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ContinuousWave: Small Boat Electrical
Battery Rigging for Mercury OptiMax
|Author||Topic: Battery Rigging for Mercury OptiMax|
posted 05-09-2009 04:22 PM ET (US)
I have a [1999 Mercury 150-HP OptiMax motor] on a 22-footer I just bought. The battery setup has a battery switch (OFF-1-BOTH-2) and two batteries, both newer deep-cycle 600-CCA or 750-MCA batteries. I have read that this motor requires [a battery with a rating of a] minimum 800-CCA or 1000-MCA. I have to think about how and if I need to change this set-up.
I can hook in a new starter battery as Battery-1 and leave one deep-cycle with all electronics directly hooked to it as Battery-2. I'm not sure about having all the house appliances (GPS receiver, fish finder, and aerators) hooked into one battery. There's a three-bank charger on board for the two separate trolling motor batteries, and I guess one bank charges both deep cycles in the back.
Is it bad for either the engine or the batteries to have it rigged as is, which is about 1,200-CCA or 1,400-MCA when the battery switch is on "BOTH" (which I assume means they are in parallel)? The engine starts well, so it's not a prolonged large load on the batteries during starts. Is this a bad situation as rigged?
Any advice on this?
posted 05-09-2009 05:57 PM ET (US)
If you now have two batteries, each with a rating of 750-MCA, and if you connect them in parallel (by putting your battery switch in the BOTH position), then you will create a combined battery with a rating of 1,500-MCA. This combined battery will have sufficient rating to meet the demand of the Mercury OptiMax 150-HP motor, which requires a battery with a minimum rating of 1,000-MCA.
There is no particular harm done in this approach. The only limitation of this approach is that neither battery alone has a rating sufficient to start the Mercury OptiMax motor, or their ability to start the motor may be very marginal.
The reason for having two batteries on a boat is to provide redundancy. In your configuration there is not complete redundancy, as you will need both batteries on-line to meet the starting requirements of your motor.
posted 05-09-2009 06:06 PM ET (US)
The primary purpose of the battery on your boat is to provide for engine starting. If your engine cannot be started without a battery, then it is reasonable to provide redundancy in the battery. I assess your current situation as follows:
Can the motor be started without a battery? In the case of the Mercury OptiMax, the answer is no. The motor requires a battery to start, and it also requires a battery to run. A battery is absolutely essential for a Mercury OptiMax motor.
Because a battery is absolutely essential, I would then propose that there be some redundancy in the battery. A battery is not a 100-percent reliable device, and it is reasonable to expect that there may be a situation in which a back up battery is needed or would be extremely valuable.
If neither of your two batteries is capable of reliably starting the engine by themselves, then you should think of them as a single battery. In this view, you boat does not have dual batteries. It has a single battery which is distributed between two separate cases. Essentially, you are operating the boat with one battery.
My recommendation is to replace at least one or both of the engine starting batteries with a new battery that has a rating of at least 1,000-MCA.
Please read your owner's manual for the Mercury OptiMax motor and pay careful attention to the recommendation for the battery. It has been reliably reported here that the manual contains explicit prohibitions against use of a deep-cycle battery for engine starting.
posted 05-10-2009 12:58 PM ET (US)
thanks Jim-- I appreciate the response. i understand the redundancy issue, but I only have room for two batteries, and i need a deep cycle for the electronics. I suspect that if i just replaced one with a dedicated starter battery (in the "1" position) and just used the other deep cycle for electronics, in a situation where the starter battery was low I could switch to "all" and get her started to get back home.
I should note that i never go off shore-- mostly lakes and if salt it's limited to inshore....not interested in going offshore with 22 ft of fiberglass.
posted 05-10-2009 03:30 PM ET (US)
I have an Optimax engine and I run 2 starting batteries each capable of starting my motor on its own. Today's electronics do not draw that much power to demand a deep cycle battery. I stay off of the vhf radio and have installed LED deck lights which draw almost nothing. I run one battery at a time and alternate which one I use so as to keep them both charged. Unless you use an electric trolling motor or some other high-current accessory I would opt for redundancy.
posted 05-10-2009 06:37 PM ET (US)
Thanks-- I'll have to think about that; in addition to the GPS and fish finder, I also run the live wells off the one battery, so I fear I'll be draining a starter while on the water with all that going on. I think the best option would be two starters and the one deep cycle, but not sure where to put the third one!
posted 05-10-2009 07:56 PM ET (US)
As long as your engine is running there is no worry about battery load. When your engine is not running, there should not be any load on the starter battery. Move pumps for live wells to another circuit, not the starter battery.
posted 05-10-2009 08:11 PM ET (US)
I have a 225 Optimx that requires 1000 mca. I use two AGM batteries (start/house) connected to an BEP 716 Battery Management Cluster. The BEP uses an ACR that manages the charging of the batteries. After starting the BEP isolates the start battery to the alterator. When the voltage reaches 13.7 volts the VSR opens letting the alternator charge both the start and house battery. If at anytime the start battery drops below 12.8 volts then the VSR disconnects the house battery from the charging circuit targeting the start battery.
In my configuration I run two chartplotters, two VHF radios, fishfinder, a stereo, and two AC outlets. I've been running this configuration for three years plus and I never drained either battery.
Here are some pictures:
The boat is a 210 Ventura.
I did all the rigging myself ...it's very straight forward and easy to do. Took me two days to complete.
posted 05-11-2009 08:31 AM ET (US)
I have a live well also. My 2005 150 Optimax has a pretty healthy charging system (60 amp). In 2 years I have never had a problem. I will not let the batteries get to old.
I used to run the deep cycle/ starter type batteries in all my boats and I worried about killing my battries with the starter batteries that came with my Eastport,to date I have not had that problem.
posted 05-11-2009 04:36 PM ET (US)
Tom-- that's an exceptional e-rigging job; I'll have that as a future goal (as well as having any compartment on my boat look so clean!). Seems like a perfect set-up for both re-charging and redundancy.
Thanks for the tips and advice, everyone; see you out on the pond!
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