Battery question

Jan_Donadoni · Post by **Jan_Donadoni** » Sun Feb 20, 2011 9:24 pm

Hello,
just wondering if has ever tried to use anything else than Pb batteries ?
Or, better, anyone has ever thought about using LiPo batteries?
using 6 cells we should reach 22,2V, using 7 cells 25,9V. Actually a fully charged battery even gives higher Voltage, so maybe a 6 cells would be enough.
They are expensive, but not far away from gel Pb batteries. Amperage reaches max 5 Ah, for R/C batteries, BUT they are very small, very light and really fast to recharge. You just need little more than 1 hour to charge a "flat" battery.
Not to forget, they maintain the full charge (or at least a 90-95%) for a really long time, so you can get a trip without planning it ahead.

Allan Webster · Post by **Allan Webster** » Mon Feb 21, 2011 7:50 am

The safety aspects would worry me. See:

Jan_Donadoni · Post by **Jan_Donadoni** » Mon Feb 21, 2011 10:02 am

Do not worry too much.
Actually I have a pretty good experience with LiPo batteries, I am a AirSoftGunner too, and I use LiPo batteries in very hard (poor) condition (hot, cold, wet weather). Also the handling is pretty harsh with items falling all the time.
Two things are important. Do NOT short circuit them or they will tend to overheat and eventually burn or explode. Second : you have to properly and carefully charge them (LiPo charger AND Balancer). With 50 pound you can find a proper charger, with 200 you get a fully computerized charger capable of charging two or more batteries at the same time keeping all data under control (charging current, time, temperature and so on).
If you are VERY worried about safety there are special LiPo battery bags that will prevent possible fires to spread. They are not used in planes or small cars since they would add unnecessary weight (50 grams or so), but this would not be an issue in a 100Kg tank.

Andrea Daviero · Post by **Andrea Daviero** » Mon Feb 21, 2011 3:31 pm

I think that our future in big scale models will be the LiFePo batteries.
They are similar to the lipo but at the same volume they can supply more Ah.
They are expensive, but in some models they can be the only chance to have long running times.
I'm waiting a couple of batteries for my sdkfz7, at the same place of 2X 12V7Ah batteries I will have 2x 12,8V 20Ah batteries.

Joe Lilley · Post by **Joe Lilley** » Mon Feb 21, 2011 8:52 pm

I have been thinking about Lipos for my Comet, I have been using them for some time in scale model boats with great success.
Provided you buy reasonable quality ones and use a balancing charger they are quite safe, I have done most things to them to try and make them burst into flames with no success. I know there were problems in the early days and these bad reports linger in the memory, I had someone only the other day still saying he won't convert to 2.4 because of the problems with them!
Great advantage:- quick charging.
Big disadvantage: - if the cell voltage drops below 3volts they are ruined, there are low voltage warning devices available and on the basis that you don't let a tank far out of your sight this should provide suficient protection.

phil fitzpatrick · Post by **phil fitzpatrick** » Mon Feb 21, 2011 9:04 pm

Hi Guys
I've got a lot of LiPo batteries up to 6S and my biggest charger
the Bantam E-Station BC8DP which would charge 2 single 6S at
5 amp.
But I would never consider using Lipo Batteries in my Armortek
Tanks.
LiPo batteries are the first choice for electric helicopters right
up to the big 700 size Align.
They all need high discharge rates and bursts of high current.
With our Tanks we need high amp hour rates the limitting
factor being size.
First with new Armortek Tanks you would have to consider the
Warrantee,when not using the recomended batteries.
The Price
The price of LiPo,last time I looked the new big size 6S 5200mha
was Â£145.00 including vat,4 would give you 20.8 amp hour.
Thats a pocket bursting Â£580.00
Safety
The danger can be reduced greatly,with good product knowledge
common sense and above all else respect.
Oh and no mistakes!!!!!!!!!
With LiPo batteries connected to give the required amp hours,
they couldnt be charged untill all disconnected,and a proper
balancing charger used.
At the recommended charge rate of 1C max you could only
charge 2 at a time if you had the large charger,other wise
you might have to do the 4 seperately.
Murphy's Law says "What can short out will short out".
There is no safe way to charge them in the Tank and that comes
nicely back to the mistakes.
If you have to dig deep into the dungeons of your Tanks hull to
dig out 4 LiPo's every time you need to recharge them,unless you
are very carefull and insulate each connection as it is removed,
bonfire night or the Northern Lights in the sky,will have nothing on
the pending effects if you have a short.
Looking at my 6S Lipo in my 600 size Heli I think you would only
save one battery's space.
Then there is the safety device for your LiPo batteries because
the green,orange and red light is no good for them hidden in the
Tank.
Drop bellow 3.0 volt per cell and you may never recover the
battery by recharging.
So you would need one of those warning devices in circuit to let
off an alarm when reducing to at least 3.5 volt.
I have had to coax a battery back to life that the computerised
charger refused to charge,comes up with the warning voltage
too low or missing cell.
No its not yet worth the hassel
I dont have any experience with LiFepo batteries but I am aware
of them.I think they are an amalgamation of the quallities of LiPo
and LiFe batteries.
But from an article I read I think they might charge a bit faster and
drop a bit lower safeley.
No,not for my Tanks.
Cheers
Phil

Adrian Harris · Post by **Adrian Harris** » Mon Feb 21, 2011 9:15 pm

The LiFePo batteries look to be the sort of thing for which we should be aiming, but at the moment they seem to be rather odd sizes which are at odds with tanks hulls.

The 24V 30Ah one I found is 270x270x75mm. The low height makes it handy for going under the turret and blank firer but at 270mm wide, it will only fit in models such as the Tiger. It won't even fit in a Sherman, unless fitted level with the sponsons.

Hopefully the scientists will be able to reduce the size in time.

Adrian.

Andrea Daviero · Post by **Andrea Daviero** » Mon Feb 21, 2011 9:37 pm

http://www.lipotech.net/storeindustria/ ... 0a4f86734b
Search on this site, they have a lot of type of life batteries. There are some with same Ah but different measures.
As you stated before, the most important thing is the battery capacity (Ah), wich tell us how long it can supply power to the tank.
Don't order if it is stated that has low quantity or if they are backordered, I'm waiting my life from December...

phil fitzpatrick · Post by **phil fitzpatrick** » Mon Feb 21, 2011 10:29 pm

Some interesting batteries on that link Andrew
The Ltf6 range 12.8v x 10ah looks interesting at 175mm x 123mm
x 27mm. and can drop to 2.5v per cell.
I see what you mean about the not available or limitted supply
problem.
Is it a dedicated charger for the LiFeP4 batteries?
Cheers
Phil

Jan_Donadoni · Post by **Jan_Donadoni** » Tue Feb 22, 2011 6:08 am

For the charger take a look as these :

http://www.graupner.de/en/products/843d ... oduct.aspx

http://www.graupner.de/en/products/843d ... oduct.aspx

I've got this latter one:
http://www.graupner.de/en/products/843d ... oduct.aspx

Found on Ebay for a reasonable price.

Jan_Donadoni · Post by **Jan_Donadoni** » Tue Feb 22, 2011 6:19 am

I am also considering using the LiPo or Life in my 222.
The should both save some space (222 is pretty "small" and has little space to spare) and also some weight, since the 222 is generally know for being "heavier than real one", thus helping to partially solve the drive train issues.

Regarding safety risks.
I am also anAir Soft Gunner. Started to use the lipos nearly a year ago. They received really a hard treatment. Cold, hot, wet and all kinds of poor weather, mud and dust and my rifles fell plenty of times. The batteries never gave a single problem.

Regarding short circuiting. LiPos and similar usually have "tamiya" connectors, which prevent easy short circuiting.
Also they are generally much smaller for the same amperage, so it should be pretty easy to extract them each time from the tank (as to connect properly the balancer). If i think to my rifles where sometimes the margin is less than 1mm to accomodate the battery I believe using the ports in the tank should not be a problem.

Jan_Donadoni · Post by **Jan_Donadoni** » Tue Feb 22, 2011 10:48 am

Hello,
would really like to have "official" Armortek advice on the issue.
Traditional batteries ar Ok for the big bad boys (tanks) but for the smallere ones? Like the 222 and the Sdkfz 7 ?
Did Armortek ever made any test with LiPo or LiFe batteries?

Andrea Daviero · Post by **Andrea Daviero** » Tue Feb 22, 2011 5:39 pm

Maybe that changing to lipo or life will require a battery cut off to protect the battery cells for the undervoltage.
Armortek in the sdkfz7 (and probably also other afvs) uses a relay controlled power. If voltage drops the relay will open the circuit.
So, maybe we have all ready for lipo/life, and I'm sure that noone will run an heavy tank till its battery is completely down. This will mean that it must be towed or taken by hand.

Andrea Daviero · Post by **Andrea Daviero** » Sun Apr 03, 2011 4:40 pm

I replaced few weeks ago the battery with 2 20Ah LifePo4 batteries (12,8V each)
I'm impressed about battery life, battery power until it is almost discharged.
It gives full voltage through most of its operation, and when you feel that it is slowing, the battery is almost discharged.
It charges till 22Ah, so, more than default, you can use almost all of the charge, but you need a battery low voltage cut off to prevent battery damage.
I've not found a device for 8S life batteries, so I'm not using it till it is discharged.
I also integrated the TBS mini (benedini) + amplifier with the main batteries, in the old configuration the audio system used a third battery.
Also with this new load, it worked very well!
The only few problems: 1 battery in the engine compartment, one on the aft baggage compartment.
This is not a problem now, it will be in future when I will do the flakvierling version.

Martin Cohen · Post by **Martin Cohen** » Mon Apr 04, 2011 4:00 am

I like the idea of a battery taking up less space in my tank, maybe even weighing less. However, I might better justify the expense of exotic batteries if I understood more about:

1. shelf life: I mean, if I let my Tiger sit on display for months then use it, then display it for months, etc. How does the overall life of these exotic batteries compare with that of lead acid batteries?

2. I understand lead acid batteries do best if they are periodically charged, even when not in use, every three months or so. How do LiPo's compare in terms of needing periodic charging?

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