Help with battery for lawn mower motor

Other Hardware Motors, Mechanics, Power and CNC
1

I have built a remote controlled lawn mower using an Arduino, but had a question specifically related to the motor and battery arrangement I have for the motor powering the blade/cutter.

The motor is a 24v 250w Scooter motor

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Previously I was using two 12v SLA (REC10-12 Yuasa Battery 12v 10Ah) connected in series to give 24v 10Ah. Which worked great, had lots of power and didn't stall even with long grass. However, it took a long time to charge, was really heavy and perhaps not the best battery type to use?

So I have upgraded to an e-bike battery. which is again, 24v and 10ah. This battery is not available anymore, but the details can be found here https://batteryempire.co.uk/startseite/3984-green-cell-e-bike-battery-24v-104ah-250wh-frog-ebike-2-pin-with-charger.html#additional-info

The problem I am having is that now the motor will really struggle with long grass that the old setup seemed to be able to handle. It will even cut out (which I think is the overload protection build into the battery?). I think its also spinning slower than it used to.

So all in all, it now feels underpowered. Can anyone explain what might cause this? as the specs appear to be the same from my understanding?

Could it be that I was actually overloading the SLA batteries, but they just handled it? Where as the e-bike battery is capping the power?

Could I use a 36v e-bike battery? which seem to go up to 12/15/17 ah

2

Cookied links are not opened.
You need to know what max current the battery is made for, and the motor max current.
How do You control On/Off?

3

Sorry, not sure what you mean by cookie links not opening. It opens for me from a 'incognito' window?

The e-bike battery says 24v 10ah 250w,

the motor specs are :

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Just noticed the 13.5a rated current.

I was going by the 250w.

24v x 13.5a = 324w ??

So does this mean I need upwards of 350w? (as max current will be higher than rated current)

I can't seem to find any 24v e-bike batteries that have a power rated higher than 250w.

It is being controlled by a simple relay module

4

24V 10ah doesn't tell you much.
I imagine that the SLA batteries can supply much more current than the Li-ion maybe 40-50A.
Also as you have found out, the Li-ion has a BMS inside that will cut the current

5

So was I right with SLA batteries to begin with then? :upside_down_face:

6

You can buy high discharge rate Li-ion batteries, it's just that particulay E-battery was just a bad choice.
Another option is an LIFePO4 battery. They are kind of inbetween Lead acid and Li-ion

7

ah ok, doh!

Isn't this the kind of battery used in Scooters though?

Just had a look for LIFePO4 battery at 24v and they are super expensive :frowning:

8

Yes but there are no specifications given for maximum currnent, so who knows

Just had a look for LIFePO4 battery at 24v and they are super expensive

So are high discharge rate Li-ion.
The SLA will be the cheapest solution but also the heaviest

9

okie doke. Thanks for your help. I think I'll go back to the SLA

10

For the price you can't beat them. Plus they are very tolerant of overcharging and overdischarging.

1 Like
11

Motors like that are used in those kids cars and they all use SLAs, like this : https://electricrideoncars.co.uk/12v-4-5ah-battery-6fm4-5-replacement-battery-for-kids-electric-cars-and-kids-electric-scooters/
What capacity to choose depends on how long you want it to work, possible battery size restriction etc.

12

Ebikes sold in the United States must be limited in the speed/power, so that is why the battery control limits the current.

13

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