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ContinuousWave: Small Boat Electrical
Recommended Brand of Smaller, Sealed Battery
|Author||Topic: Recommended Brand of Smaller, Sealed Battery|
posted 10-10-2010 02:53 AM ET (US)
I've got a Dauntless 15 with two batteries wired together with no switch. After pulling them out today to look them over, I realized that one is dead--good thing I pulled them! Now I have to find a new battery. Can I use a smaller sealed battery? If so, what type and brand do you recommend?
posted 10-10-2010 10:07 AM ET (US)
I do not recommend you continue to use a primary power distribution system with two batteries permanently wired in parallel. You should consider installing a main battery switch to control the battery selection.
You need to select a battery based on the requirement for starting your outboard motor. Typically the owner's manual will give information on the minimum battery capacity needed for starting the motor. You should purchase a battery that meets or exceeds the minimum specification.
In general, sealed batteries will tend to be larger in physical size than a conventional battery of the same capacity.
If you provide the minimum recommended battery capacity in marine cranking ampere rating (MCA) we can offer some suggestions.
posted 10-10-2010 10:36 AM ET (US)
Once you have determined the battery needed for starting your engine you will probably get better results by installing matching new batteries with the previously mentioned battery 1/2/off/both switch and isolator.
posted 10-10-2010 04:59 PM ET (US)
Definitely get a battery switch. If one battery goes dead in your setup, you are just dragging the good one down. I have 2 Delco maintenance-free batteries on an off-1-2-both switch.
I know some guys don't like maintenance-free batteries but in that small console with that small door it is too hard to maintain the batteries.
I got my batteries from a guy here that sells batteries to commercial crabbers and golf courses for golf carts. He has no problems with maintenance-free batteries.
posted 10-10-2010 06:07 PM ET (US)
What is the downside of having the setup I have now?
(besides the "dragging down" of the good battery)
I think the battery I pulled out that was bad, was this way for a while. It read 9.3 volts. I have it on a charger now to see if it can be recovered. I have a feeling that it will not be possible....
posted 10-10-2010 06:25 PM ET (US)
The downside of your current set up is that you essentially have a single 12 volt battery with six extra cells. If one battery goes down it will drag the remaining battery down with it. That will eliminate the benefit of having dual batteries on your boat; redundancy.
The value of a redundant battery on a boat is self evident. If you're away from shore and your starting battery lacks sufficient energy to start your engine you only have to switch to the redundant battery to start the engine thus preventing the need to be jump started where you are or being towed back to shore.
If you decide to follow the advice provided in this thread consider two new AGM batteries for your console. AGM batteries are virtually maintenance free for their entire lives. They never require the addition of water. Because they virtually never vent gasses battery terminal maintenance is not required.
Get the switch if you do nothing but replace your bad battery with a similar one. It's really a no brainer.
posted 10-10-2010 08:26 PM ET (US)
The only spec in the BF50 manual I can find is - 12V / 70AH. Is this the spec I am looking for?
Thank you again for the input.
posted 10-10-2010 09:59 PM ET (US)
The specification of "70 AH" likely refers to Ampere-hours. Ampere-hours are a measure of the storage capacity of the battery for discharges that occur over a 20-hour period, nominally. For engine starting, batteries are typically rated by the amount of current they can deliver for a short duration, as occurs when cranking over an engine.
A 70-Ampere-hour battery would be able to deliver a current of 3.5-amperes for 20-hours. Exactly how much current it can deliver during engine cranking would be determined by the battery itself, how it was made, its state of charge, and so on.
Looking at some typical batteries from Interstate
we see that their model SRM-24 can deliver 690 MCA. At a discharge rate of 5-amperes the battery can deliver that current for 16.4-hours, thus 82-Ampere-hours. This battery may rate even more than 82-A-h if figured at the 20-hour discharge rate. For starting a typical 50-HP outboard a MCA rating of 690 likely more than needed, so this battery should be good.
I mention the Interstate brand only because I am familiar with their specifications. There may be many choices that will meet your criterion.
posted 10-10-2010 11:06 PM ET (US)
SEARS sells a nice line of marine batteries, including some AGM premium batteries. They are frequently offered at a reduced price, and, in fact, this weekend are selling at $15 off normal price, on-line only:
http://www.sears.com/shc/s/s_10153_12605_Automotive_Batteries+&+ Chargers_Marine+Batteries?viewItems=24&pageNum=1& sortOption=ORIGINAL_SORT_ORDER&&filter=storeOrigin|Sears& lastFilter=storeOrigin#viewItems=24&pageNum=1& sortOption=ORIGINAL_SORT_ORDER&&filter=storeOrigin|Sears& lastFilter=storeOrigin&adCell=W3
posted 10-12-2010 12:54 AM ET (US)
Thank you for the replies! How about these batteries -
http://www.dekabatteries.com/assets/base/0245.pdf? The group 24 seems to have similar specs to the one Jim recommended and can be had for $160.
Also, after doing some reading on dual battery setups, it seems like a lot of these are set up to isolate on battery for starting. The only electronics I have on board are my lights (which I never turn on) and my VHF radio that is on for a few minutes a trip. I only boat recreationally every couple of weeks or so. So do I really need a dual battery setup? What if I get one good AGM battery and carry one of those portable jump starters?
posted 10-12-2010 08:48 AM ET (US)
The principal reason for having two batteries is for redundancy in engine starting. If you can pull-start your engine--I think you have a HONDA BF50--then the need for a second battery for engine starting is reduced. Some engines will not start or run without a properly charged battery connected. Refer to your owner's manual to learn if your engine requires a battery to be connected to run. If your engine needs a battery to run, you probably want to have two batteries.
I do not endorse the concept of carrying around an auxiliary battery for jumping to the main battery. Often when connecting an auxiliary battery using the clumsy spring-loaded clips there is sparking, and the connections that result are not very good. If you want a second battery, I recommend installing one and having a primary power distribution switch to select between them.
posted 10-12-2010 02:30 PM ET (US)
My engine can be pull started. I will probably move to a single battery setup.
What do [readers] think about the battery I mentioned in my previous post? It looks like a really good deal at $160. Please let me know if you think this will work for my boat.
Or should I go with the group 27? Does the AGM battery have to be 20% oversized?
posted 10-12-2010 10:10 PM ET (US)
The INTERSTATE Group-24 flooded cell battery is about $80, or half the price of the Dekka AGM battery you are considering.
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