BOS: the encounter between lithium and lead batteries


If there are only lead batteries on board, when they are worn out the boat owner has to choose between two options:

  • replacing the existing batteries and recreating the whole system;
  • completely changing the type of batteries and opting for lithium.

Both options have advantages and disadvantages.
AGM batteries cost relatively little, much less than the lithium battery, but can only be half used and don’t last long (generally 2-3 years).
On the other hand, lithium batteries last longer, weigh less, a higher percentage can be used and they have a higher charge efficiency (meaning a saving on costs); however they cost more, installing them is complicated and expensive and switching from a lead battery to a lithium battery requires a change of parameters.

BOS lithium batteries: a new and innovative solution

LE300 are lithium-iron-phosphate batteries, with a voltage of 12V, and rated capacity of 28 Ah, respectively 25 Ah and 300 Wh actual capacity

BOS offers a third option, which offers the best of the earlier two: LE300 – Smart Battery System, a lithium battery that connects in parallel to the existing lead battery, with the same charge regulator and no need to intervene on the parameters.

The only installation needed is connecting the lithium battery in parallel with the lead battery, an operation made easier by the fact that the cable diameter is much reduced; it is much lighter (3.4 kg compared with the average 24 kg of lead batteries) and occupies a third of the space taken up by the lead battery. The customer, if he does not have enough room for a large single block, can install a number of small independent blocks and connect them in parallel.

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The advantages

With this system in parallel, the lead battery works and wears out less: with both batteries 100% charged, first the lithium battery discharges and only when its energy is exhausted the lead battery steps in. In the same way, the lead battery is the first to be recharged.

In addition, if there is an energy peak the two batteries intervened to cover it together, supporting each other in turn. The company’s twin system guarantees a life of 10 years both for the BOS battery and for the lead battery to which it is connected in parallel.

LE300 uses a system based on lithium and phosphate which is extremely safe as the lithium is bound to other elements and does not react to oxygen, so even in the case of perforation there would be no risk. Quality controls are very intense, carried out twice for each single block and then also for the blocks of 2 – 4 – 6.

An 8-module pack of LE300s, allowing an extension of the on-board system of actual 200 Ah, alongside a lead-acid battery
The BOS company
BOS – Balance of Storage Systems, founded in 2014, offers energy accumulation systems into product lines:

  • LE300 – Smart Battery System batteries;
  • energy accumulation systems for developing countries. The principal market is Africa and Southeast Asia were there is no mains electricity.

One of the most important aspects for the company is to make highly functional products able to operate efficiently even in difficult conditions.

LE300 – Smart Battery System has been on the market since 2018, so far above all in the camper sector, thanks to close collaboration with Hymer (one of Europe’s biggest camper producers).

Initially the exclusive with Hymer, which believed in this product and was of great help in developing it, was total; later out there was specialisation in the camper sector, then from 2019 BOS entered the nautical sector in Germany, and since 2020 has also been involved in the Italian market.