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Old 23-10-2024, 02:48   #1
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12V Battery voltages

I tried to start the Perkins 4 108 motor just a few hours ago. All I could hear was a whirring sound. I assume therefore the solenoid hadn't worked to engage the flywheel. I suspect low battery voltage would cause that?

I am using X2 12V batteries in series. When I checked the voltages of the batteries the aft battery read 16.1V and the other battery it read 12V. Initially I thought the high reading was because the solar panels were still connected but when I switched them off the readings remained the same.

I started reading other threads and I have concluded this is not an uncommon problem but there were various differing reasons.

The history of the two batteries is a bit vague but they have been OK for the last two years.

I am going back to the yacht tomorrow morning so I would appreciate any advice you may have.

PS I do have a battery tester on board but I have no idea how to use it. However my son has offered to help but that won't be until the w/e
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Old 23-10-2024, 03:49   #2
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Re: 12V Battery voltages

If the connection between the two batteries was "dirty" could the 24V alternator (or 24 solar charge) boost the voltage of one battery around 16V and leave the second battery with just a 12V charge.
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Old 23-10-2024, 05:21   #3
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Re: 12V Battery voltages

When charging is one battery hotter than the other, use a temp gun or the back of your hand.



Disconnect/isolate the batteries and read the voltage after 5 minutes. What volts do you get?
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Old 23-10-2024, 06:31   #4
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Re: 12V Battery voltages

Quote:
Originally Posted by coopec43 View Post
I tried to start the Perkins 4 108 motor just a few hours ago. All I could hear was a whirring sound. I assume therefore the solenoid hadn't worked to engage the flywheel. I suspect low battery voltage would cause that?

I am using X2 12V batteries in series. When I checked the voltages of the batteries the aft battery read 16.1V and the other battery it read 12V. Initially I thought the high reading was because the solar panels were still connected but when I switched them off the readings remained the same.

I started reading other threads and I have concluded this is not an uncommon problem but there were various differing reasons.

The history of the two batteries is a bit vague but they have been OK for the last two years.

I am going back to the yacht tomorrow morning so I would appreciate any advice you may have.

PS I do have a battery tester on board but I have no idea how to use it. However my son has offered to help but that won't be until the w/e
order this https://www.aliexpress.com/item/1005...238118024trg4d
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Old 23-10-2024, 06:58   #5
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Re: 12V Battery voltages

I saw some threads on other forums where unusually high voltage readings were due to low batteries in the multimeter itself. Perhaps try with fresh batteries or a second meter?
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Old 23-10-2024, 08:51   #6
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Re: 12V Battery voltages

Quote:
Originally Posted by coopec43 View Post
I tried to start the Perkins 4 108 motor just a few hours ago. All I could hear was a whirring sound. I assume therefore the solenoid hadn't worked to engage the flywheel. I suspect low battery voltage would cause that?

I am using X2 12V batteries in series. When I checked the voltages of the batteries the aft battery read 16.1V and the other battery it read 12V. ...
If the batteries are connected in series should the battery voltage be over 24 volts? I have two batteries connected in parallel and they will read around 12.5ish volts.

Sounds like either the batteries are dead/dying or there is a connection issue between the batteries.
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Old 24-10-2024, 00:45   #7
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Re: 12V Battery voltages

Quote:
Originally Posted by Tin Tin View Post
When charging is one battery hotter than the other, use a temp gun or the back of your hand.



Disconnect/isolate the batteries and read the voltage after 5 minutes. What volts do you get?

They both seem to be cool while charging.

I have the batteries at home now. I have had the stern battery on charge and it now reads 12.7V

The other battery is now on charge and currently reading 11.7V

Instructions from my Son is to keep charging and he will load test both tomorrow (Having read the instructions I realize now that I could easily use the load tester myself)

I think I'm up for one new 700cca battery
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Old 24-10-2024, 00:52   #8
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Re: 12V Battery voltages

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Originally Posted by coopec43 View Post
They both seem to be cool while charging.

I have the batteries at home now. I have had the stern battery on charge and it now reads 12.7V

The other battery is now on charge and currently reading 11.7V

Instructions from my Son is to keep charging and he will load test both tomorrow (Having read the instructions I realize now that I could easily use the load tester myself)

I think I'm up for one new 700cca battery

Won't you need two - is it not a 24V system? - mxing old and new batteries in series is not recommended
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Old 24-10-2024, 01:52   #9
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Re: 12V Battery voltages

Quote:
Originally Posted by Tin Tin View Post
Won't you need two - is it not a 24V system? - mxing old and new batteries in series is not recommended
Exactly.
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Old 24-10-2024, 04:00   #10
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Re: 12V Battery voltages

Quote:
Originally Posted by Tin Tin View Post
Won't you need two - is it not a 24V system? - mxing old and new batteries in series is not recommended

I thought someone would raise that point. I can understand it if the batteries were being run in parallel but I am running them in series. I did a google and came up with this.

Can you connect different brand batteries in series?
To ensure optimal performance and safety, it is best to use batteries of the same type and rating when you can. This means not using batteries of different brands together. But if you really must, make sure to check and compare so that the type and ratings are similar or as close as possible.24 Aug 2023

The present system has been in use for several years and the batteries were secondhand when I installed them
They are starting batteries so don't get used a lot. (The starter motor is 12V but I have installed a 24V solenoid)
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Old 24-10-2024, 05:08   #11
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Re: 12V Battery voltages

WHilst googling check out this site and read the section on different aged batteries in series. https://batteryguy.com/kb/knowledge-...ies-in-series/
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Old 24-10-2024, 06:20   #12
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Re: 12V Battery voltages

Quote:
Originally Posted by Tin Tin View Post
WHilst googling check out this site and read the section on different aged batteries in series. https://batteryguy.com/kb/knowledge-...ies-in-series/

I have one good battery which has charged to 12.6V quite easily. Tomorrow I will load test it.

The other battery is obviously stuffed as I have been charging it for 5 hours and it is only registering 11.8V

Just looking at prices of batteries (and keeping in mind the bank balance) I can buy

X2 SCA 550CCA @ $135 ..............$270

OR X1 Supercheap 700CCA........... $216

I think I'll go for the two SCA batteries. (I hope to goodness I never need to use 550CCA)

I just had a look at the battery I took out of the yacht and it is
"LEAD ACID Sealed Maintenance Free"
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Old 28-10-2024, 07:59   #13
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Re: 12V Battery voltages

In spite of the battery issues, I would look at the starter. Hard to debug "whirring", but it might be that the solenoid is frozen. This has happened to me. If there is enough juice to run the starter the bendix gear should engage. I would tap it with a mallet or remove it and clean any corrosion. It's generally possible to remove the solenoid without taking off the starter.
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Old 28-10-2024, 15:15   #14
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Re: 12V Battery voltages

I suspect that the starter motor is spinning but the Bendix drive remains disengaged. It slides along a thread against a spring, and the thread needs to be lubricated. If it has not been lubricated for some time, this may be the cause.

You will need to remove the starter motor to do it, and while you have it out, you might as well check the motor brushes as well and replace them if worn.

If your batteries are two years old, they may be alright, but there is a chance that they are faulty and that is why they are simply not spinning the starter motor at sufficient speed to operate the Bendix drive. Terminal voltage is not the same as terminal voltage under load.

I replaced mine every two years anyway. An engine that will not start in an emergency is a potential loser of your vessel, and perhaps your life and that of any others aboard at the time.
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Old 28-10-2024, 22:22   #15
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Re: 12V Battery voltages

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Originally Posted by Mike Banks View Post
I suspect that the starter motor is spinning but the Bendix drive remains disengaged. It slides along a thread against a spring, and the thread needs to be lubricated. If it has not been lubricated for some time, this may be the cause.

You will need to remove the starter motor to do it, and while you have it out, you might as well check the motor brushes as well and replace them if worn.

If your batteries are two years old, they may be alright, but there is a chance that they are faulty and that is why they are simply not spinning the starter motor at sufficient speed to operate the Bendix drive. Terminal voltage is not the same as terminal voltage under load.

I replaced mine every two years anyway. An engine that will not start in an emergency is a potential loser of your vessel, and perhaps your life and that of any others aboard at the time.

Thanks for that.

I took both batteries home and tested them under load: one battery is excellent but the other is knackered.

Under instruction from my two diesel mechanics (Son and friend) I bought another battery with similar CCA and they are going to fit them tomorrow. AND my Son has said he will pull the starter motor off and lubricate it.

Thanks for you help.
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