steve hill Posted February 13, 2021 Share Posted February 13, 2021 We have a Ducato Roller Team Camper 707 that cross charges (once the caravan side has enough charge) to the engine battery when we are plugged into mains. However, at the same time when we are plugged in we also have a Sterling B2B that the kicks in sometimes when it realizes the engine battery now has enough charge to cross back to the caravan battery, oops? Does anyone else have this problem. It does all settle when both batteries reach full charge and go to " float level". Neither can be easily switched off and both work fine separately. But I am worried that the loop and high charge rate of the B2B will cause the Roller Team charger to run flat out and overheat if it takes a long time to reach float level. Link to comment Share on other sites More sharing options...
Keithl Posted February 13, 2021 Share Posted February 13, 2021 Steve, I thought a B2B should be wired with an ignition D+ signal so it can only charge the leisure battery when the engine is actually running? Sounds like yours may be missing a vital link? Keith. Link to comment Share on other sites More sharing options...
mikefitz Posted February 13, 2021 Share Posted February 13, 2021 If you have the Sterling Pro Ultra 30 amp units there are options that control the activation. Option 2 uses the voltage increase above the threshold and ignition on signal to enable charging. Page 6 in the instruction manual gives details. Ignition live may be accessible at the vans electronic control panel or by using a piggy back fuse at position of any of the 'key on' fuses in the dashboard fuse box, F37 , F35, F31. I doubt that the existing mains charger will 'keep up' with the 30 amps that the Sterling is pulling from the starter battery, ( in the unlikely event of reaching float voltage this is still above the Sterling switch on value). Failure of the mains charger, as you suspect, may be a result of the constant cycling of the Sterling unit. The problem you are having is a well known situation where battery to battery chargers are installed, and using ignition on signal, ( ignition on is easy to access on the Ducato, D+ (alternator charging) can also be used as a control signal but is not normally readily available), is common practice. Sterling instructions, ( I guess this is your unit) https://cdn.shopify.com/s/files/1/0658/7343/files/2017-06-29_BB1260_30_Ultra_InstructionsEng_GerV56.pdf?4184034073808288374 https://cdn.shopify.com/s/files/1/0658/7343/files/2019_GREEN_V69_Rev_Instructions.pdf?92 Mike Link to comment Share on other sites More sharing options...
steve hill Posted February 13, 2021 Author Share Posted February 13, 2021 Mine is a 1250, The B2B senses the voltage level at the engine battery which is the same point as the alternator ouput and the Roller Team mains charger are, if either is working it will output to the spare battery when the engine battery rises above 13V and drop when the spare achieves float level. I need the B2B only working when the engine runs. I cannot simply switch off the B2B its an install and forget type. There is no seperate line to tell the B2B its got the engine running, as far as I can see the diagram just shows the alternator going to the battery terminal. Link to comment Share on other sites More sharing options...
Keithl Posted February 13, 2021 Share Posted February 13, 2021 In that case you will have to install a D+ controlled relay (old fashioned split charge relay) in the feed to the B2B so it can only connect when the engine is running. Keith. Link to comment Share on other sites More sharing options...
Keithl Posted February 13, 2021 Share Posted February 13, 2021 Just found instructions for Sterling 1250 and agree with you, no ability to control via ignition circuit or D+ signal. https://cdn.shopify.com/s/files/1/0658/7343/files/12-12_install_eng_germ.pdf?480 Keith. Link to comment Share on other sites More sharing options...
mikefitz Posted February 13, 2021 Share Posted February 13, 2021 The Sterling 12/50 is an unusual choice for a van. At idle speed the 'spare current' will be 50 to 60 amps with full demand from the van circuits, however the temperature sensing of alternator will help with reliability. Since there is no control on that Sterling unit the simple option is to fit a power relay between the engine battery and the Sterling unit. Control the relay with ignition on voltage. A suitable relay, https://www.12voltplanet.co.uk/heavy-duty-relays.html A D+ signal could be used as an alternative, but is not always easy to find on a Fiat. Mike Link to comment Share on other sites More sharing options...
steve hill Posted February 14, 2021 Author Share Posted February 14, 2021 MMM ta for that. The Sterling 1250 was actually the regular B2B van people were using, at 50Amps it was more than good enough for most, it is however old. I think the relay is a good idea and cheap, but the fitting it, finding the "trigger", getting it through to the B2B, getting more heavy duty cables may not be worth the trouble. I don't need mains power often, we have diesel heating, gas for hot water, use the van often, dont use power on sites and free camp regularly, it was a while before I found the van charger was disconnected at the plug. We use the usual equipment and only have one good old school battery and 2 solar panels. Link to comment Share on other sites More sharing options...
Tracker Posted February 14, 2021 Share Posted February 14, 2021 I have no technical knowledge of these systems so forgive me for a very basic thought - but would a cheap and easily sourced and sited battery isolator type switch be sufficient to break a circuit where needed? Link to comment Share on other sites More sharing options...
Auditor Posted February 14, 2021 Share Posted February 14, 2021 Tracker - 2021-02-14 12:04 PM I have no technical knowledge of these systems so forgive me for a very basic thought - but would a cheap and easily sourced and sited battery isolator type switch be sufficient to break a circuit where needed? Quite correct. That is what I did, when I fitted a Sterling B2B. It doesn't have to be more complicated than this. Link to comment Share on other sites More sharing options...
steve hill Posted February 14, 2021 Author Share Posted February 14, 2021 Yes it would, but again it means more heavy duty cables ( which have be cut to fit and not really easy to change arround and get in place) and connections etc at a possible 50 amps you have to be carefull where it is sited and secured. I have a switch in Oz and they are often open on the connections, I would prefer to leave it but it may be a bad setup, hoping Sterling will advise. Thanks though! Link to comment Share on other sites More sharing options...
Alanb Posted February 14, 2021 Share Posted February 14, 2021 I note that the Steve has chosen to post the same query on another forum, in parallel with this one. On the popular CBE and Schaudt systems, charging of the starter battery when on EHU is via a relay contact, and reverse blocking diode, with current limited to about 2A by a thermistor. The relay coil is energised when the charger is energised. The charging of the starter battery, operates in parallel with the charging of the habitation battery, but due to the diode, maximum voltage is at least 0.4V lower than that of the habitation battery. When fitting a small B2B (20A), to operate in conjunction with with my CBE DS520 unit, I was anxious not to create loops around the existing circuitry. I therefore fitted a relay at the input to the B2B, to perform as that suggested above by Mike. I chose to operate the input relay from the CBE simulated D+, but a similar relay could also be operated from the supply to the 12V element of a 3 way fridge. As Steve's B2B lacks the facility for a D+ control (as did mine), he should take note of the recommendations to fit a relay at the B2B input On fitting a B2B, it is also necessary to disable the split charge relay, which will effectively become a short between the input and output of the B2B, when the relay is operated. Some B2B users choose to disable the split charge relay by disconnecting the coil circuit on the CBE or Schaudt etc. PCB. This results in a non standard unit. Not the best state, if emergency replacement is required. Given the small rating of my B2B, I did not want the major portion if its output to be consumed by the fridge. The solution was to fit a simulated D+ operated changeover relay for the fridge, at the B1 (starter battery) input to the CBE board, together with a new inline fridge fuse. This modification also preseved the starter battery charging and monitoring functions. The installation, although slightly complex, functions as expected with no problems observed. The wiring and connections, are designed to facilitate restoration of basic split charge relay operation, in the event of B2B failure. Alan Link to comment Share on other sites More sharing options...
Derek Uzzell Posted February 15, 2021 Share Posted February 15, 2021 Alanb - 2021-02-14 10:21 PM I note that the Steve has chosen to post the same query on another forum, in parallel with this one. https://www.fiatforum.com/ducato/485448-cross-charging-problem.html Link to comment Share on other sites More sharing options...
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