what are lipos=too?
 

are 3200 lipo packs equal too 3200 nimh cells? or do they work out different?

Lipo packs are similar capcitys so 3200 lipo is the same as 3200 nimh the only diffrence is nimh you loose performance though out the run lipo you dont.

A

so would you use higher rated packs for more run time? oh,as anyone tried lipos in a xx4 yet? do the battery clamps need work on them to get them to fit? so many questions!!!!!!:thumbsup:

I can see your logic, but no. Will try and explain, but please do ask any questions if I don't cover it.

Nimh cells self discharge, so if you charge a 3200 pack to 3400 (200mah wasted in heat and resistance), then by the time you reach the track, that pack may have 2900 or less in it, plus it will consume more mah due to it getting hot during a race.

Just try fully charging your own cells, let them cool, then discharge to 6v at 10amps continous and they won't discharge the full mah capacity that you put in ;)

Whereas Lipos, if you charge 3200, they will have 3200 in them when the car is on the track, a few mah may be wasted in heat but these cells will get no hotter than mildly warm under normal circumstances so there is little mah wasted if atall. They do not self discharge over time either. For example, I went to Belgium last week and while I was setting up, I thought id put a pack on charge which I knew id charged fully a week ago - and they literally went off charge within 5 seconds...... i.e. they hold there charge over long periods.

Realistically, a brushless car with a 6.5R Novak will consume 2000mah over a 330 second race. This is not based on calculation but based on my experience. Therefore, a 3200mah pack is more than adequate.

if you go for a higher C rating pack, then the continous ampage draw is higher and they'll discharge quicker in the car - which will result in a faster car, therefore you are likely to motor down or drive smoother and still only use 2000mah. ;) :thumbsup:

A 3200mah 20C Lipo pack, will make the car around 150g lighter (approx'), and the power they give is as good as the first charge on top spec Nimh cells if not slightly better. But this power does not deteriorate, after 6 months your Lipo should (if you haven't killed them by charging wrong/over discharging) be as powerful as the first charge (mine are).

The capacity number mAh (milli amp hours) is a measure of the energy stored in a cell. A 3200mAh lipo will have the same amount of energy in it as a 3200 NiMH but as Ash said, it will deliver it differently. A lipo of the same capacity will be smaller and lighter (excluding any hard casing).

Also, I believe the internal resistance of a Lipo is less so less of the energy will be lost to heat in the cell itself, but don't quote me on that.

thanks guys,next question is....are all lipos the same no matter what company they came from? i using a much more ctx charger.does anyone know if this would charge lipos?

I don't know. My experience is only of Trakpower and I can highly recommend.

What I do know, is 3200 is quite a thin pack (stick or saddle), the 4800 & 4900 packs are quite a lot thicker and heavier - although still far lighter than any pack of Nimh cells.

Regarding your XX4, you will have to dremel off the points from the underside of the cell brace, but a 3200 saddle will fit directly in. The 4800 saddle may be too tall but with some modifications should fit.

Chris

Garry - A LiPo behaves very differently to a NiMH or NiCD during a charge cycle and will become dangerously unstable if you overcharge it. Bear in mind that all delta peak chargers are effectively over charging the cells and relying on a voltage drop to cut out. Do that with a LiPo and you'll have some nasty and unstable chemicals on your hands (hopefully not literally)

Do not charge a LiPo with anything but a LiPo compatible charger - if your charger is compatible, it will have a LiPo charge mode. If it hasn't - you'll need one regardless of actual cell make.

Quite right. If your charger has Lipo mode, and doesn't hold it when power is lost - then do not use it. Ive heard of this and it didn't take long for the pack to be rubbish. If your charge is compatible, do take great care to select the right mode, i personally prefer to use a Lipo only charger - they are cheaper than the replacement pack if forget to check the settings.

Whilst we're on the subject of charging, current 'best practice' advice would suggest a maximum charge rate of 1C for a LiPo cell.
If you're confused about the 'C' rating - 1C is the equivalent of 1x the pack capacity. i.e. 1C for a 3200mAh = 3.2A whereas 1C for a 5000mAh pack is 5A.

I have a Core RC UDC20 Balance Charger - it does NiMHs and a load of other stuff too. Would highly recommend it for anything and especially LiPo. For £54.95 it's good value - especially as it has a balance charge mode and comes with a stack of different balance leads.

I have attempted to fit the 3200 lipo saddl einto xx4 and it will fit with a little dremmel work wat i did was flip the straps over and use them up side down with a small bit filled off the bottom but you will need to dremmel the straps so you cna plug it in as i realised when i went to test run it i put the pack in went ot plug it in and realised i couldnt :p

A

so the 3200's are roughly as tall as NIMH, and the 4800's are taller?

Hi mate, The 3200 stick and saddle packs are not as tall, the 4900 stick is approx right, the 4800 saddle is slightly taller.

all dimensions are here www.trakpower.co.uk

important, sound advice :thumbsup:

when running LIPO, you have to let go of all the nicad/nimh charge at a zillion amps then discharge voodoo crap. there's no need to use higher charge rates - the punch is the same at 1 amp or 3.

you can't go wrong with any of the trakpower cells - i've been totally blown away by the consistent performance, silly run times - 10+ minutes with a 6.5r in my b44? using the 3200 saddle packs - and no signs of dumping? bonkers!

thanks andy.guess ur going faversham next weekend? got lots to ask!!!!:thumbsup:

I'm just trying to decide which saddle packs to get, could someone confirm that the only benefit of the 4800 over the 3200 is longer runtime?

4800 will have more punch too

Check the dimensions on www.trakpower.com, as the 4800 pack is taller, I don't know what car you run to say if we've seen them fitted before.

Thanks, currently have B44 & B4. I know that the 4800 can fit, but is it significantly more punch or is it really runtime that makes the difference?