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Collection, Preservation and Display of Old Lawn Mowers

Atco royale B30 starter battery

Probably a dumb question.

The 12v 12ah battery now fails to start the mower.

Its is self charging I assume?

In which case is it fair to say the battery has gone bad?  


wristpin Sun, 22/05/2022

The engine should charge the battery but even if it isn’t working a fully charged battery will usually start the machine for several weeks of normal use.

Andrew Pritchard Tue, 24/05/2022

Checking the voltage across the battery and there's very little difference between engine off and running?

Do you need to recharge these batteries manually or should they get suficient charge from the engine?

wristpin Wed, 25/05/2022

If the battery is “full”  the engine’s alternator won’t be able to “ push” in more charge in but as you have already said that the starter won’t operate, you need to carry out a systematic check of the whole starter system.If you don’t have access to a multi meter , several basic tests can be done just using a standard 12 volt automotive lamp bulb such as a 21 watt tail light or indicator one. For a start get hold of a schematic diagram of the machine’s starter, key switch  and charging system which should give a greater understanding of what and where to look.  A very basic start is to ensure that the battery negative is properly earthed.

What engine is fitted to your machine?



Andrew Pritchard Thu, 26/05/2022

B&S intek 206

I've now charged the battery fully and all seems fine at the moment.

I'm just not sure if your expected to have to charge the battery on occasions or wether under normal use it will get topped up from the engine while it is running?

wristpin Thu, 26/05/2022

Unless the battery is failing or you are starting and stopping a lot in comparison to your running time , auxiliary charging should not be needed. A rule of thumb**is that quarter of an hour’s running at governed top rpm is needed to replace that used for one start. So unless the box is filling very frequently with the engine stopped and restarted every time the alternator may be struggling to keep up. Typically we used to see that situation with walk behind rotaries being used with autumn grass growth and leaf collecting and the Operator Presence Control dictated that the engine stopped every time the collector bag was emptied.

** not sure who's. !

Andrew Pritchard Fri, 27/05/2022

Thanks for this wristpin.

Before I get too deep into this though as a simple check. With the engine running I get 12.6v and when the engine is stopped it drops to about 12.5. So I guess that is the trickle to top up the battery.

Does this sound right, I was a expecting a greater difference in the 2 voltages?

wristpin Fri, 27/05/2022

Unless it causes you a problem in normal use I wouldn’t worry about it . If it gets to the stage of not starting on the key when it has regular use, see whether trickle charging cures it. Only then,  if key starting is important ,  possibly consider a new battery. Don’t buy a new battery just before a winter lay up, start the new season with the new battery.