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Author Topic: Brush 7kva battery charging problem.  (Read 125 times)

Onzlow

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Brush 7kva battery charging problem.
« on: November 04, 2018, 09:43:45 AM »
Hello,
I have a ST2 Startomatic with a Brush 7kva generator . It has a 24v starting system.
Normally, after starting the generator will charge the two 12v starting batteries (24v) and the voltmeter will show a charge of about 2 amps depending on whether you switch to fast or slow charge. However the voltmeter now shows a discharge of 4 amps or more ( voltmeter only goes up to 4amps). This drains the batteries and the generator cannot then be started remotely. I suspect some contacts in the alternator are not releasing, so I would appreciate if someone can point me in the right direction.

ajaffa1

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Re: Brush 7kva battery charging problem.
« Reply #1 on: November 04, 2018, 11:11:13 AM »
Hi Onzlow, I have an ST2 startomatic which I rebuilt. One of the finest and most over engineered pieces of generating equipment on Gods earth. I have had exactly that problem, it is caused by the fuel control solenoid, which is kept open by the 24 volt charging circuit. There are two possible causes for this and I have experienced both.

1: The solenoid has two coils in it, one is high powered and designed to open the rack, the second is low powered and only designed to hold the rack open. There is relay built into the top of the solenoid  to switch between the two solenoid coils. If the contactors are dirty or out of adjustment it will continue to run on high power and discharge the batteries, It will also eventually burn out the solenoid coil. (see photo attached and a rather poor circuit diagram)

2. Dirt/corrosion/misalignment of the shaft that the solenoid lifts will also have the same effect.Try spraying some lubricant and then manually lifting the solenoid up and down.

Let me know how it works out,

Bob

Onzlow

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Re: Brush 7kva battery charging problem.
« Reply #2 on: November 04, 2018, 12:00:31 PM »
Bob, thank you for your prompt reply. Yes that makes complete sense as I have had problems with starting and had to operate the fuel cut of valve manually on occasions. It will be a few days before I can get round to fixing but I am very grateful for your advice and will let you know how I get on.
Regards
Onzlow

ajaffa1

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Re: Brush 7kva battery charging problem.
« Reply #3 on: November 04, 2018, 12:12:22 PM »
Hey Onzlow, you are very welcome, both to my advice and also to the forum. There are a lot of experienced old guys like me on this forum, we do our best to sort out engine/generator problems. We don`t always get the diagnosis right first time but that is usually down to lack of information.

Good luck,

Bob

Onzlow

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Re: Brush 7kva battery charging problem.
« Reply #4 on: November 20, 2018, 05:41:52 PM »
Hi Bob, I hope you are still with me! You are right!
I have at last managed to get round to looking at the solenoid, and what seems to be the problem is the pin below the contact bar, that is held on with a split pin, has worn down or broken so that it is no longer long enough to lift the contact bar and break the contacts on the high power solenoid.
I must admit I am a bit puzzled as to how this has got worn, anyway I can make another one. I assume itís length is such that it sits just below the insulated pad on the contact bar.
I did notice that when I ran the generator and lifted the contact bar with a screw driver the voltmeter rose from a negative discharge to zero, which was good in that it showed the contacts were breaking, however I would have expected it to show a charge as the batteries should have been charging then. I checked the fuses in the box where the battery leads come in, they were ok, any ideas?

ajaffa1

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Re: Brush 7kva battery charging problem.
« Reply #5 on: November 20, 2018, 09:29:43 PM »
Hi Onzlow, If you have checked the charging fuse and it is OK the only other possibility is that Line Contactor two in the main relay is not making a circuit. Please do not do this with the generator running as some of the contacts run 240 volts. It may be that the high current leak you were experiencing has fused the contactors together in the standby/start position.

Please see the photo attached, the red wire goes to the ammeter, the white wire goes to the battery and the yellow wire connects to the charging circuit fuse.

Bob