LIPO Batteries in Mardaves

[Richie]

Hi All

On a few of the posts I have seen people refer to Lipo batteries in Mardaves and being completely out of touch on this subject I was wondering if someone could advise and maybe setup some debate as to what the feelings are without necessary implementing anything, and certainly not wishing to implement any changes to the next championship.

For Example

I thought I heard a rumour that Mr Mardave was considering developing a Lipo cell, does anyone have any idea what size, what voltage and when this may be available ?
I believe you only need one lipo cell and they can be recharged straight after a race which would make them cheaper than buying 3 packs of the current type cells, does everyone agree ?
If lipos were considered should the car 1Kg weight limit be reduced to compensate ?
Some people are against LIPO cells in Mardaves, could I ask why ?
Are their any disadvantages to running LIPO cells in Mardaves ?
Does anyone know the maximum voltage a mabucci motor will take ?
Richard

[Gazza]

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[Rich]

Couldnt stay away ey gazza

I don't think it's time to move over to lipos yet personally. (This has nothing to do with the fact that I've just bought a couple of packs of matched cells )

I think the only real disadvantages are:

- Possibly safety issues (if youngsters are using them),

- The fact that people's current cells and chargers will probably be useless if they don't have a lipo function

- Initial cost. I know the lipos won't be expensive and lipo chargers can be had for about 20 quid but this is stil a fair bit of money to younger members

This also increases the cost of progressing from the standard to brushless class. You need a diff, brushless motor + esc, lipos and a charger which is about 150 quids worth. A lot of money for what is supposed to be a cheap way into racing.

I'm fairly new to the whole lipo thing myself, but if running 1 cell at around 3.7V, would there be some sort of performance difference? I guess if there's no real difference then both lipo and nimh could be run and people could choose when and if they wanted to change over to lipos.

[Gazza]

. .

[Gary K]

Some Lipo info for you Mardave guys 'going through the change'…

Firstly, having recently converted to Lipo myself I can confirm they offer a big advantage in terms of ease of use (charged correctly of course). I use one pack all day and charge straight after the race has ended. No discharging / cycling / balancing = big advantage.

In touring cars we run a 7.4 volt Lipo (2 cells in series) which I'd say would be pretty much equivalent to a good pack of Nimh cells (6 cell = 7.2 volt nominal). I'd say a 3.7 volt Lipo (1 cell) however would be slower than a 4 cell Nimh pack as the voltage difference is significant [3.7v vs 4.8v]. 1/12th guys will probably get around this by running lower turn motors so it’s not such an issue.

In terms of cost I think you need to be careful. Personally I've got a very cheap charger from Precision RC (about £20!) which is great. A single Lipo is probably equivalent to 2 packs of Nimh cells so that’s not a big deal either. What you must remember however is that Lipo cells are in the early stages of development and the rate of improvement of new cells will mean that a new / top spec Lipo will significantly out-perform an older / lower spec version. I think it's a myth that Lipo's will level the playing field, far from it. If you want the highest performance you will have to buy new Lipo’s fairly regularly.

I hope that helps, if you want more details than please come and ask - I sit over near the main doors, spiky hair!

Cheers,
Gary.

[Gazza]

.:

[Richie]

Hi Gazza

The Lipo cell delivers 3.7 volts. My understanding is the saddle pack is two lipo cells wired in series which will double the voltage and deliver 7.4 volts. I had once been told that a 6v lipo cell was being developed but Roger dispelled that myth yesterday by confirming that a Lipo cell will remain at 3.7v. A single cell pack could be used on a Mardave at 3.7v but I don't think that is sufficient voltage to effectively run the receiver, steering servo and speed controller, it would mean an additional receiver pack would need to be used if this option was chosen, which creates more complexity and I'm not convinced is worth it.

[Gazza]

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[Richie]

Sorry Gazza

You'll have to explain this to me in a fortnight, if a LIPO cell is 3.7 volts, how do you achieve a LIPO 4.8v pack ?

[Gazza]

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[Gazza]

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[Richie]

Answered

Richard

[JamesG]

Gazza, the batteries that you've posted are made up of two cells as are all lipo packs in this area of the hobby, it would be possible to use one of the cells individually but it wouldn't be worth it as Richie has said. When fully charged they are 4.2v and must not be discharged below 3v. The voltage drop is a lot slower than with sub C's but a pack needs to be developed specifically for this area in order to be on a par with four sub C's, whether this happens is another thing though as the 1/12th scene is a lot smaller than 1/10. I hope it does happen though as lipo's are the way forward.

[Gazza]

James
Correct I just wanted to show Richard what I meant by saddle pack
also as you say 2 cells which make 7.4v its just that I cant find the HUSH HUSH LIpo that they are testing . . .
Richard and my self were thinking of a LIPO that fits a 1/18th truck http://www.actionmodelcentre.co.uk/prod ... T%2DC22824

These can fit the Mardave with the BRUSHLESS system you would need to turn the speedo down or it would be like a rocket but the down side is I WANT a HARD case type

Gazza sits back and waits for forum to go wild

[Richie]

I have to say I think the posting of these videos needs to be put into perspective. When LIPOs are charged correctly they are perfectly safe, these are being connected to mains voltage or severly punctured which creates the reaction with Lithium and atmosphere. I think this point could have been put over in a better way.