Can older batteries hurt an alternator?

MakoNY

Petty Officer 2nd Class
Joined
Dec 27, 2007
Messages
110
I can't get my batteries to take a full charge. They are still strong and sit around 12.6v and load test fine, but my charger can never get them to full charge to where it shuts off and they get real hot when charged for a while. They are Group 24 1100MCA EFI rated batteries.

I've noticed my alternator has started to fluctuate, charging less at idle around 13.6v and more at higher idle or cruising speed around 14.2v or so. I've never seen it fluctuate like this before and was wondering if it's normal or if it's a sign my batteries are shot. Also wondering if batteries that can't be fully charged will hurt my alternator, it's brand new has maybe an hour on it.

By the way it's a Merc 250 EFI.



Thanks.
 

dwparker99

Petty Officer 3rd Class
Joined
May 9, 2010
Messages
98
Re: Can older batteries hurt an alternator?

Are you talking multiple cranking batteries hooked in parallel charged by an onboard or portable charger? What type charger are you using when they get hot? Is it a known good charger? If the charger is good, batteries getting hot is bad. Charging them may damage the new alternator. I would identify the problem prior to running the big motor.
 

MakoNY

Petty Officer 2nd Class
Joined
Dec 27, 2007
Messages
110
Re: Can older batteries hurt an alternator?

I was charging them with a Black and Decker Smart charger. I used the "Recondition" cycle first and then put them on a charge, but it never got to the point where it showed "Full Charged", it just kept going. I came out in morning at it was ripping at 25A and the battery was very hot, and this was after about 14hrs straight. I let them cool down and added distilled water before putting them back in the boat.

The batteries are in parallel when they are on the boat, but I didn't charge them that way, I had them out and in the garage.

All cells on both batteries test good with a hydrometer, and they load test perfect and hold a charge around 12.6-12.8. Just thought it was strange that the new alternator starting charging less at idle. When I first installed it, it worked great and charged fully at idle, put about an hour on it and now it charges lower at idle.

The batteries are Power Master combination starting/Deep Cycle batteries. They say EFI rated and are 1100 MCA, and I believe 125Ah reserve. I don't know the history on them as they came with the boat I bought this year, but I can only assume they weren't taken care of, as most people don't.

Thanks.
 

flargin

Chief Petty Officer
Joined
Aug 13, 2008
Messages
540
Re: Can older batteries hurt an alternator?

in response to your question; Yes. a bad battery can kill an alternator.

A battery can become higher in resistance and that resistance drive the alternator to push more energy. Ultimatly it will not be able to keep up and will die.

Break the two apart and test/charge individually. Likely one is working, and one is dying..

don't think batteries are lifetime, they can go out in days or years.... always suspect a battery is bad, even if you just bought it today.... can save yourself a lot of time.
 

dwparker99

Petty Officer 3rd Class
Joined
May 9, 2010
Messages
98
Re: Can older batteries hurt an alternator?

I was charging them with a Black and Decker Smart charger. I used the "Recondition" cycle first and then put them on a charge, but it never got to the point where it showed "Full Charged", it just kept going. I came out in morning at it was ripping at 25A and the battery was very hot, and this was after about 14hrs straight. I let them cool down and added distilled water before putting them back in the boat.

The batteries are in parallel when they are on the boat, but I didn't charge them that way, I had them out and in the garage.

All cells on both batteries test good with a hydrometer, and they load test perfect and hold a charge around 12.6-12.8. Just thought it was strange that the new alternator starting charging less at idle. When I first installed it, it worked great and charged fully at idle, put about an hour on it and now it charges lower at idle.

The batteries are Power Master combination starting/Deep Cycle batteries. They say EFI rated and are 1100 MCA, and I believe 125Ah reserve. I don't know the history on them as they came with the boat I bought this year, but I can only assume they weren't taken care of, as most people don't.

Thanks.

It is important to understand which batteries you have, how old they are and how you are charging them. Are they Grp 24s? 1100 MCA and 125Ah seems high for a grp 24. Does the batteries have a sticker on them that indicates when they were shipped and characters stamped in the plastic which will tell when they were manufactured? When you say you "put them on charge" and "let them cool down" it sounds like you are charging in parallel or do you have two chargers?

I think the recondition cycle on your charger is an equalization charge. This cycle raises the voltage as high as 17 volts and can cause the battery to heat up and cause major gassing. Some chargers run this cycle automatically at the end of the regular charge cycle. It is my understanding that the battery should be fully charged prior to applying an equalization charge. I would use it sparingly on any battery and would make sure I understood its purpose.

The alternators output voltage is relative to the resistance it encounters in providing its max current. At idle, if the max output is 5 amps and your battery is a little low and you are running other electronics, there will be little resistance to the 5 amp output so the voltage will be low. At 1200-1500 RPMs, if the max output is 60 amps, the voltage will rise until it reaches its regulated voltage of 14.2-14.4 volts and then the current will decrease to maintain the voltage ceiling.
 

MakoNY

Petty Officer 2nd Class
Joined
Dec 27, 2007
Messages
110
Re: Can older batteries hurt an alternator?

Each battery has a sticker on top of it, one side says Part # 24M10006D.P., 1100MCA/165Ah Reserve, this is the side that has a hole punched in it. The other side of the sticker says Part # 27M10006D.P., 1100MCA/200Ah Reserve and is not punched.

I assumed the first two numbers in the Part # were the Group #, but I guess I could be wrong on that. Either way 1100MCA and 165Ah reserve are spelled out.

I only have one charger, I didn't charge in parallel. When I said "them" I meant when I did each one separately the same way as one another. I didn't charge them together.

The book for the charger says the "Recondition" cycle is to break up any sulfate built up on the plates. It's a 24hr cycle and I periodically went out and checked each battery on this cycle and they were not hot at all, not even warm and were not gassing. I was going to charge them with my smaller 10amp charger overnight but wanted to see if the "Smart" charger would do a better job. It never shut off (on either battery) and each battery got very hot to the touch and each gassed a lot, I had to add water to each afterwards.

I was thinking that charging like that might have killed them. I let each sit for about 8hrs after the charge before I gravity tested each cell and all cells were equal and showed full charge. I load tested each next and each load tested perfect and they are sitting at 13v, now 2 days after having any charge go through them.

Does it take a little while for the water to fully mix into the acid after you add water?

When I have my load tester on each battery with the engine running it shows "charging voltage" in the "Good" range at both idle and at around 12-1400. When you first start it, it charges lower (around 13.6v) and then when you run it at a faster idle it goes up to about 14.2-14.4. When you pull back to idle again after a minute or so it tends to sit at a higher charging voltage then when you first start it, just around 14v. I've done this on each battery separately, using the OFF-1-ALL-2 battery switch.

Thanks.
 

TerryMSU

Senior Chief Petty Officer
Joined
Jul 31, 2007
Messages
743
Re: Can older batteries hurt an alternator?

I think the recondition cycle on your charger is an equalization charge. This cycle raises the voltage as high as 17 volts and can cause the battery to heat up and cause major gassing. Some chargers run this cycle automatically at the end of the regular charge cycle. It is my understanding that the battery should be fully charged prior to applying an equalization charge. I would use it sparingly on any battery and would make sure I understood its purpose.

The recondition cycle is for sulfation. It pulses the battery with a very high frequency pulse. And yes, I have this brand of charger and I have seen this recover a "bad" battery

TerryMSU
 

TerryMSU

Senior Chief Petty Officer
Joined
Jul 31, 2007
Messages
743
Re: Can older batteries hurt an alternator?

in response to your question; Yes. a bad battery can kill an alternator.

A battery can become higher in resistance and that resistance drive the alternator to push more energy. Ultimatly it will not be able to keep up and will die.

Higher resistance at a constant voltage (such as a regulated output) will result in lower energy. A shorted cell will result in much higher current and this will result in a much higher energy level. Other than that most of what you are saying is correct.

TerryMSU
 

MakoNY

Petty Officer 2nd Class
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Dec 27, 2007
Messages
110
Re: Can older batteries hurt an alternator?

I was thinking that too Bubba. I found it strange that as time went on the charger was increasing amperage to the battery. It would start around 6 or 7 amps and I'd come out an hour or two later and it would be up at around 12 or so, then the next morning it was sitting at just under 25, like 24.7 and the battery was hot a hell.

I'm not any kind of expert but I always though charging amperage should drop as the charge increased within the battery. I know my old 10amp "non-smart" charger's ammeter always drops as the battery gets more and more charged.

Guess I shouldn't have assumed the charger was "Smart". Although my friend used it on his and he said they got a little wamr and the next day it showed "Fully Charged" in the little LCD display.

I don't know, but to me it seems as though these batteries are fine, what else can I check, I mean they sit at 13v, they load test fine and the hydrometer shows them as fully charged as well.

Not sure why my alternator is putting out less voltage at idle, although maybe it should be and I'm overthinking this whole thing.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Re: Can older batteries hurt an alternator?

Measure the voltage of the battery after it has been sitting for a couple hours and any surface charge has dissipated. If you are measuring 13V, you must have just pulled them off the charger.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: Can older batteries hurt an alternator?

Your alternator is working fine. It is doing exactly what it is supposed to do and the numbers are perfect.
 

MakoNY

Petty Officer 2nd Class
Joined
Dec 27, 2007
Messages
110
Re: Can older batteries hurt an alternator?

Thanks for all of the input and answers, I really appreciate it.

I took both batteries up to Advance Auto to get load tested because my multi-meter was showing them at 12.0 and 12.1 while the analog meter on my load tester was showing them sitting at 13.0 and 13.1 and they are load testing fine on that gauge too, so there was a full volt discrepancy between the two. I didn't know which one was incorrect/correct so I figured I'd let Advance Auto be the tie breaker.

They hooked their load tester and before they did any testing one battery showed at 12.8 and the other at 12.7, so I know my multi-meter is most likely shot as the load tester was closer. So the voltage is perfect for both batteries, but then they did the load test.

The batteries are rated at 1100 MCA, so that's what they punch into the machine, then it does a load test. For one it said the actual MCA was 856 and the Result was to Replace Battery, and the second one load tested at 861 MCA and the obviously the result was the same.

So now my question is do I replace these batteries because the MCA tested low? 856 and 861 doesn't seem too bad to me and my engine has no problem at all starting and firing right off. As mentioned earlier I've tested specific gravity on all cells with a hydrometer on both batteries and they all test Good, no shorted or low cells, all are exactly the same.

I figure 1100 MCA is probably not true unless the battery is brand new (and maybe not even then) and since I think these batteries sat for a year and were never charged properly until I got them, they may be a little weak but again that MCA doesn't seem too bad to me. I assume the Amp Hr rating has gone down as well on these batteries, correct?

What would you guys do, replace these or keep them? Will having the lower MCA affect/hurt my new alternator at all, or is it strictly the cranking amperage that is affected. 12.7V and 12.8V seems pretty perfect to me, so I'm not sure if that's all that will affect the alternator or if the MCA will also.

Thanks again for all of the answers and any and all input is appreciated. Trying to learn as much about batteries as I can.
 

Cricket Too

Lieutenant Commander
Joined
May 14, 2003
Messages
1,732
Re: Can older batteries hurt an alternator?

I am having the exact same issue as this, except I have now gone through 2 alternators in 2 months. My batteries are doing the same thing, never get fully charged on a charger but hydrometer shows them all good, they also load test fine. Can weak batteries actually cause an alternator to go bad?
 

generator12

Senior Chief Petty Officer
Joined
Jul 9, 2010
Messages
666
Re: Can older batteries hurt an alternator?

Try that charger on your car battery and see if it shuts off when full charge is reached. The charger itself might be misleading you.

As to two batteries in parallel - remember, if one is unable to attain full charge, the other will keep discharging into it until equilibrium is established. You need to find out whether your charger is working right, and if it is, you have a problem with one or both batteries.
 
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