Power Management System wired to Alternator or ign live?

BongoNess · Post by **BongoNess** » Sat Apr 28, 2007 2:26 pm

Hi guys,

Hoping for some advice / reassurance from the electronics experts out there.

I have a PMS 34 power management system fitted in my converted van, but I'm not sure if it is wired correctly.

There was originally a wire running from the PMS unit to the Live feed on the alternator (this was fitted by the company who originally converted the van). However, this set up was drawing current from both batteries when the engine was switched off - irrespective of which way the battery selector switch on the PMS was pressed.

I know that on some vehicles, the alternator is only live when the ignition is switched on, but in the Bongo the alternator is always live, so I made an assumption that the connection to the alternator was supposed to be an on/off feed to a relay, and I've now removed the alternator connection and re-routed it to an ignition live in the dashboard fuse box.

This now allows me to select which battery is used to power the fridge etc. when the ignition is switched off (i.e. current is drawn from just the leisure battery when "van" is selected and just the vehicle when "car" is selected).

When the ignition is switched on, both batteries are re-connected in parallel, allowing the vehicle battery to charge the leisure battery when the engine is running.

First of all - can anyone tell me if I've missed a trick, and my modifications are wrong

... (or hopefully confirm my diagnosis and congratulate me on a problem solved $\:D/$ )

Secondly - If what i've done is correct - I wonder if anyone else out there has their PMS wired up to the alternator and are risking a flat starter battery in the morning

BongoNess · Post by **BongoNess** » Sun Apr 29, 2007 7:35 pm

Hmmm. Obviously no-one has had this problem - or no-one understood what I was going on about - which I think is more likely as I've just tried to re-read my post and I can hardly understand it myself!

I'll stick with my modifications for now and let you know if anything blows up as a result ....

Cheers,
Steve...

francophile1947 · Post by **francophile1947** » Sun Apr 29, 2007 7:39 pm

Hi BongoNess
I didn't understand your post because I haven't got a conversion - I'm sure it must have made sense to somebody, maybe

pippin · Post by **pippin** » Sun Apr 29, 2007 8:22 pm

I have never heard of a PMS34 management system and from the deafening silence it seems that no one else out there has either.

Is there a manufacturer's name on it?

BongoNess · Post by **BongoNess** » Mon Apr 30, 2007 11:56 am

Thanks for posting guys - the makers name on the pannel is "Plug-In Services". It's an unusual conversion - photos here if you want to have a look.

I guess the main point in my original post was to do with connecting to the alternator. I've seen some previous posts where people talk about wiring a split charge relay to their alternator, and I was wondering if this might be the wrong thing to do on a Bongo, as the alternator is always live...?

Cheers,
Steve

pippin · Post by **pippin** » Mon Apr 30, 2007 12:47 pm

The main positive output terminal is always live on most vehicles, it is always connected to the engine battery.

We are talking about the charge light terminal on the alternator.

Usually the positive of the bulb goes to positive when the ignition is switched on. The negative of the bulb goes to the charge terminal on the alternator, which goes down to 0V (chassis) when the alternator output voltage is higher than the battery voltage.
Thus the lamp only lights when the battery voltage is lower than the alternator voltage, to indicate that the battery is not getting a charge.

This usually happens briefly at switch-on, but will happen if there is a fault such as alternator drive belt failure or even indeed if the alternator packs up.

The charge terminal can also be used to energise a relay for secondary battery charge switching.

The relay coil is connected to 12V IGN ON and the other side to the charge terminal.
The relay will not energise until the alternator is producing an output.

The relay has three purposes:
To charge the secondary battery from the alternator.
To isolate the secondary battery (and its wiring) from the engine battery during the starter motor operation period.
To isolate the engine battery from the secondary battery to prevent the engine battery from being used (and being run down) by secondary loads.

Clear? As mud?

dandywarhol · Post by **dandywarhol** » Mon Apr 30, 2007 4:52 pm

Usually the battery charge light earths through the alternator windings so when there's no charge from the alternator the bulb lights via that route.
When the alternator starts to produce current, it puts it back up to the bulb - the bulb then has two positive supplies (no it's not a Japanese bulb

) to each side of it (therefore no earth) and the light extinguishes.

BongoNess · Post by **BongoNess** » Tue May 01, 2007 11:34 pm

Thanks for the advice guys.

My reason for thinking that there might be an ignition live on some alternators is that when I recently wired in the relay for the charging socket on my tow bar, the Tow-Sure instructions said to wire one end of the relay coil to the alternator for UK vehicles, or to an ignition live on non-uk vehicles. I assumed that this meant that UK vehicles have an ignition live on the alternator, but it sounds like I'm wrong?

I'm not sure my recent mods were correct - I think this needs some further investigaton...

...Cue multi-meter...

Cheers,
Steve

corblimey · Post by **corblimey** » Wed May 02, 2007 9:15 am

Hi Bongoness

Is it one of these?

Duncan · Post by **Duncan** » Wed May 02, 2007 3:24 pm

wheres the best place to tap into the 12volts on/off alternator light.
I have wired to both my batteries from the relay as per instructions, and earthed the correct terminal, its just wiring to the alternator I am struggling with. I have found the plug in the side of the alternator that carries two wires, is it one of them ?

Cheers

BongoNess · Post by **BongoNess** » Wed May 02, 2007 6:26 pm

Hi Bongoness

Is it one of these?

That's the one Cor Blimey - I'm just about to go outside and unscrew the pannel to see where the wires are going...

corblimey · Post by **corblimey** » Wed May 02, 2007 11:55 pm

The alternator output can only be "live" when the engine is running. If you're measuring a voltage at the alternator when the engine is off it must be via a connection to the battery.

The PMS is able to charge the batteries and also run your 12v accessories. I assume that it's been connected to the "live" feed of the alterator to provide this facility. It doesn't provide relay swithcing for split charging of fridge power as far as I can tell.

Without more info about the rest of the circuit it's difficult to work out what they were trying to achieve when it was originally wired up.

Sounds like we've got some wire crossed here (groan)

Give them a call and see if you can get a manual http://www.bonus-group.co.uk/index2.html and maybe we can work it out.

BongoNess · Post by **BongoNess** » Thu May 03, 2007 10:52 pm

Well - i've finally sussed it.

I took the panel off and found the relay complete with a handy sticker labelling the connections. The wire that was connected to the alternator is definitely supposed to be connected to an ignition live.

The main output terminal on my alternator is definitely always live (as Pippin says - it is connected to the engine battery). So the way the system had been connected up meant that the relay was always "on" even when the ignition was switched off.

I'm now happy that I've done the right thing by disconnecting from the alternator and re-connecting to an ignition live.

Thanks for the advice and feedback...

Cheers,
Steve.

Duncan · Post by **Duncan** » Fri May 04, 2007 8:08 am

Yep as you said, connecting to the alternator works but leaves the light on slightly, this because the relay is drawing to much current and dropping the 12 volts to 7 volts. Being stubborn and not liking being beat I have added another relay to drive the split relay charger. this relay only draws 40 milliamps on the coil so the voltage does not drop. this relay then drives the contacts on the heftier split relay charger. happy to say it now works. Thanks for the imput.

Cheers Duncan