Split charge Relay and power drain

slarty · 11-02-2003, 01:48 PM

Hi

I had an SV24 with a DC/DC PSU from MGPower and ran a 600w AMP @ 30 AMP.

I now have a regulated C134 EPIA-M and run it off the same system, i.e. a second battery in the boot/trunk. The problem I have is that the PC and AMP on together will drain the battery in 20 minutes flat. I can only surmise that the relay is not charging the battery. I get 14.3v at the main battery terminal and going into the relay but ony 12.3v at the second battery terminal on the relay and on the second battery terminal.

The relay has

Power In from main battery
Power Out to second battery
Fridge Power Out
Ground
Ignition light

When I take a reading off the ignition wire it only reads between .1 and .15 of a volt, I thought that this may be the cause?

Basically the voltage off Power out to the second battery seems to be just the voltage from the battery and when I power up the PC it just steadily drops about .1 volt every 40 ish seconds

I have searched the forum on split charge relays and found some interesting links and coments made on the "Black Art" of Lead Acid battery charging

Any help welcomed

Spaghetti · 11-02-2003, 01:59 PM

Sounds a bit too technical for me, but..... I don't suppose you have any pics of your set up do ya...??

I wanna Prelude myself...

slarty · 11-02-2003, 03:08 PM

Quote: Originally Posted by Spaghetti

Sounds a bit too technical for me, but..... I don't suppose you have any pics of your set up do ya...??

I wanna Prelude myself...

I do but they are of the old setup, I had an sv24 and a 10.4" screen but I got sick of the size of the screen and the space that the sv24 took up

http://www.btinternet.com/~jonathan_porter

The site will be updated as soon as I solve this power issue!

Spaghetti · 11-02-2003, 06:04 PM

That's a lotta wires!

meddler · 11-02-2003, 07:21 PM

It definately sounds as tho the second battery is not being charged. If you could draw a diagram of how it is wired up I will be able to help you. Obviously your alternator is working because you have 14.3v at your main battery. If you have wired it up correctly, when the car is running you should have about 14V (varies due to resistance in wire from alternator to the back of the car.) at the second battery.

My first suggestion is double check all your wiring.

slarty · 11-03-2003, 06:11 AM

Quote: Originally Posted by Spaghetti

That's a lotta wires!

There's a lot less now

slarty · 11-03-2003, 07:57 AM

Quote: Originally Posted by meddler

It definately sounds as tho the second battery is not being charged. If you could draw a diagram of how it is wired up I will be able to help you. Obviously your alternator is working because you have 14.3v at your main battery. If you have wired it up correctly, when the car is running you should have about 14V (varies due to resistance in wire from alternator to the back of the car.) at the second battery.

My first suggestion is double check all your wiring.

Thanks for this. Its a bad diagram but it gives the idea The wire to the rear battery is a heavy guage and about 2 metres

I don't know what else to try at this time.

meddler · 11-03-2003, 09:07 AM

Quote: Originally Posted by slarty

Thanks for this. Its a bad diagram but it gives the idea The wire to the rear battery is a heavy guage and about 2 metres

I don't know what else to try at this time.

It should be wired up as shown in the pic below. I have drawn in the connections for a standard bosch type auto relay, but you should be able to figure it out if you are using something else. It sounds as tho you have the relay wired up incorrectly. Any more dramas let me know.

slarty · 11-03-2003, 09:37 AM

Quote: Originally Posted by meddler

It should be wired up as shown in the pic below. I have drawn in the connections for a standard bosch type auto relay, but you should be able to figure it out if you are using something else. It sounds as tho you have the relay wired up incorrectly. Any more dramas let me know.

85 does go to ignition on but it goes to the ign on the head unit loam. is .1v enough to switch the relay. Also does the relay switch immediately to charge the second battery as it has the ignition on.

Thanks for the help!

shakes · 11-03-2003, 01:18 PM

most 'ignition' inputs need 12v to trigger. sounds to me like that's the culprit

slarty · 11-03-2003, 02:15 PM

Quote: Originally Posted by shakes

most 'ignition' inputs need 12v to trigger. sounds to me like that's the culprit

Nice one I'll find a new input ...hmm

shakes · 11-03-2003, 02:44 PM

what is the part number for your relay? just curious

slarty · 11-03-2003, 03:16 PM

LUCAS 33RA associated documents XXB464

I'm going to try and work on it next weekend... the keyboard drain is enough to drain the battery overnight... I think I need some kind of intelligent circuit here. time to start searching the forum

meddler · 11-03-2003, 07:12 PM

as Shakes said, you need 12V across the relay to get the relay to click (probably about 8V min). Getting 12V from the ignition on from your head unit should be enough to make the relay change contacts. Make sure the other side of the coil for the relay is going to ground. The relay is definately the problem, either the realy itself or the wiring for the coil in the relay (terminals 85 and 86)

slarty · 11-04-2003, 06:01 AM

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Quote: Originally Posted by meddler

as Shakes said, you need 12V across the relay to get the relay to click (probably about 8V min). Getting 12V from the ignition on from your head unit should be enough to make the relay change contacts. Make sure the other side of the coil for the relay is going to ground. The relay is definately the problem, either the realy itself or the wiring for the coil in the relay (terminals 85 and 86)

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When the 12v comes from IGN on is it a perminent on and therefore a perminent signal to the regulator to charge the second battery. so when Ignition is off the relay disconects on allowing the rear battery to discharge. Excuse the basic theorising, I'm clearing this up in my head.