charging battery

[nightvision]

Hi all,<br />Can some one explain to me the process that a starting battery on a boat get charge. Let just say that my battery is now at 70% and I like to charge it by using the boat motor and not with an external charger (trickle/maintainer). <br /><br />a. Will the motor charge the battery if I start it and leave it in idle? Lets say I keep it running for say 7 minutes.<br /><br />b. Or do I need to engage it into gear and drive it around for a certain amount of time. How long?<br /><br />I just like to be able to charge the battery to 100%.

 

[roscoe]

Re: charging battery

It all depends on the motor.<br />Older outboards generally did not put out much charging capacity at idle, some newer ones put out plenty.<br />Inboards put out more also.<br /><br />How long? a long time.<br /><br />Much easier, faster, cheaper than the gas, to charge with an external charger, even if you have to haul it home and charge it over night.<br /><br />More importantly, WHY/HOW did the battery get down to a 70% charge?

 

[Silvertip]

Re: charging battery

Seven minutes will not recharge a 70% battery whether the engine is at idle or wide open. If the engine is a few years old or more you would need to run wide open for probably a couple of hours to fully charge it -- provided you had an engine with a stout alternator.

 

[Solittle]

Re: charging battery

The best way to charge a "low" battery is by using an external charget set on low and charge it for 24 hours. The alternator will not do the job as roscoe states in 7 minutes or 7 hours.

 

[manykids]

Re: charging battery

My question is how old is the battery? 70% may be the best it will do. All batterys deteriorate over time and will not charge back quite as must as last month or last year or whatever.