How to look after a lithium battery

Most lithium solar batteries today are lithium iron phosphate, often written LiFePO4 or LFP. It is a stable chemistry that tolerates daily deep use, and UTL’s lithium batteries use it.

No water, no acid, no cleaning

A lithium battery is sealed. There is nothing to top up and nothing to spill, and it gives off no gas in normal use, so it does not need the dedicated ventilation a tubular battery does. A cool, airy spot is still best. A battery management system, or BMS, inside the pack watches every cell and cuts the battery off if something goes out of range.

Set the inverter for lithium

This matters more than anything else. A lithium battery charges to different voltages from a tubular one, and an inverter left on its tubular settings will charge it wrongly. Before a lithium battery goes in, check that the inverter supports lithium and is set for it. UTL makes inverters for this, such as its Gamma+ 3 kVA, which supports lithium batteries.

Do not connect a lithium battery alongside tubular ones, or mix old and new lithium packs. They charge differently and the mismatch works against both.

Keep it out of the heat

Heat shortens a lithium battery’s life as it does any battery’s. Keep it out of direct sun and away from the inverter’s exhaust or a hot tin roof. A cool, dry, shaded spot is best.

Use more of it, without worry

A lithium battery is built to be used deeply. When we size a system we plan on using 80% of a lithium battery’s capacity each cycle, against half for a tubular one, which is why a smaller lithium bank can do the same job. UTL lists 3,000 to 3,500 cycles at 80% depth of discharge for its LiFePO4 batteries.

You also do not need to keep it full. A lithium battery is content sitting part-charged, so there is no need to run the generator or buy grid power just to top it up.

If it will sit unused

For a farmhouse or a shop closed for weeks, leave the battery partly charged rather than full or empty, switch the system off as the manual says, and check it every so often. A battery left completely flat for a long time can be hard to recover.

Older habits to drop

Tubular batteries benefit from an occasional full equalising charge and from never being left part-charged. Neither applies to lithium, and an equalising charge can harm it. If you are moving from tubular to lithium, forget both. For the tubular side, see how to look after a tubular battery.

To choose between them in the first place, read tubular or lithium for solar, and size the battery for what you want to run in the hybrid solar calculator.