Dual Battery Relay

[Sluggo]

I want to add a second battery for the stereo, blower, phone charger, etc. Do you need to get those kits from the various vendors? It looks like it's just a regular 30A Bosch relay & 30A fuse with the wires routed to the batteries and voltage regulator. I can get Bosch relays for a few dollars a piece. Just wanted to make sure there wasn't something special about these relays.

[chitwnvw]

I was just wondering the same thing. I'll send you a dollar or two if you want to try the generic relay.

[Sluggo]

I was just wondering the same thing. I'll send you a dollar or two if you want to try the generic relay.

Thanks. But no need. I have several. I'm just wondering if this is like the "Hot Start Relay". Packaging an item as a specific purpose with a higher price when it's just a generic Bosch/Hella relay.

[Amskeptic]

If your aux battery is just an assist when car is parked,
get a big old Ford starter relay.
Hook one big terminal to the aux battery, hook the other to the starting battery. Hook an ignition power source to the relay's solenoid and ground the other. Every time the car is running the alternator can charge the aux battery. When ignition is off, your aux battery is free to do other things while keeping the starting battery fresh to start the engine.
Colin

[chitwnvw]

What about using an isolator?

http://www.geocities.com/harald_nancy/isolator.htm

[Sluggo]

What about using an isolator?

http://www.geocities.com/harald_nancy/isolator.htm

I was looking at those too and it might be the way I go. I'm still curious, just because I like knowing how to do things and how they work. Plus I like finding cheap but equivalent alternatives.

[chitwnvw]

Seems like the isolator or the separator is the "right" way to do it.

You could just hook them together with a manual switch. It would certainly be cost effective.

IIRC you don't have a camper, what are you going to be powering with an aux battery anyway?

[Sluggo]

IIRC you don't have a camper, what are you going to be powering with an aux battery anyway?

Stereo, Heater Blower (I've noticed when I have the lights, stereo and blower on at once my lights dim and the voltmeter drops), lighter/charger in the rear, lights in the engine compartment & cabinets, + whatever else strikes me.

When I play something with a lot of bass, the headlights & dash lights dim to the beat. Kind of cool actually.

[Amskeptic]

Sounds like they are selling something there.

A drained auxiliary battery is not going to be "robbing" the starting battery and raising all hell when you consider that the moment you start the engine after an all-night party of stereo and tiki lights and heat or whatever, the draw of the starter motor is going to be pulling the voltages between the two damn close to equal, the amperage will be flowing to the starter.
Once the engine is running, both batteries will have a very similar potential the alternator will likely favor the starting battery's quick loss of surface charge at first and then get to work on the drained aux battery.
Colin.

[BlissfullyCrusin]

When I play something with a lot of bass, the headlights & dash lights dim to the beat. Kind of cool actually.

You might want to consider a Stiffening Capacitor. It's about the same price as a dual battery kit, maybe a little less once you factor in the cost of the second battery.

You won't be able to run stuff with the car off though. Just a thought.

[Sluggo]

If your aux battery is just an assist when car is parked,
get a big old Ford starter relay.
Hook one big terminal to the aux battery, hook the other to the starting battery. Hook an ignition power source to the relay's solenoid and ground the other. Every time the car is running the alternator can charge the aux battery. When ignition is off, your aux battery is free to do other things while keeping the starting battery fresh to start the engine.
Colin

Like this?
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... Track=true

[Amskeptic]

If your aux battery is just an assist when car is parked,
get a big old Ford starter relay.
Hook one big terminal to the aux battery, hook the other to the starting battery. Hook an ignition power source to the relay's solenoid and ground the other. Every time the car is running the alternator can charge the aux battery. When ignition is off, your aux battery is free to do other things while keeping the starting battery fresh to start the engine.
Colin

Like this?

Yep. Please use common sense and keep all live terminals safely free of inadvertant grounding. Thank-you.
Colin

[Sluggo]

Please use common sense and keep all live terminals safely free of inadvertant grounding. Thank-you.
Colin

Of course! I'll mount this in the stock location. Now to figure out where to mount the fuse panel.

[westy78socal]

Can someone post some links to good relays? On my extra battery, I can read how much power it has on the wall, but its not hooked up to the inside outlet under the back seat.

[vdubyah73]

How about a marine battery switch? Turn the switch to the battery you want to use for engine off use. When it comes time to start, turn the switch to the starting battery. Once running, turn the switch to 'all batteries' and charge both or turn it back to the battery you used all night and charge that back to full charge for the next night. I did that with my boat for twenty years and absolutely never had a dead starting battery. Man, I had some wild nights on that old boat. Lights and music 'til wee hours. I frequently had to leave an anchor light on all night too.

http://www.westmarine.com/webapp/wcs/st ... SiteSearch

Bill