BCR...again

@CALNNC posted:

This is a general question about BCR's in MTH locos, and after correcting a problem with the help of gunrunnerjohn, wanted to know if there is a known issue about using a BCR in older MTH locos.  I have a 2-6-0 with original Protosound, it has no engine number, it has no model number anywhere on or in it.  I put in a BCR, and it immediately burned up the 24 ohm resistor that is in the lead to the battery.  I have used this same BCR in other MTH locos with no issues, but they do not have that 24 ohm resistor.  I have an older ABA set, #20-2168-1, and like that 2-6-0 it also has that 24 ohm resistor in the battery lead, so right now, planning on sticking with a rechargeable battery.  I was wondering if anybody else has experienced issues with installing a BCR in older MTH loco's, or if there is already a warning out there to not do so.  Also, does anybody know if the Eveready 9V rechargeable is actually 9 volts, or in this case 8.4 volts since the individaul Nicad or LIon cells that make up the battery are 1.2 volts instead of 1.5.  I read somewhere to be careful because some branded 9V rechargeable are really only 7.2, with only 6 cells in the case instead of 7.

All the 7-cell NiMh batteries are 8.4 volts nominal voltage.  NiCad is no longer the choice, use the NiMh batteries.  FWIW, it's been quite a while since I've seen a 6-cell "9 V" rechargeable, I think they're almost universally 7-cell.

@gunrunnerjohn posted:

"... I think they're almost universally 7-cell."

Thanks again John.  I was looking for the best deal on the Eveready 9V rechargeable, Amazon being one of the better places, but some commenters warned that they were still finding 7.2 volt batteries.  At one time, the 9V was called a 'transistor radio battery', but that is pretty archaic, so is the AA cell that was originally called a 'Penlight' battery.  I have an old Ray-O-Vac, that amazingly has not leaked and ruined something, with the words penlight battery on the label, plus '2 for 25' cents and  made in Madison Wisconsin,  that makes it really archaic.  My best Eveready example is a pair of D cells I found in an old aviation radio, made in November of 1952, in perfect condition, and still show about .6 volts on them, not enough to light the tube filaments though.

CALNNC:  I have quite a lot of very early PS1 loco's (mainly diesel), and have never seen any resister inline in the battery lead.

Does you PS1 board have all of the feed wire leads soldered directly to the bottom board, or does it have the Molex plug connections?? Real early boards had every wire soldered.

Been running BCR's in all my PS1 and PS2 loco's since I have owned them (years now) with no problems what-so-ever. Only problem using a BCR in the very early PS1 loco's is you have to start at 10V for one minute to fully charge the BCR, and then throttle down very slowly to get the board out of the "reset" mode.

Sometimes I have to shut them down completely after the one minute charging time, and start them up again at only 5V, to get them out of "reset" and moving forward.

A photo of the inline resister would be interesting.

Peter.....Buco Australia.

@Buco posted:

CALNNC:  I have quite a lot of very early PS1 loco's (mainly diesel), and have never seen any resister inline in the battery lead.

Does you PS1 board have all of the feed wire leads soldered directly to the bottom board, or does it have the Molex plug connections?? Real early boards had every wire soldered

This resistor- next to the battery connector.

@Buco posted:

CALNNC:  I have quite a lot of very early PS1 loco's (mainly diesel),

Well, is Protosound the same as Protosound 1?  I have boxes that say Protosound, as this ABA set does and has the 24 ohm resistor, but my Protosound 1 labelled items  seem to have a totally different method of providing voltage to/from the battery with the battery plug on the opposite end of the board than the plain Protosound.  Protosound evolution is as confusing as all the manners of controlling Lionel locos, as long as my ZW will run them, I am happy.

Yes Vernon.....that is the only resister I am aware of as well.

The PS1 board you posted the photo of has the Molex connector plug onto the board, but the very early PS1 boards had the battery charger wires soldered directly onto the board.

From the description in the original post by CALNNC, he suggests the resister was inline "I put in a BCR, and it immediately burned up the 24 ohm resistor that is in the lead to the battery"

Am I missing something here??

Peter.....Buco Australia.

I think you are taking "inline" too literal.

It's in series in the circuit on the board with the battery- series= inline.

Edit, and yes, I'm aware of boards that were early versions with a battery switch and often directly soldered wires for the battery connector to the board.

CALNNC.......I'd love to see a photo of your board, if that is possible??

Peter....Buco Australia

@CALNNC posted:

Thanks again John.  I was looking for the best deal on the Eveready 9V rechargeable, Amazon being one of the better places, but some commenters warned that they were still finding 7.2 volt batteries.

You might find 7.2 volt batteries, but they're easy to avoid.  I've used the Tenergy and EBL brand batteries from Amazon, and never gotten one that didn't have 7 cells.

I converted all of my Proto locomotives to BCRs and have never had a problem ... and I have about every combination of boards they made.

@Buco posted:

CALNNC.......I'd love to see a photo of your board, if that is possible??

Peter....Buco Australia

Actually, the picture that Vernon Berry posted was the one I included in my original posting.  It is several up the page from here.

Thanks CALNNC......your photo didn't show up on my laptop view of your original post. I can only see the photo posted by Vernon, and didn't realize it was your photo.....sorry.

Yeh, that is a later model PS1 board, with the battery wires attached to the bottom board via a Molex plug. Nothing unusual there.

Don't know why you blew the resistor on the board using a BCR.....maybe the polarity of the BCR was back-to-front in its manufacturing process????

I'll bow out now, and hand it back to GRJ and Vernon.

Peter.....Buco Australia.

@OGR CEO-PUBLISHER posted:

I converted all of my Proto locomotives to BCRs and have never had a problem ... and I have about every combination of boards they made.

There have been a few documented instances of that particular resistor cooking, so it's not a totally isolated case.  OTOH, I haven't heard of a definitive reason for it.

I looked at the roughly 20 PS/1 board sets I have, and one has a discolored resistor although it still reads the correct 24 ohm value.  That board works fine when tested on the bench.  It don't draw excessive current or exhibit any other issues, so I'm not sure what causes the excess current at times in that resistor.

@OGR CEO-PUBLISHER posted:

I converted all of my Proto locomotives to BCRs and have never had a problem ... and I have about every combination of boards they made.

All my PS1 locomotives (and 5-volt PS2s) have had BCRs since I bought them. I also use BCR2s in PS2 3-volt locomotives and never have had any problems with either type.

MELGAR

I have used BCRs in all my proto 1 engines with no issues. Do have 2 proto 2 engines with BCRs and no issues. Never have to be concerned about battery issues.

In my testing, I found that a low or discharged battery or BCR,  demand a high current and the circuit cuts back charge voltage to around 2 volts.  As the battery charges and the current drops, that 2 volts or so does not rise, it holds steady, and at a certain point, around 75ma the charge voltage jumps up to the nominal amount in the 9 volt range until the battery is charged.  A full charge still draws a few MA of current.  When you push the direction button on your control, and track volts cut off, the battery or BCR supplies around 300 ma of current to the circuit boards until track volts comes back,  I would guess that most of that current is used by the audio amp.  When you cut off track volts at the end of a run, the audio is still coming until the software decides the track volts are not coming back, and to shut down to save the battery.  Even calculating a dead short of a battery or BCR does not explain the instantaneous burn up.  A 24 ohm  1/2 watt ohm resistor with 9 volts through it to ground/dead short would have to draw 375 ma. to exceed its rating, and I did not see that current level at any time, plus an instant burn up would take much more than 375 ma.  The charging circuit did run normally with a good battery or a charged up BCR, but have been reluctant to try the BCR again after replacing the resistor, plus it did not burn up with a dead 9V, just the discharged BCR.  I did find out that it is the MTH 605, the painted number on the tender was apparently the actual model number, and it is from the 1998 era, but there is not one other number or manf. code, not even stamped with an MTH,  of any kind, inside or out, of loco or tender.  I think this one will have to fall into the mysteries of the universe category, and just move on.

@CALNNC posted:

A 24 ohm  1/2 watt ohm resistor with 9 volts through it to ground/dead short would have to draw 375 ma. to exceed its rating, and I did not see that current level at any time, plus an instant burn up would take much more than 375 ma.

Not sure where you're getting your numbers from, but a 24 ohm resistor with 9 volts across it would be drawing 375 ma, that's true.  However, that is a power dissipation of 3.375 watts, that would take that resistor to the woodshed in a hurry!

@gunrunnerjohn posted:

Not sure where you're getting your numbers from, but a 24 ohm resistor with 9 volts across it would be drawing 375 ma, that's true.  However, that is a power dissipation of 3.375 watts, that would take that resistor to the woodshed in a hurry!

Yes your are correct, I forgot to say that 56 ma is the .5 watt rating of that resistor at 9V, at the low charge volts of about 2 was drawing about 150ma which is about .3 watts, and and when it jumped to 9 at around 70 ma or so, actually the trip point was between 50 an 70 ma on the Simpson 260, that would actually be a bit over 1/2 watt, but it did come down quickly towards 50ma.  The actual charge voltage when it jumped up from 2 was between 8 and 9.  I wondered if the charge circuit initially messed up and put the full 9 volts on the, basically shorted/discharged BCR, and did not downshift to the 2 volt level.  As you noted, if it did fail to switch to the low 2 volt charge voltage, and put 9 on it, your 3.375 watts would smoke the resistor just like it did.  I did experiment with 3 different MTH locos and they all did the low 2 volt initial charge voltage until the current was in the 50-70 range, and then shifted up to 8-9V charge volts.

I've truthfully never looked at the charging circuit to any degree.  It's interesting that it starts with 2 volts, that sounds like they're trying to protect against a shorted battery.  If so, that would also help with the supercap as it looks like a short at first until it gets a charge.  However, going from 2 volts charge to the full 9V charge would still put around 7 volts across a very low impedance load, that being the supercap.  That still gives me 2 watts across that half-watt resistor.

I have a similar charging issue in my YLB - RailSounds Battery Replacement, I start out with a totally discharged 1.5F supercap and apply 5V through a 10 ohm resistor.  That gives me 2.5 watts at the resistor until I get a voltage of at least 1 volt on the cap and it down to 2 watts.  I can tell you that the 10 ohm resistor gets pretty toasty in those few seconds as the cap charges, and I'm only at a max of 125% of the rated power of the resistor.  Dumping 400% of the rated power into a 1/2W resistor, even for a short time, isn't going to be particularly good for it.