4S goes into half speed in 3 laps, while 3S runs for over 40 laps?

[1945dave]

Okay Dana, I have no problem with you, so lets clarify what you are telling us that we don't listen about. Are you saying that I should reduced the load on the prop and still run the boat to see how this affects my lvc? Or put another way are you thinking if I reduce the prop size that I might not have this issue?

Dave

[dana]

I recommend raising the strut up 1/8 increments. Where is your strut now? At or below sponsons? Basically yes, reducing load will reduce likelyhood that the lvc kicks in

[1945dave]

Let me jump up and tell you that I already have the strut higher than most. I can set my boat (virtually all of my cats, nitro, gas and electric) on a table and the strut very bottom will just kiss the table. The center line of the prop shaft is above that by the radius. I also almost without exception have the line of thrust dead level with that table also. So I have no problem raising the strut even higher but for my purposes to test your theory I might drop down in prop size. While I am sure that will result in a lowering of my speed I might learn something about the lvc circuit on my esc. Your point is well taken and understiood, thanks for your input.

Dave

[dana]

You're welcome. I went thru this with my mean machine, and without changing the lvc, I raised the strut and problem went away. I hate the idea of no lvc. I have 4 seaking escs all with lvc on. Setup is everything. It's worth trying. IMO, you can never have the prop too high, unless it doesn't hook up and just cavitates. Most likely, you would be able to raise the strut up more than you think before the prop just cavitates.

[dana]

Btw, I Agree there is an lvc issue. I set mine to 3.0

[1945dave]

dana, I fully appreciate the rasing the strut until cavitation is unmanagable and I agree adjusting the strut depth has to go hand in hand with prop selction. meaning for one prop the strut can not be raised anymore but for another larger prop perhaps you can. I know I am close with my choice of prop and yes I have experimented with higher strut depth but lowered the depth just a hair (1/16th?) to lift the bow a bit and also allow for a more dependable acceleration or punch when I ask for it. All things said the issue is I need to know what is the actual voltage reading for cutoff. I will invest in an Eagletree or such very soon. I think the tell tale indication that my lvc cuts in too soon is that it only takes 1500 ma to get back to full capacity. What recharge capacity would you think a 4,000 ma setup would be reasonbable? I have heard guys say never use more than 80 percent of your capacity meaning that it would take about 3200 ma to bring back to full charge. The confusion on my part is that this is for my 4S setup while my 3S setup with the same prop and esc has no issues giving me about 86 per cent usuable capacity without excessive heat anywhere. Do you see my confusion?

Dave

[drwayne]

Okay, my programming card will allow me to turn off the lvc but then how will I know how much time I can run before risking damage to the batteries? I don't mean how can I do the timing just how much time do I allow for?

Hi
Dont turn off the LVC .. set it manually to the cell count applied.

Have you tried an alternate set of 2S packs?
Despite their label ratings.. the packs may be ducbious from manufacture (?)
W

[martin]

On some off these Seaking & turnigy esc you can set with auto, manually, 2.8v,3v, 3.2v,3.4v lvc, run higher c cells etc & the lvc still cuts in to soon. I have a Seaking 120a that is permantly on lvc from the start, this is why their are so many with these esc use no lvc. This included some pretty experienced racers on this forum.

[drwayne]

On some off these Seaking & turnigy esc you can set with auto, manually, 2.8v,3v, 3.2v,3.4v lvc, run higher c cells etc & the lvc still cuts in to soon. I have a Seaking 120a that is permantly on lvc from the start, this is why their are so many with these esc use no lvc. This included some pretty experienced racers on this forum.

Hello Martin.
Yes, there are low voltage issues here.
But on 3S lvc works a treat, Id not eliminate other issues too soon.

Has the OP checked disconnect voltage the 2x2S Turnigy 35-70C4000 packs ?
The 1500mAh recharge does not identify voltage drop under load.
Are one/more of these cells 'sad' ?
Without that knowledge it is incorrect to declare the lvc faulty, when that feature works well on 3S.

His first run on 4S with 2x2S turnigy packs ....... and problems started in an otherwise sound setup for 3S.
He also stated that the esc detected the 4 cells by autocount beeps on connect...

Please check the batts ( or try an alternate set of 2x2S and report back )

Wayne

[1945dave]

Thanks Wayne,

A very determined and well thought out responce. Yes I am in the process of getting another set of 4S batteries and that should help us narrow down what is happening. I am not sure what this would tell you but to isolate one bad cell how about if I run the boat on 2S to compare each 2S pack individually. I would not expect much performance but I would think if there is a battery problem with these new packs it would have to be only one of the 2S packs not both wouldn't you think? I also agree the recharging capacity does not tell you what dropdown voltage under load is being detected. Yet, I balance charge each 2S pack individually and they are identical in this regard. By the way just to rule out a charger issue I had my brother use his very expensive charger and the results are the same. My favorite charger is a Imax B6AC and all the voltages and settings have been verified with a Fluke 77A digital multimeter. I have not discharged these batteries using the 1 amp discharge rate on my charger to determine capacity but a low drain may not reveal the problem, do you think?

Anyway, thanks for your input.

Dave

[drwayne]

Hello 1945dave

Determined ?.. Sure... SOP at my desk.
One needs to satisfactorily examine each possibility before focusing on the likely culprit.
A process of elimination leads you to the bastard at fault !
If a mechanical fault, it could be right up your alley !
My alley is named 'Electronics'.

I enjoyed my iMax B6 DC charger.. I sold it on for the B610 unit which has equal appreciation.

Cheats way to check battery condition.
Do this outside !
2S = 8.4V ..
Grab 2 automotive headlamp globes of 12V 70-100W and wire in series.
That equates around 16-24A on a single 2S35C4000 (continuous draw available 140A )
connect to battery and light up the room for 30 seconds.
Disconnect and then immediately measure cell voltages.

In one your posts you made mention the plugs/wires used on/between the packs may be an issue... have you access to a camera for showing us this handiwork ?

regs
W

[1945dave]

DSC_0206.jpgDSC_0207.jpgDSC_0208.jpgSure Wayne, I will snap a few high quality shots of my handiwork but in truth I use 10 gage wire and solder really well. My series harness is much longer per leg than needed but my concern is really about those stupid red dual 4mm barrel connectors typical on Hobby King batteries. I am changing everything over to 5.5 bullet connectors soon but have not yet.

You will see my home made harness is about the same size as the castle XT60 harness. I know you can not see the actual solder connections inside those red insulators but trust me there are no cold joints and I fill up the cavity in the barrrel connectors with good quality electronic approved solder.

Dave

[drwayne]

True, the 4mm plugs are poor quality

That red wire looks like auto power cable !
tsk tsk if so... higher resistance than the denser core of high current cables ...
W

ps 01:30hrs here, time for shut eye.

[1945dave]

Interesting observation. The red wire is 10 gage silicon power cable very soft and pliable but the individual strands are heavier and therefore fewer than some high current leads I have seen. Yet, I like my cable better than the more expensive castle premade. I just got some 8 gage wire and will make a new as small as I can series adapter just to see what happens.

[drwayne]

I think you have answered your own question.
This style 10awg has fewer& larger strands than the HIGH CURRENT cables. ...... Which have lower tesistance and higher cable density by cross section.

Nite !
W