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New trolling motor decision

7518 Views 40 Replies 20 Participants Last post by  MariettaMike
I am considering adding a TM to my Maverick 17 HPX-V. After speaking with several very reputable installers, most suggest the 24v system which I agree is the safe way to go but to keep all batteries in console I would need to reduce the Reserve min to 80-90 [email protected] Amps for the battery sizes to work.
A 12v system would be the easiest install and I have not ruled that out as I could install one grp 29 battery and get 210 RC min’s
Here’s where I could use help.
Different conditions require different amounts of thrust so to provide a simple comparison, the 55# MK draws 50 amps at max which will burn through a RC 120 battery in one hour. If I go 24v, the MK 80# using 55 lbs of thrust uses 38.5 amps based on 56 max amp draw x 69% of max thrust. In other words, if my math is good, the 80# motor requires roughly 75% of the amps to achieve the same thrust as the 55# motor. I am using terrova numbers here.
When I read comments like “if you fish in wind and current then go 24v” doesn’t that simply translate to more thrust for longer?
It would be great if anyone with my skiff would respond and/or anyone who would set me straight on what I am missing in my analysis.
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I know you said you weren't ready to go lithium, but if you really do your research you will find that the cost is only slightly higher than a quality AGM battery for comparable performance. For instance you don't need to buy a 100ah lithium battery to perfrorm the same as a 100ah lead battery. I put a 12v lithium battery in my 17' skiff to run my trolling motor almost a year ago and no regrets.
I have a deep cycle wet cell marine battery for my house. It is in the center console and used for cranking as well as GPS, bilge, livewell, lights, etc. I have the TM power in the front hatch.

I bought from a local company Lithium Ion Technologies which has the batteries made in China. Another local company Green Life buys the same batteries from the same factory. I'm sure there are others doing the same thing. The 12v trolling motor drop in replacement they suggest is the 50ah battery which gives comparable performance to a 100ah lead battery. Without getting into a technology monologue or sparking a big Elusive Porpi says lead batteries can effectively discharge to about 50%. Any lower and the output significantly drops making them useless from a practical standpoint. Additionally discharging wet cell batteries below 50% and AGM batteries below 75% significantly lowers their effective life. A LI battery can provide full output all the way until they are discharged to 85-90% at which point an internal Battery Management System controller shuts them down.

As far as cost, the price is about 2x the price of a high quality AGM such as an Optima Blue Top or similar. But an expected 10 times more discharge/recharge cycle life justifies the higher price in my opinion.
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Please note lithium batteries have serious hazards associated with them. If they are overcharged, they can catch fire and essentially melt a boat. They have internal charging circuitry that is required to regulate the charging cycle unlike a lead acid battery. A failure in that internal regulator can easily cause a fire. Lithium itself will catch fire when exposed to water as well.

Their have been recent airplane fires due to lithium issues. Samsung notoriously had lithium battery issues that set phones on fire. Lithium batteries are an impressive technology but it is still a new technology that comes with additional risks. Given the rate of equipment failure on a boat (water intrusion, vibration, etc) I would be very cautious about new technology that can effectively sink a boat in seconds.

Also something to keep in mind if a lithium battery catches fire, pretty much nothing puts it out until the entire battery is consumed. A fire extinguisher is of no use.
Not all lithium batteries are the same, nor do they carry the same risks. The current generation of portable lithium power uses a Lithium Iron Phosphate (LiFePO4). This is not a Samsung phone that fits in your pocket. Small electronics such as phones actually use a different electrolyte Lithium hexafluorophosphate (LiPF6) and the plates are much thinner making imperfections and flaws much more likely to cause a short and overheat....and it is still very rare outside of a design flaw in a specific model phone.
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PV redfisher. Would you mind specifying what size odyssey house battery and how you are recharging them? As an update I spoke with a guide here in Charleston this morning who runs a pro w/70 LA and he has the MK 70/24v and uses the pc 1200’s and says he easily goes 6 hours chasing tarpon. Can I assume you also have the 70? And are you recharging house off O/B and TM’s off battery charger?
Thanks and thanks again for those new comments
I know a lot of people use odyssey PC batteries...mostly because they are small and light I think, but they are still lead acid chemical reaction batteries and smaller and lighter means less potential energy. Also a PC1200 has 30% more capacity (and weight) than a PC925. The PC batteries are designed for personal watercraft and need to be sealed, extremely durable and able to be mounted in any orientation since they are subject to lots of shock and extreme conditions. Sealed AGM batteries are are ideal for this application.
In a somewhat watertight hatch on a skiff, I've never really seen the NEED for anything more than a wet cell lead acid, I'm not discounting there are advantages to sealed AGM over wet cell but at a price of perhaps 3x per ah with no weight savings I don't really see much benefit.
Now when you get to Lithium batteries, you get all the benefits of the sealed AGM PLUS you get significant weight savings and the ability to discharge with full output for the entire cycle. I don't really try and convince many people to try Lithium batteries because honestly it probably barely makes financial sense, and the weight savings are probably not necessary for most skiffs...I mean if you have a TM to begin with you aren't exactly a minimalist and the extra 1/2" of draft from heavier batteries isn't going to be that much of a difference maker.
The bottom line is that a standard deep cycle wet cell battery for $80 at Walmart, Sams, Costco or similar is almost always going to be the best financial decision for a power storage solution....but most of us don't own skiffs because they make financial sense...let alone add on the cool stuff to them for that reason
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