Solar Powered Fridge(s) Cause Glitchs/Spikes/Drops/dips

[GT250]

Hi all.
Good to see Trash running around

Have some solar panels and batteries that provide power via a 2400W PSW inverter into the house. Quite a few appliances are run off this;

I have noticed (only observed at night), that the house lamps (ambience), flicker/dim for a short while when - I suspect - one of the 2 fridges (small one and a bar fridge), cut in.
I've had a few psu's (the electronic type), fail - but never the 'old' transformer copper type.

Due to a potential upgrade of Panels and Batteries, I'm hoping to put our main (expensive), TV, computers (My understanding is that the PC's should be ok as the PSU in them should take the 'hit'), and our main food Fridge (expensive) onto the solar batteries.

I'm fearing (the wife's wrath mainly), of damaging these 'luxury/critical' items with those 'dips' in power.

Is there some sort of capacitor, 'Surge Drop' device I can use to offset/absorb this dip of power?

I understand a UPS on each GPO should do the trick, but I'm wondering if there's a more less bulky, maintenance/replacement and cheaper way to do it.

Cheers,
GT250

[lsemmens]

A UPS for each GPO sounds expensive, It might be worth investing in a UPS for the entire house, or, at least, a surge arrestor.

[Tiny]

Hi all.
Good to see Trash running around

Have some solar panels and batteries that provide power via a 2400W PSW inverter into the house. Quite a few appliances are run off this;

I have noticed (only observed at night), that the house lamps (ambience), flicker/dim for a short while when - I suspect - one of the 2 fridges (small one and a bar fridge), cut in.
I've had a few psu's (the electronic type), fail - but never the 'old' transformer copper type.

Due to a potential upgrade of Panels and Batteries, I'm hoping to put our main (expensive), TV, computers (My understanding is that the PC's should be ok as the PSU in them should take the 'hit'), and our main food Fridge (expensive) onto the solar batteries.

I'm fearing (the wife's wrath mainly), of damaging these 'luxury/critical' items with those 'dips' in power.

Is there some sort of capacitor, 'Surge Drop' device I can use to offset/absorb this dip of power?

I understand a UPS on each GPO should do the trick, but I'm wondering if there's a more less bulky, maintenance/replacement and cheaper way to do it.

Cheers,
GT250

I suspect that the surge is as you say the fridge turn on surge, this is common for fridges to have a surge way above their rated draw at pump/motor turn on & possibly defrost element start-up - if it has auto defrost.

The PSW Inverter you have, is it rated at 2400W continuous or is that the surge rating?

The other factor here is that your current battery capacity is too low for the surge rating of the Inverter & appliances connected to it, so it's quite possible that when you upgrade the batteries the problem will go away.
Adding to the solar input as you are doing in the upgrade to keep the batteries topped up better certainly is beneficial as well.

I run a completely standalone power system in my house, 1900AH 12V BAE SLA batteries (recently added as an upgrade 15 months ago), 12V/24V - 1200W Continuous rating Selectronic SA21 PSW Inverter with 3600W Surge rating & 1800W half hour rating (18 years old).
Incoming power is 560W solar, 240W continuous Micro hydro turbine.
I run a 420l 240v Fridge,
F&P washing machine,
3 satellite decoders,
PC with a 850W PSU,
1200W Surround sound system,
Satellite modem & wireless router.
Cordless phones, battery chargers etc.

I currently don't have any dips in power that upset my equipment, nor do the lights dim at any time from start-up surges.

I did however experience similar power dips as what you are describing when my last set of batteries was coming to the end of their life cycle (16 years). I thought my fridge was the problem but it turned out to be the batteries.

The batteries when in good condition & rated correctly for your power draw demands are the best power buffer (capacitor) you can have, when they are underrated, undercharged or failing due to age they work like a faulty capacitor.
Your batteries & other system components when looked after will be better than any UPS.

[Skepticist]

I think you're on the money there. The 'locked rotor' current of an electric motor is the instantaneous current it takes in the milliseconds between switch-on and the rotor actually starting to move and can be as much as 10 times the running current in that initial burst because, without any back emf from rotation, the motor is essentially a short circuit across the mains with the current limited only by the impedance of the windings

[gordon_s1942]

In the 'GOOD Old Days' it was common to see and hear the 'fridge cut in' but rarely today.
It doesnt matter but you dont say if your totally 'Off Grid' or still use the Mains but I was thinking that basically you are running a UPS now even if your 'OFF GRID' ignoring what charges your Batteries, with them and an Inverter to supply power so adding a UPS is just doubling up what you already have.

[GT250]

Hi all,
Thanks for the replies.
The PSW inverter is continuous 2400 and surge 4800. I'm not totally off grid and I power most things from the inverter, besides the main fridge, main TV.

I also don't use the batts for the main PC because it has dual screen, big PSU and dual Video cards and the hours it's on would be a large drain.
I have 8 T105-RE's @ 24v

There's plenty of solar power as I added 8 more 190w panels and the batts after a full days usage are fully charged (sun on panels about 7:00am), at about 10:00am. Have been 3 days of very inclement weather and the batts never went below 23v.
Since I added the panels I wanted to add another 4 T105-RE's and go fully off grid. But I'm concerned about this power 'dip'. This dip probably lasts for 1/4 of a sec.
The Microwave 1000w clock is never effected, so there's no actual loss of power per se.

The bar fridge, definitely 'Cut's in' and the other chiller fridge.

[gordon_s1942]

This 'Dip' may only be specific to that particular Fridge or that model which is no help to you what so ever.
Years past I remember buying a devise about the size of a cigarette box you plugged into the power point and it was supposed to 'suppress' spikes and surges in the Mains.
That was when all TV's were vacuum tubes and the picture would shrink a bit around Tea Time when everyone was using the power.

My only worry with power 'dips' would be if it was causing a spike that MIGHT damage something otherwise its not a problem because 'dips' occur on the Mains' during electrical storms which if you were 'OFF Grid' shouldnt affect you.
The only other idea would be (if your idly rich and cost is no problem) to consider installing a setup that can be joined into the main system if required but basically stands alone to run the Fridge(s) by themselves, ie: Solar panels, Batteries, Inverter and feed to the appliances.

[Uncle Fester]

That inverter should handle a fridge. As mentioned above your battery has to be up to it.
A 24V/100Ah battery will drop a volt or two if it gets hit with a 100A surge and the inverter has to respond to that.
Of course Tiny's 1900Ah battery would barely budge somewhere in the tens of millivolts.

Don't forget the battery wiring.
Connections might just need a bit of cleaning with a wire brush or sandpaper.

Edit: just checked your 8x T-105RE, they should be fine but you need a lot of cable bridges for that set up. Only one has to have a bad connection. Only way is take them off and sand them. Oxidation is not always visible.

[Tiny]

Hi all,
Thanks for the replies.
The PSW inverter is continuous 2400 and surge 4800. I'm not totally off grid and I power most things from the inverter, besides the main fridge, main TV.

I also don't use the batts for the main PC because it has dual screen, big PSU and dual Video cards and the hours it's on would be a large drain.
I have 8 T105-RE's @ 24v

There's plenty of solar power as I added 8 more 190w panels and the batts after a full days usage are fully charged (sun on panels about 7:00am), at about 10:00am. Have been 3 days of very inclement weather and the batts never went below 23v.
Since I added the panels I wanted to add another 4 T105-RE's and go fully off grid. But I'm concerned about this power 'dip'. This dip probably lasts for 1/4 of a sec.
The Microwave 1000w clock is never effected, so there's no actual loss of power per se.

The bar fridge, definitely 'Cut's in' and the other chiller fridge.

With your 8x T105-RE's configured for 24V you have 500Ah @24V at the 100Hr rate which is a mid range - small battery capacity.

This is where your power dip is coming from with the Fridges; as your inverter, unless it's faulty, should not blink at those fridges.

Now adding another 4x T105-RE's, in series & parallel, connected into your current battery bank would bring you up to 750Ah @24v at the 100Hr rate, which would be a definite improvement & likely cure the supply current dip, however the difference in age of the new cells to the old cells could be a potential hazard to your battery setup.

The new batteries will be marginally stronger & more efficient to a degree that will likely cause your battery cells to be unevenly discharging & charging, making it a big strain on the old cells to achieve cell equalization during the cell equalization cycle of your charge controller/regulator, this can prematurely end the life of older cells or possibly the newer cells in the string.

It is not recommended to add new cells into an old battery configuration.

When you say your batteries never went below 23V during inclement weather, that's quite low. My inverter low battery warning alarm would go off.
As lead acid batteries comprise configurations of 2.1volt cells; that 23 V=1.916 volts per cell compared to 2.1 - 2.13V of a fully charged lead acid battery cell at rest (OCV).

I would be concerned if my batteries dipped below 2V/cell unless they were being discharged at a very high rate by using some pretty hefty continuous loads like a large vacuum cleaner, toaster or hairdryer.(BTW hairdryers are banned from use on my system).
Your fridges starting up & running at the same time may produce this amount of load on your setup?

Also as nomeat has stated, contacts of the battery connections need to be regularly checked for continuity & cleaned regularly as well as checking individual cells or cell strings for voltage differences.
In your case, hydrometer readings at monthly intervals & water top up when necessary would be advisable as well.
Luckily in my system the 6 & 2.1v cells have double connections between cells with a relatively large contact area giving an excellent current flow across the battery bank.

Hope that helps.

[gordon_s1942]

I was reading Tiny's comment about banning Hair driers but those and any sort of appliance that uses a heating element ie Radiators, Electric jugs, Toasters etc must be real power suckers and to be avoided at all costs.

I was wondering if the old tricks of 'sealing' the battery terminals and bare connections commonly used on cars after giving them a good clean, was to put a smear of Vaseline/Petroleum Jelly on or those oil impregnated pads put under the connector which tended to minimise corrosion or electrolytic action between the battery terminal and the connector, even on those bolt on types, would be helpful on those battery banks.

[Skepticist]

This reminds me of someone I know who was trying to run a water pump from a portable generator (for blackouts) and the small generator was rated just marginally higher than the pump's rated running load. It was a total failure as the generator stalled and tripped on the starting current of the pump.

[Tiny]

I was wondering if the old tricks of 'sealing' the battery terminals and bare connections commonly used on cars after giving them a good clean, was to put a smear of Vaseline/Petroleum Jelly on or those oil impregnated pads put under the connector which tended to minimise corrosion or electrolytic action between the battery terminal and the connector, even on those bolt on types, would be helpful on those battery banks.

There is a slightly more upmarket solution than Vaseline, we use conductive grease to coat the connections to prevent corrosion & decrease resistance in the connection.

[gordon_s1942]

That 'conductive grease' been available for years but you cant beat the old petroleum jelly for price and availability as we always had some back then when our children were little for the treatment of Nappy Rash.
I must say however I never put it between any connectors, only over it as an air seal because I have no idea how conductive it is unlike the conductive grease which is designed for the application.

[GT250]

Hi Tiny.

With your 8x T105-RE's configured for 24V you have 500Ah @24V at the 100Hr rate which is a mid range - small battery capacity.

* Many thanks Tiny for your very informative replies.

This is where your power dip is coming from with the Fridges; as your inverter, unless it's faulty, should not blink at those fridges.

* It's the Bar fridge and/or the chiller fridge causing the 'dip'. I'm pretty sure.

Now adding another 4x T105-RE's, in series & parallel, connected into your current battery bank would bring you up to 750Ah @24v at the 100Hr rate, which would be a definite improvement & likely cure the supply current dip, however the difference in age of the new cells to the old cells could be a potential hazard to your battery setup.
The new batteries will be marginally stronger & more efficient to a degree that will likely cause your battery cells to be unevenly discharging & charging, making it a big strain on the old cells to achieve cell equalization during the cell equalization cycle of your charge controller/regulator, this can prematurely end the life of older cells or possibly the newer cells in the string.
It is not recommended to add new cells into an old battery configuration.

* It has been on my mind to add 4 more batteries, but as time has gone on, I left it as I knew the panels I had were ok for that size. Now I have more panels, I can see that I would be ok to add 4 more. But the missies would freak out at 4 more. (this would be my second set of 12xT105's as when I started all this solar stuff, I was woefully inexperienced in this field and I didn't manage them correctly, 10 years ago.
So to 'ask' for 12 new ones would be inviting me living in the dog shed.

When you say your batteries never went below 23V during inclement weather, that's quite low. My inverter low battery warning alarm would go off.
As lead acid batteries comprise configurations of 2.1volt cells; that 23 V=1.916 volts per cell compared to 2.1 - 2.13V of a fully charged lead acid battery cell at rest (OCV).
I would be concerned if my batteries dipped below 2V/cell unless they were being discharged at a very high rate by using some pretty hefty continuous loads like a large vacuum cleaner, toaster or hairdryer.(BTW hairdryers are banned from use on my system).

* With dropping below 23v, aren't these called DEEP cycle for a reason? My Inverter is designed to warn at 21.5v. My Solar inverter is this one and I have been very happy with it.

Your fridges starting up & running at the same time may produce this amount of load on your setup?

* Yes, I see. I decided to put the expensive fridge onto solar a few days ago and with still a few days of inclement weather the batteries are still getting fully charged nicely. So now 3 fridges are on. Hopefully they all don't cut in at the same time

Also as nomeat has stated, contacts of the battery connections need to be regularly checked for continuity & cleaned regularly as well as checking individual cells or cell strings for voltage differences.
In your case, hydrometer readings at monthly intervals & water top up when necessary would be advisable as well.
Luckily in my system the 6 & 2.1v cells have double connections between cells with a relatively large contact area giving an excellent current flow across the battery bank.

* I do get that green oxide forming around - only some - terminals. I use CRC Battery Terminal Protection, but I still seem to get that green oxide.
Any chance of a photo of your 'double' connections?


* I thank you for the time you have spent to reply to me.
I have to weigh up adding 4 new batts to my system and the loss/benefits to the old/new. I just can't go new 12qty. Plus the ones I have now are 4yrs old. But have been properly looked after.


Hope that helps.

Please read the * in the post above.
Sorry.

[GT250]

I was reading Tiny's comment about banning Hair driers but those and any sort of appliance that uses a heating element ie Radiators, Electric jugs, Toasters etc must be real power suckers and to be avoided at all costs.

I was wondering if the old tricks of 'sealing' the battery terminals and bare connections commonly used on cars after giving them a good clean, was to put a smear of Vaseline/Petroleum Jelly on or those oil impregnated pads put under the connector which tended to minimise corrosion or electrolytic action between the battery terminal and the connector, even on those bolt on types, would be helpful on those battery banks.

Hi Gordon,

With this thermal grease being mentioned around - I mentioned in my reply to Tiny about still getting green oxide on some terminals - What sort should I use? And no I don't your old trick of good old Vaseline is the way to go
I found this on Feebay 301631310226 what do you think?

[GT250]

There is a slightly more upmarket solution than Vaseline, we use conductive grease to coat the connections to prevent corrosion & decrease resistance in the connection.

What do you use Tiny and where can I buy it?

[GT250]

That inverter should handle a fridge. As mentioned above your battery has to be up to it.
A 24V/100Ah battery will drop a volt or two if it gets hit with a 100A surge and the inverter has to respond to that.
Of course Tiny's 1900Ah battery would barely budge somewhere in the tens of millivolts.

Don't forget the battery wiring.
Connections might just need a bit of cleaning with a wire brush or sandpaper.

Edit: just checked your 8x T-105RE, they should be fine but you need a lot of cable bridges for that set up. Only one has to have a bad connection. Only way is take them off and sand them. Oxidation is not always visible.

Yeah, I have to clean them as I do have this green oxide on some terminals, even though the terminals are coated in that CRC Battery Protections stuff.
So you're correct that some oxidation might be between the actual terminals and lugs.

I'll see about what the experts say about this Conductive Grease and if I should clean everything and rebolt it all up and apply this grease..

[Tiny]

* It has been on my mind to add 4 more batteries, but as time has gone on, I left it as I knew the panels I had were ok for that size. Now I have more panels, I can see that I would be ok to add 4 more. But the missies would freak out at 4 more. (this would be my second set of 12xT105's as when I started all this solar stuff, I was woefully inexperienced in this field and I didn't manage them correctly, 10 years ago.
So to 'ask' for 12 new ones would be inviting me living in the dog shed.

It is possible that you can connect the newer string into your system separated by an appropriately rated Voltage Sensitive Relay (VSR) to protect the new from old.
There are 2 types. The first is analogue (usually not adjustable) used in vehicle dual battery set-ups. Not really suited to this application.
The second type is digital (cheep will not be adjustable); usually programmable on all parameters & bidirectional (this would be necessary for this type of installation). Will most likely be very expensive for a high amperage unit. Also used in some high end motor vehicle dual battery set-ups.
This is not the ideal way to go for large capacity battery systems.

EDIT: have just had a look around & really can't find a DVSR that would make this a simple job as most are designed around charging only & disconnect the batteries during load, so you would need to run the old battery bank as your main power source & use the new bank for lighting & sensitive equipment. Items with not as much draw as your main power equipment. That will likely require another inverter. Getting expensive to go that way.

The ideal way to have a large capacity system is to have your 2.1V cells rated at the Ah capacity needed & join enough of them in series to get the voltage required for the system.
Advantage of the later is less cells to get out of balance; as one poorly performing cell can ruin the whole system.

Either way with both series & parallel cells, you cannot add new cells to an old bank of cells without risk.
They really need to be identical in capacity & voltage & from production runs from the same time.
My last battery bank only failed on one cell, the positive side of that is they were 16 years old, the negative side is I spent $6800 on the replacement set. That's why I look after them.

* With dropping below 23v, aren't these called DEEP cycle for a reason? My Inverter is designed to warn at 21.5v. My Solar inverter is this one and I have been very happy with it.

Discharge voltage of a lead acid battery & capacity are hard to reconcile.
General voltages.
Open Circuit Voltage after rest fully charged is ~2.1V per cell & = 25.2V in a 24V system.
Open Circuit Voltage fully discharged is ~1.95V per cell & = 23.4V in a 24V system.
During load/draw voltage fully discharged is ~1.75V per cell & = 21.0V in a 24V system.
As you can see by the last 2, you may be getting close to fully discharging your batteries depending on the load/draw on them.
As you have a large amount of incoming power from your solar panels, these relatively small batteries can reach a voltage, whilst charging & zero to light loading, that appears to be all good; however the batteries may not be as charged to capacity as you think. Hydrometer readings will tell the truth as will OCV.
Another good method of keeping an eye on relative battery capacity state of charge is to have a shunt type battery programmable monitor that counts amps in & out of the system, with a degree of battery efficiency calculated in & is based on the percentage of total battery capacity at the 20 hour rate. My inverter has this integrated into the system.

Yes, Deep Cycle batteries are rated to handle at moderation "deep cycling", however the deeper the cycle & more often the deep cycle, the shorter their lifespan.
The shallower DOD you cycle your batteries to will increase their lifespan.
It all depends on how often you are prepared to replace them?

The following graph from the manufacturers of my BAE 1900AH Deep Cycle batteries explains it all.
Remember here you can relate 1 cycle to 1 day of life of the battery.


You may recognise this bit, it's from a PM we had a year ago.

* I do get that green oxide forming around - only some - terminals. I use CRC Battery Terminal Protection, but I still seem to get that green oxide.
Any chance of a photo of your 'double' connections?

2 reasons for green oxide, resistance due to inadequate connection.
Different metals at connection point combined with vapour from battery gassing causes electrolyses.
Both can be reduced with
My first set of large format deep cycle lead acid batteries came with a tub of conductive grease & I still have enough left for usage.
As I have never had to buy any I can't recommend a brand or type, there are many.
There is silver based, carbon based, etc.
The type I have is black which would suggest it is carbon based.
You will need to clean the terminals, file & sand paper as necessary to remove all oxide from connecting surfaces, brush away any grit, then apply grease to all connective surfaces & bolts, tighten all bolts then smear to cover connections & bolts. Messy job with the black stuff - you will need a good quality hand cleaner.
May need repeating yearly or as necessary.

My old set of batteries had a clear plastic cover to fit over the connections to guard against getting grease on me & my tools when performing maintenance & to prevent dust collection on the grease.
My new batteries have an anti-oxidation coating on the bolts & connecting cables (feels rubbery), so only tiny amount of grease needed on the connecting surfaces, totally out of sight.


Here are my double battery connections, my batteries are designed & equipped with them, your T-105-RE's are not.
For a size perspective; they are 23mm heads on those connecting bolts.




Hope that helps.

[gordon_s1942]

Although some may look askance at my usage of Vaseline/Petroleum jelly, it was an ACCEPTED practice to do so on car battery terminals as was the oil soaked 'felt pad' under the connector with a view of both sealing the connection from air or gas's from the battery.
To make it totally clear, none of these products was ever applied to the contact surfaces, only under and on top.
Another was to use a mixture of water and Baking Soda/Powder on a cloth and wipe all the surfaces, it was excellent in removing any build up of that 'Green Oxide' (Verdigris) that had built up on the terminals.
The warning here is that Baking Soda/Powder is an Alkali and will KILL a battery stone dead if it gets into the cells.
A thorough clean using emery tape or a wire brush to get the contact faces as shiny as possible followed the use of Baking Soda/Powder cleaning.

The era these items were used was when motor vehicles had generators and with their lower ability than an alternator to charge a battery, it was as important back then to keep the terminals as clean as possible as it is today to get the best out of Solar Panels generating power into batteries.

[Tiny]

Although some may look askance at my usage of Vaseline/Petroleum jelly, it was an ACCEPTED practice to do so on car battery terminals as was the oil soaked 'felt pad' under the connector with a view of both sealing the connection from air or gas's from the battery. To make it totally clear, none of these products was ever applied to the contact surfaces, only under and on top. Another was to use a mixture of water and Baking Soda/Powder on a cloth and wipe all the surfaces, it was excellent in removing any build up of that 'Green Oxide' (Verdigris) that had built up on the terminals. The warning here is that Baking Soda/Powder is an Alkali and will KILL a battery stone dead if it gets into the cells. A thorough clean using emery tape or a wire brush to get the contact faces as shiny as possible followed the use of Baking Soda/Powder cleaning. The era these items were used was when motor vehicles had generators and with their lower ability than an alternator to charge a battery, it was as important back then to keep the terminals as clean as possible as it is today to get the best out of Solar Panels generating power into batteries.

Not at all Gordon, I used both those products until I discovered Conductive grease & would still use Bicarb/baking soda for cleaning acid affected metals.