Batteries for the Chief

Forum for discussion relating to the Chietain MBT
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Richard Goodwin
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Batteries for the Chief

Post by Richard Goodwin »

With the delivery of my Option packs arriving this week, I've started to look at batteries. I did awhile ago look at a few threads on batteries and it would appear that despite the cost, LifePo4 batteries came out on top due to size, weight, safety when charging and number of recharges. That said, I could find nothing in regard to suitability wrt Short term Peak discharge current, Continuous discharge current and the recharge current from the Armortek modules.

Looking at the Peak discharge current (short term) capability of the Yuasa 12V 22Ah gel battery and a high grade, high performance, LifePo4 12V 20Ah battery, they can deliver a maximum of 300A and 90A respectively; quite a difference isn't it and probably due to the internal resistance of the batteries themselves; 8mOhms and 60mOhms respectively. A standard LifePo4 from the same manufacturer is around 40A!

Looking at continuous discharge current of the same two batteries is a little more troublesome since there are no figures qouted for the Yuasa but the high performance LifePo4 is 50A and its 20A for a standard LifePo4 although the Yausa may also be able to supply 50A continuously.

Lastly, I could be wrong here but I thought I had heard somewhere that the Armortek modules supply a recharge current to the batteries whilst in operation. Am I correct or am I imagining this?

SO.........in order to help me decide which type of battery and what size to get, I would be grateful as I'm sure others would be, of some input to these the following key questions:

1. What is a typical peak short term discharge current for these heavy tank models?

2. What is the average continuous current draw with all options fitted driving in the same direction without turning?

3. If there is a recharge current supplied by the modules, whats its value approximately?

One last thing, if you are considering LifePo4 batteries, do pay attention to the specs! There are some large differences out there in regard to output currents, peak currents and the number of recharge cycles.

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Adrian Harris
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Re: Batteries for the Chief

Post by Adrian Harris »

> 1. What is a typical peak short term discharge current for these heavy tank models?

There's a 60A fuse in the old larger Motion Control Module...

The peak output of the new Red modules, unless they've been reconfigured, is 64A per channel, so 128A in total.

Interestingly, at 70°C, max continuous current output is only 10A per channel. Something to think about for shows in June, or hot climates.

I seem to get a total current of around 60A on the telemetry with the electronics I have fitted into the Cent Bridgelayer, which uses the same drive system as the new red modules. I don't have a circuit breaker in the loop, so am not limited by that.

Back in 2007 :shock: , I did a stall test with a Sherman and that peaked out at 70A:

viewtopic.php?f=7&t=85&p=561&hilit=decking#p561

2. What is the average continuous current draw with all options fitted driving in the same direction without turning?

It depends. I don't run a smoker, which would add another couple of amps, but generally it's about 20A when driving the BL around with the sound on. I'm going to resurrect the T-34 shortly, which is a much lighter tank and runs from a LiFePO4 battery, so it will be interesting to see what figures I get from the telemetry when running that.

3. If there is a recharge current supplied by the modules, whats its value approximately?

It depends. Running down a steep bank will generate more current than down a shallow one. On the flat, unless you drive it like you stole it, I doubt there is much current getting back into the batteries. When you charge a lead acid battery, you use the same terminals as the load. With a BMS protected LiFePO4 battery, there is usually a separate charging connection, so I'm not even sure if the regen current would find its way back into the battery.

Adrian.
Contact me at sales@armortekaddict.uk for details of my smoker fan control module

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John Clarke
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Re: Batteries for the Chief

Post by John Clarke »

I'll be keeping it simples Richard. Yuasa 12V 22Ah x2 laying down

In the model boating world, batteries have duel role, Power source and ballast.

This would also be appropriate with Chieftain.

Well you wouldn't want it to float away would you! :lol:
Oh Man, I only ride em I don't know what makes them work,
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Stephen White
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Re: Batteries for the Chief

Post by Stephen White »

Good question Richard and helpful that you pointed out the variations in spec of lithium iron phosphate batteries.

The Tracer 24v 20AH battery I use offers a max peak current limit of 60A and a max continuous of 30A, which are both consistent with the spec of the Armortek modules. I’ve had no issues in normal use but Adrian has highlighted one factor to consider, which is performance in high temps under load. I’ve had one instance of the BMS cut off operating on a hot day when I tried a sharp turn on thick grass. It performed as advertised and was reset by applying a momentary charge. I agree with Adrian that you can discount the regenerative power issue although I do remember Mark Watkins raising it before anyone tried LiFePO4.

Chieftain is surprisingly challenged for hull space and the comparatively small footprint of Lithium Iron Phosphate is very helpful. I don’t buy the argument that more weight is a good thing, the models are heavy enough to be realistic. Although I accept that deciding between battery technologies is complicated, nothing could be simpler to install and operate than an LiFePO4 with BMS protection. And you don’t have to keep them on a maintenance charge as you do with Pb.

Finally, and it bears repetition, the major advantages of LiFePO4 are the flat discharge curve (= more power for longer), the reduced weight and size and the equivalence of whole life cost compared with Pb (= they cost more but last longer).

Prices are also beginning to show the effects of competition. From UK, Tracer were really the only module in town unless you wanted a custom array and they are up-market. Now you’re beginning to see other manufacturers coming in at substantially lower prices. It would be interesting to hear some user feedback.

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Re: Batteries for the Chief

Post by Dennis Jones »

Probably off the subject but can anybody tell me if LIPO or LIFO batteries are re-cyclable because as I see it if they are not then with all the changes to electric vehicles etc what's going to happen to all the old batteries. As opposed to lead acid batteries which are re-cycable, just a thought.

Dennis.

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Adrian Harris
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Re: Batteries for the Chief

Post by Adrian Harris »

https://batteryuniversity.com/learn/art ... _batteries

My local recycling centre has a container for batteries, and their website doesn't specify which types they do or do not take.

One advantage of the pack I use in the T-34 is that it is made up of individual Headway 40152S cells, rather than flat sheets as per the sealed types. If one cell starts to get tired, I can break down the pack and replace it just by undoing the screws in the ends.

Or I could replace all of them, and reuse the BMS, wiring and case.

If someone comes up with a cell in the same cell format but with higher capacity, that's another upgrade option.

Adrian.
Contact me at sales@armortekaddict.uk for details of my smoker fan control module

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Gerhard Michel
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Re: Batteries for the Chief

Post by Gerhard Michel »

Hi guys,

Lithium cells are recyclable, and Lithium is an expensive material.

My CALB cells (CALB = China Aircraft Lithium Battery) have a peak discharge current of 10 C and a peak charging current of 2 C. This means 400 amps peak discharge current and up to 80 amps charging current at a 40 amp hours battery, if the charger ist strong enough. Normal tank motors have a peak power consumption less 100 amps, only the Unite Motors (e.g. used in Bigtanks models) have up to 114 amps each. So the lithium cells have enough power to supply 2 motors also in extreme situations.

However, there are 2 obstacles supplying the engines with extreme high current:

1 - wiring is not thick enough (6 - 10 mm², AWG 9 - AWG 7 recommended)

2 - the beloved BMS limits the peak current! This is the main contention for me NOT to use a BMS.

My King Tiger consumpts ridiculous 4 amps to move forward at a plain ground, but it consumpts up to 60 amps when tableturning in high grass.
kind regards
Gerhard
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1/6 Scale models: Jagdpanther (AT), Jagdtiger (BT), Königstiger (Porsche turret, NH), Königstiger (Production turret, BT), Pz. IV (SH)

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Richard Goodwin
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Re: Batteries for the Chief

Post by Richard Goodwin »

Gents,

VMT for your inputs; they are greatly appreciated!
Last edited by Richard Goodwin on Thu Feb 06, 2020 11:56 pm, edited 1 time in total.

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Richard Goodwin
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Re: Batteries for the Chief

Post by Richard Goodwin »

Forgot to mention........it could be worth installing a fan on Motor Control A when operating in hot environments to increase its range at high temperatures!

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