BOS Logo
BOS Balance of Storage Systems AG Logo weiss

Hymer - Smart Battery System


Installation & User Manual

Product No.: 12000101

Table of Contents

General Information

The HY-Tec lithium battery 50 is a high-quality power storage system from the HYMER Smart Battery System series. The HY-Tec lithium battery 50 consists of six individual LE300 lithium extension battery modules (LE300). The HY-Tec lithium battery 50 is a scalable solution for increasing the capacity and performance of lead-acid batteries and improving the efficiency and lifespan of your overall system.

The HY-Tec lithium battery 50 is connected in parallel to the lead-acid battery. Multiple HY-TEC lithium batteries 50 can be connected in series. The lithium batteries will handle most of the charging cycles, while the lead-acid battery functions as low-cost back-up storage. The lead acid battery is charged first, and the lithium batteries will then absorb the excess energy. During operation, the lithium batteries will discharge first, which significantly prolongs the lifespan of the lead-acid battery.

The lithium batteries are able to detect the voltage of the lead-acid battery. The integrated discharge management function ensures that loads are primarily supplied from the deep-cycle lithium batteries. Large loads are supplied in parallel by the lead-acid battery and the lithium batteries, which reduces the load on both battery types.

Overview of components

The HYMER Smart Battery System consists of the following individual components:
• HY-Tec lithium battery 50
– consisting of 2x LE300 lithium extension battery modules
• 1x connection cable set – for connecting the lead-acid battery
(length: approximately 2.10 m, with M6 ring terminal)
• 1x communication cable for parallel operation
• 1x replacement fuses (20 A)
• 1x replacement fuse (30 A)

Safety instructions

  • Please read and understand the whole user manual before installation and usage of the LE300 Lithium Extension Battery.
  • Only connect to 12 VDC batteries of the following types:
  • Lead storage batteries with liquid electrolytes
  • Sealed lead acid batteries – GEL or AGM
  • Use the device only in combination with a lead acid battery and a lead acid charge controller, do NOT connect loads or power sources directly to the lead acid battery nor to the LE300 device.
  • Lead acid batteries can generate explosive gases during operation. Never smoke, allow flames or sparks near the battery. Make sure to keep sufficient ventilation around the battery and read the lead acid battery user manual.
  • Do NOT use with nickel cadmium batteries, nickel metal hydride batteries or other battery types.
  • Do NOT mix up the + (plus) and – (minus) poles of the battery.
  • Do NOT connect anything to a damaged battery. It could heat up, catch fire or explode.
  • Do NOT open the battery pack. Danger of short-circuiting. Opening the LE300 device voids any and all warranty claims.
  • Best operating temperature is between 15 and 20 °C. Higher temperatures shorten the lifespan of the batteries. Do NOT place device in direct sunlight!
  • Protect the LE300 against heat (e.g. prolonged sun exposure) and fire and from water. Do NOT store or operate the LE300 near hot or flammable objects.
  • Install this device step by step as written in this manual for best results.
  • After installation, the device needs to be fully charged.
  • Do NOT charge the device over an extended period, if the device is unused.
  • After prolonged storage period, it may be necessary to charge and discharge the device numerous times to achieve the full performance capability.
  • Follow all safety precautions during installation of device & handling batteries.
  • Improper handling of batteries may introduce a risk of battery explosion.
  • Keep batteries away from children & animals.
  • During handling of batteries no smoking or exposure to naked light & fire.
  • Wear eye protection during installation process.
  • When working with a battery and LE300 remove all personal metal items like watches, rings, necklaces and bracelets. Metal items in contact with the battery terminals might cause a short circuit with a very high electric current, which may heat up and melt nearby objects and cause severe burns.
  • Keep the LE300 not being used away from paper clips, coins, keys, nails, screws or other small metal objects, that can make a connection from one terminal to another. Shorting the battery-pack terminals together may cause burns or a fire. For short-circuiting damage caused in this manner, any and all warranty claims shall be invalid.
  • Use electrically insulated tools for connecting cables.
  • The mounting and the electrical connection may only be carried out by trained specialists.
  • Use only properly functioning test equipment with this device.
  • Internal voltage of device may be higher than the rated level, take care to avoid being zapped during installation.
  • Keep this document in a safe place for the entire service life of the device. Pass the document on to subsequent owners and operators of the device.
  • Incorrect operation can damage system components.
  • The device must not be connected to a lead acid battery if it has a damaged casing.
  • Factory labels and markings must never be altered, removed or rendered unreadable.
  • This device contains sensitive electronics, so take care during installation and use.
  • Consider all relevant official safety instructions during transportation of the device. Safety instructions might vary depending on the mode of transport and on local country regulations.
  • Check the recycling information at the end of the user manual for disposal of device.

Application Scope

  • The primary application of the LE300 is the stationary storage of renewable energy in the area of solar energy.
  • This device is for residential, recreational & small commercial operations.
  • This device is for operation with 12 V lead acid batteries only. A lead acid charge controller is needed for correct operation.
  • The device is not permitted to be mounted in outdoors, underside, engine compartment or exposed areas of interior spaces (e.g. side pockets in the trunk, outer wet chamber, spare wheel recess).
  • Failure to follow this precaution can cause damage to this device and the energy source to which it is connected.
  • Consult authorized supplier if device is to be connected in nonstandard configuration.
  • Sizing of lead acid battery needs to fit to the overall system design. For long lifetime lead acid battery must frequently be charged to 100%.
  • If sizing of the system is not done within the specification warranty becomes void.
  • The battery connection in the KFZ range need to be chosen < 3 m.
  • Failure to comply with correct product usage or neglecting the user manual, the warranty and guarantee becomes void.

Guidelines and certifications

The LE300 Lithium Extension Battery is designed and verified according to the following standards/guidelines:

  • CE
  • UN38.3
  • IEC 62619: 2017
  • IEC 62133: 2012
  • (EMC) Directive 2014/30/EU
    (electromagnetic compatibility)
  • DIN EN 61000-3-2: 2015
  • DIN EN 61000-3-3: 2014
  • DIN EN 61000-6-1: 2007
  • DIN EN 61000-6-3: 2011

Furthermore, the LE300 Lithium Extension Battery was successfully subjected to a temperature cycling test as well as a shock and vibration test. All tests were carried out in accordance with LV124 at TÜV Rheinland. The LE300 Lithium Extension Battery is approved for use in motor vehicles and bears the ECE test mark E1*10R05/01*9017*00.

Technical specifications

System voltage

12 VDC

Norminal voltage

12.8 VDC

Voltage range

11 -15 VDC

Battery packs used in LE300

IFpR/26/65 [8p/4s] E/-20NA/95 LiFePO4 rechargeable battery

Nominal lithium capacity

28 Ah / 358 Wh

Usable lithium capacity

90% (25.2 Ah / 322 Wh)

Numbers of cycles at room temperature

>3000 complete cycles

Recommended lead acid capacity for each LE300 (not included)

70 – 125 Ah @ 12 VDC

Recommended lead acid capacity for each LE300 (not included)

1/3 in solar home applications. Values vary depending on needed autonomy and on application.

Continuous charging current

Max. 12.5 A between 5 and 40°C, at higher and lower temperatures current is limited.

Battery efficiency

> 90%

Housing dimensions

175 x 229 x 67 cm


3.4 kg

Connection terminals

RAST 5/mini module 4 pin/communication
interface/external display

Recommended wire size

1.5 – 4 mm²

Ambient temp. (operation & warehousing)

-20 – 50 °C ambient temperature with
maximum battery life at 15 – 25 °C.
Warehousing temperature 10 – 30 °C.

Low and high temperature protection,
heating, charging & discharging

Temp. sensor prevents lithium battery charge under -5°C or above 55°C cell temp. Charging starts once cell temp. is higher than -5°C. Device has an integrated heating that is active between -20°C and 10°C cell temp. Discharge possible between -20°C and 60°C cell temp. At cell temp. below -20°C and over 60°C system is running in pure lead acid mode for higher battery lifetime.

Lithium cell balancing

Battery management inclusive balancer

Protection features

Overcurrent, overvoltage, short circuit, deep discharge, wrong polarity protection.

Operation mode/compatible
external batteries

Works in combination with any 12 V lead acid battery & lead acid charge controller.

Connection possibilities

Packs can be connected in parallel with each other (see exemplary parallel combination in the table below).

Max. parallel LE300s

In standard version, a maximum of 24
LE300 can be connected only in parallel, higher quantities possible after consulting BOS partner.


parallel combination


Qt. in parallel


Total nominal voltage

12.8 VDC

Total lithium capacity

112 Ah / 1.43 kWh

Continuous charging current to LEs

Max. 50 A

Continuous discharging current from LEs

Max. 50 A

Recommended lead acid capacity (not included)

4 – 12 kWh


  1. State-of-charge-trend-display and torchlight
  2. Push button
  3. Mounting shape for standard lead acid mounting clamp
  4. Holes for mechanical parallel mounting / mounting on mounting plate (optional)
  5. Cable connector plugs
  6. Cable strain relief connectors

System Functions



The lead acid battery is charged with higher priority. After the lead acid battery is charged 80% the LE300 starts being charged in parallel. However, it still leaves sufficient energy for the lead acid battery to be properly fully charged. The charging current is limited to about 12.5 A per device, for instance 4x LE300 can be charged with up to 50 A.


At the beginning of each discharge phase, the LE300 will be discharged first (given that the LE300 has not been empty). Depending on the load, the LE300
is doing all the work until the LE300 is almost completely discharged. Once the LE is discharged the lead acid battery will be discharged (if load continuous). Therefore, in charging & discharging phases the LE300 is supporting the lead acid battery. The current is limited to about 12.5 A per device, for instance 4x LE300 can thus together support the lead acid battery with up to 50 A. Currents higher than the nominal rated currents of the LEs are supported by both, the LEs and the lead acid batteries, resulting in smaller C-rates for both batteries.


Due to the intelligent battery management, the LE300 is fully protected against overload and deep discharge as well as overcurrent, short circuits, wrong polarity and too high or too low temperatures. Under cold conditions (<10 °C cell temperature) the integrated heater heats up the LE300 to operating temperature to avoid damage to the cells during the charging phase. At cell temperatures below -20 °C no discharge of the device is possible. At cell temperatures below -5 °C no charge is possible. Once the integrated heater has warmed up the LE300 and the thresholds of -5 °C for charging
and -20 °C for discharging are passed, the LE300 starts charging/discharging. Full charging and discharging power is available between 5 °C and 40 °C. At cell temperatures lower than 5 °C and higher than 40 °C the charging and discharging currents are limited.

The device is short circuit protected, in case of short circuit the device will show an error code (see details under chapter 7 Display & operation). The device is wrong polarity protected, in case of connection with wrong polarity the device will show an error code (see details under chapter 7 Display & operation).

Sleep mode

An internal sleep mode protects against a complete discharge of the Li-cells. When idle, under normal conditions the LE300 goes into a standby/sleep mode. Every 128 seconds the device will be automatically waked up to check, if LE300 is needed for charging/discharging. If one of the Li-cells falls under deep discharge, caused by self-discharge, the LE300 goes into a deep sleep mode. In this mode, the LE300 can only be woken up by pressing the push button or by recharging the device (this is checked every four mins automatically). After wake-up, a charging phase is possible. If one of the Li-cells is critically deep discharged, the LE300 system shuts down completely into a safety mode to protect from potential dangers that could occur when recharging depleted lithium cells. The LE300 cannot be woken up anymore. Neither charging nor discharging is possible anymore. In this case, please contact your local BOS dealer for support.


Please read and understand our general information before starting the installation.

Technical installation

In general, the LE300 can be installed in any mounting direction. Recommended mounting directions are mounting in upright position using the standard lead acid battery clamps and mounting flat on biggest area using direct mounting to a mounting plate with screws/bolts. See graphics below for details.

Electronical installation

The LE300 Lithium Extension Battery is connected in parallel to the lead acid battery. Please note that a standard lead acid battery charge controller is needed. No special additional charge controller is needed for the LE300. It is important to choose the right size of connection cable, depending on the maximum currents. Several sets of connecting cables might be required. Make sure that wiring is done according to DIN VDE 0298-4.

The picture above is a basic visualization of the system connection, details on the electrical connection are explained in the following.

 20 A
Optional to
next LE
Optional to
next LE
Optional to

Simply connect the LE300 system directly in parallel to the lead acid battery at the RAST 5 (code 00E) power connector (1). Therefore, use the supplied plug connector, fix cables to it, plug it to the back of the LE300 at the power connector

1 and mount the other side of the cables to your lead acid battery. Pay attention to right polarity and proper cable connection!

Check if the 20 A fuse is inserted at

2. If fuse is missing, insert the supplied spare part 20 A fuse.

In case of parallel connection of several LEs, make sure that LE enclosures are mounted firmly together. It is recommended to use a threaded bolt and nuts to tighten LEs with each other (optional mechanical parallel mounting kit). It is recommended to connect all LE300 with each other through RS485 communication

3 and 4. LE300s would also work in parallel mode without the RS485 communication, however one common state-of-charge-trend-signal couldn’t be generated anymore for the whole system. Maximum number of LEs in parallel configuration is 24 LEs as standard version, please get in touch with your BOS dealer if more LEs in parallel are needed.

5 Optional signal outlet for display connection. 0 – 10 V state-of-charge-trendsignal to be connected to displays with 0 – 10 V signal input. It is recommended to use the following plug with cables at the signal outlet: Mini-Fit Jr.™ TPA Cable Assembly 45135 (plug not included). Optionally a LCD state-of-charge-trend-display is available.

5 Display out graphic



6 Tighten the installed cables with a cable tie to the strain relief connectors to avoid damages to the electronics from moving cables.


Once mechanical and electrical connection is done according to chapter 5, the LE300 will automatically start working and supporting the lead acid battery system. Please push the pushbutton of LEs to check the status of the products (see details in chapter 7). It is recommended to fully charge the system once LEs were connected. A full system charge is needed in order to give accurate information on the state of charge of the system. For devices which are stored over a longer period of time, several charging cycles might be necessary. This is done to balance each lithium-cells and to show an accurate state-of-charge-trend-display.

Display & Operation

The HY-Tec lithium battery 50 can be visualised by means of an external LCD display (optional).

The state-of-charge monitor displays the state of charge of the entire battery system, i.e. that of both
the lead-acid and the lithium batteries. The characteristics of the lead-acid battery affect the state-ofcharge
monitor. The state-of-charge monitor is most accurate at room temperature after a period of
inactivity of approximately 5 hours.


The device is optimised for energy-saving operation. A complete shutdown is therefore neither necessary nor possible.

Display screens

Use the left and middle button to switch between the display screens.

Remaining battery capacity:

State-of-charge (SoC) monitor in %.

Battery voltage:

Battery voltage monitor in volts (V). The bar graph on the left continues to indicate the remaining battery capacity. Caution: A battery voltage below 12.8 V (at light loads) indicates that the lead-acid battery has partially discharged.

Accessing the menu

The menu is divided into two sections. The first section includes all settings that can be adapted to your daily needs, such as the brightness of the lighting. The second section contains the basic settings of the SoC 100% signal. To prevent unintentional changes to the basic settings, access to the second menu section requires deliberate action. To access the menu, press and hold the right button for about 3 seconds. When the menu is active, “Set” will flash at the upper edge of the display. Use the left and middle buttons to adjust the settings. Press the right button briefly to move to the next menu item and automatically save the changes. The settings will be retained even in the event of a power failure.

First section of the menu:

Switching output
Switch-off threshold
(Not being used)


Second section of the menu:

The second section of the menu can only be accessed from the last menu item of the first section (backlight brightness) by pressing and holding the right button (for about 3 seconds) until the following screen appears.
SoC 100% signal This voltage corresponds to an SoC of 100%. The default value for the HY-Tec lithium battery 50 is set to 9.3 V.

Troubleshooting and FAQ

The fuses and connecting cables of the HY-Tec lithium battery 50 need to be checked if the
display does not show more than 80% in packages 1 and 2 or 90% in package 3, despite being
fully charged at room temperature (15°C to 25°C). If the problem persists, contact the nearest
HYMER service centre.


The device is basically maintenance-free. Cable connections should be checked frequently. Clean the device from dust when necessary with a dry cloth. Avoid any contact with water or other liquids. The lifespan of the LE300 can be prolonged when being properly maintained and especially when being operated and stored at the right temperatures. With increasing age however, the LE300 capacity will diminish even when properly maintained. If the operating period significantly reduces after charging, the LE300 is probably worn out and must be replaced.

Storage & winter storage protection

If used properly, the HY-Tec lithium battery 50 has a lifespan of over ten years. The system has to be fully charged at least once every six months. Please note that the batteries may be damaged by deep discharge if not charged regularly. If the HY-Tec lithium battery 50 has not been used for a longer period of time, it must first be fully charged. The EBL then has to be switched off in order to disconnect all loads from the battery system. The battery status should be checked at least every six months by switching on the EBL. The fuses between the HY-Tec lithium battery 50 and the lead-acid battery must not be removed, otherwise the winter storage protection will not be operational, which will damage the lead-acid battery. Note: If the HY-Tec lithium battery 50 is stored in state of discharge for a longer period of time, the device may be damaged despite the low level of self-discharge, thereby greatly reducing its capacity.

If possible, the HY-Tec lithium battery 50 should be stored in a dry, well-ventilated place. Do not expose it to moisture or water. The operating temperature range is -20°C to 50°C. During winter storage, the battery can be stored at temperatures as low as -20°C for a limited period. Make sure not to exceed the maximum operating temperature. Keep away from direct sunlight. During prolonged storage, the ambient temperature should be between 10°C and 25°C and must not exceed 30°C. Relative humidity above 95 per cent and below 40 should be avoided over longer periods of time, as should condensation.


The LE300 is UN38.3 certified, nonetheless it is subject to the Dangerous Goods Legislation requirements. Private users can transport undamaged LE300 by road without further requirements.
When being transported by commercial users or third parties (e.g. air transport or forwarding agency), special requirements on packaging and labelling must be observed (e.g. ADR regulations). If necessary, an expert for hazardous materials can be consulted when preparing the item for shipping.
Dispatch LE300 only when the housing is undamaged. Tape or mask off open contacts and pack up the LE300 in such a manner that it cannot move around
in the packaging. Inform your parcel service that the package contains dangerous goods. Please also observe the possibility of more detailed national regulations. In case of questions concerning transport of the LE300, please refer to an authorized BOS dealer. The BOS dealers can also provide suitable transport packaging.

Warranty & Legal Notes



The LE300 Lithium Extension Battery come with a two-year warranty on the product including the integrated lithium battery starting from the date of purchase. There is no warranty granted on other system components from other manufacturers that are used together with the LE300 Lithium Extension Battery. In case of problems, comments or a warranty claim or the need for spare parts please contact the local dealer or BOS AG for support.


Exclusion of liability

The manufacturer can neither monitor the compliance with this manual nor the conditions and methods during the installation, operation, usage and maintenance of the device. Improper installation of the device may result in damage to property and, as a result, to bodily injury. Therefore, the manufacturer assumes no responsibility and liability for loss, damage or costs which result from or are in any way related to incorrect installation,
improper operation, incorrect execution of installation work and incorrect usage and maintenance. Similarly, we assume no responsibility for patent right or other right infringements of third parties caused by usage of this device. The manufacturer reserves the right to make changes to the product, technical
data or installation and operating instructions without prior notice.

Declaration of conformity

The LE300 Lithium Extension Battery comply with all applicable provisions of relevant directives and regulations and are in conformity with the relevant standards. The full declaration of conformity is found for download at

Recycling Information

Recycling of the integrated lithium battery is handled in Germany by GRS Service GmbH.

Do not dispose in waste bin, but recycle electronics, batteries and packaging materials according to local regulations. Tape or mask off the contact surfaces of the LE300 terminals with adhesive tape before disposing of the device. For more information, please contact your BOS dealer or BOS Balance of Storage Systems AG.

Only for EC countries:
According to the European Guideline 2012/19/EU, electrical devices/tools that are no longer usable, and according to the European Guideline 2006/66/EC, defective or used battery packs/batteries, must be collected separately and disposed of in an environmentally correct manner.

Contact Hymer Zentrale

Hymer GmbH & Co. KG
Holzstraße 19
D-88339 Bad Waldsee/GERMANY
E-Mail: [email protected]
Telefon: +49 7524 999-0
Telefax: +49 7524 999-220