Frequently Asked Questions
Short Answer -
Parallel: No Limit.
Series: Four, up to 48Vdc
Series and Parallel: Series string up to 48V - parallel strings unlimited.
In-Depth Explanation -
Parallel – There is no limit to the number of batteries that can be connected in parallel provided the wiring and connections are properly sized to handle the resulting power. See wire gauge calculator. Our BMS will balance each battery in the bank, continually share energy to maintain pack unity Voltage.
Total battery capacity is added, Voltage remains the same.
Example: 2 x 12.8V 100Ah batteries connected in parallel yield a 12.8V 200Ah bank.
Series – Up to four batteries can be connected in series or until a maximum of 48Vdc is reached. Example: 4 x 12V = 48V battery bank or 2 x 24V = 48V battery bank.
Total Battery Voltage is added, capacity remains the same.
Example: 2 x 12.8V 100Ah batteries connected in series yields a 25.6V 100Ah bank.
Extra battery balancing (balancers or equalizers) may be required to ensure that each battery pack stays at equal Voltage with the other batteries in the Series connected string. This depends mainly on the type of charging system being used.
If 2 x 12.8V batteries connected in series to create a 25.6V bank, there are three ways of charging.
- A single 25.6V charger - connected across both batteries. Show diagram.
- A 2 bank 12.8V charger – connected to each battery. Show diagram.
Balancers not necessary. The batteries will align once charged full. Each battery is essentially charged separately while remaining connected to the system.
- Single 12.8V charger- connected to each battery individually. Show diagram.
Balancers not necessary
Batteries must be disconnected from each other and charged separately.
Series and Parallel:
Combination of Series and Parallel connected batteries. The same rules apply as above.
Example: Connect 2 x 12.8V 100Ah batteries in series to effectively produce a 25.6V 100Ah bank (or string). Now connect 2 of these 25.6V 100Ah banks (or strings) in parallel – you have created a 25.6V 200Ah bank. Series/ parallel connected bank.
Discharging: LFP batteries can be discharged at Temperatures down to -20 Celsius (-4 F) but will temporarily lose usable capacity once the internal temperature of the battery falls below 0 Celsius (32 F) and will continue to discharge more quickly as the temperature drops. See graph.
Charging: LFP batteries should not be charged below a Temperature of 0 Celsius. We recommend charging at above 5 Celsius. Internal Temperature.
Current must be reduced to.
0.1C max from -7⁰C to 3⁰C
0.05C max from -15⁰C to -7⁰C
Storage: Storage is allowed in cold temperatures, to -20 Celsius, although not strongly recommended. It is important the proper SOC is maintained to avoid damage. Storing at improper state of charge levels has increased detrimental effects at temperatures below 0Celsius. The battery cells can freeze below -25C, and although not necessarily detrimental to battery health, precautions must be taken to slowly thaw and then charge to full before using.
70% State of Charge @ 13.2V - in a cool dry location.
Disconnect from all loads and charging sources. They exhibit very low self-discharge characteristics and can be stored for up to 1 year without any additional charge.
We recommend checking State of Charge (SOC) after the first month to ensure no unexpected discharge is taking place. It is detrimental to leave them in a fully charged or fully discharged state for any extended period of time. Roughly speaking – storage SOC can safely range from 40% – 80%.
All of our batteries come stocked with oversized management systems capable of handling usage above and beyond standard ratings. The BMS provides internal cell balancing, thermal cut off, charge and discharge Voltage limit cut out, charge and discharge limit Current cut out, and short circuit protection. This is just the baseline! Safety - Reliability - Performance are front and center in our units.
All batteries over 100Ah boast Low-Temperature charge protection with options for in-battery heating, direct monitoring and communications, and adjustable setpoints to suit your project.
LFP batteries should be isolated from other battery chemistries. They have different charging characteristics and will not charge or discharge at the same rates. Current transfer between the different battery types can be elevated, continuous, and damaging.
You will need either a Voltage Regulator or DC-DC Converter Charger with the proper charging profile. Charging directly from an alternator, with no regulation, can damage the alternator and LFP batteries quickly. LFP batteries can take in high a amount of power when charging, enough to overburden the alternator and cause failures. While the output voltage of the alternator may be correct for LFP charging, the profile and current tapering needed to properly charge is not inherent.
A proper regulator or DC-DC converter charger will limit current flow from the alternator, protecting it and the batteries, as well as provide safe and effective charging capability.
These batteries are generally not meant for engine cranking but are best used inconsistent deep cycling applications - this is one of their main cost benefits. Engine cranking requires very high short power bursts to turn over the engine. LFP Aside from significant size and weight savings, the cost of using LFP as a starting battery is seldom realized. Additionally, LFP batteries should not be charged directly from an Alternator.
We are currently developing a Crank battery!
Constant Current – Constant Voltage (CC-CV) charge profile.
A CC-CV charging profile is required to safely top up LFP batteries.
Most existing AGM or GEL battery chargers possess the proper charging profile LFP batteries.
Maintenance, reconditioning and equalization modes should be avoided, they generally included high Voltage and Current pulsating spikes that are unnecessary for LFP battery chemistry and can be damaging with prolonged use.
When using standard AGM chargers with maintenance, equalization, or reconditioning stages, it is recommended the charger is disconnected or turned off before these stages activate. They will only activate once the battery is fully charged or after an extended period of time. Disconnect chargers with these phases once the battery is fully charged.
Floating profiles or Floating stages are acceptable, often beneficial in solar and constant battery cycling applications. 13.2V – 13.6Vdc
Note: LFP batteries do not need to remain fully charged and prefer to rest in a partially charged state. They are designed to cycle. The best practice is to charge before use. Leave resting at a 40% - 80% SOC.
Recommended charge settings.
Charge Current = Bulk Current = Constant Current Phase (CC) = 0.1C - 0.5C (C= Capacity Rate)
Capacity Rate Example: For a 12.8V 100Ah battery – total capacity is 100Ah
1.0C (100% of total battery capacity) = 100A
0.5C (50% of total battery capacity) = 50A
0.2C (20% of total battery capacity) = 20A
Charge Voltage – Absorption Voltage = 14V – 14.4V
Float Voltage – 13.2V - 13.6V
Equalization Voltage or Equalization Time = 0 = OFF