brushless ESC programmig

[bwells]

When programming a brushless Esc from NiMh to lipos, does it only activate a low voltage cutoff circuit (LVC) or does it do anything else?

[ozzie-crawl]

as far as i know thats the only diffrence

[m4a1usr]

When programming a brushless Esc from NiMh to lipos, does it only activate a low voltage cutoff circuit (LVC) or does it do anything else?

For most speedos thats all it does. And depending on the year built or software installed the cutoff voltage level may be outdated or inadequate. Some speedos you only get to pick the pack size, 2S/3S/4S/5S etc. The factory LVC setting can be as low as 3.0 vdc and non adjustable. Thats too low. Most agree the LVC should be at least 3.25 or higher. But the biggest problem with a Speedo LVC setting is it does not monitor each cells voltage level. If you specify a 4S pack all it knows is what the total pack voltage is. One cell might be 3.25 when the cut off starts but another might be 3.0 while another might be 3.4 so unless you are regular with balancing and your cells are from a known quality builder you could still have pack issues all the while believing your speedos doing its job. Which it is, just not well enough. Thats why some of us use devices like the CellShield. It simply does a better job.


John

[bwells]

Good answer, Thank you, which leads me to another question. A 2s charged thru two leads, why wouldn't it balance itself? I do have the balancing tap and a charger that does that but was just wondering why?

[m4a1usr]

Good answer, Thank you, which leads me to another question. A 2s charged thru two leads, why wouldn't it balance itself? I do have the balancing tap and a charger that does that but was just wondering why?

The reason is again because you are dealing with 2 cells. Each an individual. If as a pair they will not come up in voltage equaly they end up not acceping the same amount of energy. In theory smaller packs should not suffer ffrom this imbalance issue to the same extent as larger packs however it is still something to consider when charging or doing maintenance. Balancing is the only way to make sure each cell end up at the same level.

During discharge the weakest cell (highest IR/lowest capacity0 is going to drain the first. The strongest picking up the slack. All multiple cell packs have this issue. No 2 cells are identicle. The best we can hope for is the tolerance is so close that the worse one isnt all that bad.

John

[ozzie-crawl]

During discharge the weakest cell (highest IR/lowest capacity0 is going to drain the first. The strongest picking up the slack. All multiple cell packs have this issue. No 2 cells are identicle. The best we can hope for is the tolerance is so close that the worse one isnt all that bad.

John

not wanting to jack this thread as i have another going on balancing but iam intrested about the ir/capacity with multiple cells,i havent been blancing my lipos for some time and only ever see a diffrence of .01 volt when charged.
all my cells are turnigy or zippy,they say on the front of the cells ohm matched
thought this more a sales thing but maybe the do match them and it makes a diffrence

[m4a1usr]

maybe the do match them and it makes a diffrence

Quality made packs are matched. But there are plenty of examples where packs have had a failures related to a single cell degradation that most likely the explanation is one of them was a lower quality or mismatched. And of course theres always the issue of the one cell thats furthest from the rest that see's the most resistive path due to wire length,solder joints, etc that has the effect of having to overcome the problems when dealing with a series circuit. That outer cell is going to always be subjected to the worse effects when in discharge.

John