Deep Cycle Q?

[Gone]

During my haste with an impending storm, I accidentally bumped the off/on switch of my Minn Kota foot control when covering the boat. The power level was at zero so the prop never turned.
It sat for 5 days that way and drained the battery.
How much damage did I do to the battery? With the on-board charger, I charged it for 5 hours and it only came back to 12.4V, about half charge for a lead/acid battery. I'll check it again this weekend and charge it some more. Did I ruin the battery already??

CD

 

[JB]

Re: Deep Cycle Q?

That is why you use a deep cycle battery, VCD. They can tolerate complete (deep) discharge.

You will probably need at least 24 hours on an automatic charger to bring it back.

Do not trust a voltmeter to tell you the state of charge of any battery. A load tester like the one that may be in your troller is a lot better because it measures voltage under load.

The best, most accurate way to determine state of charge is with a hydrometer, which measures the specific gravity of the electrolyte. You need one.

Good luck.

 

[Gone]

Re: Deep Cycle Q?

Actually I have one, JB. It was at home about 140 miles away but I had my FLUKE with me at the time. I remembered the 12.4V bit from my BCI battery service manual open circuit voltage test. Mainly I wanted to see if I shorted a cell.
I'll charge it more tomorrow. Thanks for the encouragement!

CD

 

[Texasmark]

Re: Deep Cycle Q?

You're probably alright. Like was said it's a deep cycle. Also the discharge was very slowly. Don't develop much heat like that which could boil your water out of your electrolyte and evaporate.

Agree on JB's hydrometer and load testing, but both are usually not available. But your multimeter is. I use 12.75 for full after at least 24 hours after charging to allow the chemicals to bond correctly and settle out.

My onboard charger has 2 ea, 5 amp 12v circuits to charge 2 different batteries simultaneously, like in a 24 volt series system. It has a red light that comes on when on full charge and after the batteries have reached about half charge the red and green are on and at full charge just the green.

Amp hours is just that If you take out 10 amps for 1 hr you removed 10 amphours. Gotta put it back if you want the battery recharged.

So say your bleed current was 1 amp and bled for 5 days. That's about 120 amphours so it will take 10 hrs at 12 amps or like with mine 24 hrs at the full 5 amps to fill it back up.

But since chargers usually back off the current as the voltage/charge on the battery rise, it will take 2 or 3 times that to reach full charge.

HTH,

Mark

 

[Gone]

Re: Deep Cycle Q?

I'm usually very good at analyzing others problems but my brain turns to mush when faced with similar problems myself! I tend to throw too much into the mix.
Thanks for helping me make sense of it all!

BTW, the battery is fine!

CD

 

[b00tstrap]

Re: Deep Cycle Q?

Another option would be to have the battery tested (usually free) at a local auto-parts franchise.

 

[ZmOz]

Re: Deep Cycle Q?

Just because it's a deep cycle doesn't mean it wasn't damaged. Without a doubt, the capacity has been reduced. It will still probably power your trolling motor fine, but not for as long. The worst part is not discharging it all the way, but leaving it that way for 5 days. Lots of sulfation has developed in that time, and that's what eventually kills most batteries.

Your battery would benefit from a desulphating charger like a "battery minder", although they cost as much as a new battery...

 

[jtexas]

Re: Deep Cycle Q?

doing that over and over again would kill it for sure...at worst, you may have shortened it's useful life...

in case anybody's interested, here's an interesting discussion of battery desulfatation...
"http://www.shaka.com/~kalepa/desulf.htm"

 

[Texasmark]

Re: Deep Cycle Q?

Last time I looked at a deep cycle life chart it measured number of complete cycles and life was based upon that. Didn't mention how long it was discharged. Additionally, it showed lots of deep cycles before the capacity curve started to decline.

Besides, you probably never use it to capacity anyway so what the heck. :%

Mark

 

[Gone]

Re: Deep Cycle Q?

True! I never run it below 30%. It seems to charge fine and motor run time is about the same.
I think that I lucked out!

CD

 

[ZmOz]

Re: Deep Cycle Q?

Last time I looked at a deep cycle life chart it measured number of complete cycles and life was based upon that.

Battery manufacturers consider a battery to be "dead" or a "complete cycle" long before the power hits ZERO. Running any kind of rechargeable battery this low is really, really bad for it. Most manufacturers consider the battery to be dead at around 10.5v, and even this is much too deep for every day use.

Also, the number of cycles a battery is good for varies by huge amounts between manufacturers and battery models. I have some very expensive Hawker AGM batteries that are rated for 400 cycles at 100% discharge, but if you tried that with your average Wal Mart battery it would only last a hand full of cycles.

 

[Texasmark]

Re: Deep Cycle Q?

Okaye folks, a little off topic, but an interesting tidbit none-the-less.

I bought a well used 400 cubic inch Diesel, John Deere Farm tractor that had a (1) well used 12v deep cycle trolling motor (not combination) battery for starting. It started very well summer or winter. And being in the used condition that it was it apparently had been doing it for awhile.

I didn't know that deep cycles could do that.....thought they were only supposed to deliver low currents with their few in number, thick plates. :%

Mark

 

[ZmOz]

Re: Deep Cycle Q?

I didn't know that deep cycles could do that.....thought they were only supposed to deliver low currents with their few in number, thick plates. :%

Deep cycles do put out less amps than a normal starting battery, but they still can put out hundreds of amps. Most starters use less than 200 amps, which is only "2C" for a normal sized deep cycle. (2 times the battery's capacity) A cranking battery can put out 800+ amps, or around 8C, but unless you're trying to start a dump truck in antarctica you'll never need that much. My Jeep's starter only uses about 125 amps for it's big old inline 6.

 

[Texasmark]

Re: Deep Cycle Q?

Sir, I assure you my diesel with 400cu in and over 500psi cranking compression (16:1 compression ratio) will use all 200 amperes and then some. (My 90 hp outboard is rated at 120 amperes in my Merc service manual and it's nowhere near the load to roll the diesel is...especially in winter when diesels don't like to start and the oil in the crankcase is thick as molasses.)

Normally tractors of this size use 2 ea HD size 27 or 31 batteries of 800 or so CCA and preferably have them wired in a 24 volt configuration to reduce the required current.

The info I supplied came from battery mfgr's brochures. They indicated that to keep the plates from cracking and failing (under deep cycling) they had to make them thick on deep cycles. Went on to say that since the battery was only so big you could only get so many in there; hence the surface area exposed to the acid solution was reduced and the max current accordingly. That's why later on, they came out with the combination crank/deep cycle.....don't know how it's built. :%

HTH

Mark

 

[Gone]

Re: Deep Cycle Q?

During one of my visits to the International Truck Engineering group The engr was showing me some wiring harnesses that he was working on. I asked about the current that the diesel starter drew and he floored me with 900 AMPS! I would assume that it is also @24volts.
Just my $.02.

CD

 

[jtexas]

Re: Deep Cycle Q?

Last time I looked at a deep cycle life chart it measured number of complete cycles and life was based upon that. Didn't mention how long it was discharged. Additionally, it showed lots of deep cycles before the capacity curve started to decline.

Besides, you probably never use it to capacity anyway so what the heck. :%

Mark

A 12V wet-cell battery reaches a 0% state of charge at 11.89v (at 80ºF), and is fully discharged at 10.5v - discharges below 10.5v can damage a battery.

Any time a battery is at less than 100% state of charge, soft lead sulfate crystals start to form on the plates. Charging converts the crystals back to lead. Left uncharged, the crystals harden to the point where normal charging can't change 'em back.

 

[ZmOz]

Re: Deep Cycle Q?

Sir, I assure you my diesel with 400cu in and over 500psi cranking compression (16:1 compression ratio) will use all 200 amperes and then some.

Not really. 200 amps is about the limit for what your starter could possibly use, unless there is something horribly wrong with it.

Take a look at this:
http://cgi.ebay.com/NEW-CASE-CUMMIN...TER-16990_W0QQitemZ130016015800QQcmdZViewItem
A brand new starter for a 5.9L cummins. It is rated at 2.5kw @ 12 volts. That's only 208 amps.