Electric only power

[gnappi]

So, I'm done with offshore fishing, $250 gas fillups, and maintenance on salt water boats and engines. My new love is electric power and "quiet" fishing, gliding through the lakes and ponds without a sound.

My bugaboo is the battery power. I bought a group 27 96Ah AGM cell for my Minn Kota 50 and I have been running it 4 +/- hours some at full speed, most at low speed and the meter on the Minn Kota battery power center sneaks below the 1/2 charge (Yellow) into the red zone. I have no idea how much range or time I have once I dip below 1/2.

So in order to not have to paddle by pushing the battery into the empty zone or cut short my day unnecessarily for fear of having to paddle back, I'm thinking of one of the following options, any opinions would be greatly appreciated.

1. Get a small ~35ah AGM deep cycle battery as a get me home backup. Cost is not a biggie at around $65 delivered, the penalty is weight and space on my 10' topper.

2. Get a 100watt solar panel and PWM charger controller to constantly provide charge current to "top off" the AGM battery while fishing. Rating it conservatively I can get ~ 5 amps of current in full sun.

In Florida we get plenty enough sunshine to keep me going. Cost is ~$150 also do able and a better option than paddling. Weight is FAR less than option 1 above, but I wonder if anyone has tried this before to extend their time on the water. Will the constant charge / discharge kill the battery?

3. The LED's on the "power center" don't really say much, so I'm thinking a voltmeter will tell me more. What is the voltage "danger zone" of when the battery should be expected to burp and shut down? Does anyone in here have one of these power centers that can tell me anything about the "Red Zone" on the MK power center?

 

[gnappi]

Well I seem to have found some answers, sort of...

Regarding charging when the battery is not low... Charging when the battery is VERY low is much less desirable than charging it with a substantial amount of charge left. They also have a voltage vs. state of charge table which I can go by with a voltmeter I can read under load, but the trick is knowing at what voltage my TM will conk out.

https://www.solar-electric.com/learning-center/batteries-and-charging/deep-cycle-battery-faq.html

 

[Captain Ahab]

I would go fishing on a full charge until you get your low reading. If there is not much wind troll around the launch until you kill it to get an idea of how much you have left - you will feel it start to slow down so that is you clue to get up wind of the launch just in case

 

[mbweimar]

Gnappi, I feel your pain. I have an 88 Mako 231 that I fish out of the St. Lucie inlet with. It doesn't get used much because of the fuel.

I've done some testing with solar chargers while fishing, and I've found it takes several hours to get even the smallest amount of charge. Unfortunately it would take a solar panel too large to fit in your boat to make any difference.

My thoughts would be to put another group 27 battery up front in parallel to double your capacity.

 

[gnappi]

I wound up buying a group U1 AGM deep cycle battery as a "spare tank" sort of deal. They're light and it should get me home in the event of my main battery going dead or failing. I'll do whatever it takes to not use an engine again.

I added a voltmeter on a sort of dash panel I made up to watch the state of charge / discharge. The one thing about Jon boats I don't like is the lack of information display and electrical system control. I really don't like diddling connecting and disconnecting cables for lights, depth finder, bilge pump etc.

 

[gnappi]

Today now that it's finished, I went fishing for the second time in my 10 footer, and upon launching there was a fellow pulling and pulling and pulling on his engine's start rope. Poor dude, I thought he was gonna stroke out I was maybe a mile away and heard him zoom away from the dock.

I remember those days all too well, I need these images to reinforce my no gasoline engine decision

Anyway... I spent 5 hours on the water (hoping not to need my spare battery) none of that at anchor or drifting and after all that time my original battery was still showing 12.1 volts under load with the throttle at 4 and I had no sign of the motor weakening while the MK charge state LED's said to recharge. Maybe I didn't need a spare deep cycle cell after all.

This is my first TM and I'm still unsure about the performance curve of deep cycle batteries so I found a graphic online and it is in disagreement with the Minn Kota battery charge state indicator on their wowie zoomo (read as pretty expensive) battery box. at 12.1 volts under load I'm reading that I really am around 55% charge?

What are you folks who may be using electric only or spending a lot of fish time on your TM finding in real life usage? Does this graphic make sense?