Armortek

Richard Goodwin wrote: ↑

Sat Oct 17, 2020 11:34 pm

Does anyone have any measurement data wrt current draw of the motors on any model?

Hi Richard,

all my models have -among other shown values on my transmitter- a real time current measurement via telemetry (the other transmitted data are e.g. voltages of each LiFe cell, temps of motors and ESC and -important- the consumed capacity of the driving battery). It's rather astonishing which peak values of driving current you can see and under which conditions they occur.

My non-Armortek models are equipped with spur gear motors of either 350 watts or 450 watts, similar to the spiradrives. The power consumption is also similar to Armortek tanks. My Armortek Jagdpanther actually has dead lead acid batteries and is not operational, therefore I will use data of my other models.

Perhaps discussing my so called Pöti (king tiger with Porsche turret) with about 160 kgs and grippy steel track links showing the following data:

- driving ahead at flat and plane ground: 4 amps (for the whole tank!)

- driving ahead at an ascent of perhaps 10 %: 10 amps

- driving a turn: 15 to 35 amps, depending on kind of surface

- table turn in rough grounds: up to 55 amps, which means an overload of 50 % to the motors.

You see that climbing moderate hills is not as power consuming as turning in the plane. The reason is that when driving ahead the tank treads lie immovable on the ground and the roadwheels roll over them, but when cornering each track link is moved across the ground, while the whole weight of the tank bears upon the track. Therefore much more power is needed to move a tank (original and model) through a turn than driving straight ahead. But I was astonished that the difference makes up to 15 times more!

Gerhard, that's useful data. Your observation about the power required to turn on resistant ground matches up with my case of the BMS cutting in when I was attempting to turn the Centurion on grass at slow speed on a very hot day. It's probably the worst case for power consumption. More data would be really helpful, particularly from the heavier models and with the latest Armortek motion system. I suspect we'll find that a LiFePO4 with a max momentary limit of 60A is fine.

I don't think the max limit will be an issue either however, the time it can be applied is! Looking at the specs for different suppliers indicates diffent times in which this max current can be supplied for. Some are milli seconds whilst others are seconds. Its worth checking!!

It would be interesting to know the current coming down that ascent.

If it never goes negative then there's no appreciable regeneration occuring.

Adrian.

Armortek noob and electronics idiot-savant without the savant part here...

Would you say something like this: https://www.batteryspace.com/custom-lif ... a-pcm.aspx

Meet the requirements you have discussed? What specifically should I ask or look for in a LifePo4 pack?

Thank you for any guidance you can provide.

For the Chieftain size could be a factor as there is surprisingly little room in the hull (in terms of height) once the motors and speakers are mounted. The batteries have to be laid flat and one have to be wedge right up the front ,you cannot mount them upright unlike a KT . I'm still scratching my head on how Phil Wollard can fit interior details and still managed to shoehorned the batteries into the Chieftain.

Don,

The battery you looked at does have a 60A max charge rate but you might want to check under what conditions (momentary and for how long). The protection specs looks like an effective BMS, which is vital. I'm a bit surprised by the figures for life cycle. At 1000, this seems low. My Tracer pack has a 1500 cycle life. Note also our discussion about capacity. You can never have too much capacity but if cost and/or space is an issue, you could probably get away with a lower capacity than 20ah. See the earlier discussion. Something around 12-14 might suffice.

Manny, yes and one of the reasons I like LiFePO4 technology. I've pushed the battery in my Cent right forward into the driver's compartment and there is still room for a driver figure to sit on top. That also helps with centre of gravity.

Manny, Phil uses Doctor Who Tardis technology, Its a lot bigger on the inside than the outside.

Stephen White wrote: ↑

Mon Oct 19, 2020 12:17 pm

Don,

The battery you looked at does have a 60A max charge rate but you might want to check under what conditions (momentary and for how long). The protection specs looks like an effective BMS, which is vital. I'm a bit surprised by the figures for life cycle. At 1000, this seems low. My Tracer pack has a 1500 cycle life. Note also our discussion about capacity. You can never have too much capacity but if cost and/or space is an issue, you could probably get away with a lower capacity than 20ah. See the earlier discussion. Something around 12-14 might suffice.

Manny, yes and one of the reasons I like LiFePO4 technology. I've pushed the battery in my Cent right forward into the driver's compartment and there is still room for a driver figure to sit on top. That also helps with centre of gravity.

Stephen,

Thank you very much! After more looking I think I've settled on this one: https://relionbattery.com/products/lithium/rb24v20 which has readily available specs and seems a bit more "buttoned up".

Thanks again for all your help!

Don, pleased to be of help. That battery has some very interesting figures. I'm especially interested to see that the peak discharge current of 60A (as you'd expect) but it will tolerate that level for 7.5 secs. That's much more than the milliseconds seen on others. What's more, the BMS only cuts off the power at 170A for 10 milliseconds. That's an enormous margin of safety and ought to reassure anyone dubious about the effectiveness of BMS in protecting LiFePO4 batteries in our likely usage case. Thanks for letting us know.

Gerhard,

- table turn in rough grounds: up to 55 amps, which means an overload of 50 % to the motors.

Found this explanation as to why this may be the case. It also would explain the increased current when just turning:

It should be noticed that a true tracked vehicle can take a lot of power (motor current) to turn ‘on the spot’ as the diagram should make clear. The green arrows show the machine turning about its centre. At the ends of the tracks the arrows are nearly at right angles to the track: movement along the track’s running direction is minimal and the ends of the track are having to slide sideways, so if the track has a good grip, a lot of turning force will be needed. Only near the centre of the track is the track not sliding sideways.

Clearly the longer the track is, the worse the effect and the wider the tracks are apart, the better the turning ability. If the tracks are wide enough apart (in relation to their length) then the nearer they behave to two normal wheels.

Doesn't bode well for Chieftain with its rubber pads on tarmac does it! If your King Tiger is anything to go by, Chieftain has the potential to be up there as well and if it is, push a LiFePO4 battery to its limit.

Best batteries to use for Chieftain

I don't think there is a definitive answer any more

But if I were to use the Armortek Red boxes in standard format as Armortek recommend, two 12 volt 22ah AGM batteries are advised.

That is the way the red boxes have been setup and it's difficult to argue against that. I've spent £1600 on the motion pack (Chieftain) and I'm not about to start changing the electrical spec's for no good reason.

I expect to get up to an hour running time (Chieftain) and often as much it will depend on terrain and the way it is driven.
That could easily be broken down into several short runs during a show day, so no real problems there. (Donuts not advised Richard )

I think there is a question mark hanging over Lifepo 4 Batteries. Ideal no doubt for solar storage systems, golf trolleys, wheel chairs and electric scooters.

But nowhere does it officially say their ideal for Armortek tanks with Red box controlled motion packs.

Maybe the Red boxes will get a upgrade in the future, (regeneration dropped) but till then (hate to say it) I'll abide by the recommendations

Hi, and a happy new year to you all.

As someone who is new, as are others, to this addictive (obsessive, honestly I think it is, as the good lady tells me) hobby. I agree with John's comments, unless one has a degree in electronics or been in the radio controlled world consistently for decades, stick with the suggested options, for now. No. 34 is back on the bench for the winter and has a weekly maintenance charge for the lead acids, along with all the others

There is a lot of info on the forum some of which is easily digestible, to me at least. However when it comes to batteries, charging rates, U-tube nasties and all those lovely aftermarket electronics, I am lost.

I would love to meet up, at some point, with the those who have the knowledge and are prepared to share it.

Keep safe and party on (its ok for some it seems)

Cheers Charles

Hi Richard,

I think your explanation is a good one. IMHO my non-Armortek King Tiger with Olaf's steel track links demonstrated impressively, where a lot of electric power is lost when table turning. The 'nest' in the following picture occured by simple table turning:




The stone in the middle is only for marking a tiny amount of remaining ground which prevented the tank from mining to the south pole.....

That's a really nice clean KT. Does that pillar swivel