How to switch to Lipo technology?

[DuckOfDeth]

Would any one be interested in explaining to me what all is involved in switching from NiMH cells to the Lipo side of the Force?

In the famous words of Sgt Schultz (Hogan's Heroes!!) 'I know nothink!'

I am interested in learning what safety precautions need to be followed, what hardware is needed, and how to figure out what configuration would be needed to match 18 NiMH cells.

i'm sure that this has been covered before, and if this is the case, simply linking me back to the posts, will suffice.

Many Thanks,

Duck

[saleens7]

a 6s lipo would be close to a 18 cell pack (little more voltage though)

you will also want a low voltage cutoff for your lipos if your esc doesent already have one....

[DuckOfDeth]

Saleens,
Fill me in on the low-voltage cut-off, and what it does. I am currently running the CC 125, which to my understanding, has a programmable low-voltage cut-off.

Duck

[saleens7]

the low voltage cutoff cuts off the current to the motor if one of the cells or the total voltage in the pack gets down to a certian level that it will damage the cell if it goes any lower...

i.e. if any cell should get below 3.4v (3 volts it usually the norm, but its a lot safer to have it at 3.4 volts) it will cutoff the current from the pack to the motor.

[DuckOfDeth]

Can you explain how many volts each cell holds charged? And here's a real doozie, what does the 'S' or 'P' stand for that I have seen posts about?

Many Thanks,

Duck

[NorthernBoater]

The highest cut-off on the hydra was a 12 volt cut-off. You will most likely need the computer link with the CC 125 to set it any higher than 12 volts. You will also need a LiPo balancer to plug in between your batteries and charger.

[saleens7]

's'= series

'p'= parallel

so a 4s2p pack is two 4s packs in a parallel to put out the same voltage as a 4s pack, but twice the capacity ratings...i think thats how its supposed to be anyway

[NorthernBoater]

Actually a 4s2p pack is 2 4s packs in parallel. If you are doing sport running and not drawing a lot of current each pack will see half the current which will extend the life of the pack.

[DuckOfDeth]

Do you set the low voltage cut-off for the pack, or for the cell? What does the balancer do during the charging process? I realize that might sound like a stupid question as the word 'balancer' should be self-explanatory, however, I'm not sure what I am balancing.

Excuse my ignorance, but are the packs made of individual cells, similar to how a NiMH pack might be setup? Is the 6s made up of 6 cells, that simply have a higher voltage capacity than a NiMH cell?

Duck

[DuckOfDeth]

Explain the difference between running in series vs parallel? I would fall in to the catgory of sports boater, as only one other friend is into boats, and there are no FE or even boating clubs in the Kansas City area, to my knowledge.

Duck

[saleens7]

yep..6s is six lipo cells (each cell has 3.7v)

[saleens7]

Explain the difference between running in series vs parallel? I would fall in to the catgory of sports boater, as only one other friend is into boats, and there are no FE or even boating clubs in the Kansas City area, to my knowledge.

Duck

if you run two 4s packs in a series, you essentially running 8s...if running two 4s packs in parallel, you only have the voltage of one 4s pack put double the mah, current capacity, and C rating...

[saleens7]

Actually a 4s2p pack is 2 4s packs in parallel. If you are doing sport running and not drawing a lot of current each pack will see half the current which will extend the life of the pack.

oops...typing faster than i can think (again)

[NorthernBoater]

Yes the 6s is referring to the number of cells which is 6 in this case.

You set the low voltage cut-off for the pack. For a 6s pack the lowest you would set it is 18 volts which leaves each cell at 3 volts. It is a good idea to set the low voltage cut-off at 3.4 volts a cell because not all the cells will discharge the same. So if you set it at 3 volts after a run 5 of the cells could be 3.1 volts and the 6th cell would be at 2.5 volts which will most likely damage that cell.

The balancer will make sure all cells are at the same voltage when they are fully charged. If you look at the diagram of the balancer on the last page of the manual for the Hyperion balancer it shows a wire connected in between each cell. From what I understand this will cutoff the voltage to each individual cell when it is at the correct voltage.

http://www.battlepack.com/rclipo/lba10.pdf

[NorthernBoater]

if you run two 4s packs in a series, you essentially running 8s...if running two 4s packs in parallel, you only have the voltage of one 4s pack put double the mah, current capacity, and C rating...

Less current draw from each pack == less heat generated in each pack. This is one big advantage with running in parallel.