Battery volts vs cranking power?

[rebars1]

One of my batteries will read about 12v on my multimeter, but not be able to crank the engine (Johnson 60hp). Is this a sign that the plates are used up?

 

[NYBo]

Re: Battery volts vs cranking power?

At an even 12 volts, the battery is only at 40% to 50% charged. If that's the maximum it will reach, it's shot; no further testing is needed. If it will reach a full 12.6 volts, you need to have it load tested. Most auto parts stores can do this for you for free. If the battery checks out, the problem lies with the battery connections and/or the motor (starter, etc.)

 

[cyclops2]

Re: Battery volts vs cranking power?

A 13.6 vdc Battery is what I have all the voltage regulators set to. Cranks scarry fast. Do not even hear the compression peaks slowing it down.

 

[Bondo]

Re: Battery volts vs cranking power?

One of my batteries will read about 12v on my multimeter, but not be able to crank the engine (Johnson 60hp). Is this a sign that the plates are used up?

Ayuh,... You Can't test crankin' amps with a multimeter, ya need a battery Load tester...

 

[rebars1]

Re: Battery volts vs cranking power?

Thanks for the input. Looks like it is time for a new battery. What type/brand battery would be recommended for infrequent (2-3 moths) use?

 

[Scott Danforth]

Re: Battery volts vs cranking power?

batteries will self discharge at between 4 and 8% per month from non-use. I would recommend any quality marine battery, with a good maintenance charger.

 

[cyclops2]

Re: Battery volts vs cranking power?

Just to confuse all of us. & the expert battery company engineers.
I have a 2002 Chaparral with a V8 & the ORIGINAL battery in upstate N Y. Run the boat about 10 hours each summer. Marina disconnects the battery for the winter.
They DO NOT do any type of charging during the winter.
I DO ADD water every spring after a FULL RECHARGING is complete.


How come it still cranks fine? It does start quick for a bone dry carb system. Restarts are 1 second.

It should have died long ago. Right ?

 

[joed]

Re: Battery volts vs cranking power?

What voltage does it read while attempting to crank? If it stays at 12 volts then you have a different issue than the battery.

 

[Silvertip]

Re: Battery volts vs cranking power?

Just to confuse all of us. & the expert battery company engineers.
I have a 2002 Chaparral with a V8 & the ORIGINAL battery in upstate N Y. Run the boat about 10 hours each summer. Marina disconnects the battery for the winter.
They DO NOT do any type of charging during the winter.
I DO ADD water every spring after a FULL RECHARGING is complete.


How come it still cranks fine? It does start quick for a bone dry carb system. Restarts are 1 second.

It should have died long ago. Right ?

It does so because y0u have been extremely lucky.

 

[Silvertip]

Re: Battery volts vs cranking power?

What voltage does it read while attempting to crank? If it stays at 12 volts then you have a different issue than the battery.

I agree. Don't dash out to buy a new battery until you "prove" the one you have is actually bad.
1) Charge it
2) Connect the voltmeter directly to the battery.
3 Observe the voltage while attempting to crank the engine. If voltage stays at 12+ you do not have a battery issue but rather a soelnoid, wiring, or starter issue. If the voltage drops well below 12 volts you may have a battery issue OR it may be a bad starter. Try another battery. If it does the same thing, look for a starter.

Any auto store in town can load test your battery for you. Make sure its fully charged for the test.

 

[MH Hawker]

Re: Battery volts vs cranking power?

A 13.6 vdc Battery is what I have all the voltage regulators set to. Cranks scarry fast. Do not even hear the compression peaks slowing it down.

Perhaps I don't understand battery's, but from what I know about them the battery voltage on a new one is between 12.5 and 12.8 volts fully charged, open circuit. And its cranking amps that effects how fast it turns a motor around say 400 CCA versus 1000 CCA and I realize its what is avable not what is used or needed , and charging voltage is 13.2 to 13.6.

 

[cyclops2]

Re: Battery volts vs cranking power?

Rare but it happens.

Your charger is not good anymore.
We had the community charger go bad the thing would charge & show green @ 100 %. Was only doing a lot less. Fortunately our NAPA guys do a charge & load test before selling batteries. We like our NAPA guy !!

 

[cyclops2]

Re: Battery volts vs cranking power?

A little basics about car type batteries.

IF......IF your battery holds at 12.1 or 12.2 while cranking, that.. LETS...the starter motor pull... AS MANY AMPS... as it can / or needs.
Can it hold that speed for 30 seconds ?
Everything should be fine with the battery. IF...IF... it is fully charged to start with.
I always check a lead/acid wet cell battery with a meter ...AND....a hygrometer. That squeeze bulb thing with lots of long numbers on it. RARELY does a hygrometer EVERY go bad.
Small plastic or a large BREAKABLE GLASS one. They come with a moving pointer or 5 balls usually. Normally VERY VERY accurate.

 

[bruceb58]

Re: Battery volts vs cranking power?

I always check a lead/acid wet cell battery with a meter ...AND....a hygrometer.

Unless you want to measure the humidity of the air near the battery, you would be best to use a hydrometer!

A battery will be fully charged if it is at 12.6V. If the charger can't get it up to that level, one or more cells is probably bad. Even at 12.6V a battery may not have much capacity left and will drop quickly with a load. Best way to test a fully charged battery is with a load tester which can be purchased at Harbor Freight for $15.

 

[Silvertip]

Re: Battery volts vs cranking power?

Perhaps I don't understand battery's, but from what I know about them the battery voltage on a new one is between 12.5 and 12.8 volts fully charged, open circuit. And its cranking amps that effects how fast it turns a motor around say 400 CCA versus 1000 CCA and I realize its what is avable not what is used or needed , and charging voltage is 13.2 to 13.6.

A 400 CCA battery does not spin a starter any faster than a 1000 CCA battery unless the starter actually requires MORE than 400 CCA to operate. If the starter only draws 300 amps, a 1000 cca battery won't spin it any faster than a 400. it will however, spin it much longer;

 

[cyclops2]

Re: Battery volts vs cranking power?

CCA is a PEAK current ability.

It is not related to duration abilities. The LIFEPO4 batteries used in RC airplanes can & do spin car starters. But the are only the size used in portable work tools. No where near the capacity / duration of boat batteries.

Reserve amperes calculations, is a more accurate way to juggle CCA duration. Remember that battery numbers are UNDER THE BEST LABORATORY conditions. You will get less power than they did.

 

[MH Hawker]

Re: Battery volts vs cranking power?

400 CCA versus 1000 CCA and I realize its what is avable not what is used or needed

thats what I said

 

[bruceb58]

Re: Battery volts vs cranking power?

CCA is a PEAK current ability.

Actually, its not quite peak current. The rating is the amount of current that can be produced for 30 seconds @ 0?F before the battery voltage drops to 7.2V. Its a combo of peak current and capacity to keep outputting that peak current.

Reserve amp calculations have absolutely nothing to do with CCA ratings either as its more a capacity rating.

Read here for some accurate info for CCA and Reserve capacity
http://www.autobatteries.com/faq/index.asp

Another thing, a charger can bring up a battery to full charge and the battery can fail a load test. The charger will still be good. If the battery capacity is low because of age, it will still fully charge.

 

[UncleWillie]

Re: Battery volts vs cranking power?

... will read about 12v on my multimeter...

What is "About"?.
Measuring 12.4 or 12.8, makes a huge difference.

... Connect the voltmeter directly to the battery... Observe the voltage while attempting to crank the engine...

Not so obvious to the layman.
When it says "Measure the Voltage at the battery", It means that quite literally.

Place the meter leads on the Battery Terminal Posts that are molded into the battery.
NOT on the Battery Clamps attached to the Battery Posts, or the wire one inch away, Directly On The Battery Posts!
Yes, it does make a difference!

For example.
If the Battery Post itself measures 12.4 volts while cranking the engine, and the Battery Clamp, a quarter of an inch away, measures 8.5 volts, you have a bad connection between the Battery Post and the Battery Clamp!
A two Minute fix. Just clean it up!

If you only measured the Battery Clamp and saw the 8 volts, you would have improperly assumed the battery was bad.
In the process of replacing the battery, you would likely have resolved the bad connection issue without even knowing it, and replaced a perfectly good battery for no good reason.

When charging the battery, expect to see more than 14 volts. And hopefully less than 17!
You can "Maintain" at 13.6. But it will take forever and a day to actually charge at that voltage.

If you see 14+ volts at the battery posts with the engine reved up, the alternator (or charger) is charging the battery!

 

[sschefer]

Re: Battery volts vs cranking power?

Thanks for the input. Looks like it is time for a new battery. What type/brand battery would be recommended for infrequent (2-3 moths) use?

Take a close look at all the batteries at Wal-Mart, O'Reily's, Advanced Auto, etc. Bets are that 90% at least are made by Johnson Controls. This is something I just discovered after calling Johnson with a question about the Optima's. Since your basic Marine Start/Deep Cycles are all pretty much the same no matter what the brand name the only disclaimer is "Proper Maintenance".

A 60hp Johnson should be fine with a group 24 battery rated at 750 CCA and a RCA of 90 minutes or better. RCA's are important if you run a fishfinder and other accessories when the engine isn't running. Your troubles will be in the proper maintenance area. Talk to the folks at Interstate or Johnson. They'll tell you how to properly maintain their batteries to attain maximum lifetime.