Jeff and I are currently negotiating on a 200aH liFePo unit from this place.
https://www.lithium-battery-factory.com/product/36v-200ah-lithium-rv-batteries/#body_seleA bit less money for it than Dakota.
I have done a ton of research on these, and the companies involved.
I want 150ah minimum, but strongly want the 200ah.
Unlike lead acid deep storage batteries, if you charge a LiFePo battery sooner, when it is still at a higher percentage charged, you will get more charge cycles out of it.
BTW, you want a LiFePo battery as these do not have the fire/explosion issues related to the earlier lithium batteries that we have heard about.
A deep cycle only has X amount of charges. That's it. Which is one of the reasons you are instructed to take them down low before charging them. They are built to handle this, hence the "deep cycle" designation.
Unlike car and boat starting batteries that are buiilt for super high current draws for short bursts, and require steady charging.
Also, after each charge you get a reduced ah available from the battery. They age and you realize this.
So each cycle lead acid batteries give you less time out on the water.
LiFePo batteries do not act this way.
500 charge cycles is a tad low if a guy were to seriously take super good care of his lead acid deep cycle batteries.
So let's say 600 charges.
And I know that if you buy larger 200ah LiFePo batteries, and only use say 150ah of them, that 2000 charge cycles now goes up to like 2666 charge cycles. (2000/.75=2666)
But if I inly use 1/2 (100ah), it now goes up to 4000 charge cycles.
So let's use the 3000 vs 600 and I now get 5X the life.
I was looking at $180 Duracells from Sams Club.
I needed 3 to get the 36 vdc I need, and they would only be 100ah.
(If I want 200ah I would need 6 batteries wired in series parallel)
So three (3) batteries cost me almost $600 with the sales tax (not including the core charge they hit me with either)
Six is $1200.
The 36vdc 200ah LiFePo unit is $2500 (I'm working on getting that down).
This $2500 includes the charger, overseas shipping, the BMS, and the optional bluetooth feature so I can monitor the battery from our smartphone.
So, for 5X the life, I am paying 3.125X the cost of the 3 lesser ah batteries.
And an even better deal if I can get him down to $2000.
Not to mention the savings if I went with 6 lead acid batteries.
Yup, major investment to say the least.
But huge payback.
Also, my plan is to pull that battery and take to Florida for my other boat down there during the winter.
The seriously lighter weight is a major factor here for this.
Next, let's assume I only use my boat 3X a week.
That's like every other day.
I might do this at first when retired, but doubtful it would continue.
Still, lets assume this.
That's roughly 150 charges a year.
If I get 2600 charges out of the battery it works out to more than 17 yrs.
In reality, this battery will most likely outlive me and Jeff will contune using it.
Again, yup - major outlay in cash.
But if you do the math it really pays for itself.
I have the 36VDC Minn Kota.
Now I need a battery.
We will order this thing in the next couple weeks.
It takes about 24 days to build and they say about 35 days to ship.
So we are looking at 2 months before we get it without any delays.
I want the battery in late March so this works for us.