Recommendations on category G1

Test procedure for category G1:

NFC58-510 plus PPER (Combined test procedure, ageing ratio 1:1, ref. [3])
See Testprocedures.
As long as no results are available for this combined test procedure, select the battery that has the best results (longest life time) for the two separate test procedures.

Selection of battery and charge controller for category G1:

• It is essential to use a charge controller that protects the battery from deep discharging. The control algorithm of the charge controller can be based on a SoC calculation or on voltage settings. The recommended end-of-discharge-settings of the controller are the following:
  • Low voltage Disconnect, for discharge current I10: 1.80 to 1.85 V/cell
  • Low voltage Disconnect, for discharge current 10% of I10: 1.95 to 2.0 V/cell
• It is essential to use a charge controller that protects the battery from overcharging. The recommended end-of-charge-settings of the controller depend on the type of battery and the category of battery usage. The recommended batteries are given below, in order of preference, together with the recommended voltage settings for the charge controllers at charging.

  Recommended battery in order of preference	Controller settings (in V/cell at 25°C)	maint. months
  VRLA, tubular plate	Charge: 2.4 V equalisation: 2.5 V ( 10h / month)	6
  Flooded, tubular plate with electrolyte mixing	Charge: 2.35 V equalisation: 2.45 V (10h / month)	6
  Flooded, tubular plate without electrolyte mixing	Charge: 2.4 V equalisation: 2.55 V (8 h / 2 weeks)	6

• If the battery will be operated outside the temperature range of 20-30 degrees it is preferable to use a charge controller that compensates for the effect of the battery temperature. It will typically adjust settings to ensure that charge and discharge cycles are modified based on temperature and voltage or state of charge. A separate battery temperature sensor should be used.
• It is preferable to use a charge controller with separate voltage sense terminals.

More specific recommendations for category G1:

The main battery issues of category G1 are the high energy throughput and the low charge factor. For such systems, the main improvement is the increase of the charge factor. To achieve this the following actions should be considered.

1. Apply the recommended values for the setpoints of the charge controller in the table above.
2. Use a charge controller with a low self-consumption and with a high efficiency.
3. Reduce the load (e.g. by replacing appliances by more efficient ones).
4. Increase the electricity generation of the renewable energy sources.
5. Use (or increase the use of) a back-up generator. The most efficient way is to use the back-up generator starting early in the morning and, once the threshold voltage of the battery is reached and the power output of the back-up generator is beginning to fall, continue charging the battery by means of the renewable energy source.
6. Replace the battery with a battery of lower capacity if this is possible. Due to the low charge factor, the capacity of the battery is likely to decrease quickly and therefore a battery with a lower nominal capacity but proper charge factor is likely to offer a better long-term security of supply.
7. In the case of a low ambient temperature (high value of the low environmental temperature factor) the battery should be thermal protected to avoid electrolyte freeze that may happen due to the deep discharge conditions, possibly long time at a low SoC and the electrolyte stratification.