Isolating charger socket

[mowgli]

I use a battery conditioner and have a socket installed just above the number plate. I noticed the other day that the terminals in the socket are corroding aggressively. I suspect that this is because the socket terminals remain live connected to the battery and that moisture is acting as an electrolyte.

I am considering replacing the plug/socket and installing a relay as in the attached diagram to electrically disconnect the socket when not charging. I am not a sparky so am interested in views on why this will or won't work. TIA

[AllanB]

Mines under the seat and has a little cover over the end - no problem :sunny:

[mossy1200]

once the charger latches the relay then your bike battery will keep it latched even when charger is removed.

[bogan]

once the charger latches the relay then your bike battery will keep it latched even when charger is removed.

agreed, get a diode instead

[mowgli]

once the charger latches the relay then your bike battery will keep it latched even when charger is removed.
I don't understand. The relay is held latched through the plug. When the plug is removed the circuit through the coil is broken and the relay should trip.....either that or my leccy knowledge is poorer than I thought :(

[mossy1200]

I don't understand. The relay is held latched through the plug. When the plug is removed the circuit through the coil is broken and the relay should trip.....either that or my leccy knowledge is poorer than I thought :(

Once the relay coil livens the contacts close and you have completed the charging circuit.The problem is that you have created two live feeds to the coil.As long as the coil has a feed then it will remain latched.

Nah my bad didnt see the position of the plug socket and assumed you had 2pin socket.Sorry.Is correct

[bogan]

I don't understand. The relay is held latched through the plug. When the plug is removed the circuit through the coil is broken and the relay should trip.....either that or my leccy knowledge is poorer than I thought :(

on closer inspection you're right, using a 3pin plug will sort it

[mossy1200]

on closer inspection you're right, using a 3pin plug will sort it

Did you just change it cause i just said sorry for not seeing the socket correctly.Thought I had gone mad. LOL

[mowgli]

I could have been clearer in my description. I couldn't find a convenient 3pin socket in Eagle so simply left it as a gap. Thanks for the advice.

[bogan]

Did you just change it cause i just said sorry for not seeing the socket correctly.Thought I had gone mad. LOL

nah i also thought he was using a 2 pin connector, didnt even see your edit

[NinjaNanna]

be interesting to hear your results - whether electrolosis is contributing the corrosion or if it just good old fasion rust from the road spooge.

be good if you remember to post back in a month or so

Cheers
NN

[mowgli]

Doh! The charger won't energise the relay, I guessing because the charger is expecting to see a voltage or perhaps the resistance across the battery before it will switch to charge mode.

I need to rethink my circuit :o

[bogan]

must be a fandangled charger, or is it a low current trickle charger? Im unsure what exaclty a battery conditioner does

[mowgli]

It's a trickle charger (1600mA) then once the battery is charged fully it goes into a maintenance mode to keep the battery healthy. It turns itself on and off automagically when you (dis)connect to the battery.

Might have to use a transistor as a switch and draw power from the bike battery to energise the relay. I can use the third pin in the charger plug to switch between floating and ground.

[bogan]

drwing power from the bike is prolly the way to go, you could still use (just the) the relay, have the plug connect relay coil ground to bike ground when its plugged in, and the other side of coil on battery +ve.

[mowgli]

But doing that leaves one of socket pins live. I'm trying to leave the socket grounded to avoid electrolysis. It's possibly the world's worst schematic but I've attached a picture to give you the general idea of where I'm going. Use the plug to pull the base low. Your thoughts?

Edit: That's a PNP transistor

[bogan]

But doing that leaves one of socket pins live. I'm trying to leave the socket grounded to avoid electrolysis. It's possibly the world's worst schematic but I've attached a picture to give you the general idea of where I'm going. Use the plug to pull the base low. Your thoughts?

Edit: That's a PNP transistor

hmm, she's getting well complicated now (would need a base resistor as well), is there not an easier non-circuitry solutions, such as plated terminals, or a cover for the plug?

[mowgli]

Complicated? Nah, would probably fit neatly on the end of the relay in a bit of resin. You're right regarding the base resistor. My bad.

I could stick the socket under the seat but then that's not as tidy as "pull up, plug in and walk away". Plated terminals could work. The previous socket had a cover. I think that lead to the condensation.

[bogan]

you may find that a pnp will also put positive voltage on the wire (base)

[mowgli]

you may find that a pnp will also put positive voltage on the wire (base)
Hmmm, of course it does :doh:
It's been a fun exercise but I'm beginning to think an electronic solution is a bit beyond me. Thanks for the help.

[bogan]

Hmmm, of course it does :doh:
It's been a fun exercise but I'm beginning to think an electronic solution is a bit beyond me. Thanks for the help.

looks like a quality job though!

Think the problem is you need to pass a signal without using any voltage (current signaling requires less voltage but there must be some), so you're going up against the laws of physics

[mowgli]

By inverting the low input and driving an NPN I can reduce the voltage at the pins to quite low (see diagram) but that's about the best I can do. Damn laws of physics :oi-grr:

Edit: T1 and T2 are both BC547

[NinjaNanna]

its all very foggy to me - so don't crucify me if I'm wrong but I think your problem may be that your 2k4 base resistor is too big.

Base current for the BC178 is 50mA (100mA max) your resistor only allows 5mA to flow meaning the transistor is hardly turning on.

Try a resistor 220ohm resistor or 150ohm

[mowgli]

its all very foggy to me - so don't crucify me if I'm wrong but I think your problem may be that your 2k4 base resistor is too big.

Base current for the BC178 is 50mA (100mA max) your resistor only allows 5mA to flow meaning the transistor is hardly turning on.

Try a resistor 220ohm resistor or 150ohm
My bad! The schematic is not up to date. The relay only draws 30mA so the transistor doesn't need to turn on fully (I think). I ended up using a PN200 and a 2k2 base resistor. All very approximate when you're scraping the bottom of the components drawer.

Anyway it works in the sense that it switches the relay when plugged in. It still fails to reduce the potential between pins in the unplugged socket. Hence my later schematic using an inverter. Again all very approximate :)

[mossy1200]

Just a thought.If your current plug has copper terminals it will oxidise reguardless of power at socket or not.You need to have silver terminal ends on the socket.

[mowgli]

Just a thought.If your current plug has copper terminals it will oxidise reguardless of power at socket or not.You need to have silver terminal ends on the socket.
It's been fun but I think this is the answer. A marine grade plug and socket will no doubt sort this out.

[bogan]

It's been fun but I think this is the answer. A marine grade plug and socket will no doubt sort this out.

yup, sometimes the most fun projects are the one that dont do bugger all!