when using a gfx is it a good idea to solder the voltage leads to the main clips like a much more charger?

or is it a bad idea? use the clips on both...

thanks

signed the rookie

It's more accurate if you clip them to the battery bars.

Mine Are Soldered Together And So Is Everyone Elses At Mtr

Clip on separately. Big difference when cycling a pack.
Rookies... You never know what they will ask!

I'm glad someone brought this up because I have asked the question for years. How can it possibly make a difference if you solder the two together? You are clipping two leads to the same place.

If it's better to keep both clips, someone please explain why.

How can it possibly make a difference if you solder the two together? You are clipping two leads to the same place.

If it's better to keep both clips, someone please explain why.

My thoughts also............

It would seem to me that using both clips would be less accurate because you have two sets of contacts on the bar instead of one. I've had mine soldered without problems.....

I can't explain why it makes a difference, But it does. I cycle a pack with the leads soldered together, and then cycled separatly. The Cycle with the leads soldered together the readings were real low. the cycle with the leads separatly the numbers were alot closer to the numbers on the pack.

i have heard the same thing jerry..i think danny at smc said it does make a difference.

BUT if you just cycle your own packs and keep your own numbers and don't care how they match up to another racers pack..than your ok i guesss?

thanks for the replies

Here is how I understand it, I hope I can do this justice. Also you can test this by touching the leads to the Larger clips and to the bars themselves and see a voltage change. I would suggest doing it on charge or in a steady part of the discharge cycle so you can see the difference.

If you solder the smaller "sensor wires" to the clips they are "more in the circuit" than just monitoring. I realize that electrically, this is the same point. But from my experience in not only this application but in others. If you are wanting to monitor a circuit, you want to connect as close to the "Source" (the battery itself) as you can rather than the "Load" (the LARGE clips on the GFX).

This is by no means an argument, I really want to know. I’m a Spa (Hot Tub) Technician and I deal with electrical circuits every day and I just can’t see any basis for a difference, in fact it looks like to me that you have more of a chance to get an error in your readings.

Let’s take this one step further. What if you cut the alligator clips off both of the leads and solder them to the battery terminal without them touching each other. This should be zero resistance and yield 100% accuracy (except the line loss). BUT just as when you use the clips and attach them to the battery terminal, the two leads to not physically touch each other but in both cases they “electrically” do because they are attached to the same piece of metal and there is no resistance between them.

Ive been told the same thing to cycle them with the clips. I just bought a orion advantage, it has the wires soldered on the clips. Id think the numbers would be less acurate with the wires clipped on. What if you had a bad connection? I have a spintec, i know about bad connections:(

McLin -- I work with Elevator drives all day, both AC and DC. I know that when we are working with the sensors, it matters. I know what you are saying, like I said, electrically, that is the same spot. But as far as measuring it is definately not. What the difference is that the "sensing circuit" is "seeing" I really do not know.

But I did go to the Competition Electronics website and download the GFX-35 Manual. Here is what it states about the leads and what I attempted to explain but did a poor job of.

First of all, you’ll notice that your T35-GFX
has four leads. This is no accident. One of the
things that set your T35-GFX apart from the
competition is that it has a set of separate,
smaller “sense leads”. Why? Ohm’s law tells
us that where there is a higher current flowing,
there will be a greater voltage drop across any
resistance in the circuit under observation. In
this case, most of the unwanted voltage drop
occurs directly at the mechanical connections
between the large, hi-current leads and the
battery pack. This can be minimized by
making better connections, but the fact is that
there will always be a voltage drop at the connections, because of the high current
flowing during charge or discharge. That is why we have the additional small sense leads.
These leads are designed specifically for measuring, and will have essentially no voltage
drop at all, because the current flowing through these leads is relatively low. The
advantage of this is that they can measure the voltage far more accurately. So in general,
it’s best to always use the sense leads. However, the sense leads are not absolutely
necessary for a charge cycle. Although the
readings will be slightly off, it will not
affect the amount of charge delivered to the
pack.
And another thing: it is critical that the
sense leads be connected directly to the
pack/motor solder tabs, and not clipped
or soldered to the large leads. If you do
this, you will defeat the purpose of the sense
leads and they will do you absolutely no
good.

I say they should not be put together because Jim at Comp Electronics told me so. :wave: I dont know why it is, but they do read different from what I have seen.

Scott, now THAT makes sense, I had not considered the voltage lose situation, especially on discharge. But I have to also agree with Katf1ish, unless you are keeping super accurate records (especially at the racetrack) I would still put them together. We are not talking about something that will hurt the charger at all, just a difference in cycle readings.

But thanks for that post, at least now I know what I am by passing LOL

I have an old T30 and I know while breaking in a motor if I had the small leads hooked to the large leads the voltage to the motor never seemed really consistent. Amp draw was all over the place.
However If I hooked them up independently to the motor, the motor ran much smoother and showed a higher amp draw.

I never noticed this as much with the GFX's though.

is does not matter so much on the charge mode as the discharge mode it does matter. you will get more of an inaccurate reading on discharge mode with sensor leads connnected to the main leads. When in charging mode this does not accure..

JP

I just did some cycling last night. i have two brand new 4 cell packs. On the same charger one night, i did a test. Both packs were really close in numbers with each other. I did another test last night. Cycled one on my gfx with soldered sense leads, and one on my gfx with separate sense leads. the one on the soldered leads showed 0.14v less average voltage during discharge. now .14v is not much but to some people it will make a difference. The AIR on the soldered one was 10.4 vs 6.3. So it makes a big difference on that.

but like was said earlier, if you are not trying to compare your packs to someone elses, it does not matter. Normally i solder my sense leads to the large clips. Mainly because it is easier. You WILL NOT hurt the charger, your numbers are just going to be "off".

You WILL NOT hurt the charger, your numbers are just going to be "off".


To me, because I'm an old fart, if I spend a lot of money on a quality
piece of equipment, I don't want it to be off.
That was the purpose of buying a nice unit.
IMO of course.. ;)

To me, because I'm an old fart, if I spend a lot of money on a quality
piece of equipment, I don't want it to be off.
That was the purpose of buying a nice unit.
IMO of course.. ;)

I understand you there. No debate whatsoever. Its just for the track, it is easier for me to solder them together. Then, when i do cycle, to see the correct numbers i just unsolder them from the charge leads and hook them directly to the pack.

my opinion of why you get more accurate readings with the sensor wires seperate from the big gator clips is because, the sensor wires "sense" the load of the charge pulsating through the gator clips when they are together. the sensor wires "sense" the load of the discharging current, when they are together with the big gator. the biggest thing to remember is that sensor wires are named so because they "SENSE" everything, good and bad, or right and wrong currents. when we cycle a battery, we want to know what the battery is doing. not what the charger is doing. so hook them to the battery bar seperate from the big gator clip.

ps. i could be totally wrong here but its how i think of it.

I'll put my 2 cents in:

If you solder the sense leads to the clips, the voltage they measure is lower by the amount of voltage drop across the alligator clips and the clip/battery bar interface.

So that is why the voltage that CClay1282 measured with the sense leads soldered on was .14V lower. [taking an average] There was .07 volts drop between the place where the sense leads were soldered on and the battery bars on each lead (.07 for each lead times 2).

Mine Are Soldered Together And So Is Everyone Elses At Mtr



Just because they are doin it doesn't make it right. it's the little details like this that seperate the Men from the Boys

...so the question then -

Which of these methods will be more apt to cause a GFX to "Over Charge" a LIPO battery ;)

From what I was told, the small leads only come into play when discharging, NOT charging.

The small leads make a difference whether you are charging or discharging. This makes no difference for charging NiMH because the absolute voltage level is irrelevant to peaking a NiMH battery.

It is easy to see this if you still have the sensor leads separate. Hook up the main leads and look at the voltage display. Then hook up the sensor leads one at a time. The voltage will go up a little bit as each sensor lead is hooked up. It is easier to see on a single NiMH cell than a whole pack because there is an extra digit in the voltage display when the voltage is under 2.0V.

So since the voltage reads lower (we could say "than it actually is") without the sensor leads than with, charging a LiPo without the sensor leads will have the battery end up with a higher final voltage than if they were connected. For charging though, the difference between having the sensor leads separate and soldered to the alligator clips (or whatever) is less significant since the current flow (and voltage drop) is less.

I have kept my sensor leads separate but only use them when cycling a pack. For batteries that have connectors, I have made adapters that allow me to connect the sensor leads to the connector to get an accurate voltage at the connector (best you can do in that situation). I just tried this on my GFX and while charging a pack, the voltage goes up when I touch each sensor lead to the battery terminal. But it only goes up about .02V when connecting the negative sensor lead while it goes up about .10V when connecting the positive sensor lead.

For LiPos, I think the Hyperion chargers with the built-in balancers are better than the GFX because the charger reads the voltages of each cell through the balance leads, kind of like the sensor leads of the GFX, but with one for each cell.

T35-GFX
has four leads. This is no accident. One of the
things that set your T35-GFX apart from the
competition is that it has a set of separate,
smaller “sense leads”. Why? Ohm’s law tells
us that where there is a higher current flowing,
there will be a greater voltage drop across any
resistance in the circuit under observation. In
this case, most of the unwanted voltage drop
occurs directly at the mechanical connections
between the large, hi-current leads and the
battery pack. This can be minimized by
making better connections, but the fact is that
there will always be a voltage drop at the connections, because of the high current
flowing during charge or discharge. That is why we have the additional small sense leads.
These leads are designed specifically for measuring, and will have essentially no voltage
drop at all, because the current flowing through these leads is relatively low. The
advantage of this is that they can measure the voltage far more accurately. So in general,
it’s best to always use the sense leads. However, the sense leads are not absolutely
necessary for a charge cycle. Although the
readings will be slightly off, it will not
affect the amount of charge delivered to the
pack.
And another thing: it is critical that the
sense leads be connected directly to the
pack/motor solder tabs, and not clipped
or soldered to the large leads. If you do
this, you will defeat the purpose of the sense
leads and they will do you absolutely no
good.

I know one thing I did when we ran mod with 4200's I would keed melting the solder of my clips so I just soldered my leads directly to the battery. the large lead to were you would solder the speed control. the small senseing one to the top of the bar not touching each other. I worked good till melt down with 4200's one day GFX and all out the door....

Ritchie Mac

...so the question then -

Which of these methods will be more apt to cause a GFX to "Over Charge" a LIPO battery ;)


In my experiance if you charge your Lipo in Lipo mode on a GFX 35 and leave the small sense wires off the battery will gain approx .01 to .05 this is on a 3200 Lipo I havent messed with anything else. So a battery that charges to 8.40 volts can be made to go to 8.45, Not really serious OVERCHARGING IMO.
You can REALLY OVERCHARGE a Lipo with a GFX, I,ve seen as much as 9.00 volt....you dont want to do that.

...so the question then -

Which of these methods will be more apt to cause a GFX to "Over Charge" a LIPO battery ;)

When charging a Lipo pack on the GFX in Lipo mode here is what you will find:

8.40 top off with both sonsor leads hooked up
8.44 top off with only negative sensor lead hooked up
8.50 top off with only positive sensor lead hooked up
8.55 top off with both sensor leads removed

When charging a Lipo pack on the GFX in Lipo mode here is what you will find:

8.40 top off with both sonsor leads hooked up
8.44 top off with only negative sensor lead hooked up
8.50 top off with only positive sensor lead hooked up
8.55 top off with both sensor leads removed

Tony (aka. the man with all the numbers) - now that you have the cycel numbers which method runs better on the track?
I know you have excel graphs and charts with the answers !!!
lol

Tony (aka. the man with all the numbers) - now that you have the cycel numbers which method runs better on the track?
I know you have excel graphs and charts with the answers !!!
lol

8.55 without a doubt. I've tested up to 9.25 and boy does it fly! :woohoo:

what's the reason for not letting the peak voltage of a lipo go above 8.44

hmmm explosion........overcharging a lipo can cause they to explode catch fire burn your pit trailer down you know bad things....so 8.44 is the cut off that all tracks should use and should be doing tech before racers race to promote safe use of a lipo pack.

i would have to say eithe 8.40 or 8.44 because the others are over the legal limit

I'll put my 2 cents in:

If you solder the sense leads to the clips, the voltage they measure is lower by the amount of voltage drop across the alligator clips and the clip/battery bar interface.

So that is why the voltage that CClay1282 measured with the sense leads soldered on was .14V lower. [taking an average] There was .07 volts drop between the place where the sense leads were soldered on and the battery bars on each lead (.07 for each lead times 2).

You right by adding some resistance on the smaller wire (voltage sensor leads) the CE GFX will overcharge lipos to a slightly higher voltage up to .5 of a volt.

It will also do the same thing without the leads connected in a defalt mode.

so will it kill the lipo or cause an explosion to let it charge to 8.55?? I would not thinnk so, but with lipo don't know.. I know sum have done it with no issuse

It shouldnt. Think about this, if lipos were only suppose to be charged to 8.4 and knowing todays racers, the manufactures would tell you the max is 8volts. They are not going to push the batts to the limit. Noone does when the manufacture anything like this. They are going to be on the safe side.