Power inverters

[Chicken lights]

There’s some pretty smart people on this forum when it comes to electronics. I started using a Cobra power inverter which worked very well for a couple years, when it quit I found a Samlex brand to replace it. I liked the samlex brand because it was a pure sine wave, allowing me to use a laser printer versus a bleeping inkjet. But it seems like they don’t like life in a truck, I get maybe a year out of one.

What’s more likely the reason they fail? Bouncing around down the road? Or working constantly to power a fridge?

My fridge quit a couple months ago, I understand those have a hard life with the compressor and other things bouncing around.

I’ll probably try to pick up a cheap power inverter this trip to get me home but now with Covid it might be tough to source another pure sine wave inverter.

One thought I had was run a cheap power inverter for fridge/microwave, then a second smaller pure sine wave inverter for the laser printer.

 

[Susquatch]

There’s some pretty smart people on this forum when it comes to electronics. I started using a Cobra power inverter which worked very well for a couple years, when it quit I found a Samlex brand to replace it. I liked the samlex brand because it was a pure sine wave, allowing me to use a laser printer versus a bleeping inkjet. But it seems like they don’t like life in a truck, I get maybe a year out of one.

What’s more likely the reason they fail? Bouncing around down the road? Or working constantly to power a fridge?

My fridge quit a couple months ago, I understand those have a hard life with the compressor and other things bouncing around.

I’ll probably try to pick up a cheap power inverter this trip to get me home but now with Covid it might be tough to source another pure sine wave inverter.

One thought I had was run a cheap power inverter for fridge/microwave, then a second smaller pure sine wave inverter for the laser printer.

Hmmmmm..... This is a toughy.

Without actually looking at what failed, it's hard to say why it failed. I'd guess it's probably a combination of the constant use, the bumpy ride, and perhaps temperature cycling too.

I remember getting a lot of criticism from the early electronics industry about why car and truck electronics were so unreliable compared to home tv's and radios. I used to respond with, "I wanna see how long your tv lasts out in the rain and snow bouncing down a gravel road". That used to shut them up fast. Your application is a good testament to that reality.

Most things will work just fine on a big relatively inexpensive square wave inverter. And I confess I'm a bit surprised that your laser printer wasn't happy with that too. I'd bet some are and some are not.

I like your idea of a small sine wave unit for the laser printer, and a big automotive grade inverter for everything else. I'd also try to mount both on a foam suspension to absorb the big vibrations and shocks.

But ya, that is a tough problem.

Maybe consider searching the internet for an RV unit that gets good ratings by the RV community.

Edit - look at small boat applications too. Those things also take a beating.

 

[CWelkie]

Every time I see/hear and discussion about inverters (and RV solar installations), I think of this website:

INVERTER ISSUES – Spring 2013

I need some photos, but I rarely take pictures of other people’s installations. The message will not wait………… I am over it. People keep contacting me and either aski…

handybobsolar.wordpress.com

The author may come across as "roughly forthright" but I reckon it's just his way of "calling a spade a shovel". The technical information there will always be valid even while any details about brands and service/support are dated. For many years, he has been recommending Magnum inverters.

I have not gone down the inverter rabbit hole for our RV but have followed his advice for revising the factory/dealer solar installation and charge controller/monitor. That was seven years ago without a single issue or regret.
FWIW ...

 

[Chicken lights]

Every time I see/hear and discussion about inverters (and RV solar installations), I think of this website:

INVERTER ISSUES – Spring 2013

I need some photos, but I rarely take pictures of other people’s installations. The message will not wait………… I am over it. People keep contacting me and either aski…

handybobsolar.wordpress.com

The author may come across as "roughly forthright" but I reckon it's just his way of "calling a spade a shovel". The technical information there will always be valid even while any details about brands and service/support are dated. For many years, he has been recommending Magnum inverters.

I have not gone down the inverter rabbit hole for our RV but have followed his advice for revising the factory/dealer solar installation and charge controller/monitor. That was seven years ago without a single issue or regret.
FWIW ...

That’s some great reading. An RV/solar setup must be different than using it in a truck? He makes reference to one brand that was bought out and now “it’s designed for an over the road truck”. Then further down he says he fixed a bad install and “he’s finally using his microwave off the batteries”

Aren’t RV fridges able to be run on propane or electric? Maybe RV’s have found the fridge to be a problem too. I’ve long wanted a deep cycle battery or batteries with a battery isolator dedicated to the power inverter side of things

I’ll look into Magnum power inverters, thanks!

 

[kevin.decelles]

I run this unit in my 5th wheel https://www.homedepot.ca/product/sunforce-2500-watt-pure-sine-wave-inverter/1000732658

I picked it up from Amazon.ca about 4 years ago -- still going. I didn't mount it 'rigid', rather I set it on 1.5" kneeling pad (foam) and used a piece of foam on top as a damper. I take it inside in the fall, put it back in in the spring.

I back-feed the trailer's power from this unit and it handles coffee machine, tea kettle, microwave no problem (not at the same time though). Boiling a pot of water puts a noticeable dent in the battery bank. I run two 5' panels on the roof, feeding to 4 6V golf cart batteries (creates 2 12V banks that are isolated from each other). The inverter drives off bank #1, and bank #2 feeds the trailers 12V system.

 

[CWelkie]

Yes, RV's (generally) use propane or electric as an energy source. I hope I haven't confused things in that regard; was only looking at it from an inverter perspective regardless of the type of load.
DC power is the same regardless of where it is but it seems most installations suffer from common issues that don't account for the significant amount of current involved. Small gauge wiring, long cable runs, and low battery charging voltages (in RV's) all lead to substandard performance and short lifespans.

 

[Chicken lights]

Hmmmmm..... This is a toughy.

Without actually looking at what failed, it's hard to say why it failed. I'd guess it's probably a combination of the constant use, the bumpy ride, and perhaps temperature cycling too.

I remember getting a lot of criticism from the early electronics industry about why car and truck electronics were so unreliable compared to home tv's and radios. I used to respond with, "I wanna see how long your tv lasts out in the rain and snow bouncing down a gravel road". That used to shut them up fast. Your application is a good testament to that reality.

Most things will work just fine on a big relatively inexpensive square wave inverter. And I confess I'm a bit surprised that your laser printer wasn't happy with that too. I'd bet some are and some are not.

I like your idea of a small sine wave unit for the laser printer, and a big automotive grade inverter for everything else. I'd also try to mount both on a foam suspension to absorb the big vibrations and shocks.

But ya, that is a tough problem.

Maybe consider searching the internet for an RV unit that gets good ratings by the RV community.

Edit - look at small boat applications too. Those things also take a beating.

I forget what failed on the Cobra, I was given a second one to try, they both were considered not worth fixing. Meaning the repair bill would be higher than a new one.

The inverters are in the bunk, usually mounted to a panel that’s mounted to the floor over 1” of insulation. The point on reducing shock is a good point, I’m on my third headlight in 6-7 months. I modified a truck junction box for the inline breaker for this system, to keep it out of the weather.

 

[Chicken lights]

Yes, RV's (generally) use propane or electric as an energy source. I hope I haven't confused things in that regard; was only looking at it from an inverter perspective regardless of the type of load.
DC power is the same regardless of where it is but it seems most installations suffer from common issues that don't account for the significant amount of current involved. Small gauge wiring, long cable runs, and low battery charging voltages (in RV's) all lead to substandard performance and short lifespans.

Nope, no confusion here. You just made me wonder if RV’ers have learned that fridges are too hard on consuming electricity long term, for the components in the system. Because they run quite often

 

[Susquatch]

Every time I see/hear and discussion about inverters (and RV solar installations), I think of this website:

INVERTER ISSUES – Spring 2013

I need some photos, but I rarely take pictures of other people’s installations. The message will not wait………… I am over it. People keep contacting me and either aski…

handybobsolar.wordpress.com

The author may come across as "roughly forthright" but I reckon it's just his way of "calling a spade a shovel". The technical information there will always be valid even while any details about brands and service/support are dated. For many years, he has been recommending Magnum inverters.

I have not gone down the inverter rabbit hole for our RV but have followed his advice for revising the factory/dealer solar installation and charge controller/monitor. That was seven years ago without a single issue or regret.
FWIW ...

This was an absolutely terrific read. Most of which I did not know.

It totally blows my mind that inverter outfits don't understand charging voltage tempetature compensation or GFCI panel connections.

Every car and truck ever built has temperature compensation in the charging system. Even the old ones before electronics had that.

Inverters are primary designed for what? To make 110 or 220 off of a 12V auto battery. So how could they screw that up? Totally completely amazing to me. But he is right. The world is full of outfits who don't give a rats butt about anything except taking your money from you.

All this entire rant is only about panel outputs and temp compensation though......

Tbat doesn't leave @Chicken lights with much option but to try a good morning star or Magnum inverter and hope that they understand vibration as well as they understand temperature. Both should be givens in a good inverter design.

 

[Susquatch]

Sorry @Chicken lights. I was busy reading and absorbing the article that @CWelkie shared.

Yes, refrigerators (and to a lesser extent freezers) are a big load - especially the compressor starting draw. A nice RV or truck fridge would have R24(million) insulation so it gets cold on the battery and then stays there on its own because of fantastic insulation. It's another given in the automotive world if you ask me...... But I've never seen that anywhere. Might be worth a look at that new "Yeti" company. They are obsessed with long lasting cold.

PS - Some of my friends and family have started to call me Yeti now that my fur has all turned snow white......

 

[CalgaryPT]

When I traded my F250 in for a new F150 two months ago the service guy at Ford told me that inverters have a limited service life due to vibration—but mostly due to temperature swings. Granted, at the time he was plugging the new "Power Onboard" with the F150s, which is an actual generator driven by the drive belt. In my case I have the smallest engine (2.7 EcoBoost) and it generates 2200W to the tailgate. But the largest engine can deliver 7000W, which is enough to drive a welder. There is still an inverter inside the cab which I think has better technology as I can now use my small ink jet on it which the inverter in the old truck didn't like. When the cold weather comes we will see. Reliability in cold months seems to be inversely proportional to complexity of the electronics. Also remember that discrete components and ICs come in different grades. For example, 7400 series TTL (Transistor Transistor Logic) ICs have a narrower operating temperature than the military/hi-end commercial 5400 series. (I think there are newer classes I am unaware of). The same is true of their sensitivity to vibration. Ditto for CMOS (Complementary Metal Oxide Semiconductor) electronics. MOSFETs are increasingly popular in driver transistors these days, and they can be very sensitive to temperature fluctuations if they skimp on the heat sinking—which is another way cheaper products keep the prices down. (You can validate this by spraying Freeze Spray on key components.) I suspect SMT components would be more sensitive yet to temperature fluctuations due to their smaller surface area, but this is just my guess. However, due to their smaller mass they probably win when it comes to vibrational tolerance.

There are interesting videos on YouTube of the Russian vs USA snow crawlers abandoned in Antarctica decades ago. One of the initial problems identified was the use of consumer grade semiconductors vs. military grade in the electronics. Both vibration and temperature were the culprits.

I pulled up the spec sheets for the consumer vs. military versions (both of which you can buy commercially), and you can see the huge, dramatic difference. Even though they are different manufacturers, you get the picture:

 

[Chicken lights]

As usual you guys don’t disappoint.

Looks like a 1000 watt (2000 peak) Magnum inverter is around $6-700 with free shipping, I just haven’t had any more time to dig into it today

I ordered a battery isolator too, I think I’m gonna stop at a truck wreckers Monday and see what I can find for battery hold down brackets and pursue seperating the inverter onto deep cycle batteries

@kevin.decelles do you have a rough battery life on your setup? I’ve gotten in the habit of just changing mine every fall, $200-ish for four new batteries is cheap insurance instead of a $200 boost in January

 

[Susquatch]

When I traded my F250 in for a new F150 two months ago the service guy at Ford told me that inverters have a limited service life due to vibration—but mostly due to temperature swings. Granted, at the time he was plugging the new "Power Onboard" with the F150s, which is an actual generator driven by the drive belt. In my case I have the smallest engine (2.7 EcoBoost) and it generates 2200W to the tailgate. But the largest engine can deliver 7000W, which is enough to drive a welder. There is still an inverter inside the cab which I think has better technology as I can now use my small ink jet on it which the inverter in the old truck didn't like. When the cold weather comes we will see. Reliability in cold months seems to be inversely proportional to complexity of the electronics. Also remember that discrete components and ICs come in different grades. For example, 7400 series TTL (Transistor Transistor Logic) ICs have a narrower operating temperature than the military/hi-end commercial 5400 series. (I think there are newer classes I am unaware of). The same is true of their sensitivity to vibration. Ditto for CMOS (Complementary Metal Oxide Semiconductor) electronics. MOSFETs are increasingly popular in driver transistors these days, and they can be very sensitive to temperature fluctuations if they skimp on the heat sinking—which is another way cheaper products keep the prices down. (You can validate this by spraying Freeze Spray on key components.) I suspect SMT components would be more sensitive yet to temperature fluctuations due to their smaller surface area, but this is just my guess. However, due to their smaller mass they probably win when it comes to vibrational tolerance.

There are interesting videos on YouTube of the Russian vs USA snow crawlers abandoned in Antarctica decades ago. One of the initial problems identified was the use of consumer grade semiconductors vs. military grade in the electronics. Both vibration and temperature were the culprits.

I pulled up the spec sheets for the consumer vs. military versions (both of which you can buy commercially), and you can see the huge, dramatic difference. Even though they are different manufacturers, you get the picture:

View attachment 18085


View attachment 18084

@CalgaryPT is spot on about all that.

I would only add weather resistance. In the early days of electronics in both automotive & military applications, entire circuit boards were encased in potting compound to seal them against moisture and corrosion. That caused its own set of problems and has largely been replaced by sealed enclosures and coated chemically treated circuit boards.

Of course, connectors continue to be a major problem despite huge improvements in sealing and corrosion protection.

I bring this up primarily as reason to beg you not to use those horrible crimp on connectors. A good 95% of vehicle fires are caused by crimp on or wrapped electrical connections. If you do not want to take the time to install proper sealed connectors, then at least solder the connections and use a good shrink wrap that includes a sealer. Please don't do what all the repair places do. Your very life might actually depend on it. I cannot emphasize this enough.

 

[CalgaryPT]

@CalgaryPT is spot on about all that....

I would only add weather resistance. If you do not want to take the time to install proper sealed connectors, then at least solder the connections and use a good shrink wrap that includes a sealer.

Bang on. This hits home. I recall spending hours diagnosing a friend's battery issues, only to have a real mechanic clean up the terminals and solve the issue in 10 mins. Lesson learned.

 

[Chicken lights]

Usually every fall (I’m behind this year) I pull every battery cable off. Using a wire wheel on a die grinder clean every connection. Once it’s all clean, sometimes rinsing stuff down, I’ll reinstall then spray a terminal connection protector on. Again usually I do it when replacing the batteries and it’s all apart but I just replaced batteries 3-5 months ago. It’s time consuming, 4 batteries with probably 12-15 connections. I’m thinking replace the batteries with new anyway this fall, had to get a boost last week which has me concerned

Today was a long busy day I’ll try to learn more this weekend

A buddy went through this same issue with his trucks, replaced all 4 batteries with deep cycles and never looked back. Yet a battery guru will say you want the cold cranking amps from a regular battery for startups not a deep cycle

 

[Susquatch]

Usually every fall (I’m behind this year) I pull every battery cable off. Using a wire wheel on a die grinder clean every connection. Once it’s all clean, sometimes rinsing stuff down, I’ll reinstall then spray a terminal connection protector on. Again usually I do it when replacing the batteries and it’s all apart but I just replaced batteries 3-5 months ago. It’s time consuming, 4 batteries with probably 12-15 connections. I’m thinking replace the batteries with new anyway this fall, had to get a boost last week which has me concerned

Today was a long busy day I’ll try to learn more this weekend

A buddy went through this same issue with his trucks, replaced all 4 batteries with deep cycles and never looked back. Yet a battery guru will say you want the cold cranking amps from a regular battery for startups not a deep cycle

You have to be careful about anecdotal evidence. Just because it worked out ok for your buddy once doesn't mean it will work out for a thousand other trucks the same way.

I don't know what your draw usage really looks like so I can't say which is best. However, I do agree that your battery gurus are correct THE WAY YOU DESCRIBED IT.

Nonetheless, I could easily create other ways of describing the situation that would dictate deep cycle batteries. For example, let's say that you start your truck twice a day. But at night, you shut it down and then run your inverter all night driving various loads. The inverter will draw your battery charge down which cycles the battery deeper than normal. In this case, deep cycle batteries might be preferred.

The difference is simple. Starting the engine is really the only draw on the battery while the engine is running. The alternator supplies all the other current that an engine and other accessories need. Starting currents may be quite high but rarely deep discharge the battery. That usually only happens in very cold weather. So the battery usually only sees shallow discharges and charges. That typical usage dictates a standard battery type.

However, if other battery usage when the engine is not running regularly drain the batteries down to say half their capacity, they get cycled deeply on a regular basis and that usage dictates a deep cycle battery.

The problem is deciding which one to get based on YOUR OWN USAGE. As a rule of thumb, I would say that regular discharging below 65% of charge dictates a deep cycle. You can use a hygrometer to test your state of charge before and after starting. The before number will tell you what your overnight usage was, and the after number will tell you what your starter draw was. You can also use a power meter that is permanently attached to make it easier to check and record your usage each time.

I think you also need to recognize that any amount of deep discharging, even minor amounts, will shorten the life of a standard battery, and any amount of heavy starting current will shorten the life of a deep cycle battery. Mixing the two types of usage is going to hurt battery life - period.

That said, it is possible to setup your system so that your engine is started using regular batteries, and your off engine draws are run off of a set of deep cycle batteries. Isolators can be used so that both get charged when the engine is running.

More food for thought.

 

[Chicken lights]

You have to be careful about anecdotal evidence. Just because it worked out ok for your buddy once doesn't mean it will work out for a thousand other trucks the same way.

I don't know what your draw usage really looks like so I can't say which is best. However, I do agree that your battery gurus are correct THE WAY YOU DESCRIBED IT.

Nonetheless, I could easily create other ways of describing the situation that would dictate deep cycle batteries. For example, let's say that you start your truck twice a day. But at night, you shut it down and then run your inverter all night driving various loads. The inverter will draw your battery charge down which cycles the battery deeper than normal. In this case, deep cycle batteries might be preferred.

The difference is simple. Starting the engine is really the only draw on the battery while the engine is running. The alternator supplies all the other current that an engine and other accessories need. Starting currents may be quite high but rarely deep discharge the battery. That usually only happens in very cold weather. So the battery usually only sees shallow discharges and charges. That typical usage dictates a standard battery type.

However, if other battery usage when the engine is not running regularly drain the batteries down to say half their capacity, they get cycled deeply on a regular basis and that usage dictates a deep cycle battery.

The problem is deciding which one to get based on YOUR OWN USAGE. As a rule of thumb, I would say that regular discharging below 65% of charge dictates a deep cycle. You can use a hygrometer to test your state of charge before and after starting. The before number will tell you what your overnight usage was, and the after number will tell you what your starter draw was. You can also use a power meter that is permanently attached to make it easier to check and record your usage each time.

I think you also need to recognize that any amount of deep discharging, even minor amounts, will shorten the life of a standard battery, and any amount of heavy starting current will shorten the life of a deep cycle battery. Mixing the two types of usage is going to hurt battery life - period.

That said, it is possible to setup your system so that your engine is started using regular batteries, and your off engine draws are run off of a set of deep cycle batteries. Isolators can be used so that both get charged when the engine is running.

More food for thought.

Part of isolating the power inverter side of things, for me, is then it’s easier to diagnose problems.

I’m going to try two deep cycle batteries on an isolator, and probably get four new batteries for the truck side of things. Alternator was new in the spring this year, 2021. I’ll maybe look into RV fridges too but the fridge is new as of the summer 2021. The isolator should be in today but I’m 800 miles from home to even think about starting this project

The truck is wired with 4 gauge wire for the charging circuit, and that’s what we used for the power inverter wiring.

 

[Susquatch]

I never worked on the really big trucks. They are different for sure. The closest I got was a consulting gig to improve manufacturing processes at a truck plant after I retired. Very different for sure. Tractors are completely different again.

 

[Susquatch]

Part of isolating the power inverter side of things, for me, is then it’s easier to diagnose problems.

I’m going to try two deep cycle batteries on an isolator, and probably get four new batteries for the truck side of things. Alternator was new in the spring this year, 2021. I’ll maybe look into RV fridges too but the fridge is new as of the summer 2021. The isolator should be in today but I’m 800 miles from home to even think about starting this project

The truck is wired with 4 gauge wire for the charging circuit, and that’s what we used for the power inverter wiring.

So tell me. How many times do you start your truck per typical day?

Have you ever measured your battery state of charge before your first start of the day? I know your day might mean something different to mine. I also know that you might leave your truck running all night iin the winter sometimes. So I'm asking about state of charge after being shut off for an extended period of time while you sleep.

I'm hoping you won't need to replace batteries so often after you separate the deep cycle and start circuits.

 

[Chicken lights]

So tell me. How many times do you start your truck per typical day?

Have you ever measured your battery state of charge before your first start of the day? I know your day might mean something different to mine. I also know that you might leave your truck running all night iin the winter sometimes. So I'm asking about state of charge after being shut off for an extended period of time while you sleep.

I'm hoping you won't need to replace batteries so often after you separate the deep cycle and start circuits.

I’m gonna say on average 10 starts per day. Probably some days less probably some days a lot higher

No I’ve never measured it, but this truck doesn’t seem to charge as high as my last one. I see a lot more 13-13.5 volts with this truck versus the last truck was consistently 13.5-14 volts.

What’s interesting is with the cobra power inverter I could park on a Friday, leave the fridge on with food in it, fire it back up Sunday and go to work. The Samlex is sketchy for leaving the truck off overnight let alone 2-3 days.