TECH TIP: HOW DO I SET UP MY ESC TO RUN HV LIPOS??

LiHV Batteries.jpg

If you are looking to improve the performance of your electric R/C car, boat, plane or heli one of the first things you should do is make sure it is getting the power it needs. If you upgrade your motor and ESC you may not see much difference if the batteries are not up to the job. It was in the early 2000’s that we saw LiPo (Lithium Polymer) batteries surge in popularity and quickly become the choice electric upgrade over NiMH cells. While LiPos require extra care and cost more, the tradeoff was the improved power to weight ratio that translated to a faster car with better acceleration.

Within the last few years we’ve witnessed yet another LiPo based battery emerge. The pack is commonly referenced as LiHV, identifying that it is a high voltage based lithium battery. Using a modified chemical composition, these batteries have a higher nominal and peak cell voltage. LiHV per cell peaks at 4.35 volts where a typical LiPo battery has a peak voltage of 4.20 volts. The nominal voltage of a LiHV battery is 3.8 volts whereas the nominal voltage for a typical LiPo is at 3.7 volts. The higher end voltage can provide your model even more power (especially as you increase the number of cells you are running), the voltage increase should give you even longer run times and the lower internal resistance (provided it’s lower than a standard LiPo cell of the same C rating) should make more power available through the entire discharge.

Some noted disadvantages of using LiHV packs include the complexity of steps required to gain the additional capacity. For example, your charger must be capable of 4.35 volts per cell and your ESC and motor must be capable of accepting  LiHV max cell count.

USING LI-HV BATTERIES WITH YOUR CASTLE ESC

There are some considerations to be aware of if you are introducing LiHV batteries into your Castle powered setups. Let’s first understand how the ESC interprets cell voltages to correctly perform Auto-LiPo Detection, which sets the cutoff value based on the detected cell count.

  • The number of Lithium Polymer cells in series in your battery pack is determined by the Minimum and Maximum voltages.

  • The ESC measures the input voltage from the battery and equates it to a number of cells based on 4.2v/cell.  

  • When you plug the battery pack into the controller it will sound the initialization tones and then flash and beep the number of cells it counted.

(As shown in figure 1.1)

FIGURE 1.1

FIGURE 1.1

The ESC’s Auto-LiPo detection is calibrated at 4.2v/cell. With HV LiPo cells charging to 4.35v/cell the ESC will think you're running more cells than you are and if left at default settings you will experience a premature cutoff based on the fact that the ESC recognizes your 4s LiHV at 4.2/per cell and not 4.35/ per cell.

(As shown in Figure 1.2)

FIGURE 1.2

FIGURE 1.2

FOLLOW THESE steps to eliminate a premature cutoff when utilizing LiHV batteries in your setup:

  1. Open Castle Link programming software from your Windows PC or via the App on your iPhone/Android and a B-Link Bluetooth Adapter.

  2. Under the BASIC tab in Castle Link you will see Cutoff Voltage.

  3. Change the cutoff voltage from “Auto-LiPo” to “Custom”.

  4. In the box to the right adjust the total cutoff voltage by multiplying the number of cells by the cutoff voltage per cell.  The default cutoff per cell is 3.2v, but always check with your LiPo manufacturer to verify their recommended minimum discharge voltage.

  5. Click UPDATE and send new settings to your ESC.

  6. If you change battery packs and increase/decrease cell count, you will need to adjust the custom setting again.  

Cutoff Voltage Custom Setting-Castle Link

Cutoff Voltage Custom Setting-Castle Link

LAST BUT NOT LEAST……

It is also extremely important to be mindful of the published maximum input voltage ratings of an ESC so not to cause irreparable damage from over-voltage. An ESC needs to be able to accept the nominal charge of the battery pack, and the amp draw.

MAMBA X AND HIGH VOLTAGE BATTERY EXAMPLE

MAMBA X AND HIGH VOLTAGE BATTERY EXAMPLE

So there you have it. You absolutely can run LiHV batteries with your Castle ESC without issues so long as you take into account three important factors:

  1. Depending on your setup, the Cutoff Voltage setting MAY need to be modified to prevent a premature cutoff.

  2. If the Cutoff Voltage setting is modified, remember to update the ESC settings if you change battery packs and increase/decrease cell count.

  3. LiHV Input Voltage MAY exceed the maximum input voltage ratings of an ESC, always do the math!

Have you run LiHV batteries in your setups yet? Drop a comment below and let us know if you recommend!

 

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