FXR lipo cut-off question

[mrG]

So I went to 4s in my xr recently. Seeing that the fxr is only rated for 3s do I need to set the cut-off way higher for the 4s. I have it set at 3.375 volt per cell now but the cutoff seems not to work like with my MMP on 4s. And when I plug the battery in to my charger and check the volts they are dangerously low. So this is what I'm thinking.

3.375 x 4 cells= 13.5 volts

13.5/3 cells (what the fxr is rated for)= 4.5 volt cutoff per cell, if I can even go the high.

Anyone do this or have any thoughts?

[lemonhead]

according to the FXR instructions to run a 4s

"custom led1 & led4 on user selectable using tekin hot wire pc connection"
if using a lipo battery do not operate with the factory default cutoff voltage setting

[mrG]

I dug out my hotwire and the highest you can set it is 12 volts or 3 volts per cell on a 4s

[winnerone23]

From my understanding of what you are asking.... I run my fx-r on 4s an the lipo cutoff is set on custom at 3.25 per cell. It always shuts off around 3.4 per cell tho. All I changed was the capacitor. I went with a 25v cap. This is my setup with a single fx-r in my scale rig and the same with my XR with dual fx-r an 25v cap. No issues with 4s..

[mrG]

I had mine set to custom at 3.375 but it would not cut off at that per cell. I would plug it into my charger and check the volts per cell and some would be down at 2.8 I then kicked it up to 4.5 and had the same result now its at 12 volts. Being able to go that high seems to tell me that you are setting for total pack volts not per cell volts.

[mrG]

I did go to a 25volt compacitor

[winnerone23]

You said the max is a12v setting.. If I'm getting 3.4v per cell, that seems to be 13v or so....
I'm on custom 3.25v per cell. It always shuts of early, all half dozen+ of my fx-r are that way..
Did you check other areas of this process? Batteries, charger, or double check with a volt meter?

[Poserx]

I have the same question as the Tekin instructions are a little light in this area.

Anyways, can someone confirm if the custom voltage cut-off is PER CELL or TOTAL VOLTAGE?

Judging by peoples responses it might be TOTAL VOLTAGE.

[winnerone23]

Custom is per cell, atleast with what I have mine setup as.

[mrG]

What firmware are you running?

[ninja turtle]

Custom is total pack voltage.

Originally Posted by Ty@Tekin

Ok guys, let's settle this.

The FXR does not auto-detect the voltage of any pack, nor set it's own LiPo cutoff. LVC 1 is off, LVC 2 is 6V (2s) and LVC 3 is 9V (3s). LVC 4 is custom cutoff, which is set in the HotWire. A proper voltage cutoff for a 2S battery would be 6.0V or higher and 9.0V or higher for a 3S. Setting the custom LVC to 3.6V would mean it would not cutoff power to the motor until the battery voltage dipped below 3.6V.

It does not do it per cell and it certainly isn't magical. Are you 100% sure that after you set the custom LVC through the HotWire that it didn't somehow end up on LVC 3 for 9V cutoff? That is the only way it would work.

From this thread I got some FXR ecs problems

[Poserx]

Originally Posted by ninja turtle

Custom is total pack voltage.

l

Ya it has to be. Why else would you have up to 12 volts per cell?

Must be total pack voltage.

B.

[winnerone23]

Thank you sir!
Now I'm wondering how I switch from 3s to 4s,, never touch a thing an my cell count is always around 3.4 per cell. No matter which battery I'm running... hmmmm.. I double check all "dead"bats with a digital lv checker an look at the read out on my charger..

[AddictedtoRC1]

There's a complete thread on this very subject. Custom setting is TOTAL pack voltage. Straight from the mouth of Tekin themselves.

[Poserx]

Originally Posted by AddictedtoRC1

There's a complete thread on this very subject. Custom setting is TOTAL pack voltage. Straight from the mouth of Tekin themselves.

Link?

[winnerone23]

Originally Posted by Poserx

Link?

Check post #11

[Poserx]

Originally Posted by winnerone23

Check post #11

Nice! Now it's settled. Someone should sticky that until Tekin can improve their instructions.

[tnt-salvage]

sorry if this is a stupid question, i just installed a 35v 2200uf cap on my fxr. im using the 35t heavy duty motor, i just took it for a run with a 4s 40c pack all seems to run well esc is running a little warmer then 3s use which i expected as did the motor. the question i have is will the lipo cut off detect the 4s over the 3s? i have the lipo cut-off set on custom led1 and led4 . i set the esc to this setting using the buttons on the fxr esc, i do not have a hotwire to change advanced settings threw my computer. will this still work? the 4s battery is a 4500mah so it should last a while before it dies off, i ran it for 5-10 mins to make sure i wont kill the new battery

thanks for the help

[winnerone23]

That's a Huge cap! Lol.. but will do the job, for sure!

Not sure what custom setting led1 an led4 is nut what I can say is, I have had a 4s cap on half a dozen fxr's and in all types of rigs. Scx, ax, XR, an wraith for a little while. Now a tekin RS in the wraith with a 4s cap. Not that I have used it, but I like the extra cap room/ability if need be.

Some at a 3v setting and dome on a 3.25v custom setting, thru use of the hotwire. Now, as I stated earlier, I have found the cutoff to work just fine at a custom 3.25v setting.. experience tells me, its per cell.. tekin says its per pack voltage. Well I don't argue with tekin but I have no problem sharing my experience either!
With all this said.. the lipo cutoff will work the same for 4s as it does for 2s or 3s..

If you have a lipo alarm or digital voltage checker(4$-20$) the 4$ one workz just fine! I would plug it in and give the battery a full run. You can check the lipo cutoff against the alarm or voltage checker for a batt or 3 and then you will know for sure.

[tnt-salvage]

thanks so much. i will for sure get a voltage checker and have it plugged in.

as for the cap yes its huge.... i drove around town today to find a 25v 1000uf but could not find one. i got home took apart a cd player i had laying around from one of my old cars/trucks but nothing of use, i then took my old computer tower and found what looked to be a good one but turned out to be only 10v.... getting mad i took the power suply out of the computer tower and removed a few caps and still nothing of use. there was a 50v 100uf cap or two 200v caps but there just stupid in size. so last place i checked was an old rockford fosgate car amp i had, was only a 160 watt 2 channel so i have no use for it. opened it up and what do you know two shinny 35v 2200uf caps so that was my afternoon fun