Very strange battery behavior

[jtexas]

This is about a marine deepcycle battery powering a 36# motorguide. The battery is about 10 months old, the T/M is a few years older (don't know exactly).<br /><br />I'm running out of power too early in the day, sooner than I used to. My habits haven't changed - I use it a lot on the highest setting.<br /><br />Here's the strange part: last two times out, when it started getting noticeably weaker I measured the battery voltage at 11.8 & 11.9 volts. When I got home couple hours later, it was at 12.5 & 12.7 volts. First time I thought I was just crazy or sloppy with measurement or something. Hydrometer shows all cells near the top of the scale.<br /><br />I've been very particular about always charging it at soon as I got home using 6-amps, and it hasn't needed water. After charging it typically shows a little over 13v. When I left the house Saturday it read 13.1.<br /><br />I recently replaced the plug, wiring and recepticle, using 10 ga. wiring. Tests show minimal resistance.<br /><br />Any idea what's up with this? I can get a free replacement batt, but I'm wondering if this is symptomatic of a T/M problem.<br /><br />thanks,<br />jtw

 

[Ralph 123]

Re: Very strange battery behavior

I'm not shocked JT. When the battery is being used (under heavy load) There are chemical processes going on, heat, etc. and the voltage drops. So, after the battery has had chance to cool and recover back at home, the voltage comes back up. The older the battery gets, and the more charge/discharge cycles it goes through, the greater the drop and longer the recovery time.<br /><br />You can really see this affect in a flash camera - the more you use the flash, the longer it takes for the battery to recover to use the flash for the next picture.<br /><br />I usually like to point people to some external source, so here is one that describes somebody testing this:<br /><br /> http://www.hobbytalk.com/modules.php?op=modload&name=Sections&file=index&req=printpage&artid=49

 

[cuzner]

Re: Very strange battery behavior

Are you using wal-mart batteries? don't know the science behind it... but my freind (who bought wal-mart ones, against my advice) had the same issue, low power in hurry on the lake, showing almost full charge in the driveway after. Haven't tried the replacements yet this year.<br /><br /> Jim

 

[jtexas]

Re: Very strange battery behavior

Yep, Jim, I've been using the Walmart Everstart trolling deepcycle, never had a complaint until now. Well, I had one before that would self-discharge too rapidly but I attributed that to user error - I overcharged it to the boiling point a couple times, didn't add water when it was needed, that sort of thing.<br /><br />Ralph, I was aware of the "recovery" process but had not seen it so dramatically before. I bet this batt hasn't seen more than 20 discharge cycles, & I been treating it very kindly.<br /><br />I'm going to take it back for a new one, then decide whether to add another to the circuit.<br /><br />Anybody else seen this in any other battery?

 

[briannh1234]

Re: Very strange battery behavior

Might want to try a smart charger. Unless the charger has the smart's you run the risk of overcharging the battery. Also, the only thing that changed was your wiring? - You may want to double and tripple check it. Check to see if anything is getting hot while using your t/m. A lose connection will use more watts.

 

[jtexas]

Re: Very strange battery behavior

yeah, brian, I would like to have a smartcharger, meanwhile I have to risk it. Although the way it is now, it's fully charged when I get home, I may never need to charge it again. <br /><br />I went over the wiring carefully, checked it with an ohmmeter. Checked the motor as well as I could in the garage. Cleaned & inspected the wires & connections under the foot pedal, etc.<br /><br />I'm just amazed that it can be dead (nearly) in the water at 11am, and recovered to a full charge by 6pm. The motor's old, maybe it draws more amps than it did before, and maybe it's inadequate for the job anyway, but could that be what's causing my battery symptoms?<br /><br />If I replace this one & get a matching one to run parallel, theoretically I should double my running time per outing, right?

 

[18rabbit]

Re: Very strange battery behavior

Originally posted by jtexas:<br /> ... I measured the battery voltage at 11.8 & 11.9 volts. When I got home couple hours later, it was at 12.5 & 12.7 volts.

After a battery is depleted, over time a charge will ‘float’. It is deceptive because the battery can’t sustain that voltage for any real length of time. You often see it when a battery is run down trying to start an engine. It gets to the point there isn’t enough juice left to turn the engine over. Wait 10-min, the voltage will increase, try again, and the engine turns over.

 

[LubeDude]

Re: Very strange battery behavior

You never said what group size the battery is. If its just a 24, then you dont have enough battery. You either need to use two 24s hooked together, or at least a group 27. You can do some serious drainage quickly on just one 24. I now have two group 24 Trojans hooked together, and I can fish 12 straight hours and still have plenty of power left. My battery meter in the boat has 4 bars, it takes about half a day for it to show down to the third bar, then it stays there the rest of the day.

 

[LubeDude]

Re: Very strange battery behavior

Bump

 

[LubeDude]

Re: Very strange battery behavior

Bump again

 

[jtexas]

Re: Very strange battery behavior

I started to reply yesterday when the boss walked in - how fast can you alt-tab?<br /><br />It's a 24. Guess I'm just overworking it - I'll trade this one in on a free replacement & add another.<br /><br />thanks,

 

[ebsworj]

Re: Very strange battery behavior

moved to its own thread

 

[pilot4net]

Re: Very strange battery behavior

I agree that the battery may be not quite enough for the work your doing with it. One thing you can try is to recondition the battery if you know someone that has a charger capable of doing this. Also, I always try charging my batteries at the slowest rate possible (4 amps on my charger) since through experience with battery banks, I have found that a long thorough charge seems to hold better than a higher amperage or quicker charge. I will admit that the experience I have had hasn't been with marine batteries, but they have been deep cycle batteries none the less. The reconditioning I refered to earlier is disputed by some, but I have seen it take a battery that wouldn't hold a charge for nothing, desulfate or recondition the battery for 18 hours or so, and then recharge the battery and it worked 10x better. I agree that two batteries will undoubtedly give you more amp hours therefore giving you longer run time. These are just my two cents. Later.

 

[Tatorbug]

Re: Very strange battery behavior

Even new batteries can be defective. It sounds like yours may be down on one of the cells under load which will cause the batery voltage to fall and discharge faster, terminal voltage will recover, however, the battery has little capacity. Check your battery with a load tester or go to walmart and they will test it for you and replace it if under warranty.