LiPo Battery

[Terry Godwin]

Has anyone used LiPo batteries for this size tank. 7cell 5800MAH LiPo batteries are currrently available.

[Adrian Harris]

Hi Terry.

This was discussed on the UKTC forum a while ago. It descended into a bit of a bun fight but there might be some useful information there for you:

http://www.uktank.org/phpbb3/viewtopic.php?f=1&t=5347

Adrian.

[Günter Gäbelein]

Hi Terry,

I am using a lipo (22,2 V, 5AH) in my T34/76 and I also plan to replace the PB-batteries in my Panzer IV by the same lipo. In the T34 I can change it easy through the big hatch at the hull deck.

[Adrian Harris]

Günter

How long does you 5AH battery last, or are you running several in parallel ?

And how long does it take to recharge ?

As I understand it, one of the advantages of LiPos is the speed with which they can be regularly charged.

Adrian.

[Günter Gäbelein]

Hi Adrian,

I still have no experiences with the lipos in the T34/76, but I am using lipos in my AEV3 Kodiak in 1/10 scale since 2 years. Here I am using 3 lipos 11.1V with 5AH. I have 2 switches, to select the lipo in use (and also for recharging). The lipos can be switched during use. Before changing to the lipos I used one PB-battery with 12V and 12AH. The operation time was round about 75 minutes and recharging time was 14 hours. By using the lipos I have an operation time of 90 minutes and recharging time depends on the power. Normaly I am recharging with 3.5A (the lipos do not get warm and must not be taken out of the model) b a time of ~90-120 minutes. It would be no problem to recharge each lipo in less than one hour.
For the T34/76 I expect an operation time of 30-40 minutes (with one lipo) but I have no experience yet. Recharching time is similar to the others. In the Panzer IV I plan to place at least 2 Lipos (22.2V 5AH) also selected by a switch. So I get an operation time similar to the PB-batterie (24V 12AH), but with less weight and less recharging time. By using the space of the PB-Batteries with lipos I could at least triple the operation time.

[Terry Godwin]

Thanks for the input. I am tempted to use LiPo for my Tiger 1.

One problem I did not see discussed here or on the link provided. If you over discharge a LiPo it becomes useless. It can not be recharged.

I have used LiPo in RC aircraft. Todays Speed controls sense the battteries charge state and shut down before the battery reaches the level where it can not be recharged. Does tthe Heavy duty spoeed control preovided with the Tiger 1 have this feature?

Terry

[Günter Gäbelein]

Terry,

I would recommend to use a battery monitor! Yesterday I discharged the lipo in my T34 by testing the motion pack. When the LED at the Power Pack changed to red, the lipo has still 5% usable capacity, so if you use the lipo like the PB-batteries before, you should not get a problem.

One time I discharged a lipo totally, but I could awake it. Normally it is not possible by using lipo chargers, because they expect a minimum voltage. But in my case the voltage was less then 1 V in each cell, so I recharched the lipo like a PB-battery for a short time (~ 30 minutes). After that, the voltage in each cell was enough to be detected by the lipo charger.
This is only a personel experience, no recommendation! You will do something like that for your own risk! But it works!

[Adrian Harris]

> Does tthe Heavy duty spoeed control preovided with the Tiger 1 have this feature?

The current generation of Armortek modules doesn't have that feature, but it may be something to include in a later version, especially if LiPo power becomes popular.

I don't know what the effect would be if a battery monitor cut the power to a 1/6th tank whilst it was in motion, as the currents flowing can be quite high.

There's no technical reason why a system couldn't be developed which not only monitored the individual cell voltages but also sat between the RC receiver and the power module and stopped the tank gently before disconnecting the batteries.

An alarm sounding when there is 15 minutes of charge left sounds like a good idea too. That way you have a chance of getting the tank back into the car/van/trailer before the charge is exhausted.

Adrian.

[Terry Godwin]

You can get 75 and 100 Amp speed controllers for RC aircraft. These include the sensing the curent chare and shutting the controller down before the LiPo reaches criticalIn most current products you canm set the level opf charge you want to use for cut off.

How much current do trhe high efficiency motors draw?

Terry

[Steven Raison]

Hey guys

So im getting to the stage in my build where i need to get batteries and think im going to go lipo.

I seen above that the voltage required was 22.2v so combine multiple 11.1v batteries but how many mAH should you get? Also is it better to get a high 30C battery ?

Working on a 2012 tiger 1

Thanks for any info you can give me

[Günter Gäbelein]

Hi Steven,

I would not combine 11.1V packs. It is better to use 22.2V packs. I made good experience with that in my T34/76. One 5000Ah pack is good for 30 Minutes full operation. So, i.e. if you use 4 packs you can get up to 2 hours operation with your Tiger. In that case, I would select the packs by a switch. I made this in my AEV3 Kodiak. I have 2 switches, to select one of the lipos, for operation and also for recharging (the lipos can not be removed for recharging). In the T34, I have one lipo placed unter the big rear hatch, I can change it in half a minute.

[Steven Raison]

What about the C rating of the battery, is it best to go with a high or low C rating?

[Adrian Harris]

I must admit I don't know much about LiPo batteries but if you're taking more than 10A from the battery then you're running the tank pretty hard, unless it's a KT with two smoke units, so I wouldn't have thought a 30C battery would be of any advantage.

Adrian.

[Jan_Donadoni]

more than LiPo batteries I would suggest LiFe (or LiFePo) batteries.
Very sturdy and stable, do not have the safety issues of LiPo batteries (except the usual overdischarge issue) and pretty small and light

I am planning (already bought) to install 10aH in my 222 and 22aH in my tanks

High C factor is good but not necessary. The C factor indicates "how fast (violently)" a battery can discharge without damage.
That is C is the total capacity (in Ampheres) 10C means that it can be discharged at 10 times it's capacity (that is running the battery flat in 6 minutes). I.E. 12,8V 22aH 10C/20C means : 12,8 battery, total capacity 22aH, could be discharged continuosly at 220aH (continuos) or 440aH (for max 60 seconds)
Actually our tanks never need a very strong current. Obviously small batteries (10aH or less) would need a higher C factor to avoid problems.
Only important factor : always install a "low voltage cut-off or LiPo/LiFe saver". this small circuit stops the electronics as soon as the current voltage runs below a certain limit. that is LiPo and LiFe batteries could be PERMANENTLY damaged by discharging them too much, to a too low voltage level. Actual Armortek electronics can still work with a voltage that is too low for LiPo/LiFe batteries, so you need this small circuit to avoid damaging such high performance (and pretty expensive) batteries
LiPo saver coud be easily found at any RC model shop

[Andrea Daviero]

I completely quote Jan about LifePo batteries, I use a couple of 12,8V, 4S Life(po) 20 Amps batteries in series for my halftrack and the difference ffrom the pb batteries (7Ah theorically, less than 3Ah really usable)
The problem right now is the price. Iacopo Di Giampietro will buy a 25,6V (8s) 30Ah battery for his panzer 3.
I was unsure about 1.6V more than the rated one for armortek electronics, but found it very stable.
However armortek protection circuit for low voltage cannot be used.
Unfortunately protections for 8S batteries are also not too much, mostly are voltage monitors, but, you will see when it discharges.
Life batteries have a stable voltage until they are near to be discharged,then you will see the model slowing down. it is the time to charge it.
I use this battery monitor for my halftrack:
http://www.hobbyking.com/hobbyking/stor ... _Lipo.html
It has also an aural alert when a single cell or the battery voltage is low, it halso has a transistor output to be used to connect for example a light or with another transistor, a relay wich can stop the model.
I'm planning to connect it with this protection.
Lipo batteries avaiable for models are very expensive compared to the lifepo (for electric bikes for example).
they weight less than Pb and Lipo, they use less space, their life is more than the others and they don't have the explosion problem present with the lipo batteries (that must be charged out of the model)