Help. Giandel 1500 Watt Inverter won't start a Chest freezer?


New Member
Dec 6, 2022
I have a small system for dedicated critical loads:
I have a Giandel 1500 Watt Pure Sine Wave Inverter (model # PS-1500KAR), two 12.8V 100 AH Chins batteries, wired in parallel for a 200 AH capacity. Charging isn't a problem.

My current load on this inverter is less than 100 Watts. I have a couple of chest freezers that near the inverter in my garage and I tried to plug in one of them, and the system shut down. I have been monitoring the energy use of these freezers for about 6 month and on their worst days, the both pull a combined 125 watts on average. The highest peak load I have seen on the (again, both combined) is around 580 Watts, but for less than a minute. So my question is why did it shut down when plugging in only one freezer? Do I need to distribute the load between the 2 outlets on the inverter? I know compressors have surge loads, but surely 1600 watts (surge) can cover it? The batteries have a 100 A discharge rate from the BMS, and I think each battery is only seeing 1/2 the load. Thanks.
I suspect the startup surge is greater than that inverter can provide. It is probably an old chest freezer and not Energy Star rated. What you get with modern devices is typically an inverter driven compressor that has minimal startup surge and low operating Watts.
You can but a "Soft Starter". They are designed to reduce the surge cause when a motor is starting up. Of course there is no way to know in advance how much this will help, but in many cases they can cut the startup current to 33-50% of the normal value. It basically uses some electronics to slowly ramp the voltage up over 1-2 seconds. I gets the motor up and spinning before dumping full voltage unto it. I have one of these on a table saw. You can actually hear that it starts up more slowly.

Given these are fairly pricey, it is worth asking if your money is better spent by upgrading your inverter. It would be good if you could get a measurement of the startup current.

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Did it shutdown on overload or battery low voltage? High startup demands will cause voltage droop that can be exaggerated if there is insufficient sized cables from the batteries to the inverter. Or if the battery is at a low state of charge. Also how old is your chest freezer/ Is it a frost free type?
I think I found the problem. It's the BMS in the Chins batteries. They have a 100A max discharge rate. When pulling 1500 Watts (or more) for start up inrush current exceeds 117 Amps. I assumed that since the 2 batteries are in parallel, each would only see 1/2 the load, so I am probably pulling over 200 Amps for a fraction of a second. Such is the life of a 12 volt system. Thanks for you help everyone.
If you figure that 15A X 120V = 1800W and that an A-Typical standard generic fridge will pull at least that for a start surge (often even more for a second or so, if an older fridge) you are underpowered.

Yes, Batteries in Parallel will divide & share load & charge without issue. Your 2 batteries can deliver 200A without issue. I believe their BMS' are also capable of dealing with a momentary surge of up to 150A (remembering from Will's vid's)

12V @ 250A will give you 3000W which is pretty much the Max you can use 12V for, after that the costs of equipment etc make it unpractical and not as safe either.

You have three options:
1- Upgrade your inverter to a higher capacity Low Frequency unit (that can handle 3x surge)
2- Switch to 24V but that also requires an inverter change, batteries can be put in series for 24V.
3- Find a compatible Soft-Start unit for your fridge/freezer and AC System if you have one.
Steve_S pretty much covered your options. I had no problems with 3 freezers and a refrigerator on a Cotek 1500 watt inverter. It was a 24 volt model and used 4 ga wire to feed it. You need to determine if the shutdown is due to an overload on the output or low voltage on the input. You have the batteries in parallel, are the positive and negative lead diagonal from each other or both on the same battery?
Replace those useless lithium batteries with an automotive lead-acid starting battery 😁

You have the batteries in parallel, are the positive and negative lead diagonal from each other or both on the same battery?

As Brett indicates, imbalanced draw could be part of the issue.
Lithium can deliver very high current. Wish BMS could support starting surge, and also protect itself.