Is there a smart charger for DeWalt 20v MAX/Flexvolt batteries?

[newbury]

With increasing investment in 20 V MAX batteries since 2012, and now having about 3 of the old small ones finally fail, I'm wondering if someone has come up with a real smart charger that could charge my batteries up to the recommended 70% and hold them there.

I've read that it's best to only charge the batteries to 70% and then put them aside.

Most of the time I only have 3 or 4 batteries "active". For instance right now I've a grinder, a 1/2" drill, a leaf blower, a trimmer and several flashlights I'm using frequently. Plus I've 4 batteries set up on my DEWALT 1800 Watt Portable Power Station and Parallel Battery Charger for when the power goes out.

I'm currently trying to charge the batteries when they go to 1 bar and charge them just after they hit 3 bars. But for batteries that run $15/AH I'm looking to maximize their life.

 

[WranglerX]

Where did you get the 70% charge information , personally I never heard of it....

I am trying to preserve the old system of NI-ION (?) batteries (DeWalt DC9096) so I don't have to spend thousands to replace batteries and tools or hundreds for a adapters and new batteries to go to new battery system....

My philosophy has always to been stay within one battery system sort of "one size fits all".... Have seem people with several battery/tools systems that are not cross compatible and they never have enough charged fresh batteries to use while depleted battery is charging....

Dale

 

[Rebeldad1]

Just put the battery on the Dewalt charger and let it fully charge. It will also monitor and keep it charged and ready to go. The charger is going to be a lot smarter charging than you are. I have a few 20v that are 6 years old and still work as good as new ones.
You want the latest and greatest on the Dewalt charger line they just came out with a new rapid charger.

 

[newbury]

Where did you get the 70% charge information , personally I never heard of it....

I am trying to preserve the old system of NI-ION (?) batteries (DeWalt DC9096) so I don't have to spend thousands to replace batteries and tools or hundreds for a adapters and new batteries to go to new battery system....<snip>

I had read "several places" that 70% was what to store them at. Upon investigating today I find:

There is virtually no self-discharge below about 4.0V at 20C (68F); storing at 3.7V yields amazing longevity for most Li-ion systems.

BU-72: How to Store Batteries – Battery University

So actually I should change my procedure to
1. Charge fully
2. use to 1-or 2 bars - NEVER drain down all the way
3. set aside until I figure I will be needing in the near future, then charge fully.

On the subject of your DeWalt DC9096 - They make an adapter for the 20Vmax (and it might work with the Flexvolt) for your NiMH batteries. I got it for $79 and the NiMH batteries die sometime.

 

[LittleBill21]

there is absolutely nothing special about li ion charging profiles. its charge at full rated current (hopefully at the rated battery charge rate) to 4.20v then taper charge current down to a specific cut off level and stop charging. that the entire logic

3.80 is the storage voltage for a typical cell. simply don't fully charge the battery before putting it into storage. you can measure the voltage off the cells with a dvm, to see what individual cell voltage is.

 

[TractorGuy]

My manual says you can leave them on the charger if you want. I just recently learned you have to push the battery on the charger until it clicks like when you put it in the tool. I had just been setting mine in the slot and sliding them down until the light came on. All of a sudden they started flashing the light a few times then it would go on solid like they were charged but they weren't. Then I found a You Tube video showing that you were supposed to snap them into the contacts on the charger. Problem solved.

 

[LittleBill21]

This is in regard to long term storage, not a concern if you plan to use the battery pack in the next month or 2.

 

[dragoneggs]

I just counted and I have 12 DeWalt 20v tools some XR and 5 batteries ranging from 2ah to 5ah, also some 'XR'. I always charge them to full and then remove them when I see them sitting on the charger full. Could be a day or three. I don't try to run them down to quit and tend to charge them at one to two bars depending on if I am taking them off site being sure I have enough juice without having to bring chargers.

So far... as a hobbyist, weekend warrior type and helping others, I have never had any issues with my tools and batteries. I just don't worry about them like the old NiCads. I guess what I am saying is I haven't given too much thought in charging the batteries so I guess the existing chargers (two) are already smarter than me and good enough.

All that said, a professional with daily all day requirements might fare differently.

 

[rangerfredbob]

It's better to leave them fully charged than discharged, I honestly have some lithium batteries that are 13 years old and they work fine... I've never paid attention to "doing the right thing to store them". I have a fancy charger for RC airplanes that tells me how much energy it puts in during the charge so I can keep track of capacity and some of the old ones still work fine or are at around 75% of what they once were.

Basically, just keep them fully charged, when they die it's probably just one cell that went out which is just the name of the game in batteries... I have one genuine M18 battery with a dead cell (the small packs), and a cheap Amazon M18 5Ah pack that lost a cell and had a bad weld on one cell... thinking of mixing the two together to get one...

 

[LittleBill21]

It's better to leave them fully charged than discharged, I honestly have some lithium batteries that are 13 years old and they work fine... I've never paid attention to "doing the right thing to store them". I have a fancy charger for RC airplanes that tells me how much energy it puts in during the charge so I can keep track of capacity and some of the old ones still work fine or are at around 75% of what they once were.

Basically, just keep them fully charged, when they die it's probably just one cell that went out which is just the name of the game in batteries... I have one genuine M18 battery with a dead cell (the small packs), and a cheap Amazon M18 5Ah pack that lost a cell and had a bad weld on one cell... thinking of mixing the two together to get one...

sorry, no fully charge is not correct, if you want longevity, battery manufactures recommend between 20-80% charge. multiple sources out there on this, even telsa i believe only charges to 80% or so unless you explicitly tell it to charger higher.

 

[K5lwq]

You should charge 100% every time you charge. If you are going to store for long periods at a time then discharge the pack about 20% or so.

Most smart chargers or fast chargers will use constant amperage until the pack is 80% to 90% then switch to constant voltage. This last 10% or so is when the chargers can balance the cells. Keeping a pack healthy is more about balance than how they are stored.

 

[LittleBill21]

I am going to drop this link here, hope some people will read it, but i have studied batteries for a while, the thought process is quite different then it use to be for batteries. li ion and lipo simply last longer if there are shallow DOD (dept of discharge), they also don't like being fully charged. the article below explains this in quite some detail.

How to Prolong Lithium-based Batteries - Battery University

"Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles"

I would read the article, it will change the way you think about batteries

"Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC."

Also be aware that balancing depends on the charger, some balance on the charge side, some balance on the discharge side using bleed off resistors.

my drone uses pretty expensive lipo batteries, over 120 dollars each, the batterys by design automatically drops to 60% if not used for 7 days

https://dl.djicdn.com/downloads/mavic/Mavic+Pro+Intelligent+Flight+Battery+Safety+Guidelines-EN.pdf

page 5 under battery storage.

I hope this will clear up some confusion

tesla recommends between 50-90% charge.

Daily Life with the Tesla Model 3: Charging | It's Electric.

 

[rangerfredbob]

sorry, no fully charge is not correct, if you want longevity, battery manufactures recommend between 20-80% charge. multiple sources out there on this, even telsa i believe only charges to 80% or so unless you explicitly tell it to charger higher.

That's pretty much exactly what I said, or was trying to say... What I meant is it's better to leave it fully charged than leave it at the point the low voltage cutoff on the tool kicks in.

Doing everything "correctly" doesn't mean 100% success, there's still the luck of the draw, I have some lithium batteries from 2007 that still work to 80% of rated capacity, I had one drop one cell out of like 8 battery packs...