I'd love to know this as well. Anyone that could test, I'd also be very appreciative of the information.

Edit -- Am in the market for an Allett Liberty reel mower, but I'm already heavily invested in Ryobi ecosystems (18V and 40V), and so if I could get my handful of 40V Ryobi batteries to work with the Allett then it'd be a no-brainer for me & save me substantial money (plus space, fewer chargers, etc). =D

 

Bump -- any help/info on this, I'd love to know.

I think I'm to pull trigger on an Allett mower, but I really want to make it run w/ Ryobi 40V batteries & not have to invest in another battery ecosystem. My ability to do that will really depend on Greenworks battery info/specs; worst case, I guess I could buy one to take some measurements & then return it, but if someone has 1 and a multi-meter that can do some testing, it'd be super super helpful!

=D

 

I don't have one but check out this video: https://www.youtube.com/watch?v=1iixrd1NImc

I make my on Lithium batteries so can tell from skimming the vid its a 10s2p battery. That means 10 "cells" in series and two in parallel. Each cell is 3.7v nominal and 4.2v fully charged (this goes for all Li-ion cells).

The 10s means it will be 10*3.7v=37v nominal, or 42v fully charged (same as the one I just made for a 36v E-bike). Normally, this would be called a 36v battery, but manufactures like to round up. An 18v power tool battery is 5s, same with the newer 20v batts...just an fyi.

The 2p part of that 10s2p is the amp/hours. That is your runtime. This particular battery uses 2ah cells, and you add them together to get a 4ah battery. The 6ah battery version would be built the same way but with two 3ah cells, etc. You could make any size AH battery you want as long as the 10s (voltage) stays the same...the more AH the longer it will run. There is no upper limit on the AH you can use, just the voltage. Bigger is better, and you may be able to find something else more generic and cheaper with more AH. Any "36v battery" will work, whether it's Li-ion, LFP, or just 3 12v car batteries in series.

 

...I have several 18v power tool batteries that could easily power it if I connect a pair in series but there's a minor problem. It runs for about 5 seconds then cuts out. It's likely that the control wire connecting the battery to the control pcb is the issue. It runs from the pin next to the minus terminal on the trimmer to the the PCB at a point marked "COM". "...

I'm not totally following you, but I think that is the BMS board (battery management system) on the battery itself that is causing the shut down. That BMS will limit the discharge if something doesn't look right. It also makes sure the cells charge evenly, so we can't just bypass it. Some BMS's don't like to be put in series, which may be your problem with the test.. That board is also the reason most power tool batteries are useless when just one cell drops below a certain set level. If you don't have an adjustable power supply handy to test, maybe try to see if it runs on whatever three 12v lead batteries you can cobble together in series just to see if the problem is with the batts or the trimmer.

My power tools themselves don't use the "control wire" at all...I think it is just there for charging. The tools are pos and neg only. I have old drills w/o battery that I solder jumper cables on and stash in the truck...they work fine from the 12v truck battery in an emergency.

 

Thanks for the info so far folks. It could possibly be a BMS thing related to being in a Greenworks device but all the 18v batteries I have used in series in my Spear and Jackson 40v mower have performed fine , i.e the BMS' work in series in that scenario.

I'm hoping someone with a Greenworks 40 volt battery and a meter could just do a measurement and put me out of my misery
So basically - in a Greenworks 40v battery what is the resistance between the pins? I wonder if it's a capacitance or inductance or even a semiconductor thing. I could emulate all of those but a BMS data handshake is probably beyond me

Perhaps ADanto6840 will do their 'thing with a GW battery )

 

You are about to go down a rabbit hole that is probably not worth going down....https://www.eevblog.com/forum/reviews/greenworks-60v-battery-ohm-terminal/

The omega port on the GW battery seems to send a PWM signal to the tool. Adding a simple resistor or specific voltage will not work. How are your Arduino skills .

 

Hah, indeed. On Friday I pulled the trigger on the Allett Liberty.

After reading up further on the Greenworks comms, I'm not going to go down that rabbit hole; while I do have all of the required hardware & soldering skills, it's just not worth it given the relatively-high table stakes (ie the Allett Liberty), even if the risk is minimal. The risk does look minimal, and I'm pretty sure I could make it work, but it would certainly be quite a "hack" vs a quick or "clean" solution.

I'm just going to pony up and buy a 6AH Greenworks battery & charger and call it a day.

I've no issue taking some measurements for you when my Greenworks battery gets here -- that said, the documentation I've seen via reverse-engineering suggests that LawnRat is spot-on; it's a pretty deep rabbit hole, heh.