Ram Promaster Forum banner

1 - 20 of 44 Posts

·
Registered
Joined
·
235 Posts
Discussion Starter #1
I've had problems with my inverter, and I recently replaced it, upgrading it from 1500W to 2000W. Once I replaced it, the problems went away, so I felt confident that I'd been right that the problem was with that component instead of some other part of the wiring. But... A few days ago, the inverter lit on fire.

When this happened, there was also a lick of flame on a grounding cable, connecting the bus bar for all the negative wires to the shunt (which is needed for the battery monitor).

The inverter is on a fuse, but bizarrely, it didn't blow.

I'm trying to figure out if this was a bad inverter, or whether there could possibly be some other problem with the system. Any thoughts on what might have caused this?

(To tell the fuller story of this... When I saw small flames from the inverter, I hollered for my husband to get the fire extinguisher. He sprayed it, but then there were horrible, caustic fumes. We grabbed our cat, who travels with us, and stood outside while it aired out. When we went back in, I realized why the fumes were so caustic: He had grabbed the bear spray, not the fire extinguisher.)
 

·
Registered
Joined
·
418 Posts
Luckily not a flammable variety of bear spray, I take it. Water based sprays are also not a good answer to electrical fires.

If you're looking for help in diagnosis, a lot more (all devices in use, wire sizes, fuse sizes, additional connectors and components, connection diagram, ect) information is is required.

Electrical fires are most often caused by prolonged overheating and melting if not a spark into a different flammable source. Oversized fuses will not protect undersized wires or connection points. Most devices aren't comprised of easily flammable materials, so mostly smoke and maybe brief flame from dust or oils is the more common burning scenario rather than open flame.
 

·
Premium Member
Joined
·
8,714 Posts
That inverter can draw more than 2000 watts I bet, and when it draws 2000+ watts it is pulling close to 200 amps. That is as much as the main breakers in a home are rated for! In my conservative electrical minded van building I got scared when I began considering that current and limited myself to an 1100 watt inverter. Even then the current is 100 amps and really large wire and proper fuses are required. If we are going to build an electrical system that uses such current it might be time to look at 48 volts. 2000 watts @ 48 volts is just over 40 amps a much easier current to plan for.
 
  • Like
Reactions: Hein

·
Registered
Joined
·
2,000 Posts
That inverter can draw more than 2000 watts I bet, and when it draws 2000+ watts it is pulling close to 200 amps. That is as much as the main breakers in a home are rated for! In my conservative electrical minded van building I got scared when I began considering that current and limited myself to an 1100 watt inverter. Even then the current is 100 amps and really large wire and proper fuses are required. If we are going to build an electrical system that uses such current it might be time to look at 48 volts. 2000 watts @ 48 volts is just over 40 amps a much easier current to plan for.
For the 2,000-Watt version of Ford’s Pro Power Onboard on 2021 F-150, Ford bumped voltage up to 24V for the stand-alone electrical system. My guess is that they would have used 48V like on larger lithium-battery-based Pro Power Onboard, but on base system they would have needed 4 X 12V AGM batteries, which is more than the two batteries the system includes.

I personally think 48V is the future and wouldn’t bother with 24V middle ground, but understand why Ford did it. Regardless, the point is that Ford engineering determined that 12V electrical architecture was less than ideal for a 2,000-Watt inverter. It can be done, but as a stand-alone system it’s not the best option.

Unfortunately, most RVs do not have a stand-alone secondary electrical system, so it’s better to stick with 12V so they can charge from standard alternator.
 

·
Premium Member
Joined
·
417 Posts
Glad things didn't turn out very badly.

RD is correct that larger (over 1000 watts) inverters can draw a lot of current on the DC side. What size fuse and cables were feeding the inverter? What was the load on the inverter when the fire started? Can you post some photos of the wiring before/after?

Thanks for posting as this is a valuable lesson for those with large inverters with insufficient fusing and cables. Another issue is the heat that is produced when running large loads. Adequate ventilation is important. Mounting electrical equipment on wood is also not good.

All the best,
Hein
DIYvan
 

·
Registered
Joined
·
235 Posts
Discussion Starter #7
That inverter can draw more than 2000 watts I bet, and when it draws 2000+ watts it is pulling close to 200 amps. That is as much as the main breakers in a home are rated for! In my conservative electrical minded van building I got scared when I began considering that current and limited myself to an 1100 watt inverter. Even then the current is 100 amps and really large wire and proper fuses are required. If we are going to build an electrical system that uses such current it might be time to look at 48 volts. 2000 watts @ 48 volts is just over 40 amps a much easier current to plan for.
That's a good point.

I'm attaching a diagram of system, though it doesn't include everything -- just the stuff that's directly relevant to the inverter. The system also has a solar controller for the PV, a battery isolator, a battery monitor, and additional loads. Sorry my handwriting is awful. I wired the shunt the way the battery monitor manufacturer stipulated.
IMG_5385-1.JPG


The inverter came with the cables to and from the battery and the fuse, so presumably that wire is adequate.

I have a bank of five batteries, connected with short 2-gauge wires. According to this Automotive Wire Amperage Capacity Chart - Jasco Automotive Ltd, I can have 7.4 feet of 2-gauge wire carrying 200 amps with less than a 2% voltage drop. The wires connecting the batteries are each about a foot long, so I'm under that.

However, the grounding cable that overheated was an 8-inch stretch doubled 6-gauge, so effectively 3-gauge. That cable runs between the bus bar and the shunt, and the shunt is grounded to the van chassis with about a two-foot length of 2-gauge. The cable back to the negative pole to the battery is also doubled 6-gauge, about 18 inches.

Thoughts? Certainly one step I could take is to replace the two sections of doubled 6-gauge wire with 2-gauge, but I'm not sure whether that could explain the fire.
 

·
Premium Member
Joined
·
417 Posts
It is likely that the load is not equal in both strands of 6 gauge. What were you running off the inverter when the cable melted?

Even 2 gauge is smallish for your loads. 2000/12=167A but due to voltage drop and inverter losses you could be at 200A. 2 gauge is rated for about 180A ampacity. As soon as the wire gets warm/hot the resistance increases; which causes current to rise even more. This leads to a runaway condition that only gets worse and likely resulted in the fire.

A 2000 watt inverter should probably be wired with 2/0 to be on the safe side. And one should closely monitor the current on the DC side while running large loads on an inverter.

All the best,
Hein
DIYvan
 

·
Registered
Joined
·
235 Posts
Discussion Starter #9
I was running an external computer monitor plus a 700-watt microwave. I don't know what the monitor draws, but it seems to be significant.

The cables the 2000-watt inverter came with are 2-gauge, fwiw.

If I replace the doubled 6-gauge with 2-gauge and use a 1500 watt inverter, does that seem like it will make things safe?
 

·
Premium Member
Joined
·
1,002 Posts
How are your crimps? Professionally made? DIY with a hand-crimper? Is the inverter toast? What's the rating of the fuse for your inverter?

I'm not an expert, but maybe there was an internal failure (short?) in the inverter that drew lots of current (explains the inverter expelling flames) but not enough to trip the fuse. And then poor quality crimps at the shunt caused an overheating condition (perhaps explaining the flame there).

My cheapo microwave rated at 700W actually draws a tad over 1000W. And with (I'm guessing) inverter inefficiencies, it triggers a 100A draw on my battery bank.

Depending on the age and size of your monitor, it could draw up to 100 to 200W (I've looked at the sticker on my older LCD monitors [I'm assuming you don't have a huge old CRT monitor] and they say say they draw 1 to 2 A at 120-240V), so up to 20A at 12V. Newer monitors would draw less (my newest one draws only 1.58A at 19V, so call it 3A from my battery bank)

So you could be drawing 120A perhaps.

At my battery bank (soon to be 3 x 100Ah), I have a 250A circuit breaker. And if your fuse is similarly large it wouldn't blow either (I presume). And theoretically, even a single AWG 6 cable 8 inches long might be able to handle it. But despite you doubling it, a poor quality crimp or connection and an AWG 6 cable becomes much "thinner" at the crimp/connection. (Ask me how I know... o_O )

That crimp/connection could easily overheat and cause a fire.
 

·
Registered
Joined
·
2,000 Posts
When sizing wires/cables, I’d look at both voltage drop and ampacity limitations, and then use the larger wire/cable size of the two.

Voltage drop alone when wires are short isn’t enough because it doesn’t address heat dissipation.
 

·
Registered
Joined
·
235 Posts
Discussion Starter #12
Thanks, all. The crimps are DIY. I'll double check them. I'll look at the fuse size too -- it's whatever the manufacturer of the inverter sent.

I've been going over everything, looking for something that might be wrong, and I noticed that the screw connecting the grounding cable to the van chassis isn't fully tight. I can't move it at all, and it looks like the wire is making a good connection to the van chassis -- but could that be the problem anyway? I'd just tighten the **** out of it, but it's very hard to reach. Here's a pic.
 

Attachments

·
Registered
Joined
·
2,000 Posts
I was running an external computer monitor plus a 700-watt microwave. I don't know what the monitor draws, but it seems to be significant.

The cables the 2000-watt inverter came with are 2-gauge, fwiw.

If I replace the doubled 6-gauge with 2-gauge and use a 1500 watt inverter, does that seem like it will make things safe?
Using a slightly smaller inverter in itself won’t make much difference if the loads are the same. If anything, it may make matters worse because maximum inverter efficiency is often around +/- 30% of rated capacity. And if you run microwave (1,000~1,100 Watts of electricity) plus other smaller loads, you’ll already be well over 30% of 2,000-Watt inverter. Of course, you must evaluate each inverter separately because there can be significant variations in efficiency. That assumes they both still work.
 

·
Registered
Joined
·
235 Posts
Discussion Starter #14
I'm in the market for a new inverter. Using a 1500-watt will at least prevent larger loads. My husband is not very savvy about thinking about such things.

What exactly is inverter efficiency? You mean, when you're above 30% of the rated load, it will use extra power to meet the load?

The load I had on the inverter when it lit on fire was definitely within the capacity of the 1500-watt one.
 

·
Registered
2014 136” HR
Joined
·
4,822 Posts
Could you tell us which inverter this is?

I'm really glad to know that bear spray puts out fires and that you and van are ultimately safe.
 

·
Registered
Joined
·
235 Posts
Discussion Starter #17
It's a Krieger.

I would not recommend bear spray as a fire retardant. :) The fire went out on its own, once I turned it off from the back. I'm just glad the bear spray wasn't flammable!

It hadn't occurred to me that I might be able to use the 2000-watt inverter that burned and got bear-sprayed. Do you think that might be OK?

BTW, I had two problems with the original, 1500-watt inverter (also a Krieger). One was that sometimes, when you first turned it on, it immediately squealed and shut off. If you turned it on again, it was OK. It did that almost from the beginning. The other was that on high loads, it shut off even when the voltage was just fine.
 

·
Premium Member
Joined
·
1,002 Posts
DIY crimping is ok. But it's important how. I did mine myself, but I'm not that strong and so instead of a hand-crimper (or as I've cringingly watched YouTubers use, a pair of pliers...), for larger gauge wires, I used a hammer crimper with a 3 lb sledgehammer. I took no chances and smashed it like I was killing something. :D

Re: inverters. That squealing is your inverter overloading. When testing my smaller backup inverter with a blow dryer on high, it did the same thing; squealed and shutdown. (My big inverter could handle it.)

In my opinion, it's better to never come close to the rating of inverter when your loads are maxed out. You need room for a higher-than-advertised surge whenever you start something. e.g. for things with motors, startup surge current can be much larger than what's on a device's label. So if you're running 1000+ W loads, I'm not sure about using only a 1500W inverter unless they are overbuilt; some can provide their claimed current and some specs are inflated. And then there's the surge factor.

Re: your flamed out 2000W inverter. I'm not sure it should be reused. It needs investigation at the very least. What if it fails again when you're out on the road, perhaps at a remote location?
 

·
Registered
Joined
·
235 Posts
Discussion Starter #19
Yes, but my inverter was squealing when I first turned it on and there was zero load. The squealing should happen when the voltage gets too low, but it was doing so when the voltage was just fine, well above 12.

That hammer crimper is great -- I hadn't seen that before.
 

·
Registered
Joined
·
380 Posts
Thanks, all. The crimps are DIY. I'll double check them. I'll look at the fuse size too -- it's whatever the manufacturer of the inverter sent.

I've been going over everything, looking for something that might be wrong, and I noticed that the screw connecting the grounding cable to the van chassis isn't fully tight. I can't move it at all, and it looks like the wire is making a good connection to the van chassis -- but could that be the problem anyway? I'd just tighten the **** out of it, but it's very hard to reach. Here's a pic.
What is the cable attached with, a rivnut?
 
1 - 20 of 44 Posts
Top