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How long does it take to charge batteries?


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I am fairly new to boating, so please excuse the beginner questions. I would like to know more or less how long it usually takes to charge a 24 cranking battery and a 27 deep cycle battery using a 2 bank 4 amp onboard charger.(4/4) Let me know if you all need anymore information. I forgot to mention that the battery is 12 volts.

Thanks,

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  • Super User

Depending on the Amp hour capacity, and how far it's discharged.  105 Ah battery discharged to 25%, it will take your 4 amp charger 20 hours to charge it back.  With that said, that is way too small of a charger for those batteries.   You need at least a 10 amp per bank charger to properly charge that size battery.

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Depending on the Amp hour capacity, and how far it's discharged. 105 Ah battery discharged to 25%, it will take your 4 amp charger 20 hours to charge it back. With that said, that is way too small of a charger for those batteries. You need at least a 10 amp per bank charger to properly charge that size battery.

X2

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Unless you are fishing daily you might want to invest in an automatic charger and leave them on constantly. I keep mine on a 2 amp automatic charge unless I'm going to be fishing two to three days in a row. If that's the case I bump it up to either 6 or 10 amps so I will have enough juice for the next day.

I agree with the above post, if you want them charged up for the next day you need to use a higher charging rate.

If you leave them on constantly be sure to keep the fluid levels checked in the batteries.

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A battery should be charged at approx 10% of it's rated capacity.  2 amps is way to slow of a charge rate for any group 27 battery and is actually harmful to the battery.  When charging, the battery needs enough current to develope enough bubbles to keep it from stratifying and periodically needs enough charge current to cause some degassing to equalize it.

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Unless you are fishing daily you might want to invest in an automatic charger and leave them on constantly.

I'll drink to that.

In the early years of electric motors, we were told that it's important to fully cycle

a deep-cycle battery, otherwise you'll shorten the lifespan of the battery.

I think that rumor was spawned by some battery manufacturer ;D

Right after closing the garage door, I switch the MinnKota auto-charger to "On"

where it stays until the boat is hitched-up again. The battery is in its second year,

and I don't believe it's ever been discharged below 80%,

and generally meters around 90% when we return.

Roger

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Deep cycle batteries have a finite number of recharge cycles in them (depends on how well they have been cared for). If not discharging deeply, you are wasting life. If you were given a credit card good for 50 fill-ups for your car (not gallons, fill ups) you would be foolish to fill up at 3/4 or 1/2 a tank.

The gassing on a battery being charged starts at 80% charged (no current flow) and continues till done. Equalizing has nothing to due will the amount of current flow. Equalizing is accomplished with time. All the cells reach full charge at different times. Longer charge time allows the more discharged cells to catch up to full; thus all cells now equal.

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Fishbone,

You are right about batteries have a cycle count but you are way out in left field about how it works. If you deep discharge a battery down to 20% charge, you may get 150 - 200 cycles. If you only disharge it to 50% you may 300 cycles, at 75% you will get even more cycles. It's recommend not to recharge one with more than 90% or more charge but I'm like Catt, I ain't going out without a battery that's 100% charged if I can help it.

You should never discharge a battery below 30% charge. Doing so causes plate damage in the battery.

Also, your amost right on degassing. Degassing is caused by a state of over charge, which to fully charge a battery, it needs to be overcharged by 6%. That's why those cheap automatic chargers just cause a battery to die a slow death. They don't have the capability to hold a battery at full charge for the extra time it takes to overcharge one so they never fully charge the battery. During the charge cycle, small bubbles are being developed, too low of a charge current and these bubbles are to small and too few to keep the electrolite mixed.

This will also be my last reply on this post because I see where it's heading and I'm not getting into it.

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If not discharging deeply, you are wasting life.

Totally False!

Deep-cycle batteries are built to TOLERATE deep discharging and recharging,

they are not built to BENEFIT from deep recycling, a rampant misconception.

Deep-cycle batteries that undergo regular 75% DOD (depth-of-discharge),

last about half as long as deep-cycle batteries that are cycled at 50% DOD.

Furthermore, deep-cycle batteries cycled at 25% DOD last about twice as long as batteries

cycled at 50% DOD (four times longer than 75% DOD). However, when you get below 10% DOD,

battery life reaches the point of diminishing returns, where lead dioxide tends to deposit

on the plates, which over time may cause shorting points.

In a perfect world, a deep-cycle battery would never fall below a 75% state-of-charge,

which is to say, it would never discharge more than 25%.

I knew there was a reason why I almost never enter this forum.

Roger

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