How long do I Charge my mower battery with 3 amp charger

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  • Welcome to Motor Vehicle Maintenance & Repair! There should be an indicator on your charger stating when the battery is fully charged ... there is on most. – Pᴀᴜʟsᴛᴇʀ2 May 5 '19 at 13:17
  • It’s a Napa 3 amp manual 12 volt D.C. no lights or even a button to turn off or on. – Anita Roe May 5 '19 at 13:58
  • The charger will usually "back off" the current as the battery reaches full charge. Might take a few hours. – mike65535 May 5 '19 at 21:03

If you take the figure stated on the battery (ie 10AH) and divide it by the 3 (3A of the charger) then that will give you a reasonable time in hours.

But it does depend on how discharged the battery is initially. A battery that is dad flat will take a while to start charging and take longer overall, if that is, it will recharge.

A battery that is half charged will need less time.

However, leaving a charger on for slightly too long will only cause some gassing as long as you don't leave it for days.

If you have a timer (one of those cheap light timers) then set it for 2/3 of the time you calculate and see how the battery comes up.

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  • Dead battery only clicks when turning key. This dang thing has two red cables that run from post to where they go. Battery has positive +and negative - on top but when I put my little charger on it smoked a little and now I am getting zero spark. Why can’t anything be easy? – Anita Roe May 5 '19 at 13:55
  • @SolarMike - When you say "divide it by three", what amount of time does this become? 3 minutes? 3 hours? And you're dividing by 3 because that's how many amps the charger is? When you say "see how the battery comes up", what do you mean? How would the OP actually test this? – Pᴀᴜʟsᴛᴇʀ2 May 5 '19 at 14:06
  • @Pᴀᴜʟsᴛᴇʀ2 if you divide AH by A then the units you are left with is hours... If the OP has a battery tester that would be great - but I don't think the OP has one, so if the battery then starts the lawnmower that would be a good indication. However, given the comment by the OP the charger may not be working now anyway. – Solar Mike May 5 '19 at 14:19
  • @SolarMike - Please remember, we don't only post for the OP, but for anyone who might be looking for the information down the road. Clarify the "why" you are suggesting someone do something, then ensure you've given good enough instructions on how they can accomplish what you're suggesting. Please don't assume the OP or anyone else may or may not have the tools/knowledge to accomplish something. Just trying to help you create good and lasting answers. – Pᴀᴜʟsᴛᴇʀ2 May 5 '19 at 14:30
  • @anita never make assumptions based on the colour of the cables; always check you’re connecting charger positive to battery positive etc – Caius Jard May 6 '19 at 6:17

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