Accucraft Excelsior RC battery charging

[tom_tom_go]

Be good to see it running!

[Soar Valley Light]

Hello Tom,

I was hoping to treat you to a video clip of just that. I found time to steam her up this afternoon. Bearing in mind a wheel hasn't been turned in well over three years we got off to a good start. She ran very nicely, even if she did turn her nose up at some of the rougher bit's of my road! It was a new experience driving a loco with separate regulator and reverser controls. It was going so well I was planning a second steaming to record some video. I was getting the hang though when, halfway through the steaming, she suddenly sat down and refused to move. closer inspection revealed that the reverser was in mid gear and not responding to the controller. Once cool I ended up taking the body off and found what I think is a burnt out servo. It's close to the burner but the damage is on the opposite site (if it really is damage - it's the first time I've looked at one up close). I've had a chat with a friend about it and he suggested plugging it into the channel for the regulator control to see if it really is the servo. Unfortunately the advice came just as I was dishing up the evening meal so it will have to wait until tomorrow now. I did try to get a couple of pictures of the damage.

servo 1.JPG (32.6 KiB) Viewed 6294 times

servo 1.JPG (32.6 KiB) Viewed 6294 times

I'm not sure they are very clear but if you look where the wiring loom joints the servo body you can just make out that things seem to have been hot and the front right top corner of the server seems to have 'ballooned out' slightly.

Andrew

[tom_tom_go]

Your friend has made a good suggestion, try that to see if the servo is faulty.

[Soar Valley Light]

Well, things have moved on, but not for the better. I’m afraid it’s a case of one step forward and one leap back! I tried swapping the servo’s over, the dud remained dud and the good one continued to work. I had a couple of new servo’s that came with the loco so I swapped the dud, switched back on and hey presto! We were back in business, all working. Steam was raised and a trial run began. The handset for this loco has very ‘floppy’ joysticks, particularly on the regulator channel. It has to be held continuously to keep it in the required position. This makes shooting any video footage a bit of a challenge but I did manage some. When I can remember how to do it, I’ll either upload it here of post a link to you tube. So far so good, but this was the end of the step forward.
The beginning of the leap backwards began when the reverser servo stopped working again. I continued the run on the regulator control alone, which appeared to continue working normally. Once out of steam I left the loco to cool and steamed my Ragleth. Old reliable chuffed away quite happily and I took the opportunity to tie the tourist saloon on to see how it coped with the new track (it’s the most ‘picky’ vehicle I’ve got, being a very long wheelbase four wheeled vehicle). All was going well until the servo on the reverser stopped working! I had the strongest feeling of deja-vu! I managed to set the regulator to match the reverser position and continue running. I must have hit the ‘sweet spot’ because it was probably the best slow speed run I’ve ever had, impressive when you take into account that, even on the ‘flat’ section of my line, curves and minor gradient changes make it’s almost essential to keep nudging the regulator one way or the other – or so I thought! I’ve had the Ragleth for 7 years, it’s only had about a dozen runs in that time and came to me second hand so I’ve no idea how long the batteries had been in there but I’d never changed them in all that time making it a fair bet they were the cause. So the second loco began cooling down for attention!
Meanwhile the Excelsior was cool. An inspection revealed no damage to the new servo that I could see from the cab. I switched the electrics back on and nothing….. nothing at all. Both servos were lifeless and the light on the magic box on the loco wasn’t lit. Given what had just happened with the Ragleth I wondered if the batteries had lost their charge very quickly, given their long period out of use without a charge. Suspecting I may need to replace them I decided to recharge them and see if there was enough life in them to test the servo’s. I also stripped the now cool Ragleth and removed the batteries from that too. I plugged the Excelsior into the charger and put a set of rechargeables that I use for the Christmas lights on charge for the Ragleth. (I’m not planning on putting up the Christmas lights any time soon!!!). When I went into the kitchen at about half past nine last night I noticed that the Excelsior was charged. I could resist seeing if there was any life. I switched on, reached over for the controller, got it out of its box, switched on and turned back to the loco. It all took no longer than it took you to read the last sentence, but to my horror there was smoke pouring from the cab off the wiring loom. One of the things I’d done when changing the servo was move the wiring round the cab door side of the oil filler to keep it as far from the burner as possible (ironically!) this put the plug coupler from the battery to the switch in the cab door way. I grabbed it to unplug it but it was hotter than I expected, the wiring was just on the point of melting and came away (stuck to my finger and thumb!). I’m not sure at what point I flicked the switch to ‘off’, I think I did it immediately I saw the smoke but I can’t be sure. However, the batteries were definitely disconnected now because one of the wires had parted. I could hear the batteries starting to fizz and there was still plenty of smoke from the wiring so I quickly shot the loco out onto the back yard and retired to a safe distance. The smoke was subsiding now but the batteries continued to fizz for a couple of minutes more. It was dark by this time and I wasn’t about to start investigations at that time of night so I threw a box over the loco and left it until this morning.

First job today was to try the Ragleth with the recharged batteries I’m pleased to say all was good there, everything came back to life. The excelsior was a sorry sight though. The battery plug coupler was completely melted and the wiring from it back towards the switch was melted, it had also heated up and melted the cables from the reverser servo and warmed up the cable from the regulator servo to the extent that the insulation was damaged in two places where it had been resting against an edge. I took the batteries out and they are clearly fried. I cut the battery lead at the end of the damage to release them. Clearly extensive work is going to be needed to recover for this situation.

Wiring damage.JPG (30.85 KiB) Viewed 6272 times

My first question is whether there is any means of jointing a new connector onto the end of a cable. This would save the two servo’s and avoid the need to strip out the on/off switch from the bunker (which looks like it’s easy to remove and a complete so-and-so to put back). If not, it looks like a complete new electrical system will be required. I’m not sure I fancy the expense of that! What worries me more is the chance of it recurring, especially as I’ve got no idea what caused it in the first place. Any suggestions would be gratefully received, but please bear in mind that I’m a technical ‘numpty’, explanations in words of one syllable (at least technical words) will be the most useful for sure!

[GTB]

My first question is whether there is any means of jointing a new connector onto the end of a cable. This would save the two servo’s and avoid the need to strip out the on/off switch from the bunker (which looks like it’s easy to remove and a complete so-and-so to put back). If not, it looks like a complete new electrical system will be required.

Hooley dooley......................

Well, you just found out the hard way that rechargeable batteries have a high energy density and a low internal resistance. This means the only limit on the current delivered is the resistance of the wire, which rapidly turns into a heating element when shorted, until it melts and becomes a fuse.

The odds are that the wiring insulation was either already damaged, or was brittle and was damaged when you moved it around. There are a lot of sharp metal edges that get hot in little steam locos. Once the insulation breaks down and both battery wires are bridged by metal, bingo.

It could have been worse, NiMH cells get very hot when shorted and can go bang, but aren't particularly flammable. The fizzing noise was the electrolyte in the cell boiling and the steam escaping from the vent in the casing.

Yes, servo connectors can be replaced, but not easily. A good r/c shop will likely stock spares and if they have a repair service, the repairer will have the special crimper needed to wire the connectors. The crimper is expensive, so not really a DIY option. I have fitted JIS connectors to leads without using crimper, but it's a real pain in the nether regions.....

The biggest problem at present is that with the virus shutdowns there probably aren't any places open that can fit a plug for you.

To be honest if it was me, I'd probably rewire the loco, as the wiring is now suspect and other bits of electrickery may have suffered damage in the incident. The switch contacts may have been damaged by carrying the full current and the Rx and servo electronics may not be happy little campers either.

I have fitted a suitable size polyswitch fuse between the rechargeable battery and the switch in my r/c and battery electric models to reduce the likelihood of this type of incident.

Regards,
Graeme

[LNR]

I switched on, reached over for the controller, got it out of its box, switched on and turned back to the loco.

Hi Andrew, sorry to hear of your problems. If I am reading your statement quoted above correctly you turned on the receiver in the Loco, then got to the controller (Transmitter) and turned it on. If that is the case it may be the source of your problems. You must turn the transmitter on first then the receiver otherwise the receiver has no signal to set the position of the servos and they go anywhere or at least try to. If there is a restriction they will just fry.
If I've misunderstood your statement then please ignore what I have said.
Hope you are able to get things going again.
Grant.

[Chris Cairns]

Hi Andrew,

That is incredible bad luck.

You can get plugs for servo wires, but an easier option is to get a new male servo lead & solder splice it onto your current servo leads?

I would definitely renew the switch harness (if you remove the receiver from the bunker you should be able to hold a new switch in place whilst getting the first mounting screw done).

The steam pipe coming off the lubricator to the valve block is very adjacent to the reverser servo and the power leads. I would recommend using some sort of cable clip to hold your leads away from the steam pipe, lubricator, etc.

Component Shop are still doing mail order so could be a source of all your needs including a new battery pack.

https://www.componentshop.co.uk/futaba- ... rness.html

https://www.componentshop.co.uk/jr-hite ... -male.html

https://www.componentshop.co.uk/small-s ... clips.html

Chris Cairns

[Soar Valley Light]

Thanks everyone for the help and advice. The sympathy is just as welcome too!

I feel a rewire might be the order of the day, my only worry is that there might be something in the receiver that's causing some or all of the trouble. Changing that as well takes well out of my comfort zone!

This sort of support and advice is one of the very best things about this forum.

Andrew

[IanC]

Andrew,

Sympathy I can do. Electrics are also a mystery to me so I can't help. I have a Caradoc which I am trying to sort out. It's running deteriorated quite markedly last year and I change or replace one part, only to find it shows up a problem in another area. Like you, one step forward and one backwards. A short gas burn time and a lack of power are what I have been addressing, but I haven't had to sort out any electrics, although I have replaced the r/c receiver so can control the locomotive using my existing OMNI transmitter. Whilst it is frustrating (And expensive) it is also proving to be a useful learning exercise. Take it slowly and step by step. You'll get there. My Caradoc is now awaiting a new burner which, fingers crossed, should see the final chapter of my saga.

[FWLR]

Andrew,

Have you not got in touch with ge_rik and Phil RC Trains, both of this parish. They would I feel, be the people to help with your problem....

Electrics... Nightmare for me also....

[GTB]

I feel a rewire might be the order of the day, my only worry is that there might be something in the receiver that's causing some or all of the trouble. Changing that as well takes well out of my comfort zone!

We all need to push the boundaries of our comfort zone now and again. Just ask for help with anything you are uncertain about and you'll get there.......

Once you've got the new wiring loom, test the various parts on the bench with ordinary dry cells, before installing things in the loco. These cells have a high internal resistance and can't deliver enough current to get things hot in a hurry.

Don't use alkaline cells, they can deliver a lot more current than the ordinary type and definitely don't test with rechargeable cells until you know everything is working. Some r/c electronics can get funny about running on 6V, so use three dry cells, not four.

Chris's advice to splice on new leads is a good one, but make sure you use shrink tube to insulate the joints, not tape. Tape won't last long in the heat of a live steamer and you'll be back where you started.

So, connect up the receiver first to find out if the magic smoke is still inside. If that looks OK, try a spare servo in each of the outputs. I'd try a known good servo first, before you try a repaired one, so you aren't chasing two possibly faulty devices at once.

If that all works on the bench, you can then start installing it back in the loco.

If you get the right wiring loom it should be 'plug and play'. Just take notes and photos as you remove parts from the loco so you have a reference for when the time comes to replace them. Your other steamer should also be a useful reference as you go.

Regards,
Graeme

[Soar Valley Light]

Thanks again guys,

There's no progress to report as I've been 'off colour' for a couple of days. Annoyingly, as I'd taken a days leave today to extend the bank holiday. It's back to work tomorrow and I'e got bean plants coming through now which need planting out so it looks like the project will have to wait for a day or two.

I'll keep you posted when there is some progress.

Andrew