Wiring 4QD controller for 4 motors.

Hi, in the wiring diagram of the 4QD DNO-10 controller it shows the two terminals for the motor. But how would you wire up 4 motors each being 12volt. Do I wire the motors In series or parallel. Or sure I split the power take off at the 4QD terminals and wire the motors in pairs as it’s two motors per bogie. Which is best.

Is this the arrangement you're using?

https://www.4qd.co.uk/docs/dno-pro-vtx-series-controllers-wiring-for-push-button-use/

Edited By Ady1 on 25/07/2023 23:16:05

Hi, no, I have two 12v battery’s and 4 x 12v motors.

if you wire the motors in series you will reduce the voltage across each motor to 25% of the boards output (based on identical motors). Putting them all in parallel will put the board's output voltage on each motor but will increase the output current fourfold over one motor (same caveat). A hybrid of two parallel motors in series with another two in parallel will halve the voltage on the motors and keep the output current the same as a single motor.

So if you have four 12 volt motors in series on a board with a maximum output voltage of 36 volts the motors would be expected to only be supplied with 9 volts. Possibly not what you want.

If you put the 4 motors in parallel then supply them with 12 volts and they all draw 25 amps inrush current then the board, wiring and power supply would have to be able to cope with 100 amps for a short time.

Answering "what is best? " is dependent upon what load the motors will have to overcome, the power supply being used and how much stress you are willing to subject everything to. The stress is related to how close you want to take things up to maximum rating for the system and for how long they would be subject to this stress.

Martin C

Just read you are using two 12 volt batteries. Put in series these will give 24 volts and so two pairs of parallel motors in series will give 12 volts across the motors if the 24 volts is on the output terminals.

Edited By Martin Connelly on 26/07/2023 08:39:24

Take a look at the 4QD site ...

This shows 4 Motor wiring in regards to supression - Link

and comparing Serial/Parallel - Link

Ride-on-Railways put all 4 motors in parallel [As 2 pairs .. so 4 wires to controller]

Dave

As the 4QD site says there can be issues with motors in series. This is due to the voltage/speed current/torque charateristics of DC motors. The the voltage should split by the ratio of the speed and current by the ratio of torque. for a ideal motor but there is no ideal motor and it is difficult to get balanced torque. So in practice one motor will try to run at high speed. Worst case if you stall one motor of two 12V motors in series on a 24V the other (unloaded) motor will overspeed as it will almost all the 24V supply voltage. This will exceed its 12V rating. It's a bit like a differential on a car when one whell losses traction. If the two motors output shafts are linked it will generally help with load sharing. It will still depend on the specific motors though.

The easy answer (assuming the controller has enough current rating) is batteries and motors in parallel. This is a 12V system. The other option is batteries in parallel and two pairs of serial connected motors in parallel. This is a 24V system. You would have to try the 24V system and see how your motors work.

Robert.

As I read the manual, the DNO 10 is only intended to drive a single motor. Section 13 'Expansion Connector' explains how to connect controllers in a master slave relationship: in this configuration one controller tells another, one per motor, what to do. Again as I read the manual, only two motors.

At risk, one could run 4 identical motors off one controller.

The DNO 10 spec says:

• 12V to 36V
• 100A Peak
• 75A for one minute
• 60A continuous

The most important limiting factor is 60A continuous. Whatever is connected to the controller must not normally draw more than 60A. (Starting an electric motor briefly draws more than it's rated power. to accommodate start surges the DNO 10 controller allows 100A peak provided it drops immediately to 75A for no more than one minute.

Assuming it's big enough (see capacity below) a single 12V battery would power a single big 720W motor (12V x 60A) or four smaller 180W 12V motors in parallel: 720W total, 180W per motor, 15A each.

Two 12V batteries of the same size in series, or a single 24V battery, doubles the amount of power available:

1. a single big 1440W motor (24Vx60A) or:
2. four smaller 360W 24V motors in parallel: 1440W total, 360W per motor, 15A each. OR
3. four smaller 360W 12V motors in series-parallel: 1440W total, 360W per motor, 30A each leg.

Various pros and cons. A single motor means a drive train is needed, maybe not a disadvantage if a gear-box is needed. High amperage wires get hot and waste power, so have to be made of thick copper in short runs. 60A is more trouble than 30A and 15A is ordinary. 12V batteries and motors are a bit easier to source than 24V etc.

The risk that two or motors motors could present an unbalanced load to the controller may explain why 4QD's manual doesn't cover more than one motor per controller. A vehicle should put the same power on all the drive wheels, and bad things happen electrically and mechanically if one or more wheels slip or stall. A professionally designed vehicle would allow for this, which my simple multi-motor suggestions above don't. My feeling, and I have no direct experience, is a hobby designer, driver, or club insurer need not get into a flap about balance. 'Our' electric locos are relatively slow and unlikely to get out of balance on a Club track - we're not building full-size locos required to reliably haul huge loads of iron-ore over snow-filled mountain passes!

Battery Capacity is measured in Ampere Hours. 12V Car Batteries range from as low as 30AHr to about 120AHr. In theory, a 60Ahr battery would power a DNO 10 flat out for an hour. In practice rather less, 80% or 48 minutes max. Worse, a car battery used for this purpose will have a short life - not many recharge cycles before it fails to hold charge. The problem is car batteries are heavily optimised to deliver a few hundred amps for a few seconds into a starter motor; once the engine is running, the battery takes about 15 minutes to recharge, after which it has a long rest! This type of battery is rapidly damaged by repeated deep discharge and long recharge cycles, and particularly by doing it once a week on a loco! The battery will work, but expect it to die quickly.

A Leisure Battery is a better bet because they're designed for repeated deep-discharges. But for a long life (more than about 500 cycles) even these are best not discharged below about 50%. There are also lead-acid batteries specifically made for fork-lifts etc, which perform better than caravan batteries, but are expensive. I've no experience of them but Lithium Batteries outperform lead-acid types. Although they last much longer, the purchase cost is high. I guess for hobby use an inexpensive Leisure Battery will give best value for money - reasonable life and performance without costing a fortune!

Again, I feel the designer of a hobby loco, needn't fret too much about about how many battery recharges he'll get, or exactly how many hours his loco will run for on a single charge. All that's needed is that the loco start and stop when required. It doesn't have to meet commercial cost-benefit targets over a wide range of operating conditions.

Anyone with practical experience of building one of these? I've no idea what the total weight might be. Would four small motors need a gear box or belts to improve torque, or can they drive the wheels directly?

Dave

The controller will drive multiple motors as long as you don't exceed the current rating (As stated in previous posts). Maxitrak drive multiple motors from 4QD controllers .... The manual only shows 1 motor for simplicity.

Here is the wiring for a 2-Bogie loco (Each with 2 motors) - So 4 motors in Parallel

Please ensure that you wire the motors so they all rotate in the same direction. (You may need 1 running forward and 1 running in Reverse on each bogie if 1 drives on the left and 1 on the right!)

Edited By Steambuff on 26/07/2023 11:26:59

According to the interweb, whether in series or parallel, the two batteries should be the same Ah capacity.

If you have the money and space then trojan 105 traction batteries BUT they are 6V or 8V so its 4 or 3 units to give 24V or 2 X 6v for 12v. Noel.

All sort now, thanks