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>> Home > Forum > Electrical Related > Wiring query
Wiring query
(4001 views)
Author Message
HoweGY177
(Lieutenant)





Forum Posts: 43
3rd Oct 2015 10:35  
>> Permalink
mdlbt.com/19238

I am converting a 300mm long plastic kit for RC working, problem is that the battery has to be charged inside the boat and is inaccessible. Question is, if I connect the battery and speed controller in the normal way and then connect an extra L&N charging lead to the battery that I can make accessible for charging will I damage the 10 amp speed controller when using this lead to charge the battery. Obviously the balancing lead will be accessible.
Thanks for any input.

Dave M
(Fleet Admiral!)





Forum Posts: 1527
3rd Oct 2015 16:10  
>> Permalink
mdlbt.com/19244

Not generally a good idea to charge batteries in a boat, especially if you can't see them to check for any abnormalities or monitor the temp. If they should gas you may have the risk of an explosion.

Assuming your battery is connected directly to the ESC and you intend to run a lead from this connection for the ve and -ve then the ESC will be subject to the charging voltage from your charger which will be higher than the battery voltage and could be above the ESC max voltage. Also the ESC may be live and if it has a BEC so will any connected devices (Rx/Servo). Some ESCs have an on off switch so you can switch off the BEC but the power will still be fed to the ESC.

If you really wish to proceed I suggest you use an accessible plug to connect the battery to the ESC and swop this to your charger to isolate the ESC when charging.


Live long and prosper

Dave
HoweGY177
(Lieutenant)





Forum Posts: 43
3rd Oct 2015 18:34  
>> Permalink
mdlbt.com/19246

Thanks Dave,
With such a small craft, only 30mm wide, I have no option but to charge the battery in the boat but it will be charged in a metal box in case of a fire but I believe you have answered my question, the ESC may be damaged. I will have to look at the possibility of swapping the connections, another challenge!
Regards
Vic

nivapilot
(Petty Officer)





Forum Posts: 14
3rd Oct 2015 18:59  
>> Permalink
mdlbt.com/19247

double pole, double throw switch.
connect battery to centre pair of terminals, esc to one end and battery charging plug to the other side.

switch in centre is off....switch one way, powers the esc, switch the other way and only the battery is connected to the charger......esc is isolated.

nivapilot
(Petty Officer)





Forum Posts: 14
3rd Oct 2015 19:09  
>> Permalink
mdlbt.com/19248

DPDT switch connections.


Attached Files - Click To View Large

shavings
(Commander)





Forum Posts: 79
3rd Oct 2015 19:16  
>> Permalink
mdlbt.com/19249

You can buy a plug and socket where the socket has a built in switch which would disconnect the esc when the plug is in. Talk to the guys at Maplin who I am sure will help you
Roger

HoweGY177
(Lieutenant)





Forum Posts: 43
3rd Oct 2015 19:52  
>> Permalink
mdlbt.com/19250

HI Roger,
Sound brilliant but it would have to be a very small unit. I will contact Maplins asap.
Many thanks for you input,
Vic

Dave M
(Fleet Admiral!)





Forum Posts: 1527
3rd Oct 2015 21:34  
>> Permalink
mdlbt.com/19253

Make sure you tell Maplins how you are using the switch. Many small switches are low current devices and may not be suitable.


Live long and prosper

Dave
Haverlock
(Fleet Admiral!)





Forum Posts: 508
4th Oct 2015 12:11  
>> Permalink
mdlbt.com/19262

going with the dpdt switch makes most sense what current are you intending to run? You need to get a switch rated at the intended current x2 giving 100% over current capability as a minimum.

I know this seems excessive BUT some is good more is better. Your switch contacts themselves will act as a resistor and heat up.
To low a current rating on the switch will result in energy being wasted in the switch and ultimately a failure.


When not in use throw the switch to charging position that way the ESC is disconnected while not in use.


Attached Files - Click To View Large


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
HoweGY177
(Lieutenant)





Forum Posts: 43
4th Oct 2015 13:13  
>> Permalink
mdlbt.com/19263

The Speed Controller is 10 amp max, the very small motor pulls a shade over 3 amps.
I can see the benefit of a double pole switch but on this size model it may be impossible to fit one and still get access to it. I am having to open up part of the superstructure and the max opening I think I can get is 15mm x 25mm,

Haverlock
(Fleet Admiral!)





Forum Posts: 508
4th Oct 2015 13:55  
>> Permalink
mdlbt.com/19264

You will need to disconnect the battery from the ESC when the model is not in use.
This is because there is some current flow even when the ESC is switched off, and you would risk the long term life of the battery pack if it is allowed to fully discharge ( even if its not a LIPO ).

http://www.maplin.co.uk/p/dpdt-toggle-switch-fh39n

can you not find room for that?


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
HoweGY177
(Lieutenant)





Forum Posts: 43
4th Oct 2015 16:00  
>> Permalink
mdlbt.com/19268

Thanks for reminding me that there is a constant drain on the battery from the ESC, I had forgotten that point.

It is impossible to get the switch in, remember the boat is only 300mm long and 30mm wide and at the tallest point in the super structure from the hull bottom is only 35mm. The whole length of the keel from aft is taken up with, rudder, link and servo, then the speed controller that is mounted over the shaft, then the motor followed by the 2 cell lipo and finally the receiver leaving about 10mm at 'the sharp' end. Any switches and access for charging has to be somewhere in the superstructure of the boat. I think I am coming around to thinking of 4 x 2mm gold connectors, 2 to the battery and 2 to the ESC, links would connect the lives and neutral whilst the boat is in operation. The link will be removed and extension leads plugged in to the battery connections for charging. The balance lead would be fixed under another part of the superstructure that was made removable and an extension plugged into this for charging. I will add this to my fleet at a later date showing the construction.
Any other suggestions that would take up less room would be welcome but thank you everyone for your help, some very valid points have raised that I have included in the build.
Vic

Haverlock
(Fleet Admiral!)





Forum Posts: 508
4th Oct 2015 17:23  
>> Permalink
mdlbt.com/19273

go for the link its a viable solution. I don't like the idea of charging in situ BUT your in a metal box and are prepared for what may occur so I wish you luck and want to see some pics of the completed project on the water( even if you do need a macro lens )


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
HoweGY177
(Lieutenant)





Forum Posts: 43
4th Oct 2015 18:29  
>> Permalink
mdlbt.com/19279

HI Guys,
Added this model to the site, obviously work in progress but will update periodically.
Thanks again for all your help.
Vic

Dave M
(Fleet Admiral!)





Forum Posts: 1527
4th Oct 2015 20:48  
>> Permalink
mdlbt.com/19284

HI Vic
Seen your pics of the model and yes it is small. Is the superstructure all solid or is it hollow? If the latter you could cut it off the deck, add some coamings round the resultant hole and have more room for the installation.
If this is the case you may benefit from separate cells in line This could be achieved by using two Lion (Lithium Iron) batteries. Each cell gives 3.7v and you can get them up to 4000 MAh. They are protected so if you get them too hot they will restrict the current. I make my own packs and add balance leads to use with my charger set to Lion. The batteries are like big pencells but weigh very little. Commonly used in domestic applications they are more resilient than LiPo and less prone to accidents.
Dave


Attached Files - Click To View Large


Live long and prosper

Dave
Haverlock
(Fleet Admiral!)





Forum Posts: 508
5th Oct 2015 00:02  
>> Permalink
mdlbt.com/19288

I had a look and here is an idea mount 2 crosspieces inside the hull and glue on 2 magnets glue 2 more magnets under the deck.

You now have a removable deck and access to the internals.

Have a look here they do quite a range I have had dealings and they are quick to deliver.

http://www.first4magnets.com/


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
HoweGY177
(Lieutenant)





Forum Posts: 43
5th Oct 2015 08:38  
>> Permalink
mdlbt.com/19289

HI Guys,
The ideas keep flowing in and thanks, I do use magnets a lot and buy them in bulk from China. If you look at 'River Dance' in 'My Harbour' all the dolls are held in place by magnets, one behind the seats and the other stuck onto their backs under their clothing.
On this warship the higher part of the superstructure is already held in place by magnets possible allowing access to the lipo balance lead. Until the wiring route has been finalized I will not cut out any access holes as I feel the need to make it as waterproof as possible, hence I decided to glue the deck on with silicone, making it removable in emergency. No doubt this tiddler will be on a pond with slightly larger boats and if the deck was only held in by magnets any wash from other craft might enter the hull and blow the electrics. To the other point the superstructure is hollow and that is where I intend getting access to the required electrical connections. There are 2 possible access areas and until I assemble these individual assembles to see any restrictions I cannot be sure of the size. One access point may be sufficient.
As for batteries I have no experience of the Lion type and what is required in the way of charges. I use Lipos a lot and have only blown one up and that was inside the 'Minx' also in 'My Harbour', it has 2 x 850 motors in and when testing it for the first time only had 1 lipo fitted, I simply tried to take too much from it and it blew up! So again thanks for the suggestion but the lipos fits in snugly and gives just the right amount of ballast, just luck. Thanks again guys will keep you in the loop and will update pics, next week.
Vic

Haverlock
(Fleet Admiral!)





Forum Posts: 508
5th Oct 2015 08:57  
>> Permalink
mdlbt.com/19290

ok one last thought your running a motor drawing 2A this seems like a LOT of power for such a small boat. I am wondering if you had considered using a servo motor to power your model.
Get something like an old atcoms servo take it apart the electric motor will drive from its own amplifier since the feedback servo is no longer driven the motor will run in one direction or the other directly from a single control function I accept you would have only full power in each direction BUT with the correct prop your scale speed ( plus a bit) would be easy to obtain.


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
HoweGY177
(Lieutenant)





Forum Posts: 43
5th Oct 2015 10:07  
>> Permalink
mdlbt.com/19292

I took the amperage from an identical looking motor on eBay so may be a bit of incorrect info. When I get into the electronics side, as you may have gathered, I am 'at sea' so to speak. Own amplifier and feed back servo, not a clue I fear to say. I will have to stick to what I know. As for the correct size prop it is hand made and only 10mm, yes 10mm in diameter, I have had to glue it in place. There is no room for anything larger, I will show pics of this later. I think it is smaller than an old farthing coin, and that's giving my age away. lol. I believe proportional speed control is preferable especially when turning a craft that is very narrow for its length.

On another note I will probably change the balancing lead on the lipo male plug for a female that means I can glue it in place hidden under the superstructure. Doing this will mean The 4 x 2mm gold sockets and the female balancing socket will all be flush, again pics later as things progress.

Haverlock
(Fleet Admiral!)





Forum Posts: 508
5th Oct 2015 14:48  
>> Permalink
mdlbt.com/19294

It is possible I did a poor job of describing soooooo

http://www.mhsd.org/model/howto/servo.htm


have a look there it shows what I mean.

ohhhh I do remember the farthing showing a wren, yes I am that old!!!!!!
Q) Why do 3d coins have flats?
A) so a shopkeeper can use a spanner to screw them out of kids hands


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)