This may be a long read, but it can help others who may experience what we had …

We had left for a trip from Niagara Falls, NY to Orlando, FL this past week.

My son wanted to power his laptop and the other children wanted to watch DVD movies on our DVD home player while we traveled.

So, at the last minute, I grabbed an inverter from the local Wal*Mart. This Black&Decker 400W unit is made by Whistler model PI-400W. Whistler inverters operate on a modified sine wave AC output. In other words, it's a switcher inverter that generates a stair stepping sine wave vs. a smooth spline type of sine wave found in many of the older transformer inverters made a few years back.



Well, I let the wife drive the first few hundred miles on the trip while the inverter was running all of the electronic gadgets. Within the first 50 miles, the cruise control went flaky. At first, the cruise would surge the speed about every 8~9 seconds like a heart beat. Then in another 50 miles, the cruise became non-functional. The wife blames me for not keeping the vehicle well maintained prior to this long 1,100+ mile trip. Therefore she had to do without the cruise control and was to hold a steady foot on the pedal.

Once we arrived into PA, she told me to drive since her foot developed cramps on the pedal.
The inverter has a 40x20mm cooling fan that is on the noisy side. So, I tucked it into the storage opening into the dog-house. This way, I had full access to the unit and could reset it when too many things were running.

When we crossed into WV, the OD started to act funny. The tranny wanted to shift down to a lower gear on the slightest grades of hills. I never had that happen before with this van, even while towing the RV camper through these same mountains two years prior. So, I backed off of the pedal from 65 to 60. This lasted until the WV and VA state line. So, again, I backed off to 55. Within the next 100 miles, I have to back off to 50 to keep the OD working. The OD would pulse in and out of gear at faster speeds while going up any hills or grades. When the NC state line arrived, I knew we were in for a long ride. The OD only stayed in at 40 up the hills and grades. I was now keeping pace with the heavy truckers in the far hill climbing right lane using the 4-ways.

We have some dear friends in Charlotte, but they are attending college down that way and wouldn't have the extended time to really help us out.

The OD finally stopped working and driving in 3rd at 45 was all it would do without any problems. So, I thought, will we need to drive 45 in 3rd all the way to Orlando? Or, would I need to find a repair shop near Charlotte to get us back on the road? Just then, the radio then went out. The headlights to the van pulsed brightly every 8~9 seconds too. The engine seemed like it wanted to turn off as those 8~9 second heartbeats happened. We pulled the van off to the shoulder. The engine no longer ran, so I coasted to a stop. To save on energy, we pulled the plug on the inverter shut off the lights and sat a moment.

I then tried the key off/on three times trick to find any codes. Nothing but "done" showed up.
So, I started the van. Strangely, it ran fine at an idle. So, I proceeded to re-enter the interstate making sure plenty of lane space was available. The van got up to 45 and the OD wanted to kick in. At 50, the OD kicked in, but wouldn't stay if the pedal was pressed a wee little more. So, I drove 50 down hills and 40 up hills. Finally we had come to an exit with food, gas and motels.

We then pulled off, got a bite to eat, gas and debated whether to move forward or let the vacation plans get ruined. So, My son and I pop open the hood, checked the fluids, looked under the van, the gauges read normal, so on we went.

Strangely, the van ran fine at 50 with OD, but it wouldn't stay if the pedal was pressed a wee little more. We stopped at a rest area 200 miles later. The van was still only capable of 50. When we left the rest area, strangely, the van ran fine at 55 with OD.

Strangely, the radio was working again and so was the cruise control.

Now, I got my brain into thinking about the postings here in this forum dealing with the PCM. Many people mentioned that the PCM when cleared will need to "relearn" things about the vehicle's electronics and the sensors. The tranny in this Ram Van is the 46RE. In the 46RE, the E stands for ELECTRONIC. The radio is ELECTRONIC. The Cruise Control is ELECTRONIC. What in the world is messing with these things. I then looked down at the inverter that we had shut off hours ago. BINGO !

After the fourth restart of the van, the OD worked like normal again.

Upon inspection of the Whistler PI-400W inverter, it plugs directly into any of the power-plugs or lighter outlets in the van. These outlets are routed to the fuse panel and the PCM. We now know that a switcher inverter that generates a stair stepping sine wave is REALLY BAD for operation in our Ram Vans.

Our family still needs an inverter for the van. I'm debating on getting a 800W unit that will tie DIRECTLY to the battery with fuses vs. using the power outlets in the van. However, will the battery prevent the modified switcher since wave from impeding into the vehicle's main circuits and the PCM? I'll have to test it out.

 

The problem you were likely running into was from the constant power drain on the system that the inverter was causing. On top of what was was being used to run the van, you now have an inverter adding another 20-30 amp draw on the electrical system. (watts/volts=amps.) Your little inverter has the potential to draw 33 amps at full load. It's possible your engine's electrical systems, including the PCM, were not getting the power they needed to run correctly. Going to an 800 watt inverter is going to double your potential power draw to 66 amps. Nothing is saying you'll use all of that if you continue to run the same devices as this trip you described. In that case, the load will remain the same. The only difference is that the invert will only be working half as hard as the 400 watt one.

 

Also, regarding the modified sine wave. The sine wave has no effect on the primary (12v) circuitry. The sine wave exists only at the power outlets and if it is to cause a problem, it will only cause a problem with whatever is plugged into the inverter.

 

Alloro,

I really don't think there is a problem with the battery draw from the inverter at all. The battery is rated at 1000cca and the altenator is rated at 136amps.

I would relate the problem issues to the newer high energy saving switching inverters that rely to much on microfarads that are a common mode for EMI concerns in PWM inverters.

Pulse width modulated (PWM) inverters are increasingly being used with today's vehicle power systems. The generation of voltage in the PWM frequency range by the inverter, particularly for both the common mode signals, shows the propagation of these frequencies through the input and output leads of the inverter. Even with the "soft-switching" PWM problems still occur.

Three-phase PWM inverters have been wildly used as major power stages for three-phase dc-ac power conversions for many years. One of the side effects of this type of inverters is the switching harmonics generated by the pulse-width modulation (PWM). Many papers were published regarding the harmonics analysis. However, most of them were focusing on the output ac voltages only. In addition, complex mathematics used in the analysis prevents the practical engineers from understanding and using them in the inverter design. There is a simple mathematical method for calculating switching harmonics in the output voltage, as well as the switching harmonics in the dc link. There is a relationship between the harmonic spectrum and the mathematic equation associated with individual harmonic components.

So the inverter problem my vehicle experienced is based on the pulse problems from the inverter and the EMI field generated. The pulse problem is mentioned many times in my original posting averaging 8~9 seconds in the harmonic build up. What really is needed is an active common-mode EMI filter for the PWM inverter.

 

I have to agree with Alloro on this, and you pointed to part of the cause yourself. You needed to reset the inverter often because you were drawing too much from it. It was indicating a problem, but you were not paying attention to it.

Some things to note, the Cigareette lighter plug circuit is only designed for a load of 10 amps. the manual should have recomended for any load greater than 100 watts that the inverter should have been connected by fused wires directly to the battery. 100 watts is not much. a laptop draws about 90 continous, but may have a greater startup cost.

The CCA of the battery in no way affects the ability of a battery to handle a constant high level of load that an Inverter will put on your system. As batteries age, the ability to handle a large constant drain diminishes.
I have killed batteries with inverters and ham gear several times.

Also there is some misnomer about how much current the Alternator/Generator produces. The 136A rating is I think at a higher than normal RPM. As the RPM decreases, the amount of current generated (and thus watts) decreases. Watts are units of power and are useful when looking at the capacity of a system. An example is that my 65A altanator is really only generating about 30a at 2000 RPM.

At best and this varies from inverter to inverter, the inverter is about 85% efficient at converting from DC to AC. the rest turns into heat, thus the need for that loud fan you complain about. As the device gets hot, it becomes less efficient.

Try this, take note about where the the RPM of the van hangs when you are in OD, tahe take it to advance Auto, have them hook up their marchine, and check the alternator output at *THAT* RPM. Next you need to multiply the Amps rating from above by 12v to get your wattage output. Then figure out that you have two 55w headlamps running, and the watt loads of the rest of the car electronics. You will then have a better idea of your system usage.

Then as allero said you have to look at the load the inverter adds to that 10A circuit your battery is on. You may also want to consider using some filter caps, because if it is a cheap inverter and not filtered properly, it could be backfeeding noise into the circuit it is on. Directly connecting (with fuses) to the battery will limit that, but filtering anyway wont hurt.

My suggestions, have your son run less electronics at once, get more efficient electronics when you buy them and put that thing on the battery. You may want to not get the walmart made in tow-dung provence model, but instead get one that the owners manual isn't a fire and forget engrish item.

All of this is why I'm looking at putting in a second 65A alternator to power the inverter and my ham gear on a dedicated basis, the same can be done with a second battery preferably a marine deep cycle and an Isolator. hook Your inverter and electronics up to that.

 

IGadget,

I can see your point of the load demand vs. the energy stored in the battery and how the altenator at a given rpm outputs less juice than at the maximum rating. The 1000cca battery in my van has only 15 plates. It's a HD type vs the other 1000cca that have 21 plates. Sure ther are otherplus and minusesfor the number of plates, but I wouldn't go into that here.

Your 65A alternator wouldn't do beans in my 2001 Ram Van. The later 2nd generation Ram Vans got the 136A alternator as standard equipment.

My HAM gear, HTX-242 2-meter radio (Less than 8A at 45W on high power), and cell phone charger never took the battery down nor the PCM like this inverter did. In fact, there were plenty of times the inverter ran on the trip with nothing pulling juice from it. It was left on so that I could focus on driving and the boys could use it when needed.

My son's laptop only pulled a mere 75W of power and the DVD player pulled 35W of power. That was a small load of 110W overall being used at any given time. The mp3 player only pulled a little 1.5W max if that was tossed in too.

The headlights didn't come on until the early evening time. When we set out, the cruise control at 8am was doing the 8~9 second pulse after the inverter was turned on for just the 35W DVD player. No headlights nor other accessories were being used at that time.

Early this summer, I borrowed a friend's 650W inverter that conected directly to the battery. It ran a 375W crockpot and the 35W DVD player for 4 hours without any issues. That's a total of 410W plus the radio and headlights as we drove out to M!CH!GAN. So, over loading the battery and altenator this past trip should have never been an issue. [&:]

 

There is another possibility for what's going on here. Perhaps your battery, alternator or regulator is on the Verge of giving out. The use of the inverter might have tipped the scales enough to show you a problem is looming.

 

Alloro,

After the trip this past week, I hadchecked the battery with my advanced charger and meters. It passed all of those tests. The alternator passed the testing too at AutoZone.

 

Stev,

As you are a ham radio operator you know way more than me about efi and rfi. One thing I might be able to add to this thread is that I have a battery monitor in my van that will show alternator amperage.I find this to be a real informative tool, figuring out how much each device draws, and how much juice the alternator is making at a certain battery level and load.

One thing that has surprised me is how quickly the voltage regulatorinside my '89 s ECM Smec reacts to load. If I'm idling, and the batteries were at about 90% when started, about 5 minutes after starting the meter will read 13.7 volts and show a net output of +2.5 amps at idle. If I turn on the lights, inverter running a 5 amp fan, computer, the 2.7 amp dc fridge, and every load I can inside the van, the numbers on the meter barely flicker. Same voltage, same net + amperage at idle.@ ~ 3000rpm, +.1 amps + .2 volts. I've got a reman autolite 130 amp dual pulley alternator.

Granted this is when 3 brand newnearly full Batteries are connected together in parallel, acting as a big filter. Maybee with them at 60% dod thealternator's output would respond differently on my meter. Even in my haynes manual in checking the charging system it says when switching on the lights, the voltage should lower, then rise back up as the alternator responds to load. On a solar forum I frequent one guy said the gauge cable between the alternator and battery have a big effect on the quickness of the response of the VR.

As you said, I don't think you have a problem with your charging system, but putting on some thicker wires from the alternator couldn't hurt.

 

Stev,

I think the key here is that you were running your frineds 650w off of the battery and the 300w was though the Cig Lighter. That cig lighter circuit is only rated 10A. So 75w and 35w = 110w That is right at the edge of the fuse, and I'm not sure if they changed it for the Gen2 vans, but that circuit also has the markers and dash lights on it which as you say are ot coming into play until later.

I think all of your problems will be solved by 1) connecting directly to the battery and 2) getting a better quality inverter. Dont forget that 'at best' the inverter will be 85% effecient, though there are some higher rated models out, they are unlikely to be found at Walmart where I think you said this beastie came from.

The battery connection also has the benefit that any back feeding on the circuit will be cushioned by the battery. You can check if there is anything leaking back from the inverter by measureing AC voltage between the cig ground and chassis ground with the inverter and load connected. Most meters are not sensitive enough to notice AC hum on a DC line otherwise. I used to check PC supplies for this since it was an indication of impending failure.