Fogstar LiFePO4 Lithium Batteries

Fogstar LiFePO4 lithium batteries are from the UK’s largest lithium battery supplier, with exceptionally good warranty (10 years!) and pricing. They are available in 12, 24 and 48V versions.

Lithium batteries are really the only viable choice for electric boat drives, offering massive weight and space savings over “traditional” lead acid. Whilst there are some advantages to single make systems (eg powering your Torqeedo motor with a Torqeedo battery) there is no escaping the fact that there are now much cheaper alternatives on the market. Many customers don’t want to take a “leap in the dark” on this, which is why we have teamed up with Fogstar – the UK’s largest supplier of lithium batteries – to offer their Drift range of LiFePO4 batteries.

LiFePO4 is the safest chemistry of lithium batteries and indeed the only one that many marine insurers will accept. Installed correctly they are actually much safer than lead acid batteries, and much much safer than a tank of petrol or a cylinder full of cooking gas…

Fogstar Drift LiFePO4 lithium batteries are safer still, because the Drift series (that we sell) all have Bluetooth monitoring and heating pads (for charging in cold weather) as standard. They are also rated IP67 on the waterproofing scale.

First of all – with apologies to those who know this already – we need to go back to basics! The only useful comparative measure of battery capacity is Watt hours Wh, or kilowatt Hours kWh (1kWh being 1000Wh). Voltage or Amp Hours on their own do not tell you the whole story. You can calculate Watt hours by multiplying Voltage V and Amp hours Ah, for example:

• a 12V 100Ah battery has a total capacity of 1200Wh, whereas
• a 48V 100Ah battery has a total capacity of 4800Wh, or
• a 48V 25Ah battery has a total capacity of 1200Wh (same as the 100Ah 12V battery)

That is not the end of the story though, as some types of batteries can use more of their capacity than others. As a general rule of thumb:

• you can use about 40-50% of the capacity of lead acid type batteries before you start seriously affecting their life time cycle limit (number of times they can be charged/discharged)
• you can use about 90% of the capacity of lithium batteries without affecting their life, and 95% is not a disaster (one discharge to 95% has a massive effect on lead acid batteries)

So that’s where the term “usable capacity” appears from, for example:

• a 12V 100Ah lead acid battery has a usable capacity of about 550Wh (based on 45%)
• a 12V 100Ah lithium battery has a usable capacity of about 1100Wh (based on 90%)
• a 48V 100Ah lithium battery has a usable capacity of about 4300Wh

Whilst all three could reasonably be described as “100Ah batteries” you can see they’re completely different in terms of what you can get out of them! So for example in the Fogstar LiFePO4 lithium batteries range:

• the 48V-125Ah model has 6400Wh total capacity (so at 90% that’s 5760Wh usable, or about the same usable capacity as 10x 100Ah 12V lead acid batteries!)
• the 12V-105Ah model has 1280Wh total capacity (or 1152Wh usable, or double the usable capacity of a 100Ah 12V lead acid battery)

These are just examples, we can supply any of the Fogstar LiFePO4 lithium batteries – please call if not listed.