Ultrex 36v 112 - Battery Run Time

[Junger]

I have an electric lake only that is pretty big. I'd like to get 5-6 hours of fishing there and the group 27 wet cells that came with my boat weren't cutting it, I could only get about 3 hours tops. I put in some Duracell Platinum group 31 AGM's, rated for 105AH and 200 min reserve capacity.

 

The max draw for the Ultrex is about 50amps on speed 10. If I aim to deplete the AGM batteries by 60%, my math seems to be that I'll only get about 1 and a quarter hour of full speed operation. (105AH / 50amp * 60%). I obviously don't plan to zip around the lake on speed 10 the whole time, but there are some parts of the lake that are 2-3 miles apart and it takes 20-30 mins to move from one part to another. Is my math right? I'm trying to figure out how I can stay out on the lake longer.

[MN Fisher]

Math looks right to me. I'm in a TM powered canoe, so I have to watch my battery level the entire time I'm out.

[gunsinger]

I too fish an electric only lake and my poor little 12v doesn't do well at top speed all day.  If I stay at about mid-speed, I can fish all day but at top, I'm lucky to bet 3 hours, depending on the prevailing winds.

[Junger]

4 hours ago, gunsinger said:

I too fish an electric only lake and my poor little 12v doesn't do well at top speed all day.  If I stay at about mid-speed, I can fish all day but at top, I'm lucky to bet 3 hours, depending on the prevailing winds.

 

Good point, I don't think the amp draw is linear based on a post from another forum. I may just have to run across the lake at a lower speed.

 

[Deephaven]

When Lithium's that will last 2-3x as long as the AGM's per charge and take 5-10x's more charges are only $499 vs $300 for the AGM and way lighter I am not quite sure how AGM's are still being sold.  If you really need juice Lithium power is the solution.

[Junger]

7 minutes ago, Deephaven said:

When Lithium's that will last 2-3x as long as the AGM's per charge and take 5-10x's more charges are only $499 vs $300 for the AGM and way lighter I am not quite sure how AGM's are still being sold.  If you really need juice Lithium power is the solution.

I bought the boat new off the lot (i.e. not a custom build) and it already had the overpriced $800 quadpro 4 bank option installed and can't handle lithiums. But if/when I redo the electronics, I'll rewire the boat for lithiums and also add a DC alternator switch to the TM battery bank.

 

The 31 AGM's were $159 before taxes, Duracell Platinums which are rebranded Deka's made by East Penn. Hopefully when I'm ready to rewire/repower batteries lithium will drop down a little more.

[NHBull]

There is no good solution.

Your math is solid and you will likely draw your batteries down lower than you would like.

 

Lithiums are in your future, but i here they are back ordered for the year.

 

Modify the water you want to cover and perhaps anchor instead of spot lock 

 

......I know you know this

 

 

[Johnbt]

What is your mph at 50% power vs mph at 100% power? Do you really get that much more speed running wide open?

 

I know I don't. I have a heavily loaded 1648 with a Maxxum 70 and an Endura Max 55 (and nice seats, 2 200-pounders, and carpet, and an extended rear deck, etc) and the boat will only go so fast. Running the 24v on the bow at 50% and sometimes the 12v Endura Max at 50% to get an extra 0.5 mph is about it. My 2 group 31 Duracell AGMs last all day - 8 to 10 hours - and aren't anywhere near half depleted. The third AGM is for the Garmin, bilge pump and the Endura Max. The Endura Max is mostly for unloading/loading and backing up to free snags or out of laydowns retrieving lures.

 

It performed the same way for six years running the $99 group 31 batteries from Walmart. My friends and I got away from them when the quality became spotty.

[Junger]

2 minutes ago, Johnbt said:

What is your mph at 50% power vs mph at 100% power? Do you really get that much more speed running wide open?

 

That's something I'll have to check. Next time I redo my rod locker storage and pull them all out to access the batteries, I'll put the ultrex down and test amp draw, and then on the water test the speeds and figure out what's optimal. 

[Logan S]

I fish the same lake you're talking about and use three group 31 batteries for my 112 Fortrex.  Mine are Interstate, but same specs as you listed....They work well and while I can certainly run them down, it would take a lot of 'running' (like the back of Seneca to the back 10-Mile in the same day).  

 

I used to have 27's but they weren't cutting it for a full day.  I plan to go Lithium the next time I need batteries but that's not for at least 3 years...Hopefully by then they'll be a bit more affordable.  

 

When "running" I usually don't go above 80%...Only like one or two tenths of a MPH difference between 80% and 100%.  

[slonezp]

On 5/20/2021 at 5:21 AM, NHBull said:

There is no good solution.

Your math is solid and you will likely draw your batteries down lower than you would like.

 

Lithiums are in your future, but i here they are back ordered for the year.

 

Modify the water you want to cover and perhaps anchor instead of spot lock 

 

......I know you know this

 

 

Lithium batteries are not the future. It's old technology with other stuff is in the works. I'm not a tree hugger and never will be. Mining lithium is bad for the environment. 500,000 gallons of water are needed to mine 1 metric ton of lithium.

https://www.instituteforenergyresearch.org/renewable/the-environmental-impact-of-lithium-batteries/#:~:text=The lithium extraction process uses,rich brine to the surface

[Way2slow]

There is one flaw in your math.  A 105 Amp hour (Ah) battery is only rated at 105 Amp hour with about a 5 amp draw on it.  They use the 20 hour rating.  So, if you only drew 5 amps off the battery you could use your math.  Not very realistic.  

As the current draw increases, the Ah capacity decreases.  The exact formula for that, I don't have, it can vary somewhat with the type battery, but it is a rather significant reduction.  At 33 amps, it could be as much 25%.  

If you use the Reserve Minutes (RM) rating, that will get you a little closer to a realistic number.  The Duracell batteries are made by EastPenn and they use a 23 amp rating, some companies use a 25 amp.  What that means is a fully charged battery will run the RM time with a 23 amp draw before it's fully discharged.  Now, since it's harmful to most batteries to fully discharge them, you need to reduce that RM time by about 20 - 25%, the leave some charge in the battery.  By then, you are going to be moving so slow, they are almost useless anyway.  

Then you have to figure if you are going to be drawing 33 amps, then you have to reduce it another 10 or 15% 

So, what you have is some batteries that are closer to about 75Ah instead of 105Ah if you plan on running them at a 33 amp draw, and then leaving at least a 20% charge in them, you find your run time is a whole lot less than your math says it is.  

You actually went the wrong direction when you went with AGM's if you wanted max run time.  An AGM, group 31 is a 105Ah, a group 31 in a good flooded cell is about 130Ah. 

The lead acid battery that's going to give you the absolute most run time, is the Trojan SCS225 but you are not going to run down to Sam's Club and buy one of those for $175.  There's not a lead acid battery on the planet in a similar size battery that's going to beat it.   

 

I just noticed the chart you had with speed and amp is for a 80# 24V.  If your 36V 112# motor is 50 amps, that's a huge load and you can reduce my numbers even more

[Junger]

13 minutes ago, Way2slow said:

I just noticed the chart you had with speed and amp is for a 80# 24V.  If your 36V 112# motor is 50 amps, that's a huge load and you can reduce my numbers even more

I figured I was missing something. I was able to get out back on this lake last week, and I hit the spots I wanted to, and with a mix of reducing speed to #8 on the Ultrex dial, and using spot lock less, I was able to stay out on the lake without going below 50% (per the TM remote) for 7 hours. Thanks all for the feedback.