Battery question

musella

Seaman Apprentice
Joined
Mar 20, 2005
Messages
34
Hi.<br /> I have a new 2005 (50 hours) 5.0l Mercruiser I/O on a 23' Caravelle WalkAround.<br /><br /> Last night, while watching the fireworks and bass fishing, I drained one of my batteries. I have dual batteries, and usually have it set to BOTH, but when I anchored, I switched it to use only Battery 1, to make sure I don't drain both batteries while running my TV, Lights, etc:)<br /> When I went to start it, there wasn't enough juice left in battery 1 to start the engine. I switched it to BOTH and it worked fine.<br /> The question:<br /> How long does it take for this engine to recharge a battery? I take many short trips and rarely run at high speed for more than 5 minutes a day. Would it recharge enough just letting the engine idle? How long?<br /><br />thanks<br />Al
 

amirm

Petty Officer 2nd Class
Joined
May 7, 2005
Messages
176
Re: Battery question

To figure out the amount of time it takes to charge the battery, you would need to know how much capacity it has and what its maximum charging rate. You would also need to know the alternator output of your engine. A quick search shows your alternator to be rated at 65 amps although I very much doubt that it can put out this much current at higher temps or for too long. So safe bet would be 30 to 35 amps. <br /><br />If your battery is rated at say, 200 amps capacity, you would need about 6 to 7 hours at full throttle to fully charge it. I can not find the idle charging current on your engine. It is probably under 10 amps so you need to at least tripple the above number to charge at idle.<br /><br />All in all, I highly recommend that you charge the battery with an external A/C unit and not rely on it being charged by itelf. Leaving partly charged battery out there will cause it to self destroy itself over time.<br /><br />Amir
 

musella

Seaman Apprentice
Joined
Mar 20, 2005
Messages
34
Re: Battery question

thanks.. looks like I have to get an battery charger!
 

musella

Seaman Apprentice
Joined
Mar 20, 2005
Messages
34
Re: Battery question

I was looking around.. and just have a couple of questions before I buy it..<br /><br />1. How easy is it to install? <br />2. I am looking at Guest Waterproof Battery Chargers Pro and need to pick a model. I am assuming that the only difference between the 3 2-bank chargers is the amount of time it will take to recharge a battery? I am planning on letting it charge overnight, so speed doesn't matter - dose it?<br />3. How often should it be used? I use the boat about 5 times a week, but most of those trips consists of starting and stopping the engine frequently with no more than a few minutes of low speed driving.<br /><br />thanks.
 

amirm

Petty Officer 2nd Class
Joined
May 7, 2005
Messages
176
Re: Battery question

Installation is fairly simple but mistakes could be dangeours and life threatening as you are dealing with seriously high currents here. If you have no electrical background, I don't recommend that you attempt it. Otherwise, it is a rather simple affair of matching polarities on the output of the charger to the battery and finding a dry place to mount the unit. You would also need to use sufficiently large wires to carry the necessary current (12 guage should be fine). The only (minor) complication might be where to connect the charger wires, if you don't have an empty terminal some place.<br /><br />And yes, the lower the current, the longer it takes to charge the batteries. The 10 amp one seems cheap and can handle two batteries which is a good baseline. Note that it may take up to 24 hours or more if both of your batteries are empty with this unit.<br /><br />Since these are smart chargers, they can be left on all the time with no worries. Ideally, you would leave them on when the boat is not in use. Batteries self discharge at 4% per month so even sitting there, you lose charge. But practically speaking, if you are using the boat frequently and run the gear with the engines on most of the time, I would not bother with the charger. But if you ever get in the situation that you mention here, then you should hook it up. And if you don't use your boat for a while, do the same.<br /><br />Amir
 
Top