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    21

















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    SEA COMANDER RE-FURB.
    by Colin H πŸ‡¬πŸ‡§ ( Commodore)
    πŸ“£










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    271 Posts 270 Replies 125 Photos 597 Likes
    ( Newest Posts Shown First )
    SeamanCook
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    I didn't dare to say that. Has rank got privileges?

    It does bring certain advantages with it Petty OfficerπŸ˜‰
    😎
    SeamanCook
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    Going back to battery life....not having one myself I did a little web research.
    Salient facts
    1. Many folk don't know exactly what sort of battery they have. Don't assume that you have got it right. Check.
    2. Gel batteries are safest in confined environments and funny angles.
    3. You don't get any benefit for free, there is always a tradeoff.
    4. Gel batteries are the poorest battery technology for fast discharge. Eg a battery rated 7Ah discharged at 7A should last 1 hour? Wrong. Reckon on about 35 minutes at best.
    5. Gel batteries need careful and proper charging. If your charger is the wrong type or has a sensing or timer fault you will get reduced battery charge, faster sulphation etc all resulting in shorter run time, end result eventually a dead battery.
    6. As suggested earlier, if you have a constant voltage charger, 13.6V is the next best simple charger. That is a very slow charge technique; wait until the charge current has been stable and very low for 12 hours minimum, but then you can leave it trickling for a long time.
    7. If you want 7Ah equivalent performance to a gel battery you will get very near using a 12V 3 cell LiPo rated 4.4Ah. Do not trust any cell claiming more than 3Ah or so such as Chinese claiming 9900mAh . I can buy six Sony VCT4 cells 3x 2x2.2Ah =13.2V 4.4Ah for 18 pounds, but doubtless one can buy a battery pack. At 7A Lithium will be very happy. The Fleet Admiral would correctly insist on a 15A or less fuse. Due to the superior discharge characteristics the Lithium will give rather better performance overall, finishing at 9.3V or so. Gel ratings reckon on full discharge at 9.2, but voltage dips sensed by an ESC may trip you out earlier. Its the end point that really matters in giving those last few minutes.
    2
    RNinMunich
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    I reckon that's it's a pound to a pinch of proverbial that's it's a reversing relay Jonathan.
    But then, you knew that all along didn't youπŸ™„ you naughty boyπŸ˜‰
    Cheers, Doug 😎
    1
    Young at heart πŸ˜‰ Slightly older in other places.;-/ Cheers Doug
    SeamanCook
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    Without knowing the ESC number I can't answer that!
    But there are 2 major possibilities.
    1. A crossover reversing switch. That eliminates 3 out of 4 switching elements and can reduce losses. Relay would be rated near or above ESC rating. If above 20A it would be big. Can incorporate a resistor so as to allow less power in reverse.
    2. A device to ensure all is well before enabling the Switching devices to start up.
    Could be in the main power line and double up as an On switch. Again, fairly big, but smaller than in first option because it only needs one contact.
    Other possibilities exist but need a mind more perverted than mine...
    1
    G6SWJ
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    SC,

    What does the relay do in my ESC?

    Regards
    Jonathan
    I think it's the way I have learnt most of my stuff - getting very stuck first...
    SeamanCook
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    Gentlemen, you illustrate exactly why I built my own first ESC (ignorance and mistrust of purchased products,) and partly why I then continued with my Tug dual ESC blog. Advert over...but in a few blogs time I will be covering H bridges, which are present in every ESC and may, I repeat may, be a real source of some of your problems.
    With no disrespect intended, you don't really know what, if anything, is wrong.
    I can say that battery specifications and tests can be horribly misleading. In particular, battery voltage cannot be interpreted with a DVM. In my testing I have seen battery voltage, on NiMh at 7.2V nominal, dip and recover by over 500mV in a single 3msecond cycle while drawing only 3A. That is more than enough to trigger under voltage trips rather earlier than expected, and I'm sure that other technologies or poorer state of charge would give even worse figures. Figures given by marketing men are totally worthless, and I understand that Chinese batteries can be only 10β„… of what is promised.
    Going back to H bridges, several aspects of the design are critical. In particular, if the design allows even momentary "shoot through" - google that- you will get poor runtime at best and early under voltage tripping as a certainty. Higher voltages make that a higher possibility, again depending on any short cuts in the design. The ESC numbers you mention only seem to have options for up to 9 cells, which means absolute max running at start of around 12.6V and rapidly decaying on a few seconds to 12.2 and below.?? But your 12V batteries will start at 14.4 and should not be run below 8V, so a 5V drop out is extremely low, the battery is over discharged by then. If you could select the 9 cell option, and if I was designing the ESC I'd be putting dropout at around 7.5V and hope for recovery to 9V to allow a limp home mode.
    What is there to do?
    Testing battery discharge time at a load nearly equal to the motor load is a first step only. A stack of light bulbs is easy and convenient, although a purist will argue. That will confirm that the battery is basically good or bad. You just time how long it takes for volts to drop below 1.1V/cell NiMhl (1.5 for lead acid, 3.3V for lithium) but do NOT flatten the battery much more than this or you may wreck it, especially lithiums.
    5 mins after you start this test, take the light off measure the battery volts, put the light back and see how much the battery drops. That is a crude measure of battery internal impedance. You can repeat that test at any time during the discharge cycle. High battery impedance will always result in problems. For NiCd and NiMh battery holders with springs are an absolute no go because they will double the battery impedance. Strong clips may be OK for a small motor. So connections are critical. Soldering some materials needs care because you may get a poor joint even if mechanically it seems strong. Gold plating is a well known culprit. It starts OK and vibrates off.
    The gold standard is the oscilloscope. You just set the boat going and look at the power supply. (Light motor loads can be misleading so pushing against the side of a tank is best)
    All is revealed by this test, if you know how to interpret what you see.
    In time, I'll be putting some pictures on my blog when I cover H bridges, and how to sleep at night.
    Colin H
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    Hi Peter and Chris, comparative times can be awkward to get right unless the setups are the same. As you know my refurbished commander has a taycol Supermarine. And a water-cooled New Rain 320 amp esc. And the 12v 7ah battery. Time running still unknown, I have done a wet bench test in a baby bath on 3/4 throttle and left running till in stopped, 72 minutes. Checked the battery voltage, dropped to 5.2 volts.
    My other commander at present has an unknown motor, esc, but running on 6v sla ah? As its very old I charged for 72hrs on trickle and did the same tests, it ran for 28 minutes and the battery had dropped to 4.6v.
    I hope to reconfigure it to use a 12v 7ah in the near future as I have plenty of them and they are cheap enough to replace.
    Cheers Colin.
    2
    Fair winds and calm waters, COLIN.
    peterd
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    That is all very interesting.
    My setup:
    700 motor brushed
    Battery:12v 4.5 aH Gel. (Brand new and only used the once)
    ESC Brushed Hobbywing WP1060 RTR - same as yours.

    At the end of the day it appears our setups are quite similar - you might be right and the battery needs some use. Would be very happy to get that sort of time.

    Hoping to get onto the water tomorrow, however the weather at the moment may say otherwise. Rain plus I believe that we are getting some of the arctic blast so it might be a good day in front of the heater - not my ideal.

    I will put something more positive up hopefully.
    1
    ChrisB
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    Hi Peter,
    Had a couple of further thoughts post my own battery woes previously. ESC setting? Battery conditioning?
    Long story below - apologies!
    Using my Huntsman as an example, 1/16 scale and very light weight - but she would stop only after 10-12 minutes run time. Its is a brushed set up, then using a Hobby-wing(?) WP1040 ESC and at the time a 12 turn 540 motor and 7.2 v NiMh batteries - nothing overly complex which suits my electronic IQ!
    My first thought was too high speed motor drawing way to much juice - which I scaled back to a 35turn but still had short runs but scale speed at least.
    I would run my multimeter across the battery post returning to shore and it would show a surface charge of >6.2v....I was a little confused. I tried several of my batteries and similar results...so I did a boat bench test to check the voltage and amp draw - amps were good around 1.1 - 1.3amp full noise, voltage as required by the ESC depending on throttle position. However, as the battery declined and it approached 6v - it was goodnight. No go.
    Turns out the ESC I had purchased - RTR kind - had a fault or incorrect set point for the low voltage protection. Being RTR it wasn't adjustable. It was meant to be a 5v trip, recoverable down to 4.5v by letting the throttle return to neutral. But I was a dead duck each time.
    I procured the same brand but a WP1060 RTR - same trip specs - recommended by the hobby shop here and now I use these on all my boats - never missed a beat (so far) and run times are 40+ mins or longer depending on pauses and idle time. Voltage runs down to 5v as intended - solved for my case.
    I also tend to deliberately run for only for 15 minutes or so, then rest the boat which allows the battery to recover, motor to cool etc - but if its a family day with my nieces driving my boats around then its run till they nearly stop but they each get good run times regardless.
    With the battery - and I'm not sure of your set up - but I run on NiMh and all get some warmth post running. Do you notice any battery heat?
    I have had a new but "problematic" battery which took several days of bench running on a test motor, recharging once cool, and repeating the cycle to condition it (if that's the right word). Might be helpful if you suspect a battery issue to give this a try?
    My limited experience is the more consistently they get used the better and longer they perform (I have had a 7.2v 1700mah NiMh for over 20 years now - still as strong as ever).
    Sorry for the long story - hope my past woes might help you (if you haven't already ruled these out that is). Good luck.
    Cheers,
    Chris
    PS - not recommending any brands - just sharing what has worked for me.
    2
    peterd
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    Never too late Chris. I am a newbie to powered boats so I did get heavy on the throttle as well. That is more the time I would expect and hope that it was simply a combination of things that gave me a short time on the water. I actually took the boat out for 20 minutes to allow me to come last in a sailing race and then put it back in and it had regained another 5 minutes.

    Better luck Sunday. (ps, wondering about the logistics of putting the motor into my Wee Nip. Cannot take a trick with it lately.)
    1
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