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Smart Battery System


Lithium Extension Battery

BOS LE300 Smart Battery System is a fully scalable solution to enhance performance and upgrade capacity of lead-acid batteries in solar or any applications with storage needs. They can be used with new or existing 12 V lead-acid battery systems. Easy to install, by simply connecting the LE300 in parallel to lead-acid batteries. Its capacity is very flexible and can be increased by just stacking multiple LE300 in parallel until you meet your system’s needs!



Sailing & Boat

Solar Home Systems

Mobile Applications

Works with any lead-acid battery and any application

LE300 Smart Battery System can be used wherever a 12 V classic lead-acid battery needs to be extended. The scope and application of the LE300 is such that customers often inspire us with new ideas and possible application areas. Right from solar home systems in Africa to mobile homes and boats in Europe, LE300 has touched every kind of storage application you can ever think of!

Lithium for cycling.
Lead-acid for basic load.

In pure lead-acid systems, batteries often fail within one to three years, as batteries get damaged by continuous operation at low state of charge. Pure lithium systems perform way better and show longer lifetimes but are expensive and complicated to install. LE300 Smart Battery System turns your lead-acid system into a lithium system with special features. And the best thing about it: It only takes a few minutes to install before it can make a real impact in your storage system.

Charging & Discharging Cycle

With the LE300 hook up, the lead-acid battery is kept fully charged, while the cycle-resistant lithium battery takes on most charging cycles and is preferentially discharged under load. The capacity and the performance of both batteries are used optimally, so you can look forward to a better performance and a longer life span of your batteries.



Longer Battery Lifetime. At Low Costs

The lithium battery takes most of the charging cycles while the lead-acid battery provides inexpensive backup capacity. The lead-acid battery is charged with higher priority, while the lithium battery takes all surplus energy. This process helps to increase the lead-acid battery lifetime to up to ten years.

Robust housing for automobile. Protected against bad terrains

An elegant design and robust housing keeps the lithium batteries safe, even when you are driving off-road or bad roads. Thanks to an optimised sizing and variable fixing possibilities, the modules fits even in smallest of the corners. Each module is E1 certified which allows them to be installed in automobiles as well.

Easy to scale up. All your needs are covered

LE300 modules can be easily stacked together to meet your individual energy storage needs. Up to 24 (7.8kWh lithium capacity) of them, on top of your present or new lead acid battery. As mentioned, all your needs are covered!

Retrofit or extend your lead acid battery. Hybrid technology

LE300 Smart Battery System can be connected to any new or existing 12V lead-acid battery. Thanks to the intelligent design, no additional charge controller or electrical wiring changes are needed.

Low temperature resitance. Works with any climate

All LE300 modules have an integrated cell-heater, so the lithium batteries are protected against cold temperatures and perform without any energy losses. At low outside temperatures, the heating can increase the cell temperature by 5 to 10 degrees celcius.

Plug & Play. Ease of installation

With the plug and play design, LE300s are easy to install and operate. They simply need to be connected with plus (+) and minus (-) terminals of the lead-acid battery. Installing lithium batteries was never this easy.

RoHS.svg Kopie


Capacity: 25.6 Ah | 328 Wh

System voltage: 12 VDC

Battery: LiFePO4 Lithium

Weight: 3.4 kg


Exclusive partner for caravans.


Partners of Erwin Hymer Group


Exclusive partner for boats and yachts in Germany.


Partners for boats and yachts worldwide


Battery Management System (BMS): Is integrated in every LE300 modul and monitors/regulates the status of the lithium- and lead-acid battery.

Battery cable: Simply connect the plus and minus cable parallel to your lead-acid battery. If you buy more than one LE300, you will get the required cables.

Display: Shows the status of the LE300.

The LE300 is already built, you do not need to assemble it. Larger systems with several LE300 modules can be ordered pre-assembled. In this case you just need to connect them to your lead-acid battery.

In this video you see how to connect more LE300 modules and how to install the battery cable.

In this video you will learn how to prepare the battery cable and connect it to a lead-acid battery.

In this video you will learn how to connect a LE300 block to a lead-acid battery.

The LE300 can be used with all 12V lead-acid/gel batteries. The size of the lead-acid battery is not relevant, our system works with all capacities. Nevertheless, we recommend a minimum capacity of x% from the LE-capacity. The lead acid battery should have a rest capacity >60%.

No, the LE300 only works as a hybrid system.

No. You can use the LE300 everywhere a 12 V lead-acid battery is installed.

The heater switches automaticly on as soon as the cell temperature falls under 10 degrees celsius. This means concrete as soon the lead voltage >13,25 V.

In comparison to lithium system, our hybrid system is immediately ready to use.

Yes. The State of Charge (SoC) is given in precent and the voltage of the hybrid system (LE300 + lead-acid battery) will be shown.

For all brands of the Erwin Hymer Group, a SoC Display from Votronic is available. It can be ordered through the authorized dealers.

For all other applications a SoC Display will be available very soon.

The Display can be retrofitted. Bluetooth is not supported.

The LE300 can be bought at all of our official partners.

Here you can see a list of our partners.

You can use every lead-charger (Lichtmaschine, Solar, Landstrom). There is no special adjustment needed, the LE300 is using the same charging technique as a lead-acid battery.

The LE300 should cover at least your average daily consumption.

For example: If you have an average daily consumption of 0,5 kWh, we recommend two LE300 modules.

Li batteries can be discharged 100% without any harm to the batteries, however BOS systems have a default setting of 80% to get best out of the Lithium batteries.

The average ambient temperature for best performance is between 150 – 300 C and for warranty claims, the temperature should never fall below -100 C or exceed 450 C

Still have some questions?

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Sailboat Windzang

The passionate sailor Peter Reinmann extended his lead acid energy storage of his 9.30 meter long sailing catamaran with two BOS LiFePO4 Lithium modules. Peter is thus able to operate all the on-board electronics such as navigation, radio, light, refrigerator and gas heating. Because there was no room under the bench seat for a larger supply battery, a LE300 hybrid system was the perfect solution without loosing too much space. Now he is able to enjoy longer trips on the water without returning for recharge. A freedom that he no longer wants to miss.

Read More >

Hymer Cooperation

BOS Lithium Extension Batteries
are the main component of the new innovative hybrid storage battery for Hymer caravans. Hymer AG is one of the largest manufacturer of motorhomes and caravans in Europe. The HYMER-smart-battery-system will
offer more freedom of energy
integrated battery heating,

Read More >


Podcast: GELADEN with Fabian Weber

Podcast: GELADEN with Fabian Weber BOS AG welcomes the podcast team of GELADEN in our headquarter in Neu-Ulm, Germany. GELADEN is a podcast about batteries, created and spoken by Patrick von Rosen and Daniel Messling. In the newest episode, published on 2th november is about stationary storage with the COO of BOS AG, Fabian Weber.

Read More >


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