Have i been connecting my 12-volt batteries wrong

I'm never above learning better ways for processes I thought I've been doing the best way for years. For years I've been running and charging my 12-volt batteries for in parallel with one cable between each battery's positive and negative terminals. I know this is parallel, but I've been connecting the trolling motor's cables and charging clips to just one of the battery's terminal posts (positive and negative to the same battery). Should I be connecting the tolling motor and charging clips to the positive post of one battery and the negative of the other?

Yes, Neg of one battery and pos of other. In this connection of parallel batteries the combined amp hour out put us doubled so charging time will about double. Fyi Google "charge parallel batteries with one charger" and you get several good videos and link to "Battery Genius" page that explains better this this old snook can 😄

[QUOTE=Dobe Mejuwa;557331]Yes, Neg of one battery and pos of other. In this connection of parallel batteries the combined amp hour out put us doubled so charging time will about double. Fyi Google "charge parallel batteries with one charger" and you get several good videos and link to "Battery Genius" page that explains better this this old snook can [/QUOTE]

Good post. I suppose I need to change my ways too. Which begs the question . . . if only connecting the charger to one battery lengthens the charging time, is the discharge time affected by how, for example, the trolling motor is connected? I have it connected to one battery and assume it is just as efficient as connecting to both.

[QUOTE=Dobe Mejuwa;557331]Yes, Neg of one battery and pos of other. In this connection of parallel batteries the combined amp hour out put us doubled so charging time will about double. Fyi Google "charge parallel batteries with one charger" and you get several good videos and link to "Battery Genius" page that explains better this this old snook can [/QUOTE]

I didn't think it made a difference, but to be honest it has been a long, long time since I ran 12v.

When I did run 12v, I ran parallel with two batteries, and had trolling motor hooked to one battery and charged to the other.........never though about pos and neg on opposite batteries for better efficiency.

In series you increase voltage, not total amp hours. So a charger takes less time to replace the amp hours in the batteries. Example 2 x 100 amp hour battery's in series = 24 volts, but still 100 amp hours, so if 10 amp charger, then 10 hours X 10 amps charger output = 100 amp hours total recharged

In parallel you increase total amp hours, not voltage. So a charger takes more time to replenish the total amp hours available in both batteries. Example 2 x 100 amp hour battery's in parallel = 12 volts, but still 200 amp hours, so if 10 amp charger, then 20 hours X 10 amps charger output = 200 amp hours total recharged if I charge on the pos and neg of one battery first. Why? First battery in parallel has to be back to full capacity before it passes the excess amps onto the second in the parallel set up.

But if I go neg one battery and pos on other at opposite ends of the parallel set up, I flow the full 10 amps available from the charger to both batteries at once, and so time to charge each 100 amp battery is 100 amps to charge divided by 10 amps in or 10 hours to charge.

[QUOTE=Dobe Mejuwa;557464]

But if I go neg one battery and pos on other at opposite ends of the parallel set up, I flow the full 10 amps available from the charger to both batteries at once, and so time to charge each 100 amp battery is 100 amps to charge divided by 10 amps in or 10 hours to charge.[/QUOTE]


LOL, it doesn't work like that. The cable between the two batteries distributes the charge evenly no matter how it is connected.

In parallel the 10 amps is split equally between the two batteries. You don't magically get 20 amps out of your 10 amp charger by connecting to a different point of the wire. The entire wire is hot. I'm not sure why you would think only the first half of the wire would be hot until the battery is charged. In your example that 10 amp charger is sending 5 amps to each battery and it will take 20 hours to charge from 0 to full.

Even without a charge the batteries will self balance. If one battery has a slightly higher charge it will push that to the battery with the lower charge until they equal out.

el I'll be....:D