Lithium Batteries

[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.

[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.

[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.

[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.

[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!

[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.

[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.

[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]

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.

[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.

[PNjunction]

Funny - I got the same treatment when I tried to put an Optima Blue-top on the bottom shelf.

The LED light, model BDCF20 arrived today. Makes sense to have a work light, or otherwise be able to put the batteries to use as light when necessary. I like it a lot, but I'll save the beamshots and other flashlight review material for Candlepowerforums. Does not come with a battery, figuring you'll use what you already have.

The best part is that this will serve as a controlled discharger, so I can take it down to whatever soc level I want when I feel the need. Later I'll put a timer on it, and get some data. Sure is a lot quieter way to discharge.

[Sunking]

Funny - I got the same treatment when I tried to put an Optima Blue-top on the bottom shelf.

The LED light, model BDCF20 arrived today. Makes sense to have a work light, or otherwise be able to put the batteries to use as light when necessary. I like it a lot, but I'll save the beamshots and other flashlight review material for Candlepowerforums. Does not come with a battery, figuring you'll use what you already have.

The best part is that this will serve as a controlled discharger, so I can take it down to whatever soc level I want when I feel the need. Later I'll put a timer on it, and get some data. Sure is a lot quieter way to discharge.

PN sounds like you have some electronic background. I have a few circuit schematics for a constant discharge current load that can be tailored to about any voltage range one want. Great tool to measure battery capacity. Let me kno wif you are interested. Pretty simple really just a could of transistors and power resistor with a OP amp voltage reference.

[ChrisOlson]

Hey, B&D makes a LED light that uses that same battery? I might have to get one of those the next time we go into Duluth. I always can use a nice worklight.

[PNjunction]

PN sounds like you have some electronic background. I have a few circuit schematics for a constant discharge current load that can be tailored to about any voltage range one want. Great tool to measure battery capacity. Let me kno wif you are interested. Pretty simple really just a could of transistors and power resistor with a OP amp voltage reference.

Sure I'd love to see that. Honestly though, I'm not much of a builder any more (sadly). I've got a West-Mountain-Radio CBA-IV analyzer when I need to get down and dirty. Still, it might inspire a trip to mouser etc!

[PNjunction]

Hey, B&D makes a LED light that uses that same battery? I might have to get one of those the next time we go into Duluth. I always can use a nice worklight.

Yep, it's pretty handy:

http://www.blackanddecker.com/power-tools/BDCF20.aspx

But be VERY careful! If you forget about it like I did last night, it will silently take you down to the LVC, something we want to avoid. In fact, the light can do worse damage to the pack by doing it slowly, unlike accidentally letting the high-current powertool do it. Basically, TIME spent at either the very high voltage or extreme low voltage is the multiplicaton factor for damage.

I'm going to time out the soc's from a full charge next time I stay awake!