I'm going to try and hijack my own thread here since I've been getting some good responses.
Could somebody explain this to me, on the HiTec RDX 2 Pro Charger, the default settings are as follows:
Nominal Voltage: 3.7V
Max Charge: 4.2V
Storage Charge: 3.8V
Max charge is just the charge setting, why would charge and storage settings be above nominal? That makes no sense to me. I can override but it seems weird that it's so high. Do you typically reprogram chargers for specific batteries?
Also, I just connected a 2S battery charged to 8.4V to an ESC rated for 7.2V. I assumed it would only charge to 7.4V which I figured would be close enough.
Seems to be working (as is the motor) but the servo is only humming. It only worked a few times before it stopped.
My initial thought was overvoltage but it looks like the voltage output to the RX is regulated by the ESC. Is it correct that the servo gets the same voltage as the RX? My TX shows me the RX voltage, it was never above 6.2V so I would think it's OK.
The servo itself was never connected to anything, so no load. Would it be best practice to set servo limits in the TX before starting to try and operate it, or are they all 'standard'? I think I can do that in my TX, not sure yet. Wondering if I didn't crank the servo too hard one way.
Anyway, any input would be great.
Ok, Theres a fair amount to unpack here...
Could somebody explain this to me, on the HiTec RDX 2 Pro Charger, the default settings are as follows:
Nominal Voltage: 3.7V
Max Charge: 4.2V
Storage Charge: 3.8V
Max charge is just the charge setting, why would charge and storage settings be above nominal? That makes no sense to me. I can override but it seems weird that it's so high. Do you typically reprogram chargers for specific batteries?
Let me start off by saying that it would be extremely helpful to know the exact make and model of your ESC, motor, servo, and lipo. That being said I can address the questions in generic terms. Also TLDR; Dont change those settings in your LiPo charger.
So Nominal voltage is a value assigned to a circuit or system to designate its voltage class conveniently. Nominal voltage is used as a voltage reference to describe batteries, modules, or electrical systems. A LiPo can operate in a range of voltages. for a single LiPo cell that voltage range is 3V/C (3 volts per cell) to 4.2V/C. So some electrical engineering geeks somewhere decided that Lithium Polymer batteries should be designated as 3.7V/C nominal.
4/2V/C is the maximum charge that a LiPo cell can have so thats why your chargers max charge is set to 4.2V. This you do not want to change unless you're using HV (High Voltage) LiPos but thats another conversation altogether. Also just like going over 4.2V/C will damage a cell, Going under 2.6V/C will also damage LiPos. Now there will be some debate about the 2.6V/C. Most people will tell you its 3.2V/C. While it is advisable not to run your ESCs LiPo voltage cut off less than 3V/C (again most people will tell you 3.2V/C). This is due to voltage sag and not wanting the LiPo cells to even get close to that 2.6V/C where they get damaged. I personally run mine at 3V or 3.1V/C cut off. Most people run 3.2V/C or some people even higher.
The 3.8V/C storage charge is just because this is where the aforementioned electrical engineering geeks determined it to be the safest for the cells while sitting unused. You see if you let your lipos set at max charge for more than a few days it begins to degrade the IR (internal resistance) of the cells. Those will also happen if the battery packs sits with to low voltage also.
The higher the IR of the cells the worse your lipo will perform. The IR of your LiPos cells is the life blood of your lipo. The higher the IR of the cells the less the LiPo is capable of and the more "stressed" the cells are. Cells that are stressed to much can actually suffer a catastrophic failure which means that at the very least the cell(s) will swell, Sometimes if they swell to much they can rupture and catch fire. LiPo fires are no joke so heres my best advice I can give you on how to keep protect yourself and you property as much as possible.
THIS is what a LiPo fire can look like and bear in mind that the LiPo catching fire here is a small 1500mAh LiPo. If you're doing ground kits then most likely you are using a much larger 5000+mAh LiPo.
First and foremost you need to make sure you are charging your LiPos in your garage or outside and the LiPos should be in a fire proof container. They make "lipo charging bags" but imho theyre a pain in the but and I just charge mine inside an old empty ammo can in a place where theres nothing flammable within at least 2 or 3 feet of your LiPo.
In addition to that precaution never used LiPos with puffed cells and make sure you buy a quality charger that can read IR of your LiPos. Progressive RC makes a stand alone IR dyno tool but its just as expensive as a good charger. I would suggest something like an iCharger and just every time you charge your lipos check your IR readings. If one cell has a signifcantly higher IR than the rest the LiPo is not safe to use. Beware cheap Chinese chargers, even the ones that can read IR. Hitec is a quality brand so you're good there but I'm uncertain if that model reads IR or not.
Also, I just connected a 2S battery charged to 8.4V to an ESC rated for 7.2V. I assumed it would only charge to 7.4V which I figured would be close enough.
This entire sentence doesn't really make sense to me so you may want to restate this if your questions are not answered here. So to start you're saying you hooked an 8.4V (fully charged lipo) up to an ESC rated for 7.2V. ESCs are generally rated in what LiPo cells you can run through them. For example an ESC might be compatible with 2-4S LiPos or 2-6S LiPos. Even if you had an ESC that was only 2S compatible Then it will funtion on 6-8.4V. See why that part doesn't make sense? Second thing is after that statement then it says "I assumed it would only charge to 7.4V" but ESCs dont charge LiPos. So this particular part I can't really address because I'm not sure what you really meant.
Seems to be working (as is the motor) but the servo is only humming. It only worked a few times before it stopped.
My initial thought was overvoltage but it looks like the voltage output to the RX is regulated by the ESC. Is it correct that the servo gets the same voltage as the RX? My TX shows me the RX voltage, it was never above 6.2V so I would think it's OK.
Ok, so as to the part of this question that has to do with whether voltage is regulated by the ESC. The answer to that part is, "yes it does". ESCs have whats called a
BEC (Battery Elimination Circuit) built in to them. The BECs job is to take whatever the LiPos voltage is and output an amount common for RXs, servos, and anything else plugged into the RX. This is typically 6V the vast majority of the time. It can sometimes be lower or higher depending on what electronics you're running and wether or not you can control the voltage output of the ESCs built in
BEC. Generally you can't control it or may be limited to 2 options. For more control over voltage output for specialized projects an external
BEC may be used. Cheap BECs are generally only switchable between 5V and 6V but high quality BECs like the ones made by Castle Creations have all kinds of voltage levels you can pick. External BECs are a tad tricky to wire up though so make sure you watch a good how to vid or make sure you ask here in the forums.
As for why your servo stopped working I couldnt even begin to guess, especially with out knowing all the details about your electronics etc.
I hope this helps. If anything is still unclear or you have more questions let me know
