It's Battery time !!!!

[newbiedmv]

Time to get at least one new battery. I'm running a 12/24V system with a 55 amp at 24 V  max draw on the electric motor. I usually cook a Walmart 12V deep cycle (the second biggest) every few years.

Now and then i look into the 24V lithium batteries  but discount them due to cost and the cost of the charger.

Anyone had any luck with them? I mainly cook the walmart batteries on electric only lakes drawing 20 amps or more fighting the wind getting out on in.

[casts_by_fly]

Which Walmart batteries are you using as your baseline?  You said the second biggest one.  That’s the group 27 banshee on the website right now. That’s a group 27 with 77 ah capacity for $280 ea. For two, that’s $560 for 24v 77 ah. 
 

in an amped outdoors lithium (my current brand) you have a couple options to get you comparable performance. If you want exact capacity, then two 80 ah for $1120 is the right comparison. However, if you run down your lead acid to 30-40% you’re about done for the day. That’s a usable capacity of (maximally) 55 ah and possibly 48 ah. In lithium you can run them down to 10% reliably. That 48-55 ah effective range in lithium calls for a 50-60ah setup.  The other benefit of lithium is that it holds the charge longer into the cycle, so at 50% it outputs the same as full.  It means if you’re running closer to the limits you still have the performance whereas with lead you are slowing down. It also means with lead you’ll be turning up the motor to accommodate and burning it faster. 
 

Back to lithium, a pair of 60 ah is going to be $760 and going to be a great slight upgrade option. More capacity and better overall performance. You’ll need to add a charger for $140 (genius 2 bank). If you don’t fish back to back days no don’t mind swapping batteries then a single bank is $100.  Or, a 50 ah 24v is going to give you the same capacity with better performance during a charge for $800 including the charger. If you couldn’t tell with lithium, the price is proportional to the amount of total capacity. 
 

the lead alternative is the group 31.  If weight isn’t a problem, the marine group 31 banshee is 105 ah and $320.  For two you’re at $640.  Effective capacity is about 70 ah. That’s equivalent to the pair of 80’s above. It’s about a 2x cost difference.  Will you get 2x life out of lithium?  If you’re cooking a lead battery in 2 years then I’m going to say yes. Lithium has a claimed life of 10 years with normal use and good charging. I don’t have that much experience with them, but even if you get 6 you’ve broken even vs the lead, lost weight, and not had to worry about it for 6 years. Any life past that is cake. 

[newbiedmv]

Thanks. I've only considered the one 24V.

Battry weight is a concern  not so much for the boat but for my back. I have a standard marine cranking battery ( for a 50hp 2 stroke)as the other and it seems to handle the draw fine.

I'll think about it, the last few years have been bad fishing local reservoirs, way to many kayaks and people. It makes  fishing, launching and loading miserable. Unfortunately they don't have very good sense on the water. I'll have to check on the room for 2 12v batteries 

[Bankc]

Check out Amazon for lithium batteries.  They have a bunch on there.  Yes, they're all name brands you've never heard of from China.  But, the truth about lithium batteries is that just about all of the components, and certainly all of the cells, are going to be made in China anyway. 

 

I'd also recommend checking out Will Prowse's YouTube channel, as he tears down a lot of these batteries and shows and discusses their guts and helps you figure out which ones are good and which ones should be avoided.  That way you can get the price down to something approaching the value of a lead acid battery, as lithium batteries should last for 7-10 years.  Even 12-15 years isn't unreasonable.  A deep cycle is only rated to last somewhere between 200-800 cycles.  A LiFePo4 lithium battery is usually rated to last 2,000 to 5,000 cycles.  So double the lifespan should be expected, and even triple or quadruple is quite possible.  

 

You won't get the product support, some of the features like bluetooth monitoring, or much of a useful warranty with the cheaper Amazon batteries that you will from a brand name, but chances are you probably won't need any of that.  Plus, with the Amazon batteries often being less than half the cost of something like a Battle Born or Dakota, you can buy a replacement battery should yours fail prematurely, and still save money over the big-name brands.  Plus, ordering a replacement off of Amazon will probably arrive sooner and with less hassle than fulfilling a warranty.  

 

As for a charger, look into the Noco Genius chargers.  They do lithium (and lead acid and AGM) and they're fairly affordable and of excellent quality.  

 

This is the route I took.  I got a 50Ah Weize LiFePo4 lithium battery and a Noco Genius 5 charger for my kayak trolling motor.  And since lithium batteries can be drained to about 90% of their capacity, versus only about 50% for a deep cycle lead acid, it's more or less the equivalent of a 100Ah lead acid battery, while only taking up half the space and weighing about 65 lbs less.  Even a 100Ah LiFePo4 battery only weighs about 30 lbs, which is about 50lbs less than a Group 31 lead acid.