Inverter won't start

Hi there - I have recently built 3 18650 cell packs as a bit of an experiment. Each pack contains 40 cells, which have all been tested.
Each pack has been fully charged and connected in series to achieve the desired ~12V.

This weekend I purchased a pure sine wave600W inverter that was on special at Jaycar - the unit also included a charge controller. When I connected the inverter, an under-voltage alarm sounded and the inverter wouldn't start. I checked the specs of the input voltage -8 to15 VDC and measured the pack voltage at the terminals on the inverter which measured just under 12V.
No matter what I tried, I couldn't get the inverter to start.
Assuming the unit was faulty, I returned it (for a cheaper unit that didn't include the charge controller). This unit will also not start - it just sounds the under voltage alarm as per the previous unitand fails to start.

I'm at a loss here - the pack voltage is def in range -at the input terminals of the inverter it's measuring atjust under 12V.

Any ideas folks?

Did you measure the voltage on the terminals on the inverter during startup? Have you tried the battery pack with some load?
Can it be that the inverter pulls to much in beginning and then the battery sags to much and the low voltage alarm is triggered?

Please tell us more of those battery packs you bought? What type of cells? how are they tested? Capacity in total? Old or new?

Yep, I'm thinking the packs are sagging too low under startup, as well.

I have a few random inverters and none of them start much below 12V, did you test on another voltage source? 8V input may not mean 8V start...

An easy test : connect it to your battery car (only if the battery work well)
if the inverter start : it's working. so your 3S battery is not good enought.

cristof said:

An easy test : connect it to your battery car (only if the battery work well)
if the inverter start : it's working. so your 3S battery is not good enought.

Click to expand...

Another option is to add another group of cells to make a 4S pack - then only charge it up to 15 Volts. If that works try charging the pack up to 16V and testagain.

You may find that the inverters prefer to be running high voltages.

Cheers, Paul