Lithium-Ion batteries represent a great opportunity to save weight on a fast cat.

Trying to explain the benefits of Lithium – Ion batteries, we couldn’t do a better job than Sailing Today’s James Turner in the June 2010 issue.

Below is a summary of the article. To read the full version, click on the link below the summary.

“Most of us know of Lithium-Ion (Li-Ion) batteries because we use them in cameras and in some models of hand-held VHF radios. You may have noticed they are very light when compared with conventional batteries. You may also have noticed that they charge very quickly. [..]

Now let’s look at the power of the battery. As I write this, the only model on the market is 24V 160 Ampere/Hour (Ah), but a 12V 320Ah model will be available by the time you read this, so I will focus on that model for technical comparison. A lead-acid or gel battery generally doesn’t get filled right to 100 per cent capacity by the boat’s engine. It normally only goes up to about 90 per cent. Only if you are connected to mains in a marina, for a long slow trickle charge, can you expect to go to 100 per cent. When you use the battery, you discharge as much as 50 per cent of its capacity, so unless you start out from a base with shore power you will only get 40Ah out of a 100Ah battery. The Mastervolt Li-Ion battery charges to 100 per cent with no problem, due to the very low internal resistance. You can readily discharge it to 20 per cent capacity, so for every 100Ah battery capacity, you can use 80Ah before charging. What’s also very interesting is that it only takes one hour to charge – but more about that later.[…]

Next, a look at the life cycle of the battery. This is not primarily dependent on the age of the battery, but the number of times it has been depleted then recharged. Manufacturers’ figures vary, but most lead-acid and gel batteries have a life of between 500 and 700 cycles. For our comparison later, we’ll take the average as 600 cycles. The Mastervolt Li-Ion battery, however, will give you up to 2000 cycles. […]

 The 12V 320Ah Li-Ion weighs in at 48kg, which is 6.66Ah per kg. The equivalent AGM batteries from Mastervolt – 4 x 160Ah weigh a total of 172kg. I have said four AGM batteries, not two, because the ‘usable capacity’ of the Lithium-Ion batteries is twice that of the AGMs – 80 per cent against 40 per cent[…].”

PDF File Sailing Today Lithium-Ion Battery