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Author Topic: A bit of help needed  (Read 4496 times)

waverunner

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A bit of help needed
« on: April 30, 2011, 08:07:19 AM »

Bear with me if I waffle a bit.

I was very happy with the Graupner Ti Amo I bought in February. Fast enough for what I wanted but I would have liked a little more run time. The shop had sold me a pair of 9.6v 3800Mah sticks together with the Planet 5 and ESC all of which they fitted before collecting the boat. I started a thread under the batteries section and it seemed 5000Mah were available, but the Overlanders I first looked at were a bit pricey so opted for the recommended Component Shop ones. Initially everything seemed ok ish but the more I used them (the boat gets used usually 2 or 3 times a week) the more I noticed they seemed unable to hold high discharge rates for very long and it became more noticeable the more I used them. In fact the performance dropped off noticeably after only a couple of minutes and to get back to something like full power I had to "rest" them for a while before going back on the throttle. Even then the performance dropped off really quickly. I put this down to cheap batteries and bought a pair of 9.6v 5000Mah from Overlander.

Newly delivered and fully charged off I went. Same problem. The boat went like the proverbial whatsit off a shovel for a couple of minutes then the power started to drop off. I persevered, resting the batteries periodically but still the power drop off was there. More interestingly towards the end of the run time when I applied small amounts of throttle to bring the boat back in, the engine would stop/start like someone was switching it off and on. This had also happened the last time I used the boat with the Component Shop batteries.

So, when new the boat would quite happily run at close to full power for most of the run time followed by a quick but manageable decline in power at the end, now power loss begins almost immediately you start to use it, and it's seems to be getting worse, and it doesn't seem to matter which batteries I use the problem is still there.

And so, where does the problem lie? Batteries - originally I thought yes but now I don't think so. Planet 5 - I don't think that has anything to do with the problem. That leaves the ESC and motor. I know nothing about ESCs and don't understand how they work (I'm still very much a novice when it comes to RC).

One small issue I have with Graupner is that the motor pre-fitted is a Speed 600. That's all they tell you. Nothing in the paperwork supplied with the boat tells you which variant it is. Even the motor itself carries absolutely no markings or labels whatsoever. What I did notice yesterday (and I hadn't checked previously) is that after the first outing, with all its stops and starts, the motor was seriously hot. Touching it was not a good idea. So was the shop wrong in supplying 9.6v batteries? Am I slowly cooking the motor and that's what's causing the problem? The only possible clue I have with this is that for the first time yesterday I noticed on Graupner's web site under accessories for the Ti Amo that they list 8.4v batteries. Would 9.6v do this over a long period of time with many runs?

Or, being the novice that I am, am I missing something else?

Any help or suggestions very much appreciated.

Jim


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JB

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Re: A bit of help needed
« Reply #1 on: April 30, 2011, 09:03:20 AM »

Ok, I'm something of a 'novice' myself, despite modelling in one form or another for the past 45 years...! all this electrikery can be confusing...

I'm guessing you are talking about Ni-Mi batteries? correct me if I'm wrong.

You don't mention what type of charger you have or your charging method...

I would be tempted to look at those first.

I'll have a think about it all...!

J.   
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waverunner

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Re: A bit of help needed
« Reply #2 on: April 30, 2011, 09:25:31 AM »

All the batteries are NiMH. The battery charger was sold to me by the model shop the boat and all the other bits came from. I can't remember which one and I'm at work now so will check and post later.

The batteries are always charged off the mains. Never leave the batteries on charge for more than a few minutes after the charger says charging is complete. Charge at 3.5A which can take 1hr 30mins or so depending on the capacity of the pack. The batteries are always charged after use and never left discharged for any length of time.

The shop gave no special instructions about charging other than plug 'em in, charge 'em, unplug 'em and the fact that I could charge at up to 6A and the batteries would take it quite happily.

Never occured to me that charging could be a possible issue.
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JB

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Re: A bit of help needed
« Reply #3 on: April 30, 2011, 09:44:19 AM »

I think we need to have a good look at your charger, did it come with any instructions? charging any type of battery is usually not just a case of 'plug it in and off you go'...best plan now is to wait until you are ready to supply more info...

catch ya later... 8)

J.
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waverunner

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Re: A bit of help needed
« Reply #4 on: April 30, 2011, 12:32:22 PM »

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nick_75au

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Re: A bit of help needed
« Reply #5 on: April 30, 2011, 12:46:18 PM »

If the motor is getting so hot you cant touch it then the load is to high, two ways to cure that without more drastic changes, either lower the voltage or reduce the size of the prop. It is possible that the motor has cooked, I have a Makita cordless drill that I cooked and it almost exibits the same problem with the high initial power but very short battery life ( and the occasional whisp of smoke :embarrassed: )

Some ESC's have a low voltage cut out, when the battery voltage drops below a certain point it will stop, if the load is too great for the batteries then it can "sag" the voltage enough to trigger the "LVC", pause then the voltage rises and off you go again until the cycle repeats.

To charge a fully discharged 5000 mAH battery it will at least 1.5 hours at 5 amps. If you charge after a run then use the batteries next time without topping them up may be some of the cause as well, Ni-mh exibit self discharge where over a period they gradualy loose charge, They are capable of being stored in a discharged state unlike Lead Acid so you might be better of charging before your trip to the lake not after.

Nick

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waverunner

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Re: A bit of help needed
« Reply #6 on: April 30, 2011, 02:10:59 PM »

Cheers Nick for your post. I've been doing a bit more digging. It seems you may have hit the nail on the head.

I've spoken with another Graupner dealer and he says the maximum you can put through the standard Ti Amo motor is 7.2v. He says 9.6v will certainly burn out the brushes which, as they can't be replaced, means essentially the motor is stuffed.

I'd ideally like to get another opinion on this before taking issue with the shop that supplied it who I'm not happy with anyway.

It's a real shame you can't deal with Graupner direct and that they insist you go via a dealer. There seems to be so few of these boats sold here that hardly anyone has detailed knowledge of them.
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JB

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Re: A bit of help needed
« Reply #7 on: April 30, 2011, 03:53:46 PM »

You have another PM Jim.
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Aeronut4

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Re: A bit of help needed
« Reply #8 on: April 30, 2011, 06:33:18 PM »

I tend to agree with the others about the motor, but I'm a bit puzzled about the battery you've got. 9.6V 5000mAh NiMH? I'd struggle to find one of that voltage AND capacity that was worth having.  Can you post a photo of it?
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JB

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Re: A bit of help needed
« Reply #9 on: April 30, 2011, 07:04:20 PM »

Here's a 9.6v 5000...

http://www.overlander.co.uk/batteries-chargers/premium-sport-5000-9-6v-overlander-ultimate-capacity.html

the charger should be ok, it will charge 9.6v (8 cells) if a little old fashioned with delta peak...I stand to be corrected on that last point..!

looks like you have cooked the motor, I've got some 'feeler's' out looking for a proper Speed 600...you never know..!

J.
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waverunner

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Re: A bit of help needed
« Reply #10 on: April 30, 2011, 09:14:38 PM »

Also

http://www.component-shop.co.uk/html/body_large_packs.html

Scroll down for the 9.6v packs. Can't comment on the quality of either as yet.
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AL 1

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Re: A bit of help needed
« Reply #11 on: April 30, 2011, 09:30:03 PM »

ive had quite a few 9.6 nimh component battery packs ana always found them very good
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JB

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Re: A bit of help needed
« Reply #12 on: April 30, 2011, 09:31:51 PM »

I can't comment on the component shop pack, not had any of those but they are ok I think, yes with the Overlander batteries, had a few different type's from them, so have other club (aircraft) members, no problems as far as I'm aware,  best thing about O/lander...they are just up the road..well about 20 miles...from my place, not sure if they'd let me in though..!!!
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over_powered84

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Re: A bit of help needed
« Reply #13 on: May 01, 2011, 03:28:20 AM »

my best advice being a novice as much as others here(5Yrs Experience %% ) is to get a charger that you can set to discharge and recharge, component shop batteries i'll swear by when used in conjunction with said type of charger, i have the graupner pollux running either one of it's 2x 7.2v 3700mah batteries or one of it's 2x 9.6v 3700mah... seriously never a problem, as i run them down during the day(When used), take them home, connect to charger and discharge at 1.5a and recharge at 1.5a, always pushes the mah over the 3700mah rating O0, typical wall plug in chargers i have a real pet hate for

Regards Jnr
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waverunner

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Re: A bit of help needed
« Reply #14 on: May 01, 2011, 08:22:09 AM »

In the light of conflicting information from Graupner dealers here in the UK, and being unable to email Graupner in Germany, I've emailed their UK service centre for advise on the use of 9.6v batteries with this model. Let's see what they say.
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nick_75au

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Re: A bit of help needed
« Reply #15 on: May 01, 2011, 08:46:12 AM »

As a matter of curiosity, what size prop is on her?

Nick
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waverunner

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Re: A bit of help needed
« Reply #16 on: May 01, 2011, 09:01:42 AM »

All I can tell you is it's a 3-bladed jobbie. (I'm at work and the boat's at home).

Graupner's web site doesn't give any more info either.

Edited to add that in the small print at the back of the operating instructions, under the heading of "you will need the following items not included in the set" it states the required battery as 8.4v. So maybe the 9.6v ones are just too much for it.
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waverunner

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Re: A bit of help needed
« Reply #17 on: June 05, 2011, 09:18:15 AM »

Just to bring this thread to an end, I finally managed to get the boat back to the shop. The problem lay with the motor. Seems Graupner now fit a different motor and it maxes out at 8.4V. Running with 9.6V over numerous runs was killing the brushes. New motor fitted and all ok...... until I picked up some reeds around the prop and sheared two blades off. Now waiting on delivery of replacements.

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