ziplock bag, of course.

I forgot about that - it's important.

Small world - here we are going on about the B&D lithium batteries, which in high likelyhood might be the NMC type, which prof Jeff Dahn and students brought to reality what seems like ages ago. Onwards!

[PNjunction]

... All it does is flash green then go to solid green when it's charged up (unless I didn't use enough power from it). I could've swore it was orange when we got the trimmer and I charged the battery for the first time. So now I don't know how long to charge it for.

The little wall-warty LCS1620, flashes green just once upon applying power. Then when you slide a battery in, it will constantly flash green while charging, and when the flashing stops and it is solid green fully charged, it stops. If it quick-flashes red, then the battery is bad. If it flashes an alternate long and short red, then it is in temperature-hold, waiting for the ambient temp to either cool down or heat up before it will attempt to charge. I'm sure (but haven't verified) that when the charge is done, the green led will stay lit, but there should be no charging.

Part of the sales pitch is that you can leave these things in the charger all the time, since the battery has the brains to stop the charge.

One way you can check is that you can measure voltage across the two uppermost outside edge clips. Fully charged, mine read about 20.7V (4.14v per cell unloaded) on a Fluke 87V. That's a little high for my tastes, but perhaps the B&D / battery vendor engineers seem ok with that.

[inetdog]

... Thaw for an hour at room temp prior to use....

Before even opening the ziplock bag, of course.

And thanks for the link. Popcorn tonight, since most of the good TV shows are now in reruns.

[ChrisOlson]

First lawn mow of the season here and I just used our trimmer for normal trimming around trees and all the stuff where the rider mower can't reach, and it never ran out of power. When it came time to charge, I thought the little LED on our charger turns colors. It flashes red, orange, green, then solid green when it's charged up. But it don't. All it does is flash green then go to solid green when it's charged up (unless I didn't use enough power from it). I could've swore it was orange when we got the trimmer and I charged the battery for the first time. So now I don't know how long to charge it for.

[PNjunction]

I agree. But I don't know if I want to take it to the same level of obsession that i do with flashlights. Hello Candlepower forums!

I mean, i broke out the Fluke 87V, started thinking of how to make a custom connector to link up to a Revolectrix Cellpro, and then stood back and asked if I was taking it a bit too far. I'm just going to keep if off the top after a full charge, and if not in use for a day or two, pop it into a ziplock and throw it into the crisper of the fridge. Thaw for an hour at room temp prior to use.

While high voltages during storage aren't ideal, the following made me wonder if it is really masking a secondary issue that may be far more important - electrolyte additives and it's affects.

Check this out from Professor Jeff Dahn of Dalhousie University:

https://www.youtube.com/watch?v=pxP0Cu00sZs

It's a long one, so break out some popcorn, pencil and paper first.

[inetdog]

For long term storage "taking a little off the top" is not going to make a big difference. The general opinion that i have seen is that somewhere is the range from 60% to 80% of full charge is the best balance between long life and being able to use them immediately for a long enough time without recharging first.

[PNjunction]

Ok, I'm in. Got the same trimmer and a drill. Date codes for the battery and charger are 2013 so that's good, especially when the box of stand-alone batteries on the shelf was dated 2011! No thanks. Also picked up the fast-charger (2A) just in case I need to finish a job and run short.

Charging via my 120W Samlex PSW inverter from my solar-charged Optima - no sweat there when used with the included slow chargers. However, I smoked the fast charger. Not sure if it was somehow related to the inverter, or just luck of the draw in the QC department. Suppose I should have tried the poco AC first. Fortunately, no harm to the battery.

Although I haven't torn the battery apart, it appears to be an 18650-based 5S pack of either Lithium-manganese or lithium-nickel. I seriously doubt it is lithium-cobalt. I wouldn't be surprised if there were 5 Sanyo UR18650W2's in there. Based on some repair photos, I see a custom PCB and what looks like bms wiring. So the smarts are in the battery more or less.

The little wall wart charger / monitor does not appear to provide any soc other than full charge. Overtemp / bad battery / charging / full charge is all we got.

I believe that there is an LVC, an HVC, and bms balancing of some sort. However, I don't want to hit the lvc if I don't have to. The chargers appear to bring the batteries up to 95-100% or so unloaded (4.1 / 4.2v per cell). I don't like the idea of keeping them there for more than few days like that, so I'll probably stick to the original plan of pulling the trigger for 30 seconds or so after a full charge just to get them off the top. For normal people that use it every week it probably won't matter as the battery ages on it's own whether it is lovingly cared for or not - and just get a new battery a month or two earlier.

In fact, with the light duty mine will be subjected to, I may be able to actually just charge every other time. Still, it appears that finishing a full charge probably accomplishes some balancing which is a good thing. I'm not going to take these to the RC / Flashlight extremes of maintenance, although one could certainly do that.

[inetdog]

Well, you already know more about the charger than I do. I had to take a look and it actually says LCS1620 on the charger's power brick. The little thing that attaches to the battery to charge it has four blades that engage with four sockets on the battery. But on the tool there's only three blades, so one socket isn't used on the tool. I wonder what's up with that?

Many good possibilities:

1. There is a diode in the pack such that the normal tool contacts cannot send current back into the battery.
2. The fourth contact is part of a "four terminal" voltage sensor so that the charger knows what the voltage at the battery is regardless of IR loss in the charging circuit and contacts.
3. The fourth contact is part of a signalling circuit between a rudimentary BMS system in the battery pack and the intelligent charger so that the BMS system can tell the charger to shut down.
4. The fourth contact is part of a battery temperature sensor circuit. But in some cases (like an toy electric car or a Dyson portable vacuum) the tool itself will monitor battery temp too.

[ChrisOlson]

Well, you already know more about the charger than I do. I had to take a look and it actually says LCS1620 on the charger's power brick. The little thing that attaches to the battery to charge it has four blades that engage with four sockets on the battery. But on the tool there's only three blades, so one socket isn't used on the tool. I wonder what's up with that?

I think it's a pretty good weed whipper for a cordless one. The other thing is that it doesn't have a bump to feed spool. It has some sort of centrifugal line feed deal in it that works really good. It never over-feeds the line so it hits the little blade that cuts off the excess, and always keeps a decent amount of cutting line out on the spool. I'll have to take that apart and figure out it works.

[PNjunction]

Ok, that's a different story!

The included LCS20 (I think) charger looks to be smart enough for consumer use. However my curiosity is piqued by the "maintenance mode". What does that mean - balancing? Just stopping the charge when full? Or after a set period of time, discharging the battery back to 50% DOD or so? If the latter, that could be a problem for users who don't check the SOC reading, and might need to charge after a long period of disuse.

I kind of wish you didn't post that, because now I'm going to have to get one to find out. For fun, perhaps I'll charge it from my solar / AGM battery setup and a psw inverter, as inefficient as that is.

I think I see the problem - most consumers are doing brush-clearing, fake lawn-mowing, and not actual trimming. Unrealistic expectations of more than 30 minutes of continuous use. Not recharging after each use, and just running it until dead every time. Not realizing that during this 30 minute period, they are getting full power, rather than a gradual decline like their old nimh packs, which they took well down past 80% DOD on a regular basis. Storing and charging in a hot garage.

I'll let you know if I am putting my foot into my mouth when I grab mine and see what's up. A spare battery, or the fast charger might be fun too.