Powering internal electrics from second battery?

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kenbw2
(Donor 2017)
Posts: 271
Joined: 23 Dec 2014, 00:24
Location: Bradford
My Cars: -
Current:
2000 Citroen Dispatch 1.9TD: daily driver
1997 Peugeot 806 1.9TD: backup vehicle
1996 Citroen Synergie 1.9TD: donor car
1997 Citroen Xantia 2.0 16v: Aussie play thing

Former:
1999 Citroen Dispatch 1.9D DW8: got a new owner
1994 Peugeot 106 1.5D: killed by a deer
1996 Peugeot 106 1.5D: cremated
x 23

Re: Powering internal electrics from second battery?

Post by kenbw2 »

As I mentioned I've got a voltage detecting relay, so that's a solved problem.

It's just getting the internal electrics running off the internal battery. I like the fuse outlet spade connector idea, I think I'm going to roll with that.

Does anyone have an idea of how much sustained amperage I could safely pull through the cigarette lighters' wiring?
old-un77
Posts: 166
Joined: 25 Nov 2014, 19:58
Location: peterborough
My Cars: Renault 14...now skyward
Renault 19.. skyward also..
'03 Xsara 1.8 Picasso in silver met his maker
'06 Desire, again in silver also gonn to metal heaven

Re: Powering internal electrics from second battery?

Post by old-un77 »

on my '03 Pic its fused at 20 amps, I run a 20 amp diode through a 10 amp fuse in the cigar adaptor for charging my second battery.....
kenbw2
(Donor 2017)
Posts: 271
Joined: 23 Dec 2014, 00:24
Location: Bradford
My Cars: -
Current:
2000 Citroen Dispatch 1.9TD: daily driver
1997 Peugeot 806 1.9TD: backup vehicle
1996 Citroen Synergie 1.9TD: donor car
1997 Citroen Xantia 2.0 16v: Aussie play thing

Former:
1999 Citroen Dispatch 1.9D DW8: got a new owner
1994 Peugeot 106 1.5D: killed by a deer
1996 Peugeot 106 1.5D: cremated
x 23

Re: Powering internal electrics from second battery?

Post by kenbw2 »

Yea mine's fused at 20A too, I'm not convinced the electrics are designed for consistent pull at 20A though. Don't want to fry my electrics...

What's this diode? It sounds less complicated than the relay I already have. The relay I use allows charge through if the input s above 13.9V, and isolates if not. What does your diode do differently?
old-un77
Posts: 166
Joined: 25 Nov 2014, 19:58
Location: peterborough
My Cars: Renault 14...now skyward
Renault 19.. skyward also..
'03 Xsara 1.8 Picasso in silver met his maker
'06 Desire, again in silver also gonn to metal heaven

Re: Powering internal electrics from second battery?

Post by old-un77 »

its a cigar adapter feeding a inline diode +ve out.......mounted on a red crocodile clip, big enough to grab the battery posts ...only works while ignition is on...diode was to prevent spare battery trying to start the car if the car battery was down on volts.........didn't want the wiring frying.

the adapter started life as part of a maplin solar panel lead
Bob
BX
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Joined: 30 Oct 2009, 00:53
Location: Ireland
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x 17

Re: Powering internal electrics from second battery?

Post by BX »

The problem with charging with a diode is that there will be a 0.5 to 0.6 volt drop across the diode. In order to fully charge and to prevent any risk of sulphation batteries which are cycled need to charge to over 14V. The voltage regulator of the alternator regulates to a nominal 14.2V. if you loose 0.6 then you will not achieve full charge. The voltage sensitive split charge relay is the way to go. Charge is only transferred to the leisure (house) battery when the engine battery reaches a pre-determined voltage. Where batteries are used for back up power they are usually charged in stages. First they are charged to about 2.4V per cell. This equalises the cells and ensures the battery is fully charged. When the charge current at this voltage drops to a predetermined amount depending on cell construction and capacity the charging voltage is dropped to about 2.2V per cell. The batteries are then kept on float at this voltage until another discharge event occurs.
For the built in jump start use the isolator with the removable key. This is NOT part of the charging arrangement. The other option is to use a solenoid switch as used on the older cars with the inertia type starter. This can be operated via a non latching push button so there is no risk of leaving them joined after starting.
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