RC Tank Warfare community hobby forum

Completely agree on the answers here that i should be getting a lot more time out of it, I am very capable of being daft and making mistakes so problem is in the chair more likely than the tank!

@Rad i had a read of your battery explanation blog and was very useful.

Invested in a battery meter today, whilst that is arriving I have charged the Li-ion this morning. At 1C, which in the Samsung specs says 1300mah, it literally topped the battery up with 900 charge. Am now discharging the battery at 1 amp to see what comes out of it. What would be a reasonable draw on the battery for an RC tank, appreciate all are different.

Great advice on the NimH too Mr General, I am going to cycle that on the charger to see what goes in it and what comes out of it too.

Will post up the results when i have them.

Thanks

Dave

There's little point me guessing the draw on your tank as no two are the same but it will be relatively low compared to, say, a low turn touring car which your NiMH could deal with no problem. The C rating if your pack is a good guide both for burst ratings and for charge rates.

Our tanks use small motor cans with high turn armatures, low draw LEDs and sound cards and low torque servos, all low as draw items. Max draw would occur only if you drive into a wall and keep the throttle open! We'll await you test results.

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Thanks general, I discharged the li-ion battery and it showed nearly 4200 capacity drained. So when I fully charged the battery this morning it added circa 850. Which tells me it had over 3200 capacity left last night. So about 65% still charged. I did some test drives last night on stone floors with a bit of carpet, for the kit in the tank I don't think it should be a challenge.

After reading a bit online the discharge rate doesn't seem to be linear and relatively shallow till it reaches a drop off quite sharply near the last 15% or so.

Agree I should be getting well over 2 hours at least. Agree that the nimh should be giving me over 30 mins too.

Batteries and electronics are a bit of a wooly area for me so I could be very wrong however all I am seeing is pointing to a wtf moment.

Any thoughts?

Thanks

Dave

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New batteries don't always perform as well as ones that have been through a couple of cycles so why not cycle both of them a couple of times, noting the mah figures for each cycle peak. If either fall short of their claimed capacities then a call to SMC would be in order. However, if the figures are good then maybe you need to start looking for high draw items on your tank that may be faulty. Good luck


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thanks for the advice on that, ill give them both a couple of cycles, see how they get on. Realistically the high draw items are going to be the gearboxes and the smoker I guess, hope it doesnt get that far! thanks again

Hello,
on our tanks, the smoke system, is part of the most important energy consumer , do the test without it, to see

Hi,
Just for info.
You can buy an r/c watt meter, ( ie GT Power, there are other makes ) great for diagnostics and setting things up rather than guessing, it plugs into your battery then into your model battery input, it will tell you exactly how many amps / watts your model is pulling in real time as you use it, and will show you as you switch things on ie the smoker, they are quite cheap to buy but worth every penny.
It will tell you if its the model pulling too much or the battery is not performing.
I use one to match air props to speedos and batteries to get the max performance to current draw.
Sub

Hi all, been a long time on this. Have moved house finally and have moved all my belongings out of storage. Including my tanks!

Have bought a watt meter and taken some readings. I have zero idea why I can't get this to work.

I've unplugged everything but the gearboxes. Changed the ibu2u file to give 20 amps max to the gearboxes. Using a 5200mah li-ion battery thats got 41.4 wh.

Peak amps recorded 16.33, 101 Watts draw max, 0.100mah used for the session, 0.7wh total usage.

I am still getting the board cutting out and telling me low battery. It's not, it just isn't. Charged up yesterday as per instructions. 1.3a rate, capacity shown as circa 4800. Even the watt meter is showing that the voltage on the battery is 7.9v and the minimum voltage is 7.77. So its not flat. I got about 5 mins on grass, the gearboxes should easily cope. It happens on wood flooring too.

I've bought a lipo battery now to test it with, haven't yet however I'm sure it won't make a difference based on the above.

I'm going to caveat all the above with I'm an IT consultant, not an electrical engineer. My rudimentary knowledge of electronics says that this is nuts and something is broken.

Has anyone got any ideas here, I am not precious and would be very ok to be wrong!! Just want to be able to use the flipping thing!

Cheers

Dave

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Hi.


Ok so i have just had a thought.......

You say its an ibu2 board...i am not familiar BUT does it have a LIPO battery setting or battery type setting where you can set a LOW VOLTAGE FAILSAFE to ensure the lipo does not discharge too low ?
I know that quite a lot of modern rc electronics do have them fitted as standard to protect the electronics and batteries.
If so it could be kicking in as a Lion battery has no where near the discharge capability of a Lipo.
16.33 Amps is a hefty discharge rate.

It wont be the first time that something similar has caused the exact same issue you are having.

Edit...

Just found this in the ibu2 site

Battery voltage selection, now is possible to use 3 cells Li-Po or 8 cells Ni-Mh packs with “low voltage” warning and “battery discharged” cut-off.                      


Hope its of use and makes sense.
Sub.

Hello, I think Sub ,has a good idea, indeed, you have to choose the type of battery, like many cards today!! maybe a way to follow?