Yet another solenoid bites the dust! - Page 4

porscheracer · 07-11-2008, 08:19 PM

Great idea! Thanks, Harry (and John).

cbeierl · 07-29-2008, 07:05 PM

Well, our second bridging solenoid just failed at some point in our 4wk/9500mi trip. Not sure just when during the trip, since the generator was running much of the time to provide A/C and was therefore keeping the house batteries charged. I noticed it the day before we got home. Before I replace it with the new one I just got is there a consensus on the specs of the recommended diodes and/or resistors to add in series with the coil lead? MrTransistor?

Any help would be appreciated.

Thanks.

SCVJeff · 07-29-2008, 07:16 PM

These are the DIODES I have for the install. More than needed but look at the $$!

cbeierl · 07-29-2008, 07:27 PM

If I'm understanding this correctly there's an approximate 0.3V forward voltage drop in each diode, so four of them in series would give a drop of 1.2V--does that sound correct?

Do these diodes look suitable as well? 6A/50V Rectifier Diodes

On edit, I guess a germanium diode would have a 0.3V to 0.4V forward voltage drop while silicon would be 0.6V to 0.8V, giving a total drop of about 2.4V for four in series. I'm assuming that the above diodes are silicon--can somebody confirm that?

SCVJeff · 07-29-2008, 08:00 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by cbeierl:
If I'm understanding this correctly there's an approximate 0.3V forward voltage drop in each diode, so four of them in series would give a drop of 1.2V--does that sound correct?

Do these diodes look suitable as well? 6A/50V Rectifier Diodes

On edit, I guess a germanium diode would have a 0.3V to 0.4V forward voltage drop while silicon would be 0.6V to 0.8V, giving a total drop of about 2.4V for four in series. I'm assuming that the above diodes are silicon--can somebody confirm that? </div></BLOCKQUOTE>It's .6 drop across each device. I have no idea what it might be, but it's possible that the back EMF of that coil being shut down might cream a junction. That's why I went for the beefy ones @ $.50ea.

MrTransistor · 07-29-2008, 08:57 PM

Hi Chris,

Sorry for the delay, sometimes I go for days without checking the posts.

I would definitely go with the contactor with silvered contacts. The copper contacts just don't provide the consistently low resistance required in a bridging application. Unless you are prepared to open the device to clean the contacts when they fail to provide this low resistance.

As far as the heat in the coil, a 2 or 2.5 ohm resistor of 15 or 20 watts will work just fine. If you chose to use diodes, 3 silicon diodes would provide about 1.8 to 2.4 volts drop depending on the device. Counter EMF (back voltage when the device is turned off) could be quite high given the iron core and number of turns of wire in the contactor. An 800 or 1000 volt rating for the diodes should be more than enough.

You could use much lower voltage ratings for the diodes if one more diode is added across the coil as a counter EMF shunt. i.e. Install the diode with the anode to the ground lead and the cathode to the +12 volt side right at the contactor. Then when voltage is removed, the counter voltage briefly forward biases this diode and shunts the current preventing the high potential that can arc contacts and destroy diodes.

Use diodes with about a 2 Amp. continuious rating and all should be well. The diodes that Jeff proposes should work just fine. The 50 PIV devices probably won't unless the counter EMF diode is also added.

I'll check the Trombetta web site to see if any change in the coil of the contactor has been made recently.

Nope, no change!

Good luck!

cbeierl · 07-30-2008, 03:06 AM

Thanks, Jeff and Mark!

SCVJeff · 07-30-2008, 04:26 PM

I'm sure Mark has been here too, but if you get across that coil, the back EMF will definitely knock you back in your chair enough that you won't do it a 2nd time...

cbeierl · 08-25-2008, 07:03 PM

Well, I just replaced my failed solenoid/contactor with one with the silver contacts. I added a couple of 1-Ohm / 10W Wirewound Resistors in series with the coil. Hopefully the third time's the charm and I won't have to replace it again.

rnabors · 08-26-2008, 06:12 AM

For a less experienced guy with electronics can you explain how and where you place the resistors.
Thanks

John_Canfield · 08-26-2008, 08:30 AM

The resistor(s) is(are) placed in series with either the positive or negative of the coil terminal post. The coil terminal posts are the smaller ones. The large studs are the contacts of the solenoid

rnabors · 08-26-2008, 11:54 AM

Thanks John--I put the resistors in this afternoon that cbeierl suggested. The solenoid is a lot cooler but the resistors are hot---guess that is what they are supposed to do huh.

John_Canfield · 08-26-2008, 12:25 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rnabors:
Thanks John--I put the resistors in this afternoon that cbeierl suggested. The solenoid is a lot cooler but the resistors are hot---guess that is what they are supposed to do huh. </div></BLOCKQUOTE>Exactly - the resistors are dropping voltage across them and that is expressed in heat - just like a traditional filament light bulb gets hot.

cbeierl · 08-26-2008, 05:18 PM

Here's a picture of how I installed the resistors with my new solenoid/contactor:

The metal bracket was just a piece of scrap I had around--it provides a rigid mounting and strain relief for the resistors and serves as a heat sink as well. It's held by one of the same mounting bolts used for the solenoid. I used some small copper wire to secure the resistors mechanically to the bracket.

NoMoreAZ · 10-22-2008, 06:55 AM

Having been recently inducted into the FOTWADCCB (Fraternal Order of Those Who's Alternator Doesn't Charge the Coach Batteries), I will pass on the details of the fix I performed on our unit.

Problem Discovery:

We travel with the refrigerator on; hence the inverter (Xantrex RS2000) runs. Somewhere in the Yukon or northern BC, on the way south, the charge on the coach batteries was falling into the 70 to low 80% range. Voltages for the 'House' and 'Engine' battery display on the One-Place panel were not the same, +/- a little, as they should be while traveling. We have 400 watts of solar on the roof and a XBM (Xantrex Battery Monitor). The XBM tells us the percentage charge in the battery bank as well as many other useful items. Having read various threads on this forum about the battery isolator and its less than sterling performance, I said "Aha, I know what that is".

Until we could park for a while, we traveled with the refrigerator off and the inverter in 'Hibernate' mode. The solar system, even on cloudy days, could now keep the coach batteries at or very near 100%.

Repair:

I purchased a new Trombetta contactor (relay) P/N <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> 114-1211-020 (silver contacts),

http://www.trombetta.com/dc-contactor-products.cfm?id=8

http://shopping.murcal.com/Welcome
</div></BLOCKQUOTE> This has the exact same form factor as the Trombetta contactor used by 'Bago. The only difference is the contact material. To drop the voltage to the coil to somewhere around 12 VDC I used three diodes <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> These are the DIODES I have for the install. More than needed but look at the $$!

_______________________________
Jeff - WA6EQU
</div></BLOCKQUOTE>in series. At a 0.7 VDC drop for each silicon diode, 2.1 VDC is now 'removed' from the contactor coil. I also installed one of these diodes across the coil 'backwards', i.e. cathode to +12 VDC and anode to 0 VDC to protect the coil on shutdown (aka back EMF). All exposed leads have heat shrink tubing where needed. All connections to contactor terminals were done with fully insulated quick disconnects.

Testing:

Initial test after repair showed both voltage displays on the One-Place panel to be the same. We have driven about 900 miles since the repair, with long and short driving days and long and short down periods in between. Coach batteries stay at 100% while traveling, but may drop to 98.6 or so when engine is shut off while fueling or shopping for a while. Refrigerator is switched on the entire time. Solar does its job when engine is off.

Dissection of Old Contactor:

Based on what I have read in this thread, I expected to see a contactor assembly with burnt contacts. I did not see this on my old contactor. There were just small points of discoloration, no pitting. The contacts could have been easily cleaned with a burnishing blade .The coil was dark brown, some of that color due to the installed varnish on the wire. I did not measure the coil's resistance, or lack thereof. There is a nylon washer and a phenolic washer or spacer on the shaft that travels in and out of the coil. Both of these were very brittle and broke. I may have contributed to the breakage removing the coil from its canister, but I believe the damage was already done. The conclusion could be that either the broken washer or spacer limited shaft travel or the coil was defective. As in so many instances with electronic or electrical components, heat is the worst enemy.

So, for the moment, to quote Wm. Shakespeare, "All's Well That Ends Well". But, since Murphy rides with us, I have a spare set of everything!

John_Canfield · 10-22-2008, 08:40 AM

Welcome to our not-so-exclusive club

. However, in order to attain the next level of membership, you must have more than one failure which you probably have avoided with your upgrade.

Well done write-up.

Winnie engineering maintains the particular Trombetta solenoid supplied is appropriate for this application, but one has to wonder

Only Winnie has the hard data on failure rates per x number of parts and the Trombetta product failure rate might be within Winnie specs. We'll probably never know.

Ready2Travel · 11-07-2008, 02:09 PM

It's been a few weeks since this thread has had any posts so thought I'd revive it and share my recent experience and ask a few questions.

Had the house batteries not charging when driving on the first and only trip I've made since replacing the house batteries. As with others they charge fine on shore or generator power. The trip I made was 500 miles in one day and when I noticed the problem I started the generator and ran it a few times to keep the batteries charged until I got to my destination. Have been reading this thread and a few others since having this problem and until today have not had a chance or good enough weather to check it out. (Raining here in Oregon can you believe it?)

Today I found the two solenoids thanks to posters here and first I checked out the two fuses on the outboard one, they were OK. Then I started up the engine to see if I was getting 12 volts to the two small terminals that supply power to activate the inboard solenoid. That was OK. Went back inside and before I shut down the engine I pushed the inside battery boost switch a few times and then noticed that the batteries were now charging? Shut the engine down, started it again, they still were charging.

For what reason did pressing the boost switch make the batteries start to charge off the engine alternator? Was the solenoid stuck and pressing the switch get it unstuck? Was changing the batteries related to my problem?

I will be making the 500 mile trip back home in a few days and wondered if this problem occurred again if it would be OK to just put a jumper connecting the house and chassis batteries as a temporary solution until I get home and have the MH in the garage where I have more tools and better conditions?

John Hilley · 11-07-2008, 02:39 PM

It should be no problem jumpering across the solenoid for the trip home.

John_Canfield · 11-07-2008, 02:52 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">....For what reason did pressing the boost switch make the batteries start to charge off the engine alternator? Was the solenoid stuck and pressing the switch get it unstuck? Was changing the batteries related to my problem?

I will be making the 500 mile trip back home in a few days and wondered if this problem occurred again if it would be OK to just put a jumper connecting the house and chassis batteries as a temporary solution until I get home and have the MH in the garage where I have more tools and better conditions? </div></BLOCKQUOTE>Sounds like the contacts are a little wonky and operating the boost switch is temporarily healing the contacts. The 'boost switch' is simply operating the solenoid like it would automatically if the engine was running.

For just 500 miles, I would run the gen set, or shut everything in the house off to minimize the current drain. You certainly could jumper the solenoid contacts, but that would be a bit of a hassle.

Yo - welcome to the club

Ready2Travel · 11-08-2008, 05:16 AM

Thanks for your response John/John.

I was going to jump the house batteries to the chassis batteries, not the solenoid connections.

I made a jumper cable that I have used to keep the chassis batteries charged when hooked up to shore power. My MH does not charge the chassis batteries unless the engine is running so I have to charge them every two weeks or so to keep them up even though I'm hooked up to power.

Hope I do not have the problem when making the trip home but can't see the difference jumping the battery banks instead of the solenoid contacts. Even so it would not have been that difficult to jump those solenoid connections if I had left that cover off. Not real easy to get it on/off, the three screws above the inverter were not easy to get to.