Making battery accessible for charging

[ianb3174]

I have a Deltang Tx22 controller, Rx 41d-22 reciever and 3.7v battery for installation in a loco for testing. I opened up my Heljan Class 14 to find very little room inside. I was concerned that removing the body for recharging wasn't viable on a regular basis. I'm going to instal in my Class 24 which has acres of space. Does anyone know of best practice in fitting an external charging port? Ideally underneath the battery box. It's no issue to remove loco from tracks as this is normal after an operating session so I don't need charging from rails, just a small socket to connect the balance charger. Is there a thread/diagram/website with a schematic that can be recommended?  

Absolute beginner in RC btw

[Simond]

Ensure you use a charger suitable for Lithium batteries.  

As you’re working on 3.7V, you have only a single cell (or cells in parallel) and balancing is unnecessary, though I imagine your loco is rather slow, and can’t pull much.  I’m using 2S & 3S batteries, which do need a balancing charger (3 and 4 wires respectively), but give a higher voltage to the motor.

 (Don’t just charge with the + & - as you would with a car battery!) 

 

You can fit any suitable, polarised, socket, anywhere convenient on your loco, and make a lead to connect to your charger.  Make absolutely certain that you connect it up correctly!  And equally, that you cannot inadvertently connect it up incorrectly!

 

Most definitely fit a switch that isolates the battery from your receiver, and ensure you turn it off, or the battery will discharge to a level where it cannot be recharged (safely).

 

hth

Edited May 3, 2022 by Simond

[PenrithBeacon]

My diagram, hope you find it useful. 

[ianb3174]

Super, thank you both.

I have a balance charger and loco will be not pulling much more than 3 wagons on a shunting layout. I can always add more batteries as necessary if it's not up to the task. 

Am I right in thinking the SPDT switch toggles between the charging and operating states? So that would be best sited near the charging point? 

With adding extra batteries is that better in series or parallel? 

Also do the plethora of running lights on RTR diesels reduce the battery capacity significantly? 

 

[Simond]

A single cell does not need to be balanced.  When you add more cells in series, you must balance them during charging, so that they are all the same voltage - they won’t “share” the supply fairly, so they need the balancing charger.  You cannot use the above diagram with a multiple series cell arrangement, but it’s fine for a single cell.   You can hide the switch wherever convenient, the electrickery doesn’t really care how long the wires are!
 

Adding cells in series will give a higher voltage, which will give you more speed, but it will also help haulage capacity.  Imagine turning the voltage up on a conventional dc analog controller.

 

Adding cells in parallel will give you extra run time, it would also help haulage capacity, but only if the cells were the limiting factor, which I would not expect to be the case.

 

lights won’t have much effect on the run time, particularly if they are LEDs which take very little current.

[PenrithBeacon]

You have a motor which is rated for 12V but a battery whose maximum output is 3.7V . Fi rst check that the battery will power up the motor. If it does no problem, you probably won't want the loco to move at its maximum speed anyway. Maximum speed on a 3.7V battery will be a little less than 1/3 of the theoretical maximum. Usually this doesn't matter. 

Measure up the space into which your battery has to fit and go online to eBay and find the largest 1S (ie single cell) battery can find that will fit. That's the one you buy.

I get all my stuff from Micron you can buy everything already wired up. Easy peasy.