Split Charge relay - advice

Graeme · Feb 26, 2006

Hi all

Currently fitting a split charge relay and I have two queries:

1) What size of fuse would you put in the live feed from the existing
battery andin the feed to the live of the leisure battery? I've read 25Amp
but elsewhere 10 Amp.

2) Negative feed from the relay - is there any benefit in taking this back
to the leisure battery negative over a good chassis earth?

Graeme

Pieter Vroom · Feb 27, 2006

I am no car electrician but would have thought:
1) there is no need for two fuses, after all when the relay closes live from
car battery and live to aux. battery is one circuit. Size of fuse would
depend on the rating of the relay.

2) Don't quite get this. What negative feed from the relay? The only
"negative" would be the earth in the actuation part (if that is the right
word in English, sorry am Dutch) of relay (i.e. small current from the
alternator terminal that also controls the charge light of your dash), the
current that closes the relay to join positive terminals of battery
together. The aux battery obviously would need a good earth to charge.

Pieter

"Graeme" <[email protected]> wrote in message
news:[email protected]...
> Hi all
>
> Currently fitting a split charge relay and I have two queries:
>
> 1) What size of fuse would you put in the live feed from the existing
> battery andin the feed to the live of the leisure battery? I've read
> 25Amp
> but elsewhere 10 Amp.
>
> 2) Negative feed from the relay - is there any benefit in taking this back
> to the leisure battery negative over a good chassis earth?
>
> Graeme
>
>

Graeme · Feb 27, 2006

Hi Pieter
"Pieter Vroom" <[email protected]> wrote in message
news:[email protected]...
> I am no car electrician but would have thought:
> 1) there is no need for two fuses, after all when the relay closes live
from
> car battery and live to aux. battery is one circuit. Size of fuse would
> depend on the rating of the relay.

I'm using this as a guide:
http://www.kampenwagen.co.uk/split charge relay.htm

plus the printed instructions with the fancy relay I've bought - both
suggest a fuse to both positive terminals. The relay is rated at 25 Amps so
I'll use that size fuse.

>
> 2) Don't quite get this. What negative feed from the relay? The only
> "negative" would be the earth in the actuation part (if that is the right
> word in English, sorry am Dutch) of relay (i.e. small current from the
> alternator terminal that also controls the charge light of your dash), the
> current that closes the relay to join positive terminals of battery
> together. The aux battery obviously would need a good earth to charge.

The relay needs to be earthed to the chassis - I was just wondering if it
would be beneficial to run it back to the battery -ve terminal rathe rthan
faff around with yet another chassis earthing point.

Graeme

steve · Feb 27, 2006

Graeme wrote:

> I'm using this as a guide:
> http://www.kampenwagen.co.uk/split charge relay.htm

There's no point putting two fuses in, and I'd use a 12v MCB instead
personally. The fuses are in the same piece of wire, when the switch is
closed, and they aren't connected anywhere when the switch ISN'T closed,
so why two fuses ?

Also, don't use a 1N4001 across the relay - use at least a 1N4007, and
again, there isn't a right lot of point, its a nice touch, but the
starter motor will put out rather more inductive kickback than a poxy
bloody relay.

>
> The relay needs to be earthed to the chassis - I was just wondering if it
> would be beneficial to run it back to the battery -ve terminal rathe rthan
> faff around with yet another chassis earthing point.

No problem, if its easier to put it back to the battery, do it.

Graeme · Feb 28, 2006

Hi Steve

Thanks for that - I'll bung one fuse in for the time being and get a MCB
next time I get anything from Maplins or RS.

I was not going to be doing the diode bit as the beast is only going to be
powering a couple of internal LCD spotlights and a ciggy lighter fitting to
run laptop/shaver/whatever.

Trouble is it's too dang cold out there to do any meaningful work - oh for a
garage/big shed/101 with a cabin heater

)

Now I wonder if I could convince the SWMBO that a 101 is a necessary
purchase?

Graeme
"steve" <[email protected]> wrote in message
news:[email protected]...
> Graeme wrote:
>
> > I'm using this as a guide:
> > http://www.kampenwagen.co.uk/split charge relay.htm
>
>
> There's no point putting two fuses in, and I'd use a 12v MCB instead
> personally. The fuses are in the same piece of wire, when the switch is
> closed, and they aren't connected anywhere when the switch ISN'T closed,
> so why two fuses ?
>
> Also, don't use a 1N4001 across the relay - use at least a 1N4007, and
> again, there isn't a right lot of point, its a nice touch, but the
> starter motor will put out rather more inductive kickback than a poxy
> bloody relay.
>
>
> >
> > The relay needs to be earthed to the chassis - I was just wondering if
it
> > would be beneficial to run it back to the battery -ve terminal rathe
rthan
> > faff around with yet another chassis earthing point.
>
> No problem, if its easier to put it back to the battery, do it.

Steve Taylor · Feb 28, 2006

Graeme wrote:
> Hi Steve
>
> Thanks for that - I'll bung one fuse in for the time being and get a MCB
> next time I get anything from Maplins or RS.
>

Maplin ? Bwahhahahhaahh.

RS will have something though. Or Vehicle Wiring Products.

> Now I wonder if I could convince the SWMBO that a 101 is a necessary
> purchase?
Vital. And if she's like Lizzy, hide the keys.

Steve

Simon Isaacs · Feb 28, 2006

On Tue, 28 Feb 2006 16:58:34 -0000, "Graeme" <[email protected]>
scribbled the following nonsense:

>
>Now I wonder if I could convince the SWMBO that a 101 is a necessary
>purchase?
>

mine took about 1 second to convince, in the end, it was more her than
me that wanted an ambi, cos she got fed up with the tent, and now
lloks forward to a life of luxury camping!
--

Simon Isaacs

Peterborough 4x4 Club Newsletter Editor and Webmaster
Green Lane Association (GLASS) Financial Director
101 Ambi, undergoing camper conversion www.simoni.co.uk
1976 S3 LWT, Fully restored, ready for sale! Make me an offer!
Suzuki SJ410 (Wife's) 3" lift kit fitted, body shell now restored and mounted on chassis, waiting on a windscreen and MOT
Series 3 88" Rolling chassis...what to do next
1993 200 TDi Discovery
1994 200 TDi Discovery body sheel, being bobbed and modded.....

Graeme · Mar 1, 2006

"Steve Taylor" <[email protected]> wrote in message
news:[email protected]...

>
> > Now I wonder if I could convince the SWMBO that a 101 is a necessary
> > purchase?
> Vital. And if she's like Lizzy, hide the keys.
>
Funnily enough - when we first met she (somehow) ended up using my Range
Rover as her daily vehicle and I got relegated to the 88" - spooky things
these femaliens

GT

Pieter Vroom · Mar 1, 2006

Graeme,

Having given it some more thought I can see (some) sense in two fuses, in
the unlikely case that there would be a short in the relay (i.e. from either
of the battery lives to earth) it could still draw current from the
non-fused battery, if you only put a fuse in one side. Unlikely, if you ask
me, but if you want to be fool proof two fuses would be better.

Pieter

"Graeme" <[email protected]> wrote in message
news:[email protected]...
> Hi Pieter
> "Pieter Vroom" <[email protected]> wrote in message
> news:[email protected]...
>> I am no car electrician but would have thought:
>> 1) there is no need for two fuses, after all when the relay closes live
> from
>> car battery and live to aux. battery is one circuit. Size of fuse would
>> depend on the rating of the relay.
>
> I'm using this as a guide:
> http://www.kampenwagen.co.uk/split charge relay.htm
>
> plus the printed instructions with the fancy relay I've bought - both
> suggest a fuse to both positive terminals. The relay is rated at 25 Amps
> so
> I'll use that size fuse.
>
>>
>> 2) Don't quite get this. What negative feed from the relay? The only
>> "negative" would be the earth in the actuation part (if that is the right
>> word in English, sorry am Dutch) of relay (i.e. small current from the
>> alternator terminal that also controls the charge light of your dash),
>> the
>> current that closes the relay to join positive terminals of battery
>> together. The aux battery obviously would need a good earth to charge.
>
> The relay needs to be earthed to the chassis - I was just wondering if it
> would be beneficial to run it back to the battery -ve terminal rathe rthan
> faff around with yet another chassis earthing point.
>
> Graeme
>
>

Split Charge relay - advice

Graeme

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Pieter Vroom

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steve

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