Battery Size

I'm pretty sure the group 24 I bought in July is bad. I've been getting an hour or less of run time on it. It'll be down below 10 volts after an afternoon of fishing. It seemed to last 3-4 times that when it was new, and never dropped below 12 volts. It only runs my trolling motor and fish finder.

I always hook it up to a .75 amp maintainer when I get home. If I'm in a hurry I will put it on a 20 amp charge from my Mac smart charger. It still seems to hold 13 or so volts after a charge, but the reserve capacity is not there.

I'm going to have it replaced under warranty, and thought about upsizing to a group 27, but it's almost twice as expensive.

It seems to me that just buying an additional group 24 would be better than spending close to the same amount as a single 27. Maybe they would last longer if I didn't run them down as far.

Thoughts?

Running a lead acid battery down to 10 volts will kill it in a hurry. They’re really don’t like to be discharged that deeply.

It sounds like you need more capacity one way or another.


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Where are you buying batteries that a group 27 is almost twice as expensive as a group 24? I just shopped for batteries. I didn't see anything like that.

For example, at Walmart, the Everstart 24DC is $74.88, the 27DC is $81.67, and the 29DC is $86.83.

SeaFaring said:

Running a lead acid battery down to 10 volts will kill it in a hurry. They’re really don’t like to be discharged that deeply.

It sounds like you need more capacity one way or another.


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It sure does kill them. The worst is to let it sit overnight or longer in a discharged state. The lead plates get covered with sulfate crust. The sulfate blocks the charge. The expensive chargers have setting to pulse the charge rate, frequency and voltage and is supposed to keep the plates cleaner. When they get old and out of warrenty I bump them down flat on the concrete a dozen times as hard as I think the plastic case can stand. That knocks the sulfate off and brings some "bad" batteries back to life. If your going to replace it eventually any way then give the concrete trick a try. It knocks the sulfate off of the plates and if the build up of sulfate is in the bottom and shorting plates to 10 or 11v (dead cell) then it knocks that crap off the bottom of them. I ran cars for 40 years picking up used "bad" batteries and fixing them that way. Works about 50% of the time. Find the used battery piles and snag two or three with the most volts in them then slam them on the ground and charge them up. Keep the best one and avoid the cost of a new one. Can get a stranded vehicle to take a charge as well to get you home so know this trick.

.Mike said:

Where are you buying batteries that a group 27 is almost twice as expensive as a group 24? I just shopped for batteries. I didn't see anything like that.

For example, at Walmart, the Everstart 24DC is $74.88, the 27DC is $81.67, and the 29DC is $86.83.

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The battery I have now is the Everstart 24MS, which as I read now is a starting battery. Maybe that is a factor in the short life. That battery is only 59 dollars, and is where I got the price figure.

Is there much of difference between the 24MS and 24DC? Or between a marine starting and normal marine, respectively.

Starting batteries have thinner plates which allows them to put out more current, but they are more susceptible to damage by deep discharges.

Deep Cycle batteries (presumably the “24DC”) have fewer, thicker plates and survive being run down better, but 10v would kill one of those pretty quickly also.

The rule of thumb we used for house batteries on sailboats was to never discharge below 50% for maximum battery life, and to generally not bother charging above 85% since the energy absorption rate slows down a lot as you close in on a full charge. If you’re charging on a plug in charger overnight, you can ignore the 85% part - that’s mostly if you are having to run a genset or engine for charging.

In essence, figure out how many amp-hours you need for fishing, and install double that to maximize battery life.

Some chargers have the ability to occasionally over-charge the batteries to knock off the sulfation, but I don’t really have good insight into how well that works and whether or not it lets you run batteries down farther without compromising battery life.


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SeaFaring said:

Starting batteries have thinner plates which allows them to put out more current, but they are more susceptible to damage by deep discharges.

Deep Cycle batteries (presumably the “24DC”) have fewer, thicker plates and survive being run down better, but 10v would kill one of those pretty quickly also.

The rule of thumb we used for house batteries on sailboats was to never discharge below 50% for maximum battery life, and to generally not bother charging above 85% since the energy absorption rate slows down a lot as you close in on a full charge. If you’re charging on a plug in charger overnight, you can ignore the 85% part - that’s mostly if you are having to run a genset or engine for charging.

In essence, figure out how many amp-hours you need for fishing, and install double that to maximize battery life.

Some chargers have the ability to occasionally over-charge the batteries to knock off the sulfation, but I don’t really have good insight into how well that works and whether or not it lets you run batteries down farther without compromising battery life.


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Thank you for the info.

I'll see if they'll let me upgrade to a 27DC when I bring mine in for warranty, and see how that holds up.

I don't routinely run it under 10 volts. That has just started happening lately with the battery getting weak.

I was able to exchange my old battery. Ended up getting a group 29, they didn't have a 27 in stock. Should have reserve capacity for days.

Lesson learned, all marine batteries are not created equal.

If you make sure to avoid discharging it too deeply, that should be a big improvement.

Tight lines!

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I wish Walmart would post better specifications for their batteries. Their website doesn't match their battfinder.com website, which doesn't match the actual batteries.

Inconsistent information, too. For the 24MS, battfinder.com says "Not designed for trolling," which is nowhere to be found on the Walmart website. I bet you would have bought the DC battery from the start if that information wasn't buried on a hard to find website.

Out of curiosity, what is the voltage on your new 29DC?

.Mike said:

I wish Walmart would post better specifications for their batteries. Their website doesn't match their battfinder.com website, which doesn't match the actual batteries.

Inconsistent information, too. For the 24MS, battfinder.com says "Not designed for trolling," which is nowhere to be found on the Walmart website. I bet you would have bought the DC battery from the start if that information wasn't buried on a hard to find website.

Out of curiosity, what is the voltage on your new 29DC?

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13ish with no load.

Ran it for a good hour tonight and voltage never dropped below 12.4. That's with my bigger bow TM, should last even longer when I put my smaller TM on the transom and use that for long lining.

MrGiggles said:

13ish with no load.

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Interesting, thanks. My new 29DC is 12.7 when charged. I'll have to see what the voltage is after I use it tomorrow (weather permitting).

Here’s a good article I found on battery charging, with some helpful charts. https://www.batterystuff.com/blog/how-to-tell-if-your-battery-is-bad.html


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Mine seems to hold right at 13 fresh off the charger.

After trolling for an hour or so it dipped down to 12.4 under load. So far so good.

Should be 13v or so after coming off the charger - if you let it sit for a while it should fall back to 12.6 or 12.7 and hold there.

I've got walmart's 29DC batteries in my boats, but one is getting on 9yrs old while the other is close to 7 so I'm anticipating they're not going to be with me too much longer. They hold a charge fine but they just don't have the capacity they once did. I'm going to try knocking them around and seeing if that will help clean up the plates, as I've had good luck with that in the past.

I have an Autocraft 24DC-1 in the fishing boat that stays in the water from April to October. Auto Zone has 20% off coupons all the time so you can get a decent price on their marine batteries. If you're running a trolling motor or have a bilge pump setup, you really want a deep cycle. I was limited to the size that would fit so I had to go with the group 24. I had to get a new battery in Feb when my old battery died and I made it through the season without having to recharge it once.

In my sprint boat that has the Chevy 350 in it, I wanted more cranking amps and went with the Autocraft M24-3 which is a marine starting battery that is 1000 cranking amps and 800 CCA. I wanted as much cranking power as I could get for the higher compression 350 engine and it has worked well.