CBE DS520AN - how to disable/negate the split charge relay

[arthur49]

I did consider adding this query to the end of my previous thread here

 

https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/CBE-CB516-charger-whats-the-white-signal-wire-/58257/

 

but the subject has altered somewhat so here goes on a new thread.

 

Everything is working fine - thank you Alan (and Mike from 'Veletron's thread') but I'm not achieving the full potential of the B2B, a Schaudt WA121545. This can deliver in selectable steps an output up to 70A but due to existing cable/fuse/DS520 limitations I can't utilise the B2B full potential. So currently the B2B is set to 45A ie approx 22.5A per lithium battery.

 

The Sterling Power LifePo4 batteries I have are specified at 70A max charge according to information leaflet (but box says 50A or 60A???), so I could safely set B2B to max and each battery would be getting approx 35A, well within it's limit.

 

So I'm considering installation of B2B in the conventional way ie direct on batteries, rather than installed between starter battery and DS520 as at present.

 

16mm2 cable is recommended by Schaudt so thats what I'll use with fusing as suggested by them.

 

BUT how to disable split charge relay in DS520. I'm aware the late Allan Evans didn't believe that was necessary and I'm technically incapable of defending or criticising his stance but disabling/negating the relay seems to me to be sensible. I realise electronically I could open DS520 and remove circuit board to desolder a resister I think it is but I'm not willing to do that.

 

So what I am thinking about is installing a changeover relay, with diode, between the DS520 and leisure batteries. I have one of these in my "spares" in garage!

 

https://www.12voltplanet.co.uk/mini-change-over-relay-12v-3040a-with-diode.html

 

Pin connections 85 - negative 86 - positive (from ignition on in DS520) 30 - from DS520 B2 87A - to leisure battery positive. And I could use the NO pin 87 to drive the D+ signal to B2B?

 

Or is there an easier way?

 

I could simply pull the existing fuse between starter battery and DS520 when B2B is taken out of that circuit but I'd lose electric step auto retraction on engine start

[Alanb]

Arthur,

 

What is the current rating of your proposed relay?

 

Why go against your principles and disable the split charge relay? In your previous thread you were unwilling to modify the DS520. I fully support you in this, as I prefer to keep the major units standard. This keeping it standard could be a big plus in an emergency situation, involving either a faulty DS520 or B2B (It can happen.) I was considering suggesting that you move your B2B connection point to the Output/Charger terminal of the DS520. I refrained from making the suggestion and causing further confusion.

 

Yes take the B2B output direct to the habitation battery, but with a suitable fuse close to the battery.

 

This will leave the DS520 B1+ terminal unconnected, and consequently no power supply to the fridge via the DS520 split charge and fridge relays.

 

I suggest running a new fused cable for the fridge from the starter battery, and install a separate fridge relay. In my B2B installation I used a changeover relay operated from the DS520 simulated D+ output with the NC (87a) contact connected to the DS520 B1+ terminal. For me this retained starter battery charge from EHU, and the ability to check starter battery voltage on the DS520 when parked up. I used a micro automotive relay (as used in various Fiat Ducato and similar vehicle applications).

 

With your Victron charger, you do not have the mains ON signal (white wire), hence no charging of starter battery from this source. Also no sensible reading of B1 (starter battery) volts through the B2B.

 

I was disturbed by Allan Evans advice that disabling the split charge relay was not necessary when a B2B is fitted. ( I did not disable the split charge relay, but effectively removed the starter battery supply to it.) I did not wish to start a spat with a sick man, but sometimes think that I should have voiced my disagreement.

 

I agree that some action is necessary, otherwise the split charge relay creates a short circuit between the input and output of the B2B.

 

If adopting my suggestion, you could take the B2B D+ input signal, either from the DS520 simulated D+ output, or from the former fridge output with reduced fuse rating.

 

With the B2 +ve (habitation) battery input left intact, there should be problem with the electric step, and a small improvement in charging, due to not having the relay contacts in the charging circuit.

 

Have I covered all of your questions?

 

Alan

[arthur49]

Thank you Alan.

 

My aim is to achieve 70A charge rate from B2B which is why I was looking at options. The cabling installed by Wildax from starter battery to DS520 to leisure batteries is rated at 70A - which is also rating of DS520 split charge relay, so I can't utilise the current configuration if I switch B2B to 70A output.

 

"What is the current rating of your proposed relay?"

30A, which I would have thought was enough since no alternator charging will be passing through it. Mains charger is 25A output

 

" In your previous thread you were unwilling to modify the DS520."

Absolutely, which is why I've considered the changeover relay - no messing with DS520. We love this van, health issues mean this is probably our last van, but should we sell/trade it in I don't want it passed on with alterations making the next owner scratch his head!

 

"Yes take the B2B output direct to the habitation battery, but with a suitable fuse close to the battery."

Will give it a go

 

"I suggest running a new fused cable for the fridge from the starter battery, and install a separate fridge relay."

The fridge is a bit of a mystery. The Wildax schematic shows it powered from the starter battery with a relay ..... but there is a fridge connection in DS520. I need to do more investigation on the fridge to find out what may be required.

 

"With your Victron charger, you do not have the mains ON signal (white wire), hence no charging of starter battery from this source. Also no sensible reading of B1 (starter battery) volts through the B2B."

Got my 'Vs' confused its a Votronic charger! Starter battery can be mains charged from separate charger output connected to B1. I am able to monitor voltage as there is a bypass switch on B2B so effectively the starter battery and DS520 are connected when engine is not running, in the current configuration

 

Thank you Alan, very helpful. But I need to do a bit more checking out before I do anything

[arthur49]

Well Alan, that was interesting!

 

This morning I pulled the fuse between starter battery and B2B since that simulated no connection to B1 of DS520. Started the engine and noticed the step auto-retract, just as you said it would.

 

I then switched on fridge set it to battery and it too worked.

 

Checked the BMS app and noted a current draw from the leisure batteries over 8A. The sun was shining it was quite bright, so 120W of solar adding maybe 6A, suggesting an actual current draw of 14A - the fridge?. Despite the Wildax schematic showing the fridge drawing power from the starter battery it must be drawing power from the leisure batteries.

 

Its a winter project to check the fridge out further.

 

So it seems to me if I improve cabling from starter battery to B2B and connect it's 70A output direct to leisure batteries, all I need to do whilst driving is pull the above fuse - easily accessible on side of passenger seat.

 

Every day's a school day

[Alanb]

Hi Arthur,

 

On CBE DS520 & DS300, the fridge relay connects to the B2 (habitation) battery side of the split charge relay. I think that despite contrary statements from Wildax, they may well have connected the fridge via the DS520. Why would they adopt a different method?

 

The resistance of the fridge 12V element is about 1 Ohm, so at 14V alternator output, it will draw about 14A. Taking the simple route and pulling the B1 fuse will result in this 14A being supplied from the available output of your B2B. The alternative of installing a relay in the B1 connection (my suggestion), is automatic, and shifts the fridge load directly onto the alternator. This leaves the full B2B output available for battery charging.

 

I was forced into the above method as I only have room for a small B2B, and the choice at the time was either a rather bulky Sterling 50A unit, or the neater CTEK D250S at 20A output. The D250S does have the advantage of an integral MPPT solar regulator, with the ability to charge the starter battery, when the habitation battery has been charged.

 

May I suggest checking the alternator rating, perhaps from vehicle specification, rather than by crawling under the vehicle. I would expect a rating of at least 120A, possibly 150A. Allan Evans advised against running the alternator at max for an extended time. Now that I do agree with.

[mikefitz]

The Renault Master 170 was fitted with either a 150 amp or a 185 amp alternator.

The chart below is the converters information for allowable load on the van electrical system for the 185 amp alternator.

 

Mike

[arthur49]

Thank you Alan and Mike. Van has the 185A alternator fitted. Confirmed via My Renault app .... However app does not advise which turbo version I have!

 

I recall watching this a while back and whilst I want to maximise charging, I want that to be safe for the alternator, so I'm not going to set the B2B at 70A even if I go ahead with improved cabling etc!

 

[arthur49]

Alan and Mike.

 

Please be assured that your input has been invaluable. I'm learning more and more about the kit in my van and the CBE DS520 appears very flexible.

 

But the max charge figures Mike posted yesterday are concerning. Potentially, since I don't know which turbo I have, the max charge at tickover (traffic lights, queues etc) is 39A!

 

In the circumstances I'm going to stick with my set up since its now working well. By cranking the B2B up to 50/60/70A I reckoned I was safely within the 185A rating of my alternator ...... but above all I want efficiency and no risk of overloading the alternator

[arthur49]

Final update on this thread.

 

The alternator figures Mike posted caused me concern. My van does have twin turbo (its a flying machine!) and 39A max draw at tickover of 900rpm is too low for a 45A B2B if I want to respect my alternator.

 

So volte-face. Instead of looking to increase charge rate I want to get it down.

 

So I now have installed a Votronic 30A B2B which at the push of a button can be reduced to 20A temporarily. New 16mm2 cables from starter to leisure batteries. And its working great.

 

Alan - installed B2B in the conventional way direct on batteries. Reconnected starter battery to B1 using original cable. Mains charger output for starter battery connected to B1. I'll wire fridge as you suggest off starter battery but no rush. And I like your relay installation on B1, that too will follow. Thank you again (and Mike) for guiding me through this.

[DamperVan]

Hello All,

With respect to the original post on how to disable the split charge relay on the CBE DS520AN, can anybody advise whether this is technically possible and if so, how to do it. I have read many of the posts in respect to this and the reasons of why/why-not to do this, but in my case I do need to disable the split charge relay rather than going down alternative routes of disconnecting the van battery wire (+B1)

I have the necessary skills and tools to perform the potential task is hand, but I have no idea on how to do the disabling in the best manor without removing the DS520 and performing circuit track tracing (which is a difficult task in itself.)

I would like to install a B2B Votronic 1212-30 charger to help keep my leisure battery in tip top charge. The current scenario that I have is that the intelligent alternator (Bosch 150A, brand new) which is controlled by the ECU, keeps dropping it's voltage output to 13.4V when the ECU thinks the Van battery is charged. The downside of this is that the leisure battery then drops it's voltage as it is in parallel with the van battery because of the split charge relay. By "breaking" this connection, the leisure battery can be controlled/charged separately from the van battery and left at full charge when the engine is turned off.

There are no other problems with any electrics in the van, everything operates fine. Model of the base van is a Fiat X250 3.0 160 2007.

I am aware that there may be "side effects" of disabling the split charge relay, but I have not found any information anywhere to indicate of exactly what the effects are (EG, no concrete evidence, just suppositions or references to different boards). If there are potential side effects, then I would like to know what they are so that I can mitigate or work around them. I am aware that the 12Volt relay for the fridge "MAY" be a problem and accept that I may have to provide an additional relay & wiring for this, but again, I'm not 100% sure.

 

Any guidance would be appreciated. Thank you

 

Chris

 

[arthur49]

Chris

 

I have the same B2B as you. I ran two new cables + and - from starter battery to B2B leaving the originals in place. I found that if I pulled the original 50A fuse in cable from starter to DS520, effectively disabling existing split charge relay, I lost little functionality whilst driving.

 

But if you want to go an alternate route why not do as Alan has done ie

 

"In my B2B installation I used a changeover relay operated from the DS520 simulated D+ output with the NC (87a) contact connected to the DS520 B1+ terminal. For me this retained starter battery charge from EHU, and the ability to check starter battery voltage on the DS520 when parked up. I used a micro automotive relay (as used in various Fiat Ducato and similar vehicle applications)."

 

Check his earlier posts in his thread at 1 August 7.11pm

[DamperVan]

Hi Arthur,

Thanks for the reply. Both the suggestions are possible. I'm going to give it some more thought before I get the tools out. I'm off to France for a couple of weeks so I'm going to leave everything as standard. The B2B will have to wait a bit longer.!!

I do think that the 12V (3 Way) fridge will have to be fused and relayed separately (fed from the van battery) and I don't think there is anyway around this once the van and leisure battery are electrically separated on the DS520. Leaving the fridge on the leisure battery will just mean the the B2B will be supply power to the fridge which sort of defeats the point in "intelligent" leisure battery charging.

 

Thanks

 

Chris

[DamperVan]

An update. So just to say I have now installed the B2B after thinking long and hard about the way to complete the installation without too much modification and I ended up sort of using various ideas to come up with a good solution.

 

Basically installed the B2B and connected to the +Van battery incoming supply (Via a 40A fuse). I then removed from the DS520, the +B2 incoming leisure battery wire from the DS520 and connected it to a NC Relay . The output of the relay was then connected to the +B2 connector on the DS520 with a new cable. The 85 Pin (coil with diode) was connected to ground and 86 pin connected to the simulated D+ from the DS520.

 

The Votronic B2B has a input to enable/disable the B2B charging and this was connected to the simulated D+ signal from the DS520.

 

The result works perfectly. The net effect is that when the DS520 detects the engine is running, the simulated D+ signal is activated. At this point the split charge relay (in the DS520) also energizes, thus connecting +B1 to +B2. My new NC relay which was closed, and thus allowing the leisure battery voltage IN to the DS520, is now disconnected as the new NC relay opens. Also at the same time, the fridge 12V relay is also activated on the DS520 and so the fridge works on 12V. The 12V supply to the fridge relay actually comes off the +B2 side of the split charge relay, and as the leisure battery is now disconnected, the fridge relay can only get it's power from the van battery. Meanwhile, the B2B charger is happily charging the leisure battery to it's correct charge profile with no accessories taking any of that current and distorting the charging profile dynamics.

 

Initial testing shows that leisure battery is getting it's full charge voltage 14.5 and when I arrive onsite, it is fully charged. Need to test it a bit harder with longer weekends away, but looking good so far.

 

I've attached a couple of screen shots of the Smart Shunt which shows the pre-B2B voltages and after B2B voltages. The dip in the van battery voltage on both screens is when the fridge was turned on to 12V from gas.

 

Hope this helps somebody else wishing to do the same.:-)

 

Chris