Disappointed with new lithium battery

[pir8ped]

Hi,

I have a really tiny cabin. I have 2 X 260w panels on the roof which for the last 5 years have charged 2x 6v Trojan T105s. I have a 300w Victron inverter.

For the first couple of years, I just ran led lights, charged phones and laptops. Then I got an old fridge and added that to the system, a freebie from marketplace. Worked fine for three years, till a month ago.

Then the inverter started cutting out. Couldn't find enough power I guess to start the fridge compressor. It worked at night, but in the day, despite the input from the panels, it failed. I guessed the batteries were on their way out, not working so well when they get warm.

So I bought a Lanpwr 100ah lithium battery. Charged it up. Worked great for a few hours. Now I get the same shenanigans from the inverter, cutting out when the fridge tries to start the compressor.

I can see from the battery app that when the fridge runs it uses 30w. And now when it fails to start up, it's draws 500w for a few seconds till then inverter quits trying.

I thought the lithium battery would be capable of putting out more power than the lead acid batteries. And I'm surprised at the 500w draw from the fridge. (The fridge is a standard domestic Miele fridge).

Is the fridge too old? Do I need to buy a bigger inverter (I also have a cheap Lvyuan 600w inverter that didn't get the fridge going away all). How about some kind of soft start gadget?

I thought I was simply upgrading my battery and it would be so easy!

Thanks for reading.

 

[RCinFLA]

Refrig probably needs a new start capacitor or PTC thermistor that controls the start capacitor.

 

[Delmar]

Also monitor the fridge to see how often it starts. It takes a while for the high-pressure side to bleed down. Frequent starting will increase the compressor load.

 

[pir8ped]

Refrig probably needs a new start capacitor or PTC thermistor that controls the start capacitor.

Good call. Start relay shot. New one on order. Thanks!

 

[dopeassjackson]

And if that dosnt work I bet you need a bigger inverter.

 

[JanisD]

Will be curing similar problem with 800 VA inverter and 250 W dehumidifier soon.
At start the consumption spikes to 1,4 - 1,7 kW. Will ad soft start circuit to compressor motor - I'm 99.9% confident of success
In that case the relay, power resistor and small time delay circuit will be all that's needed.

 

[sun walker]

Love Totnes, beautiful oak giants down by the river.
I'm on my 3rd almost free fridge, the 1st I got for housing my batteries, the next 2 side by side, to repair, there's a lot of info online re repair, always the simple solution like "start capacitor or PTC thermistor" which it may be but sadly old fridges just lose their refrigerant gas, you can refill them with piercing valves & a doner fridge with the same gas, for a few $, using the outlet from the compressor to pump gas into the other fridge or buy gas from an auto shop. Not sure if your fridge is worth the effort. When they lose gas the compressor runs more & needs more energy, in time they can ice up & then just won't freeze anymore. But it may be a simple solution.

 

[Airman68]

The age of the fridge has a lot to do with it. Definitely higher inrush current on the old ones. Nowadays you can get a pretty nice new fridge for under $300 unless you want a full size one and they don't use that much power. I just have a 3.0 cu/ft mini at my cabin and I think it uses about 20ish watts running. On sale I think it was $99.

 

[RCinFLA]

Leaking refrigerant is not going to cause a hard start, just crappy cooling.

A start relay is better system than a PTC thermistor control.

PTC means Positive Temp Coefficient; resistance rises as it gets hotter). It is cheap for manufacturers but only works for small compressor motors.

Start relay is called a potential relay because relay's energizing coil depends on voltage (back EMF) developed across start/auxiliary winding of single phase AC motor. At initial startup, EMF voltage is low and relay remains as it sits in off state condition. The EMF begins to rise as motor spins up. EMF voltage from start/aux winding will increase by about a factor of 2x. When voltage reaches about 1.5x it causes relay coil to pull-in relay, disconnecting the normally closed contact to start capacitor. This removes start cap from circuit.

PTC thermistor starts out cold with low resistance in series with start cap to give the full effect of start cap phase shift to start/auxiliary winding to increase startup torque on motor. As the current flows, it heats up the PTC thermistor causing its resistance to increase reducing the phase shift and current to start winding of compressor.

Problem with PTC thermistor start cap control is it takes some amount of 'OFF' time to cool down. Normal refrigerator cycling operation provides this off time gap but if there is grid power glitches or you are messing with plugging in refrig multiple times while playing with an inverter it does not get the time to cool off the PTC thermistor so you effectively have little to no benefit of start capacitor startup torque boost. This lengthens the high current surge startup time, likely caving the inverter with too much overload time.

Compressor has a Klixon cutout breaker switch internal to compressor if compressor gets too hot. Problem is if you trip this it can take half to one hour before high mass steel compressor will cool down enough to reset thermal overload mechanical breaker.

 

[dopeassjackson]

Love Totnes, beautiful oak giants down by the river.
I'm on my 3rd almost free fridge, the 1st I got for housing my batteries, the next 2 side by side, to repair, there's a lot of info online re repair, always the simple solution like "start capacitor or PTC thermistor" which it may be but sadly old fridges just lose their refrigerant gas, you can refill them with piercing valves & a doner fridge with the same gas, for a few $, using the outlet from the compressor to pump gas into the other fridge or buy gas from an auto shop. Not sure if your fridge is worth the effort. When they lose gas the compressor runs more & needs more energy, in time they can ice up & then just won't freeze anymore. But it may be a simple solution.
View attachment 292823

I would not recommend doing this. There are refrigerants now that are propane based. At what point did house hold fridges use 134a? If your fixing house hold appliances that are useing r12 your more than likely fixing a 25ish year old appliance. Not really worth the effort when new/used ones are so cheap. Marketplace has been my go to for cheap "used" appliances, you have to be picky though.

 

[Skypower]

Everything that was said about the refrigerator and check your cable size/conmections

 

[Shawn Hayes]

Will ad soft start circuit to compressor motor - I'm 99.9% confident of success

What kind of soft start devices are available, and most importantly can it be used with a 1.5 hp 110v water pump? If so, possible help on how to wire it up?
I’ve looked at the “Soft Start Flex” made for HVAC units but it’s unclear how to wire up for a pump versus HVAC units…..even though they say it can be used that way…..

 

[JanisD]

Sorry, for me as DIY guy, it will be something simple similar to fig.6 here .
Be warned - don't try these, if You are not comfortable with working on live AC circuits. And it isn't preferable solution for 1.5 hp motor either.

On the bright side - simple question to Google "soft start for 1.5 hp 110 V AC motor" gives plenty of results starting with ebay or Ali... (use with caution) till something of reputable brands (for ex. this ). Take a look and I would suggest to ask some local suppliers of electric equipment.

 

[sun walker]

Hi,

I have a really tiny cabin. I have 2 X 260w panels on the roof which for the last 5 years have charged 2x 6v Trojan T105s. I have a 300w Victron inverter.

If your interested in considering other options, bearing in mind your system is small, see "Water heating with solar" on this site page 4,
there is a bit of discussion there re fridge.

 

[sun walker]

Compressor

You have a good understanding of refrigerators, would you mind answering a couple of questions?
I run a fridge directly from an inverter (no batteries), its works fine, but foggy mornings can delay the relay turn on, as the fridge compressor needs 1100w for its 1st start, after that its fine.
So can I make it easier for the compressor to start by either or both options?
- a soft start (230V To 12-20A Soft Start Switch Current Limiter)
- & or by connecting capacitors in parallel with the motor,(I have a pile of ~300w pump motors with starter capacitors I could use, I figure ~4 caps in parallel will delivery extra current on start).

 

[RCinFLA]

Refrigerators have various versions of circuitry for starting capacitor activation.

A popular method is a positive temp coefficient thermistor that acts like a switch to reduce the effective capacitance of starter capacitor after startup. PTC thermistor is in series with start capacitor. PTC is low resistance when cool resulting in high starting capacitance. After motor starts, the start winding current heats up the PTC causing its resistance to rise, lowering the effective capacitance to the start winding.

Issue with this method is it takes some off time for the thermistor to cool back down to lower its resistance to achieve larger starting capacitance again.

Normal thermostat cycling of refrigerator gives enough off time, but if you are experimenting with an inverter, reapplying power with short off period gaps you may get higher starting surge current time period due to lack of sufficient cooling of thermistor and resulting lack of starting capacitance.

Refrigerators also need some off time to allow the refrigerant gas to equalize pressure and relief compressor from having to start up against a high output head pressure which increases startup surge current.

There is no simple method to reduce start up surge current. Just make sure start capacitor is good. It is electrolytic based to achieve high capacitance in a small size and electrolyte will eventually dry out reducing capacitance.

Another failure mode is the thermistor goes bad, usually the connection wire separates from the carbon puck that makes up the thermistor.

Defrost heaters are wild card with regards to their required current draw. Some refrigerator have high power heating elements that duty cycle on and off to defrost. Others have a lower power heating element that just stays on for about 15-30 minutes. I have seen defrost heaters as low as 200 watts and as high as 1000 watts for typical residential refrigerators. Defrost cycle usually runs every 14 to 20 hours.

Then there are ice makers. They sometimes have a heater to dislodge ice from tray.

If you want to be fairly sure you can run a residential refrigerator, I recommend a 2000 VA inverter. You might get away with a smaller inverter but need to test for peak load current. Catching a defrost cycle at 3 am in the morning is challenging.