0
\$\begingroup\$

I already have a 12 V 7 Ah battery. Now I am planning to buy an inverter which is 700 VA. Can I use that battery with this inverter? Will it be safe?

Regarding load, I will only use 2 CFL/LED/Tube lights.

\$\endgroup\$
  • \$\begingroup\$ 84VAh battery with 700VA inverter. Inverter start current may be too high to start \$\endgroup\$ – Sunnyskyguy EE75 Apr 23 at 15:41
1
\$\begingroup\$

Unfortunately you haven't provided enough information to answer the question fully. What you need to know is the discharge current characteristics for the battery and the specifications for the inverter.

A 60W equivalent CFL is likely to be somewhere in the region of 15W. So, your load will be somewhere in the region of 30W.

If your inverter is rated for 700VA then you can think of it as being able to support a 700W load (for the real, and longer, answer search for volt-amps). Therefore the load on your inverter would be well within its capabilities at less than 10%. A smaller inverter might suit your needs better.

If this is a cheap Chinese square-wave inverter then the efficiency could be as poor as 50%.

So: 30W / 0.5 = 60W input to the inverter. Or: 60W / 12V = 5A

Usually even SLA batteries can support a 1C load (7A in your case for a 7AH battery), so you would be comfortably under that.

BUT, inverters can have significant inrush current. The start-up characteristics should be in the documentation for the inverter, you just need to check two things on the battery spec:

  1. That the battery can support this short-term spike in current without damage while the inverter starts up.
  2. That the terminal voltage will not fall below the under-voltage cutout for the inverter due to the battery's internal resistance.
\$\endgroup\$
  • \$\begingroup\$ I am using Exide ceil valve regulated lead acid battery. Unfortunately I couldn't able to find the datatsheet. In the battery, maximum initial current is mentioned as 1.4A \$\endgroup\$ – Antony Vimal Raj Apr 23 at 16:57
  • 1
    \$\begingroup\$ @AntonyVimalRaj - "In the battery, maximum initial current is mentioned as 1.4A" From my experience with several such batteries, that is likely to be the maximum initial charging current (especially if nearby text describes the float and cycling charge voltages) - not the battery's maximum discharge current. A 1.4A maximum discharge current from a 7Ah VRLA battery would be unexpectedly small, in my experience. However, the battery's datasheet (or equivalent information from the manufacturer) is the authoritative source of data about it. \$\endgroup\$ – SamGibson Apr 24 at 3:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.