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Author Topic:   Engine Starting Battery for OptiMax
Mambo Minnow posted 02-17-2007 08:06 PM ET (US)   Profile for Mambo Minnow  
I have two New Castle brand Marine/RV, Group 24, Deep Cycle, wet/lead acid batteries at rated 790 Marine Cranking Amps for my 200-HP Optimax. No CCA rating listed. Original owner purchased them. The month/year markings were not punched out so I can only guess worst case, the batteries are six-seven years old.

I am doing my annual maintenance this weekend. Pulled batteries out of boat, topped off cells with distilled water and put on a 10 amp charger. Charger reading a 100% charge after only an hour charging. My battery voltage gauge on boat reads around 13 volts (halfway bet 8 and 18). I have had no power problems onboard the last year, but I am taking a long trip to Keys next month. Just how long can a traditional lead acid battery last?

1. Wonder if these batteries are enough juice given the well known Optimax 800/1000 CCA/MCA requirement? I guess I should always start with Perko switch in "all" to ensure adequate starting power from two batteries. I like to start in "all" and then switch to "1" outbound and "2" inbound legs of daily trips.

2. Is Deep Cycle better application than Starting a battery? My Mercury manual does not require one or the other. I do like to keep my GPS, Fishfinder and VHF powered on when at anchor fishing but I doubt if they draw much power. As a precaution, I normally stay in "1" or "2" at anchor in case of a severe discharge.

I have read all the posts in search regarding the AGM and Optimax minimum requirements. Seems like JimH is a proponent of the traditional lead acid battery vs. AGM. I am in no hurry to replace these unless someone thinks these are the wrong battery type installed in first place.

jenkinsph posted 02-18-2007 11:43 AM ET (US)     Profile for jenkinsph  Send Email to jenkinsph     
If you have them out of the boat why not have them load tested at your supplier. Most places will do this free and you can pickup new ones if needed in one trip.


jimh posted 02-18-2007 12:04 PM ET (US)     Profile for jimh  Send Email to jimh     
I offer the same advice as Steve. Most battery retailers now have on-hand some sort of battery test instrument which can make a meaningful assessment of your battery's state of charge and capacity by only a very brief and modest discharge test.

If you have doubt about the accuracy of the test results from such a device, request the retailer test a new battery from his shelf. You can then compare the results.

In the overall cost of boating, a new battery is a modest expense, even for a fancy $150 VRLA AGM cell with a popular brand name. A flooded cell lead-acid Interstate cranking battery with 1,100-MCA rating sold at a boat store is only $80 to $90. You should consider the cost of that investment in terms of the returns it will bring when your engine starts easily the next time you are 30-miles away from your home port.

If you cannot easily pull-start your outboard motor, it will be necessary to have an engine starting battery in excellent condition on board, and also quite likely to have a back-up battery as well. If you cannot start your engine your boating enjoyment is going to be very low.

Mambo Minnow posted 02-18-2007 12:06 PM ET (US)     Profile for Mambo Minnow    
I had only one of the two out yesterday, since I have only one charger. After, 2 hours on Fast Charge (10 amps) and trickle charge (2 Amps) 12 hours overnight in garage, the multimeter is reading 12.2 negative. Based on JimH's excellent reference article, that's 50% discharged. The second is reading 12.65. I don't think I can get them to hold a higher charge.

I decided this morning to pull the second battery and do exactly what you suggested. The other advantage to pulling out of the confined boat space was I found the old fashioned "B0" sticker on the side of the battery. This confirms my thought that these batteries go back to February 2000. Time for a change or with my luck they will be dead next month in the Keys!

Love the great reference section! I have learned so much from this site over the years. Thanks JimH!

jimh posted 02-18-2007 01:25 PM ET (US)     Profile for jimh  Send Email to jimh     
I think we have the same charger--10-amp and 2-amp.

Your charging was

2-Hours X 10-Ampere = 20-Ampere/Hour
12-hours X 2-Ampere = 24-Ampere/Hour

which implies you gave the battery 44-Ampere/Hours of charge.

In actual results you probably only achieved about half of that or less. The charging current tends to taper off as the battery terminal voltage rises, so the 10-Ampere rate charge tapers off to just a few amperes, and the same for the 2-Ampere charge, which tapers to just a trickle.

If the charge rate is down to about 0.5-Ampere, which might be typical when the battery voltage has risen some and the charger output is set to the 2-Ampere rate, then it will take more like 100-hours of charging to put 50-Ampere/Hours into the battery. A typical Group-24 size lead-acid flooded cell battery will have a capacity for around 50-Ampere-Hours.

The state of charge is one parameter, but the capacity is another. As a battery ages its capacity will drop. The battery can still reach a terminal voltage which indicates a full-charge, but the battery will have very little capacity to deliver current. The lead plates of the battery become covered with other chemical deposits (oxides) and fail to provide their original capacity. Or the lead plates flake off and fall into the electrolyte and to the bottom of the cell.

The capacity is typically a function of the amount of lead plate surface area available.

The last marine cranking battery that failed on me showed a full-charge terminal voltage, but the battery dropped to complete discharge after about five seconds of engine cranking. That failure cost me a whole day of boating and wasted about 150-miles of driving around with the boat in tow. At 10-MPG, I wasted as much money on gasoline as a new battery cost.

Mambo Minnow posted 02-18-2007 05:48 PM ET (US)     Profile for Mambo Minnow    
I took the two batteries to my local auto hobby shop and a friend tested with his digital load tester. The LED readout for each 790 MCA battery showed only approx 632 MCA and read "replace battery". Seven years for those batteries was outstanding, though.

So off I go shopping. Interesting results for the discerning shopper. Optima blue tops were prevalent at all retail outlets, averaged $199 each. Best price on the Blue Top I found was Pep Boys at $189 each.

Sears was disappointing. Their only Group 24 deep cycle on the shelf had a paltry 500 MCAs...too small a margin for even two in series on an Optimax. NAPA, Autozone and WalMart had Group 24s averaging approx 625 MCA.

Looks like I am going to go back to Worst Marine. They had a starting battery at 1000 MCA (only one I could find that high) and a deep cycle in the 665 MCA range. I am going to buy one of each and label the starting and house circuits on the Perko 1-All-2 switch. This should cost approx $214.

If I wanted two deep cycles again, I would go with the Optimas, but JimH's AGM reviews have not sold me on spending $400 for two batteries, particularly when I don't expect to be able to boat as much after this summer due to work travel commitments

jimh posted 02-19-2007 09:44 AM ET (US)     Profile for jimh  Send Email to jimh     
Try WALMART. They have decent flooded cell lead-acid marine-style batteries.

Interstate makes an 1,100-MCA battery for marine applications.

jimh posted 02-19-2007 09:56 AM ET (US)     Profile for jimh  Send Email to jimh     
Re any imputed endorsements by me regarding batteries:

I don't really have a strong opinion about AGM batteries. They have some nice qualities, but price and (apparently) long life are not among them. They are roughly twice the price of flooded cell batteries and they do not seem to have a long life span, particularly when subjected to charging from an outboard motor whose voltage regulation may not be as well controlled as the AGM battery would like. A further drawback on some AGM batteries is the terminal post configuration. They tend to use a 1/4-inch post, which is smaller than the terminal configuration on most boat primary battery distribution cables.

If I were choosing a battery for a military jet fighter plane, an AGM would be a much better choice than a flooded cell lead-acid battery. An AGM would be lighter, it could be turned upside down and not spill, and it could probably keep working even if the case were penetrated by a shell. But on my boat I don't really worry if the battery weighs 10-lbs more, and I do not anticipate it being operated upside down. We have met a few hostiles while boating, but so far we have not taken any fire, so I am not too worried about a shell hitting the battery and taking us out of action.

Mambo Minnow posted 02-19-2007 06:11 PM ET (US)     Profile for Mambo Minnow    
Thanks JimH. I tried Wal-Mart, but not much selection in higher MCAs. I will pursue an Interstate retailer, since I have not checked them out yet.
Mambo Minnow posted 03-12-2007 05:10 PM ET (US)     Profile for Mambo Minnow    
After a great deal of market research, I went with a 1000 MCA West marine starting battery and a Wal-Mart Everstart Marine 650 MCA deep cycle for the house circuit. Both lead acid, the starting maintenance free.

For Opti owners, this was the West Marine was the most powerful starting battery I could find in a maintenance free. I had access to two Optima Blue Tops, but I decided the cost/benefit ratio was not good enough to justify at this time.

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