Does anyone use them? If so, are they worth the expense? Where can you get them? What is the cost and any other info would be appreciated. Thanks.

I saw some good reviews on the K-2 Batteries. They can be used in conjuction with a standard onboard "regular" battery charger. Some of the others I was told require a special charger. The good side is they weigh a LOT less than regular ones. BUT when they quit for the day they quit at one time and do not taper down their output like a standard battery. Their recycle/recharge lifespan rates are comparable to the lifespan of the 5 years I would consider for the cost comparison of replacing a standard battery. (Standard Battery approx $125+- for Group 29 and Lithium approx $800+-.) Personally I typically get 18 mo out of my batteries so I look at the replacement on that time frame. IF a person could get a discount it might be cost effective to get them along with the weight reduction. BUT with their high prices it could be just as beneficial to keep the regular batteries and replace them and endure the extra weight. I talked with one BASS Pro and he is still "on the fence" about them. The sudden output drop being a significant factor. Of course they get theirs for free so the cost is not a factor to them. They are just looking at the performance. It would be a good discussion.

I couldn't imagine them being beneficial for the cost.it would be great to save a LOT of weight....but too pricey for the average boat owner.

I am going on 6 years with my optimas. I can't see where lithium are thatch better unles you are really worried about weight.

make sure your insurance is paid up; Li's are more volatile (unplanned combustion) than traditional batteries.

What color top?

I have 6 years (09) on my Optimas also. Blue tops..Going strong.

I have to agree with the cost vs. weight savings. It's just not there yet for the couple mph you will pick up. I have gotten 5-7 years out my last 2 sets of everstarts and all I do is keep them charged. Also, there are some guys having electronics and trolling motor issues that cant be explained really and all they have done is switch to lithium. Is that their real problem, I don't know but they didn't have problems before.

There is no need to worry about lithiums unless you have already done everything else to gain speed. The x5 trollingmotor is 2mph faster than a 112 fortrex. Also get rid of your pedestal seats. Run minimum gas. Get rid of all of the clutter. Put your weight,jigs and other lead items in the back or under your seat. Put the plastic in the back or towards the stern in the front box. Cranks up front. Do you really need a full livewells for 15 pounds? Loose some water. Then get a worked prop. If you're not doing this.. Then you are capitalizing on your set up.

I have Lithionics in my boat for six years. I would normally replace my flooded ones every 18 months. Never had a corrosion issue. Never had to clean on them. They charge in less than 2 hours. They reset to tell you they are at 80% discharge(push a button). That happened once after fishing for three days and not charging to test.
I will never put a flooded battery in my boat again.
Fire? Ever see a boat burn or explode from fuel? More than I can count. Every had a flooded battery explode? I have. Twice in my face. They give off Hydrogen. Never had any electronic issues from my batteries.
Expensive? Initial cost is higher but cost per hour beats flooded or mat.
And they are lighter. Way lighter. 2-3 mph. They are the future as are electric cars and yes I have five of those and work on ICEs for a living. LMK if you have questions.

What is a ICEs?

I second that, they have been known to burn when you are charging them.

blue

In Car Entertainment systems.....a thing of the past with virtually every new car having great AVN systems as standard equipment.

I triple the consensus. I prefer my fiberglass non-crispy. Even the Boeing 777 spent some time grounded due to multiple "rapid energy release" events relating to their decision to use lithium cells. They seem to work much better in applications using smaller cells with lower amperage drain (and therefore charging currents). There have been numerous documented complications with applications attempting to use large cell arrays while the small cell applications appear to remain unblemished, possibly due to the difference in the amount of heat that must be dissipated during the charging cycle.

Yes, boats can have fuel fires. However, most fuel fires don't erupt when a boat is sitting unattended with an active battery charge cycle underway. While I could lose my boat to a fuel fire, I'd most likely be present to have some chance of fighting it. A bonfire during the night while I sleep almost assures a total loss.