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Old Jun 07, 2008, 03:29 PM
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JWilliams2's Avatar
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GWS 35 amp: how can I lower the LVC?

I have a new GWS 35amp controller and no programming card. The "manual" talks only of setting the throttle position, but for some insane reason, on three cells this has the LVC default to a 3.5 volt LVC (which is very high for an under-load cell).

Is there any way to lower this without a programming card?
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Old Jun 07, 2008, 07:28 PM
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Bruce Abbott's Avatar
Hastings, New Zealand
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The ESC-35A has a fixed cutoff voltage of ~2.9V per cell. If yours really does cut off at 10.5V on 3S then either it is faulty, or it's set to NiMH mode (unlikely as the default is Lipo mode, and you need the programming card to change it).

How did you test the cutoff voltage? What battery, motor and prop are you using?
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Old Jun 08, 2008, 06:21 AM
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Quote:
Originally Posted by Bruce Abbott
The ESC-35A has a fixed cutoff voltage of ~2.9V per cell. If yours really does cut off at 10.5V on 3S then either it is faulty, or it's set to NiMH mode (unlikely as the default is Lipo mode, and you need the programming card to change it).

How did you test the cutoff voltage? What battery, motor and prop are you using?
I'm using a high kv outrunner with a fairly small APC prop and a fresh 3S loong max pack, 2250 size. I'm only pulling about 15 amps on it (and I know from another plane the pack can easily do 20-25+) before hitting the LVC. I am using an inline eflite watt metter and if I very gradually increase throttle so that I can slowly see the volts drop, as soon as they hit 10.5, the motor cuts out.

That is a shame that the programming card is needed to do anything else with this. I tried a 4S a123 pack and the thing baulked and would not arm. My presumption is that, although it's a 2-4S ESC, the A123 voltage that sits between 3s and 4s lipo just makes the thing upset. Is that expected behavior? If it was set to NiMH, 4S A123 matches basically dead-on 10 nimh cells, so it shouldn't throw a problem.
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Old Jun 08, 2008, 10:34 AM
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Bruce Abbott's Avatar
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Quote:
Originally Posted by JWilliams2
I tried a 4S a123 pack and the thing baulked and would not arm. My presumption is that, although it's a 2-4S ESC, the A123 voltage that sits between 3s and 4s lipo just makes the thing upset. Is that expected behavior?
Yes. It also proves that the ESC is in Lipo cutoff mode.

When the ESC detects low battery voltage it lowers the throttle position, which usually allows the motor to keep running at reduced rpm. If it 'cuts out' then it may be shutting down for another reason such as over-current, over-temperature, or a noisy throttle signal. In some circumstances it will also beep to tell you why it shut down.

Exactly what motor and prop are you using?

What is the expected full throttle current draw?

Does the ESC make any noises after cutting out?

Quote:
[It's] a shame that the programming card is needed to do anything else
Yes it is. At least you can't accidentally screw up the settings. Some other ESCs also need a card. Then there are some that have few programmable settings, incorrect or missing instructions, or are not programmable at all!
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Old Jun 08, 2008, 12:59 PM
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Quote:
Originally Posted by Bruce Abbott
Yes. It also proves that the ESC is in Lipo cutoff mode.

When the ESC detects low battery voltage it lowers the throttle position, which usually allows the motor to keep running at reduced rpm. If it 'cuts out' then it may be shutting down for another reason such as over-current, over-temperature, or a noisy throttle signal. In some circumstances it will also beep to tell you why it shut down.

Exactly what motor and prop are you using?

What is the expected full throttle current draw?

Does the ESC make any noises after cutting out?

Yes it is. At least you can't accidentally screw up the settings. Some other ESCs also need a card. Then there are some that have few programmable settings, incorrect or missing instructions, or are not programmable at all!
It's this motor (not from that source, but the same motor, give or take a few % in kv) with a 4.75X4.75 APC prop.

I expected full current around the figure there (27 amps). This morning using another ESC, I hooked it up and with this battery it peaked at 30 amps and then gradually started to drop, but battery voltage stayed above 3v/cell for a while, so everything was peachy and as expected.

Regarding the cut off, I am pretty sure my 15 amp GWS esc does the same thing; it will completely cutoff without a soft slow down. I know for sure my towerpro 30amp (what I used this morning) cuts off once it hits LVC hard instead of a gradual spin down, though I do have other escs that do the gradual reduction.

The ESC makes a noise when cutting out. If my vid camera was working properly i'd tape it. It beeps a bit and then if I lower throttle and wait a moment it will spin up ok again. I thought it may be heat related but it does it even if cold and i quickly spin up.

Thanks for your help! It seems I may be stuck getting a programming card or selling this one. I like the stats on this esc but really don't want to get a card right now.
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Old Aug 02, 2008, 08:24 AM
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Update, I bought the programming card and set this to NiMH. On 4X A123 that I started at 13.64 volts (a touch under full charge), it started to hold steady at 8.51, which is perfect. Instead of LVC it has an--at least as I've it set--a low voltage "slow down", so it will continually throttle itself until the 8.51 is held, so the prop will not completely stop, just keep slowing.

With 3X A123 and starting voltage of 10.14 this low voltage point was hit dead on 6 volts, so now the controller is set perfectly for A123 with these settings.
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