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I have a 74 pounds of thrust 24 volt Minn Kota trolling motor. I purchased two of the best rated batteries that I could find locally (Trojan, deep cycle, 130 amp, 7.1 hours run time at 15 amp and 820 marine cranking amps). On my first trip (which was early in 2005) after fully charging the batteries I tried using it for trolling just to see how long it would last. I was able to troll almost steady with it (varying the speed from slow to fast) for about 5 hours before the batteries run down. Last Saturday, after fully charging the batteries (onboard with my Dual Pro charging system), after a maximum of 30 minutes of slowly moving around looking for fish to vertically jig to, the batteries were too low to operate the trolling motor. I removed the batteries and charged them (using my automatic charger set to deep cycle setting) and after letting them sit overnignt took them to Batteries Plus to have them checked out. The guy at Batteries Plus said the one battery had lower cranking amps than he would like to see, but that it was a deep cycle battery so no problem and everything else checked out fine. Is it possible that I have internal resistance in one or more of the batteries that is causing the problem (if so how do I check for that) or could something else be causing the problem? I should also explain that I purchased my first Dual Pro charging system used off of eBay and when I started having similar problems to the above and Batteries Plus said the batteries weren't charged I purchased a new Dual Pro charger in 2005. I should also note that with my single battery charger at times the charging meter will slowly move down until the green light turns on, indicating it is fully charged, and other times the arrow stays up high. I have decided that the charger is actually working because the batteries are charged and the water doesn't boil out of the battery (but my logic could be faulty). Can a deep cycle battery develope memory? If one is supposed to drain the batteries every time before recharging how does one accomplish that? Any help would be appreciated.
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[black][size 3]I think that if you do an in depth study, you will find that lead/acid batteries do not have memory. Only neglect and age kills them. I have personal knowledge of vehicle batteries that have lasted over 5 years.[/size][/black]
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[size 3]Many of the rechargeable batteries (closed cell) that were developed for phones, laptops, flashlights, etc. had a bad memory problem. I don't know if the latest technology has corrected this problem. The advancements made in batteries, has certainly improved the charged life of batteries.[/size]
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[size 3]I have a cell phone that is over two years old, and is on 24/7. On standby, it would last over a week when new, now it's charge life is about 4 or 5 days.[/size]
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Wet cell lead acid batteries do not have the "memory" effect. This was a characteristic of NiCad batteries years ago. You do not need to fully discharge your batteries before you charge them. The one thing you do want to do is charge them as soon as you can after you use them. Do not let them sit in a discharged state for days or you will kill them quickly. Your motor can draw almost 45 amps at high speed so its not going to run all day long at that rate. You stated your batteries were good for 7.1 hours at 15 amps so 5 hours at varying speeds is about right. On that Saturday when you only got 30 minutes, it sounds like your batteries were not fully charged. Your batteries are two years old now. If they sat around in a discharged state, that could be your problem as that can cause them to develop internal resistance. If you are sure you are getting them fully charged and they tested that way under load, then you should get around 5 hours use like you did before.
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I charge my batteries immediately after I get home. How can one test for internal resistance?
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Ohms law is voltage = current X resistance. You need a battery load tester that will measure the voltage and the current. The current will be the same through the load and the battery. The voltage across the load or the battery can be measured with a volt meter. The total resistance will be the sum of the load resistance and the resistance of the battery.
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Sorry, I have no idea what this all means. All I know is that I took the batteries back to where I purchased them and he said that they checked out fine. He did say he would be happier if the starting power was better on one of the batteries, but that it was a deep cycle battery, and not meant to be used for starting, so he wasn't too concerned.
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Sent you a PM.
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i use a general formula for finding out how long i can run my stuff....
get the amp hour output on the battery. figure out how much your equipment draws....then divide...example a 400 amp hour battery will run my 50 amp draw motor for 8 hours...400 divided by 50 is 8. this is general times.
you post says your battery is rated at 7.1 hours at 15 amps...thats in the neigborhood of 106 amp hour rating. so multiply here to figure out the battery specs...7.1 times 15 = 106.5 amp hours approx. then if you draw at 45 amps divide... 106 divided by 45 = 2.3 and some change, so you are getting less than 3 hours of run time off a single charge. the cold crank amps dont matter because you are not starting a engine you use the deep cycle part of it all to maintain a flow of energy to the electric motor...you need bigger batteries...i am not exactly sure how that changes when you run in series to get the 24 volts, but i know it does not double that intital number even if it did you would only be set up to get around 5 hours at best on a charge...which you did when they were spankin new, figure that time will decrease with age and use on those batteries...you should ask about the amp hour rating...the higher the number the longer you fish. i use a 100 amp hour battery because my 12 volt motor has a 7 amp draw on high speed and around 5 amps on low, i do not have variable speed i have hi lo off.
i will find the report on the amp hour stuff i was reading in a journal and post the highlights here for all to see...it was interesting.
good luck!! if you need other questions shoot me a PM. i know a couple things about electron flows and protrons and other nuclei.
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Thanks, all I know is that I purchased the highest amp batteries I could find locally, they are extremely heavy, been used very little, and don't seem to hold a charge!
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[font "Tempus Sans ITC"][#808000][size 3]Since you took the batteries in they were probably checked, so this is probably a dumb question but are the batteries full of water? You can check by taking the cap off the top and the water should be all the way to the top on each cell. If any of the cells are dry fill them up with distilled water. If a battery starts to go dry in any of the cells it will not hold a charge as long. Marine batteries are really bad for going dry because of the way we use them. They don't have a memory but by deleting all of the charge and then charging over and over will cause the water to dry out faster.[/size][/#808000][/font]
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[font "Tempus Sans ITC"][#808000][size 3]I hope this helps and sorry I didn't see this earlier.[/size][/#808000][/font]
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Yes, they are full of distilled water.
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[font "Goudy Old Style"][size 3]You may want to check your trolling motor. I just bought a new Minn Kota with a higher thrust that my old one and I can run it even longer. The new ones operate a lot better than the old ones.[/size][/font]
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[font "Goudy Old Style"][#000080][size 3]FYI-Do you your research on them. Motorguide components are 5times as much as a Minn Kota. I've had both and would never go back to Motor Guide[/size][/#000080][/font]
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one thing i have seen in "wet cell" batteries is over time if they discharge to almost zero...low enough you think they are dead but are not quite dead....like to 1 volt or something...and get recharged, they sometimes have a hard time "accepting" a full charge off a normal charger. this is when i put a "trickle" charger on them, one that will put out like 2 amps and 12 volts instead of a 20 amp 12 volt charge to the battery. really any charger that can charge less than 5 amps and 12 volts will be a trickler in my mind. its not a "memory" thing with this it just happens, i dont know why, how or what causes it but it happens. try to run a 2 amp trickle charge on them for say.....24 hours to get them up enough to accept a full charge off the normal charger.
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It is a newer trolling motor, but who knows it may be faulty (not sure how to test it).
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I'll try that.
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