The Ideal Diode / Leisure battery switch, charging thingy

[francophile1947]

I haven't got a clue what most of this is about, as it's beyond my electrical knowledge, but would a heat sink, used in computer processors, help with the heat problem?

[dandywarhol]

OK, (don't get too excited!) Nearly there..................


To recap this 'Device' will be inserted in the +Ve lead of the main battery and connect to the +Ve terminal of the leisure battery, it will need a good ground and will be SMALL! because it will use 'Semiconductors!'

It will allow the leisure battery to be charged from the main whilst maintaining complete isolation, any current greater than 12A(???more/less???) will cause the 'Device' to PWM the o/p and also drop the Volts a little due to the action of the circuit, I'm hoping this will help to limit the inrush of 'I' to a deeply discharged battery.

I've set it up to only switch on and conduct 'I' at 13V5(???) any less and it'll be 'Off'. So will only charge 'Leisure' when 'Main' is full.

Reverse 'I' is impossible but can make it so at the flick of a switch (if you really needed to charge the Main batt from the Leisure batt?)
I can also use the same circuit slightly modified to monitor the o/p of the leisure battery and isolate the load when 'V' drops below 11V5 (suggestions please) and will also turn off when a preset current (???) is reached.

So if I can get the thing to work you may want to buy 2!

This is 'Work In Progress' and can't guarantee anything here but it may work well for lead acid charging / isolation / monitoring.

I'll post as soon as I've got a finished model and will be wanting some willing 'Victim' to test it!

Charging batteries isn't too difficult it's looking after them that's the problem and I'm hoping my 'Device' may go some way to sort out this 'Problem'

JnK.

Sounds really interesting JnK and well done. I have an inadequate VSR on mine that I currently have to protect with 30amp fuses. I keep meaning to upgrade it but as I'm watching the £ and as my setup is coping OK, I just live with it and avoid deep discharge ( ). If your idea passes muster on test, are you thinking of offering them for sale and at what cost if so?

Once again, well done. Great to see so many innovators on this site. Better than listening to hedge fund managers by a clear mile

THIS will sort out your problems for £7 Mike - as long as you've got 70 amp wiring to the LB.

It can be switched by your "inadaquate" relay

[mikeonb4c]

OK, (don't get too excited!) Nearly there..................


To recap this 'Device' will be inserted in the +Ve lead of the main battery and connect to the +Ve terminal of the leisure battery, it will need a good ground and will be SMALL! because it will use 'Semiconductors!'

It will allow the leisure battery to be charged from the main whilst maintaining complete isolation, any current greater than 12A(???more/less???) will cause the 'Device' to PWM the o/p and also drop the Volts a little due to the action of the circuit, I'm hoping this will help to limit the inrush of 'I' to a deeply discharged battery.

I've set it up to only switch on and conduct 'I' at 13V5(???) any less and it'll be 'Off'. So will only charge 'Leisure' when 'Main' is full.

Reverse 'I' is impossible but can make it so at the flick of a switch (if you really needed to charge the Main batt from the Leisure batt?)
I can also use the same circuit slightly modified to monitor the o/p of the leisure battery and isolate the load when 'V' drops below 11V5 (suggestions please) and will also turn off when a preset current (???) is reached.

So if I can get the thing to work you may want to buy 2!

This is 'Work In Progress' and can't guarantee anything here but it may work well for lead acid charging / isolation / monitoring.

I'll post as soon as I've got a finished model and will be wanting some willing 'Victim' to test it!

Charging batteries isn't too difficult it's looking after them that's the problem and I'm hoping my 'Device' may go some way to sort out this 'Problem'

JnK.

Sounds really interesting JnK and well done. I have an inadequate VSR on mine that I currently have to protect with 30amp fuses. I keep meaning to upgrade it but as I'm watching the £ and as my setup is coping OK, I just live with it and avoid deep discharge ( ). If your idea passes muster on test, are you thinking of offering them for sale and at what cost if so?

Once again, well done. Great to see so many innovators on this site. Better than listening to hedge fund managers by a clear mile

THIS will sort out your problems for £7 Mike - as long as you've got 70 amp wiring to the LB.

It can be switched by your "inadaquate" relay

Yes, interesting. Doh! I guess I'd use my 'inadequate' VSR to activate the heavy duty relay and its heavy duty wiring? That should work eh? Got to admit it's so cunningly simple I don't know why I didn't think of it before (yes I know, you all know why )

[John and Kim]

Heat is bad and is power loss = to current squared * resistance or voltage squared / resistance; that's as complicated as it gets!

Heatsink not ness as I'm trying to make the 'Device' efficient and will have less volts dropped across it than a relay (honest!).

I know the main problem with the V.S.R. device is will break its contact when so much current is slurpled from the main battery as to drop its V.S. voltage.

I'll cool the thread for a while until I have a 'Real' circuit; it will be small tho' and will not require any heatsink other than the bolting it to the earthed body of the vehicle. It wont even need a fuse but one will be fitted for piece of mind.

I need to do 'Real' experiments with 'Real' batteries and capture what's actually going on, especially when the leisure battery is totally flat.

More Soon.

JnK

[simon638]

OK, Looks like I've got myself a project (too much time on my hands at work!) and have thought about this 'Problem' before.

How to connect the leisure battery to the alternator permanantly whilst;

1, allowing the Main battery to be fully charged first.
2, not allowing current to flow in the 'wrong' direction, i.e from Leisure to Main, or from Main to Leisure whilst engine not running.
3, lots of other things I probably haven't thought of yet!

Well there are the usual voltage sensing relays and the like (and this has been covered in depth on here before) but this is I think rather crude and there are more 'Modern' solutions.

Without getting even slightly technical (I'm an Electronic Engineer) I'd just like to gather a list of requirment of what this 'Device' must do.

It will be very easy to install, only having an earth tab and a connection in from the Main and connection out to the Leisure.

Ideas please.......................

JnK.

what you need to do it cut the large output wire from the alt,put a large diode in forward bias in the gap you cut (thats the van charging back to normal).
where you connected the first diode now connect a second (forward bias again) from the alt output to your new battery, job done.
both batteries will independenty charge, receiving the power needed to hit 14volts while never being connected directly,so neither battery could run the other one down.
The trouble with the other types that charge the main one first is,the system charges the main battery to about 13.8volts (nothing wrong with that you may think),then ADDS other battery (good system).
The problem comes when you put something power hungry like air con /headlamps etc,the main battery voltage drops below 13.8,so now the second battery is disconnected from the circuit therefore no charging on second battery.
so in the summer when you need the fridge on in the back, running from the second battery you cant have the air con on.
Hope you understood this.

[Manny]

The problem comes when you put something power hungry like air con /headlamps etc,the main battery voltage drops below 13.8,so now the second battery is disconnected from the circuit therefore no charging on second battery.

In the circuit I built, and I think most vsr are similar, there is some voltage hysterisis i.e.the LB charge relay comes on at about 13.5 V but does not drop off till about 12.8 V. The "drop off voltage" should not be made lower as that is the voltage of the fully charged SB after the engine is turned off.

Manny

[dandywarhol]

I've got an led guage in the rear of the van to indicate the LB voltage and it certainly charged with the a/c on when the coolbox was running from the rear socket.

[lizard]

Hymn to Diana (Ode to Cynthia)
QUEEN and huntress, chaste and fair,
Now the sun is laid to sleep,
Seated in thy silver chair,
State in wonted manner keep:
Hesperus entreats thy light,
Goddess excellently bright.
Earth, let not thy envious shade
Dare itself to interpose;
Cynthia's shining orb was made
Heaven to clear when day did close:
Bless us then with wishèd sight,
Goddess excellently bright.

Lay thy bow of pearl apart,
And thy crystal-shining quiver;
Give unto the flying hart
Space to breathe, how short soever:
Thou that mak'st a day of night
Goddess excellently bright.

Ben Jonson. 1573-1637

[John and Kim]

Just a quick update as I've decided to incorporate both circuits into one device, so;

Circuit 1 will;
1; Not allow current to flow to the leisure battery if the main battery is below 13V.
2; If a charging current of more than 20A is exceeded the circuit will PWM the charge current to protect itself and the Leisure battery until a Normal (<20A charge can commence).

Circuit 2 will;
1; Not allow current to flow from the Leisure battery if the voltage has dropped <10V.
2; Not allow current to flow from the Leisure battery if the current exceeds 20A.

current can NEVER flow from the Leisure to the Main (although it is easy to make it so for whatever reason)

The circuits will be in a small case which will need electrically earthing to the vehicle, little or no heat is generated but good electrical contact to the earth of the vehicle and short low resistance leads to the batteries are very important.
1 cable to MAIN, 1 to LEISURE and 1 OUTPUT all fused at 30A (externally)

LED indication will provide the user with visual indication of the mode of operation;

GREEN = NORMAL (charging) or IN USE (in the case of the second circuit) DEVICE ON!
RED = OFF (Under Voltage on either circuit, so not connected for circuit 1 and 2.) DEVICE OFF!
AMBER Pulse (first circuit only) PWM Charge. This to indicate a possible battery fault or just too deep a discharge but this should not be possible and is why the second circuit is necessary.

No LED indication signifies a blown fuse in either circuit.

I've decided to go this way as it would seem the main problem is too deeply a discharged LEISURE battery, so using my 'Device' will not only stop the battery from being totally discharged it will also charge sensibly with indication.

OK I still need to know this is ALL I need to do, I can incorporate TEMP compensation to but that will take up some time in experementation but wont involve much expense other than my time. I have both circuits simulated and 1 is built and undergoing some rather brutal testing!

ALL voltages and currents are adjustable, I'm just using these values to get started and must do some trials to find the optimum values.

Let me know what you think.

JnK.

[teenmal]

Hi,Jnk
Looks like you have it covered,well done.

Cheers Mal..

[dandywarhol]

I think the 20A max limit will save a lot of the problems associated with LBs getting too much charge quickly and damaging them or shertening their life.
This is being discussed in another thread by Mike on b4t or whatever his name is

If you want some testing done I'd be happy to oblige.

Alan