| Author | Message | ||||||||||||||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 232 Registered: 12-2004 Posted From: 206.212.230.165 Rating: N/A |
Well, I cooked the start batteries this last week. I am not sure what the root cause is yet. I could use some of your musings before I get into the diagnosis. First, here is the setup. Two 8D start batteries, and four 6 volt deep cycle house batteries connected to the alternator via a Vanner battery isolator. All batteries are the same age, just short of two years old. The alternator and voltage regulator are stock. There is a high current mechanical switch that can be used to connect the start and house batteries. In a fit of forgetfullness or stupidity, take your pick, I managed to leave the switch on connecting the house and start batteries. Not sure if this plays into the picture or not. Somewhere in the 300 or so mile range into our trip I started to smell something funny. You know the feeling. I realized it was batteries and remembered the switch. I stopped and opened the connection between the two battery sets thinking I was cooking the house batteries. The house batteries seemed fine. I didn't check the start batteries at that time. I motored on, camped for a couple of days, then headed off on the next leg. Things started stinking reall bad and I got out to look things over. There was battery acid dripping out of the start battery bay and steam (hydrogen gas!) boiling out of the batteries. This was not good. Being that I was a long way from anywhere, I flipped the battery cutoff switch to disconnect the start batteries and motored on to Prineville, headquarters of Les Schwab. They don't open on sundays, so I motored on the Wally World in Redmond, where I bought some car batteries to poke in the hole. I ran the new batteries for a short time and they started getting hot as well, so I left them disconnected except to start the Detroit. So here is the weird part. The house batteries did not get fried. I would think that this is a voltage regulator problem, but I wonder if the Vanner isolator is toasted and causing the charge to continue to the start batteries. Anyway, all thoughts appreciated on this one. I have not looked at a thing since I parked the bus here at home last night, so no real investigation to report on. Craig - MC7 Oregon | ||||||||||||||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 3 Registered: 8-2006 Posted From: 207.231.80.150 Rating: N/A |
You're obviously running too much current through the starting batteries. Why? If the running lights and all of the other 24v accesories didn't burn out while running with the battery switch open, then it is not a voltage regulator problem! Are you using 12v headlights wired "between" the two coach batts? Or something else wired onto one coach batt only?. The voltage reg. will try for about 27v, and if there isn't 24v of resistance in the batts, too much current will flow. 2nd set of start batts rules out one shorted batt, and recurring problem says to look at the charging circuit output path. A 24v bus alt can put out 40 something volts open-circuit, which will burn out all of your light bulbs if the reg has failed and everything else is alright. Look at the vanner input voltage to ground with a dc meter, eng running, bat sws closed, look also at the outputs, all SHOULD be the same, with about .6v loss across the vanner. If the vanner input (alt output)is over 28-29v, and house batts read 24 or less, vanner is bad. Do need some more info, as headlights should have burned out with battery boiling voltage, and open batt sw. but hope this helps. | ||||||||||||||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 233 Registered: 12-2004 Posted From: 206.212.230.165 Rating: N/A |
George, - I will look at those measurements. The headlights are 12 volt and are powered by a Transpo DC to DC converter. The rest of the running lights etc. are still 24v and are all OK (we'll see if they last as they might have been "wounded" in whatever happened). As far as the open battery switch goes (I admit this was a snap decision) my thought was that the Vanner isolator, if at least partially functional, would present the load of the house batteries to the alternator. Until I figure out what all is wrong, this theory will be just that, a theory. At any rate, I like your suggested debug procedure and will give it a try once I catch up on things a bit from being gone. Craig - MC7 Oregon | ||||||||||||||
| T. (Bluegrass)
Registered Member Username: Bluegrass Post Number: 202 Registered: 4-2002 Posted From: 72.160.128.100 Rating: N/A |
Crag The start Batt Is getting a little 2 much charge the regulator Is set at specs for the Air conditioner and or the heater, I did the same thing on my 1969 MC-7 and just backed the regulator off a couple of points, make sure that you have plenty of water In the Battery | ||||||||||||||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 4 Registered: 8-2006 Posted From: 207.231.82.128 Rating: N/A |
Craig, The open (no connection-off)battery switch was the thing to do! It got you home intact, and without the cost of a tow. A 24/12 converter will hold back a lot of voltage, so the headlights would still be ok. You did say "last night," so I assumed you drove at least a little with the lights on. If you did, and the instrument lights were still lit, the reg. is ok. I also ASSUME that this wasn't the first trip in the coach, or the first trip since electrical modifications? As info, a 12v load on one battery appears to the charging system as a somewhat low battery, (the current through the load has to go through the other {innocent} battery) This overcharges ONE starting batt, not two! If the coach alt could see both house and coach batts, BOTH would have cooked. The voltage regulator has to "see" what the system voltage is. It does this by an input wire from the master switch. It also uses this as its source for the field current to control the alternator output. If the input wire were not switched, the regulator would turn on full field current and stay there, calling for full alt output when it can't get any because the engine is not running. Consequently, dead batts in a couple of days. You obviously have LOTS of alt output, which means you have LOTS of field current. Don't bother going there, remembering the house batts are ok. I also assume there wasn't an open switch on the house batts? Also, need to know hot to ground voltage from the engine side of the batt switch with it open and the eng idling. Shouldn't be more than 28.5. Still need more info though... George | ||||||||||||||
| Jerry Liebler (Jerry_liebler)
Registered Member Username: Jerry_liebler Post Number: 226 Registered: 3-2005 Posted From: 75.117.214.6 Rating: N/A |
Craig, You could have a wiring error or failed isolator, otherwise the house batts would also have been destroyed. Here is my suspicion of a wiring error in your 'intertie' switch's wiring: If the sensing for your alternator's regulator were on the house battery and your switch tied the alternator's output to the bus battery (basically shorting out the isolator's diode to the bus battery). Another possibility is that the diode in the isolator that feeds the bus battery is shorted. It would be very instructive to have measurements of both battery's voltage with the engine running and your switch in each position. Regards Jerry 4107 1120 | ||||||||||||||
| Mel La Plante (Mel_4104)
Registered Member Username: Mel_4104 Post Number: 16 Registered: 7-2006 Posted From: 208.181.100.31 Rating: N/A |
Craig the other thing that might have gone wrong is that the selenoid on the starter has actered up and stuck in place leaving it turning over even after the engine started and you would not hear it over the engine noise as the benbix kicks out but the armature still turns and over a period of time it will heat up increasing the amp draw off the batteries and once the start to boil it does not take much to boil out the water, this why some vehicals have started cut out switches. | ||||||||||||||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 5 Registered: 8-2006 Posted From: 207.231.82.128 Rating: N/A |
Morning Craig, Don't want to dis Mel, BUT you did tell us about buying new batts after the first incident, "camped for a few days, motored on, Schwab closed on Sunday, drove to Wally's," new batts go hot too, etc. An energized starter with no load will destroy itself in less than a minute from tremendous overspeed! Since you have been able to start the bus at least five times since the problem manifested, its not the starter. I think Jerry and me have said exactly the same thing slightly differently. Now there's two of us wanting more info, Sorry! George | ||||||||||||||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 234 Registered: 12-2004 Posted From: 207.101.213.58 Rating: N/A |
Wow - thanks again to all for all of the ideas. I probably won't get to look into the bus issues to this weekend... I am back at work paying for the sins of taking time off... home late last night, not looking good for tonight! Mel - any thoughts on a clever way to check the solenoid? (Hopefully without taking that anvil starter off! ) Since I am going to tear into this I want to check out everything. Reliability is the #1 stress reliever in bus trips for me! It has sat a fair piece lately so the bendix et. al. could be sticky just like the blower assembly (below). If I do need to take it off I assume that it is an overgrown version of the car starters I have torn into over the years... any thoughts on this much appreciated. Further history - the wiring configuration has not been changed in the bus. The bus also has not been used much in the last year, a few local (2 or three errands) trips and such to keep things moving. We have been replacing the windows, carpeting, seating and so on to update the bus so it has sat still (other than getting turned around once in the driveway) since spring. We put about 1000 miles on it this trip for our shakedown cruise after having it "in dock" for a year. The problems we had included this electrical goober, the house water pump going intermittent due to corroded / oxidized electrical connections, and one of the blower dampers on the squirrel cage fans only partially opening. On the blower issue, the bus was running warmer than it should for the conditions so I stopped to find out why. The left side damper on the fan was only about one third open. I pulled it the rest of the way, but each time the dampers cycled, the left one would not fully open. Since I was running in the mountains and it was warm, I disconnected the rod to the damper and wired the left one open for the balance of the trip. Looks to me like surface rust due to lack of use and lube. I'll take all of that apart, clean and lube it, then see how it goes. Anyway, thanks again for all the leads. There is a great deal of quality thought here and I thank each of you for taking the time to offer it. Craig - MC7 Oregon PS: George - post a picture of your bus! I love the look of the 6! | ||||||||||||||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 77 Registered: 7-2006 Posted From: 66.217.105.133 Rating: N/A |
An uder dos centavos? "but I wonder if the Vanner isolator is toasted and causing the charge to continue to the start batteries. " Take the vanner out of the circuit, leave the engine batteries connected directly to the alternator/regulator (as it was OE), and see what happens. Why go 'round in circles chasing a problem? Isolate it....! | ||||||||||||||
| David Dulmage (Daved)
Registered Member Username: Daved Post Number: 133 Registered: 12-2003 Posted From: 142.46.199.30 Rating: N/A |
I've had the starter off my MC-8 to replace the starter drive. It's basically just a larger 24V version of a typical Delco car starter with a Bendix drive, not that hard to work on. Dave D | ||||||||||||||
| JR Lynch (Njt5047)
Registered Member Username: Njt5047 Post Number: 43 Registered: 7-2006 Posted From: 69.132.238.127 Rating: N/A |
Be certain that the battery disconnect switch is "off" when removing the starter. Just 3 bolts and two wire terminals (3 if you have a starter ground cable) allow removal. Leave the top bolt in until the other two are removed...and be careful..the starter is heavy...I'd guess about 40 or 50 lbs. I pull mine by myself by setting a floor jack beneath the starter. The fuel filters make it a PITA to get out, but it will tilt and come out. IMHO it really doesn't sound like your starter is at fault. If your coach is OEM, you may have an interlock on the fuel filter that prevents engaging the starter when fuel pressure is seen...however, this would not help a "hanging" bendix or solenoid. My dos centavos..JR (Message edited by njt5047 on August 30, 2006) | ||||||||||||||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 990 Registered: 5-2001 Posted From: 65.74.70.16 Rating: |
Craig, you said that you have the stock regulator and generator. But you didn't say how hot the weather was where you were when you smelled the batteries. If the starting batteries were already fully charged when you started your trip, and the ambient temperature got up to 100 degrees or so, the voltage regulator setting would be quite a bit too high. This would lead the starter batteries to start overcharging, which in turn would turn the overcharge current into heat. This would aggravate the difference between the regulator setting and the correct float voltage, lead to more overcharging and to more heating. At some point, you can reach a thermal runaway condition in your batteries while everything else in your system seems like it's normal. This is the reason that temperature compensation on the batteries is so useful. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||||||||||||||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 237 Registered: 12-2004 Posted From: 206.212.230.165 Rating: N/A |
Tom - we were running in 90+ degree weather most of the day, but how hot I am not sure. I got a complaint from the wife earlier about something smelling hot, but I didn't smell it "so it wasn't real".  When I actually smelled the batteries it was cooling down in the evening and we were climbing hills at about 4500 feet (read: with a MC7 and 8V71N @4500+ feet Þ not much air movement to dissipate the smell, yuk yuk). OK - drum roll, here are the voltage measurements I was able to take tonight:
I took the "Static" reading before starting the bus. The bus has not been started since Monday night. The "Running" voltage was taken at idle (not fast idle, just the regular old purr). The measurements were taken on the lugs of the Vanner which is located in the engine bay using the same ground reference for all three lugs. I find the alternator reading peculiar but the voltages were moving around some as the bus idled. I may need to take better readings. It looks like I really did overcharge the house batteries, even if they were not hot to the touch or fuming. The low start batteries make sense to me because I have started the bus several times since this happened and then always immediately disconnected the start batteries so that they would not charge. Looks like I need to learn about setting the regulator, assuming that it is OK. Thoughts on the voltage readings? Thanks, Craig - MC7 Oregon (Message edited by ceieio on August 30, 2006) | ||||||||||||||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 6 Registered: 8-2006 Posted From: 207.231.82.128 Rating: N/A |
Craig, aqui tiene usted cinco centavos mas. !DON'T WASTE ANY TIME ON THE STARTER! You have alreay told us in the first post that you camped for three days after the problem started, right? IF the solenoid had welded closed, AND the starter didn't explode from over revving for however many hours you drove after first noticing the problem, you darn well would have heard the starter screaming WHILE YOU WERE CAMPED FOR THREE DAYS!!! You have also told us "I have left the starting batteries disconnected except to start the Detroit." I don't want to sound like a "know-it-all," but I did read your post carefully before making a long range diagnosis, and I am a licensed electrician. Both our buses have the same voltage regulator, which is equipped with temperature compensation. You have told us, without being explicit, (or deliberately obscure) that you started the bus several times, with two different sets of batteries, after the problem started. You also told us that you drove the bus with the starting batteries disconnected. That DOES MEAN that the starting system is OK. I feel strongly that a failing regulator would have fried the house batts also, IF everything else were correct. It hasn't failed completely, or the bus would stop due to no power to the engine run relay with the batts disconnected. Small light bulbs won't stand much overvoltage, so the excess voltage applied across the batteries should burn out a lot of small bulbs. IF the bus has had NO wiring changes since the last drive of a hundred miles or so, then the problem is a failure. If you have changed any wires, look there. Look also for a high-resistance ground on the voltage regulator. Look also at anything making 12v out of 24v connected to the start batts. As mentioned above, if you just want to do something, disconnect the batteries, then disconnect the Vanner. Bolt the alternator lead to both the start and house batt leads, tape or don't let it touch ground, connect batts and fire up. No more than 28.5 volts across batts at high idle with bus air OFF. John, Jerry, JR"s IMHO, and me are all saying the same thing. I wonder if this board is a democracy? Ha Ha. Do we get to vote on the cause of the failure? Yours & my bus were both run across several Southwestern deserts for YEARS by the Dog without boiling batteries, not to mention that you told us you were in Prineville. LOL, and we gotta know what you find!! George | ||||||||||||||
| niles steckbauer (Niles500)
Registered Member Username: Niles500 Post Number: 660 Registered: 11-2004 Posted From: 24.129.157.205 Rating: N/A |
Craig - Did you by chance top off your batts before the trip? - and did you possibly disconnect and reconnect the batts while filling them? - Do you have a center tap? - Could you possibly have incorrectly reconnected the center tap? - sorry if this seems too elementary ..... but .... | ||||||||||||||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 240 Registered: 12-2004 Posted From: 207.101.213.58 Rating: N/A |
Niles - thanks all help appreciated! No center tap on the start batts. I did not top up the batteries before the trip, <sheepish> in fact I did not check them at all... probably for 6 months or so. I did check the house batteries, but inexplicably, not the start. Craig - MC7 Oregon | ||||||||||||||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 79 Registered: 7-2006 Posted From: 66.217.105.48 Rating: |
Since the "problem" was continued with the installation of the new engine/start batteries, the water level of the old ones is moot, at best.... Get that Vanner off line and the batteries connected as they were OEM, originally. If they boil, turn the regulator down to 26 vdc and check again. If they didn't boil, then get rid of that damned Vanner. Most bus outfits tore the Vanner battery equalizers out after a few road calls.... Are the Vanner isolators better? | ||||||||||||||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 7 Registered: 8-2006 Posted From: 207.231.80.150 Rating: N/A |
Evening Craig, All the running readings are high. A fully charged 12volt batt should read 12.56. It is possible to get a battery to read over 14v for a few minutes, this is called a "surface charge," and it will go away quickly. Charging voltage should not exceed 14.2v on A 12v batt, or about 28.4 on a 24v system. Niles asking about a "center tap" is suspicious of the same cause as I was. Please fire up and read the voltage between the input terminal of the Vanner, and the start batt terminal, record, and then read the voltage between input and house terminal, readings should be about 0.6 or 0.7v. A reading of 24v nominal says that that part of the Vanner has failed open, a reading of zero indicates a shorted side. Please also read the voltage to ground on the regulator input (sensing) wire with the engine running. Should be EXACTLY the same as the starting batt terminal of the Vanner. If it is ANY lower, there is the area of the fault, as the reg is trying to make up for what it "thinks" is low voltage. 33v on the house batts and no smell! Had you been plugged into shore? Whew The static alternator reading says that neither side of the Vanner is shorted, but I do have a problem with the alt output voltage being lower than the batt voltage? Corroded terminals and high resistance grounds cause many problems, but still. IF the regulator input voltage is above 28.5, preferably in high idle if you are still so equipped, with the headlights on, turn it down slowly until you get there. Please also take a 3/8 nut driver to EVERY stud in the terminal boards. My 6 had at least 20 loose nuts, and actually had a new wire run through the bays from the reverse switch to the shift solenoid because of a loose wire, not to mention the company mechanic couldn't read a schematic! It would have been a whole lot easier to have used one of the spares! LOL, all of it good! George | ||||||||||||||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 241 Registered: 12-2004 Posted From: 207.101.213.58 Rating: N/A |
Thanks George - I'll give all that a go this long weekend in between the honeydo's. I was looking at the wiring layout in the schematics last night anyway to prep for installing the jake brake that has been sitting in the garage for a year... I need to poke my nose into the wiring boxes either way! I read the manual on adjusting the regulator last night... looks like more art than science; involves tweaking the regulator and charting over/under charge and water useage (under fleet conditions) for a minimum of 48 hours before next tweak. The only point of departure they gave was 27.5v, fast idle or 1000 revs if no fast idle, accessories and lights on. There were lots of waffle-words in the book about the 27.5v. After referencing the 27.5 etc. etc. above is when they went into the charting stuff. I think I will give the 27.5 with the bus heat and lights on as a starting point and see what goes from there. I will also tighten up all the lugs as suggested and check the ground on the regulator. thanks again! Craig - MC7 Oregon | ||||||||||||||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 992 Registered: 5-2001 Posted From: 65.74.70.16 Rating: N/A |
Craig, there are numerous tables available on the web that show battery voltages for different temperatures. Xantrex manauls for some Trace and Heart inverters have these tables. Good luck. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||||||||||||||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 245 Registered: 12-2004 Posted From: 206.212.230.165 Rating: N/A |
Tom - thanks, I'll look for them. Depending on when I get to it it could be quite warm... predicting 90 degrees here in the Pacific Northwest. Thanks again. Craig - MC7 Oregon | ||||||||||||||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 250 Registered: 12-2004 Posted From: 206.212.230.165 Rating: N/A |
Well, just to tie up the loose end... today, manual in hand, I went out and reset the voltage regulator on the bus based upon the book procedure. It is set at 27.6v, down from almost 32v!!! I will monitor the beastie for a while to make sure all stays OK. I need to plan another bus trip to make sure this fix is going to hold! Thanks agian for all who helped me with this problem. Craig - MC7 Oregon | ||||||||||||||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 8 Registered: 8-2006 Posted From: 207.231.82.128 Rating: N/A |
Craig, Thanks for the info! A "trip to check the voltage regulator," sounds like a great idea to me. George |
