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itolond

Member Since: 16 Jan 2016
Location: Singapore
Posts: 193

1997 Defender 110 300 Tdi SW Alpine White

dual battery (parallel setup)

Hi Forum,

i have a DC/DC setup for a dual battery setup which unfortunately this setup does not allow for using the Aux battery as a backup starter (parallel or only).
I have been advised by the DC/DC supplier i will need to isolate the DC/DC unit out of the circuit if I bridge the Aux and th Starter. This is very easy as the unit is 25 Amp and this can be a relay.
Equally via a high duty switch i can manually 'bridge' the AUX/Starter battery - again all good.

the question is the join the two to prevent 'fudge ups', e.g. relay to isolate DC/DC energised when the manual Heavy duty switch is 'on'

if i connect POS from Start bat to one pole of the heavy duty switch and the POS of the AUX bat- bot are energised - so how to trigger the relay?

8th Feb 2018 2:03am

rallysteve

Member Since: 10 Feb 2014
Location: Cumbria
Posts: 2196

2002 Defender 110 Td5 DCPU Keswick Green

Use one of the FIA battery isolator switches with the auxiliary contacts on the bottom. From memory there is one normally open and one normally closed contact. Use ome of these to trigger your relay.

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8th Feb 2018 7:39am

itolond

Member Since: 16 Jan 2016
Location: Singapore
Posts: 193

So the FIA switch (From looking at these on internet)

Provides the manual battery connection (200Amp - 1000amp Crank) all ok
the 4 pole connector at the base - i take it is :
2 circuits (1 NO/1 NC) - i would use these to trigger the DC/DC isolator Relay????

8th Feb 2018 8:11am

MadTom

Member Since: 10 Sep 2013
Location: Olomouc
Posts: 564

Do you need the DC/DC converter between the batteries? Is it much simpler without it and just direct charging both batteries from alternator. You need only some sort of switch (I prefer heavy duty relay/solenoid) to disconnect batteries, with not running engine. And for the case od death battery a way, how to bridge the solenoid - with additional manual switch, or simple with just reconnecting wires. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo

8th Feb 2018 9:06am

DuncanS

Member Since: 07 Dec 2013
Location: Cumbria
Posts: 295

2008 Defender 110 Puma 2.4 USW Santorini Black

What I used on my old freelander was a voltage sensitive relay and two key isolators, but I removed one key out of the vehicle. This means that I could have either the VSR in, or the manual bridge in and the VSR disconnected. It worked a treat. North Cumbria Search and Rescue - Team Leader

8th Feb 2018 9:50am

rallysteve

Member Since: 10 Feb 2014
Location: Cumbria
Posts: 2196

itolond wrote:
So the FIA switch (From looking at these on internet)

Provides the manual battery connection (200Amp - 1000amp Crank) all ok
the 4 pole connector at the base - i take it is :
2 circuits (1 NO/1 NC) - i would use these to trigger the DC/DC isolator Relay????

Yes

02' 110 TD5 Double Cab Rebuild Thread
84' 90 3.9 V8 Caged Pickup Build Thread - Now For Sale

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8th Feb 2018 9:54am

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