Assistance with Ryobi 48v mower conversion

Onecaribou

10 µW
Joined
Oct 16, 2012
Messages
6
Hi All,

I'm attempting to convert my Ryobi RY14110 48v SLA mower to Lipo. The stock mower runs off 2-24v 10Ah Lead acid batteries and though the SLA pack sags terribly, the mower is in working condition. Unfortunately, I'm having trouble figuring out why the mower won't start.

I've gone ahead and purchased two Turnigy nano-tech 5000mah 6S high discharge batteries and wired them in as shown below. I've checked my wiring and the fuses and all appear to be OK.

I'm hoping someone could point me in the right direction before I tear the mower down and trace it with a voltmeter.

Conversion:
mower_conversion.jpg


Original Wiring:
mower_original.jpg



For what it's worth I have checked out some similar conversion threads for the same model but they have't shed much light on the issue.

https://www.endless-sphere.com/forums/viewtopic.php?f=1&t=52108&p=792645
https://www.endless-sphere.com/forums/viewtopic.php?f=14&t=53275&p=794083#p794083
http://endless-sphere.com/forums/viewtopic.php?f=1&t=37250


I intend to put a couple voltage monitors and add another two packs in parallel once I get the current configuration working.

Thanks!
 
Well, the first thing I'd do is stick that little capacity meter on the input to the system, instead of in the old SLA pack. Then you could press and hold it's little test button *while* you are starting the motor, to see if the voltage sag is too much, and why it doesn't start.

However, it looks like it's original wiring only has a meter on *one* of the SLA, not the other, which is pretty strange (unless the charger puts them in parallel, while the mower puts them in series, which is the only reason I can think of for the 4-pin connector vs 2 or 3). That means it's only a "24v" meter, not a "48V". So if you do use it, you can only use it on one pack at a time.


That said, if there is no circuitry in the mower itself other than the motor, switch, circuit breaker, and that resistor (which I'm not sure I understand the purpose of, but there must be a good reason for it or they wouldn't have spent money puttting it in there), then it should spin at least a little bit with no load on it even if your batteries were not high enough voltage (due to sag or whatever).


So, since the connector itself on the input to the mower has that little shorting bar, and you're using it to connect your two pack halves together in series, why don't you bypass that and leave them in series all the time? Then you'll know for sure it's not a connection issue there. (probably isn't, if hte same connector worked with the SLA). The only reason it's even there is probalby as I am guessing above, for it to turn the SLA into series cells where they are parallel during charging.



Now, SLA can put out a heckuva lot of current even when they are sagging down to "dead" voltages. Normally so can RC LiPo, but perhaps yours have a problem?


Does the mower still work on its SLA now that youv'e tried the LiPo? If not, then a fuse has probably blown somewhere, or a brush burned. If it does still work on that, then you can eliminate antyhing that you havent' changed or added when the SLA are not present.
 
amberwolf said:
Well, the first thing I'd do is stick that little capacity meter on the input to the system, instead of in the old SLA pack. Then you could press and hold it's little test button *while* you are starting the motor, to see if the voltage sag is too much, and why it doesn't start.


I actually half heatedly connected the capacity meter to the terminals of one of the batteries after I finished up installing everything in the mower pack but I wasn't able to get any reading off it. I figured it was an issue with the differing battery chemistries.. which in retrospect was a silly thought. This makes me wonder if I'm grounding out the terminals somewhere. The ring terminals I am using are slightly larger in diameter to the stock ones and I when I checked this morning it looked like one was touching a screw used to attach the terminal block to the battery box.

amberwolf said:
However, it looks like it's original wiring only has a meter on *one* of the SLA, not the other, which is pretty strange (unless the charger puts them in
parallel, while the mower puts them in series, which is the only reason I can think of for the 4-pin connector vs 2 or 3). That means it's only a "24v" meter, not a "48V". So if you do use it, you can only use it on one pack at a time.

I also saw this. Pretty odd. I was thinking about just buying a couple Cell-Log 8 and mounting them to the outside of the battery box longer term.

amberwolf said:
That said, if there is no circuitry in the mower itself other than the motor, switch, circuit breaker, and that resistor (which I'm not sure I understand the purpose of, but there must be a good reason for it or they wouldn't have spent money puttting it in there), then it should spin at least a little bit with no load on it even if your batteries were not high enough voltage (due to sag or whatever).

I believe I read that the resistor was there to help the mower spin down the blade once power is disconnected.

amberwolf said:
So, since the connector itself on the input to the mower has that little shorting bar, and you're using it to connect your two pack halves together in series, why don't you bypass that and leave them in series all the time? Then you'll know for sure it's not a connection issue there. (probably isn't, if hte same connector worked with the SLA). The only reason it's even there is probalby as I am guessing above, for it to turn the SLA into series cells where they are parallel during charging.

Great idea!

Any thoughts on how I should wire them? If you can't tell I'm a novice when it comes to wiring/battery tech.

Option 1-
serial_config1.jpg


Option 2 -
serial_config2.jpg


amberwolf said:
Now, SLA can put out a heckuva lot of current even when they are sagging down to "dead" voltages. Normally so can RC LiPo, but perhaps yours have a problem?

You could certainly be right but these were just delivered yesterday and the extent of their service life is just an initial balance charge.

amberwolf said:
Does the mower still work on its SLA now that youv'e tried the LiPo? If not, then a fuse has probably blown somewhere, or a brush burned. If it does still work on that, then you can eliminate antyhing that you havent' changed or added when the SLA are not present.

The SLA battery pack, now that it's disassembled is truly a bit disconcerting - it's bulging and distended and you can see where liquid has splashed out... so I'm a little terrified to plug it back in. That said, my brother has the same model and I'll see if I can borrow one of his SLA batteries.

I'm going to revisit all of this when I get home tonight. Thanks for your assistance amberwolf!
 
Be Extremely Careful When Testing A Mower!!!

Do this motor test: Charge the lipos and bypass everything with jumper wires. Go directly from the batteries to the motor to see if the motor spins up. If it doesn't spin then it is probably the motor. (although it may want 48v not 44v)

If it does spin up work backwards through the wiring.

First leave the negative connected to the motor and connect the positive lead before the switch to test the switch. If that works then work backwards through the connectors ect.

:D
 
e-beach said:
Be Extremely Careful When Testing A Mower!!!
Note that when I have to work on a mower electrically or mechanically, first I make sure the power source is disconnected from it, then I take the blade off, and then do the work (whcih may include connecting it to a power source and running it).

Onecaribou said:
I actually half heatedly connected the capacity meter to the terminals of one of the batteries after I finished up installing everything in the mower pack but I wasn't able to get any reading off it.
If there was no reading at all, but it *does* work on the SLA, then you are getting no voltage at the terminals it was connected to, for whatever reason.

So you should start from that point, and check backwards to the battery itself from there, with a multimeter on DC Volts, range of 200 (because they shoudl be higher than 20V).

When you find the spot on one side of which you get the correct voltage reading from + of the pack output to - of the pack output, and the other side of which you don't, you've found the connection problem and can go from there.



This makes me wonder if I'm grounding out the terminals somewhere. The ring terminals I am using are slightly larger in diameter to the stock ones and I when I checked this morning it looked like one was touching a screw used to attach the terminal block to the battery box.
If you had a problem with a short, you would have known about it instantly when you connected it because there would ahve been a huge spark and vaporized metal. ;) See "KFF" in the wiki or on a google search of ES. :lol:

IF you were lucky it would jsut ahve instantly blown any fuse in series with the pack in question.

I believe I read that the resistor was there to help the mower spin down the blade once power is disconnected.

That makes sense. LIke the mechanical blade brakes the gas engine ones I've fixed before have. (and the B&D plugin electric I use now)


Any thoughts on how I should wire them? If you can't tell I'm a novice when it comes to wiring/battery tech.
Neither way in the Option# sketches is correct. #1 only gets you half the voltage, and in reverse. #2 gets you lots of pretty sparks and fire. (assuming your red and black = the red and black on the packs)


You need to wire it exactly like the original. So you would jsut put that short between the packs (+ of teh most negative, bottom pack to - of the most positive, top pack) directly between them, inside the battery case, rather than make the case-to-mower connector itself do the work for you.

So...being more clear, you'd connect the red wire from the bottom battery to the black wire of the top battery.

Then the black wire of the bottom battery goes to teh - of the mower.

Then the red wire of the top battery goes to teh + of the mower.

You could certainly be right but these were just delivered yesterday and the extent of their service life is just an initial balance charge.
Unfortunatley with hobby lipo that doesnt' mean anything at all. :( Defective brand-new packs are common occurence, for a number of reasons. SInce they passed your first charge, it's unlikely they are bad, but until you test them on discharge with a load, you can't know for sure.



The SLA battery pack, now that it's disassembled is truly a bit disconcerting - it's bulging and distended and you can see where liquid has splashed out... so I'm a little terrified to plug it back in. That said, my brother has the same model and I'll see if I can borrow one of his SLA batteries.
[/quote]
It's normal for SLA to age and fail like that...but if it still worked before taking them out, then they are safe enough to use for one test. Just use rubber gloves to handle them so you don't get any acid gel on your hands.
 
That last diagram looks like it's wired in parallel and not series. You've got two reds going to one connection and two blacks going to the other. You're supposed to have the batteries - out, + to -, + out for a series connection to get 48V.
 
This is how it should be wired. I would cut the yellow resistor wire if it starts getting hot

roybe mower .jpg
 
Also, you will need a volt meter attached where you can see it when you are using your mower so you know your depth of discharge while running the mower. If you discharge your lipo batteries beyond 3v per cell you could kill your battery. (3 x 12 = 36v)
 
The diagram provided by ebeach and described by amberwolf worked perfectly. I was able to clean up the wiring and she's running great. Thanks guys!

About the same power as with SLA and seemingly with more run time - down only 20% after a 15 minute test mow.

I'll be adding a couple voltage monitors and possibly on-board charging.. but that'll be another thread.

Here's the video of the first run. Turn your volume down or my EV Grin might frighten you.
https://www.youtube.com/watch?v=po6AdapvFe8



Embedding seems to be misbehaving..
[youtube]po6AdapvFe8[/youtube]
 
You should keep your whole project in this thread, so people later on looking around don't have to find all your threads just to see how to do it themselves. :wink:


Plus, anyone helping you now may not even know you need help in the other thread--but any new posts you make in this one they'll see.
 
amberwolf said:
You should keep your whole project in this thread, so people later on looking around don't have to find all your threads just to see how to do it themselves. :wink:


Plus, anyone helping you now may not even know you need help in the other thread--but any new posts you make in this one they'll see.

Will do

Thanks again for your help!
 
Hi,
This thread was helpful. I removed the yellow wire which does the safety stop. Was the recommended to prevent damage to the battery, or just to save juice? Anyhow, I did this back in May, and simply used a 40v Ryobi battery http://www.homedepot.com/p/Ryobi-40...Qjm7ch4xJsQjuhtZd3G28aAjV88P8HAQ&gclsrc=aw.ds that came with my weedeater. Works fine, but takes about 2-3 charges to do my lawn (lot is 0.44 acre). It got me through the season without any additional cost. It is 2.4 amp hours. I'll try to find a 48v 7.5+ ah battery over the winter.
 
robertinmilford said:
Onecaribou, its been awhile, but how well has your battery set up worked?

It's held up really well. I'm surprised at how well actually since I never did install battery monitors.

Eventually I'll be adding an additional pair of batteries ( in parallel) for a more run time, battery monitors and an onboard charging solution. For now though, I can finish my lot just fine unless I've been negligent and let it grow too high or if it's wet from a recent rain. The mower is coming up on 5 years old runs great and the batteries still charge up to their initial specs.
 
I just recently got a used mower with bulging SLA. Ripped out the SLA, the circuit that tells the battery level, charging plug and all the wires except for one positive (far left out and far right looking from the back). I used the positive wire with the 60amp fuse to have some sort of protection I guess.

I connected 6x4s 5800mAh RC (12S2P = 44.4V @3.7V each 11600mAh) lipo packs giving me about the same power and capacity as the original SLA.

However, I have a question about the amp draw requirement for these mower. I also have 13S3P 18650 (10500mAh) pack I used for my ebike. It has a 30A BMS installed on the battery. When I plug into the mower, the mower would just blip a bit of power and just stop. It does not power up and maintain power like the 12S2P RC that runs without BMS.

Is there a really high current draw to start these mowers up? Is that why the BMS protected pack would not work?

I am asking since I am tired of charging 6 RC packs to individually and would like to install a BMS to make charging simpler on these RC packs.

Any ideas?
 
A motor can have a huge startup spike, hundreds of amps or more, especially if it is a brushed motor with no controller, just on/off switch, as the switch is closed to turn it on. If you have a wattmeter you could try using that to see what it captures for peak readings.

There is also inductive kickback from the motor directly to the battery as the switch is opened to turn it off, which can create very high voltage spikes.

So a BMS can actually be destroyed by this, and will usually shutdown for overcurrent protection if not.


To prevent this you would need to install a controller on the motor, so the controller helps protect the BMS from this startup spike, by letting you turn the motor on more slowly (with a throttle instead of jsut a switch).

But the controller itself has to be able to handle the startup spikes of the motor, too, and whatever it's loaded current is (presumably under 60A, since that's what that fuse is rated for).
 
Thank you very much amberwolf.

I suspect the amp draw is higher than what the BMS is giving. However, I think your theory about the kickback high voltage spikes may be the issue since the BMS can go as high as 50A if needed but only as peak.

Guess the only way I can use BMS is to install a controller which is a long term project over the winter. I just need to use the mower during grass cutting season. Saying that, the pack 11600mAh pack may be better/longer capactiy than the 10Ah SLA. The pack was not full since i used it in the ebike a bit before moving it over to the mower. I started with about 46.2V and after going through the yard the reading drop to 45.5V. So I can pretty much only need to charge it every month if I cut twice maybe three times a month.
 
Hi,

I was wonder if something like this would allow the control of amp draw and induction kickback protection against the BMS and will still allow the mower to spin at full speed?

[img=https://ae01.alicdn.com/kf/HTB1xJdPlAOWBuNjSsppq6xPgpXaY/pwm-speed-electronic-40A-DC12V-24V-36V-48V-Brushed-motor-controller-Maximum-Power-of-2000W-Third.jpg][/img]
40A 48V Brushed motor controller (2000W)

I would have to rig a better throttle bar since I will more than like have to start it at low speed and then slowly crank it up to mow. More effort than just turn on the safety and just mow. But if it will allow better BMS action.

What do you think?
 
If the motor did not have a controller before, and was simply switched on/off by the handle, then a controller with a throttle will allow you to control the startup surges, etc. (keeping in mind that if you start it up in the middle of high grass or other highly loaded situation, it will still draw a lot of current trying to speed up).

That should prevent the problems affecting a BMS/etc that simply switching the motor on and off create.



If the motor already has a controller, then unless you are replacing that with the new one, I don't know how (or if) it will work.
 
The Ryobi motor circuit uses 18AWG wire, which has a current carrying capacity of about 10A. The circuitry also has a 15A breaker. So this would indicate that if the current to the motor exceeded 15 amps, the breaker would open the circuit. There is also a large "0.5R" 50W resistor in parallel to the motor which I believe is a braking mechanism for when power is removed from the motor - the resistor dissipates the energy being generated by the still spinning DC motor. It is also using some power from the battery when the mower is running, so it reduces efficiency.

The Ryobi lead-acid battery pack uses 14AWG wire, which has a current carrying capacity of about 25A, and for the charging circuit, 18AWG. The battery pack also has two 60A fuses as a fail safe measure in case of a short circuit I presume.

The Lipo battery packs the poster is using are rated at 40C, and their capacity is 5000mAh each. So they each have a safe sustained current draw of 40 x 5A or 200A. They are also rated at a peak of 80C (for 10 seconds), or a 400A current draw. So it would seem that their safe current draw would not be exceeded by the Ryobi mower.

Assuming a maximum 10A running current, and 5000mAh battery capacity, and not want to fully discharge the Lipo batteries, one could probably mow for 1/2 hour. So for a small yard, that is probably adequate. Assuming 100 to 300 charge cycles, perhaps they will last 2 to 6 years of mowing. That could be the same or better than the original lead acid battery packs which one can still buy from Home Depot for about $130.00.

Of course, those lead acid batteries are very heavy. They don't seem to do well unless stored indoors fully charged over the winter, and checked frequently to top-off. The charger will gladly over-charge them as well.

I have this Mower which I bought in 2010 for just under $400. With the first battery pack I did what the manual said and left it connected to the charger all the time, assuming it was a battery maintainer type of charger. So one day I found the battery case puffed out and leaking, and it was a few days after the 1 year warranty had expired. I was more careful with the next battery pack. But even so, it failed to hold a charge within a year - this time before the warranty had expired. I took it to Home Depot and the manager gave me the battery pack from one they had on display, which is the one I have had since June 2012, almost 9 years. It still powers the mower, but I don;t get much more than 15 minutes out of it and don't use the powered wheel drive to save energy. And it takes a lot of babying.

So I think I am going to try the Lipo substitution and see how that goes. I am buying a balance charger/discharger so I can get a much lifespan out of the Lipo's as possible. I am going to cushion them to avoid the shock that could come from hitting bump in the yard. I found an XT90 series connector and will use that with a pigtail on which I have installed female bullet connectors that will fit on the pins the original batter pack used (just the two end pins).

I'll post a follow up after I've done the transformation.
IMG_2524.JPG
 
amberwolf said:
There is also inductive kickback from the motor directly to the battery as the switch is opened to turn it off, which can create very high voltage spikes.

In the Ryobi, the motor is disconnected completely from the battery pack when the switch is opened, and there is a resistor to discharge the power the spinning motor is generating as it stops. I agree that the BMS in the question is probably shutting off the battery pack (disconnecting) due to the initial current draw of the motor start up.

If the motor's armature resistance is 0.5 ohms and the applied voltage is 40 volts, the start up surge current would be 80 amps. Once the motor is running the current would be more on the order of 10 amps. Of course the surge only lasts for milliseconds unless the motor is stalled/jammed.
 
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