Improvements to leisure battery charging

[Alanb]

aandncaravan - 2018-11-20 7:05 PM

 

If the Schaudt WA121xx unit is installed between the Starter battery and the CBE 'Starter Battery Input' terminal, then all the CBE system sees is a decent voltage, it won't be 'aware' of any other change or where that voltage has come from. That is the beauty of the WA and wiring it this way.

 

But you are right, the WA's current will be used to drive the Fridge, which is no bad thing as it will at least get a decent voltage and be more efficient.

There should not be any 'Feedback' issue and the WA should ramp up it's output to suit but it would require the 40 amp version to work well..

.............................................................

............................................................

 

 

Installing a Schaudt WA121xx in the suggested manner will permanently disable the CBE facility to mains charge the starter battery, and to read its voltage when the engine is stationary. Diverting the fridge supply via a changeover relay as I have done, preserves these facilities, and gives the fridge exclusive use of the original 6sqmm B1 supply cable while the engine is running. This should enhance the fridge performance if that is required. However in UK use we have not had problems with 12V operation, even when we forgot to switch it on. Further this method will not require a higher rated Schaudt WA unit.

 

In a PVC, mounting space is a prime consideration, and I elected to use a micro automotive relay rated at 25/15A to switch the fridge. The option remains to upgrade the fridge 12v supply cables, but a first target would have to be the makers tail cable which is of minimal csa.

 

When fitting my CTEK D250S B2B, there was a possible problem when on EHU, but as the Schaudt WA unit requires a D+ connection to switch it ON, this should not apply.

 

I agree with Allan's concern over total battery charging input, but perhaps Velotron could advise in this respect. I believe that at times, he wild camps in the Scottish Highlands in winter.

 

Alan

 

 

 

 

 

[aandncaravan]

arthur49 - 2018-11-20 9:09 PM

 

aandncaravan - 2018-11-20 7:05 PM

 

If the Schaudt WA121xx unit is installed between the Starter battery and the CBE 'Starter Battery Input' terminal, then all the CBE system sees is a decent voltage, it won't be 'aware' of any other change or where that voltage has come from. That is the beauty of the WA and wiring it this way.

 

 

Allan

 

But does this approach still mean there could be undue strain on the power distribution unit as it tries to pass higher current?

 

I recall your photos of burned out boards and relays. If a non-Schaudt distribution board is used isn't there a tendency for high current issues? My previous van had a pretty puny Sargent EC155 for example

 

Every day's a school day :-D :-D :-D

 

 

Yes all the boosted power will go through the CBE power controller, but you are only boosting it by a handful of amps, so it isn't an issue.

A CBE setup isn't perfect but a whole heap better than the Sargent EC155.

 

The CBE systems tend to have an Alternator charge voltage at the habitation battery, with Fridge on 12v, of about 13.9 - 14.0v, The Sargent will be lucky to show you more than 13.5v

 

So getting a CBE systems charge up to the recommended 14.4v, by thicker cables or Alternator boost charger, will normally give you a max of 5 amps extra per 100Ah battery.

 

None of that is going to overload the CBE 50a rated connectors.

 

 

That you think these changes might overload the CBE DS unit, also indicates you are expecting more from these gizmos than is likely?

 

 

 

 

[DavieR]

Here is the manual for the Schaudt WA121525 unit if anyone is looking for info -

http://www.produktinfo.conrad.com/datenblaetter/1600000-1699999/001628096-an-01-en-SCHAUDT_LADEGERAET_BOOSTER_WA_121525.pdf

 

Thanks again everyone. Perhaps the best thing to do is contact Schaudt and ask for advise. I'll get on to that tomorrow.

 

I take the point that we might not achieve the amps we need with the suggested and actual improvements but we want to maximise what we can get. How much we are prepared to spend for each extra amp is as yet unknown but selling the van and buying a higher spec'ed conversion is not an option. A DIY job lessens the cost, plus I get to know the van better which will be of great help when, inevitably, something fails in the future. And, I am enjoying it.

 

It might not be cost effective but I look at this way, every few extra amps achieved in effect lengthens the wild camping season. Perhaps we will have to drive a little more. We rarely switch the fridge on in the summer, so definitely won't be using it through the winter but we still want it wired up correctly. We have 18 years experience of long trips in a VW T4 camper so we know what we can cope with, and do without if necessary. The electrics were simpler too. "Oh, the red lights gone on, better go for a drive tomorrow then". First leisure battery did 11 years, never bought a third!

 

Regarding the mains charger, I thought to replace the CBE516 with the 520 (20amp). The next batteries will be 90 or 100Ah. Is there a better charger with a S (corrected from +D) signal out there?

 

Our leisure batteries are probably nearly shot too. Hopefully, I'll found out about that next week too.

 

Dave

[arthur49]

aandncaravan - 2018-11-20 9:48 PM

 

That you think these changes might overload the CBE DS unit, also indicates you are expecting more from these gizmos than is likely?

 

 

Not really Allan. I just like to fully understand all the implications! Every day's a school day :-D

[weldted]

Today's results, two days parked up on solar only. Temp last night -2 ran Alde heating all night, ( gas ) batteries at 10:00am 72% from 200 amp bank. Solar 1.1 amp input. Started engine 11 amps at 13.9 volts after ten mins switched on inverter 28.7 amps at 14.4 volts Drove for around hour and a half stopped with engine running inverter on 11 amps at 14.4 volts switched inverter off engine still running 5.2 amps at 14 volts. Engine off solar input 2.7 sky cloudy with sunny intervals. Drove another half an hour with inverter on last check with inverter on 6.3 amps

Inverter off engine running 3.7 amps 14 volts all off solar 2.1 amps solar computer shows batteries at 97%

Quite happy with that.

[aandncaravan]

DaveR, don't get me wrong, I applaud what you are doing and how thoroughly you are going about it.

As you say understanding how it works will make a huge difference to it's use, reliability and your ability to fix it.

 

 

Maximising everything is good, but if it was me I wouldn't be spending money on a CB520, it isn't the fastest charger or the best for long term float charging.

 

If you want real value for money, it is hard to beat the Victron charger range, the 20amp version : Blue Smart IP22 Battery Charger 12V/20A/230V is a 20a continuous charger, not the usual 'peak' ratings that are quoted.

It is value for money because you can take it with you when you change vans.

 

Don't remove the CB516, but install your new charger next to it and tie it into the existing chargers 12v out put cables and remove the 230v supply to the CB516.

.

When you change van, just remove the new charger and reconnect 230v to the CBE..

 

I agree with changing the Solar charger to a Votronic, because at £70 they are not expensive, easy to fit and a 40% gain in Spring, Summer and Autumn will be useful.

 

 

 

Welted, those are cracking charging currents. you certainly know your stuff.

Hopefully, you are seeing signs of the Yuasa L36-EFB batteries getting into their stride as well, as they will take a few cycles to reach full capacity?.

 

 

[DavieR]

DavieR - 2018-11-20 10:31 PM

 

Regarding the mains charger, I thought to replace the CBE516 with the 520 (20amp). The next batteries will be 90 or 100Ah. Is there a better charger with a +D signal out there?

 

Dave

 

That should be an S signal, sorry.

 

Edited. (Keithl).

[weldted]

Youasa L36! Hi Allan, yes they do seem to be working up well, my post forgot to mention the fridge was on 240 volt from the inverter so effectively being charged from the engine battery side so no drain on the leisure battery which I think goes a long way to acheive my results. The heavier cabling taking a new earth cable from the alternator body to both the engine and leisure batteries, and one from engine battery to the split charge and from there to the leisure batteries has given better charging in both volts and amps when not using the inverter. The Blue Smart 30 amp charger is also proving to be an excellent investment. It is wired directly to leisure batteries via the shunt so only charges them and has a switched relay if for any reason when on ehu I need to top up the engine battery but so far the Voltronic 350 mpp second output is doing it fine.

[DavieR]

aandncaravan - 2018-11-21 8:45 AM

 

Maximising everything is good, but if it was me I wouldn't be spending money on a CB520, it isn't the fastest charger or the best for long term float charging.

 

If you want real value for money, it is hard to beat the Victron charger range, the 20amp version : Blue Smart IP22 Battery Charger 12V/20A/230V is a 20a continuous charger, not the usual 'peak' ratings that are quoted.

 

 

Thanks Allan,

 

Yes, I had looked at the Victron range. But without an "S" signal cable I would lose starter battery charging, I believe. I wonder if that matters though? I have solar and that charges the starter battery a bit. We don't leave the van sitting for weeks on end - I take it out at least once a week, if only to turn the engine and spin the wheels.

 

Are there any other disadvantages to missing an "S" signal?

[Alanb]

Davie,

 

As far as I can deduce, the "S" signal has only two functions which are to operate the mains charge relay for B1, (lower RH corner of the DS520 PCB) and to trigger the mains connected indication on the display unit.

 

A possible workaround would be to use a small voltage/charge monitoring relay to monitor B2 voltage and connect 12V+ to the DS520 "S" input when B2 voltage > 13.2V, and simulated D+ is low. Not so simple.

 

Another possible alternative would be to use a separate small charger to refresh the starter battery.

 

There are obviously other ways to check that the EHU input is live.

 

May I suggest that if you have not fully committed to the Schaudt WA unit, try increasing the cable sizes as far as practicable and perhaps add a larger split charge relay, then review the situation.

 

When you take your vehicle out for a short trip, do go far enough for the engine and exhaust to warm up.

 

Alan

 

 

[aandncaravan]

DavieR - 2018-11-21 9:28 AM

 

aandncaravan - 2018-11-21 8:45 AM

 

Maximising everything is good, but if it was me I wouldn't be spending money on a CB520, it isn't the fastest charger or the best for long term float charging.

 

If you want real value for money, it is hard to beat the Victron charger range, the 20amp version : Blue Smart IP22 Battery Charger 12V/20A/230V is a 20a continuous charger, not the usual 'peak' ratings that are quoted.

 

 

Thanks Allan,

 

Yes, I had looked at the Victron range. But without an "S" signal cable I would lose starter battery charging, I believe. I wonder if that matters though? I have solar and that charges the starter battery a bit. We don't leave the van sitting for weeks on end - I take it out at least once a week, if only to turn the engine and spin the wheels.

 

Are there any other disadvantages to missing an "S" signal?

 

 

DaveR, Alanb and you are correct that in it's usual form the WA unit effectively breaks the internal connection between the CBE DSxxx unit and the Starter battery when the Alternator stops. This doesn't matter on the Hymer/Schaudt equipped vehicles because Starter battery charging is carried out via the Fridge feed cable as is the 'Voltage' reading of the Starter battery.

 

 

But that is what the WA 'Bypass' switch is for as it bypasses the internal 'break' and allows a low current connection from the CBE DSxxx back to the Starter battery so the Starter battery can"be 'low current(5a)" charged as well as pick up the Starter battery voltage.

 

Never used this feature, so no practical experience of it, but the WA121545 manual says :

 

"8.4.4 Setting the ”Bypass” switch

The ”Bypass” sliding switch enables and disables a connection between the starter battery input and the EBL / leisure area battery output on the booster.

Y This connection is established internally and has a limited current. When this switch is in the ”On” position, there a connection between the starter battery and the booster output (to which about 5 A can be applied) as soon as the engine is turned off (so the D+ signal is no longer being applied).

F This connection provides mains recharging of the starter battery when the vehicle engine is switched off and a 230 V mains supply is available (made available to its starter battery connector from an EBL with STDBUS for example with bypassing of the cut-off relay).

F Measuring the starter battery voltage when the vehicle engine is turned off and the bypass is established is also possible using the electroblock to assess its condition".

 

 

Have a read of the manual and see if it's what you require?

We don't support the CBE kit so I am definitely not an expert on the CBE.

.

 

[DavieR]

Thanks again everyone who has posted. I've reread this thread a couple of times tonight and want to thank Allan and Alanb especially for their their assistance and their patience. I'm obviously a slow learner but I'm getting there.

 

I'm going to hold fire on the Schault WA 121545 booster (the cheapest I can find is €380 and that probably does breach my "value for money" threshold!). Having now discovered how to thread the heavy cables down to the distribution box, that will be the next job, plus fit a heavy duty relay. At that stage I will reassess. Hopefully I will have the same success as arthur49.

 

Tomorrow, I should have all the connection bits I need so I will put the van back together, fit the battery monitor and make sure it all works.

 

I have two email replies today, one from CBE and the other from Schaudt.

 

CBE have confirmed that the DS520AN-AN distribution box and the PC380 control panel are compatible, which is good but still leaves me with the unexplained +ve 3 amps when no charging is taking place.

 

Udo Lang from Schaudt confirmed that the WA121xxx units will work fine with the CBE box as shown in the wiring diagrams.

 

Dave

[DavieR]

All the new heavier cables are now connected, plus fuses, with the leisure batteries correctly linked. A new leisure battery monitor installed too. Also, the solar regulator has been replaced and the new one installed next to the distribution box. And thankfully, it's all working ok.

 

I have solved the mystery of my false +3 amps reading at night. I set the CBE monitor amps to match the new battery monitor (minus 3 amps from the monitor reading) and moved the mains charger positive cable from +B2 to +OUT. The latter correcting the erroneous readings when on EHU.

 

Next, will be heavier cables to the distribution box, plus a new split relay. Can anyone recommend a specific split relay? I believe a 100amp with 5 or 6mm studs is what I need, but one that requires minimal power to make the switch, so as not to overload the CBE simulated +D.

 

Thanks

[Alanb]

Davie,

 

You must have been a busy beaver of late.

 

As regards the phantom 3A, I was about to suggest that you adjusted the CBE current indication to read -0.5A with nothing else switched on. Congratulations.

 

As regards the new split charge r.elay, I do not think that you will be overloading the simulated D+ on the DS520AN, which is fused at 3A. The Tyco PCB which I think is used to control the simulated D+ output is rated at 2A at 24V DC possibly more at 12V DC,. The power for this output is obtained by tapping into an ACC+ circuit on the base vehicle.

A suitable higher rated split charge relay such as the Durite 0-727-18, or the cheaper equivalent Cargo 160720 will take about 0.3A coil current at 12V (Ducato spec.), and proportionately more at 14V.

 

Alan

[Alanb]

May I add another similar relay to the list, namely a Ripaults 2136/200.

 

I have one reservation about these relays. That is that the the Ripaults version at least is not fitted with either diode, or resistor across the coil, which helps to suppress sparking on the controlling contacts when the relay is de-energised. This may be to ensure a rapid release of the relay when breaking 100A DC, and so reduce erosion at its own contacts.

 

In the CBE system the simulated D+ is controlled via a PCB mounted relay, which we do not want to damage. A split charge relay will not normally be breaking much if any current, because it is released as the alternator output decays. It would therefore seem to be a good idea to include a diode across the coil, to help preserve the simulated D+ control relay. The diode would need to be connected with its positive end towards the relay terminal 86, that is the simulated D+ side. When choosing the diode I would go for 3A rated type, for reasons of physical strength. The reverse voltage rating (PIV) should be several hundred volts to allow a large margin of safety. As regards mounting the diode, the minimum would be to sleeve the diode wires and crimp it across the relay coil terminations.

 

A possible alternative would be to use the fridge 12V supply to energise the additional relay, but this is also PCB mounted.

 

Perhaps I am being over cautious? Comments and suggestions appreciated.

 

 

Alan

[plwsm2000]

Alanb - 2018-11-24 10:35 AM

 

May I add another similar relay to the list, namely a Ripaults 2136/200.

 

I have one reservation about these relays. That is that the the Ripaults version at least is not fitted with either diode, or resistor across the coil, which helps to suppress sparking on the controlling contacts when the relay is de-energised. This may be to ensure a rapid release of the relay when breaking 100A DC, and so reduce erosion at its own contacts.

 

In the CBE system the simulated D+ is controlled via a PCB mounted relay, which we do not want to damage. A split charge relay will not normally be breaking much if any current, because it is released as the alternator output decays. It would therefore seem to be a good idea to include a diode across the coil, to help preserve the simulated D+ control relay. The diode would need to be connected with its positive end towards the relay terminal 86, that is the simulated D+ side. When choosing the diode I would go for 3A rated type, for reasons of physical strength. The reverse voltage rating (PIV) should be several hundred volts to allow a large margin of safety. As regards mounting the diode, the minimum would be to sleeve the diode wires and crimp it across the relay coil terminations.

 

A possible alternative would be to use the fridge 12V supply to energise the additional relay, but this is also PCB mounted.

 

Perhaps I am being over cautious? Comments and suggestions appreciated.

 

 

Alan

Alan,

As you rightly point out, a single rectifier diode across the relay coil will slow down its opening time. If you are really concerned about this, you could use a zener and a rectifier diode in series that will allow the relay to open as fast as possible AND protect the driving circuit from over voltage. A MOV or TVS diode would also work.

 

[arthur49]

Alan/Phil

 

Interesting. I think I follow your logic ....... I am an interested amateur, so bear with me. Our new van which we don't get until April has CBE electricals, so:

 

1. what is simulated D+? Is it generated by the internal electronics when the engine is running rather than the D+ itself direct from alternator?

 

2. The coil terminals are 85 and 86 and I get what you're suggesting, and why. Could you attach a link to suitable diodes/rectifiers?

 

 

[Alanb]

arthur49 - 2018-11-24 6:17 PM

 

Alan/Phil

 

Interesting. I think I follow your logic ....... I am an interested amateur, so bear with me. Our new van which we don't get until April has CBE electricals, so:

 

1. what is simulated D+? Is it generated by the internal electronics when the engine is running rather than the D+ itself direct from alternator?

 

2. The coil terminals are 85 and 86 and I get what you're suggesting, and why. Could you attach a link to suitable diodes/rectifiers?

 

 

Arthur,

 

In answer to your first point, the CBE system does not make any connection to the alternator field terminal, commonly called D+. Instead a tap is taken from an ACC+ point, and connected to the CBE distribution board DS320xx, DS520xx, etc. I believe that the voltage is monitored on the distribution board itself, as there are sufficient electronics on the board to carry out this task. When the vehicle system voltage reaches about 13.2V??, indicating that the alternator is charging, a small relay is operated. This relay connects the ACC+ supply to operate the integral split charge and fridge relays. The same supply is also made available to operate external devices e.g. electric step, sattellite dish. There has been a suggestion that the fuse also supplies the split charge and fridge relays, but from memory I don't think that the handbook says that.

 

As regards your second point, I do not see any problem with an additional (100A) split charge being slightly slow to release. Therefore the simple diode approach, (which is quite commonly fitted internally on automotive relays) should suffice as an insurance against any erosion of the simulated D+ relay contacts. A 1N504 diode, readily available on Ebay, would be adequate electrically, and have sufficient physical strength.

 

Alan

[arthur49]

Thank you Alan

[Alanb]

aandncaravan - 2018-11-21 10:44 AM

 

.......................................................................................................................................................................

 

DaveR, Alanb and you are correct that in it's usual form the WA unit effectively breaks the internal connection between the CBE DSxxx unit and the Starter battery when the Alternator stops. This doesn't matter on the Hymer/Schaudt equipped vehicles because Starter battery charging is carried out via the Fridge feed cable as is the 'Voltage' reading of the Starter battery.

 

 

But that is what the WA 'Bypass' switch is for as it bypasses the internal 'break' and allows a low current connection from the CBE DSxxx back to the Starter battery so the Starter battery can"be 'low current(5a)" charged as well as pick up the Starter battery voltage.

 

Never used this feature, so no practical experience of it, but the WA121545 manual says :

 

"8.4.4 Setting the ”Bypass” switch

The ”Bypass” sliding switch enables and disables a connection between the starter battery input and the EBL / leisure area battery output on the booster.

Y This connection is established internally and has a limited current. When this switch is in the ”On” position, there a connection between the starter battery and the booster output (to which about 5 A can be applied) as soon as the engine is turned off (so the D+ signal is no longer being applied).

F This connection provides mains recharging of the starter battery when the vehicle engine is switched off and a 230 V mains supply is available (made available to its starter battery connector from an EBL with STDBUS for example with bypassing of the cut-off relay).

F Measuring the starter battery voltage when the vehicle engine is turned off and the bypass is established is also possible using the electroblock to assess its condition".

 

 

Have a read of the manual and see if it's what you require?

We don't support the CBE kit so I am definitely not an expert on the CBE.

.

 

Allan,

 

Sorry for the delayed response. I have looked at the Schaudt WA121545 (B2B unit), as suggested.

 

As far as I can ascertain, this unit would be compatible with CBE DSxxx xx distribution boards when the unit is effectively connected between the starter battery and the CBE B1 terminal, and the bypass feature is enabled. However the WA121545 which comes with battery sensing connections, is as Davie has stated expensive. I still think that if wishing to add a B2B to a CBE equipped vehicle, the most effective route would be to separate out the fridge supply via a small changeover relay, and use a new second cable from the starter battery for the B2B. The new fridge relay could be operated from either simulated D+, or (Why did I not think of it earlier?) from the original fridge supply. Some reduction of fuse ratings would also be needed.

 

Alan

[aandncaravan]

Schaudt Wa12145.

The Schaudt WA12145 at 300 euros (£270) is way cheaper than the £379 50amp Sterling B2B, yet despite it's higher price the Sterling is not full featured and not designed for a motorhome.

The Sterling B2B instructions don't even mention the relatively simple Sargent ECxxx Power Controllers let alone document the best way to wire them up to retain full functionality.

 

The Sterling docs assume the setup is similar to that on board a boat, which are actually very, very different.

 

The Schaudt unit is designed by the biggest specialist Motorhome electronics manufacturer in the world whose kit is installed in more motorhomes world wide than any other. So not surprising it not only works better, is cheaper, and more efficient.

 

The Schaudt unit works in harmony with the existing kit, no need to disable any existing hardware to make it work, unlike almost all the Sterling, CTEK, etc B2B units.

 

 

The Schaudt range start at about £89 for the lower power Alternator voltage boosters, so puts the other units to shame when it comes to value for money, yet most of the professionals either don't know they exist or don't understand the Motorhome in built electronics to be able to fit them.

 

A real shame as most people who get A B2B fitted professionally, usually end up with a compromised system and a bigger bill than it needs to be, because not only is the kit more expensive, but installation is more complex than the Schaudt option.

Those that doubt that, should see the documentation which states things like,

" Multiple units can be used: for example, if you have a 60A alternator and 3 battery banks (engine, domestic and bow thruster).........".

Also

"No direct connections to the standard engine alternator: or to the OUTBOARD engine".

 

 

 

I think that rather than playing with relays, moving to Welteds solution of running the Fridge off 230v on the move is a much better idea, but there you go.

In it's simplest form all that is needed is a 400w Inverter with a 13amp socket to power the Fridge. Just pull the Fridge 13a plug from it's existing 13a 'EHU' socket and plug it into the Inverter output whenever the engine is started.

What could be simpler?

 

The Fridge then uses it's internal thermostat, which often isn't part of the 12v circuit so also works much better, cools more effectively and using less power overall because the thermostat ensures it is turned off around 60% of the time, rather than the usual 12v continuous power draw.

 

With Fridge Freezers getting bigger and draining close to 20 amps, they are always going to place a major load on the 12v circuits which just have not kept pace. The original '12v from Alternator' system has not advanced much at all from when it first introduced in the 1980's. Then they drew around 9amps. permanently on 12v for the typical 3 hour journey's that people made at the time. Driving for 3 hours at a time was pretty much all most could manage in a Talbot of the period.

That is very different to the 10 hour drives down through France drawing a constant 19 amps. Not surprising more and more Fridge 12v circuits are burning out.

 

It is time something much better was introduced by the manufacturers. Weldteds solution is an amazing step forward, IMO.

 

[DavieR]

Alanb - 2018-11-23 9:24 PM

 

As regards the phantom 3A, I was about to suggest that you adjusted the CBE current indication to read -0.5A with nothing else switched on. Congratulations.

 

Alan

 

The adjustment on its own wasn't the total answer though. After adjustment, if I put in the mains charger, I would see a (from memory) -0.7 amps. But moving the mains +ve from +B2 to +OUT gave me a true reading, checked with the new battery monitor. I'm glad to have it sorted!

[aandncaravan]

arthur49 - 2018-11-24 6:17 PM

 

Interesting. I think I follow your logic ....... I am an interested amateur, so bear with me. Our new van which we don't get until April has CBE electricals, so:

 

1. what is simulated D+? Is it generated by the internal electronics when the engine is running rather than the D+ itself direct from alternator?

 

2. The coil terminals are 85 and 86 and I get what you're suggesting, and why. Could you attach a link to suitable diodes/rectifiers?

 

 

 

Arthur, If you are asking the question because you want to find an easy way to pick up D+, then on some of the DSxxx units we have worked on, the male spade terminal FA4 usually provides a D+ trigger voltage when the PCB also triggers Split charging, Fridge, etc.

 

On the limited DSxxx units we have performed surgery on, FA4 has been about 2 inches above the B1+ terminal and just above FA5, but this may not be the location on all DSxxx units

 

 

The Fridge relay can usually be found located adjacent to spades FA2 and FA3 and can be fairly easily located by following the track between FA2 and it's supply Fridge fuse.

Note that the fuse is on the INPUT side to the Fridge relay not the output side as Alanb seems to think.

 

If you desolder the trigger for this relay so it is permanently open, you can pick up the relay Fridge 12v input (directly from the Fuse) on spade FA2, then run the supply through the new relay and onto FA3 to supply J5, 6 pin socket for the Fridge to bypass the original weedy Fridge relay.

 

HOWEVER, and this is the issue with the CBE system, or at least the ones we have worked on like the DS300 ; Because the Fuse is fed directly from 'the habitation battery', not the Starter battery, there is little benefit.

 

So taking the power supply from the Fuse won't give any real benefit because it is still the habitation battery that is supplying the load (and therefore creating the voltage drop) when the ideal is for it to be picked up from the Alternator.

 

The solution to poor charging on the CBE systems, is as simple as removing the Fridge fuse, taking a feed from the Alternator and plugging it via a temporary male Spade into the lower (none live) Fuse connector. This results in the Fridge relay being fed from the Alternator, not the habitation battery connection.

 

That is obviously not a solution because it isn't sound, safe, nice or pretty. But it shows what you need to do to the PCB, by breaking the habitation battery feed to the Fridge fuse and applying Alternator power to the fuse input (top) side.

 

 

While running bigger cables to B1+ and B2+ will obviously help, the key is to remove the Fridge load from all wiring except directly from the Alternator it is physically running from, via a single cable run.

 

It sounds like only a minor difference but the end result is huge, as seen by the 13.7v charging voltages shown in other threads.

 

Obviously adding the extra charging load of another battery, or worse still higher current draw batteries like AGM or, god fobid, Lithium, will lead to further load and the resulting Voltage drop making charging even less effective. It can even result in voltages so low the battery doesn't charge fully.

So if any 'experts' tell you that adding more batteries doesn't make any difference to the charging you can take what they say with a pinch of salt.

 

Only the Schaudt designed systems take a Fridge feed directly from the Starter battery and that is why they have close on 14.4v charging at the habitation battery, even with the Fridge running off 12v.

 

 

[arthur49]

Thank you Allan. I've no idea how well my next CBE equipped van will charge whilst driving so at the moment I'm just in a learning stage in case I need to improve charging.

Useful and interesting Allan thank you

[DavieR]

I'm not sure what is the best time to take charging voltage measurements but these were directly after starting a cold engine on tick over.

 

Starter Battery - 14.27 -14.30v

Leisure Batteries (fridge off) - 14.03 - 14.11v

Leisure Batteries (fridge on) - 13.82v

All the above taken with my cheap multi-meter.

 

My new battery monitor reads -

Leisure Batteries (fridge off) - 14.22v

Leisure Batteries (fridge on) - 13.97v

Which suggests my cheap multi-meter is possibly under reading a bit?

 

I have 6mmsq cables from the starter battery to PCB and back to the leisure batteries. I was planning on replacing that with 16mmsq, or could I run the thicker cable parallel with the 6mmsq? What level of improvement should I expect? Thanks.