FAQ - Green Cubes Technology | Lithium-ion Power Systems Manufacturer

FAQ

Green Cubes Tech. Frequently Asked Questions

GENERAL INFORMATION
Q1.What is material is in the Green Cubes SafeFlex Battery ?
A1.

A Green Cubes’ SafeFlex battery pack is made using large format prismatic lithium-ion cells. The cells are constrained against shock and vibration in a steel enclosure. Battery interconnections are made with flexible busbars and high strand cabling.

TEMPERATURE PERFORMANCE
Q1.At what temperatures can I charge and discharge a Green Cubes’ SafeFlex Battery ?
A1.

Packs should only be charged from 0°C to 45°C (32°F to 113°F) and discharged from -20 °C to 55° C ( -4°F to 131 °F).

Q2.What are the effects of temperature on capacity and operation for both high 55 °C (131 F°) and low temperatures 0 °C and -20 °C (32 °F and -4°F)?
A2.

The supported discharge temperature range is -20 °C to 55 °C (-4 °F to 131 °F) and supported charge range is 0 °C to 45 °C (32 °F & 131 °F). At 55 °C (131 °F) the available capacity is 100%, at 0° C (32 °F) there is 75% available capacity, and at -20 °C (-4 °F) there is 41% available capacity. Constant operation at 55 °C (131 °F) will reduce the battery cycle lifetime by >20%.

Q3.Is the temperature range of -20 °C to 55 °C (-4 °F to 131 °F) the operating internal temperature of the pack or the ambient temperature?
A3.

This is the internal temperature. There are temperature sensors inside the pack which monitor the operating temperature. If the temperature range is exceeded, the pack will automatically shut off until the pack is allowed to cool/heat to within operational parameters.

CHARGING INFORMATION
Q1.Can Green Cubes’ SafeFlex batteries be opportunity charged?
A1.

Yes, Green Cubes’ batteries can be plugged in at any state of charge with absolutely no negative effects. In fact, opportunity charging can actually increase the lifetime amp-hour output of the battery. The battery pack does need periodic balancing and should be plugged in overnight or over the weekend once per week.

Q2.What happens when the pack runs out of charge?
A2.

Once the battery reaches 2-3% SOC red LED will flash notifying the operator that the battery is about to go dead. We recommend plugging the pack in as soon as the initial buzzer sounds to prolong the life of the battery. If the pack is not plugged in and left sitting in an uncharged state, it is possible the lithium-ion cells will be permanently damaged and no longer function which will void the packs’ warranty.

Q3.Do I need to disconnect the Green Cubes’ SafeFlex battery from the truck to charge it?
A3.

Green Cubes’ SafeFlex batteries include drive away protection which does not allow the user to use the truck while charging. The battery does not need to be disconnected from the truck when charging.

Q4.Is it OK to leave the Green Cubes SafeFlex battery plugged in?
A4.

Yes, the Battery Management System (BMS) monitors charging so the battery will never overcharge. Green Cubes recommends leaving the charger plugged in when not in use.

Q5.Can you overcharge or over discharge the packs?
A5.

Green Cubes’ SafeFlex Battery Management System (BMS) monitors charging so that the pack cannot be overcharged or over discharged. The only risk is if someone fully discharges the battery pack and then does not plug it in. In this case, because of the small parasitic draw from the electronics, it is possible to completely kill the pack. Therefore, we recommend the packs remain plugged in whenever not in use for more than a few days. There is no harm in leaving the packs plugged in, but great harm if they are left discharged for extended periods of time.

Note: Allowing the battery to over discharge due to extended use or storage after the low SOC alarm goes off will result in an “over discharge” condition and the battery will no longer charge. Failure to properly maintain the battery will void the battery’s warranty. We recommend plugging the pack in as soon as the initial buzzer sounds to prolong the life of the battery. If the pack is not plugged in and left sitting in an uncharged state, it is possible the lithium-ion cells will be permanently damaged and no longer function which will void the packs’ warranty.

Q6.Can you overcharge or over discharge the packs?
A6.

Green Cubes’ SafeFlex Battery Management System (BMS) monitors charging so that the pack cannot be overcharged or over discharged. The only risk is if someone fully discharges the battery pack and then does not plug it in. In this case, because of the small parasitic draw from the electronics, it is possible to completely kill the pack. Therefore, we recommend the packs remain plugged in whenever not in use for more than a few days. There is no harm in leaving the packs plugged in, but great harm if they are left discharged for extended periods of time.

Note: Allowing the battery to over discharge due to extended use or storage after the low SOC alarm goes off will results in an “over discharge” condition and the battery will no longer charge. Failure to properly maintain the battery will void the battery’s warranty. We recommend plugging the pack in as soon as the initial buzzer sounds to prolong the life of the battery. If the pack is not plugged in and left sitting in an uncharged state, it is possible the lithium-ion cells will be permanently damaged and no longer function which will void the packs’ warranty.

Q7.What type of charger and charging profile is used in the Green Cubes” SafeFlex battery?
A7.

Batteries with on-board charger have a high frequency BMS controlled device. It will charge at constant current until the desired pack voltage is reached. Once the voltage is reached, the charger will hold a constant voltage to finish charging and balancing.

Q8.Can a lead acid charger be used to charge the Green Cubes SafeFlex battery?
A8.

Green Cubes’ SafeFlex batteries require a higher charging voltage than lead acid batteries. It is recommended to use a Green Cubes approved charger to charge the battery. Charging with a non-approved charge will void the battery’s warranty. Contact Green Cubes for more information on approved chargers.

Q9.Is the charger CEC (California Energy Commission) approved/rated?
A9.

Yes. Green Cubes chargers are CEC compliant.

CELL CHEMISTRY INFORMATION
Q1.What types of lithium-ion chemistries are available, and why do we use LiFePO4?
A1.

There are several different chemistries available. Green Cubes uses LiFePO4 due to its long cycle life, low cost of ownership, thermal stability, and high-power output. Below is a chart which provides some information on alternative lithium-ion chemistries.

Specificatio ns Li-cobalt LiCoO2 (LCO)   Li-phosphate LiFePO4 (LFP) LiNiMnCoO2 (NMC)
Voltage 3.60V 3.30V 3.60/3.70V
Charge Limit 4.20V 3.60V 4.20V
Cycle Life 500 2,000 500 – 1000


Operating Temperatu re Average Good Good
Specific Energy 150–190Wh

/kg

90–120Wh/kg 140-180Wh/kg
Loading 1C 35C continuous 10C
Safety Average Very Safe Safer than Li- Cobalt
Thermal Runway 150°C (302°F) 270°C (518°F) 210°C (410°F)

 

Q2.What “wears out” in lithium-ion batteries?
A2.

As lithium iron phosphate cells cycle, the charge is carried between the anode and cathode using lithium-ions. As the pack cycles a very small percentage of the mobile lithium-ions are caught in irreversible side reactions. This reduces the amount of charge transfer possible between the electrodes.

In lead acid this is somewhat analogous to sulfation, where the sulfur becomes locked in stable lead sulfite crystals and can no longer intercalate into the lead plates. Sulfation is worse however as it occurs during use and during storage, the crystals can grow and crack the plates, and block electrolyte access to the plates.

Q3.What is the electrolyte in these batteries?
A3.

Green Cubes’ SafeFlex lithium-ion batteries use an electrolytic salt dissolved in organic solvents.

Q4.What is the specific gravity of Green Cubes’ lithium-ion batteries?
A4.

Specific gravity is not relevant for lithium-ion batteries. Generally, specific gravity is used to measure the density of lead acid electrolyte against water. Lithium-ion batteries are sealed and maintenance free, so there is no way to measure the electrolyte and no water is used.

Q5.What are the positive and negative active materials?
A5.

The cathode (positive electrode) is lithium iron phosphate with a copper charge collector, and the anode (negative electrode) is graphite with intercalated metallic lithium, and an aluminum charge collector.

Q6.What does intercalate mean?
A6.

Intercalation is the insertion of lithium ions into the anode and cathode material.

Q7.What are the chemical reactions occurring within a Green Cubes’ SafeFlex lithium-ion battery?
A7.

When the battery charges, the lithium ions are in the carbon/graphite anode, and when discharging the lithium ions move to the cathode. The chemical reactions are as follows:

  • Charge : LixC6 = 6C + xLi + xe
  • Discharge :Li(1-x)FePO4 + xLi+ xe = LiFePO4
Q8.Does the lithium-ion battery pack have a positive and negative grid like lead acid batteries?
A8.

Lead acid uses a lead plate, and a lead dioxide paste that must be supported by a structural grid as their anode and cathode. Green Cubes’ Safe Flex lithium-ion batteries have an anode and cathode, but no grid is used as there is no lead dioxide paste.

SHIPPING AND RECYCLING
Q1.What do I need to know to ship a Green Cubes’ SafeFlex battery ?
A1.

Similar to lead acid, there are packaging instructions which must be followed when shipping. A Lithium SAFEFlex battery must be shipped in accordance with UN3480, Hazard Class 9, packaging group II, instruction 965. If the pack is shipped in equipment, use packaging instructions 967.  If you need further assistance, please contact your Green Cubes representative.

Q2.What do you do with the batteries at the end of their life? Is there a recycling program?
A2.

Recycling methods are currently being developed, with reports of 60% recyclability at the cell level. Lithium-ion batteries are the future of energy storage, and recycling efficiencies are predicted to climb to >90% as the markets scale and additional recycling methods are developed.

Also note, because lithium-ion batteries have a much longer life-time vs. lead acid, there will be dramatically fewer batteries subject to recycling over time. If you require more detailed information regarding recycling, please contact your Green Cubes representative.

MAINTENANCE AND WATERING
Q1.Do the packs require watering?
A1.

No, lithium-ion batteries do not require watering. They are completely sealed and produce no gas when charging. In addition, the electrolyte is made of organic solvents, so water should not be used.

Q2.Do Green Cubes’ SafeFlex batteries require periodic maintenance?
A2.

No, but an annual inspection is recommended by an authorized dealer to ensure maximum battery health and life.

SAFETY INFORMATION
Q1.Are lithium-ion batteries safe?
A1.

There are several factors responsible for the remarkable safety of Green Cubes SafeFlex lithium-ion batteries.

  • The selection of battery chemistry is important. There are several lithium-ion chemistries to choose from, and each has unique properties. Green Cubes frequently has chosen lithium iron phosphate (LiFePO4) for several reasons. Most importantly LiFePO4 is chemically stable and has the highest thermal runaway temperature of any lithium-ion chemistry at 270 °C (518F). The news stories of cell phone and laptop batteries catching fire were a cobalt based chemistry that is less chemically stable. These batteries are also in a small cylindrical cell format.
  • The lithium-ion cells used are in the form of prismatic cell technology versus cylindrical cell. The prismatic cells contain >20Ah versus the 2.5Ah in cylindrical, meaning Green Cubes’ SafeFlex batteries have up to 10 times fewer power connections. In addition, the cells are connected with flexible busbars, meaning they are extremely vibration resistant.
  • The use of Large Format Cells means there are far fewer cell taps and temperature sensors. This system is less complex and inherently safer.
  • The BMS monitors the cell temperature and current and shuts the system down if it detects anything which may cause harm to the battery. This is to maintain battery performance and expected lifetime.
Q2.What happens if the pack is breached, what leaks out and is it dangerous?
A2.

The lithium-ion cells are first encased in hard plastic, and then an industrial 10-gauge powder coated steel case. If a user punctures through all these materials and exposes the lithium-ion cell electrodes and electrolyte, be cautious when handling. The electrolyte consists of organic solvents (EC, PC, DEC) and a dissolved electrolytic salt (LiPF6). They are skin and eye irritants, and fumes can cause mucus membrane irritation.

The solvents are flammable so do not expose to an open flame. Use rubber gloves, eye protection, ventilation and positive pressure breathing protection when removing the damaged battery and electrolyte. In addition, LiPF6 is hydrophilic and reacts with water releasing hydrogen fluoride, a corrosive flammable gas. If a fire does occur, use a CO2 or chemical fire extinguisher.

Q3.Will the batteries catch fire?
A3.

Green Cubes uses lithium iron phosphate (LFP) in its products as it is a very stable chemistry.  The ignition temperature is over 500F, much higher than other chemistries such as lithium cobalt at 149C (300F). The chemical stability also provides long cycle lifetimes (2000 at 80% DOD). In addition, there are safety measures built into the pack which prevent overcharging and rapid discharging. Finally, the battery case is made of high-grade steel, protecting the cells from damage, and containing them should a cell breach occur.

All these protections mean that under normal usage there is no danger of a fire. The dangers of spills and explosive gas buildup from lead acid batteries are much more common than a Lithium SafeFlex battery catching fire

Customer Ratings and Reviews

Green Cubes is a great company, great engineers, great product. That’s been kind of my number one go to [lithium] battery.

President, Industrial Power Company

The thing I like about Green Cubes is that they have other lines of business outside of material handling batteries, they have been in the lithium world for a long time. I can trust they will likely stay in business

VP, Industrial Battery Company

Green Cubes [differentiates] on its capability to custom design for things like the hardware, the firmware, and inverters. They also have economies of scale because they make battery systems for things like forklifts.

VP, Powered Cart OEM

I am doing some work with them right now. We’re learning their products, and looking at demos. They have good people. They seem like they know the technology well – they say they’re a technology company. I like that they’ve been in the lithium business a long time. I can trust they will likely stay in business.

Sales Manager, Industrial Battery Company

Green Cubes Technology would be my go-to for lithium applications.

Branch Manager, OEM

I’ve told my friends at Green Cubes, I don’t plan on going anywhere. I believe in loyalty.

President, Industrial Power Company