The only problems besides the battery would be a high excessive current load being pulled by the motor for many reasons. Worn out parts are the most coming reason for excessive power loads.

To eliminate everything else except the battery you'll first need to find the continuous current draw for the motor, and I don't have that data but your saw should pull between 9 and 15 amps. Take the motor cover off and clamp an amperage meter around the motor lead and note the current (in amps).

If the motor is drawing it's rated continuous current load (or somewhere close) the battery is shot. If the current is high or very high there is a problem with the motor or the power head. The most common motor problem are it's bushings/bears. Problems with the power head could be as simple as dried up grease or worn out parts. The battery will also heat up quickly If the load is very high but not under a cutting load.

Most likely it's the battery. The ego batteries per their loss chart will lose 10% capacity over 500 charges and start rolling off quickly to about a 90% loss to 1000 charges. With these batteries it's not how old they are but how many charges they went through. Look on the battery to see if there is a production Date, but Ego hasn't been around long so even adding up 500 charges in it's life time would a stretch.

Your battery has between 14 and 42 cells depending on the battery size, and more likely one of the cells had suffered internal damage. When just one cell loses storage capacity the battery management system limits charging of all cells to the lowest capacity battery. This is for saftey to avoid explosions and fires. The result of one bad cell will ruin the battery pack even if all the rest are good.

Finally you could try and find a battery to borrow and see how well it works. Just make sure you're comparing apples to apples and the borrowed battery is the same capacity battery as yours.

I'm afraid I don't have a meter of the type that lets me measure current without interrupting the circuit. Which complicates things: do I want to buy another tool that I may use just once to find out if my tool is working? Not if I can help it...

At this point I'm inclined to deal with the problem by buying another battery. My reasoning: I want to buy another Ego tool (string trimmer), so I'll have a good use for a second battery even if the first one turns out to be good.

The first one is a 2.5AH (disappointing) battery dated 6/2018. I suspect that it hasn't been recharged a lot -- the saw looks almost new -- but it sat on someone's shelf without getting charged at all for a few years. I know Li+ batteries don't take kindly to that.

Yes, I bought it used through Facebook Marketplace. I took a risk and lost, but the price was good enough that I'll still come out ahead if the saw is OK. I could complain to the seller but I don't think it's worth the trouble if it's just the battery.

One thing surprised me: I looked at the Ego batteries for sale on eBay, and found a lot listed as "for repair or parts." And people are buying them. Can these things be repaired? It would make a lot of sense considering what they cost, but I've never heard of anyone repairing a battery pack.

Although I have NO experience with Ego batteries, it looks like there are repair possibilities. For example:

https://youtu.be/4NESKJ0beAc?feature=shared

Good luck with it!

Yes, the battery packs can be repaired but not something commonly done. I wouldn't recommend buying a used battery off of EBAY or you may end up with another weak battery, so buy new.

Your Lithium battery can easily sit a decade with a 30% charge because there is virtually no self-discharge with lithium batteries. Shipping rules require no more than a 30% charge is allowed for shipping, and even EGO's web site states batteries are shipped with a 30% charge and will last over 10 years in this condition.

If you measure your 56V battery fully charged it will actually have a voltage of 58.8. volts and this is called your float charge. Sitting around it will self discharge down to 51.8 volts and then virtually stop self discharging to a minute trickle over many years. Believe it or not the optimum charge for maximum longevity is to store lithium batteries with a 50% charge.

On the flip side a battery stored totally uncharged long enough will cause the battery to "fall asleep" and the Battery management system (BMS) will not allow it to recharge, but still may be good. Your Batteries critical voltage Where it will "fall asleep" is around 30 to 40 volts depending what EGO designed their BMS to stop a charge. IF someone let the battery drop below the critical level you would not even be allowed to charge the battery, but you are able to charge it so it wasn't ruined by letting it sit around.

Even below the critical level down to 22 volts a special battery analyzer can bypass the BMS and boost the battery up so the BMS will charge it. Below the 22 volts the battery will be toast with excess internal resistance buildup that can't be reversed.

@kevin9408, your post suggests that the existing battery can be restored if given some special attention, but it's not clear what needs to be done or who can do it. Can you clarify, please?

I measured the battery's no-load voltage at 52.8 to 53.0 volts. This is after a full charge and a very brief test in which the saw stopped running after a few seconds, several times, then would not run at all. At this voltage perhaps your comments aren't going to help, but I'd like to understand them as background for the future.

You said that a "special analyzer" can bypass the battery management system and rechanrge a battery when the voltage is too low. Is that something that any repair service that handles Ego equipment is going to have? Or must I go farther afield?

I got my multimeter out and realized that it does have jaws for measuring current flow without putting the meter in series with the circuit, but the manual says it's only for AC current. As I think about it that makes sense, because a constant DC current in a conductor generates a static electromagnetic field, which cannot induce current flow in a nearby sensor. But that makes me wonder how any meter could detect DC current flow, unless it has a little motor to spin the sensor in the field.

I didn't suggest it can be restored. It can't, it can only be reconditioned using good cells from other batteries to replace the cells in your battery that are bad. The analyzer I mentioned is to "wake up" a dead battery because the voltage dropped below a critical point and the BMS won't allow it to be charged. It will not restore any battery.

Your battery is not dead, it is not asleep, and it can be charged. The 53 volts tell me it's seen it's better days with the ability to hold maybe 1/2 of a full charge. If you stubble across a used battery for sale check the float (full charge) voltage so you don't get burned. The full float voltage is always going to be about 2 1/2 volts above the actual voltage stated for 100% capacity, live and learn. But what you learned today is your battery is the problem and there is nothing wrong with the saw. So you can buy a new battery without worry.

What did you pay for the used EGO chainsaw anyway?

Your last post confuses me. You said, " Your battery is not dead, it is not asleep, and it can be charged." Then you said, " But what you learned today is your battery is the problem and there is nothing wrong with the saw." Those two things seem mutually exclusive: either the battery's OK (and something must be wrong with the saw or the charger) or it's not.

My own impression, based on knowledge of how electricity and electric motors work but no particular knowledge about Li+ batteries, is that something is wrong with the battery that allows it to deliver near-normal no-load voltage, but prevents it from delivering enough current to operate the saw.

What I paid: $200 for the saw with 18" bar, bar cover, 2.5AH battery, charger, and original box.

An afterthought: I thought about how I might have avoided this hassle, and I realized that something doesn't fit. I tried the saw before I bought it. I met the seller in the parking lot of a Starbuck's, so I didn't run it very long, but I ran it longer than I can run it now before it poops out. What changed between then and now? It's not because the seller charged it up just before bringing it to show me. I charged it up just before I tried to use it. And he couldn't have replaced a good battery with a bad one after I tried it; he gave me the saw in the box, and after i tried it I put it back in the box. It was a simple short transaction with no interruptions or distractions; no way he could have taken the saw out of the box, changed the battery, and put it back without me noticing.

Well good luck, I'm done.

I solved the problem by buying a new Ego string trimmer with its own battery and charger. I charged the new battery on the new charger, and it runs the chainsaw just fine. I'm now charging the old battery on the new charger, and the charger's fan is running, as it did when I charged the new battery, and did not when I tried to charge the old battery on the old charger. (I didn't know there was a fan until I got the new stuff.)

So the chain saw is OK, I'm pretty sure that the old battery is OK but the old charger is defective.

I'll have to run the new battery down and try charging it on the old charger before I make an absolute pronouncement, but I'm sure enough of this to bet quite a bit of money on it ... if I was a bettin' person, which I'm not.

That battery 2.5A is too small for the saw. It should have a 5A battery. They may have given you a smaller battery and kept the big one. it will not run on the 2.5A battery.