Tom Cooper explains his lightbulb moment!

Thanks to Elon Musk, heavy-duty Lithium batteries have come along way in a very short time and as the technology develops it finds ever-increasing applications and consumer volumes. This ‘space-age’ technology has now moved well within the reach of most yacht applications, especially for the large capacity house battery bank.

All yacht manufactures, including Kraken, are continuing to fit AGM or Gel batteries as standard, since the cost of these batteries is only 25 % of the cost of Lithium.

I began investigating this subject assuming that I would prove that Lithiums, although they are more expensive than AGM’s, due to the benefits they provide, are well worth the extra initial outlay.

My analysis prove that, despite a higher initial cost, Lithiums will, even over a fairly short time, be far more cost-effective compared to AGM or Gel batteries.

Analyzing the benefits of Lithium can be subjective, according to the use of the equipment on board and the type of use dictated. Here we are focusing solely on a blue water long-range cruiser application.

  • Extended life onboard
  • Increase in creature comforts – A/C, Safe electric cooking, computers etc.
  • Improved options in recharging – solar, wind, larger alternators, generators
  • Conserving fuel, restrict charging time from running generators or main engines

The comparison

Here’s how a 10,000 Euro plus upgrade will provide a significant financial advantage!

Simply compare two batteries (thanks to Battery Works Pty Ltd – Technical Team for info)

  1. Victron AGM 220 Ah usable energy measured, discharge @ 50% has a life of 500 cycles
  2. Victron Lithium 200 Ah usable energy measured to discharge @ 85% has a life of 2500 cycles

In the table (right) Lithium costs approx four times more than the AGM but last conservatively 4.5 times longer.

Therefore the cost per Ah over the life of the battery bank is approx the same for Lithium and AGM. However Lithium is installed once, while in that time you will need to pay four times to replace the AGM’s – so add on the future cost of procuring and installing AGM replacements. The difficulty of removing these very heavy AGM batteries should be considered too.

Over the lifespan of one lithium battery, the overall cost of using AGMs to match lithium would cost over €700 more.

Now the big win that no one seems to consider…

Charge at 30% say 60 Amps. This is the Bulk Charge (80%) rate, the remaining 20% absorption rate slows even further. 

Can charge at 200 Amps, but we’ve used only 100 Amps allowing very ample capacity for running other on board systems, assuming you have this capacity from your generator, which on a Kraken you do.


Lithium batteries for the same capacity are:

  • 50% smaller 
  • 60% lighter
  • Cycle to 85% instead of 50% with AGM so you don’t need to recharge as often
  • Last over 4 times longer 
  • Save the cost of reinstalling replacement batteries 4 times over the lifespan of a lithium battery.
  • Reduce generator run time for recharging batteries by 75% therefor reducing diesel cost to 25%  

Another significant benefit that Lithiums offer is the ability to increase the battery bank to allow silent running of the air conditioning system, powered overnight by stored battery power and inverters alone.

This would not be possible with AGM or Gel batteries as the weight and space required would be prohibitive on a sailing yacht.

Lastly Lithium battery technology is moving very quickly and there are now two different types of lithium batteries that are compatible for sailing yachts:

  • Lithium Ion 
  • Lithium Iron Phosphate

Lithium Iron Phosphate is later technology and, whilst being a little more expensive at this time and a little heavier, is also much more stable and has a greater life cycle.

So at Kraken we are offering Lithium I P as our lithium upgrade.

AGM is still a reliable and affordable battery option but initial owner budget constraints are the only real argument against installing Lithium IP batteries from the start.

The evolution of Lithium batteries and charging technologies is here now and offers some fantastic benefits to the blue water/ liveaboard sailor.

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