Amperes - friend or foe

[Jerry Carducci]

Hello all.

Still attempting to wrap my little brain around the power requirements of the larger models. I'm making good progress on my King Tiger
and presently I want to test install the motors, electronics, batteries. Once I finish the lower hull and apply zimmerit (ugh!); after that I'm going to have to rely on the thing moving itself around while I finish it.

I'm going to make up a control box, similar to the one I showed elsewhere and it's time to pick the circuit breaker.

From what I'm reading I hear fellows building similar models are using as much as 60 amp circuit protectors on the main? 60amps
concerns me I won't mince words. The XT90 connectors are rated at 90amps max (but who knows for how long) but other components specifically
switches may not be able to handle more than 20 or 30 amps.

So while I'm willing to go with a 50 amp circuit protector I'd prefer to stay with 30 or 40 and hope for the best. I don't want my KT to shut down
every time I attempt a hill or churn up dirt due to a tripped CB but that is still preferable to having worse. I should say that while I've never got them stuck in mud or caught churning dirt I've not had a problem with either my M3 Lee or SdKfz 7 And they're using 30amp and stock protection respectively.
(Yes I never added additional protection to my 7). This will be useful as I move on to my JT and other heavies...that will be using far more powerful
batteries than my SdKfz 7.

So what say you? What is the optimal value for a circuit breaker?

Jerry

[Paul Sparkes]

In our JT I have a 24v 36ah lifepo4 battery.
I run a 60 amp circuit breaker with custom electronics through out.
Using AT motors on the flat it ran at around 6 amps on telemetry.
On other motors I have seen over 70 amps when heavily tested.

[Gerhard Michel]

Well, I think it is familiar to this forum that I use telemetry in all my vehicles; with various motors and weights. So I can say that there is a very wide range for power consumption; starting at 5 amps in the flat and reaching 60 amps in some exceptional situations like towing another tank, a person in a wheel chair (uphill) or even things like a car. My steel track links also cause high power consumption when tableturning.

Excluding the towing situations all loads are momentarily; therefore even a 30 amps breaker with inert characteristics will not fall. So I'm meanwhile using only one of my two 30 amps circuit breakers when driving around (the flip switches top left).

[Adrian Harris]

How long is a piece of string ?

How grippy are the tracks, how heavy is the tank, how heavy are the batteries, what surface is it running on, how is it being driven, how well was it built, how well has it been maintained ?

I'm putting telemetry into all my tanks now and am surprised at the results. The King Tiger uses less current in a straight run than the old Sherman. Both have the older style Parvalux motors and gearboxes. A steady turn on grass in the KT uses 30A. But that's without the 4A of power use of the smoker elements or the turret turn motor. I log the max current used on the telem screen on the Taranis and it's unusual to see it any higher than 30A, but I do try and drive in a realistic manner.

When I was trying out different speed controllers in the JagdTiger, I could log up to 90A doing neutral turns on grass using a pair of 32Ah AGM batteries.

My plan is to fit blade fuses as the link between the batteries and work up to a value which will run in normal situations but blow if there is a short, or an unexpected load such as a stone stuck in the track.

My go-to tank for shows used to be the T-34. That is a relatively light model, with large flat tracks giving low ground pressure and a 15Ah LiFePO4 battery pack. It would very occasionally blow the 30A fuse in the silver Power Module which fed the Speed Control Module.

Adrian.

[Jerry Carducci]

The track resistance is something I'm keenly considering. My Lee doesn't have exceptional traction with the hard plastic track pads but in a hard turn it can chew up the earth with the best of them.

On My KT and JT I plan to at least sometimes run steel tracks so I know just that will demand more effort.

I've ordered 50 and 60amp circuit breakers. I have some 30amp versions somewhere. I'll likely start low and work my way up. I also may start with automotive fuses.

I don't plan on pulling cars or people up hills! Not unless someone bribes me with the mother of all ice cream cones...

Jerry

[David Merritt]

From an electrical point of view the main circuit breaker is there only to provide protection to the wiring and the components making up the wiring and should be rated to protect the weakest component within the wiring infrastructure. It is not there to protect any of the electrical equipment (motors etc.) connected to the wiring infrastructure. this protection device should be as close to the power source as possible to provide full protection in the event of a failure any were within the main wiring infrastructure.
The final wiring providing power from the main infrastructure to the electrical components (motors etc.) should be of sufficient cross sectional area to enable it to carry in excess of the maximum required current to the connected electrical component (motors etc.) and should have a circuit protection device of a size that will provide protection to the electrical component (motors etc.) and the wiring to prevent the electrical component and wiring failing under excessive current draw. This protection device should be a the start of the secondary wiring system to provide full protection in the event of a failure any ware within the secondary wiring.

David

[Gerhard Michel]

Just a hint: I didn't measure Parvalux or Spiradrive motors till now, but the 350 w Unite motors used in Bigtanks models and some scratch in 1/6 scale builds have a peak power consumption of 114 amps per motor. This will kill the motor in seconds...

[Gian Marco Menozzi]

HI Jerry,

in my PZIII I have 2 450 Watt motors,
they are those of the Panther (they are the Armortek, I don't remember the brand),
they are about 20A theoretical per motor, powered at 24 volts,
in overload they can easily reach double the absorption,
so 20 x 2 are 40 A with motor, 80 A Maximum in total,
now with the Flysky radio I don't have the current absorption in the telemetry,
only the battery voltage,
with the old DX8 spektrum the telemetry has never measured me more than 30A total.
the main circuit breaker,
between the batteries and all the rest,
only serves to protect the batteries from overloading,
after that I have a distributor with 1 fuse for each electronics, if the main switch trips (having only that),
go figure where did you get the problem.
In the Group we have often had to tow a tank that has run out of batteries,
wagons without telemetry or with BMS, there the absorptions go up a lot.
Very high but instantaneous absorptions are not a problem,
the problem is continuous very high absorptions.
Hi
Marco