Electrical Circuit diagram for Setec ST-35 power supply - here it is!

[gregp]

Hi guys,

If anyone's ever looking for the circuit diagram for the Setec power supply in their van, here it is attached for the 35 v3 from my 2013 Discovery. Our 2010 Expanda had an earlier version which is probably pretty similar. I requested this from Setec with the view to modifying the charging profile to suit lithium, and while I may still do that I'm more just sharing it here in case anyone else needs it for anything else.

Greg

 

[Boots in Action]

Hi Greg, the full diagrammatic electrical circuit for your Setec ST35 Series III is great for any of those who can follow the full circuit diagram. However, for those that cannot, I can tell you a fair bit about this unit as I have attempted to do something about the low charging voltage put out by this unit as I have the same unit in my Penguin only the 20 amp version. (ST20)

The main problem is that the voltage output to charge the battery is limited to only 14.0 or maybe 14.1. This may have been very suitable for GEL batteries which only require 14.2 or 14.3 volts for a FULL charge. However, this is not satisfactory for AGM batteries which really need 14.7 volts for a FULL charge. In an effort to alter this or get around it somehow, I have tried a few different ways including applying a 240 volt AC "smart" charger directly to the INPUT wires at the connector (pins 8 pos and pin 10 neg earth return) to charge a low battery. Whilst the input voltage from the charger reached 14.7 volts, the actual charge voltage at the battery did not get any higher than 14.0 volts (but no higher!) proving that the reverse bias resistance of the power diode in the input circuit was reducing the charging voltage by 0.7 volts. Looking at the circuit diagram (basic schematic), I decided to dismantle the unit to see if I could remove (or bypass) the power diode by following the output wire from the Setec. I found the diode eventually buried in the electrics!!. It is attached to the main chassis which acts as a great heat sink for the diode which blocks any voltage/current from the vehicle battery when discharging. So as that was not feasible or practical, I gave that idea away.

So as I am still with AGM systems, I use my 15A 7 stage "smart" charger direct to van battery whenever I need to keep my van battery fully charged and only use the Setec in the van for charging when at a caravan park. The van battery gets a FULL charge from my "smart" charger when I get home.

It will probably be easier and cheaper to bypass the Setec charging system and only use it as a power distribution system. A separate lithium charger suitable for 240 volt AC and 12 volt charging from vehicle (with DC to DC ability to meet the varying charging voltages of "smart" alternators) would also be required to charge lithium batteries correctly with their own algorithm for charging. Good luck and I hope this helps.

PS. You are not the only one who has attempted to change things. There are some other members on this forum that have also had a go and may wish to add more technical experience.

 

[gregp]

Hi Greg, the full diagrammatic electrical circuit for your Setec ST35 Series III is great for any of those who can follow the full circuit diagram. However, for those that cannot, I can tell you a fair bit about this unit as I have attempted to do something about the low charging voltage put out by this unit as I have the same unit in my Penguin only the 20 amp version. (ST20)

The main problem is that the voltage output to charge the battery is limited to only 14.0 or maybe 14.1. This may have been very suitable for GEL batteries which only require 14.2 or 14.3 volts for a FULL charge. However, this is not satisfactory for AGM batteries which really need 14.7 volts for a FULL charge. In an effort to alter this or get around it somehow, I have tried a few different ways including applying a 240 volt AC "smart" charger directly to the INPUT wires at the connector (pins 8 pos and pin 10 neg earth return) to charge a low battery. Whilst the input voltage from the charger reached 14.7 volts, the actual charge voltage at the battery did not get any higher than 14.0 volts (but no higher!) proving that the reverse bias resistance of the power diode in the input circuit was reducing the charging voltage by 0.7 volts. Looking at the circuit diagram (basic schematic), I decided to dismantle the unit to see if I could remove (or bypass) the power diode by following the output wire from the Setec. I found the diode eventually buried in the electrics!!. It is attached to the main chassis which acts as a great heat sink for the diode which blocks any voltage/current from the vehicle battery when discharging. So as that was not feasible or practical, I gave that idea away.

So as I am still with AGM systems, I use my 15A 7 stage "smart" charger direct to van battery whenever I need to keep my van battery fully charged and only use the Setec in the van for charging when at a caravan park. The van battery gets a FULL charge from my "smart" charger when I get home.

It will probably be easier and cheaper to bypass the Setec charging system and only use it as a power distribution system. A separate lithium charger suitable for 240 volt AC and 12 volt charging from vehicle (with DC to DC ability to meet the varying charging voltages of "smart" alternators) would also be required to charge lithium batteries correctly with their own algorithm for charging. Good luck and I hope this helps.

PS. You are not the only one who has attempted to change things. There are some other members on this forum that have also had a go and may wish to add more technical experience.

Thanks Boots! Yeah I am considering a dedicated lithium charger as a possibility, I had just hoped it would be an easy modification. The Setec still gives me about 80-90% capacity charge on the lithium batteries, however because it only delivers 13.65V for the first 24 hours of it being connected (as opposed to delivering it until charge state reaches a certain threshold) I have to disconnect the mains for a few minutes every 24 hours to get it back up to 13.65V rather than the VStore of 13.25 it otherwise reverts to. Otherwise they only get about half charged.

TBH, 80-90% charge isn't a bad state to store LiFePo batteries in anyway, they tend to get topped up by the solar panel when in transit.

 

[jazzeddie1234]

Hi guys,

If anyone's ever looking for the circuit diagram for the Setec power supply in their van, here it is attached for the 35 v3 from my 2013 Discovery. Our 2010 Expanda had an earlier version which is probably pretty similar. I requested this from Setec with the view to modifying the charging profile to suit lithium, and while I may still do that I'm more just sharing it here in case anyone else needs it for anything else.

Greg

oooh this is brilliant! Thanks for posting it. I will also have a look to see if the float can be tweaked a bit higher for lithium

 

[jazzeddie1234]

TBH, 80-90% charge isn't a bad state to store LiFePo batteries in anyway, they tend to get topped up by the solar panel when in transit

That's how I do mine plus a few things. The Setec is quite happy with multiple chargers so I have a cheap 240 to 12v (adjustable) 30 amp smps that I can plug into an anderson when I'm in a hurry - like when using the generator. It can be set to 14.6v or a bit higher and is way way cheaper than a 30a battery charger. The batteries are also wired to an anderson on the towbar and that is connected to my dc dc in the ute, so that path can top them up too

 

[Drover]

Handy diagram, I think I have one for the earlier version somewhere, be interesting if you can tweak it .................................... With a decent MPPT solar reg you really don't need a mains charger for any battery other than emergencies, well at least I haven't, don't even have the capability to charge from tug been that way for many years and go away for months at a time just solar charging the system..... since I never used the mains charger when I had GELs I never bothered with a lithium capable when I went Lithium, I could use my old AGM/GEL charger if needed but of course everything goes to float early when lithium gets to about 13.2v which isn't a biggy ............

 

[Boots in Action]

Thanks Boots! Yeah I am considering a dedicated lithium charger as a possibility, I had just hoped it would be an easy modification. The Setec still gives me about 80-90% capacity charge on the lithium batteries, however because it only delivers 13.65V for the first 24 hours of it being connected (as opposed to delivering it until charge state reaches a certain threshold) I have to disconnect the mains for a few minutes every 24 hours to get it back up to 13.65V rather than the VStore of 13.25 it otherwise reverts to. Otherwise they only get about half charged.

TBH, 80-90% charge isn't a bad state to store LiFePo batteries in anyway, they tend to get topped up by the solar panel when in transit.

Interesting about charging @gregp. Using the existing Setec ST20, when I connect the unit to 240 volt power. If the van battery is about 12.7 volts or so and not really discharged very much, initially battery voltage climbs quickly to 14.0 volts for a while (full charge voltage - best it can do!!!) before dropping back to 13.60 volts (float voltage). When left on "float" for up to 24 hours, (and no extra loads applied) I have seen it drop back to 13.20 volts (storage) for a while before reverting to 13.60 volts again. According to the booklet, this is what one can expect. I also note that when connected to 240 volts, a constant voltage of 13.65 volts is maintained regardless of power draw, either 240 volt or 12 volt and did not seem to be affected by size of load either. Be it 2400w on 240 volt or 16 amp draw of fridge at 12 volts. If battery voltage is low, there is no reason for Setec to reduce power or change charge voltage voltage and I believe that "store" voltage will only be activated after 13.65 volts ("float") has been on for a 24 hour period, You should be getting the max charge voltage initially unless the Setec thinks your lithium is less than 14.0 volts or the lithium BMS has something to do with it. Just my ideas and observations with my own system.

 

[Drover]

If your on mains power its not an issue really as when camping as the Setek runs things and battery isn't needed and if starting off with 80 or 90% charge when going off grid the solar will sort it out and thats the important bit ........ If not off gridding then no battery ever needed.

This morning things were at 13.1v when I fired up the heater ....

 

[Boots in Action]

If your on mains power its not an issue really as when camping as the Setek runs things and battery isn't needed and if starting off with 80 or 90% charge when going off grid the solar will sort it out and thats the important bit ........ If not off gridding then no battery ever needed.

This morning things were at 13.1v when I fired up the heater ....

True Ian. However, if a battery is installed and is low (discharged), the Setec will not only provide 240 volts for that (240 volt) equipment, it will also provide power for the 12 volt loads. This would include charging the low battery to a FULL state of charge. However, the total of all 12 volt loads (including battery charging) is limited to 20 amps for the ST20 versions and 35 amps for the ST35 versions. Any battery charging would have to be at the higher charge voltage, perhaps reduced somewhat by the amount of other 12 volt loads on at the time.

 

[Drover]

True Ian. However, if a battery is installed and is low (discharged), the Setec will not only provide 240 volts for that (240 volt) equipment, it will also provide power for the 12 volt loads. This would include charging the low battery to a FULL state of charge. However, the total of all 12 volt loads (including battery charging) is limited to 20 amps for the ST20 versions and 35 amps for the ST35 versions. Any battery charging would have to be at the higher charge voltage, perhaps reduced somewhat by the amount of other 12 volt loads on at the time.

Oh yeah, see your point but if I had a battery really down and I was on shore power I would be concerned as to why and really any battery thats got so low it will suck 20a then it really needs to be on a bench charger to get properly brought back to life................ If you want the Setek to go max charge then you just turn some things of in van and really during the day power use would/should be minimal ............

If you have lithium in van then you would have a decent solar controller and the Setek would be really be redundant and be set to just run the van, I could see no reason if using parks all the time or even most of the time why even fit a lithium as shore power would be doing the work and money could be better spent .............. If Big Mal is on shore power I can have batteries charging solely from the solar MPPT and the van power supplied by the old AGM charger which will just shunt 13v to the van to run things, it still has a use, mains only running fridge, toaster and HWS everything else is 12v..............

But back OT, of course I would be tinkering with things, still do even if not really needed, I did fiddle around with my old Setek way back and was surprised it didn't melt down, had followed notes by someone else from on here. .....................

 

[Boots in Action]

Oh yeah, see your point but if I had a battery really down and I was on shore power I would be concerned as to why and really any battery thats got so low it will suck 20a then it really needs to be on a bench charger to get properly brought back to life................ If you want the Setek to go max charge then you just turn some things of in van and really during the day power use would/should be minimal ............

If you have lithium in van then you would have a decent solar controller and the Setek would be really be redundant and be set to just run the van, I could see no reason if using parks all the time or even most of the time why even fit a lithium as shore power would be doing the work and money could be better spent .............. If Big Mal is on shore power I can have batteries charging solely from the solar MPPT and the van power supplied by the old AGM charger which will just shunt 13v to the van to run things, it still has a use, mains only running fridge, toaster and HWS everything else is 12v..............

But back OT, of course I would be tinkering with things, still do even if not really needed, I did fiddle around with my old Setek way back and was surprised it didn't melt down, had followed notes by someone else from on here. .....................

Oh you of little faith!! It is true trying to teach "old dogs" new tricks. They do take some convincing.

 

[Drover]

Oh you of little faith!! It is true trying to teach "old dogs" new tricks. They do take some convincing.

I knew it would take time and you would agree eventually....... or are we saying the same thing ?????