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Engagement
  • Author Author: M0DCD
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Never look a gift horse (or 2,500 of them) in the mouth

M0DCD

It lurked at the back of a railway yard somewhere in England's largest county, having been consigned for recycling (well scrap to us), but the deal with the buyer had fallen through and it just sat there. Came along the summer and someone asked if we could give it a run in the Autumn, and the communication was "sure, if you can get it to run that is". Well they did, but the batteries we're all that brilliant. That's where I came in, someone asked me to make a battery charger.

 

You can guess that they did manage to get her going, the sound of a Sulzer engine being heard for some distance as well as the initial cloud of balck smoke.

 

The first thing I found out is that the batteries were a total of 110V and that the capacity would run a laptop for several years. Then the bombshell, they are not lead-acid, they are NiFe. Current arrangement (minding the pun) is to use a 24V charger for lead-acid batteries and to rotate the cells under charge, but it's more luck than judgement. Last weekend, well, whilst it was idling two cells managed to blow out the vent caps.

 

My charger design's going along the lines of "brute force", that is switching in resistors if the current goes above 8A (we are only trickling these), but needing a decent voltage to wake these up from slumber. They have a reluctance to charge from flat - just high resistance - but they do come back into life with a vengance.

 

So if there's anyone out there with design experience of large Ni-Fe chargers - please let me in on the secret!

  • in reply to Former Member

    The charger has gone into the production phase, the pile of components being handed over to our metal bashers to mount in a suitably robust box. "47703" is out of traffic with a siezed traction motor bearing at the moment, so it's on the back burner. The "regulation" is with big resistors with bypass polyfuses, so if there's too much current, the resistors come in to play to limit the current. No moving parts, no fancy electronics, and something even the "Traction Technicians" can handle.

    They did go shopping for a few new batteries a while back, but most of the ones they came back with weren't much better than the ones they already had.

    Their pechant for replacing carriage lighting batteries is spawning another project, that is to change the management from NiFe to Pb technology as they are a fraction of the price. More of that later.

    I could with communications lines and power (these were pulled up well before we took over the line)- we're doing a lot with solar power and have some automated crossings that we're fighting inertia in the ORR (Office of Rail Regulation) to allow LED lighting, although we are a lot nearer implementation and can have a lot of "off the grid" installations. Being on the edge of a National Park doesn't help.

  • The Edison cell is supposed to be abuse-friendly; sitting at railway crossings for years. Not nearly as fussy as Li-ion, say. I've heard of reviving dried out cells just by reintroducing water.

     

    Does the railway trickle charge them from the communications/signalling lines?