OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Scott Bonnar 45 - Cordless Electric

hi I have inherited a scott bonnar 45 cordless electric mower with catcher,serial/model nos 4500141 and 450466,it is missing the battery.Can anybody advise me of the correct battery to test the mower and anything of interest about this model.it has the 2 piece handles that meet in the middle.regards chisel57(new member)

Hello chisel57

A warm welcome to these forums.
As I understand it, the battery was a standard 12v Automotive wet cell of the period.

I hope this helps.
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JACK.

I'll second that !

Thankyou Cyberjack ,how can I find out any more info regarding this mower's history ,collectability, parts availability, and value? Kind regards Chisel 57 (melb)

Hello chisel57

The link I supplied (above) concerned a Model 40 electric.
We have no Model 45 cordless photos for the record (that I can find).
It would be great if you could upload some photos of your machine.

Now, dating you machine is difficult. The cordless 45s were not introduced
when the Model 45 was introduced in the late 1960s. I believe the Cordless were
made from about 1970 and continued in production until the late 1970s.

They are rare today, because these machines sold in low volume when compared
to the petrol machines. Even the mains electrics were more common.

Unfortunately, they don't seem to be that collectable, mainly because of
their rarity making them largely unknown. Value is whatever the animal spirits
in consumers will muster on market day on the High street.

The Model 45 has the best parts availability of any Scott Bonnar model.
Here I mean the wearing parts - blades, bearings, chains, etc.

I have met a couple of owners of these machines and I have never found one that
has not liked their 'little electric'. They will run for an hour and a half on
a charge and should be recharged overnight before use. I do not know whether
modern battery technology might improve this. One of the site engineers -
Gadge or Grumpy - might know this.

When you consider the popularity of cordless mowers today, you have one of
the pioneering machines of the then emerging technology.

Hope this helps.
------------------------------
JACK

The technology of storage batteries has changed somewhat Cyberjack, but it has become a bit more sensitive to close control, and to selecting horses-for-courses, than it was. Essentially, open lead acid batteries in the old days were "lead antimony" types with open cells. While automotive versions could not stand repeated deep discharges, they were somewhat forgiving of overcharging, so it was feasible to use them with unregulated chargers of low capacity, provided they were not left charging for too long. These days, such batteries are becoming uncommon because it was necessary to maintain them - especially, to replace lost water from the cells, and to clean off all the corrosion around them which was mostly caused by leaks of electrolyte, plus vaporised electrolyte discharged through the cell vents during charging. Nowadays, for a lawnmowing mission at a commercial level you'd use Nickel-Cadmium batteries, which not only thrive on deep discharge, they demand it. However they also demand frequent use through their full cycle of charge levels. This is good for industrial fork-lifts, but for a private mower, completely unsuitable. Lithium ion batteries may be moderately suitable but they are very expensive and will only tolerate a limited number of charge cycles - hundreds of cycles, compared with about 5 or so cycles for a car battery, but still a limited number.

Modern automotive batteries are not all that expensive and do not require (or permit) supervision of their water levels, but they will still not tolerate deep discharges or being stored with less than a full charge. Equally importantly, they must be charged with electronically controlled automatic chargers, or they will vaporise water, discharge the vapour, and run out of electrolyte since they cannot be topped up. Deep discharge storage batteries, intended for off-grid power systems, will stand a moderate number of deeper discharges than automotive batteries but they store much less energy, can deliver much less current, and are more expensive than car batteries.

Essentially, it is quite feasible to use a modern sealed Ca-Ca car battery for a lawnmower provided it is always connected to an automatic charger when it is not mowing, and it is never discharged more than say 30% of its capacity. That means you could run one of those old mowers if you wished, just by substituting a modern car battery and a modern automatic battery charger, and always plugging it into the charger when it was not actually mowing, but it would be less efficient and convenient than a modern electronically controlled electric mower. I also want to point out that it takes me about 15 minutes of engine run-time to mow all the grass I have, plus my neighbour's nature strip. This should be well under a 30% discharge for a car battery. If the hour-and-a-half of use you mentioned fully discharges the car battery, any automotive-type battery, old or new, will only last about 5 of those uses. I suspect your informant told you how long it takes to decide to mow, drag the machine out from under a pile of old newspapers and fence posts, wheel it out to the lawn, find an extension lead and run it out, remove the garden furniture and check the lawn for foreign objects, mow a bit, have a couple of beers, mow a bit more, and eventually put everything back as it was except for the grass being shorter.

As a piece of useless information there was a type of battery in the old days that would stand quite a few deep discharges - more than a modern deep cycle battery. It was known as an "ironclad" because of its relative indestructability, and was used in submarines. However they were stupendously large and heavy for their capacity, and AFAIK were never used significantly for civilian purposes.

Hello Grumpy

Thank you for the considered and detailed reply.
I have learnt a bit, and this will be useful for members and for
future reference.

Cheers
---------------------
JACK

I'm the owner of the battery powered model 40 mentioned earlier in this thread.
I run a deep cycle battery in mine only because I don't use it much. I keep it maintained with a smart charger so I don't get any sulfation when I'm not using it.

I've also successfully removed the battery from my car on one occasion and mowed my front lawn.

I recommend trying a few golf cart shops for a cheap used battery. They are normally in pretty good condition, but if they wont last 18 holes on the course they are no good for them. They normally flog them off for about $20 (but don't hold me to that).
Buying a $100-$150 battery is mental when you compare that to how much petrol that could buy you for a mower.

With a bit of luck, and some simple testing when choosing it, you can desulphate an ex-golfcart battery and get it back to prime condition. Keeping it that way though, will require either permanent connection to a suitable automatic charger, or regular desulphating.

Just in case anyone cares, automatic chargers are not all born equal. It's a good idea to find out far more than is on the box and the blurb, about the one you are thinking of buying before you lay down your money. I just bought one a couple of weeks ago that turns out to have a feature I didn't want - it ends every charge with an equalisation phase, which smoothly runs the terminal voltage up to 15.2 Volts over the final 90 minutes. That isn't something you'd want to do repeatedly to a sealed (i.e., Valve Regulated Lead Acid) car battery unless it was a Ca-Ca type. Lovely little charger otherwise, but not suited to a lot of people's batteries. Fortunately my almost-never-used car has a Ca-Ca battery.