|
Post by ollieholmes on Oct 9, 2008 22:06:15 GMT 1
This is mainly aimed at Markus but i thought i would post it here as others may have a similar question to.
I already have some NI MH packs for my RC cars that are rated at 5100 milliamp from 7.2 volts, would they be suitable to use in the boat? This would make it allot easier for me as i already have a charger for these about 7 or 8 packs of these so it would save me money.
Also how easy would it be to wire up a Tamiya Style connector into the circuit? Ive never had to wire one in so i am new to it.
|
|
|
Post by markus on Oct 9, 2008 23:07:51 GMT 1
5100 mAh is good for at least half an hour running time, maybe slightly less when using special functions like turrets, smoke, ... 7,2 volts racing packs are suitable, giving the ship lots of power - so there's no need to go flat out a tamiya connector is already present on the esc's...
|
|
|
Post by ollieholmes on Oct 10, 2008 0:20:37 GMT 1
Thats good to know. I only use them in my biggest of models, tanks and a truck as they have alot of extra features. Standrd cars i run on 2000 mah packs.
|
|
|
Post by popeye on Aug 4, 2009 16:03:30 GMT 1
Help and advice please on the use of rechargable NiMH batteries.
I was going to use 2 lead acid batteries (I have arranged my circuitry with each motor - the central prop is a dummy - having its own controller and fed off its own battery, with a cross-connection switch if I need to run both off one battery). I was going to use either a 4.5, 7, 10 or 12Ah battery depending on the ballast weight after everything is fixed (e.g. servos, smoke generator, etc., etc.).
HOWEVER,
Maplins (our local UK electronic shop) are now selling an 11Ah NiMh 1.2v (D size torch) rechargeable battery, which can deliver up to 30 amps continuous. 5 of these (to give 6v) will weigh only 800 gm (probably 900 - 950 gm with the battery holders and waterproof plastic box to put them in), which compares with 1200, 1600 and 1700 gms for the 7, 10 and 12 Ah lead acid.
This seems a much better option. Does anyone know why I shouldn't go down this path or has any advice please?
Incidently, I intend to put the batteries in a battery holder, rather than solder them all together as a battery "pack". They click into the holder and can be easily removed to put them in a "standard" individual battery charger (Maplins do an 8-place charger that will handle high capacity NiMH). This also means that if one of the batteries has a problem, it can easily be replaced without having to unsolder/unwrap a battery "pack". The NiMH are also supposed to be good for at least 1000 charging cycles with a lifetime capacity loss of no more than about 20% (at least, that's what the manufacturers claim !!), which is better than the lead acid batteries.
|
|
|
Post by markus on Aug 4, 2009 17:52:56 GMT 1
using 2 lead batteries (one for each motor) is not a good idea - even 2 identical batteries have slight differences in voltage level and capacity
this will make it difficult to go straight ahead, especially if the BEC power supply is used on one of the esc's.
NiMh cells with 11000mAh which supply both motors at once are the better choice !
markus
|
|
|
Post by popeye on Aug 5, 2009 16:51:41 GMT 1
Dear Markus
Many thanks. I take it that you don't think there is a problem using the NiMH batteries.
I understand the problem of the different voltages (it also applies to the 2 motor controllers which, while of identical makes, have small differences in component tolerances that give slightly different motor speed when run from a single servo, as I found when I did an initial test run in the bath !!). However, the solution is fairly simple as the 2 controllers run off a v-tail servo, linking rudder position with individual motor speed control. All I had to do was to use the rudder trim control to offset the difference, which adjusted the relative speeds of the motors and the position of the rudders so that the boat ran straight with the rudder joystick in "neutral", when tested on the pond (after I had fibreglassed, painted and yacht-varnished the hull and with the deck covered with several layers of plastic clingwrap to waterproof and seal the top). I then adjusted the motor speed trim so that the engines were stopped with the speed joystick in neutral. Fortunately it didn't need too much adjustment and the boat controlled beautifully, especially in the pinpoint turns.
|
|
|
Post by popeye on Aug 5, 2009 17:02:16 GMT 1
PS
I join the voltage outputs from both the motor controller BEC supplies to feed the servos on a common power rail (the controllers have output protection on the BEC circuit so that any small voltage difference does not feed back into either other controller), in this way if one of the batteries/speed controllers fail, the servos remain powered from the remaining unit and I can bring the ship back on 1 motor. I am also using one of the new 2.4GHz radio control units, which has a twin receiver and therefore provides further redundancy.
This is what comes from being a nuclear safety engineer and submariner !!!!
|
|
|
Post by markus on Aug 5, 2009 18:57:52 GMT 1
a redundant system in a model ship - cool i have a special redundancy system - i can swim ;D ;D ;D markus
|
|
|
Post by popeye on Aug 10, 2009 23:06:12 GMT 1
I'm a submariner, we don't swim, although we can walk underwater !
|
|
|
Post by popeye on Aug 16, 2009 21:31:52 GMT 1
I have come up with an option for using the D-cell NiMH batteries. A company in America can supply 12Ah betteries at about £5 each. The holder is made using 40mm plastic waste pipe as follows: This is the completed battery holder for 5 D-cells to give 6v This shows all the parts for the end caps and at the top, the positive and spring-loaded negative caps. The M6 nuts and bolts are all brass to help conduct the electricity. The part in the middle, used for the negative battery contact, came from my local nut and bolt shop. It is made of brass and has an M6 internal thread and a large, flat end to provide good contact with the bottom of the battery. Instead of this, the my screw could be reversed and the hex head used for the contact, as is done for the positive end (although the head has to be machined or filed flat to provide a good contact) This shows on the left the normal end cap at the top and the lower cap has been internally machined to that the D-cell batteries will go through freely. You can also see the end caps fully made up. This shows the end caps for the battery. They are 32mm access caps (for accessing the drain pipe to remove blockages etc.) You can see at top right the piece of plastic glued in for re-inforcement and the copper tube that will be pushed in all thge way and "belled" at both ends to retain it in position. The matchstick is a standard one for size comparison as are the mini plastic clothes pegs. This shows the type of plastic waste tube used for the battery holder and the end caps with their electrical contacts. 3 of the plastic strips shown are glued inside the tube to stop the batteries from wobbling as their diameter is about 2 to 3 mm less than the inside diameter of the tube/ This shows the tubular battery holder, made from plastic waste pipe and fittings together with a morre standard option using Maplin D-cell battery holders in a plastic box. The matchstick is a standard one for size comparison as are the mini plastic clothes pegs.
|
|
|
Post by popeye on Nov 17, 2009 12:06:57 GMT 1
My 12 AH (12,000 mAH) NiMH D-cell batteries have arrived from the USA and I have loaded them up. This shows one of the 12 AH (12,000 mAH) Nickel Metal Hydride (NiMH) D-cell batteries. A standard D-cell Duracell battery is shown alongside for comparison. The following 2 photos show the 2 battery holders. One of them has been opened up, ready to have the batteries inserted. The leads at the front are to connect either a single battery holder (at 6v) to the charger or both battery holders in series (to give 12v). This shows the 2 battery holders, each with 5 NiMH 12 Ah batteries in them (6 volts each) being charged in series with the Ansmann ACS 410p autocharger. The autocharger can charge between 4 and 10 batteries (4.8 to 12 v) at 1200 mA and automatically senses the number of batteries and adjusts the charging voltage accordingly.
|
|
|
Post by Achtung!! on Nov 17, 2009 12:21:25 GMT 1
you should go into production - I ll buy one!
|
|