Soft Starters for motors ,Fridges etc.

non-EV Solar, Wind and other renewable power sources
non-EV batteries and other energy storage stuff
Forum rules
Important!
This forum is for discussion of Non-EV matters.
Post Reply
TyTower
Groupie
Posts: 63
Joined: Thu, 17 Dec 2020, 05:25

Soft Starters for motors ,Fridges etc.

Post by TyTower »

I have the problem that in the early hours of the morning when my battery is getting low my freezer turns on and pulls a huge start current out before it settles to a steady drain .
The Inverter handles the normal running current no problem but the huge drain to start it pushes the battery voltage down just enough to trip the low battery alarm and than I have to get up to turn the inverter off to silence it . Because it will do the same again I have to remove the freezer's plug to a grid supplied one before switching my inverter back on .

So is there anything I can build or buy to stop this sudden fall in voltage of my battery?
Is anyone using or have used a supercapacitor bank on their batteries to accommodate this ?
shallowal
Groupie
Posts: 77
Joined: Sat, 03 Oct 2020, 14:58
Real Name: Allan

Re: Soft Starters for motors ,Fridges etc.

Post by shallowal »

Put a timer on your fridge so that it doesnt try to start until the sun is up.
Or better still, a switch over relay that puts the fridge onto the mains until the battery is charged.

The problem with fridges is that they start under the highest load which reduces as the gases that they pump normalises their pressures.
antiscab
Senior Member
Posts: 3183
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Re: Soft Starters for motors ,Fridges etc.

Post by antiscab »

adding capacitors adds about the same amount of self discharge as just adding more battery.
depending upon what sort of battery you have, cost might not be too different either

Ian Goh has a supply of maxwell super caps: https://www.facebook.com/groups/SuperCapAustralia

another option would be switching to an inverter fridge, those don't draw extra on start up, though are a bit on the pricey side
Matt
2023 BYD Atto 3 - 21k km
2017 Renault zoe - 147'000km
2012 Leaf - 101'000km - soon to be trialing a booster battery
2007 Vectrix - 197'000km (retired)
2007 Vectrix - 50k km
T1 Terry
Senior Member
Posts: 1952
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Soft Starters for motors ,Fridges etc.

Post by T1 Terry »

All the new fridges and freezers are inverter type, that was the only way they could compete with each other on the energy star rating system. I wouldn't consider the price of the new inverter type appliances to be that savage compared to what they are asking for extra low voltage stuff that doesn't perform near as well.
You can do the soft start in a number of different ways, the easiest is a discharge valve to dump the head pressure on the compressor back into the intake side and a timer to hold it open until the compressor is up to speed. It is the high head pressure that causes the real big current draw, the capacitor start isn't near as severe although it does take more than the normal run current. For the cost or a soft start electrically and a dump discharge valve to reduce the head pressure, a few more $$ will buy you a new inverter type freezer/fridge that uses less power over all and has a much softer start up.

As far as battery voltage drop, what battery capacity and cell manufacturer? Where do you measure the battery voltage and what delay have you set to eliminate the false alarms ... and what alarm clear voltage do you have set? Actually, what battery monitor are you using? The Victron 712BMV?

T1 Terry
Green but want to learn
TyTower
Groupie
Posts: 63
Joined: Thu, 17 Dec 2020, 05:25

Re: Soft Starters for motors ,Fridges etc.

Post by TyTower »

T1 Terry wrote: Thu, 11 Mar 2021, 11:34 As far as battery voltage drop, what battery capacity and cell manufacturer? Where do you measure the battery voltage and what delay have you set to eliminate the false alarms ... and what alarm clear voltage do you have set? Actually, what battery monitor are you using? The Victron 712BMV?
T1 Terry
as in the first post ,it is an alarm as the voltage of the battery being low at that time in the morning gets pulled down just enough to trigger an alarm which does not stop until I switch the inverter off and back on. If there is a delay on it I have not noticed it and I don't know if it has an alarm clear? Never heard of it.
I am dealing with an MPP Solar HV2-5048 here which is where the alarm is coming from.
Battery is a 200Ah LFP and cut off on the inverter is set to 50 volts.

However Terry I am more interested in the Ultra/Super Capacitor solution.
User avatar
coulomb
Site Admin
Posts: 6357
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Re: Soft Starters for motors ,Fridges etc.

Post by coulomb »

TyTower wrote: Thu, 11 Mar 2021, 15:52 Battery is a 200Ah LFP and cut off on the inverter is set to 50 volts/
If that's a 15S LFP battery, then 50 V is far too high. If it's 16S, you might want to try 49 or even 48 V for the low battery cut-off setting (or somewhere in between, if the inverter lets you).

I assume that these hybrid MPPSolar inverters work much the same as the off-grid models as far as battery cut-off is concerned, in which case they won't have battery voltage compensation for load current.
MG ZS EV 2021 April 2021. Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
Patching PIP-4048/5048 inverter-chargers.
If you appreciate my work, you can buy me a coffee.
TyTower
Groupie
Posts: 63
Joined: Thu, 17 Dec 2020, 05:25

Re: Soft Starters for motors ,Fridges etc.

Post by TyTower »

You would know better than me for sure .
Its a 16 S battery.
In fact I noticed the inverter won't let me set the low voltage below 50v.
I wondered about that but just ended up going with it . It reliably holds the battery top at 54v or 53.9v on the screen so I like that. That's where I want the top to stay.
I would like to get the low to 48v though if you can suggest a way.


I'd like to know what "battery voltage compensation for load current." means also thanks Coulomb
User avatar
coulomb
Site Admin
Posts: 6357
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Re: Soft Starters for motors ,Fridges etc.

Post by coulomb »

TyTower wrote: Fri, 12 Mar 2021, 06:44 I'd like to know what "battery voltage compensation for load current." means also thanks Coulomb
Battery voltage sags under load. So using a fixed limit is simplistic. What Weber does in our fully patched firmwares is he uses the battery current measurement to compensate (adjust) a voltage reading, to estimate what it would have been with no load. There is provision for 5 "strengths" of adjustment, and it takes into account the maximum charge current (so larger batteries get compensated less). It's crude, and certainly not perfect, but it helps with nuisance alarms and switching to grid unnecessarily. Unfortunately, there is no patched firmware for your model. We had hoped that Voltronic Power would follow our lead, but they don't even fix the premature float bugs, which are what started us patching some five years ago.
MG ZS EV 2021 April 2021. Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
Patching PIP-4048/5048 inverter-chargers.
If you appreciate my work, you can buy me a coffee.
T1 Terry
Senior Member
Posts: 1952
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Soft Starters for motors ,Fridges etc.

Post by T1 Terry »

You could always silence the alarm .......

T1 Terry
Green but want to learn
TyTower
Groupie
Posts: 63
Joined: Thu, 17 Dec 2020, 05:25

Re: Soft Starters for motors ,Fridges etc.

Post by TyTower »

I found a utube video online at electronicsNmore
https://youtu.be/1MPW1dqulWw

I made the device with 2x 5 Ohm SG333 Inrush Limiters: https://amzn.to/2xLD9CY
That's his link

It got pretty hot judging by the smell of it and being inside the house I was a bit reluctant to keep using it .
My inrush davices were rated a little less and my switch might be a little under the rating too.

Works fine outdoors though if I ever want to run my grinder but my supply is big enough to handle it on its own so I doubt I'll use it for that .

Looks like a simple timer might be the go here .
User avatar
coulomb
Site Admin
Posts: 6357
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Re: Soft Starters for motors ,Fridges etc.

Post by coulomb »

TyTower wrote: Sun, 09 May 2021, 04:40 It got pretty hot judging by the smell of it and being inside the house I was a bit reluctant to keep using it .
Those are NTC resistors, Negative Temperature Coefficient. So they start off with nominal resistance, say 5 ohms, and heat up in a second or less. As their temperature rises, their resistance falls, so they become closer to a short circuit. But they have to remain hot to keep their temperature low. So they'll always lose some power, and need to be positioned so that they won't have much dust settling on them, and have reasonable air flow. Hot dust has an annoying smell.

If you use one that is too small for the continuous load, that won't help.
MG ZS EV 2021 April 2021. Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
Patching PIP-4048/5048 inverter-chargers.
If you appreciate my work, you can buy me a coffee.
Post Reply