lipo batterys

i was thinking of up grading to a lipo, and was wondering whether people thought its better to get to smaller battery's and swap every fight (charging the one that's not in the robot), or one big batter than can last multiple fights? so charge it less often, when we have time.

Because with a NiMh or lead acid is a no brainer, get a larger batter ( that you can fit in the weight limit) and then top up between fights but never remove it.

But with lipos you have to remove them to charge them, and that takes longer,so i cant decide whether to get two like 5000mah lipos which might just last two fights (i would fit telemetry system to tell me how its going) or 1 8000mah battery which should last for like 4? the 5000mah seems the better idea as its lighter and we can swap them between each competition fight, but i would have thought a 8000mah battery would be better for white boards as it can be run continually for a few battles?
i cant decide what to do? both a similar price
any thoughs?

(i was looking at the turnigy nano tech batterys by the way, http://www.hobbyking.com/hobbyking/stor ... Order=desc
so was also wondering how they faired?)

What does it need to power?

Your best of getting one good quality pack... Optipower or thunderpower are the current market leaders....

Since you have to take it out each fight u mayaswell charge it.. Lipos don't take long to charge.

8000mah is overkill for any feather.

Oh right ok,
It's a 4x4 drill box (with a new weapon to be fitted but that's not hugely powerful)

I just that I used a 7500mah battery (it was a lead acid so that could be something to do with it) but that only lasted like three battles, and I figured a better battery with a higher discharge rate would out put more power so would last considerably less time, especially if you can't run it till its flat.

I'll look into the better battery's though, the only problem is my charge would take more than an hour to charge them so they may not be fully charged between battles? How do they cope with only being 3/4 charged? Would that be ok?

im using a 4 drill motor for in a ram bot i have and my reckoning is that a drill motor can pull 25-30a so that a max of 120a so i bought a Turnigy nano tech 4.0, 4s lipo with a bust current of 50c.

so 4x50= 200a so im covered if it stalls and the continuous current is 25c so ive got 100a for general running

and on my first wheels of the ground test i tried my origionl nimh battery and the lipo and you could see and hear the difference


oh also i only worked out the amps for the motor because the sabertooth i used originality caused the motors to judder when it was pushing things

You should be fine with a 2500-3000mah lipo, get the highest C Rating lipo you can afford as they are better at supplying the current, each fight take them out and check them over and always balance charge them

Also make sure you have a fuse in the circuit that is well below the max discharge that the battery can give for safety.

As kenny says you will not need a lipo bigger than 2 to 3 Ah. Running boner in fights even when it's going the full 3 minutes doesn't take more than 1.5Ah out of the battery. I use a 4Ah lipo but that's to get the discharge for the brushless motor.

Another point is that you don't want to be in the situation of discharging the Lipo to far.

Most of the machines could run on batteries maybe 2/3rds the size or less but if you do then you are in danger of draining the battery to a dangerous/damaging level.

I have down graded slightly in Conker as I ran a 4S 4Ah battery for 1 GR01s. I charged once last year at GSL and that was only 800mAh after 2 fights. So now its a 3.3Ah.

We have our eyes on 5Ah ones as it allows for a relatively high discharge, and long playtime. Tormenta 2 currently runs very nicely on about 65a overall discharge available from its NiMH packs. We will be upgrading to a LiPo that can supply at least 100a. Not massively powerful, but the likelihood of all 5 motors stalling is tiny, and we'll run a fuse just in case.

Ok that's helpful, and as the higher end stuff are far to expensive for me, I'm probably going to go with the 4000mah turnigy battery's which are said to be 90c, but then says later in the discription that the continuous is only 45c with a peak of 90c, but it still should be fine.

And as cheap Chinese Internet company's go, turnigy seems to be pretty good, and have an ok name for them selves, so I'm hoping the lipos should be fine.

I will probably fit a fuse which is similar to the continues current, around 180 amps as I don't think it should blow from peak current but will after prolonged use

Is the aluminium base plate still recommended? Or can I just use the material from a lipo sack to line the lipo box in the robot to reduce the danger from a lipo fire, As the plastic would melt intstantly so you'd end up with a hot molten mess which I suspect most EO's don't want burnt to the bottom of there arenas :crazy:

Sorry perhaps I wasn't clear.

THE FUSE IS MANDATORY FOR SAFETY!!!!!!!!!!!!!!!

It's all in the rules gents.

7.8 LiPo
Lithium Polymer batteries have specific limitations and extra precautions which must be adhered to.
7.8.1 Balancers
Appropriate balancers must be provided if not part of the charger. They will be inspected during the
Technical Check. LiPo batteries should be properly balanced to prevent damage occurring to the cells.
7.8.2 Voltage Cut-out (Advisory)
The robot should be fitted with an under voltage cut-out or alarm set at or higher than the battery
manufacturer€Ÿs recommendation to prevent the batteries from becoming damaged by over discharge.
7.8.3 Fusing
A fuse rated below the maximum burst discharge of the battery must be fitted.
7.8.4 Extra Equipment
Roboteers using LiPo batteries must provide a LiPo sack.
7.8.5 Inspection
LiPo batteries must be removed from the robot, inspected and placed into a LiPo sack prior to and during
the charging process.
7.8.6 Charging
Lithium batteries must not be left unattended at any time during the charging process. Leaving batteries
unattended while charging will be considered a serious breach of pit safety and may result in you and
your robot being removed from the event.
7.8.7 Damage
LiPo batteries showing any evidence of damage or swelling must immediately be placed a LiPo sack and
removed to a safe, well-ventilated area such as outdoors.

And when it comes to protecting them, I would always encourage a 2mm metal base underneath the lipo. If not for the safety element then to merely protect your investment.

Sorry if I wasn't clear, I ment the probably for the current rating, as I wouldn't trust the turnigys 90c burst current, so would fit it lower current like the equivalent of 70c or something as I dont feel a 360 amp fuse would stop the pack going up.

And with the aluminium, would the lipo being placed in a small aluminium box do, as I can't really chane the whole base plate, and a box should protect it from all directions? Thanks though, I would want to get this wrong

As long as that base plate is 2mm thick or more, you don't need a separate box. I would recommend some padding around whatever you are securing it down with.

Base plate isn't a rule!

No its not, but Kane said it would be put in the rules. Best to be ready when it does get dropped in.

If you have a 1mm base plate with any battery you are asking for trouble never mind a lipo!

aha yeah! and presume it has to be 2mm metal and not plastic as 2mm plastic would be pretty usless against any thing :lol: and ok cool thanks