Graeme,
Sounds much like the batteries may not be performing up to specification to me… You mentioned you were cycling the batteries what was the outcome of said operation. How many cycles? Did the cycles include full charge/discharge cycles, what was the mAh capacity realized after the last discharge cycle? Are these new cells, do they have experience and a known performance record?
Michael
OK there is a Bonehead on the forum!!!
And that would possibly be ME (not that I am going to admit that in public (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-undecided.gif)(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-undecided.gif)).
This afternoon after coming home from work, I tried the dead loco on the bench and it worked just fine.
After much head scratching and deep thinking I looked over the wiring again and found that I have wired a 1.85A polyfuse (used for battery charge protection in the original install) into the battery to ESC line.
The clue was that when the loco stopped it would jerk instead of just slowing down to a stop and would try to start again but stop almost immediately
Now call me stupid (please don’t as my pride is really delicate at the moment) I reckon that drawing over 1.85A through a ployfuse might make it trip DOH!!!
I plan to finish work before dark tomorrow, disconnect the polyfuse and see how it goes.
My guess is that all will be fine.
If it all works out fine I will put this down to experience and look closer before shooting from the lip. (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
But on the upside I have learned a lot about batteries and charging so maybe a bit of embarrassment was worth it so thanks for the help.
Good news Graeme.
That explains it.
Don’t give the Polyswitch idea away entirely. Always good to have protection.
I use RUE 3 amps for bigger locos such as the Shay.
If speed of tripping needs to be faster try using 3 x 1 amp versions wired in parallel.
I use these to save my wiring. I use them in pairs mounted in parallel.
http://www.allelectronics.com/make-a-store/item/cpx-100s/resettable-circuit-protector-1a-2.5a/1.html
But these would probably work as singles.
http://www.allelectronics.com/make-a-store/item/rue-250/2.5-5a-resettable-circuit-protector/1.html
Interesting Todd, if they sef reset, I would really consider them vs. Polyswitches.
The polyswitches do heat under their rated load, and don’t shut down quite as fast as I would like. They are cheap enough to really put them in all the places needed if you want to protect all the wiring of a loco, and I did find a series of fast acting PolySwitches from Raychem.
I will have to look up the characteristics, but I would appreciate your experience and opinion.
Greg
Yes, the 1-amp units self reset when the power is removed for a few moments. I haven’t tried the 2.5 amp units as they are new fare and I have plenty of the others already.
Well the polyfuse is not the culprit (guess I’m not a bonehead after all (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)) so I will now start disconnecting bits till I find the problem.
What is confusing me is that when I had a 14.4V 5000mAH LiPO battery connected, the loco worked fine all I have done battery wise is change the chemistry of the batterey.
I have added a relay switch to drive a couple of LEDs but can’t remember if that was after I changed battery types so that is the next thing to eliminate, after that its the original setup ESC wise, so where to from there I do not know.
Another ESC may be.
Graeme,
Are you convinced the NiMH batteries are not the problem? Did you validate the batteries are performing up to specification subsequent to your cycling exercise? If all works well with another power source, I’d be looking very hard at the batteries.
Michael
I am seriously looking at the batteries and suspect they are not up to the task with this loco.
The ESC manual describes the symptoms I am getting as being caused by depleted batteries but I am measuring 15.06V on each packs even the loco will not move.
The other confusing thing is that I use packs made from the same cells in LGB locos with no trouble, but the glaring difference is that they only have 1 motor and not 3 wired in parallel.
This loco worked fine with a 14.4V 5000mAh LiPo in it but just does not like NiMH.
Thinking its back to LiPo/Li-ion to get it to work.
The relay removal did not change anything so it is out for the equation so I am back to either the ESC or the batteries and I am betting on the batteries being the problem.
Graeme,
If the problem was not a Polyswitch not holding, I can guarantee you it is the AA size NiMh cells. They cannot handle 2 amps and survive for very long.
If the packs had been joined in parallel I think they could handle it. But not as individual packs.
Most AA cells are designed for a max 1/2 amp draw for a long time. Not 2 amps for a short time.
As a matter of interest how old are the NiMH cells in terms of re-charges they have had.
Was that 15.06 volts measured under load?.
Tony Walsham said:
Graeme,
If the problem was not a Polyswitch not holding, I can guarantee you it is the AA size NiMh cells. They cannot handle 2 amps and survive for very long.
If the packs had been joined in parallel I think they could handle it. But not as individual packs.
Most AA cells are designed for a max 1/2 amp draw for a long time. Not 2 amps for a short time.
As a matter of interest how old are the NiMH cells in terms of re-charges they have had.
Was that 15.06 volts measured under load?.
The 15.06V was measured with no load.
I am not sure of the exact current draw but I am thinking it would be somewhere in close to 2.4A, working on 0.6A per motor and 0.6A for the ESC.
So I am guessing that I am just sucking the life out of them.
The batteries are brand new, bought for the conversion, and have been charged once and cycled (auto discharge/charge on battery charger) once.
That would explain why the LiPo was not effected.
So back to the drawing board, standby for a result in the future.
$10 will buy you a meter, you can measure the amps and eliminate the guessing.
Greg
Graeme,
Again, it sounds like the problem is your batteries. NiMH batteries need to be formed and or cycled multiple times before they are able to provide rated capacity… I’m speaking from the voice of experience herein, these cells will come alive down the road and reach the rated capacity, each cycle will net better results.
Utilize your charger to soft peak charge the batteries at 1.0A and discharge them @ 1.0A to 0.8V per cell or 9.6V, rest the batteries and start all over.
Your Turnigy Accucel-6 has a break-in cycle algorithm for this very purpose, it will show you the average voltage, mAh charged/discharged, elapsed time and more. As I recall you can set your Turnigy charger to perform 3 complete charge/discharge cycles automatically. Everything you need to evaluate said batteries is within reach.
A voltmeter as Greg suggests will work nicely to measure the current draw at these levels and eliminate the unknown.
Michael
I usually charge my 2700mAH batteries at 0.3A.
I only used the charger cycle the charger is capable of 5 cycles.
The current draw was an estimate based on Don Sweet’s figures of a Climax drawing 1.0-1.1A which I translated into approx. 0.6/motor the treated the electronics (ESC, Rx, BEC and the relay switch) as the equivalent to another motor ie 0.6A.
Connecting my Ammeter into the circuit was a job for this weekend when I can find some spare time. I am planning on measuring loaded and unloaded current while monitoring the voltage when under load.
If the battery voltage drops significantly under load of the locomotive, then it is your batteries which cannot handle the continuous load.
Graeme, my repeated admonitions to measure the current is because often a loco can appear to be running fine, while using an abnormal amount of current.
If you have a physical load that takes .6 amps to move, putting 2 motors in the same loco with the same load does NOT pull 1.2 amps total.
This is a common misconception, and I’ve been on forums for years, and it never ceases to amaze me that people will speculate about something when an actual measurement can be made easily.
When you have the actual current draw under load, everything will become clear.
Regards, Greg
p.s. I realize this might read “harsh”… just trying to save you time, and you were sounding a bit frustrated, I’m trying to minimize that frustration.
Greg Elmassian said:
This is a common misconception, and I’ve been on forums for years, and it never ceases to amaze me that people will speculate about something when an actual measurement can be made easily.
Regards, Greg
Where’s the emoticon for LOL on this site?
Graeme Price said:
I usually charge my 2700mAH batteries at 0.3A.
I only used the charger cycle the charger is capable of 5 cycles.
The current draw was an estimate based on Don Sweet’s figures of a Climax drawing 1.0-1.1A which I translated into approx. 0.6/motor the treated the electronics (ESC, Rx, BEC and the relay switch) as the equivalent to another motor ie 0.6A.
Connecting my Ammeter into the circuit was a job for this weekend when I can find some spare time. I am planning on measuring loaded and unloaded current while monitoring the voltage when under load.
A simple way to connect an ammeter, is to just connect it across the open on/off switch. I place the ammeter in a open wagon (with a few rubber bands to ‘control’ the leads. Then I can follow it around checking amps on grades and curves too.
I have a battery pack that was built as a 16.8 V 3000 mAh battery (Nicad) by the local Batteries Plus, but on close inspection is really two 8.4 V batteries wired in series. I’ve always charged them together as a 16.8 V battery, but now I’m uncertain.
Ideas? Suggestions?
