Ryobi Zero-Turn Mower SLA to LiFePo4 Conversion - (Updated - Build Complete With Pics!)

[Supervstech]

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I suppose.
I don’t care really… it will get lithium soon enough. And I will charge it with a 60A solar charge controller…
Just surprised it had only gone up 10% overnight… from 430pm to 8 am… I guess the efficiency of charging sla / agm could explain it… idk.
But with 15 ish hours of charging, id think it would be full.

 

[jberger]

You've got a low AGM battery that is pulling down the rest in the pack.
Break the group up and charge them individually then reconnect and charge with the 48V charger.
It should recharge from 50-60 in less than 12 hours, at least that's what I've seen on mine.
You also can't trust the SOC on the gauge at all, it's computed by the controller and rarely accurate.

 

[Hedges]

Oh, then there is the accuracy of SoC estimate. Maybe by voltage, not by coulombs?

Sounds like the battery may be a good size for the job, so why scrap it? Unless you've got a better application for AGM.

You've got a low AGM battery that is pulling down the rest in the pack.
Break the group up and charge them individually then reconnect and charge with the 48V charger.
It should recharge from 50-60 in less than 12 hours, at least that's what I've seen on mine.
You also can't trust the SOC on the gauge at all, it's computed by the controller and rarely accurate.

Check individual voltages.
If one is low, others in series are getting excess.
Of course, can be a low cell in one battery. But this would limit pack capacity.
Bringing all batteries individually to full charge would be good, if they are in fact different.

 

[Supervstech]

Oh, then there is the accuracy of SoC estimate. Maybe by voltage, not by coulombs?

Sounds like the battery may be a good size for the job, so why scrap it? Unless you've got a better application for AGM.



Check individual voltages.
If one is low, others in series are getting excess.
Of course, can be a low cell in one battery. But this would limit pack capacity.
Bringing all batteries individually to full charge would be good, if they are in fact different.

Cause I GOTTA!
The lead worked perfectly for the job, but I wanna give it more jobs…
I want it to be part of my shop battery bank for solar…
Make it a drive around generator too!

 

[Salmon]

Hey thanks for posting this. I'm pulling the trigger on thelis purchase soon. Been planning it for a year now, I'm only getting 20 minutes of run time.

Regarding the charger lockout bypass, I'm having an issue finding that in the thread. Could someone repost the steps or link to the post please.

Unrelated to battering power, I tested putting the crosscut blades on that they make for the 80v mower. They fit pretty well

Apologies.

However, you can work this a few ways:

1 and the simplest: Splice or bridge the Yellow and red wires coming off the lockout Circuit box (this ensures the Yellow wire is always sending the "open" voltage)..this removes the lockout function entirely.

2. Follow the path from post #589 to integrate the blue control wire with resistors

3 and most complex: Integrate the new charger into the old port, by splicing matching wires in both ends, as in post #765, this can keep the lockout function but i would only recommend if you know what you're doing, as it is destructive to the new charger.

4. You CAN simply use the old charger, it isnt recommended, but it is possible.

 

[spdickens]

*REVISED*

I'm still struggling a bit with the whole pre-charge circuit thing. I took the side cover off the mower to access where the primary contactor is located.

I have read a lot of information in regards to pre-charge circuits using contactors and such for EV vehicles which use much higher voltage battery packs and capacitors, but technically the problem still exists for these Ryobi mowers which is why my battery BMS seems to trip due to the inrush current when the motor capacitors have drained.

It seems to be fairly straightforward to install a 48v rated DC momentary switch with a resistor across the existing solenoid/contactor, hold down the momentary switch for a period of time, then turn the mower key switch to 'ON' to activate the contactor. While that appears to be a simple approach, I didn't like the idea of requiring a procedure to pre-charge the mower. Also, there is nothing to prevent someone from forgetting a step and just turning the mower key on without holding the "pre-charge" momentary switch resulting in tripping the BMS. I have been trying to figure out a more elegant solution.

I wanted to stick with the existing mower single key to turn the mower on without the need to remember to pre-charge. After doing some research it looks like a Single Pull Double Throw (SPDT) multi-function timer relay would do the trick for the timing part. If I set the timing option to a non-signaled ON-DELAY where the default switch path directed to the pre-charge circuit.

The idea is that while the mower key is in the OFF position nothing runs since the entire mower circuit is open. The SPDT timer relay is in the default position that would by default send its current through a pre-charge circuit which is just the resistor connected to the output side of the contactor. When you turn the starter key to the ON position it would close the main circuit while using the switch path for the pre-charge circuit. After a configurable time (say 5-10 seconds) the timer relay would energize and automatically switch to the activate the primary current path through the contactor. When you turn the mower key off it resets everything back to the default state.

The only caveat is that you would need to remember that there is a x-second delay until the current is switched over to the primary contactor from the timer relay. I'm thinking of adding a couple of small LED lights, one to each switch path from the timer relay, where the led light is RED when the pre-charge circuit is active and then it will turn off and activate a GREEN led on the main contactor path when the timer relay switches to the that circuit path.

I was also considering moving the battery meter/shunt Bpos wire from the battery terminal, which always causes the meter to be on, to the outbound connector of the contactor so that the monitor would only turn on only when the mower is turned on and avoid the trickle drain on the battery.

When I originally posted I was trying to avoid another switch beyond just using the timer relay plus resistor as the path for the pre-charge circuit. However, I got concerned that the timer relay coil contact switch wasn't actually rated for 48v. So I decided it was probably safer to just get another 48v ClubCar solenoid/contactor that is rated for 48v DC with an additional resistor to use for the precharge circuit. Then I adjusted the wiring for the timer relay from using the wires from the 48v switch to hooking onto the 12v wires that are used to signal the primary contactor/solenoid. It seemed to be the safest approach and keeping everything within the DC voltage specs of each component. It also allows you to just use the key to turn on the mower without any other steps than waiting a few seconds for the pre-charge to complete automatically.

I updated my original pre-charge circuit design to the attached image. I would be curious what the group thinks about this approach.

I figured worse case it doesn't work, I pick up a 48v DC momentary switch and just install that which would be the most simple. I was also struggling a bit with how to mount another contactor/solenoid for the pre-charge, the timer relay, and the pre-charge resistor. My working theory is to use an 8" slotted stainless steel mender "sandwiched" between the original contactor and its mounting bracket. Then I can mount the pre-charge solenoid to the extended part of that mender. The slots give me flexibility to shift things around. I'm thinking of using a few other strips of the slotted menders to act as "hangers" off the horizontal mender so that I can mount the timer relay and pre-charge resistor below the pre-charge solenoid/contactor. This should give me some flexibility to shift things around without trying to fabricate a mounting plate of some kind.

I'm going to try to test this out when I get all the parts in this week. If it works, I'll post final pictures.

A question: Has anyone managed to replace the ryobi charge port with an Anderson plug and been able to retain the lockout function?

I bought a 25A charger, so needed to replace the charge port and wiring with something that can handle the greater amps, and I've read of people disabling the lockout function by connecting the blue wire back to the battery positive, but not of anyone retaining the lockout function after replacing the original charge port.

I suppose I'll disable it if I need to, but I'd prefer to keep it if possible - one less thing to think about.

Thanks Voltman. What type of switch do I purchase (I assume SPST)? What volt or amp rating does it need? Can it be lighted? Thanks!

 

[spdickens]

Hi juiceman, here's some photos of my precharge circuit. It's a bit hard to follow the wires, but basically it goes from one side of the contactor to a momentary switch - mine is located just next to the key switch to help me not forget - to a resistor - I used a 270ohm one, I'm holding it at the bottom of the photo - back to the other side of the contactor. I used ring terminals placed above the primary ring terminals of the contactor. Hope that helps.

Sorry to be a bit dense about this, just confirming, is my picture below a correct interpretation? Thanks, Steve

 

[kdubbya]

Hey all just thought I'd post that the chins 48v 100ahr, 500amp max current battery works as a drop in, no precharge circuit. Got it installed today. Curious though I'm using the tr16h off Amazon and it reads voltage but 1) doesn't seem to acknowledge me setting it to 100ahr as the full charge state since it still shows 0% after I program it 2) it doesn't shut off with the key? Did I miss wiring it to the ignition switch somewhere? Watched a lot of videos and never saw that. Any help is appreciated. Thanks!

 

[Supervstech]

Hey all just thought I'd post that the chins 48v 100ahr, 500amp max current battery works as a drop in, no precharge circuit. Got it installed today. Curious though I'm using the tr16h off Amazon and it reads voltage but 1) doesn't seem to acknowledge me setting it to 100ahr as the full charge state since it still shows 0% after I program it 2) it doesn't shut off with the key? Did I miss wiring it to the ignition switch somewhere? Watched a lot of videos and never saw that. Any help is appreciated. Thanks!

Well, sure, you wouldn't need a precharge circuit if the key never shuts off the battery...

 

[kdubbya]

Well, sure, you wouldn't need a precharge circuit if the key never shuts off the battery...

Fair point. I meant that in terms of the in rush current.

 

[kdubbya]

Well, sure, you wouldn't need a precharge circuit if the key never shuts off the battery...

Got it figured out. Just pulling the voltage read from a better spot that has ignition shutoff. Thanks all the good info on the forum.

 

[noride]

@kdubbya It might be helpful to list your mower model for future visitors to this thread. I think at least one other person used the same battery and ended up needing a pre-charge bypass.
As an aside, I am still waiting for a free weekend to give my conversion a shot. Cautiously optimistic.

 

[kdubbya]

@kdubbya It might be helpful to list your mower model for future visitors to this thread. I think at least one other person used the same battery and ended up needing a pre-charge bypass.
As an aside, I am still waiting for a free weekend to give my conversion a shot. Cautiously optimistic.

@noride good catch. I have the 54in deck ryobi zt540e, model # RY48140. Interesting I just mowed my yard yesterday and it works perfectly. I shut it down multiple times during and it came on just fine. Their are two different versions of that chins 48v on Amazon and one in particular lists the 500amp surge rating.

CHINS Bluetooth LiFePO4 Battery Smart 48V 100AH Lithium Battery Perfect for Golf Cart, Trolling Motor, Marine, Peak Current 500A, Mobile Phone APP Monitors Battery SOC Data https://a.co/d/h4vM7pL

 

[noride]

That's really interesting, thanks for sharing. I think @Salmon noted there may also be a 300amp rated version of the Chin 48v floating around, or perhaps the last person simply got a more sensitive BMS. Either way, congrats on your success!

 

[kdubbya]

That's really interesting, thanks for sharing. I think @Salmon noted there may also be a 300amp rated version of the Chin 48v floating around, or perhaps the last person simply got a more sensitive BMS. Either way, congrats on your success!

@noride you're correct. I actually bought from the reference that @Salmon posted originally and with some helpful dm's from him directly. He pointed out that there were some documentation discrepancies about the surge figure. I couldn't access the chins website for whatever reason but decided to roll the dice and return it if it wasn't a drop in success but it works well. I also used the charger linked below. It was simple enough to remove the triangle ezgo from the ryobi charger and place it on this one, though it doesn't have a ground terminal like the ryobi one does. A good youtuber video did the same thing and resolved that you can either swap the heads or file down a port in the charger receptacle on the mower.

HTRC 36V and 48V Golf cart Charger 18-Amp Smart Charger, Car Battery Charger,Trickle Charger,36V18Amp/48V13Amp ,Lithium,LiFePO4,Lead-Acid AGM/Gel/SLA.. Battery Charger, for EZGO RXV & TXT,Car, Boat.. https://a.co/d/1HMwzi2

 

[noride]

I finally got mine done, fired up with no issues! So glad I waited and didn't monkey with a bypass.

ZT480ex
Batteries: https://www.amazon.com/dp/B09JNK13YH
Charger: https://www.amazon.com/dp/B0BKZ2R94T

Installation notes:

Batteries.
1. These batteries are a little tall, so do yourself a favor a remove the plastic runners that help the battery sled slide in. This will net you a few precious mm, and they aren't really necessary anymore with the weight reduction. I also cut the old plastic battery covers to fit within the interior of the top mounting bar, which also gets you a little more room, while putting the bar in direct contact with the battery top, which I liked. I used silicone tape to help prevent slippage.

2. They are also a little smaller in width and length. I used some heavy duty double sided sticky tape on the bottom of the batteries, in addition to some wedges I cut, to keep everything snuggly in place. I also added some washers to the back plate on the battery sled to shorten the length a tiny bit.

Charger.
1. Stock charger worked fine without modification, but is not ideal for this battery chemistry.

2. I chose to Dremel the plastic stoppers in the charging port so I could use standard chargers unmodified going forward, while keeping the original complete for resale.

3. You can instead remove the plastic handle from your old charger and swap it with the new one (so I've read), or purchase one aftermarket and perhaps do a little soldering instead.

General.
1. I used a drill instead of an impact driver to remove the body work and I seriously regret that choice. Probably should just do it by hand, the tabs were very fussy.

2. Pay attention to what you're doing or things will get super spicy super fast. Had a short while building the pack, no harm done though, thankfully.

3. The mower handles differently with the weight reduction! Be cautious for a bit. People have commented on the increase in speed, but the biggest surprise for me is how it doesn't slow down up steep hills anymore, it just charges up like they're nothing. I actually think with a full bagger it could be problematic.

Anyhow, I haven't installed the gauge yet, that's something I'll have to tackle down the road. For now I'll just recharge after each mow, the charger has an approximation that should work well enough.

Thanks again for all of the help everyone, especially @Julie EVD !

 

[Julie EVD]

You're not having any problems with inrush current with those batteries? I didn't see in thr description where it said they could handle anything over 100amps for any period of time. Just curious! Tha

You're not having any problems with inrush current with those batteries? I didn't see in thr description where it said they could handle anything over 100amps for any period of time. Just curious! Thanks.

It seems to have no problems. @noride retrofitted his as well, and has had no issues. He did a few things differently, but his result is the same.

 

[Julie EVD]

I finally got mine done, fired up with no issues! So glad I waited and didn't monkey with a bypass.

ZT480ex
Batteries: https://www.amazon.com/dp/B09JNK13YH
Charger: https://www.amazon.com/dp/B0BKZ2R94T

Installation notes:

Batteries.
1. These batteries are a little tall, so do yourself a favor a remove the plastic runners that help the battery sled slide in. This will net you a few precious mm, and they aren't really necessary anymore with the weight reduction. I also cut the old plastic battery covers to fit within the interior of the top mounting bar, which also gets you a little more room, while putting the bar in direct contact with the battery top, which I liked. I used silicone tape to help prevent slippage.

2. They are also a little smaller in width and length. I used some heavy duty double sided sticky tape on the bottom of the batteries, in addition to some wedges I cut, to keep everything snuggly in place. I also added some washers to the back plate on the battery sled to shorten the length a tiny bit.

Charger.
1. Stock charger worked fine without modification, but is not ideal for this battery chemistry.

2. I chose to Dremel the plastic stoppers in the charging port so I could use standard chargers unmodified going forward, while keeping the original complete for resale.

3. You can instead remove the plastic handle from your old charger and swap it with the new one (so I've read), or purchase one aftermarket and perhaps do a little soldering instead.

General.
1. I used a drill instead of an impact driver to remove the body work and I seriously regret that choice. Probably should just do it by hand, the tabs were very fussy.

2. Pay attention to what you're doing or things will get super spicy super fast. Had a short while building the pack, no harm done though, thankfully.

3. The mower handles differently with the weight reduction! Be cautious for a bit. People have commented on the increase in speed, but the biggest surprise for me is how it doesn't slow down up steep hills anymore, it just charges up like they're nothing. I actually think with a full bagger it could be problematic.

Anyhow, I haven't installed the gauge yet, that's something I'll have to tackle down the road. For now I'll just recharge after each mow, the charger has an approximation that should work well enough.

Thanks again for all of the help everyone, especially @Julie EVD !

I"ve also noticed that the mower seems to do a better job with the cut. Maybe the blades run a bit faster? I don't know, but I'm really happy.

 

[Salmon]

I"ve also noticed that the mower seems to do a better job with the cut. Maybe the blades run a bit faster? I don't know, but I'm really happy.

To explain this (at least to my limited knowledge)

The blades don't run any "faster" per se, the power to them is managed by capacitor banks in each motor controller (which are also responsible for the inrush current)

What happens if throughout the mow, the LiFePo4 batteries keep the capacitor banks energized more efficiently throughout their state of charge at a consistent ~52V where the stock SLA or AGM would slowly lose Voltage as their state of charge declined, and became less and less efficient at keeping the capacitors energized and in worst cases motors would simply lose power.

 

[noride]

To explain this (at least to my limited knowledge)

The blades don't run any "faster" per se, the power to them is managed by capacitor banks in each motor controller (which are also responsible for the inrush current)

What happens if throughout the mow, the LiFePo4 batteries keep the capacitor banks energized more efficiently throughout their state of charge at a consistent ~52V where the stock SLA or AGM would slowly lose Voltage as their state of charge declined, and became less and less efficient at keeping the capacitors energized and in worst cases motors would simply lose power.

They definitely don't bog down in high grass anymore, that's for sure. Just turned 10" of overgrowth into absolute pulp.

I assumed it was because SLA batteries are prone to voltage sag during load changes. More or less in line with your assessment, regardless.

 

[hectorspencer]

@noride you're correct. I actually bought from the reference that @Salmon posted originally and with some helpful dm's from him directly. He pointed out that there were some documentation discrepancies about the surge figure. I couldn't access the chins website for whatever reason but decided to roll the dice and return it if it wasn't a drop in success but it works well. I also used the charger linked below. It was simple enough to remove the triangle ezgo from the ryobi charger and place it on this one, though it doesn't have a ground terminal like the ryobi one does. A good youtuber video did the same thing and resolved that you can either swap the heads or file down a port in the charger receptacle on the mower.

HTRC 36V and 48V Golf cart Charger 18-Amp Smart Charger, Car Battery Charger,Trickle Charger,36V18Amp/48V13Amp ,Lithium,LiFePO4,Lead-Acid AGM/Gel/SLA.. Battery Charger, for EZGO RXV & TXT,Car, Boat.. https://a.co/d/1HMwzi2

This is really great information, thank you! I also have the RY48140. My SLA batteries have some life left but I've been preparing for the eventual conversion. Your success with the Chins as a drop in replacement is great news. I'll definitely be considering that battery and the charger you bought for my conversion. Would you mind sharing that YouTube video you mentioned regarding the charger and the plug?

 

[kdubbya]

@hectorspencer

 

[MowerConversion]

@noride good catch. I have the 54in deck ryobi zt540e, model # RY48140. Interesting I just mowed my yard yesterday and it works perfectly. I shut it down multiple times during and it came on just fine. Their are two different versions of that chins 48v on Amazon and one in particular lists the 500amp surge rating.

CHINS Bluetooth LiFePO4 Battery Smart 48V 100AH Lithium Battery Perfect for Golf Cart, Trolling Motor, Marine, Peak Current 500A, Mobile Phone APP Monitors Battery SOC Data https://a.co/d/h4vM7pL

Nice! So it seems like we’ve got two real drop in replacements for the 54” RY48140 between the chins and vatrer. I don’t see how the vatrer is worth the extra $700+, though, maybe I’m missing something

 

[kdubbya]

Litime also makes 12v/100ah Trolling Motor options that will support that in rush current. That was per the reps I emailed with but never tested that myself.

 

[Supervstech]

Litime also makes 12v/100ah Trolling Motor options that will support that in rush current. That was per the reps I emailed with but never tested that myself.

And will just did a review video on them.
300A for 5 seconds, plus it has low temp disconnect.