# LGB F7 + Aristo Li-Ion battery = problem?



## acmartina (Jan 6, 2008)

Hi,

I seem to be having an odd problem. I have a LGB F7 that I have run for several years running successfully with various power sources - most often a 14.8v Li-Ion pack (BatterySpace.com). It runs fine but is a bit underpowered at 14.8v, so I thought I would try the Aristocraft 21.5v Li-Ion packs. I have a pair of them wired in parallel that I use regularly to power larger Aristocraft locomotives (GP40, SD45, single or double-headed) with long run times and no problems. But when I use them with the F7, the loco periodically stops dead, as though a polyswitch had kicked in. 

The batteries are not warm to the touch. I am not aware of any polyswitches in the LGB F7, nor have I ever had it stop under any other circumstances. My AirWire has a voltage regulator to handle the higher voltage - I use it with the same batteries with the Aristo locos with no problems. The only thing I can think of is the polyswitch on the battery PCB. But I don't think the F7 is such a current hog, particularly with the relatively high voltage. The 14.8v packs have polyswitches too but have never kicked in. I would have thought a single 14.8v pack would be much more susceptible to overdraw on current that a pair of 21.5's. I would also expect the GP40 + SD45 doubleheader to be much more of a draw.

So in summary,

Aristo GP40 or SD45 + AirWire + Aristo Li-Ion = Success. 
LGB F7 + AirWire + 14.8v = Success
LGB F7 + TE + 18v = Success
But LGB F7 + AirWire + Aristo 21.5v = Failure









Appreciate any thoughts.

Thanks,
Steve H.
Cypress, TX


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## Torby (Jan 2, 2008)

Tell me about this regulator. If I recall, Airwire doesn't like any more than 16v, so your regulator is dropping 5 or 6 volts times the current you're drawiing. Without a good heat sink, it's going to get hot and may have a thermal shut down feature that's turning your loco off.


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## Greg Elmassian (Jan 3, 2008)

I'm with Tom... 

Greg


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## Bill Swindell (Jan 2, 2008)

Which AirWire receiver are you using? There are 3 different ones. 

Oldest - 18V max DC input 
Middle - Split power supply capable. 
Newest - G2 model will run higher voltage without any other circuits 

If you are using the oldest one with a regulator to control the input voltage to the board, your regulator is probably shutting down because of too much current through it. 
If you are using the middle one, what is the voltage that is coming out of the regulator? 

By the way, I did a locomotive with a regulator and the Aristo battery and a regulator. It works fine.


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## acmartina (Jan 6, 2008)

Thanks. The Airwire is the split power supply variety (middle generation). As I understand it (not an electronics whiz!), there are two sides to the unit - the high voltage side that supplied power to the loco and can be up to 26v or thereabouts. Then there is a low voltage side that powers the low draw accessories like sound, lights, etc. This isde has an 18v limit orit fries the electronics. So you can get > 18v on the high voltage side if you use two batteries in series. Only the first battery supplies the low voltage side, keeping it under 18v.

So the 12v regulator that I added limits the low-voltage side to 12v regardless of the battery. The current draw on the low voltage side should be quite low. Sound and lights are not affected by weight of train, grade, etc. It does not affect the high voltage side so heat sink should not be required. I am not actually running anything off of the low voltage side in this case (no sound, lights, etc) - just power to the loco.

I take no credit for figuring this out. The modification is something I picked up on MLS a few years ago. Credit to Jim Agnew and others.
http://www.mylargescale.com/Community/ForumArchives/tabid/100/Default.aspx?TOPIC_ID=40128

There is a good photo of a simple way to do it posted by John J in the following thread, about halfway down.
http://www.mylargescale.com/Communi...C_ID=44182


Thanks,
Steve


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## Greg Elmassian (Jan 3, 2008)

Can you measure the battery output and the regulator output when it quits? You could just add 3 wires to bring the voltages out if it is way inside the loco? Can you run the loco without the shell to measure this when it happens? 

Regards, Greg


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## Trains (Jan 2, 2008)

Steve,

I run my LGB A-B-A with the split A/W and a 18 volt millawkee drill battery with no problems.


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## acmartina (Jan 6, 2008)

Don, Thanks. I have done the same with an 18v Ryobi battery without a problem. So good question to ask is - Has anyone run the LGB F7 with a battery greater than 18 volts (with any R/C system)? Greg, Thats a good idea. The Airwire and battery are in a trailing car so its an easy check. However, it looks like rain, so we will see if we get out ahead of it! I do not believe the regulator is an issue for a couple of simple reasons - 1) it runs fine with other batteries and other locos, 2) there is no load on the low voltage side that would pull any current across the regulator. The power to the loco is in parallel to the regulator, so I would think it would not be affected. However, I will run the check to verify. I also have another Airwire trailing car that I can swap out as well. 
So assuming for the moment that the regulator is a red herring, it seems to me the issue is either - 1) the F7 has a problem with 21.5 volts (but not 18 v), or 2) the F7 does something funny that fakes out the Aristo battery's protection circuit. I can't see how the Airwire is an issue. Any other F7 battery runners out there?







Thanks, Steve


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## Trains (Jan 2, 2008)

Steve,

I think LGB trains are made to run on 22 volts so the voltage should not be a problem. As long as you have some way to control the voltage you should be able to run as much as you want as long as it dose not reach the motors. Maybe the Aristo batteries are shutting down? Don't know not a big Aristo fan!


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## Dan Pierce (Jan 2, 2008)

Where do you attach the battery inthe F&? 

I ask as if the battery is attached to the 2 wire connector on the B unit, there is a poly switch on many LGB circuit boards now to protect the wiring inside the engines to passenger cars.


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## acmartina (Jan 6, 2008)

Dan,
Thanks. I did not think of that. Yes, it is connected through the two-wire connector at the back of the B-unit. I will pop it open and have a look. Appreciate it! 
Steve


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## Trains (Jan 2, 2008)

Steve,

What did you come up with on your problem??


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## acmartina (Jan 6, 2008)

Hi Don,

Nothing I'm afraid. I disassembled both units and found nothing that looks like a poly-switch. I took some photos of the various circuit boards with the intention of posting them here to see if anyone else recognizes something. Then I got sidetracked by the holidays!







Will do so when I get back home. Visiting the great north woods of Wisconsin for a week or so! Merry Christmas!

Steve


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