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[Mark47]

I seem to be stumped at the moment as to what's going on.

I have a Trent by model slipway.

Motors are 2x Graupner 600 Eco

Specs

Nominal voltage 7.2V, Operating voltage range 6-9.6 V
No-load rpm 11000,
Current drain at max. efficiency 7,5 A
Shaft diameter 3.17mm, Weight 220g

I have these running through. 2x Viper marine 25s

Specs


The Marine25 has a 25Amp motor limit and has proportional forwards and reverse functions

6-12 Volts input voltage
100% waterproof design
BEC Disconected as using a seperate RX power supply. I have done this so if one battery runs done powering motor and RX. I still have power to return to shore.
Dimensions : L39.0mm x W34.0mm x H13.0mm, Weight : 55g

Batteries are 2x 9.6v 3700mAh by Vaspex (think that's the name). I bought these instead of cheap Asian knock offs. Just to be sure I had a good product.

Specs


 9.6V 3700mAh SC NiMH Battery Pack
 
 
   
 
 Capacity:
 3,700mAh
 Measured at 740mA (0.2C)
 
Weight:
 544g
 
 
Max Discharge Current:
 30,000mA
 (30 Amps!)
 
Max Charge Current:
 3,500mA
 
 
Internal Resistance:
 <31 mOhms
 At full charge (<4 mOhms per cell)
 
 
 These are charged by this charger. Purchased from the component shop along with batteries.

 500/1,000mA Smart charger for race packs.

Charges 2, 4, 5, 6, 7, 8, 10 cell NiCd or NiMH battery
packs. (2.4V, 4.8V, 6.0V, 7.2V, 8.4V, 9.6V, 12V)
Delta-Peak microprocessor controlled charging,
switches to trickle charge once pack is charged.
Discharge function for NiCd battery packs.
500mA or 1,000mA selectable charging current
Mains 230V UK 3-pin plug (Batteries sold seperately)

I charged the batteries on 8 cells at 1000mAh. The batteries were charged in around half an hour.

I connected everything up to set the ESC's this morning. After only 2-3 minutes the motors died.

Does anyone have a clue as to the reason why? ESC's still recieving signal.

Just for more info. I can flick the shafts in my fingers and the will rotate no problem at all. (basicly I don't have anything causing friction).



Thanks,

Mark 
 
 

[Tug-Kenny RIP]

Wow, what a concise load of figures.

Basically you've run out of Amps when running the two motors.

I should imagine you are going to need bigger amp/hr batteries.

Hope this helps

Ken
 

[Mark47]

Wow, what a concise load of figures.

Basically you've run out of Amps when running the two motors.

I should imagine you are going to need bigger amp/hr batteries.

Hope this helps

Ken
 

Hi Kenny,

3700mAh????? Does this not equate to 3.7aph? If it does, I should be getting at least 30 minutes approximately. As told and reccomended by Westbourne Models.

[Mark47]

Wow, what a concise load of figures.

Basically you've run out of Amps when running the two motors.

I should imagine you are going to need bigger amp/hr batteries.

Hope this helps

Ken
 

If you don't have figures an specs. How can you diagnose a fault? I may have went overboard a little ( )

[DickyD]

Are you sure the signal is getting to the escapes and that your Rx batteries are fully charged ?

Did the motors slow down and stop or just stop ?

Did they both stop at exactly the same time ?

[dodgy geezer]

Are you sure the signal is getting to the escapes and that your Rx batteries are fully charged ?

Did the motors slow down and stop or just stop ?

Did they both stop at exactly the same time ?

Echoing DickyD's thoughts - can we confirm that the batteries are run down? If it takes 30min to charge, and 2-3min to run down, it should be simple to charge, do a test run in the bath and confirm that the batteries are flat afterwards. Alternatively, charge, then set the batteries to running a light at known amps. You should be able to confirm hoiw much power you can get out of the batteries.

Assuming you confirm that the batteries are not providing anything like 3.7 Ah, then it's either dodgy batteries or a dodgy charger...

[Shipmate60]

Yes the batteries should have lasted longer than that.
Are you sure that the batteries were fully charged as the charger will discharge packs.
I only ask as when I got my new charger the first thing I set it to was cycle and when trying to test my model exactly the same thing happened.
Yes I should know better and DID check the voltage before testing!!!!
But the batteries had been discharged and "recovered" slightly to get a few minutes running.
Bob

[Mark47]

Both race pack were sitting at 9.98 and 10.01 volts before use. The Rx battery is sitting at 5.82 volts.

Charger only sat at discharge for around 1-2 minutes before charging.

Mark

[DickyD]

I'll ask again, Did the motors slow down and stop or just stop ?

Did they both stop at exactly the same time ?

[dodgy geezer]

Both race pack were sitting at 9.98 and 10.01 volts before use.

Did you check the main battery voltages under load? Even a pretty flat battery will still show a high voltage across its terminals if it's not on load.

Perhaps some electronics wizard can correct me, but I have never found that the off-load terminal voltage was a very good indicator of capacity. Seeing how the voltage varies in the first few minutes under load gives a much better idea of how the battery is behaving...

[malcolmfrary]

A 3700mAH battery charged at 1000mA for 0.5 Hours = a one sixth charged battery.
If its a new battery, it might need to go through a few charge/recharge cycles before it reaches full performance.

[Mark47]

A 3700mAH battery charged at 1000mA for 0.5 Hours = a one sixth charged battery.
If its a new battery, it might need to go through a few charge/recharge cycles before it reaches full performance.

Only going by the charger, when indicator said full.

[dodgy geezer]

Only going by the charger, when indicator said full.

So your problem could conceivably be a dodgy charger? Are you able to charge another battery on it effectively?

[DickyD]

ONCE MORE. I'll ask again, Did the motors slow down and stop or just stop ?

Did they both stop at exactly the same time ?

[stallspeed]

The receiver pack voltage is suspiciously high if it is a four cell type.The main pack voltage readings indicate the batteries are flat,regardless of that.

I recommend you do a full charge and measure your full out motor current drain.Don't be surprised if it is 30 amp.

[Mark47]

ONCE MORE. I'll ask again, Did the motors slow down and stop or just stop ?

Did they both stop at exactly the same time ?

No need to shout Dicky, trying to entertain the three year old and get boat running in between reading forum.

Both motors dying around the same time. Pretty much dying. If I put the power of and on again I get a small burst of power for a few seconds to a minute.

[FullLeatherJacket]

I agree that it sounds like flat batteries. If I were you then I'd contact Iain at Component Shop to see if you are reading this charger's indicators correctly. I have a couple of similar chargers and it's never clear which LED is fully ON at any one time.

For what it's worth, I still retain the old Multilader mains charger and use that for all NiMH and NiCAD packs - unless I desperately need a fast pond-side charge. Flatten the packs down to 1v per cell and then charge at C/10 for 14-16 hours. If your charger won't achieve C/10 then pro-rata the charge time to the available current - it's not that hard to do the arithmetic. With a brand new pack I'll extend the initial charge time to 24 hours. At C/10 you're not going to do any lasting harm.

Churlish though it would be to appear to disagree with Mr Speed, but if the reading is 30A then you can be VERY surprised! I also have found that a fully-charged 4-cell pack can often exceed 6 volts.

FLJ

[Faraday's Cage]

Mark,

Occasionally my delta - peak charger will indicate a full charge on my racing packs when I know that can't possibly be true.

Try recharging the packs twice or three times before using if you only get a short charge time.  The charger will protect the cells from overcharging.  Your 3700mah packs if charged at 1000mah will need around 4 hrs  to charge from discharged state to be charged properly.  The packs should be feel warm when fully charged at that level of charge.

Cycling the cells (Charge/ discharge several times) will also help.

Also a slower charge rate will help and prolong the life of the packs.
FC

[DickyD]

Hi I have one of those chargers, have always found mine pretty foolproof.

As FC says, when your batteries are charged they should feel warm, if not keep pushing the button to get the charger back onto fast charge.

The charger will normally start on trickle charge and after a while go onto fast charge so dont be fooled by the trickle charge LED when starting a charge.

[regiment]

i took my 47 inch fire boat wt 23 lb plu s up to the lake 12v 12 amp battery 800 motor 1 1/2 3 blade prop montronics 15 amp  2 HOURS  later i gave up and came home  freezing cold i do not know any thing about motors etc but must be doing something right  for long run time  regiment

[Mark47]

Thanks for all the input.

The RX batteries are four Duracell Ultras. The flat pack I have had for years just aint holding a charge.

I have returned to the hobby after 15 or so years away and my only experience previously with batteries was with SLA.

Race packs are all new to me.  This is the second charge I've given them since new (January 09). I'll try run them down and re-charge.

Dodgy Geezer,

Unfortunatly I do not have any other race packs to try in the charger.