Main Battery: Number of Starts

[Robert Sands]

Hi everyone,

I have a dual battery install on my 195 HO Impulse. I generally start the engine of the boat using the main deep cycle battery that the boat originally came with. I have both batteries on a marine charger, but I don't plug it is as much as I should.

The other day when my girl took the boat out she noticed the battery light come on for the main cranking battery. We do a lot of tubing and wakeboarding, which requires a lot of starts and stops. I'm wondering how many starts do you think the main crank battery has in it before it should be charged?

 

[luanders]

I run my main battery all day pulling kids tubing, boarding, etc and never have an issue - and I run a medallion screen and 1000 watts for the amps. I have a second as backup though

 

[subysti]

you shouldn't use a deep cycle battery for starting. Deep cycle batteries and starting batteries are designed differently. The deep cycle is designed for long slow draw where a start battery is designed for fast high amperage output. You will kill a deep cycle if used for starting and a starting battery wont last as long when used for a house battery. Deep cycle batteries have fewer thicker internal plates and can be drawn down to almost 75% discharge without damage. A starting battery has more thinner plates and when drawn down too far it will be damaged over time and not take a full charge any more.

 

[swatski]

you shouldn't use a deep cycle battery for starting. Deep cycle batteries and starting batteries are designed differently. The deep cycle is designed for long slow draw where a start battery is designed for fast high amperage output. You will kill a deep cycle if used for starting and a starting battery wont last as long when used for a house battery. Deep cycle batteries have fewer thicker internal plates and can be drawn down to almost 75% discharge without damage. A starting battery has more thinner plates and when drawn down too far it will be damaged over time and not take a full charge any more.

You can use a deep cycle battery as your cranking battery. In fact, I would not use anything else in a Yamaha JB.

There are specific instances where that does not apply, I believe Verado o/b for instance, which may crank but not start with a deep cycle. This is because the ecm needs more volts to operate, a deep cycle may have enough voltage to spin the starter, but not simultaneously run the ecm, or soemthing like that. But that is a very specific issue with Mercs I believe.

Most motors will start fine of a deep cycle battery because most of them put out enough cranking amps to start most motors. There are some deep cycle batteries that do not put out many cranking amps and they will not start bigger motors.

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[subysti]

I'm not saying it won't work but you will be replacing the battery often. There is a reason one is for starting and one for deep cycle. Research it a little. Many deep cycle batteries have enough amperage to start an engine but they just aren't designed for this use. The high current fast discharge of starting an engine damages the plates of a deep cycle battery. After time you will kill it.

 

[swatski]

I'm not saying it won't work but you will be replacing the battery often. There is a reason one is for starting and one for deep cycle. Research it a little. Many deep cycle batteries have enough amperage to start an engine but they just aren't designed for this use. The high current fast discharge of starting an engine damages the plates of a deep cycle battery. After time you will kill it.

I think this is about as unbiased as it gets:
http://www.nyc-arecs.org/deep.pdf

"Deep Cycle Battery as a Starting Battery

There is generally no problem with this, providing that allowance is made for the lower cranking amps compared to a similar size starting battery. As a general rule, if you are going to use a true deep cycle battery also as a starting battery, it should be oversized about 20% compared to the existing or recommended starting battery group size to get the same cranking amps. That is about the same as replacing a group 24 with a group 31. With modern engines with fuel injection and electronic ignition, it generally takes much less battery power to crank and start them, so raw cranking amps is less important than it used to be. On the other hand, many cars, boats, and RV's are more heavily loaded with power sucking "appliances", such as megawatt stereo systems etc. that are more suited for deep cycle batteries.
It will not hurt a deep cycle battery to be used as a starting battery, but for the same size battery they cannot supply as much cranking amps as a regular starting battery and is usually much more expensive."

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[Robert Sands]

Thanks guys, much appreciated. That helps me a lot.