Charging 2 batt. with a single 5 amp charger help

I installed a I-pilot on my Minn Kota Powerdrive V-2 , 12 volt. I want to install another battery for longer lasting with parallel wiring. I know the 5 amp charger I have will probably be a slow process, but, would like to try it. I have heard 2 ways of mounting the charger. 1st. , keep the charger mounted to the first battery like it was originally & it will charge both batteries, with the parallel wiring. 2nd one. , place the pos. cable from the charger on the first batt., & place the neg. cable from the charger on the 2nd. batt. , neg. terminal. it's suppose to charge both batteries. All items are new , & the batt charger is a Pro Mite 5 amp. Thank you, Don.

Either way will charge both batteries, your call. I would pick which way only on which are the closest posts to me. LOL

You'd be money ahead in the long run to get a bigger charger. The 5A is going to be very slow charging two batteries if you discharge them very far, and as the batteries get some age on them, it may not be able to charge them at all.

You'd get longer battery life with a faster charger.

Another ? When I purchase a larger amp charger should I stay with the single bank charger say a 10 amp , or should I just get a larger 2 bank charger. When i had my 24 volt TM I did use a 2 bank charger. I just wasn't to sure with a parallel 12 volt system. Thanks again guys.

This brings to mind a question..... if you have a 5 amp charger and it takes 8 hours to charge to maintenance mode, does that mean it has restored 40 amp-hrs to the battery, or putting it another way, on a 100 amp-hr rated battery does it indicate it was only 40 percent discharged? The older chargers showed charge rate dropping off over time... if this happens with modern chargers, has less than 40 Ah been charged?

i have minnkotta 2bank 5amps per bank with a 24v trolling motor it works fine charges slow but it gets the job done just plug it up whenyou return from fishing and shuts off by itself got it from bass pro shoppe

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Originally Posted by tail chaser

Another ? When I purchase a larger amp charger should I stay with the single bank charger say a 10 amp , or should I just get a larger 2 bank charger. When i had my 24 volt TM I did use a 2 bank charger. I just wasn't to sure with a parallel 12 volt system. Thanks again guys.

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If you ever think you might go to a 24V system, get a two bank and use both banks. It will work fine on a 12V parallel system.

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Originally Posted by cache22

This brings to mind a question..... if you have a 5 amp charger and it takes 8 hours to charge to maintenance mode, does that mean it has restored 40 amp-hrs to the battery, or putting it another way, on a 100 amp-hr rated battery does it indicate it was only 40 percent discharged? The older chargers showed charge rate dropping off over time... if this happens with modern chargers, has less than 40 Ah been charged?

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Quite a bit of the current used from a charger is wasted when charging a conventional lead-acid battery due to the battery's internal resistance. Around half.

Modern chargers start out by charging wide open. The battery voltage will rise as it charges, while the current remains constant at whatever the max current of the charger is. When the battery reaches the point that the charger is at its max voltage (usually about 14.7V), the charger holds at that voltage, and the current the battery draws drops as it charges. When the battery current drops below an amp, the charger turn on the green light and reduce its voltage to about 13.1V and remain there unless the battery draw increases.

So the short answer is you really can't tell how much you put back in the battery unless you monitor closely.

Watch out for sulfation charging 2 batt with a 5 amp charger. Same goes for charging on maintenace mode 2amp.