Your battery bank has to do more than store kilowatt-hours.
Doug Mycko helps Big Island off-grid customers size lithium battery storage, match batteries to inverters, plan replacements for older battery banks and troubleshoot charging, communication and capacity problems.
Capacity is only part of the battery decision.
A battery bank must store enough energy for the home, but it also has to deliver enough power when large loads start, accept the available charging current and work correctly with the inverter and charging equipment.
Usable capacity
Battery sizing should be based on usable energy, overnight consumption, reserve needs and the amount of autonomy expected during poor solar weather.
Power & surge
A battery may have plenty of stored energy and still be unable to support a demanding motor or other high-current load. Continuous and short-duration discharge capability matter.
Inverter compatibility
Battery voltage, current capability, communication protocol and manufacturer support should be considered before pairing lithium batteries with an inverter.
Charging capability
Solar charge controllers, inverter chargers and generators must be able to charge the battery bank within appropriate voltage and current limits.
Battery communication
Closed-loop lithium systems can exchange state-of-charge and operating-limit information with compatible inverters. Communication problems can affect system behavior.
Expansion planning
Adding batteries changes available storage and discharge capability, but the solar array and charging equipment still need enough capacity to refill the larger bank.
Compare usable energy, not just amp-hours.
When replacing flooded lead-acid, AGM or another older battery bank with lithium, the nameplate amp-hour numbers do not tell the whole story.
- Nominal battery-bank voltage
- Total stored kilowatt-hours
- Realistically usable depth of discharge
- Continuous discharge capability
- Startup and surge requirements
- Available solar charging power
- Inverter and charge-controller settings
The goal is to replace the useful capability of the old bank while taking advantage of the different operating characteristics of lithium.
Not every shutdown means the battery is empty.
A lithium battery can shut down because of current limits, low or high voltage, temperature, communication problems or a protection event. If the system loses power unexpectedly, the cause should be identified before simply adding more battery capacity.
Troubleshoot the SystemMatch storage, power and charging.
Measure energy needs
Estimate how many kilowatt-hours the home uses overnight and through a normal 24-hour period.
Check peak loads
Identify pumps, air conditioners, compressors, appliances and other loads that can create high startup or operating current.
Match the inverter
Verify voltage, current capability and supported battery communication before selecting the battery configuration.
Verify recharge power
Make sure the PV array and generator charging system can reasonably restore the energy removed from the batteries.
SolarMan works with modern off-grid battery systems.
Battery selection depends on the inverter, load profile, required storage, discharge capability, serviceability and the overall system design. SolarMan supplies and supports multiple battery platforms rather than treating every off-grid home as the same application.
The battery bank is one part of the off-grid system.
Tell Doug what battery bank and inverter you have.
For an existing system, have the exact inverter model, battery model and battery quantity available. For a new system, start with the major loads and expected daily energy use.