Atnen ENERpower 14S desktop charger (58.8V) for Li-ion batteries 52V (50.4V-51.8V) | output 2A | 120W
General Information
With the right charger you extend the lifespan of your battery. Cheap chargers do not charge batteries to CC / CV and usually not up to 4.2V or 58.8V. At first, your battery will never be really full, and it will also shorten the life of the battery by up to 30%. Saving on a charger, is saving in the wrong place!
Highlights / Technical Details
Cable length: approx. 100 cm
Output: 2A
Plug: DCJ / XLR-3-Pins / XT-60 / XT-90
Input: 90 - 264 V AC
Manufacturer: Atnen
Brand: ENERpower
Model: LBC030480201
CC/CV with end-of-charge voltage of 58.8V +/- 0.2V
Suitable for 14S Li-ion battery packs (50.4V - 51.8V)
Compatibility i.a.
This charger is compatible with all ENERpower batteries 14S (50.4V - 51.8V), which have a round plug (DC). You can also use this charger with other Li-Ion batteries that have a rated voltage of 50.4V or 51.8V.
Atnen ENERpower 14S desktop charger (58.8V) for Li-ion batteries 52V (50.4V-51.8V) | output 2A | 120W
General Information
With the right charger you extend the lifespan of your battery. Cheap chargers do not charge batteries to CC / CV and usually not up to 4.2V or 58.8V. At first, your battery will never be really full, and it will also shorten the life of the battery by up to 30%. Saving on a charger, is saving in the wrong place!
Highlights / Technical Details
Cable length: approx. 100 cm
Output: 2A
Plug: DCJ / XLR-3-Pins / XT-60 / XT-90
Input: 90 - 264 V AC
Manufacturer: Atnen
Brand: ENERpower
Model: LBC030480201
CC/CV with end-of-charge voltage of 58.8V +/- 0.2V
Suitable for 14S Li-ion battery packs (50.4V - 51.8V)
Compatibility i.a.
This charger is compatible with all ENERpower batteries 14S (50.4V - 51.8V), which have a round plug (DC). You can also use this charger with other Li-Ion batteries that have a rated voltage of 50.4V or 51.8V.
Atnen power by ENERpower 14S desktop charger (58.8V) for Li-ion batteries 52V (50.4V-51.8V) | output 3A | 180W
General Information
With the right charger you extend the lifespan of your battery. Cheap chargers do not charge batteries to CC / CV and usually not up to 4.2V or 58.8V. At first, your battery will never be really full, and it will also shorten the life of the battery by up to 30%. Saving on a charger, is saving in the wrong place!
Highlights / Technical Details
Cable length: approx. 100 cm
Output: 3A
Plug: XLR-3-Pins / XT-60 / XT-90 / Open-wires
Input: 100 - 240 V AC
Manufacturer: Atnen
Brand: ENERpower
Model: LBC015588030
CC/CV with end-of-charge voltage of 58.8V +/- 0.2V
Suitable for 14S Li-ion battery packs (50.4V - 51.8V)
Compatibility i.a.
This charger is compatible with all ENERpower batteries 14S (50.4V - 51.8V), which have a round plug (DC). You can also use this charger with other Li-Ion batteries that have a rated voltage of 50.4V or 51.8V.
Atnen power by ENERpower 14S desktop charger (58.8V) for Li-ion batteries 52V (50.4V-51.8V) | output 3A | 180W
General Information
With the right charger you extend the lifespan of your battery. Cheap chargers do not charge batteries to CC / CV and usually not up to 4.2V or 58.8V. At first, your battery will never be really full, and it will also shorten the life of the battery by up to 30%. Saving on a charger, is saving in the wrong place!
Highlights / Technical Details
Cable length: approx. 100 cm
Output: 3A
Plug: XLR-3-Pins / XT-60 / XT-90 / Open-wires
Input: 100 - 240 V AC
Manufacturer: Atnen
Brand: ENERpower
Model: LBC015588030
CC/CV with end-of-charge voltage of 58.8V +/- 0.2V
Suitable for 14S Li-ion battery packs (50.4V - 51.8V)
Compatibility i.a.
This charger is compatible with all ENERpower batteries 14S (50.4V - 51.8V), which have a round plug (DC). You can also use this charger with other Li-Ion batteries that have a rated voltage of 50.4V or 51.8V.
ENERpower Bike-Frame-Battery Li-Ion Hailong Reention Jaffa DIY 52V (14S) from own manufacturing 16Ah (830Wh)
For motors from 250 Watts and up to 1050 Watts
This 52V battery in the Hailong Reention Jaffa case, which we manufacture, can be mounted on the frame or on the luggage carrier of the bike. The batteries are manufactured in cell holders made of plastic. Charging is made possible with a DC circular connector (5.5 mm / 2.5 mm), discharging via the bracket (separable from the battery) with XT90, XT60, or Anderson (surcharge) connector. This case can hold up to 70 18650 battery cells. With a BMS that can withstand 20A-22A continuous load, this battery is suitable for motors with up to 1050 watts of power, working in 52V (14S) systems.The battery holder is very small and therefore we implement the Fuse inside the Discharge Cable
The On/Off button enable the user the turn the battery on and off as an additional feature.
Highlights
High quality assembly – Made in Germany
Assembly Just-In-Time
BMS with an integrated passive balancer
BMS with protection against overcharge, over-discharge, deep-discharge (temperature monitoring)
Direct from the manufacturer
Rechargeable - After 500 charging cycles, still maintaines about 70% of the original capacity
No memory effect – charge your battery whenever you want
Environmentally friendly in accordance with EU Directive 2002/95 / EC (RoHS)
Technical Details
Li-Ion-cell: LG Chem INR18650-MH1
Voltage (nominal): 52V (50.4V-51.8V)
Capacity: 16Ah
Power: 830Wh
Configuration: 14S5P
Internal resistance: < 75 mOhm
Charge Voltage: 58.8V
End-of-discharge Voltage: 42V
BMS continueous discharge current: 22A
BMS 10 Min. discharge current: 25A
BMS 5 Sec. discharge current: 30A
Safety fuse: 30A
Weight: approx. 3.95 Kg.
Charging: Zenith IP67 3-Pins
Discharging: Cable with fuse 30A with XT-60
ENERpower Bike-Frame-Battery Li-Ion Hailong Reention Jaffa DIY 52V (14S) from own manufacturing 17.2Ah (890Wh)
For motors from 250 Watts and up to 1050 Watts
This 52V battery in the Hailong Reention Jaffa case, which we manufacture, can be mounted on the frame or on the luggage carrier of the bike. The batteries are manufactured in cell holders made of plastic. Charging is made possible with a DC circular connector (5.5 mm / 2.5 mm), discharging via the bracket (separable from the battery) with XT90, XT60, or Anderson (surcharge) connector. This case can hold up to 70 18650 battery cells. With a BMS that can withstand 20A-22A continuous load, this battery is suitable for motors with up to 1050 watts of power, working in 52V (14S) systems.The battery holder is very small and therefore we implement the Fuse inside the Discharge Cable
The On/Off button enable the user the turn the battery on and off as an additional feature.
Highlights
High quality assembly – Made in Germany
Assembly Just-In-Time
BMS with an integrated passive balancer
BMS with protection against overcharge, over-discharge, deep-discharge (temperature monitoring)
Direct from the manufacturer
Rechargeable - After 500 charging cycles, still maintaines about 70% of the original capacity
No memory effect – charge your battery whenever you want
Environmentally friendly in accordance with EU Directive 2002/95 / EC (RoHS)
Technical Details
Li-Ion-cell: LG Chem INR18650-MJ1
Voltage (nominal): 52V (50.4V-51.8V)
Capacity: 17.2Ah
Power: 890Wh
Configuration: 14S5P
Internal resistance: < 75 mOhm
Charge Voltage: 58.8V
End-of-discharge Voltage: 42V
BMS continueous discharge current: 22A
BMS 10 Min. discharge current: 25A
BMS 5 Sec. discharge current: 30A
Safety fuse: 30A
Weight: approx. 3.95 Kg.
Charging: Zenith IP67 3-Pins
Discharging: Cable with fuse 30A with XT-60
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 48V | output 1.5A | power 85W | for SoFlow SO myTIER DC
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 1.5A / 85 Watt
Plug: DC
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 54.6V + 0.2V
Charges Li-ion batteries of 48V (13S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <1.8A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (54.6V) for Batteries 48V | output 1.5A | power 85W | for SoFlow SO4 PRO 2ND GEN DC
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 1.5A / 85 Watt
Plug: DC
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 54.6V + 0.2V
Charges Li-ion batteries of 48V (13S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <1.8A
Short-circuit protection: 3.5W
Reversed-polarity protection
Ultra-fast charger CCCV 420W (42V / 10A charging current) for 36V eBike batteries, powered by Enerpower.
Highligths
Overcurrent, short circuit and reverse polarity protection
Safety standards: EN60335
Efficiency: 87%
CCCV - Constant current & Constant voltage - the right way to charge Li-ion batteries
420W output power (up to 10A + 10% output current)
Simple and safe handling (plug-and-play)
High quality and long life
LED indicator (red / green)
Technical Details
Input
Voltage: AC 100-264V
Input Current: 7A (Max.)
Output
42V DC 10A
Safety Measures
Over current protection: < 10.3A
Short circuit protection: constant
Reverse polarity protection
Conformity
IEC 61558-1:2005
IEC 61558-:2005/AMD1:2009
IEC 61558-2-16:2009
IEC 61558-2-16:2009/AMD1:2013
Dimensions:
200 x 91x 63 mm
Gewicht:
1.3 Kg.
fast charger CCCV 550W (54.6V / 10A charging current) for 36V eBike batteries, powered by Enerpower.
Highligths
Overcurrent, short circuit and reverse polarity protection
Safety standards: EN60335
Efficiency: 87%
CCCV - Constant current & Constant voltage - the right way to charge Li-ion batteries
550W output power (up to 10A + 10% output current)
Simple and safe handling (plug-and-play)
High quality and long life
LED indicator (red / green)
Technical Details
Input
Voltage: AC 100-264V
Input Current: 7A (Max.)
Output
54.6V DC 10A
Safety Measures
Over current protection: < 10.3A
Short circuit protection: constant
Reverse polarity protection
Conformity
IEC 61558-1:2005
IEC 61558-:2005/AMD1:2009
IEC 61558-2-16:2009
IEC 61558-2-16:2009/AMD1:2013
Dimensions:
200 x 91x 63 mm
Gewicht:
1.3 Kg.
ENERpower charger 7S (29.4V) for Li-Ion batteries 24V | output current 20A (600W) | connector: XT-60, XT-90, Anderson
With the right charger, you extend the life of your battery. Cheap chargers do not charge batteries to CC / CV and usually not up to 4.2V or 29.4V. At the same time, your battery will never really get full, and you can shorten the battery life by up to 30%. Saving on a charger, is saving in the wrong place!
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 20A – fast and powerful
Connector: XT-60, XT-90, Anderson
Input: 100 – 240V AC
Manufacturer: Electrony
Brand: ENERpower
Model: XT80V294A200
CC/CV with End-of-Charge voltage of 29.4V + 0.2V
Charges Li-ion batteries of 24V
Energy: 600 WattWeight: ca. 2.5 Kg.Sizes: 222 x 120 x 70 mmWith Fan
Safety
Protection against over-current: < 23.4A
Protection against short circuit: 3.5W
Protection against reversed polarity
Compatibility (i.a.)
This charger is compatible with 24V Li-Ion batteries
ENERpower charger 7S (29.4V) for eBike batteries 24V | output current 5A (150W) | connector: XLR-3
With the right charger, you extend the life of your battery. Cheap chargers do not charge batteries to CC / CV and usually not up to 4.2V or 29.4V. At the same time, your battery will never really get full, and you can shorten the battery life by up to 30%. Saving on a charger, is saving in the wrong place!
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 5A – fast and powerful
Connector: XLR-3 (3 pins)
Input: 100 – 240V AC
Manufacturer: Atnen
Brand: ENERpower
Model: LBC015294050
CC/CV with End-of-Charge voltage of 29.4V + 0.2V
Charges Li-ion batteries of 24V
GS – certified safety standards according to § 21 ProdSG
Efficiency: ca. 88%
Energy: 150 Watt
Safety
Protection against over-current: < 6.4A
Protection against short circuit: 3.5W
Protection against reversed polarity
Compatibility (i.a.)
This charger is compatible with 24V Li-Ion batteries
ENERpower charger 7S (29.4V) for eBike batteries 24V | output current 5A (150W) | connector: XLR-3
With the right charger, you extend the life of your battery. Cheap chargers do not charge batteries to CC / CV and usually not up to 4.2V or 29.4V. At the same time, your battery will never really get full, and you can shorten the battery life by up to 30%. Saving on a charger, is saving in the wrong place!
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 5A – fast and powerful
Connector: XLR-3 (3 pins)
Input: 100 – 240V AC
Manufacturer: Atnen
Brand: ENERpower
Model: LBC015294050
CC/CV with End-of-Charge voltage of 29.4V + 0.2V
Charges Li-ion batteries of 24V
GS – certified safety standards according to § 21 ProdSG
Efficiency: ca. 88%
Energy: 150 Watt
Safety
Protection against over-current: < 6.4A
Protection against short circuit: 3.5W
Protection against reversed polarity
Compatibility (i.a.)
This charger is compatible with 24V Li-Ion batteries
Atnen fast charger CCCV 85W (42V / 2A charging current) for 36V eBike batteries, powered by Enerpower.
Atnen Chargers are known for being very efficient and very safe. They are smaller and lighter in comparison to competitors products and are certified in many countries (UL, cUL, PSE, KCC, GS, CCC)
Highligths
Overcurrent, short circuit and reverse polarity protection
Safety standards: UL1310, EN60335
GS (tested safety) and UL approved
Protection class: IP20
CCCV - Constant current & Constant voltage - the right way to charge Li-ion batteries
85W output power (up to 3A + 10% output current)
Simple and safe handling (plug-and-play)
High quality and long life
LED indicator (red / green)
Technical Details
Input
Voltage: AC 100-264V
Input Current: 2A (Max.)
Output
42V DC 2A
Safety Measures
Over current protection: < 2.3A
Short circuit protection: constant
Reverse polarity protection
Conformity
IEC 61558-1:2005
IEC 61558-:2005/AMD1:2009
IEC 61558-2-16:2009
IEC 61558-2-16:2009/AMD1:2013
Compatible with (i.a.)
Ansmann
Mifa
Rex
Prophete
Aldi
Lidl
Atnen fast charger CCCV 85W (42V / 2A charging current) for 36V eBike batteries, powered by Enerpower.
Atnen Chargers are known for being very efficient and very safe. They are smaller and lighter in comparison to competitors products and are certified in many countries (UL, cUL, PSE, KCC, GS, CCC)
Highligths
Overcurrent, short circuit and reverse polarity protection
Safety standards: UL1310, EN60335
GS (tested safety) and UL approved
Protection class: IP20
CCCV - Constant current & Constant voltage - the right way to charge Li-ion batteries
85W output power (up to 3A + 10% output current)
Simple and safe handling (plug-and-play)
High quality and long life
LED indicator (red / green)
Technical Details
Input
Voltage: AC 100-264V
Input Current: 2A (Max.)
Output
42V DC 2A
Safety Measures
Over current protection: < 2.3A
Short circuit protection: constant
Reverse polarity protection
Conformity
IEC 61558-1:2005
IEC 61558-:2005/AMD1:2009
IEC 61558-2-16:2009
IEC 61558-2-16:2009/AMD1:2013
Compatible with (i.a.)
Ansmann
Mifa
Rex
Prophete
Aldi
Lidl
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Doc Green ESA 1900 eScooter
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Segway Ninebot KickScooter Air T15 / D18 / D28
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Segway Ninebot KickScooter D38 / E22 / E25
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Segway Ninebot KickScooter E45/ ES1 / ES2
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Segway Ninebot KickScooter ES4 / F20D / F25E
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Segway Ninebot KickScooter F30D / F30E / F40D / F40
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Segway Ninebot KickScooter Max G30 / G30LD / G30LE
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Segway Ninebot Minilite
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection
Fuyuang 12V-24V Li-Ion-Charger (42V) for Batteries 36V | output 2A | power 85W | for Odys Alpha X10, X3 Pro eScooter
With this 85W, 12V-24V DC charger from Fuyuang (Enerpower) you can easily charge your ebike battery using the 12V cigarettes lighter in your car or caravan/mobile home.
Highlights / Technical Details
Cable length: ca. 100 cm
Output: 2A / 85 Watt
Plug: DC+
Input: 12V-24V DC 10A (Max.)
Manufacturer: Fuyuang
Brand: Enerpower
CC/CV with End-of-Charge voltage of 42V + 0.2V
Charges Li-ion batteries of 36V (10S)
Energy: 85W
Dimensions without cables: 15 x 6 x 4 cm
Weight: about 465 Gramm
Safety
Over-current protection: <2.3A
Short-circuit protection: 3.5W
Reversed-polarity protection