7 Questions To Ask Before You Buy An LFP Battery For Your Home
Almost every lithium battery sold for home solar in India is assembled here, not manufactured here. The cells inside are imported, and the label on the outside tells you remarkably little about them.
A typical battery label carries five things: the brand name, the capacity, the voltage, a warranty in years, and a country of origin. None of those five tell you whether the battery is safe, or whether the warranty means anything. The things that would tell you are the things nobody prints.
Which company manufactured the cells inside this battery?
The cell is the battery. Everything else — the casing, the busbars, the label — is packaging. India currently has only a handful of companies producing lithium cells at scale, and most of that output goes to phones, gadgets and EVs rather than home storage. So the honest answer will usually name a foreign cell maker. That is not the problem. The problem is a vendor who will not name one at all, because the manufacturer’s name is the single thread that lets you verify anything else — the datasheet, the cycle rating, the grade.
A good answer
Names the specific cell manufacturer, and offers to show you the cell datasheet.
You can then look that company up yourself.A weak answer
“It’s an A-grade cell.” “It’s imported.” “Best quality cell hai.”
Grade is not a manufacturer. Imported is not a manufacturer.What is the Depth of Discharge, and what is the usable capacity?
Depth of Discharge (DoD) is how much of the rated capacity you are actually allowed to use before the battery cuts off. A 5 kWh battery at 80% DoD gives you 4 kWh, not 5. You are billed for the number on the label but you live with the number after DoD. Get the usable figure in kWh, in writing, and size your system against that.
A good answer
A specific percentage, printed on the spec sheet, plus the resulting usable kWh.
Higher DoD means more of what you paid for is actually available.A weak answer
“You can use the full capacity.” Or a percentage quoted verbally that appears nowhere on paper.
No lithium battery is designed to be run to absolute zero.What is the warranty in cycles — not in years?
A battery does not age by calendar. It ages by use. One cycle is one full charge plus one full discharge, and a warranty written only as “5 years” tells you nothing about how much use those five years are allowed to contain. Ask for the cycle count and compare it against how you will actually run the system — a battery cycled daily reaches its cycle limit far sooner than one cycled twice a week. Then ask which limit expires first, the years or the cycles.
A good answer
A stated cycle count alongside the term in years, and clarity on which one ends the warranty.
Both numbers, and the condition attached to them.A weak answer
“Five year warranty hai.” Full stop.
Years alone are the easiest warranty in the world to write.What capacity is guaranteed at the end of the warranty period?
This is the question almost nobody asks, and it is the one that decides what you actually own in year five. Every lithium battery degrades. A battery that holds only 60% of its original capacity at the end of its term is still “working” — so no warranty claim applies — but it is doing substantially less than half the job you bought it for. The guarantee you want is a percentage floor, written into the warranty document.
A good answer
A guaranteed minimum retained capacity at end of term, stated as a percentage in the warranty document.
This is what makes the warranty measurable.A weak answer
“Some degradation is normal.” No figure offered, nothing in the document.
Without a floor, there is no threshold you could ever claim against.Who made the BMS, and does it log data?
The Battery Management System keeps every cell in balance, watches temperature, and cuts the battery off before a fault becomes a fire. It is the single most safety-critical component in the box. A generic BMS bought off the shelf and dropped into a pack — with no tuning for the temperatures an Indian installation actually sees — is one of the more common paths to a battery failure. Data logging matters just as much: without logs, a warranty dispute in year four comes down to your word against theirs.
A good answer
Names the BMS maker, and can show you the monitoring interface with per-cell voltages, temperature and an event log.
Ask to see it running before you buy.A weak answer
“It’s our own BMS” — with nothing to demonstrate and no logging to show.
If it cannot be shown, assume it cannot be checked later either.Will this battery work with another brand’s inverter, and on which protocol?
A hybrid inverter and a battery have to talk to each other, and they do it over a communication protocol — commonly CAN or RS485. If your battery only speaks to one brand’s inverter, you are locked in for the life of the system. When that inverter fails in year three, you are not replacing an inverter; you are replacing the whole pairing. Ask for the protocol by name and for a written compatibility list.
A good answer
Names the protocol, and provides a list of inverter brands and models the battery is tested against.
Open protocol plus a real compatibility list means you keep your options.A weak answer
“It only works with our inverter.” Or a proprietary protocol with no list.
Lock-in is a commercial decision being sold to you as a technical one.Where are the serial number and batch number recorded?
This is the least exciting question here and it is the one that decides whether a warranty is real. A warranty claim needs traceability: which unit, from which production batch, sold on which date, installed where. If none of that was recorded anywhere except a sticker on a box that gets thrown away, then in year four there is nothing to claim against. Get the serial and batch number onto your invoice, and confirm the manufacturer holds the same record at their end.
A good answer
Serial and batch numbers written on your invoice, and registered in the manufacturer’s own system against your installation.
Two records, one of which you keep.A weak answer
A sticker on the carton and nothing on paper.
An untraceable unit is an unclaimable one.The checklist, in one screen
Screenshot this and take it into the conversation.
- Which company manufactured the cells?
- What is the Depth of Discharge, and the usable kWh?
- What is the warranty in cycles, and which limit expires first?
- What capacity is guaranteed at the end of the warranty?
- Who made the BMS, and can I see the data logs?
- Which inverter brands and protocols is it compatible with?
- Where are the serial and batch numbers recorded?
