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Author Topic:   Using Battery With Higher Cranking Ampere Rating Than Recommened
lisfisher posted 08-25-2006 10:47 AM ET (US)   Profile for lisfisher   Send Email to lisfisher  
In reviewing my owner's manual on my 1995 75hp Merc , it says the battery recommended is one that has 465 cranking amperes. Now the new battery I just put in has 1,000 cranking amperes. Is this going to cause a problem? I got the battery at one of the boater's chain stores. It was the only size battery they had in stock.
Jerry Townsend posted 08-25-2006 03:06 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
lisfisher - You simply have a battery with more perforamnce capability than is necessary. The amp-hour rating gives an indication of the performance of the battery. The higher the number (product of amperes and hours at that current), the higer the capability of the battery.

With a 75 HP engine, you don't really need a 1000 amp-hour battery - but the only drawbacks - it will have cost more, weigh more, and be somewhat larger - than the 465 amp-hour battery recommended. Generally, the bigger the engine, the bigger the required battery. ---- Jerry/Idaho

swist posted 08-25-2006 03:50 PM ET (US)     Profile for swist  Send Email to swist     
What Jerry said. Don't confuse amps and volts. All batteries are 12 volts, but the load on the battery (amps) is determined by the power needs of whatever you are trying to run, not by the battery.
Chuck Tribolet posted 08-25-2006 10:41 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
No such thing as too much battery, as long as the voltage
is right.


WT posted 08-25-2006 11:14 PM ET (US)     Profile for WT  Send Email to WT     
I run a 1000 amp battery on my 90 hp Mercury four-stroke without any problems.


jimh posted 08-28-2006 08:51 AM ET (US)     Profile for jimh  Send Email to jimh     
There is no electrical downside to using a battery that can deliver more cranking amperes than are needed by the engine. Larger batteries do cost more, and they often weigh more.
lisfisher posted 08-28-2006 08:55 AM ET (US)     Profile for lisfisher  Send Email to lisfisher     
Thanks guys , I just wanted to be sure I wasn't going to hurt my charging/ignition system , as I just spent big bucks having it all replaced. The only thing I run while underway is a depthfinder ,and at night the lights of coarse.While anchored { engine off } I just run the anchor light.
Teak Oil posted 08-30-2006 07:58 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
I also have a 1000 amp battery. I recently left my depthfinder on for almost a month while the boat was in the garage, and the battery still had enough power to start the engine!

Its nice to have the extra capacity if you are in a situation where you need to leave your lights on without the motor or run your VHF for a long period of time in an emergency.

davej14 posted 08-30-2006 08:28 PM ET (US)     Profile for davej14  Send Email to davej14     
If you are intending to use accessories without the motor running for an extended period then be sure to get a deep cycle battery. A starting battery is not designed for significant discharge and will be damaged with a few number of cycles. A deep cycle battery has plates designed for discharge cycling and so long as it has adequate CCA capacity for starting it would be a better choice for running accessories.
lisfisher posted 08-31-2006 01:25 PM ET (US)     Profile for lisfisher  Send Email to lisfisher     
ok , what if the only thing I run when the engine is off is the anchor light? Does this have a significant drain on my cranking battery? It is on { on average } about 4 hrs maximum while the motor is off , about once per week.
alfa posted 08-31-2006 01:57 PM ET (US)     Profile for alfa  Send Email to alfa     
As electrical law, assuming lamp bulb is 10 watts, drain will be 0.84 amperes.

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