When to charge cranking battery?

[NeWcS]

It is my understanding that when I run my Big motor that that charges the battery while im running? I currently have A sonar, GPS, All lights and pumps hooked up to my cranking battery. How long should I be able to run all these things off that bettery before I should start it up to charge? Someone told me to use the Volt meter on my sonar to let me know if it time to charge. Can someone tell be when I should do this? The motor is a 2001, 75hp Merc. The battery is a 1000 crank and 850 cold crank.<br />Last weekend I ran into a dead cranking battery with 40mph winds and 4ft waves and couldnt fire up the big motor. I want to make sure that doesnt happen again.<br /><br /><br />-Jay

 

[Salmonseeker]

Re: When to charge cranking battery?

Hey Jay,<br /><br />I am assuming this battery is made for starting only. Starting batteries are only really designed to start a motor and keep accesories running while the motor is running. If you plan on running your accesories when the main motor is not running you will probally need a different type of battery. <br /><br />I use a a large deep cycle to start my motor and run my accesories. Just make sure the cranking amps are sufficiant for your motor. They also make dual purpose batteries which would work well in your situation. They will start a motor well and have some deep cycle capabilities.<br /><br />I may be wrong on this but from my understanding, the alternator output from the motor does not charge a battery very well unless you run in for a extended period of time.<br /><br />I had a similiar problem with my starting battery going dead. I solved it with the larger deep cycle and have had no problems.<br /><br />A new dual purpose battery should not be to expensive either. You can also buy a small handheld battery guage to let you know when to charge the battery. I know minnkota makes one for around $10.<br /><br /><br />Hope this gives you some ideas.<br /><br />Jay

 

[LubeDude]

Re: When to charge cranking battery?

I think you need to concider going to a two battery setup where your cranking battery dosnt get used except to start the engine. Just starting your engine isnt going to charge you battery up like your car does, you probably only have around a 2-6 amp charging curcuit on that engine. If you stay like you are, what you describe is likly going to happen again.

 

[NeWcS]

Re: When to charge cranking battery?

This is so strange. This is why I always ask the same question on more than 1 board. On every other board ive posted everyone says its ok to hook all the assec. to the starting except this site? <br /><br />I guess it takes all types.<br /><br />Thanks<br /><br />-Jay

 

[Salmonseeker]

Re: When to charge cranking battery?

It is okay to hook up your accesories to the starting battery if you use them with the motor running. They will take power from the alternator and not drain the battery. If you run them with the motor off for any length of time they will drain your battery. It is like headlights on a car. They work great when the motor is running, but will kill your battery with the motor off.<br /><br />Jay

 

[NeWcS]

Re: When to charge cranking battery?

Ok, so with that said how often should I turn the big motor on to make up for the Sonar and GPS drain on the battery?<br /><br /><br />-Jay

 

[Salmonseeker]

Re: When to charge cranking battery?

Honestly, I really don't know maybe somebody else can help. I wouldn't think the Sonar and Gps would drain it that much. <br /><br />I have always been told that it takes along time to charge a battery from an outboard. They don't charge batteries very well. They just maintain them.<br /><br />Jay

 

[jtexas]

Re: When to charge cranking battery?

newcs, I run my accessories off my starting batt too, I think it's common - you're probably getting the separate battery advice because your safety was compromised when you ran yours down - for whatever reason your combination of accessories caused you a problem with this battery. I use a deepcycle for cranking, and with the trolling motor batts and jumper cables in the boat I don't anticipate running out of juice. <br /><br />Hard to believe that just a sonar & GPS would drain the battery in a day - maybe if you had stereo, livewell pumps & running lights on.<br /><br />Anyway, you can use your sonar's voltmeter to judge the condition of your battery. When your engine is running it probably shows somewhere in the neighborhood of 13 to 14 volts. A battery is considered fully charged at 12.6 volts, and 50% charged at around 12.4 volts. How much voltage you'll need depends on your engine & how quickly it starts. 12.3 might do it. If I were you I'd turn on the accessories and experiment to see what it takes. If your boat's on a trailer, remember that the engine is easier to crank without the backpressure of being in the water. As the battery ages, it's ability to supply cranking power deteriorates so eventually you could have a situation where the voltmeter shows full charge but it still won't crank. Somebody jump in if I got anything wrong here - I'm no expert.<br /><br />As far as your outboard not charging the battery quickly...I once ran my battery down during a compression test. Jumped started it & after 5 or 6 minutes idling it was strong enough to crank the engine. That's just my experience - '79 rude 70 with the stock 4 or 6 amp alternator.

 

[NeWcS]

Re: When to charge cranking battery?

Sorry I may have posted wrong. I dont think I drained the battery I think it was bad to start with. I just want to make sure its not going to happen again.<br /><br />Thanks for the input all.<br /><br />-Jay

 

[Silvertip]

Re: When to charge cranking battery?

Gee Whiz man. Unless you change something it is very likely to happen again. You apparently are not very concerned about your safety. As was pointed out, a starting battery is not intended for deep cycle operation regardless what anyone tells you. They simply are not built for that. Neither are deep cycle batteries intended for starting use. Dual Purpose Marine/Deep cycles can serve dual purpose but they are not the best at either task. Your 75 HP engine has an 18 amp alternator. You would need to run it wide open for at least an hour to put any significant charge back into a weak battery. Since this is a starting battery, getting much below 11 volts or less will leave you stranded. At least make sure the battery you do have is fully charged before you leave the dock and that it is viable battery (no bad cells). Buy a jump start pack to take with you should that battery leave you stranded.

 

[waterone1@aol.com]

Re: When to charge cranking battery?

I have a slightly different opinion. This is a 75 horse outboard.....not a big-block 454 inboard. I see no problem with starting an engine of this size from a deep cycle battery. If I only had one choice of battery for this rig it would be a deep cycle. With that said, the above advice about your alternator is correct....it's small, it needs several hours at high rpms to replace the energy you took from your battery while anchored with your accessories on. Besides a worn-out battery or failed component in your charging system, the most likely culprit of battery drain is your depth sounder or sonar. Some of these units use 200 watts....thats up to 20 amps of current draw. In an hour or two, many batteries will be to "flat" to start an engine. As others have said, your best bet would be to have two batteries on an isolator or at least a battery switch. As an example, run just your 180 watt sonar for an hour then start the engine, you will have to run at fast idle for 1 1/2 hours just to recharge what you "took" from the battery......assuming it was fully charged to start with.

 

[imported_Curmudgeon]

Re: When to charge cranking battery?

Some of these units use 200 watts....thats up to 20 amps of current draw.<br /><br />Not likely on a boat with a 75 motor. Most DFs are fused at 2 to 5 amps. The wattage one sees with DFs is usually the output (penetrating) power of the transducer, not power draw of the unit ...

 

[jtexas]

Re: When to charge cranking battery?

what kind of depth finder are you talking about? My Eagle320 current draw is measured in milliamps. I've left it on all night before without a problem. With the display light on. Still, starting the day with a good fully charged battery is the best advice anybody can give.

 

[Salmonseeker]

Re: When to charge cranking battery?

I have a Lowrance X-85. It says in the manual it has 3000 watts (p-p typical) and 375 watts (RMS typical). I had this unit on my old boat with one medium size deep cycle battery. I also powered an electric downrigger and navigation lights at night. The motor had no alternator. I could go a whole season and would only use about a 1/3 of the batteries charge.<br /><br />My point is that Fishfinder units do not take that much power even though they have such a high watt output as mine does.<br /><br />I use a deep cycle to start my 50HP and have had no problems. It actually has more cranking amps than the starting battery that came with the boat.

 

[Silvertip]

Re: When to charge cranking battery?

That 3000 watts is not the power required to operate the unit. Thats output power and its an AC signal, not DC power consumption. Big difference. If your locator drew 2000 or 3000 watts that's over 160 amps. Don't you think the little bitty power wire would get warm at that current and maybe pop a 5A fuse? And the battery would be dead in minutes.

 

[Salmonseeker]

Re: When to charge cranking battery?

Thats the point I was trying to make. Sorry I didn't make it clear. I know it does not really use that much power. Like I said I never had to charge my battery all season.

 

[kenimpzoom]

Re: When to charge cranking battery?

I think you had a bad battery and the new one should solve your problems.<br /><br />But, if you fish in those type of conditions, I would suggest you carry a spare battery. Rig up cables or a switch so you can easily change over to the good battery.<br /><br />Ken

 

[NeWcS]

Re: When to charge cranking battery?

Originally posted by KenImpZoom:<br /> I think you had a bad battery and the new one should solve your problems.<br /><br />But, if you fish in those type of conditions, I would suggest you carry a spare battery. Rig up cables or a switch so you can easily change over to the good battery.<br /><br />Ken

I think your right, or atleast a completely dead one.<br /><br />As far as 'those type of conditions' its rare for us to get wind like that here in Denver. Its was just bad timing on my part.<br /><br />As for my fish finder: I run a Humminbird Matrix 27 and a Lowrance LMS-160 Map. <br /><br />I just went and got a 1000/825 cranking battery, I hope I can say it works everytime and I only charge it in the off season <br /><br />-Jay

 

[phantoms]

Re: When to charge cranking battery?

Make sure to go over your battery connections and connections at the motor and fuse panel. A bad or corroded connction will act just like a dead battery, and it will show worse when then battery is not fully charged. If you don't find any problems there, you might want to check your charging system. As stated in a post above, your system voltage will climb above 13V when it is charging. If not, you have a charging problem. If that checks out too, then take the battery out and have it checked. Most autoparts stores can do this for you for free.<br /><br />I have a Interstate 850CCA battery (automotive type) that runs everything on my boat. This is not much, a FF, running lights, VHF, etc. I have fished all day without cranking with the VHF and FF running and had no problems cranking. If you are running a lot of high draw electronics, such as a livewell, stereo, spot lights, etc., then you would be better off with a dual battery setup. Keep the alarm on your FF set to 12.2 Volts and if the battery ever gets that low, start up and let it charge.

 

[studlymandingo]

Re: When to charge cranking battery?

I really prefer being on the water with 2 batteries, nice to know that if one is not strong enough to crank, I can switch to the other, or both. I go 25 miles offshore occasionally, and wouldn't want to be out there with a paddle and a heavy boat!