house bank merge solenoid

[David Anderson]

Hey guys,

I just returned from a 3000 mile Colorado trip in the Eagle 10 on Tuesday.  In the last leg home I switched on the heavy duty solenoid to merge my 12volt bank with the Niehoff 300 amp alternator to run one Coleman rooftop off the SW 2512 inverter.  The AC ran fine for about 2 hours with the inverter showing 13.1 volts being pumped into the bank from the alternator.

After 2 hours I disconnected the banks, fired the genny and ran all three rooftops.  Withing 20 minutes my bus alternator gauge began jumping from 14 volts to about 12, very erratically.  Strange, never done that before.  The house bank voltmeter jiggled at the same time.  After a few minutes it went back to normal.

Today, (Thursday) I took the bus out and tried to merge the batteries and there was no voltage change.  I stopped the coach and checked the solenoid switch and the 300 amp safety fuse was blown between the alternator and solenoid.  I installed a new fuse and attempted to hook up the start batteries  and sparks went flying.  Fortunately, I didn't blow the new fuse.

I disassembled the solenoid and the contacts were melted, pitted, and basically toast inside the solenoid body.  That shouldn't have happened.  I bought this from Wrico, and IIRC the switch is rated for 300 amps @ 12volts.  The AC is 120v X 16 amps =1920watts.  1920/12 volts = 160 dc amps X 1.1 (inverter innefficiency) =176 amps load

I wonder why this thing blew up??  $160 down the drain.  I like the convenience of merging from the cockpit, but I wonder if I should consider a manual switch instead. 

Any ideas as to what happened?  No other loads were on while I did this.

Subject change:  Fuel for the trip.
I fueled up in Dumas TX (up and back) at Walmart $2.92/gal with the gift card.  South Fork CO. $3.15/ gal.  Pleasanton TX HEB Food store $2.74/gal

David

[Jeremy]

Given the high currents flowing through this circuit (and associated safety issues), it might be advisable to get a professional to have a look if components are failing unexpectedly.

Assuming that the solenoid is actually rated at 300A continuous (rather than 300A Max), two things that might cause the high current draw might be either the AC cycling on and off too much (so frequently pulling a very high start-up current), or possibly a loose or dirty connection somewhere causing extra resistance and/or spikes on the circuit

Jeremy

[TomC]

When I bought my inverter, the gal who sold me was very informed about them.  I asked her about stacking so I could get 5,000 watts and then run one or two roof tops with it.  She asked if I had a Diesel gen, when I said I had a 10kw, she said just to run the gen for the A/C use.  So instead of me buying two from her, I bought just one-from her suggestion!  Personally, I think of the inverter as a standby, intermittant electrical source for like a coffee maker, microwave, water heater, bath heater, power a drill, etc.  And you'll notice most all are just resistance loads and all do not have any significant start up loads.  I realize that you can use them for primary power, but the efficency loss is big as compared to just running the gen.  And besides, if the alternator on the bus engine is providing the power for the A/C, you'll be burning just as much fuel as running the gen from the efficiency differences.  I have a home made cross over solenoid that is two 160amp continuous duty solenoids (looks like the old Ford starting solenoids) strapped together in parallel.  I have left it on for weeks when hooked up (mistakenly), started my bus on the deep cycles (all that current going through the solenoids), and they still work fine today.  Sometimes the simplest works longest.  Just a suggestion to use the gen for A/C always, then that big power surge everytime the compressor kicks on will be absorbed by the gen rather than the inverter having to spike to get the compressor moving.  Good Luck, TomC

[Len Silva]

David,

One consideration is that your solenoids may be rated to carry 300 amps but may not be rated to switch that load.  Another is that if there were a large disparity in the state of charge of the two battery systems, that might result in a large inrush current.
Just speculation from here FWIW

Len

[David Anderson]

Tom,

I tend to agree with your assessment about running the AC's off the genny instead of trying to sneak one off the inverter.  Dick Wright was confident this solenoid would survive the continuous load as stated, however something is awry.  I've read numerous posts about successfully running one AC off an inverter.   Mine wasn't so successful.  Perhaps those with success had a different switching system. 

I never merge the system when the genny is powering the inverter.  The charge voltages from the powered inverter always gave me goofy readings on the bus voltmeter.  Since the bus volt meter was acting strange in my original descriptive post, it was because the solenoid contacts had fused together allowing current to flow to the alternator from the inverter charger.  The Niehoff didn't like that at all.

I've thought about the idea of two 160's in parallel.  Probably much cheaper, you think?  That may be a better answer.

David

[DuaneMC7]

I had a similar situation a while back. In my case I had asked for a 200 amp continuous duty solenoid to have manual control over the house bank being fed by the alternator. After it burned up in a very short time I found out it was not a continuous duty solenoid. I am having a hard time finding a high amp continuous duty solenoid and had to settle for a 120 amp. So far so good. 

Duane   

[H3Jim]

David, I'd also call Dick wright and talk to him about it.  He stands by his product pretty well. 

[Stan]

David: snip  "Since the bus volt meter was acting strange in my original descriptive post, it was because the solenoid contacts had fused together allowing current to flow to the alternator from the inverter charger.  The Niehoff didn't like that at all."  snip

If I understand this correctly, you are saying that if you feed the output from you house battery charger to the engine charging system it makes your engine alternator act up and the  engine volt meter act strange.

That should not happen if everything in the engine charging system is working properly. The engine voltage regulator would just see the higher voltage from the charger and shut down the engine alternator. If all the diodes in the alternator are good there would be no backflow into the alternator and the voltmeter should read the charger output. If the charger output was lower than the engine voltage regulator, the opposite would happen.

Since I never had this happen or heard the problem discussed previously, this is all theory any I may be missing something.

[pvcces]

David, I still think you have something messed up that you haven't found, yet.

Aside of that, if you are interested in something a little simpler and less expensive, and you still have your starter safety relay, you can take a signal off of that relay to turn on your tie in relay or relays.

If you check out the Pathmaker battery combiner by Heart, you will find out that they just ganged relays together to reach a high enough rating. You can buy continuous duty relays of 100 amps or more from quite a few sources.

The main advantage of the Pathmaker is that the combining voltage settings are adjustable and there is a high voltage cutout adjustment, as well. It will remember to disconnect when you forget to. It also has manual override features.

Here is a link: http://store.wmjmarine.com/-c13743.html

Good Luck.

Tom Caffrey
Suncatcher
Ketchikan, Alaska

[David Anderson]

Stan,

The contact ring and the contact posts in the solenoid were really burned.  The ring was stuck against the posts without energizing the the coil, but not tight enough to take the current, so charging from the inverter was probably at best interrmittent causing the Niehoff voltage regulator to get all kinds of wierd currents. 

That's just my take on it.

I'll call Dick next week to see what he thinks.

David

[RTS/Daytona]

Continous Duty - good prices

http://texasindustrialelectric.com/relays.asp

look for silver contacts

[belfert]

If you check out the Pathmaker battery combiner by Heart, you will find out that they just ganged relays together to reach a high enough rating. You can buy continuous duty relays of 100 amps or more from quite a few sources.

The main advantage of the Pathmaker is that the combining voltage settings are adjustable and there is a high voltage cutout adjustment, as well. It will remember to disconnect when you forget to. It also has manual override features.

I ended up buying a Pathmaker for a good price on Ebay.  I wanted to do a battery combiner/seperator from Sure Power, but I couldn't find the model I wanted sold anywhere and finally found out is was around $400!

Brian Elfert

[David Anderson]

Thanks, RTS

Very, very helpful.

David

[David Anderson]

I misspoke on the rating.  The solenoid was rated for 200 amps, not 300.  Anyway, I talked to Dick Wright this morning and he said he has quit recommending continous duty solenoids for merging the banks.  He has seen several failures and recommends a battery isolater $399 each.  Pricey, but more dependable.  Anyone use that instead?  How has it worked for you?

David

[H3Jim]

I bought one of Dick's isolators several years ago and so far it has worked flawlessly.  Exactly as advertised and as I'd want it to.  I only have one roof air hooked up so far, but I can run it while going down the road.  Whenever I arrive anywhere, my house bats are always charged up.  No issues with the bus batteries either, they are always charged, and not overcharged. The Bus alt charges my house batteries that run my 4000 watt inverter that runs the air.  electrically it runs fine. 

All I did was remove the wire from the alt that went to the starter and attached it to the isolator. Ran a big wire from the isolator to the starter, and another big wire from the isolator to the house batteries.  The bus regulator works from the bus bats, so it automatically compensated for the approx 1 volt loss of the isolator.