Battery to Battery charger

[Raul]

Feedback loops are a common feature of electronic circuits, and their analysis is well understood. Whole books have been written about them. You can't design a decent amplifier without accounting for feedback loops.

In this case, the split charge relay and the B2B are connected in parallel. The feedback path is an extremely low resistance - the split charge relay and wiring - so the voltage drop across it will be practically zero. The output of the B2B will be at the same voltage as the input. In other words, the B2B will do practically nothing.

And this is how not to do it. The B2B is there to limit the charge and protect the alternator. The feed via split relay is low resistance and lots of charge unregulated. The voltage will stay the same until CV constant voltage is reached at the battery. At this point the B2B will regulate and throttle back the amps. The split will just carry on to whatever regulation is in the alternator. A B2B in parallel with other regulated chargers or other B2B’s if perfectly fine, but not with a split relay, that’s not regulated by nothing but the alternator, which is only good for the starter and lead in habitation.

 

[Al n Val]

So i'm getting a little confused with some of the replies, basically if i fit the Victron unit directly between my leisure and cab batteries, running + & - cables between each so,

cab battery + to victron +, cab battery - to victron - (input)

and then the same from the victron,

victron + to hab battery +, then victron - to hab battery - (output)

are we saying this is wrong and will not work correctly, if not why not and what will the consequences be if I leave all existing wiring and fuses exactly as they are

thanks everyone so far

Al

 

[autorouter]

If there was no other wiring to think about, then wiring direct between the batteries would work fine. However there is probably another bit of wiring already present. It's the relay that connects the starter and leisure batteries when the engine is running, called the split charge relay. If not dealt with, it will be a direct connection across the input and output of the B2B. Nothing bad will happen, but the B2B will do nothing.

If the relay is separate from the distribution box, it's usually quite easy to disable it. If it's built into the distribution box, it's not so easy. There are various workarounds

 

[Al n Val]

If there was no other wiring to think about, then wiring direct between the batteries would work fine. However there is probably another bit of wiring already present. It's the relay that connects the starter and leisure batteries when the engine is running, called the split charge relay. If not dealt with, it will be a direct connection across the input and output of the B2B. Nothing bad will happen, but the B2B will do nothing.

If the relay is separate from the distribution box, it's usually quite easy to disable it. If it's built into the distribution box, it's not so easy. There are various workarounds

so lets assume its built in to the Sargent unit, what are the workarounds and what will the workarounds do/cause to other things such as the fridge and step and maybe something else.

if its external to the Sargent unit how do we disable the split charge relay and what might that do/cause to those same items

thanks Al

 

[Diabalo]

I understand your confusion as I am in the same position, as autorouter states you need to isolate the split charging link which was confirmed to me by Sargent Electrical when I spoke to them. I haven't done mine yet but intend to fit a normally closed relay on the feed to the Hab battery, this will open when the engine starts to cut the feed and stay closed when on EHU/solar so that works the same. I have the older EC500 unit so it may be different.

I'm not in any way an electrical engineer so I could be missing something relevant.

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[Insider]

I have a Forte and fitted a Sterling B2B charger recently. To stop the alternator competting witht the B2B I fitted a relay to turn off the power coming into my EC400 when the van is running. This relay is activated by +12V coming from the engine. I used the Sargent circuit diagram to identify this and got the diagram below fro another forum.

I know this is not exactly what you're looking for as you are a much later version of the Sargent kit and using Victron rather than Sterling but the principle should be the same


If I have waded in and added more confusion - apologies

 

[Al n Val]

I have it now in very good hands, Mick at SAP is going to be fitting it and making improvements to my inverter installation along with Air suspension

Bit of a turnaround i know but i'd rather be safe than sorry

thanks everyone for their input, Al

 

[Lenny HB]

I have it now in very good hands, Mick at SAP is going to be fitting it and making improvements to my inverter installation along with Air suspension

Bit of a turnaround i know but i'd rather be safe than sorry

thanks everyone for their input, Al

Are you having full 4C air?

 

[Al n Val]

Are you having full 4C air?

hi Lenny

just the back 2 axels mate, its only because I want to lift it incase I have to back onto a raised pitch, since i had the chassis mounted bike/scooter rack fitted last year the rack itself grounded twice whilst getting onto pitches. Its not something i've experienced before tbh so want to sort it for this year before we set off again travelling.

I actually modified the rear of the rack whilst in Murcia and fitted 2 x 80mm wheels at either side of the rack so 4 in total, these now ground first if anything does so it's ok but just fancied the idea of air.

Also Mick fitted the EP levelling system and at the same time fitted the front comfort springs which tbh transformed and raised the front end, literally its the best £700 i think i've spent on the van tbh

Have you got air Lenny and whats your thoughts on it as its something i've never experienced tbh?

Al

 

[Lenny HB]

Mick originally fitted VB full air to my van, but there wasn't enough ground clearance even after fitting additional spacers. Mick took it off & gave me a full refund, a great guy.
I now have Goldsmittch full air, had it fitted in Belgium, a lot cheaper than Travelworld. Having had full air I don't think I would want a van without it.

Go on treat yourself.

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[Al n Val]

Mick originally fitted VB full air to my van, but there wasn't enough ground clearance even after fitting additional spacers. Mick took it off & gave me a full refund, a great guy.
I now have Goldsmittch full air, had it fitted in Belgium, a lot cheaper than Travelworld. Having had full air I don't think I would want a van without it.

Go on treat yourself.

OOHH!!

how much lift did you get with VB Lenny and may i ask what sort of cost are we talking for both systems if you don't mind me asking, pm if you'd rather

Al

 

[Diabalo]

I have it now in very good hands, Mick at SAP is going to be fitting it and making improvements to my inverter installation along with Air suspension

Bit of a turnaround i know but i'd rather be safe than sorry

thanks everyone for their input, Al

Sounds the sensible thing to do, if possible can you let us know what was done on the B2B side of things.

 

[Lenny HB]

OOHH!!

how much lift did you get with VB Lenny and may i ask what sort of cost are we talking for both systems if you don't mind me asking, pm if you'd rather

Al

It was a problem with the way the Al-Ko was set up the torsion bars under higher tension than the standard set up, Mick also found the problem on some Burstners as well. The result was the rear sat too low and on twisty roads the rear tyres would ground on the wheel arches also lost ground clearance.
The height is only adjustable a certain amount on the VB with the addition of spacers where as the Goldschmitt mounts on a quadrant with a large adjustment range.

With the full air in driving mode the van rides at the standard height but reguardless of load the ride height is constant.

Cost of VB £6,600, Goldschmitt £7,150 (Travelworld wanted £8,750).

 

[Al n Val]

It was a problem with the way the Al-Ko was set up the torsion bars under higher tension than the standard set up, Mick also found the problem on some Burstners as well. The result was the rear sat too low and on twisty roads the rear tyres would ground on the wheel arches also lost ground clearance.
The height is only adjustable a certain amount on the VB with the addition of spacers where as the Goldschmitt mounts on a quadrant with a large adjustment range.

With the full air in driving mode the van rides at the standard height but reguardless of load the ride height is constant.

Cost of VB £6,600, Goldschmitt £7,150 (Travelworld wanted £8,750).

hi Lenny

its not out of the way tbh, but and its a BIG but, i've had this motorhome 3 years this coming Sept and getting itchy feet for an A class, so far everything i've fitted or had fitted on this one can be removed and fitted to the next Alko chassis'd van. So I may have to give this a bit more thought and hang on a little while, after all Sept 1st isn't too far away is it

thanks for the info btw, Al

 

[Lenny HB]

hi Lenny

its not out of the way tbh, but and its a BIG but, i've had this motorhome 3 years this coming Sept and getting itchy feet for an A class, so far everything i've fitted or had fitted on this one can be removed and fitted to the next Alko chassis'd van. So I may have to give this a bit more thought and hang on a little while, after all Sept 1st isn't too far away is it

thanks for the info btw, Al

Even the air suspension can be swapped if on the same chassis.
You won't regret going to an A Class, nicer environment to live in & easier to drive.

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[Al n Val]

Even the air suspension can be swapped if on the same chassis.
You won't regret going to an A Class, nicer environment to live in & easier to drive.

yes thats very true Lenny

I agree the inside cab area really does seem a lot more spacious, that and its a lot easier to wash at the front lol.

Honestly cleaning underneath the over head cab on my C Class is bloody awful, I hate doing it with a passion, do you know of a A Class with long seats in the dining area where we can both get our feet up, I wouldn't mind a look at the Cathago Liner for 2 but its a rear lounge which looks lovely but an over cab bed which we don't want

 

[Lenny HB]

yes thats very true Lenny

I agree the inside cab area really does seem a lot more spacious, that and its a lot easier to wash at the front lol.

Honestly cleaning underneath the over head cab on my C Class is bloody awful, I hate doing it with a passion, do you know of a A Class with long seats in the dining area where we can both get our feet up, I wouldn't mind a look at the Cathago Liner for 2 but its a rear lounge which looks lovely but an over cab bed which we don't want

The Germans dropped side sofas years ago, the liner for two needs to be on the Iveco chassis which makes it a lot more expensive, Fiat chassis has naff all payload, I don't like rear lounges either.

 

[Trout bum]

I have it now in very good hands, Mick at SAP is going to be fitting it and making improvements to my inverter installation along with Air suspension

Bit of a turnaround i know but i'd rather be safe than sorry

thanks everyone for their input, Al

May I ask where SAP are based , I'm getting confused now about the wiring

 

[Lenny HB]

May I ask where SAP are based , I'm getting confused now about the wiring

Just north of Doncaster.

 

[Bustup15]

yes thats very true Lenny

I agree the inside cab area really does seem a lot more spacious, that and its a lot easier to wash at the front lol.

Honestly cleaning underneath the over head cab on my C Class is bloody awful, I hate doing it with a passion, do you know of a A Class with long seats in the dining area where we can both get our feet up, I wouldn't mind a look at the Cathago Liner for 2 but its a rear lounge which looks lovely but an over cab bed which we don't want

Have you considered a Dethleffs Alpa I-7820? Massive rear lounge and drop down bed at front to relatively low access level?

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[Al n Val]

Have you considered a Dethleffs Alpa I-7820? Massive rear lounge and drop down bed at front to relatively low access level?

View attachment 469869View attachment 469870View attachment 469871View attachment 469872

hi

that looks very much similar to the Cathargo Liner for 2 layout, i’ve not done a show yet but hoping to see different vans and layouts at Peterborough in June

i’m hoping after seeing a layout such as that will help me make my mind up once and for all, we like our layout very much tbh but always open to see anything else that might make us choose differently

I was considering having air suspension fitted to the Comanche but holding off now for a while until I decide what to do

cheers and thanks for the suggestion

Al

 

[Al n Val]

May I ask where SAP are based , I'm getting confused now about the wiring

as Lenny says SAP are here

Broken Link Removed

i’m not confused as such regards the wiring but after speaking to Mick there’s quite a bit more involved on my particular vehicle, the dc to dc charger is very easy but if it’s just wired as the video posted, then other things happen.

Relays are needed to stop one charger working against the other

Similarly now i’ve fitted an inverter, if left as is, the fridge, truma heating and the charger. once recognising there’s a 240v supply attached, will all go over to 240v (as in EHU) and drain the batteries rapidly

The Sargent split charger for instance will automatically want to charge the batteries so i’ve create a loop where the inverter is on drawing off the batteries and so is the sargent charger whilst it’s trying to charge them.

Also same for the fridge and Truma, so unless i have something fitted within the electrical system i’ll need to make sure that all those 3 items are turned off or on to gas whilst the inverter is on

It’s not so simple as I thought and has been made out

Al

 

[TCG]

as Lenny says SAP are here

Broken Link Removed

i’m not confused as such regards the wiring but after speaking to Mick there’s quite a bit more involved on my particular vehicle, the dc to dc charger is very easy but if it’s just wired as the video posted, then other things happen.

Relays are needed to stop one charger working against the other

Similarly now i’ve fitted an inverter, if left as is, the fridge, truma heating and the charger. once recognising there’s a 240v supply attached, will all go over to 240v (as in EHU) and drain the batteries rapidly

The Sargent split charger for instance will automatically want to charge the batteries so i’ve create a loop where the inverter is on drawing off the batteries and so is the sargent charger whilst it’s trying to charge them.

Also same for the fridge and Truma, so unless i have something fitted within the electrical system i’ll need to make sure that all those 3 items are turned off or on to gas whilst the inverter is on

It’s not so simple as I thought and has been made out

Al

Surely if you are not on EHU and therefore using inverter. you would have manually selected gas for both the fridge and truma. that what we do and never had an issue.
with regards to the B2B. the 20amp fuse on the floor behind drivers seat was removed

 

[Lenny HB]

as Lenny says SAP are here

Broken Link Removed

i’m not confused as such regards the wiring but after speaking to Mick there’s quite a bit more involved on my particular vehicle, the dc to dc charger is very easy but if it’s just wired as the video posted, then other things happen.

Relays are needed to stop one charger working against the other

Similarly now i’ve fitted an inverter, if left as is, the fridge, truma heating and the charger. once recognising there’s a 240v supply attached, will all go over to 240v (as in EHU) and drain the batteries rapidly

The Sargent split charger for instance will automatically want to charge the batteries so i’ve create a loop where the inverter is on drawing off the batteries and so is the sargent charger whilst it’s trying to charge them.

Also same for the fridge and Truma, so unless i have something fitted within the electrical system i’ll need to make sure that all those 3 items are turned off or on to gas whilst the inverter is on

It’s not so simple as I thought and has been made out

Al

You need to fit a relay or contactor that changes over just the mains sockets leaving the freidge, charger etc., so they only operate on mains when on EHU.

 

[Al n Val]

Surely if you are not on EHU and therefore using inverter. you would have manually selected gas for both the fridge and truma. that what we do and never had an issue.
with regards to the B2B. the 20amp fuse on the floor behind drivers seat was removed

yes that’s correct but what if we forget to do this, that was always the plan tbh but the missus doesn’t do plans

The other option is to use the socket on the inverter only but that’s a bit off a faff tbh having a trailing lead all over the van, i’m a bit of a neat freak and can’t do with wires all over the place

Having it done correctly is where i’m leaning towards if i’m honest

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[Al n Val]

You need to fit a relay or contactor that changes over just the mains sockets leaving the freidge, charger etc., so they only operate on mains when on EHU.

yes that’s what Mick said Lenny, do you have a link for that particular relay what’s needed

thanks Al

 

[Tombola]

So how do we know if the b2b and VSR are cancelling each other out on a system lime this, would the b2b not show a charge avia the BMV ?

 

[Tombola]

yes that’s what Mick said Lenny, do you have a link for that particular relay what’s needed

thanks Al

Something like this but not wired direct into the EHU entrance for the whole van which would try and power all the van, but into the fused 230v sockets run only

Amazon product ASIN B073PRZGN2

 

[Al n Val]

Something like this but not wired direct into the EHU entrance for the whole van which would try and power all the van, but into the fused 230v sockets run only

Amazon product ASIN B073PRZGN2

i’d need to know exactly what to disconnect and reconnect before attempting this, i’m an ex electrician myself but not done any work on motorhomes and struggle with getting into tight areas due to arthritis so i’d not attempt myself tbh.

If I had someone behind me telling me what to do i’d still struggle as my shoulders have seized up lol

 

[Lenny HB]

yes that’s what Mick said Lenny, do you have a link for that particular relay what’s needed

thanks Al

Sorry don't have a link anymore. I used a 30 amp double pole changeover relay. I used a 240v coil relay so it changes over when on EHU as we very seldom use EHU and it saves battery power. If you use mains a lot you may want to use a relay with a 12v coil.
Edit:
In the second instant probably better to still use a 240v relay switched by the inverter output as with a 12v one you would have to switch it when turning the inverter on, depending on your installation could be awkward to do.

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