Anyone use an onboard DC alternator charger?

[Rockin Rod]

Looking at a Stealth or the Minnkota DC alternator charger for my trolling motor batteries for when I go on long excursions up to LOW with no power. Does anyone have any experience with either?

[Surface Tension]

CM thanks for the update.

Del, in CM's, post his cranking battery is charged to full 1st then the trolling motor battery gets charged. IMO that is a better option then having a short charge to the trolling motor battery every time the outboard is started and never charged fully. Reason being that this adds a charging cycle to the battery whenever the outboard is started.

A full charge soon after use is best but in some cases where your on an extended trip that isn't an option. So how much is a batteries life shortened with the extra charging cycles?

My deep cycles last years. When I see threads where someone has a problem with a short lived

batteries, I'd bet its from one or more of the other reasons.

Not fully charging soon after use.(slow killer)

Not keeping the fluid up. (battery killer)

Heat, a black battery sitting in the sun with a charger on it is heat.(instant killer)

Frozen battery in winter. (shot battery)

Getting banged around whether when trailing or on the water. Not much you can do there but

if you keep up on the first 4 your battery stands a better chance at life.

I just bought two new batteries a year ago.

The ones I had where ridiculously old but still held a charge like a new battery.

My brother needed a battery and so I gave him a Stowaway. It lasted him 2 weeks.

Gave him the Interstate gel cell. Yep it was toast soon after.

I either got rid of the batteries at the perfect time or he ruined them.

Since he'll go through 10 batteries to my 1, I think I know what happened.

[CaptainMusky]

Yeah Surface Tension I will be sure to post results and hopefully Rockin Rod will share his experience with the Minn Kota too, which I am sure will work great as well.

The thing I am really jazzed about (well aside from the charging my trolling on the water) is the fact that I no longer need a separate charger to charge my cranking battery. I can plug one cord in and all systems will be charged.

Before I had my AC charger connected to trolling batteries, then I had to hook a trickle charger up to the cranking battery separately.

I like to blast the tunes in the boat while it sits in the garage. :-) So I find myself charging it regularly.

[CaptainMusky]

As promised I am going to provide an update from my trip last week.

Spent Tuesday through Sunday (left in AM yesterday) on Lake of the Woods out from Sioux Narrows.

We fished on average 10 hours per day. Start by 8 AM daily, fish to around 1 PM for lunch then back out from 2:30 to 8:00 PM.

All fishing was done using the trolling motor. No big motor trolling. We sometimes slip drifted using the trolling motor, but mostly trolled between .4MPH and .8 MPH.

I never ONCE plugged in my charger to the generator we brought to charge it. Thats right, not ONCE!

At the end of each day the worst my batteries read as far as level of charge was 75%, while the first couple days it was 100%. When we arrived at the landing yesterday to load up it was again at 100%.

I arrived home yesterday late afternoon and plugged in my charger and its just a green light as in its fully charged.

I am SIMPLY AMAZED! I never expected the Stealth1 DC Charger to work this well. Honestly I was hoping it would buy me a couple days before I had to charge or at least longer days on the water with fuller charge, but it simply is amazing.

A little bit about the fishing spots. One spot is about 3 miles from camp (just a guess) and the other spots are probably the same distance away from that so there is a fair amount of running with the big motor to allow the Stealth to do its thing.

The results I achieved would NOT have been the same had it been a small lake, etc. That I am sure of so if you fish small water primarily you wouldnt see the full benefits of this.

The other boat charged his batteries 3 times with the generator. He asked me to give him the info about this unit and he is going to buy one before next year, he was that impressed.

All in all, VERY pleased with the results. Thought I would share for others who may have similar needs.

[pheasantpete]

From a trained avionics tech with electronic engineering schooling. Caman the BullDog Comment you "Quoted" is incorrect. The life cycle (some marketing hype involved with the numbers quoted by manufacturers) of a Marine Deep Cycle is based on manufacturers set discharge of between 25% to 50% (50% is the maximum recommended for most marine deep cycles which are not true deep cycles which are capable of 75% discharge but do not like high current draws of electric trolling motors) and immediate recharging at an ideal rate. If you take it down 10% and recharge right away you will get many more cycles than a 50% discharge. The problem with you quoting is you have no clue what you quoting and whether it is valid or not. Years of experience is not replaced by someone who does a google search to find the info they are looking for and becomes an subject matter expert. A very old quote to consider, "Do not believe everything you read on the internet" Abe Lincoln.

However you are correct that fast charging is hard on lead acid batteries. AGMs are still lead acid. The ideal charging rate depends on battery capacity, and plate design. I hate reading a bunch of nonsense from people who ought to know that they do not have a clue but only seek to up their edit count. Both you and Capitan Muskie sure know how to blow smoke and talk out your other orfice. Muskie if you have shot batteries in 3 years as you stated then you might want to figure out what you are doing wrong before giving any more battery advice. Deep Cycles are extremely rugged and will last for at least 2X that if taken care of. I do however appreciate you response about your recent experience just be careful about presenting anecdotal evidence as a hard fact.

[pheasantpete]

Surface tension most of what you said is correct except about partial charging. Full charging immediately after discharging is ideal but a partial charge at a reasonable rate is much better for battery life than the alternative of a deeper discharge. Sometimes we have to get fishing again before the ideal charging and hooking them up for a couple of hours is better than no charge. There is no memory in lead acid batteries. Many people mix in different battery chemistries but different battery chemistries require different procedures and we are talking lead acid Marine Deep cycle and Marine Starting batteries which have a much sturdier construction than automotive starting batteries but do not put out as many cranking amps for their physical size.

Fast charging literally drives lead off the plates and greatly decreases battery life. Enough current must be applied to stir the electrolyte as it is a chemical reaction taking place through the application of energy. 6 amps is good minimum for boat size batteries and 15amps is a safe maximum for large deep cycles size 29 and 31. Smaller deep cycle batteries will have a lower maximum. Heavy duty Marine starting batteries can take a higher charge rate than Marine Deep Cycles due to a plate design that has more surface area for cranking amps. Smart charges are nice because they reduce the amps as the resistance increases which decreases the heat on the plates which leads to lead being shed and eventual shorting of the cell. Batteries have a bottom section below the grids for collecting the debris but it is best not to fill them up as the debris bounce around as a boat pounds aginst the waves.

Minnkota wisely limited their rate to 10 amps although 12 amps would still be safe for most batteries. Fast charging (more than 15 amps) of a Deep Cycle battery does a poor job completely charging a battery due to the internal resistance of the battery and resulting high heat and is best for emergency use and again it will shorten the battery's life. Fast charging as stated by ST also boils off the water which can expose the plates eventualy. The alternator of an outboard has a voltage regulator and does not always put out max amps when not required and is not designed to always put out maximum amps. If it did it would likely overheat and fail as it is only designed for short periods of maximum output just like a car. It is not a heavy duty alternator like say a bus which has heavier windings to sustain long periods of high current. My problem with the system as "explained by previous posters" is that some units may take out the outboards alternator windings due to high constant draw causing overheating in the windings (a very expensive repair). Again Minnkota seemed to take a cautious approach for good reasons.

I do not own or have any interest in either devices but I do possess electrical knowledge to cut through all the marketing hype. I am a thrifty German who hates to throw away money and have spent many years researching batteries of all types in addition to my professional training in electronics. I regularly get around 8 years out of a Marine deep cycle but I do not buy cheap batteries either (however I have connections and get a nice discount). I am impressed with Interstate but even they can be quickly ruined by improper care. Penn is another good brand and has manufactured Interstate batteries under contract in the past. ST you are spot on about what likely happened to your batteries however old batteries take even less abuse before failing. I have heard from credible sources about true deep cycles used in solar powered homes lasting over 20 years but bouncing around is much harder on batteries.

Sorry so long but I do not post here much and thought some of my knowledge may help some but not the battery manufactures sell more batteries. Another thing some do that toasts batteries is to leave a manual charger plugged in all the time. It slowly boils them dry even if set at a low rate. Manual chargers must be carefully watched. There is much more to increase battery life. Feel free to move this to a new post if you desire ST.

[pheasantpete]

A search of "Are DC alternator chargers worth the money?" will give additionl info. If I had one I would go with the Minnkota. I personally would not have one as my motor already charges my two batteries that are in parallel for starting and my stern electric trolling motor. I have 2 batteries up front in serial and if they start getting low I will switch them with the rear batteries. Having 2 parallel batteries in the back ensures great cranking power and output due to less resistance and resulting efficiency otherwise given up as heat loss. The higher the current draw in a battery the less amp hours output. Always match your cells when running batteries together same size, same manufacturer, same production date, and equally charged or one can discharge another.

It is physics not inferences that matter. Batteries do not care what someone thinks they know. The laws of physics could care less.

[pheasantpete]

Problems with fast charging lead acid deep cycles: 1. Shedding of plate material-it is forever taken out of the capacity and can potentially short the cell 2. Imcomplete charging- you will get a false high voltage which indicates fully charged a. after the battery settles for a day you may not have enough surface charge to crank the motor b. The lead sulfate crystals will grow in size in a partially discharge battery (which previously indicated full) and become impossible to remove 3. an Inefficient form of charging due to much of the energy being lost as heat from pushing high current through a battery

It is best to charge at the right amps for the battery. 10 amps is safe and reliably stirs the electrolyte. 6 amps will stir a single battery but takes a long time to recharge. Save 15 amps for the big boys or two in parallel and I recommend a smart charger that kicks it down when the batteries become nearly full.

Without enough stirring stratification in the cells can occur. Sulfuric acid has a higher specific gravity and will sink to the bottom and water will rise to the top. 2 amps is great for topping off a battery after moderate rate charging but not for discharged batteries. Smart chargers take out the guess work. I still like a manual 2 amp for removing some sulfation after the smart chargers quit charging. I occassionally leave one on for a day or two and get some capacity back by slowly removing some sulfation. It will not bring back an improperly cared for bad battery. There is a theory about pulsing batteries (special charger) to do so but that has limits as well.

Finally always check your levels and only put in enough distilled water to cover the plates and a little more. Most batteries have a little plastic tab indicator to indicate the fill level. Never fill them all the way up as it will vent and remove sulfuric acid from the chemistry lowering the potential capacity. Forget about additives as they have many drawbacks and are only marginally extending the remaining life. Better to put that money into new batteries. Again I hope this helps some with charging set ups and extending their battery life.

[CaptainMusky]

Muskie if you have shot batteries in 3 years as you stated then you might want to figure out what you are doing wrong before giving any more battery advice. Deep Cycles are extremely rugged and will last for at least 2X that if taken care of. I do however appreciate you response about your recent experience just be careful about presenting anecdotal evidence as a hard fact.

First of all, my comments with this unit are my experience. It is fact because that is what I observed. No making stuff up or candy coating. I clearly stated that this was MY EXPERIENCE, and it may NOT work for everyone out there because I know there are limitations with a system like this and not everyone would see the benefit or would it make sense for them to purchase one. IMO longer runs between spots and an outboard that has a sufficient alternator output are the big keys. If your outboard puts out 12 amps, dont even bother.

Regarding the life of my previous batteries it could be a combination of a couple factors that lead to that which I believe I outlined earlier which you failed to pick up on. 1) they were "dual purpose" batteries NOT Deep Cycle. I bought them with the boat, and honestly never paid attention to what they were nor would I at the time knew the importance of one vs the other. Rookie mistake there. 2) the one battery that was shot I believe ended up freezing. Combination of factors. Low water and the charger I was using wasnt working as well as it should are the two main reasons I think it failed. The other battery was fine. Still had 12.6 volts, but I am not about to change one battery in a system, they are both getting replaced.

I changed my cranking battery as well because I was having issues with the GPS turning off when I start the outboard. Thinking this would help resolve that problem. Well, it didnt, but I now have a larger cranking battery anyway with a bigger reserve capacity so I can play the radio, run lights, livewell, etc without much concern.

[Whoaru99]

The altanator puts 50-60 amps back at your starting battery everytime you run the big motor, Why does it not kill the starting battery?

HTB

Well...yes and no.

Starting the engine, assuming a relatively normal start, doesn't take too much charge out of the battery. Once the engine starts and the alternator comes on line it will charge until the system voltage is equalized. Since the battery isn't discharged too much the alternator may put out high current (but not necessarily full current) only for a very brief time and then soon the charge current to the battery drops to almost nothing. Point being, it's not like the alternator is constantly hitting the battery with the full amp potential of the alternator.

Net charge current to the battery, I believe, would be (alternator voltage - battery voltage)/ internal resistance of the battery.

So, for example, say the battery voltage is 12.6V and the alternator voltage is 14V. If the battery internal resistance is 50 milliohms, then charge current would be approximately (14-12.6)/0.05 = 28 amps. However, considering the depth of discharge in this example wasn't too great, the battery terminal voltage will rise fairly quickly and as that happens charge current drops. Essentially, when the battery voltage reaches the alternator voltage, charge current would be theoretically zero. Not sure that it ever actually achieves zero, but it certainly drops to a very low charge rate when there is little difference in voltage.

[Rockin Rod]

OK, here's my experience with the Minnkota....

Fished 3 days, using trolling motor probably an average of 5-6 hrs a day. At the end of each day it was never under 3/4 charge using the test button on the trolling motor. I probably put 15 miles on a day on the big motor running, typically 2-3 mile runs. When I got back to the access my batteries were on full charge after the 20 mile run back in.

I wasn't sure what to expect because I only have a 25 amp alternator on my motor, but overall I am very pleased.

[CaptainMusky]

OK, here's my experience with the Minnkota....

Fished 3 days, using trolling motor probably an average of 5-6 hrs a day. At the end of each day it was never under 3/4 charge using the test button on the trolling motor. I probably put 15 miles on a day on the big motor running, typically 2-3 mile runs. When I got back to the access my batteries were on full charge after the 20 mile run back in.

I wasn't sure what to expect because I only have a 25 amp alternator on my motor, but overall I am very pleased.

Great news! Looks like it worked pretty dang good to me. Thanks for the feedback!

Still really happy with my Stealth DC as well.

Just curious, do you have a digital gauge installed that you can watch when your outboard is running to determine if the trolling batteries are being charged?

I do and find that really helpful. I have the voltage displayed on my HDS and its automatic when that voltage hits 13.0 volts on the cranking battery (displayed on HDS) I can then see the voltage on my trolling batteries increase. Pretty cool.

My wife even liked it and she has no idea what it does or how it works. LOL

[PropsterII]

Two trips to LOTW on my Stealth now, one 4 day and one 7 day. Shortest day we fished was maybe 8 hours and that was due to wind and storms, otherwise most days were 15 hrs. This thing works great. Never got low enough on the trolling motor batteries that we couldn't fight the wind and control the boat. Even though we had to run the trolling motor on high quite a bit. It will be several years (I hope) before I'll know whether the other main benefit of the system actually works, and that is prolonged battery life due to the constant charge preventing the sulfation of the batteries that occurs normally. We'll see but so far this thing is awesome for guys that use the tm long hours but do decent length runs with the big motor in between.

[Kyhl]

This is definitely top on my list of upgrades for next year. Just returned from a weekend trip where I rarely left the boat. Slept in the boat Saturday night.

Too keep the trolling batteries pumped up I used a power inverter to power the regular onboard charger on longer runs. We joked that were running a 150hp generator a la Tim Alen.

[CaptainMusky]

We joked that were running a 150hp generator a la Tim Alen.

MORE POWER!! LOL

[PropsterII]

That's what we used to do was have the Honda 2000 generator (borrowed) on board with us all the time and charge during the day while fishing.