First featherweight!

[Max]

I think Calum particularly recommends flightpower lipos

The other lead is for balance charging- you need a charger than can charge lipos. For cheap lipos I recommend the gens ace range on giant shark, it hasn't failed me yet

[PJ-27]

There's a thread on here somewhere, where I asked a series of questions about Li-Po.

The cells need to remain in 'balance' and this is achieved by using a charger that monitors the voltage of each cell individually. This is done via the extra cable, one lead for each cell and a ground.

[archie2000]

i have botbitz escheap85s.
looking forward to see the way it drives

[maddox10]

In terms of power I was thinking of 19.2V because it's still within the limits of the Gimson and I'd get a fair amount of extra torque and RPM. As for LiPo, I don't particularly mind paying the extra, but just quickly looking on eBay there are so many different makes, any particular recommendations?

5S is 18.5V nominal in LiPo, but 21V fully charged.

On recommendations. We have fairly good results with the Turnegy Nanotech in Hannibalito 4. But that's a 3S 3300mAh (11.1V) pack powering the Gimson GR01 9.9V combined with a Scorpion XL.

Also the botbitz suggestion seems fine, I'm guessing I'd need one per motor or can they control two?

Botbitz controlers are single motor controlers, so you'll need 2 .

Is there anything else I'd need to go with them (a BEC?, from what I've gathered it's just to not require an external battery pack powering the receiver although I have a few external packs already.)

A BEC is a battery eliminator circuit.
The main advantage is that you have flat reciever batteries when starting up the machine and realising D'OH , I forgot to turn off the reciever pack.
Moost modern speedo's have a BEC. But I fear it's one of the weak points of the Robot Power products. Those BEC's were designed when 40MHz was the norm, and an old school 40MHz reciever doesn't need as much power as a Dual 2.4GHz Spectrum BR6000. I don't know how the more modern recievers are concerning power, but the older DSM1 type recievers are hungry.

[Mouldy]

The BEC on the tz85a is 5amp.... wont struggle to power most rx's. Ive used botbitz on dsm1 and dsm2 and it worked fine on both.

[Mokichi]

Gimsons arrived a few days ago, and botbitz ESC's have been ordered.

In terms of battery I was looking at either Opti power LiPo or a cheaper (local) alternative

Otherwise two 9.6v NiMh packs from similar to this

I would prefer to voltage to be above the 14.4v of the Gimsons so I get a bit of extra speed/power. Also for either option could someone please recommend a good charger/balancer, thanks!

For a base plate I may use thinner HDPE (6mm) as there's less play room that I thought between the Gimson's plastic mounts and the 78mm wheels! I may purchase a couple of 100mm robochallenge wheels for this reason.

[maddox10]

Hannibalito 4 uses 170mm wheels on a set of 9.6V Gimsons. Speed is fine as you can see , even if we only use a 3S LiPo pack.

[Mokichi]

I can imagine the speed would be fine if my calculations are correct! xD

17cm x pi = 51cm ish
51cm x 530 (RPM) = 27030cm/min
27030cm/min --> mph = just over 10mph

Because of the smaller wheels I'm using, either 78mm or perhaps the 100mm robochallenge ones, I'd need to use more voltage to get a more adequate speed. Again my calculations would suggest that without increasing the voltage.

78mm wheels = 5.2mph
100mm = 6.8mph

Probably the maths is wrong though xD

[maddox10]

RPM is a tad higher. 9.6V=530 rpm= 55.3 rpm/v so 11.1V gives us 613 rpm= 19.6km/h (12mph), and that nominal.

Full LiPo's are 4.2V, so add another mph when starting.

[RogueTwoRobots]

Also for either option could someone please recommend a good charger/balancer, thanks!

I've got two of these chargers:

http://www.giantshark.co.uk/power-a606- ... 05325.html

Can't really go wrong with them. They do everything from SLA through to various lithium types, come with a bunch of different charging leads, can be powered off the mains (a lot of chargers only have DC inputs, so require either big batteries or a separate AC power supply unit) and, best of all, they cost less than £30.

The downside for lipos etc is that you can only charge up to 6S packs as it doesn't have balance charge inputs for any larger packs. Depends on whether you envisage using larger packs in the future.