Spartan LVD Cutoff
My Traxxas Spartan has worked well with my Traxxas 3S 5000mah 25c lipos until about a week ago when they both puffed. I talked to Traxxas to see if I could return them under warranty but they said that the only reason lipos would puff would be because of overcharging or overdischarging. Is it possible that the Spartan is allowing the batteries to over discharge? When is the ESC programmed to activate LVC and can it be adjusted? I really dont want to puff my new set of lipos .Any replies would be appreciated. Thanks!
You can connect the ESC to Castle Link and modify the cutoff voltage. I've upped mine to 3.4v / cell I believe (been a while since I've messed with it).
Also remember that the Spartan LVD will reset when you let off the throttle. So if you hit full speed and the boat appears to cut out, you left off and get back in it again it'll run almost up to the same point because it's reading the real-time voltage under load. Off load the voltage recovers and resets the LVD. If you keep driving slower you'll be able to run longer, but put your batteries at a much higher risk for voltage issues.
wow thanks tire slinger i didn't know we could hook the esc up to the castle link and adjust it.spc recommends that when using their batteries you set lvc to 3.5 or well all lipo batteries
I would recommend setting it at about 3.6-3.8.
+1 for 3.6-3.8v. I dont like when mine drop below 3.7vpc.
Rule of thumb is you do not want to use more then 80% or your lipos capacity. If your batts are 5000mah the most you should use is 4000 of the 5000. Best way to check is when you recharge. If while charging you put say 4500mah in then you should up your lvc setting because your pulling to much out.
For me with my 5000mah packs it is around 3.7-3.8 volts per cell.
Last edited by ttypedan; 07-04-2014 at 02:08 PM.
I think you will find settings of 3.6 - 3.8v will be too high, and your LVC will be cutting in too soon, possibly every time you accelerate hard.
Generally speaking, if your LVC is working reliably, an LVC setting of 3.4v should be adequate, and is the most commonly recommended setting.
Fully charged an individual lipo cell has 4.2v "static" charge, and a nominal "load" voltage of around 3.7v. Risk of damage to a cell due to over discharge is generally considered to be 3.0v or less per cell.
The moment you put a load on the battery the voltage will drop, the more load, the more it will drop. (the amount it drops is also dependent on C rating of the battery). Your 4.2v static cell voltage will drop to 3.8-4.0v (or possibly more) under load depending on how much load is applied, and the ability of your battery to deliver power (C rating)
Setting your LVC too high could result in it activating on, what is essentially, a fully charged battery.
The "plateau" voltage (or operating range voltage) will hover around 3.7-3.8V to 3.3-3.4v for several minutes, then it will drop like a rock.
It is the propensity of Lipo batteries to quickly discharge at the end of the cycle that makes damage due to over discharge such a risk.
What is difficult to determine is what voltage "threshold" gives you enough power to "get home" without putting a damper on your fun.
Yes, it is worthwhile to consider setting the LVC a bit higher to provide a bit more of a buffer to protect the batteries, but you also want to maximize your RC enjoyment.
Boats are probably the toughest to determine an optimum setting. Because they are power hungry and draw very high amps, the voltage drops will potentially be greater, so premature LVC activation is more likely with higher settings. However, due to their power hungry nature, it is also wise to consider keeping a bit more "reserve" power for getting home.
If you want to increase LVC setting, I would suggest bumping it up from 3.4 to 3.5v. The important factor being, regardless of your desired set point, is respect the lvc, when it activates head for shore immediately at part throttle to minimize the load on the battery when it is most vulnerable to damage.
Last edited by hog; 07-05-2014 at 10:45 AM.
To add to Hogs post, keep an eye on how much mah you are putting back into the battery while charging. If you are putting more than 3000mah back in a 5000mah pack you are over running your packs and you WILL ruin them.