battery voltages

[keakar]

I think my battery might be going bad but im not sure about it and want another opinion.

I went out yesterday and the engine runs and charges at 14v just as it is designed to, but when I turn the engine off and then turn the key right back on, the battery shows 12.6v like I expect it should,.

but if i wait a minute or two and turn the key back on, it only shows 12.1v or 12.2v (I double checked with a test meter and the voltage meter is reading correctly)

after starting the engine it shows a 11.5v or 11.6v for a second or two before it jumps back up from the engine charging it.

I think the battery is about 3 years old and im thinking it should be showing a solid 12.5v all the time, so is my battery getting weak and needs replacing?

its my starting battery so its pretty important not to take any chances if its showing signs of being weak. the thing is, im not sure what a resting batteries voltage should be showing with nothing drawing power.

so, the question is, should a good battery always show at least 12.5 volts? goggle is all over the place with people saying anything from 12.0v-12.7v is ok

I should add that the battery still cranks the engine over and starts just fine, so maybe I am worrying about nothing here..

[lil bubba]

My gauge works fine long as the motor running or just shut down...12.5 shut down...After sitting the gauge goes down to 10.5 or 11...My digital tester still shows 12.5 ....Been this way for years so I only go by my gauge to see if the motor still charging....Get a battery hydrometer...They cheap and will tell the condition of the battery and you'll know when its fixing to go out...

[keakar]

ok thanks, I will just ignore the low gauge reading then unless it goes below 12.0v.

on a side note, my motor says it should have a 800 CCA battery yet the walmart marine starting batteries are only 625 CCA and that is what I had on the boat when I bought the motor and it has worked just fine for a whole year now.

the dealer sells a 800 CCA marine starting battery for $99 but I definitely don't want to drive 90 minutes to buy one there.

if and when I do need to buy another battery, do you think I should find somewhere to get an 800 CCA battery or just get another walmart 625 CCA battery?

800 CCA seams like it is massive over kill for a 40 HP engine but that's what it says to use

[lil bubba]

All I use is wal-mart batteries...I crank a 70 and get 4 years or better before the hydrometer says its starting to go bad...The one I have now is 2 years 1 month and still going strong...

[troy001]

for a 12v battery 12.6v is 100% charged

[jl8200]

A battery may read the correct voltage but still be going bad. The proper way to test them is to put and inductive/resistive load on them to see if the voltage decays with a resistance applied. You can bring the battery to the auto parts store and they can put a tester on it and tell you if it can still handle a load or not.

[keakar]

it was just that I see it drop from 12.5 or 12.6 after shut off to only reading 12.2 a few minutes later. further testing showed it still had the same 12.2 the next day after sitting all night so I guess it cant hold a full 12.5 but it does hold 12.2v.

I "assume" that small loss of peak full charge voltage is due to its age and not a sign of immanent signs of being about to die.

so guess i'll just roll with it and keep a close eye on what it reads when I turn the key on, if I see it start to read 12.0v at any point, then its getting replaced

[swamp snorkler]

How old is it?

If its more than 2 or 3 years I'd ditch it and get a new one.

[Dogface]

To me it's not worth getting stranded just to get a couple more months out of the battery. With it being as old as you say, I would replace it.

[kibb]

There's only one option I would explore. That is desulfate the plates if you have a charger available to do so. A lot of the newer portable, electronic chargers have this mode. It will break the buildup on the plates letting the battery accept more of a charge.

There's no way I would rely on it as my cranking battery. Some of the newer engine electronics are susceptible to damage due to low battery voltages.

[jl8200]

I may decide to keep using this battery if I had a backup plan like jumping/using a trolling motor battery in case the questionable start battery died. I go by the two is one and one is none rule if I can. Always have a backup plan just in case.

Originally Posted by keakar

it was just that I see it drop from 12.5 or 12.6 after shut off to only reading 12.2 a few minutes later. further testing showed it still had the same 12.2 the next day after sitting all night so I guess it cant hold a full 12.5 but it does hold 12.2v.

I "assume" that small loss of peak full charge voltage is due to its age and not a sign of immanent signs of being about to die.

so guess i'll just roll with it and keep a close eye on what it reads when I turn the key on, if I see it start to read 12.0v at any point, then its getting replaced

[keakar]

Originally Posted by swamp snorkler

How old is it?

If its more than 2 or 3 years I'd ditch it and get a new one.

its 3 years old, 2012

Originally Posted by kibb

There's only one option I would explore. That is desulfate the plates if you have a charger available to do so. A lot of the newer portable, electronic chargers have this mode. It will break the buildup on the plates letting the battery accept more of a charge.

There's no way I would rely on it as my cranking battery. Some of the newer engine electronics are susceptible to damage due to low battery voltages.

I was just talking with my dealer about that today, he said this:

The reason the factory wants an 850 CCA battery is so that the voltage stays high enough for proper initialization of the ECU while cranking. A smaller battery will still crank OK, but the voltage will drop during cranking, and the computer may not initialize correctly. Likewise, if it's very cold (winter fishing), the specs call for a 1000-amp battery, because batteries don't deliver the amps as well when cold, and the oils are more viscous in cold weather, causing the voltage to drop more during cranking. A good group-27 starting battery should be adequate; few, if any group-24 batteries will be adequate. Better yet would be a group-31 start battery.

so I guess I need to replace it with a 27 series battery. the prices aren't much different (maybe $20 more then the 24 series) but that means that now I need to rearrange things and redo the battery holding brackets in my rear seat storage to fit the bigger battery in there

[keakar]

turns out I found a 24 series battery with 1000 mca at napa, its the bat8304 marine starting battery with 1000 mca and 800 cca @ 0 degrees temperature

it was $135 after taxes but at least I didnt have to rearrange everything to fit a bigger battery.

hopefully wally world with get with the program and find a supplier so they can sell these high amp 24 series batteries too