Battery Question

No Hook Em

Recruit
Joined
Oct 9, 2003
Messages
4
I have 2 batteries with a switch for my outboard. I have my gps, vhf, fishfinder & radio hooked to the engine batteries.<br />I'm considering installing a seperate battery to operate my gps, vhf, fishfinder and radio.<br />My question is this. Should I install a regular battery or a deep cycle battery?
 

Mucka29

Petty Officer 3rd Class
Joined
Aug 31, 2003
Messages
87
Re: Battery Question

hey,<br /> I would put a deep cycle so u can run it dead
 

kd6nem

Chief Petty Officer
Joined
Jul 25, 2003
Messages
576
Re: Battery Question

Combo batteries are OK, though personally my preference is to go straight deep cycle, just make sure it has enough rated capacity to crank the motor if you might ever ned it to do so. These tend to last longer (when kept charged and watered) than any other, and are more forgiving of getting low. I would never recommend a starting only battery. <br /><br />My 2 cents worth...
 

captain537

Cadet
Joined
Apr 18, 2003
Messages
18
Re: Battery Question

Hello<br />batteries is not a place to try to save a buck. You have the right idea, I separated my cd player, GPS, VHF and ran 2 new wires from the battery to a terminal strip and then new wires from each device. I run on that battery most of the time so when you have them on with the battery off, it then charges it back up when you run to the next spot. Then occaisionally I run on the other battery to keep it fresh for an emergency.<br />Bruce
 

Knightgang

Lieutenant
Joined
Oct 6, 2003
Messages
1,428
Re: Battery Question

Deep cycle. They are designed for the abouse of marine life. Charge it up, run it to nothing, charge again, bang around in boat, etc.
 

Paul Moir

Admiral
Joined
Nov 5, 2002
Messages
6,847
Re: Battery Question

Contrary to popular opinion, discharging any lead acid battery, particulairly beyond 50% charge (not voltage), will damage it. Deep cycle batteries just put up with it better than automotive starting ones. If you want it to live for a long time, keep it charged and cool.<br /><br />EDIT: Oops - 50% is for AGM deep cycle batteries. For regular deep cycle, never more than 80%, and try to discharge it past 10%. About 20% is optimal for life.
 

kd6nem

Chief Petty Officer
Joined
Jul 25, 2003
Messages
576
Re: Battery Question

Paul,<br />Thanks for pointing that out. I knew that to be true but didn't remember the numbers. I'm a little fuzzy on how you meant the numbers, though. Would you restate that, please?
 

Paul Moir

Admiral
Joined
Nov 5, 2002
Messages
6,847
Re: Battery Question

Sorry, I was trying to be brief, but I just came out confusing. I'll try to be more clear.<br /><br />The more you discharge a lead acid battery, no matter what type, the more damage you will do to it. The damage will cause the battery to only live through a fraction of it's possible discharge/recharge cycles.<br /><br />For example, a battery regularly discharged 20% down from fully charged may have ten times the potential life of a battery discharged 80% of it's capacity.<br /><br />If you discharge a battery past 80%, it will damage it very badly, and may quickly kill it. The plates inside the battery accumalate lead sulfate very quickly at this depth of discharge. This buildup gets too heavy to be removed by recharging often within a couple of days.<br /><br />Shallow discharges under 10% can actually hurt a deep cycle battery. They need a bit of exercise.<br /><br />Percent of discharge is related to battery voltage, but it is also dependant on tempurature and load. Here's a chart for room tempurature and just after a load is taken off:<br />100% charge - 12.7 Volts<br />75% charge - 12.4 Volts<br />50% charge - 12.2 Volts<br />25% charge - 12.0 Volts<br />Just about empty - 11.9 Volts<br />The best way of determining percent of charge is to measure the electrolyte's specific gravity. Unfortunately, that's really inconvinent.<br /><br />Hope this helps!
 

AUGIDAWG

Petty Officer 2nd Class
Joined
Oct 31, 2002
Messages
189
Re: Battery Question

Paul, you are confusing the poop out of me with your terminology.<br />When you say "a battery regularly discharged only 20% of it's capacity", what do you mean?<br /><br />20% down from fully charged, or 80% down from fully charged?<br /><br />Look at your chart and stick to that verbage.
 

Paul Moir

Admiral
Joined
Nov 5, 2002
Messages
6,847
Re: Battery Question

Sorry AugiDawg, I ment 20% down from fully charged, in other words about 12.4 volts. I stuck in that 'only' to prevent confusion, and I think it just made for more. Your wording is far more clear. <br />All those percents are from fully charged (100%) to discharged (0% charge).<br /><br />Time to edit that post...
 
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