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[Roadrunner]

Over the past few days i have had 2 different people PM me asking how to charge a battery while its still in a boat, the main reason for asking such a question is such that some model are very highly detailed and continual removal of the super structure or parts of it for access to the battery compartment risk damaging the model.

Normally i wouldn't suggest charging a battery inside a model for the simple reason should something go wrong it could result in the loss of the model or worse...

But i have known people to do this, and although i normally don't attempt this i will be during the Komet build have to do a battery charge setup inside the boat for its owner.

I have drawn up a wiring diagram to explain the 'simplest' version of charing a battery in the boat to explain the process.

Well the diagram is idiot proof so I'll let it explain itself.

If you have have other methods that wll do the same job this would be the place to post or discuss it.

RR

[Tutssy]

Hi RR

Glad you did that.  I have been thinking of how to do that for a while now.

Just a thought though.  Is it not advisable to fit an isolator switch between the battery and the rest of the electronics, so that power is going to the battery only?



Regards.  Al

[class37]

would it be worth while fitting a d/p-d/t centre off switch into the circuit.

this would have the two centre contacts wired to the battery +ve and -ve, the two contacts on one side connected to the charging sockets +ve and -ve and the two on the other side to the ESC, that way you would not have the battery connected to the ESC while charging.

would give you a CHARGE - POWER OFF - POWER ON selection on the one switch.

would this allow you to dispense with the on/off switch for the ESC ?

just an idiots idea.

[Roadrunner]

Glad you asked that.. if using a traditional esc with a built in on/off switch then providing that the switch is in the 'off' position then you should have no issues with power being distributed through out the system, but you are right fitting an isolator in place between the power to the esc would be advisable if you are not using a traditional esc with the on/off switch function, although rare in many LA battery setups, which this diagram is intended for.

[Tutssy]

Thanks for the prompt reply & for the information in general.

I think that I would put one in anyway, just for peace of mind.  Dead cautious me.


Al

[Roadrunner]

would it be worth while fitting a d/p-d/t centre off switch into the circuit.

this would have the two centre contacts wired to the battery +ve and -ve, the two contacts on one side connected to the charging sockets +ve and -ve and the two on the other side to the ESC, that way you would not have the battery connected to the ESC while charging.

would give you a CHARGE - POWER OFF - POWER ON selection on the one switch.

would this allow you to dispense with the on/off switch for the ESC ?

just an idiots idea.

Yup you can do that to the switch if desired, nothing wrong with that suggestion. Only reason i have not added that to the diagram as many buy new ESC's for each model this setup does not void your warranty on the esc by altering the switch (mtronics in general)

[Tutssy]

Hi Class37

I like that idea, it's just the job.

For some reason I couldn't think of something that simple.

Glad someone is paying attention.

Al

[class37]

many thanks, Tutssy,

and of course, don't forget the fuses !

got to get back to the asylum

cheers

alan

[class37]

Yup you can do that to the switch if desired, nothing wrong with that suggestion. Only reason i have not added that to the diagram as many buy new ESC's for each model this setup does not void your warranty on the esc by altering the switch (mtronics in general)

I must admit I would probably leave the ESC switch still connected and permenantly left switched on for that reason, although it can then be lft by the ESC, and you just end up with the d/p-d/t-c/o and two charging sockets to mount somewhere, and aren't constricted by the length of ESC switch wiring.

cheers

alan

[PMK]

Contrary to popular belief, some ESCs will still draw a small amount of current from the main battery even when the switch is off. It is therefore always safest to totally isolate the battery from the ESC and other circuits while the battery is being charged. This same/similar topic has already been covered in this thread: http://www.modelboatmayhem.co.uk/forum/index.php?topic=28505.0 , along with a couple of sketches showing how to connect a DPDT switch.

[ACTion]

This for twin batteries. http://www.action-electronics.co.uk/pdfs/On-Board%20Charging.pdf
For a single battery, just omit the second one and the P103. Switches are SPDT type. Charging connection(s) can be either jack plug/socket or 2.5mm DC power plug/socket.
The small switch on an MTroniks ESC doesn't cut the power to the speed controller itself; it simply switches the power from the BEC regulator to the receiver, thereby acting as a radio on/off switch.
DM

[Roadrunner]

The small switch on an MTroniks ESC doesn't cut the power to the speed controller itself; it simply switches the power from the BEC regulator to the receiver, thereby acting as a radio on/off switch.
DM

I have to disagree that its not the case with the newer mtronic esc's,(plug and play) when the switch is in the on position the red/green leds flash on the led will go green for signal from the tx and red when there is no signal acting as the Failsafe, (then red or green pending on tx throttle position) where the switch is in the off position the esc shuts down as no led's are on meaning no power is being drawn at all. If the esc was still drawing power surly that could be pretty dangerous if in the off position! im sure there are a few rules and regulations that must ensure that when the switch is in the off position no power is being transferred into esc...

[PMK]

But you have to remember that the on-board voltage regulator (the BEC) in the ESC unit will be constantly drawing currrent from the main battery - regardless of the position of the switch. The only way to totally isolate the ESC (and therefore the BEC regulator) would be to put a switch in series with the red wire going to the battery, and that the switch itself is capable of handling the required current draw of the ESC. The supplied slide switch on the Mtronic ESC is just a puny affair, capable of carrying, say, just 1 Amp or so of current, and the two wires going to the slide switch are also too puny to handle any major currents. It is only there, as ACTion has already stated, to disable to lower voltage/lower current feeding the receiver... or, as you said, to operate other lower voltage circuitry inside the ESC. It does NOT turn of the ESC completely.
As Tutssy and Class 37 have already tried telling you, your sketch at the top of the page really does need a hefty isolator switch between the ESC and the battery.

[ACTion]

I was passed that information by Steve, one of the service engineers at MTroniks - and a nice bloke, too - when one of our customers encountered a problem which turned out to be related to that little switch. Everything PMK has said is correct, but if you want to leave your MTroniks ESC connected to the big battery without an isolator switch then suit yourself (as someone used to say).
I wouldn't.
DM

[unbuiltnautilus]

I have a home made continuity tester which I use to test our 'bangs and flashes' with at the pondside. It consists of a 9v battery and a buzzer in a box. I fitted a DPST switch that breaks both the positive and negative lines between the battery and the buzzer and test leads. This has had the same 9v battery in it for about SEVEN years, and still works at the start of each season . I always worry that some power will 'leach' out of the battery if it is connected in any way to the circuit. My brain tells me this is nonsense, however, I rarely listen to my brain 

[Tutssy]

  Trying not to appear thick here, but where, on the diagram so kindly provided by RR, would one install the fuses as mentioned by Alan (class37)?

Electrics does my head in

Regards  Al

[PMK]

If your SLA charger unit does not already have an in-built fuse, then I'd recommend sticking one between the charging socket and battery positive terminal. Since the SLA is best charged at a small trickle rate, the fuse need be no larger than, say, 1 or 2 Amps.
More importantly, you'll need a fuse of the appropriate current rating between the battery and the input of the ESC (also on the positive rail). If, for instance, your ESC is rated at 25 Amps, then the rule of thumb is to usually use a fuse rated at 30 Amps. And for a real belt-and-braces job, you might want to stick a fuse of the same current rating between the output of the ESC and the motor actual (again on the positive rail).

[Tutssy]

Thanks PMK

I think I have it now.

Regards  Al

[PMK]

...where the switch is in the off position the esc shuts down as no led's are on meaning no power is being drawn at all.

Not so. It doesn't quite work like that. The little switch is internally connected to the output - not the input - of the the on-board 5-volt regulator (the BEC). It simply turns on/off the 5-volt supply to your Rx. The on-board regulator is also used to supply the appropriate 5-volts to the microprocessor inside the ESC because 5 volts is usually the maximum voltage that most all microprocessors can handle. Now if that little switch were connected to the input side of the voltage regulator it means that it would have to handle the full operating current of the ESC itself. And since the two wires going to the little switch is rather thin, it means they would burn to a crisp in no time at all.
Just to prove the point, try connecting an ammeter in series between the battery and the input of the esc (as I've shown in your sketch). Just because no LEDs are on does not mean that the ESC has shut down. You will notice a reading on the meter without doubt - even when that little switch is turned to its OFF position because the BEC regulator is still sapping a small amount of current from the main battery. This is the reason why you should only charge the battery while it's totally isolated from the ESC.
Put it this way, you wouldn't charge the battery on your car while the headlights are on, would you?

[Steve1961]

Hi just been reading your posts have been thinking of something similar for my Atlantis, I have a Viper15 esc should there be a fuse fitted?

[treeboa]

all the boats i have have mtronics esc`s in them, one, a bait boat has a sealed in the hull/charge in the hull batt,twin speed controllers to a pair of water jets,  no ifs or butts over a week unless i disconnect the battery from the system it flattens a 5000 mah battery, same with another boat,  i forgot to disconnect the batt lead , charged it, fitted batt, forgot about it for a week, went the pond assuming ok, near dead, as luck would have it i was carrying a couple of spares