Lister Engine Forum
How to / DIY => Generators => Topic started by: jonnymcc on December 17, 2018, 09:06:11 AM
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Hi All,
I have an SL2 which I have running and all connected up. I usually just hand crank it, but recently I connected some batteries and the starting function is working. (apart from not operating the fuelling solenoid, but I'm not panicking about that)
Doesnt seem to be any battery charging though. I're read about a burned out rheostat, though nothing in my control box looked burned.
Are the charging electrics located in the generator top box or the wall box? I take it the ammeter on the wall box is for battery charging?
How is battery charging carried out? By the mention of a rheostat I assume there is a rectifier diode and the voltage reduced by resistance?
Any help/advice greatly appreciated.
Cheers,
Jonny
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Normally there is a switch on the top box to set the charge rate to Hi or Lo follow that wiring to the resistor. The taps on it may be just dirty and a cleanup will fix it.
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Hi, thanks for the response. Noticed that switch but the lettering was worn off so i didnt know what it did. Suspected it may be high/low. Doesnt make any difference at present.
Thanks for your advice; I'll get the lid off and have a look at the terminals as suggested.
Cheers,
Jonny
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The switch is CR5 and the resistor is CR in the diagram I sent you. Note that it goes through contact LC2 which is on the main contactor relay this must be operated to get an ammeter reading. CR is the top resistor in the top box on my setup.
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Thanks, I'll get a look at the diagram this evening. Hmm, I know that the switch is connected to the lower resistor in my box. I had forgotten I've already remade all the connections in there so all ok. Was wrecking my head last night trying to work out the wiring. Difficult to test when you don't understand what is going on. I think there is a rheostat in that top box connected by fuse to the positive battery supply, which is also bolted to the box casing; I cant see how its insulated from the casing, but it is!
My main worry was that it looks like my set has 240v outputs connected to the fuel rack solenoid - would have thought these would be 24v.....
Cheers,
Jonny
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So, i managed to miss the damage to the charging resistor. Any idea for a replacement??
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The fuel solenoid is connected to 24v via the contact on the start relay. I rewound my resistor with stainless mig welding wire from memory 6 ohms should do the job.
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Thanks for that, I was thinking about a rewind, though I'm a bit lazy......
Taking the current at around 4 amps and a charge voltage of 28.8v gives power of 115w ish. What about a modern 150w 6.8 ohm resistor?
Like this:
https://www.ebay.co.uk/itm/Resistor-Aluminium-6-8-ohm-150-W-2-5-kV-5-HS-Series-Wirewound/272683756229?hash=item3f7d37eac5:g:LrQAAOSwK6RZJF-4:rk:1:pf:0
What do you think?
Cheers,
Jonny
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Hi Jonny, looking at your photos I notice that your top box contains two wire resistors. I am guessing that the high/low charging switch is between them so you would use one for high charging and both for low charging.
I therefore believe that your maths might be a bit out on the ebay resistor.
My later model ST2 has only one wire resistor with adjustable taps (see photo) I am guessing that this would have the same resistance as yours, I will try to put a meter across it over the weekend and post the results.
Bob
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That would be great, thanks Bob. It doesn't "look" like the switch world on both resistors, looks like it just switches to the other tap point on the lower one. Though I'll see if i can trace the wiring this evening.
On another note, found out why the fuel solenoid doesn't work, the pot is empty and smells like it was once on fire.....
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Hi Jonny, sad to hear your fuel control solenoid is toast, it should contain two solenoid coils, can`t remember if they are on one bobbin or two. These can be rewound if the bobbin/s are intact. If not it is possible to turn a replacement bobbin/s from nylon or paxolin. I will try to measure the correct resistance across these coils this weekend.
I had to rewind a couple of coils in my control panel, it`s very hard to find good information on what size wire to use and what the correct resistance should be. One coil I rewound three times, with different wire, before I got something that worked.
Looks like you might be right about it having been wired to the 240 volt side of things, that would certainly explain the fire. One trick I learned when I was rebuilding mine was that a burned solenoid coil usually still contains approximately the same amount of copper, thus, if you weigh it you will get a pretty good idea of how much wire to wind onto the replacement.
Failing all else there are perfectly good modern fuel control solenoids available, shame to not keep it original but unless you want to take it to shows who cares.
Bob
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Hi Jonny, sorry it has taken me so long to get back to you. We had a bit of a weather event here last weak with more than 300 mm of rain in a day. Been a bit busy trying to clear up the mess.
So, on the charging resistor we have 17.5 ohms on low charge and 7 ohms on high charge. If it helps, the center ceramic bobbin has a diameter of 1.125 inches and there are forty turns of resistance wire to the linear inch.The overall length of the winding is 4.5 inches. This would equate to the resistance wire being around 0.025 inch which would be 23 SWG or 22 AWG, however I have no idea as to how thick the insulating coating would have been so the wire diameter is probably one or two gauges smaller. A quick calculation suggests that this equates to around 53 feet of resistance wire in total. So you need a resistance wire with a resistance of around 1/3 ohm per foot.
On the fuel control solenoid there are two coils on a single bobbin with a small relay switch on the top. To open the fuel rack both coils are used in parallel and they have a joint resistance of 3.6 ohms. Once the rack is open the relay switch cuts out one of the coils and holds the rack open with just the one coil, the resistance of that coil is 7.1 ohms.
I`ve attached a couple of photos which I hope will make my ramblings a bit clearer, have a Merry Christmas.
Bob
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No Problem Bob, thanks very much for the info!
Unfortunately, my FCS has been stripped out after the burning and there is nothing in there apart from the upper switch contacts. I'm pretty sure from the wiring that someone has fed it 240v, I need to tidy the wiring up as they have just taped it up inside there. This is not something I feel a great need for; I don't use the automatic function, though I may like to repair it sometime in the future, I would assume that the best way forward is going to be if I can fit some sort of modern replacement inside the original housing.....
Anyway, back to the charging, thanks for those measurements. I was trying to get a resistance on the remainder of mine and got approx. 5 ohms, so I reckon that 7 ohm should be about spot on. I actually bought a new replacement resistor for a slightly more modern start o matic which I spotted on ebay recently thinking the values should be similar; now I can check it out and see :) The dimensions are different but layout is the same....
Any idea what causes the resistor to fail? A short somewhere? I had a feeling maybe it was to do with someone running it without a battery connected and the +ve contacting the -ve or the frame?
Any idea what the second resistor in mine does? Looks identical to the charge resistor, but the wires too/from it go into the generator housing; could it be acting as a shunt resistor?
Thanks for your help; hope you had a great Christmas, and have a happy new year.
Cheers,
Jonny
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That is the shunt field resistor if you get around 240 out of the alternator leave it alone. The big resistor in the top of the gen. housing is also called a shunt field resistor used to set the current of the cross field and controls the voltage gain or droop under load.
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Ok, back to the drawing board!
I took some measurements and made a rough circuit diagram of my charge resistor today. Thing is, i eventually worked out that the damaged part of the resistor isn't in use anyway! It's bridged by a black wire.... I found 12 ohm marked on it but only around 6 ohm is used. Anyway I'm getting continuity across the resistor and up to the control box. Some of the wires on the charge circuit in the control box have been very warm at some point in the past...
Also i can't understand how the resistor burned out where it did, unless someone has already in the past repaired it by swapping it round..... Anything likely to over heat that circuit?
What's my next point to check the charging circuit?
Cheers,
Jonny
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My wiring diagram
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That is ok the( in) end is strapped to the +24 v end of the resistor below it the out end goes to top tag of the LC2 contact or the yellow wire which should come from it.
Adjust the maximum charging current to 4 amps which is the maximum your ammeter will take.
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Hi Guys, sorry I haven`t posted anything for the last five days, we had an internet outage which cut us off from the rest of the world. It also cut off Grafton, our nearest town. The biggest problem with this was that my Wife drove into town to do some shopping only to find that none of the businesses in South Grafton were able to do any online banking transactions, cash only. Not too surprisingly all the ATM`s were either empty of cash or had no internet connection to the bank. Fortunately she had forty dollars in cash in her purse and was able to buy petrol to get home. So much for the government`s dream of a cashless society in which they can demand a cut of every penny spent.
The telecom company responsible for this are not liable for any of the financial losses incurred by local people or businesses. All attempts to get information from their helpline proved fruitless as they have contracted all these services to India, Pakistan and Indonesia, while laying off all the Australian workforce that used to do this work. I am told that one of their internet routers required a re-boot (switch it off and then turn it back on again). Apparently they no longer employ anyone with the skills to push a button twice, a remote re-boot was not possible as the overseas technicians do not have that level of access. What a fu*ked up system! Hope all the executives that were responsible for this choke on their own vomit on New Years Eve. >:(
Rant over for now back to business: Jonny, Oldgoat is absolutely right about the wiring connecting to LC2, I am a little concerned about his suggestion that you should adjust things to run at 4 Amps. Mine runs 3 amps on high charge and a fraction over 1 amp on low charge, but I guess this could vary depending on how big and old your battery bank is. A much better solution is to buy a couple of 800 milliamp battery trickle chargers. These should be wired into a mains outlet, these will guarantee your batteries are fully charged when you get a blackout. If you fit a crossover switch in your fuse box, they will also charge you batteries, through the same outlet when you have to run on generator power. Probably a good thing that your fuel control solenoid no longer works as it pulls about 2 amps on start up and about 1 amp when running.
As for the cause of the burned out resistor, I suspect that someone has fed the 240 volt side of things to the fuel control solenoid and this has back fed through the charging circuit and the batteries, should have been quite a bang, wish I had been there to see it! :laugh:
Bob
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Sorry to hear of your recent troubles!! Sounds hectic! We had an issue recently where one of our banks systems went down and loved out bank machines, cards and internet banking. People were not amused.
On the charging front, I hear what you are saying regarding the trickle chargers, a much better charge too, but i hate to admit defeat.
However, i have traced continuity in the circuit right from the charger resistor the whole way to the battery positive terminal, by manually operating the main contractor with the batteries disinfected. If i manually operate the contractor with the batteries connected, engine stopped, the ammeter drops fully up the minus. I'm not sure whether this is to be expected or indicates a short.
I did find one wire conected which isn't on the diagram, from the White wire to the LCC rectifier. Photo attached. Might try disconnecting that and seeing if it makes a difference. Could the charging windings have failed in the alternator??
See attached, cheers, Jonny
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Hi Jonny, the charging side of the brush alternator also works as the starter motor. When the control panel tries to start the generator the ammeter should show a discharge of around 4 amps. Once the generator is running some of the 240 volt output gets rectified and fed into the solenoid coil causing the line contactor to change over from start mode to run mode. Once this happens the DC side of things should charge the batteries and show a positive charge on the ammeter.
Bob
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Hi jonny, what you show in your picture is a relay. Radio Spares (RS) did not exist when your unit was built so this is a later addition to the setup. It will contain a diode to rectify 240 volt AC to DC to feed the solenoid coil. It would help to know where the wires go.
Bob
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I did wonder about that, as it says relay on it, and it looks like a relay, but is plugged into the rectifier space......
I'll check where the wires go and let you know. But that white wire comes from the output from the ammeter and is the charge feed to the batteries....
Cheers,
Jonny
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Hi all,
Still haven't got the charging issue sorted, bit of a mystery as anything checks out. But on a side note, i have a brand new genuine lister/petter wire wound resistor, think its 47 ohm from memory, free if its of use to anyone, just cover postage.
Cheers for the help so far!
Jonny
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Contact LC2 which is a changeover contact is supposed to short out the ammeter until the contactor operates this removes the short and charging current flows through the ammeter.
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Ok, here are my latest findings:
I am using the set in "push button start" mode. Is battery charging supposed to work in this mode? I note that my main contractor LC does nothing; yet still i have 240v working fine? Does the auto/manual switch bypass LC when set to manual by any chance?
Strangely, when using the set in manual with push button start, the decompressor solenoid does work.... I did not expect this and in fact the manual says you must manually operate the decompressor in this case?
Ok another note, got the selenium diode D1 replaced with a modern equivalent. Seems to relate to the detection circuit.
All help appreciated,
Jonny
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Hi Jonny, when you say that your line contactor does nothing are you saying that it does not move? If that is the case then some silly bugger may have disconnected it and replaced it with the RS relay shown in your photo. Could you please post a photo showing what you have left in your wall mounted control box.
The decompressor solenoid is driven directly from the generator top box, as the brush head starts to generate it activates the solenoid engaging compression. When you shut down the generator this releases the solenoid and a spring pulls the decompression levers back into the ready to start position.
Bob
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Hi all,
So this problem is solved, and the result is rediculous...
My set doesn't charge the batteries if you set the control box to "push button start". This setting bypasses the main contractor. On automatic, it charges grand. I'm not sure why you wouldn't want to charge batteries when using push button start, but i suspect it's more to do with hand cranking.
My only problem now is the main contractor chatters a bit... But i see someone has bypassed the resistor that i believe it's supposed to prevent that.... Resistor tests ok, I'll maybe try reconnecting it....
Thanks for all your help so far!!
Jonny
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Hi Jonny, sorry not to get back to you sooner. I have had exactly the same problem with chatter on the main relay. I like to start my SOM with just a single light bulb, I then allow it to get up to full voltage before throwing the main crossover switch in the distribution board. These were designed to auto-start with a load of around 60 watts. old fashioned 60 watt light bulbs are difficult to come by here so I have had to use 40 watt bulbs, thus the chatter, get a decent load on it and the problem should go away. The DC voltage that opens and closes the main relay is rectified from the 240 volt ac system, however the other smaller relay which initiates start up is maintained from the back EMF created in the wire wound toroidal core. In standby mode there is a 24 volt potential which, when fed through a 60 watt load, is sufficient to engage this relay and initiate the start cycle. Once running the toroidal core produces a small AC voltage which is rectified and used to keep the relay powered. Once the load is turned off the back EMF in the toroid vanishes and the relay opens instigating shut down.
Bob
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Hmm, thanks for the response Bob.
I believe I am using a 60w bulb; its one thats been around here since the 70s!! I'll see if i can find another but as you say, they are hard to come by. I have a massive 150w bulb about here too, but it produces far too much heat for any of my fittings!
Any thoughts on that resistor that has been bypassed?
Cheers,
Jonny
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Hey Jonny, if the resistor tests OK try putting it back in circuit, it can`t do any harm it will just drop the voltage and current, I struggle to understand why they took it out in the first place.
Bob