Battery Life Questions

Old 06-17-07, 05:50 AM
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Battery Life Questions

I have a 2003 Jeep GC Laredo which has the OEM battery. I also have a boat with two deep-cycle Die Hards, date codes March 99 and June 2000. The boat has a single engine and I have a switch that allows me to use either or both batts. This switch is in the Off position when I'm not using the boat.

The Jeep's battery is beginning to fail to hold a full charge but the two marine batts are still going strong. Prior to 1999/2000, the previous boat batts lasted ten years.

Aside from the manufactured difference ("starting" versus "deep cycle"), the only thing I've done differently is store the boat batts in my attached garage for the winter with no trickle charge. The Jeep sits outside in the driveway, and winters get cold up here in Buffalo.

-- Can I use a deep cycle for the Jeep? Stuff I've read says the only difference is the plate height is higher in a deep cycle so it takes longer for the gunk to build up on the bottom and short them.
-- I've also read that the "cold cranking amps" spec is mostly marketing hype and that deep cycles can be used for starting. True?
-- Are there advantages to trickle charging over the winter?
-- When charging the boat batts, I've been switching to A or B. Is there a downside to leaving the switch set to both?

Many thanks.
-- RJ
Old 06-17-07, 03:27 PM
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I am no expert on batteries, off hand I'd say no is not advisable to switch one for the other, althought I dont have the technical info to back that up but anyways why not get the Jeep a new battery and be done with it ?
Automotive batteries are cheap.
Old 06-17-07, 03:29 PM
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There are things on the Jeep that are always on, like clock, radio presets, etc. There is never a no load condition with the Jeep.
Old 06-18-07, 08:46 AM
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I did a little research, and it appears that car batteries are designed to provide for a large current surge (for starting) and some reserve capacity. Deep cycle batteries have a much smaller surge potential and a large reserve capacity. The surge power (cold cranking amps) plays a big role in colder climate. The reserve capacity refers to the time a battery can drain at a given rate before the voltage falls below a certain level.
Old 06-18-07, 09:10 AM
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A deep cycle battery can be discharged and recharged quite a few times.
They are made to have a fairly steady draw (even if it's a high draw, such as for a winch) over a period of time.

On a standard automotive battery, a few full discharges and it will done, it's designed to provide a high amount of power for a very short period of time.

Trying to swap them will lead to premature failure.

When boating and you have more than one battery, it is not advisable to use the 'both' setting, UNLESS you have a dedicated starting battery that is not part of the deep cycle system. If you do not, and you use the 'both' setting, you may find yourself stranded because the batteries have been drained to the point that they cannot start the engine. Using one battery ensures you will have another to start the engine with.

If your Jeep still has the original battery from 2003, you've gotten decent service from it given the climate it's been in.
Old 06-18-07, 10:45 AM
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while you could put a deep cycle in your jeep and it would function ok you probably would still have similiar battery life.
cca is important your jeep starter can pull alot of amps especially on a cold engine 300 amps from the starter isnt uncommon the more cca your battery has the longer you will be able to crank the engine over in cold temps before the battery goes dead this rating is taken at 0 degrees, cranking amps is similiar and should be considerbly higher as its done at 32 degrees.
trickle charging is the preffered method of charging a battery while its slow and may take 48 hours to fully charge a low battery it causes the least amount of damage to the battery, and may be of benefit to you in the winter if they did need charging but a fully charged clean battery should be able to set for months without losing much of its charge.
Old 06-20-07, 03:44 AM
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Thank you -- much appreciated.

-- RJ
Old 06-20-07, 07:18 AM
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All good advice above which addresses your questions I believe.
Just a couple things I would like to add.
A batteries life is greatly affected by temperature. Can be a couple of years of normal service or 10 plus depending on the temperature. The hotter the temperature, the faster the battery goes like a belly up fish.
The Jeeps engine compartment is hotter then the boat.
Also the Jeep would see more use. More starts equal more deterioration and that means shorter battery life.

On the issue of the deep cycle in a car. The charging system is based on the battery which expected to go into the vehicle (internal resistance). The deep cycle would not be completely compatible (different animal) and would never be charged at the exact rating and it would fail early.
That is also why there are different setting for sealed batteries and non sealed batteries. Different voltage settings.
Best to put recommended batteries in the equipment.

A lawnmower battery can start a car if needed but when it comes down to the crunch,,,,, it won't,,, and the battery will likely get damaged.
I would use the largest cold cranking amps I could fit in the car.
For $10 extra for a couple hundred cranking amps would be worth it because not only does it provide extra emergency power but a battery goes down in the years (100% 70% 40% etc) and even a 40%n battery of a lets say 800 cranking amps will start the car where 40% of a little 375 cold cranking amp battery could leave you stuck somewhere. And often it costs money to get a boost.
Good luck

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