Tiny Tim Tank Battery Charging Unit

Hi, everyone, just acquired a 1944 battery charging generator. It has been dry stored for 30 years. The MOD have over stamped it at some time, and added a SU fuel pump. After servicing the unit, had petrol engine running but no output charge. Made a few changes and then had to disassemble it again after dropping a screw inside, through one of the round holes in the generator body. Must remember to tape them up next time. Will inspect a few things why it does not charge shortly.
Does anyone have any ideas re no charge.
Regardpeter76.

Interesting project! I've never had one of these but I have had a similar tank charger in the past. I assume they're all pretty similar.

I think it will have an generator that will feed into a simple rectifier/voltage regulation circuit. The first step is probably to take it apart and make sure all the electric connections are clean and working, probably there will be some brushes on the generator that may well need cleaning or replacing. Then check for output (AC voltage) from the generator with a multimeter when the engine is running and work from there until you find the fault.

Does it have the ability to start the engine from the battery and if so does this part work? That would indicate at least half of the circuitry is working....

Hi, Will, many thanks for your reply and very helpful suggestions. Some of the electric connections on the wiring are breaking apart ,now that the unit has been dismantled twice. Time to check everyone of them. One of the brushes was broken in half, which I have replaced with a 355 from a Kano breaker. The same size ,except one dimension was 2 mm thinner.do old carbon brushes deteriorate with age and all need to be replaced? The electric starter does start the petrol engine by use of starter button.
I will modify wiring connections if suspect.
Thankyou for your advice..
Regards,
Peter.76.

Hi, there. I have dismantled the generator and made the electrical connections good around the starter button and amp meter. I have yet to inspect three of the carbon brush connections. As yet no output. The motor starts on the button, runs for a few seconds and then dies, excessive choke helps for a few seconds. I have checked the ht lead, spark plug, cracking spark. Changed the fuel supply system, cleaned and blown out the carb. Does anyone know what this unit should have for a minimum compression reading to run. Will check the reading as next
Many thanks,
Peter76.

what's the item mounted on the plate, tiny tim's on youtube don't have it, their carbs are connected directly to fuel tanks.

Maryalice

Useage 
Hi, Maryalice, thank you for your reply. The item on the silver plate is an electric SU fuel pump, I assume the unit was placed on the AFV and
fed from a separate fuel tank on the ground . I have seen a picture of the complete setup from the Sherman tank which used a gravity fed fuel tank mounted in the hull. I have looked on Utube, very helpful to spot some wiring connections. No detailed wiring diagramme seems to be available.
Regards, 
Peter76.

So going back to your electrical issues. I think the starter just connects the battery directly to the generator and effectively uses the reverse process. So instead of the motor spinning the generator to create electricity to charge the battery it uses the electricity in the battery to spin the generator as a motor to start the engine.

So if that is working it means the brushes, the coils in the generator etc are all good. So your issue has to be somewhere in the regulation and charging circuitry....

H, Will, Many thanks for your reply and explanation. It’s good to hear that some parts of the unit are in working order.I will check for any output voltage at the voltage cutout, which is still original one. connection. Is marked gen and the other battery.
Regards, May have sent too many of the same photos.
Peter76.

Don't worry - double posting pics is common when you are new to the process.
Just avoid double clicking 'Send All' and wait for the 'Insert All' message.

Many thanks for that, my IT useage will hopefully improve.
Regards, 
Petr76.

Hi, Will, today I have the motor running reasonably well. After raising the float height, the float chamber flooded. After checking, I realised that I had set the float height too high, thus the top of the float was touching the underside of the lid before the float valve was fully sealing the inflow of fuel. I do make mistakes! I also found that I had not cleaned the drilling’s out completely. The engine fires immediately now, very satisfying. It is now possible to increase or decrease revs with the knelled wheel on the carb.
My next job is to discover why no output charge is present which should prove interesting.
Regards
Peter761

Hi, there. Had a further look at the voltage regulator, cleaned the points and also the end of the magnet where it moves the flap connected to one side of the points. I connected to a charged car battery and discovered no movement of the points closing. I placed a meter between generator output and the gen contact of the voltage regulator and started the engine. The meter read 5.5 volts for a second and then settled at 1.5 volts.
I have also found that the external capacitor is dead. Trying to sort a suitable one from Lincoln. Does anyone know what MFD value this should be
At 100 volts working. I have compression checked the motor at 43psi. Would this be sufficient to drive the gen on load.
Any info would be of great help.
Many thanks,
Peter76.

Hmmmm, I'm no expert on these electro-mechanical regulators - maybe someone with more knowledge will be able to provide more insight.

I think generally inside the unit should be at least one relay, maybe more which connect and disconnect the generator from the battery depending on the battery load. So assuming you have a 12v charging set I think the basic theory is that if the voltage gets above say 14v the relay disconnects and prevents over-charging the battery, then when the voltage drops it clicks back in. That's the basic principle anyway. I think some units are more advanced with more relays which can shunt power into resistors or take the output from different numbers of coils in the generator side etc to give a nicer output that a straight on/off. I think in terms of getting it running a good start is to make sure all the contacts are clean, maybe open and close them and check for continuity with a multimeter across the connections if you have one?

The other thing is this type of regulator are commonplace in old tractors so you might be able to find more info on old tractor forums etc. You might be able to find a suitable similar unit for an old tractor to swap into your set to see if that fixes the problem.

The other issue you might have is sometimes generators loose their magnetism if they sit for a long time un-used. You might need to re-magnetise the generator. I've never done it myself but you can give it a go - seems simple enough! https://www.youtube.com/watch?v=ZDEYPszsbuc Note in the video he's connecting his up for +ve earth, I think you will need to do your's the other way around (-ve earth) so connect the field and output connectors to the +ve terminal on your battery and the ground to the -ve.....

Good luck!

I have a couple of ex military BSA Generators, they put out a max voltage of 15 VDC, the voltage can be reduced manually by a dial on the generator, the unit doesn't have any relays so if left the generator will eventually over charge and damage a battery, the battery will get hot, so I run mine with a load, lamps.
As suggested there is a chance your unit needs remagnetising.

Maryalice.

Hi, Will and Maryalice. Great to hear your replies. Your information is so welcome. I have cleaned points and end contact of energising coil. And connected to charged car battery. The only movement is when I press the flat down to close the points. No magnetic effect in the coil.
I think you are correct that the gen coils lack magnetism. I will watch suggestions and experiment, awaiting new capacitor. Also sourcing a different regulator to try.
With Best Regards,
Peter 76.