I have a question related to batteries. Anyone have good knowledge on the subject?
The Blind Eternities forum
Posted on Aug. 11, 2023, 8:51 p.m. by TypicalTimmy
When I started at my new job, we had thrown away three 6ah (Amp Hour) DeWalt batteries for our power tools. The reason? They no longer held a charge.
Well, six months later, we just threw a fourth one away. Same reason. You plug it in, it says it's charging, gets super hot and when you unplug it to cool it down, later you use it and it's dead. Again, no charge.
- We have multiple chargers, and multiple batteries. We know the chargers are good, because they don't cause harm to other batteries. Is it possible we had a defective battery? Sure. But FOUR? Unlikely.
Now, I had heard years ago that if you use the wrong charger, you can "burn out" your batteries. In this case, if you plug a 6ah battery into a 5ah charger, over time the 5ah charger somehow ruins it.
The theory suggests you can never go down, only up. You can charge a 5ah on a 6ah charger, but not a 6ah on a 5ah.
That's true for many applications. If the pressure of your gas line mandates Schedule 40, you can use Schedule 80 because it's thicker. But if you use Schedule 20, you're liable to cause leaks and blow your lines out. Similarly, if you have a 7.5uf run capacitor on your furnace that is toast, but you only have a 10uf, that's okay. But a 5uf is no good.
Or if your panel requires 12 gauge wire. You can put 10 gauge (thicker), but not 14 gauge (thinner).
So the theory is, you can never step the CHARGER down, otherwise you'll damage and ultimately destroy the battery.
But here's the thing...
I can not find one single explanation online. Not Reddit, not Quora, not YouTube, not other message boards, not Facebook groups?
So does anyone here have insight? Is that actually a bad thing?
Because if not, we have other issues to look at as to why batteries keep burning out at work.
Thanks.
TypicalTimmy says... #3
Personally, I prefer the current line of Bosch. The reason?
So my uncle was an engineer before he retired. Unfortunately he does not speak with our family anymore. Anyway, he explained to me once that there are three scopes of tools.
You have the "Home Improvement" brands, such as Black and Decker or Craftsman. These are low cost tools that get the job done for projects. Need to hang a door? Put up new trim. Build a new deck. These tools work well for that. These are the kind of tools you bush the dust off once or twice a year and use. Nice, affordable tools.
Then you have the "Handyman's" tools. These are tools that are under constant, albeit light work. Like a carpenter or a car mechanic. These are the tools used all day every day, but the environments they are used in are not hazardous to the tools themselves. These are your Ryobi, Makita, Bauer, etc.
Then you have your "Commercial" grade. These are the ones you absolutely abuse. The ones that get thrown into tool buckets, carried on top of a lift and used to cut apart I-Beams. These are the ones you're using to crack open the casing of a water pump. These are the ones you're torquing down to get tractor tires off. The ones that need to withstand impact, shock, heat, etc. These are the ones that if you don't have, you'll break whatever else you're using. Basically your DeWalt and Milwaukee and a few other brands.
I prefer Bosch because it sits between Handyman's and Commercial. They withstand tremendous abuse and impact, but aren't nearly as expensive as the Commercial grade tools.
Also a good rule of thumb:
If everyone is using X, buy Y
People won't steal your Bosch if they are using DeWalt... because they can't charge it ;)
August 11, 2023 9:20 p.m. Edited.
I wonder if the time of charge has anything to do with it. Most newer chargers will turn off when the battery is full but I remember years ago you had to be really careful on how long your battery charged because going beyond 100% would cause serious damage, similar to what you describe of hot terminals and then they won't hold a charge. It could also be that on a lower amp input the smart charge system isn't working correctly and it just keeps charging.
I really have no idea for sure, but if your volts are correct it shouldn't really matter the amp input. Like, on a car charger you can set it to different amps to charge up at different speeds, 32 is like a quick charge and 4-5 is a trickle charge, but they both are safe to use.
Again, no expert on electricity here, I just remember older hand tools where you had to keep a very close eye on the charge up because overfilling was a serious problem, and that makes me wonder if it's just not triggering the shut off for some reason.
August 12, 2023 10:34 a.m.
Gidgetimer says... #5
AH rating on power tool batteries is a capacity of the battery and has nothing to do with charging beyond how long it takes to get to full charge and how long it can be used before needing charged. (On a 1.5 AH battery a drill that pulls 1 amp can be run full speed for 1.5 hours or at a lower speed that draws .5 amps for 3 hours. Same drill same speeds on a 5 AH battery would be 5 hours and 10 hours.) I have never seen an AH rating on chargers, you will usually only have a voltage rating and an amperage rating on the charger. You will want to make sure the voltage and amperage rating on the charger match what the manufacturer recommends for the battery.
Beyond that, batteries wear out. If all 4 of the batteries have 5+ years of hard use on them I don't find it out of the ordinary that they would fail. I work for a midsized HVAC contractor and we have 25 technicians all with a battery powered drill, 1/4" impact, and Sawzall. I'd estimate that we have at least 1 battery fail each month.
On the topic of me working in HVAC... for the love of god, don't use the wrong size capacitor on your furnace. Get the correct capacitor, unless you know how to wire multiple capacitors to get the required capacitance.
August 12, 2023 7:04 p.m.
Ive worked with building electric bikes for a few years and if these are LiPo batteries I may have some insight, ignore if not. As stated by Gidgetimer, all of this info is correct. Chargers will only have voltage and amps, batteries will have voltage and amp hours.
The main thing you need to do is ensure your voltages are the same, that can screw up a battery big time or cause a fire.
Second, batteries are designed to not guarantee their maximum lifetime unless you follow certain procedure and purchase certain things. For LiPo batteries to maintain maximum lifetime of about 500 charges (dead to full charge) you typically should drain them to 40% and charge them to 90%. Neither of these are feasible on power tool batteries because of how they are run full to dead so you'll lose a lot of your lifetime there.
The other thing is to charge as long as you can as slowly as you can, again, basically impossible with power tool batteries as they never sell you a slower charger.
Another thing is I would not leave the batteries on the charger, only when they need to charge and take them off the charger when done. This may be the most likely issue. The batteries will "trickle charge" as in when they approach 100% on the charger the charge will slow down so it doesn't overheat until the battery itself drains itself to 98% or so then go back up via trickle charge. This is very bad for your batteries as it causes drain and charges while it's charging which is taking up your limited lifetime of the battery (once again typically 500 full charges on a good brand of battery cell). So while you think your batteries are charging they are actually wasting away while they charge.
If your batteries are 6ah and you have a 6A charger it will take 1 hour for your battery to fully charge from dead to full (given you have full capacity). Anything past this point is now hurting the battery. The formula is simple, AH/A gives you the hours taken to charge.
In this way you may be hurting your batteries double by fully charging them, they lose their maximum full charge (and now typically charge faster as they have less capacity) they sit on the charger for the same amount of time degrading them with each consecutive charge then they are drained to dead and put back on the charger.
After some time, your batteries will lose their maximum voltage. One of my batteries at home is a 52V 20AH. It fully charges at 58.8V and fully dies at 45V. Over time of charging the battery may get to 58.8V but will drain slightly slower as it cannot maintain the 58.8V anymore. This basically puts "pressure" on the battery as you're overfilling it. This also is not good for your battery. This is the same principle with home grade batteries but replace 58.8V with 1.5V and 9V.
Another thing LiPo batteries like are slow drains. If you are using the battery to it's max while you use it you are draining it faster than it likes.
All of these things taken into account, heavy use with full charging and sitting on the charger may kill a battery prematurely. 6 months time, I couldn't tell you.
Icbrgr says... #2
I've also had this lame luck at work... not with dwalt but with ryobi... I just thought it was a brand issue in my end... I have no idea
August 11, 2023 9:08 p.m.