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Want to switch from a cordless mower to a corded one. B&

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Inkidu

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Hello all Nicholas is my name this is my first post, wish I could say I contributed to

the site but I can't. Now that I found the site I will look over some topics.

Fairly low experience level.

What I would like to do is turn my B&D lawn mower (24volt two series connect 17Ah

batteries) to a corded mower. The battery pack (2 12volt similar looking to a

motorcycle battery) cost $130 w/o shipping. Have some fairly decent DIY skills

but I want to make sure I am making some correct preliminary decisions.

Thinking that a (2) 12volt 17.2 Ah batteries should be replaced by a

AC to DC converter spec at 24 volt and 17 amps. Correct?

EDIT

Looking at the battery more closely now it says 4.3A (cycle use???)

I kind of thought that 17 amps seemed like a lot. So 24v 4amp converter. Right?

Not that I would

hold anyone to it but what if even possible or advisable change could be made

to run at a high power. That is should I raise the volts and/or the amps?

Any help would be appreciated and would share results with others.

I couldn't find a link myself for such a conversion.

I have been a Meanwell fan for my led diy projects but any suggestions for

the AC to DC converter?

Is there some obvious things I am not taking into consideration?

Side note

I do like the mower (low noise, easy maintenance, and instant on/off) and

I did get over 10 years out of the battery ( the last few years not so good) but

I just figured that I might not get so lucky with the battery again and the mower

would be lighter with out the heavy battery.

Thanks for any help.
 

The ampere hour (Ah) capacity of the battery is a measure of the total energy that can be stored in it - nothing to do with the instantaneous power that can be taken from it. You need to know the power the motor takes. You may have to measure this if you cannot find it in the instructions or on the motor itself.

Keith
 

hi
the (17ah)capacity its mean you can run load on battery with 17a or 408 watt for one houre and then you must charge the batterry but if you run load 204 watt you can use same battery for aproxemitly two hour
you must kow how much your motor power you can found it in manual for your machine or write on motor or on frame your mour
 

Re: Want to switch from a cordless mower to a corded one. B&

the (17ah)capacity its mean you can run load on battery with 17a or 408 watt for one houre
Click to expand...

Actually most AH ratings are based on 1/10 the current draw of the AH spec. You can ran a 17AH battery at 1.7 A for 10 Hours. You will not be able to run it at 17A for 1 hour.

ken
 

Re: Want to switch from a cordless mower to a corded one. B&

Thanks for the replies.

My batteries are bad. So while it still runs I am not sure I will get any good info

about what the motor draws. I have not located any info on the mower itself and

I am still trying to track down a manual. I have read some generalities about

what Ah battery you need if you want a certain amount of consistent amps.

From that general approximation you get 4 amps. That is if you wanted more than

4 amps consistently you would go with a larger Ah battery. I have found this.

**broken link removed**

While I am not positive that this is the motor there are not a lot of cordless 24v

mowers out there. I would also think that it is probably in the ballpark.

Given those specs from the link any recommendations?

I noticed it said no load amps. (4.5) And I would think that is close to what I

want because (assumption) you probably don't want the blade to slow down

or another way to put it have a load. ????

Like I said before I like meanwell products for my led projects and I was

eyeballing this power supply. RS-100-24

**broken link removed**

But I could go with any power supply I just thought this might work and

it is not to expensive. I kind of would like to go little bigger (amps) because

I don't want the power supply to overheat and turn off but a 150 watt power

supply seems to big. ???? I am assuming that the motor will draw what amps

it needs so if I went to big could the motor draw to much and then burn up?

Please any help would be appreciated.
 

Re: Want to switch from a cordless mower to a corded one. B&

so if I went to big could the motor draw to much and then burn up?
Click to expand...
No.
6 amps is ~probably~ enough.
 

Re: Want to switch from a cordless mower to a corded one. B&

Hi. With regards to safety, the bigger the current handling of the supply is, the better. The supply won't put any bigger load to the motor as long as it's voltage stays at 24V.

The Meanwell RS-100 doesn't seem like the right thing to put into a mower. It's intended for driving fine electronics. Voltage spikes from the motor could damage it. The more or less open case isn't ideal for environment where bits of grass and dirt are flying around.

Look for some rugged power supply. A closed one with good current capabilty and resistant to noise on the output. Although I personally dislike linear power supplies, you may perhaps find out, that this kind is the right for your application.
Good luck!

JS.
 

Re: Want to switch from a cordless mower to a corded one. B&

Thanks for the replies.

I noticed Jameco lists the max output current

and max current rating. What is the difference? Looking at this.

https://www.jameco.com/webapp/wcs/s...amecoall&ddkey=http:StoreCatalogDrillDownView

Since the current rating is closer to what I need (assumption) would this

offer more protection from spikes. I would like to go with the switching p/s if I

can because of the difference in weight. From what I have read so far the

newer switching power supplies have gotten more reliable and this one was just

released, but it would be nice to go with something not so expensive. Part of the

idea for this project was to save money. $120 is about what the batteries cost.

Although unlike the batteries this would probably never need to be replaced.

The overall weight of the mower would be reduced by quite a bit. I would think

the electrical cost of running the mower would be reduced.

One thing I didn't really like with the setup was to have the best chance of

the batteries lasting a long time you needed to keep the mower constantly

plugged in. I would not think the charger is that big but it would seem that the

cost would add up. The newer model $400 comes with a removable battery so you

can charge in one place and store the mower in another spot i.e. no power shed

Side note the p/s will be enclosed by the cover but there will almost certainly

be a lot of dust about so hopefully this p/s , because it is more enclosed and has

a on/off switch for the fan, will provide a little more protection.

Thanks for all the help and once I get this working I will post the results for

others interested in such a conversion.
 

Basically a mains to 24v transformer connected to a 25 amp diode and antihum cap should work.
 

KMoffett said:
the (17ah)capacity its mean you can run load on battery with 17a or 408 watt for one houre
Click to expand...

Actually most AH ratings are based on 1/10 the current draw of the AH spec. You can ran a 17AH battery at 1.7 A for 10 Hours. You will not be able to run it at 17A for 1 hour.

ken
Click to expand...
hi... :cry::cry::cry::cry:
iam sure for which i write and itest it with my spicial tool andread battery manual and if you rread it you can belaive my note and :!: 1/10 :!: wrong

Added after 3 minutes:

hi
first you must measure your motor curent so you can use new battery as your car 2battery 12v and test curent by voltmeter you can take it arroud you pepole
 

Re: Want to switch from a cordless mower to a corded one. B&

Folks, don't speculate about the battery's discharging current, it's dependent on the battery's specific design. Besides, Inkidu said it's about 4 - 4.5A, so settle with that. :)

The output current is what you can get on the output, 14A at 24V in your case. The maximum current rating is how much it may draw from the mains. Typically it will draw much less and the 5A is only at power-on or so.

There's nothing wrong with the switching supply. If you can get it, good for you. An additional snubber at the motor end could help, but be careful with inuctors as an improperly designed snubber may cause trouble at switching on/off. But that's just an optional thing.
 

These motors take quite a lot of current at startup and need to be driven from a low impedance souce, i.e a battery. You would need very large capacitors on your psu to provide enough initial current. Then you have the problem of handling the effective short ciruit while the psu charges the caps, but still provide enough running current. This is not an efficient way to do things, and furthermore quite dangerous to mess with the mains in this fashion. I would advise you not to try it, but instead consider a new or used electic mower, they are not very expensive these days, probably cheaper in the long run than all the messing about anyway.
 

Re: Want to switch from a cordless mower to a corded one. B&

I appreciate anyones contribution.

It is easy to think that something like this is easy

if you don't have much first hand experience.

I read the one post about needing startup amps.

I might be wrong on my assumption but as a test

I turned easily the spindle of the motor with two fingers

so it least in this instance I would think the startup amps

are not to great. While I would assume the instant I run into

a thick patch of grass might be trying, I don't think startup is

a problem. I have taken into consideration that having more amps

will be beneficial. This is the reason why I have been looking at the

https://www.jameco.com/webapp/wcs/s...oreId=10001&catalogId=10001&productId=2094881

Even though I don't really want to spend a lot of money maybe this extra

power will give me some lee way. While I have appreciated comments

on other solutions this in my mind is a possible turn key solution for

someone with limited experience. In the end I am only so comfortable with

making to much DIY work. I am hoping to not find myself in the group who

know just enough to be dangerous. If something else goes wrong with the mower

I will still have a very nice power supply.

Please by all means contribute this thread might help others besides myself.

EDIT

Can I assume since the power supply is overpowered that I might not need to

run the fan. Obviously with in reason i.e. not long run times and not really high

ambient temperatures.

Trying to avoid as one post mentioned the problem of debris input.
 

Re: Want to switch from a cordless mower to a corded one. B&

Thanks for the reply

USA

Although I am not completely ashamed of ignorance this is hard for me

I have little experience with hands on electronics.

"Basically a mains to 24v transformer connected to a 25 amp diode and antihum cap should work"

A gather this would be a linear setup after that I am still researching.

Like I said earlier I don't won't to fall in the category of knowing just enough

to be dangerous.

Thanks for any help.
 


Startup current is not to do with how easily the motor turns when not powered. The current of the motor will depend on speed and will be highest when it is not moving. When you start the motor the current will be very high and will drop as the motor builds up speed.

A number of years ago I designer a speed controller for a mower for a major company and the running current was a few tens of amps at 12V but the surge, if uncontrolled, was several hundred amps. I used a PWM controller with motor current monitoring to limit the current to 60A.

Keith
 

Re: Want to switch from a cordless mower to a corded one. B&

Not that I don't believe you about the amps and I appreciate the input but there

are only (2) 17ah batteries and this mower can easily go 4 hours without a

charge. The manufacture says "trouble-free cutting of up to 1/3-acre home sites"

That seems like a lot of cutting if it drew as many amps as you mention.

As one person pointed out battery design is critical in assuming the

constant amps a battery could provide but I would assume that you wouldn't

to draw to much relative to the overall Ah. I am sure this setup runs for some

time without a charge. My one link also says a 24 volt lawnmower motor

the spec is 4.5 no load amps.

**broken link removed**

This no load condition, I would assume, almost is always the state the motor runs

i.e. a grass blade only puts up so much of a fight with a whiling sharpen steel

blade. I was planning on use the power management that is part of the mower

That is just place the output lines form the power supply where the battery was.

All that said I might just get a battery but if I do I want to get something better.

(LiFePO4 battery). I like to tinker and these batteries have over 2000 cycle life.

I want a battery that last. I just seems like such a waste to always

be replacing a battery. Big ? cost. Anyone have an opinion on these?

https://www.batteryspace.com/lifepo418650battery256v2500mah64wh18arate2rx8withpcb.aspx

https://www.batteryspace.com/lifepo418650battery256v1200mah30wh18aratewithpcb.aspx

Granted I couldn't mow 1/3 of an acre but I don't need to. They are use this

tech to power cars.

As always I appreciate anyones corrections or input.

Thanks for any help.
 

Inkidu said:
Not that I don't believe you about the amps and I appreciate the input but there

are only (2) 17ah batteries and this mower can easily go 4 hours without a

charge.
Click to expand...

My figures are based on having designed a 12V cordless mower for a major manufacturer. I would have to find the original test results but I know the power drive was rated at 480A peak and I current limited to 60A which operated during startup. I am not sure of the exact running current.

Your figures will be halved because it is 24V, but also, as the motor will be different, the current will be different. The important thing to know is that surge currents could be very high so until you know what they are, don't buy a power supply otherwise you might find it shuts down as soon as you try to start the mower, even if it has enough power when it is up to speed.

Keith

Added after 3 hours 47 minutes:

I have just dug out the old specifications for the mower controller I designed. The specified surge current of the motor/battery combination was 150A at 12V with a 50A to 60A limit to be built in to the electronics. No running current was specified (the whole circuit was designed to run at 60A continuously anyway).

Keith.
 

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