Initial high amp draws - Solar Charge controllers

jaunty · Aug 23, 2015

I am finding that most solar charge controllers have low Amp ratings(10-30A). I recently converted a mini-fridge into a chest mini-fridge and am running it off my lead acid battery connected to the charge controller rated for 20A. When the fridge initially kicks on, it pulls nearly 40A and the charge controller cuts off (does not exceed the compressor LRA rating). My remedy was to connect the inverter directly to the batteries and not through the charge controller. The only problem here is I lose the low voltage cutoff function from the charge controller.

Anybody have any suggestions here. Not a huge deal, i shouldnt have to worry about low voltage cut off if I have the proper battery capacity.

Could a capacitor after the charge controller alleviate this? If the capacitor capacity was high enough it could provide those initial few seconds of high current.

dnmun · Aug 23, 2015

for AC motors a capacitor is included across the power line so it can help to start an induction motor.

do you have a DC motor on the mini frig or AC motor?

you could also build a PWM controller with a timer ramp to slow the inrush current into the motor as it starts if it is a DC motor.

jaunty · Aug 23, 2015

Its an AC motor. I found that the DC motors are very expensive and hard to find. So i'm using an inverter.

Thanks for the tip on the PWM timer ramp, i'll look into those.

Gregory · Aug 23, 2015

At one work site a big air compressor kept tripping the breakers when it kicked in. The electrician installed an AC soft start on it and it solved the problem.
Though from memory it cost hundreds.

amberwolf · Aug 23, 2015

jaunty said:
I recently converted a mini-fridge into a chest mini-fridge

OT, but could you post a bit about what you did to do this?

I have a regular size standup refrigerators that I'd like to turn into chest-type, at some point, for efficiency's sake (so as not to waste so much cold air every time it is opened).

jaunty · Aug 24, 2015

yes...
I basically unbolted the mount that holds the compressor and twisted it so that it remained upright. Then I built a base so that the radiator on the back was off the ground.

heres a vid
https://www.youtube.com/watch?v=jYeVxlJ0qnM

jaunty · Aug 24, 2015

yes i am thinking it is a bit more efficient but I never did take any measurements before the conversion.

fechter · Aug 24, 2015

Most inverters have their own low voltage cutoff. It might be OK.

dnmun · Aug 24, 2015

try reading some of these references:

https://www.google.com/#q=capacitor+start+ac+induction+motor

amberwolf · Aug 25, 2015

jaunty said:
yes...
I basically unbolted the mount that holds the compressor and twisted it so that it remained upright. Then I built a base so that the radiator on the back was off the ground.

heres a vid
https://www.youtube.com/watch?v=jYeVxlJ0qnM

Thanks--that helps some. I think it is going to be more complicated than that for my conversion, though.

jaunty said:
yes i am thinking it is a bit more efficient but I never did take any measurements before the conversion.

I have a small deepfreezer that's chest-type, and even when I accidentally left the lid open when I left for work one day, coming back many hours later, everything was still frozen (even the stuff on top), and the daily power usage data didn't show that much extra power wasted by this.

If I'd done that to an upright unit, eerything would have been thawed, and power usage would have been many times what it normally takes, as it would never have shut off.

So that alone should show the chest-type efficiency being significantly higher, assuming it gets opened a lot, or if the door has to be left open any significatn time (like when putting groceries away).

icerider · Jan 9, 2016

I just speed read the thread so if I missed something, I apologize.

Jaunty, if you just want a simple relatively cheap fix, run a relay off the controller and route the power from battery to frige through the contacts on the relay

When the LVC trips, it will lift the fridge load from the battery.

You can use relatively low current contacts on the relay since it will not be interrupting the starting load but the running load.

mountain biker · May 31, 2016

so how goes it. did you find a solution. ebay sounds like 1000 bucks for 12 volt 1000 watt continous invertors. 200 bucks for 24 volt system. maybe doable. there is a few videos on you tube of stacking. meaning you get two or three 20 dollar 300 watt continous controllers and put them together.... so did you find a solution?

craneplaneguy · May 31, 2016

http://www.sundanzer.com/product/dcr225-dcf225-2/

craneplaneguy · May 31, 2016

http://www.wholesalesolar.com/3510605/outback-power/charge-controllers/outback-power-flexmax-fm80-charge-controller?gclid=Cj0KEQjw7LS6BRDo2Iz23au25OQBEiQAQa6hwEDqmSN1fAjBeLH-B7Gs7WzDNXiUoCAhGsklHg8HdyYaAuhB8P8HAQ

craneplaneguy · Jun 27, 2016

The LVD of most controllers (LOW VOLTAGE DISCONNECT) is not meant for major loads, that is your problem. Just wire the freezer direct to the inverter. It, unless it's Harbor Freight junk, should have it's own LVD.

Syonyk · Sep 16, 2016

fechter said:
Most inverters have their own low voltage cutoff. It might be OK.

++

What inverter are you using that doesn't have its own LVC? Most of them will cut off at something sane, and you'll be fine.

I treat the "load" terminal on most cheap charge controllers as a waste of metal that I won't bother with.

But a relay driven from that load terminal is a good option too, if you really need the controller's LVC (custom LVC for lithium?).

amberwolf said:
So that alone should show the chest-type efficiency being significantly higher, assuming it gets opened a lot, or if the door has to be left open any significatn time (like when putting groceries away).

"Cold air sinks."

Yes, they're better about having the door open.

Initial high amp draws - Solar Charge controllers

jaunty

1 W

dnmun

1 PW

jaunty

1 W

Gregory

100 kW

amberwolf

Administrator

jaunty

1 W

jaunty

1 W

fechter

Administrator

dnmun

1 PW

amberwolf

Administrator

icerider

100 W

mountain biker

100 W

craneplaneguy

10 kW

craneplaneguy

10 kW

craneplaneguy

10 kW

Syonyk

10 kW

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