A little help with bypassing battery thingy on 40v Ryobi lawnmower.

Thread Starter

ayden2007

Joined Jun 11, 2024
8
can anyone help me figure out how to run a Ryobi 36V lawnmower with a 36v scooter battery?

problem is that the contact plate (has a third orange 22ga wire) has more than 2 wires to it. I’ve heard this has something to do with temperature… how can I bypass this and get this mower to run with a 36v larger capacity scooter battery?

Seems this small wire needs to provide some sort of information to the motor controller. Tried looking for the data sheet on the controller (PM177-20A-01) but no luck.


Thanks guys for any help you can throw my way.

IMG_6726.png
 

Dodgydave

Joined Jun 22, 2012
11,375
On the original battery, can you measure the resistance of the third terminal to one of the other terminals, it should read in ohms..they usually are a thermistor to sense heating.
 

MisterBill2

Joined Jan 23, 2018
19,474
and after you measure the resistance on the original battery then you can fake it with a similar resistance between the yellow wire and which ever it showed the resistance to, on the replacement battery.
 

Thread Starter

ayden2007

Joined Jun 11, 2024
8
Thanks guys - I'm measuring 20kohms from the negative terminal of the battery to the pin connecting to the orange wire. While I'm reading 40V from the orange pin to the positive battery terminal. I'll try placing a 20k resistor and see what happens. Give you an update when that happens. Again thanks for your help :)
 

Tonyr1084

Joined Sep 24, 2015
8,006
Thermal sensing is there for a reason. Bypassing the sensor may prove problematic. And lawn mowers are not cheap. Do you want to risk damaging a machine that can cost hundreds of dollars to replace?
 

MisterBill2

Joined Jan 23, 2018
19,474
A battery overheats because of excess current, either charge, discharge, or internal failure. And the temperature sensor is INSIDE the battery pack TO PROTECT THE BATTERY. So it is not risking damage to the mower.
 

Thread Starter

ayden2007

Joined Jun 11, 2024
8
A battery overheats because of excess current, either charge, discharge, or internal failure. And the temperature sensor is INSIDE the battery pack TO PROTECT THE BATTERY. So it is not risking damage to the mower.
I've built a 30Ah lifepo4 battery to replace the 5Ah Ryobi battery. Hoping I can mow much longer. The 12s BMS on the battery monitors the battery temp so hoping that'll shut down if it gets too hot.

Build cost less than a new Ryobi battery.

Will update when tested.
 

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Thread Starter

ayden2007

Joined Jun 11, 2024
8
Thermal sensing is there for a reason. Bypassing the sensor may prove problematic. And lawn mowers are not cheap. Do you want to risk damaging a machine that can cost hundreds of dollars to replace?
Here in the Philippines we have a surplus of these second hand electric mowers from Australia - easily pick one up for less than $50 but the catch is the battery that comes with it is usually hooped.
 

MisterBill2

Joined Jan 23, 2018
19,474
Another possible choice could be creating a mains powered supply for the motor. I use plug-in electric mowers, which provide the major benefit of never needing a battery charge or the expensive battery replacement. AND, in my part of the world, the rechargeable battery MUST be protected from freezing, so storage in an unheated area is required.
And while I have worn out a few electric mowers, I have never cut a power cord with a mower, which is the common complaint about them from many folks. So a sitcher supply could certainly be an option.
 

ulms

Joined Mar 19, 2024
58
Do you remember when we were kids, how toys that needed batteries sucked! Well today unfortunately that has passed through into adulthood and things that need batteries still suck.
 

Tonyr1084

Joined Sep 24, 2015
8,006
Do you remember when we were kids, how toys that needed batteries sucked! Well today unfortunately that has passed through into adulthood and things that need batteries still suck.
Just bought one of these:
https://www.lowes.com/pd/Kobalt-7-in-3-Speed-Indoor-Outdoor-Misting-Stand-Fan/1003002600'
What sucks (to me) is that batteries are manufacturer specific. I have a lot of DeWALT tools and batteries. The Kobalt fan can't take a DW battery, won't fit. I'm thinking about making a dock for the DW battery and wire it to a pseudo-Kobalt battery so I can plug my DW's into this rig and connect it to the fan. Yes, the fan is 24V and my DW batteries are 20V. I don't think there will be much of a problem there since each battery has its own BMS. The fan consists of a - um - Fan; and a pump. Low voltage will just mean the fan won't blow quite as hard and the pump won't produce as much pressure. But the fan and pump are both 3 speed settings. So a lower voltage means I might run it on Medium instead of Low.
 

Thread Starter

ayden2007

Joined Jun 11, 2024
8
Just bought one of these:
https://www.lowes.com/pd/Kobalt-7-in-3-Speed-Indoor-Outdoor-Misting-Stand-Fan/1003002600'
What sucks (to me) is that batteries are manufacturer specific. I have a lot of DeWALT tools and batteries. The Kobalt fan can't take a DW battery, won't fit. I'm thinking about making a dock for the DW battery and wire it to a pseudo-Kobalt battery so I can plug my DW's into this rig and connect it to the fan. Yes, the fan is 24V and my DW batteries are 20V. I don't think there will be much of a problem there since each battery has its own BMS. The fan consists of a - um - Fan; and a pump. Low voltage will just mean the fan won't blow quite as hard and the pump won't produce as much pressure. But the fan and pump are both 3 speed settings. So a lower voltage means I might run it on Medium instead of Low.
I'm pretty sure you can find adaptors for these... https://www.ebay.com/itm/284768060332
 
Do you remember when we were kids, how toys that needed batteries sucked! Well today unfortunately that has passed through into adulthood and things that need batteries still suck.
Consider that EVERY BATTERY POWERED DEVICE is going to require a battery replacement before it wears out, unless it is very poor quality, AND that the price of those replacement battery packs, which are absolutely designed to be non-interchangeable, will run from a quarter to a half of the price of the whole tool. Also, consider that those rechargeable battery packs MUST be protected from freezing. That means not staying in a unheated garage all winter.
My plug-in electric mowers and leaf blower and string trimmer suffer no such limitations.
 

Tonyr1084

Joined Sep 24, 2015
8,006
OK, just did a bench test using some jumpers. Wire gauge is not a factor in performance.
Kobalt Fan & Battery
K1 (Low) Good
K2 (Medium) Better
K3 (High) Best

Kobalt Fan & DW battery
DW1 (Low) Good enough
DW2 (Medium) Better still but not as good as K2
DW3 (High) Approximately the equivalent of K2

In other words, High on DW Battery is about equal to K Battery on Medium.

At this point it doesn't seem worth pursuing. Not unless I want to get hands on some 12V SLA's in series with sufficient amperage. Two of THESE will cost $108 (approx). Whereas THIS set, which fits and no need for mod's. Just a buck more.

Two of THESE cost about $80 for 7AH of power.
 

Tonyr1084

Joined Sep 24, 2015
8,006
Just realizing I am hijacking this thread. Sorry. At this point I don't have a need to start a new thread. I will delete post #19 in a bit.

Post #19 said:
OK, just did a bench test using some jumpers. Wire gauge is not a factor in performance.
Kobalt Fan & Battery
K1 (Low) Good
K2 (Medium) Better
K3 (High) Best

Kobalt Fan & DW battery
DW1 (Low) Good enough
DW2 (Medium) Better still but not as good as K2
DW3 (High) Approximately the equivalent of K2

In other words, High on DW Battery is about equal to K Battery on Medium.

At this point it doesn't seem worth pursuing. Not unless I want to get hands on some 12V SLA's in series with sufficient amperage. Two of THESE will cost $108 (approx). Whereas THIS set, which fits and no need for mod's. Just a buck more.

Two of THESE cost about $80 for 7AH of power.
Again, my apologies.
 
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