What fuse needed for a 12v inverter?

[Nate]

Originally Posted by jabber82

I think I am just going to redo all the wiring and make it off the key switch and add in rockers for added future ability.

Very smart in my opinion, eliminates wasting time trying to figure out what someone else did.

You are correct, you would not need a solenoid rated for 400 amps or even 200 amps continuous but if you get a good price on one you probably won't ever change it out again! Lol
And it would operate at pack voltage. Even a used one would work at these lighter loads for a long time.

[jabber82]

Thanks Nate. I once had to rewire my entire garage due to the rats nest created by the previous owner. Much faster to just rip everything out and start over from scratch.

I saw a 200 amp for around $35-$45. Only about $10 more than a 100 amp.

[teecro]

Originally Posted by Nate

Very smart in my opinion, eliminates wasting time trying to figure out what someone else did.

You are correct, you would not need a solenoid rated for 400 amps or even 200 amps continuous but if you get a good price on one you probably won't ever change it out again! Lol
And it would operate at pack voltage. Even a used one would work at these lighter loads for a long time.

Think that I will be keeping the stock 200 amp solenoid around for a reason now..... I don't yet have a need but least now I've got a reason... lol

[scottyb]

A 'continuous duty' solenoid is designed for about 20 hours max before heat damage begins. If the key is left on (solenoid activated) when the cart is not in use this solenoid may be damaged after 20 hours.

[jabber82]

Originally Posted by scottyb

A 'continuous duty' solenoid is designed for about 20 hours max before heat damage begins. If the key is left on (solenoid activated) when the cart is not in use this solenoid may be damaged after 20 hours.

Thanks for the warning. That won't be a problem though. With 3 boys under the age of 7, the key is NEVER left in the cart

[Sergio]

A few things to consider:

The 48v->12v DC converters that do not have a built in "trigger" wire circuit, only produce the large spark the first time they are connected to a power source and the internal capacitors are in a discharged state.

If You add a switch or solenoid to disconnect the 48v side as a means to turn it on/off, You will be creating that scenario every time You turn the cart on.

That is probably the worst thing you can do to the converter as it will cause premature failure of the converter due to unnecessary stress of the capacitors.

It also creates a damaging DC arc that will also cause premature failure of the switching device.

The 200amp solenoid is an overkill for a system that will use the most 10amps on the 48v side, the coil for those solenoids also have a much larger "cold" current, not to mention a very large reverse voltage spike during disconnect.

Once the converter capacitors are charged, the "quiescent" current needed to maintain their charged state is negligible, so You are better off having the converter on all the time and switch the 12v DC output with the key switch by using a smaller "charger" type relay.

That also ensures the 12v DC output is stable and not "unregulated" as it may be the case during the initial converter start up charge.

This is a picture of the relay: http://www.buggiesgonewild.com/attac...ux_battery.jpg

You can order from here, or google the part #: Mouser Electronics Relay Link

If You are going to also install a Radio and need a constant +12v output to maintain the presets while still turning all accessories ON/OFF with the key switch, You can wire the relay as described in this thread:

http://www.buggiesgonewild.com/elect...ml#post1092226

Don't forget You always need to use a fly-back diode reversed biased and connected across the relay coil terminals.

Diode Link from Mouser: 1N4007 Diode for fly-back.

[joesam]

Sometimes a picture is worthwhile. Here's an actual photo of a fly-back diode installed on a relay. Not a golf cart application - but gives you a good idea.

[jabber82]

Thanks a lot Sergio. Now you have me completely screwed up

I was going to wire the 48V side of the converter off the key switch and run the 12V side to a fuse box. Fuse box leads would go to switches on the dash and then to accessories. Run all grounds through a bus bar direct to neg terminal on the last battery in series. But you bring up a good point. I will be forcing the capacitors to load every time I turn on the cart with the key.

I think the best way for me to wire everything up is to keep the 48v->12v converter on the batteries. Just so I have your diagram correct (and I have very limited knowledge of relays from never really using them), please verify that I am correct on this:

12v from converter goes to #30. 12V output to fuse box is #87. Key switch is #86 and ground is #85? Or, using your above link "http://www.buggiesgonewild.com/attac...ux_battery.jpg", #30 is the lead on the bottom right, #87 is the top right lead. #86 is upper left and #85 if lower left.

All this will give me a constant and a switched 12v source for any and all accessories. Is this correct?

And that last line about a fly-back diode reversed biased... I'm not even sure that is english. I have no idea what that is.

[Sergio]

You got it, the picture I linked where it says:

"From 12v Aux battery" is where You connect the output of your converter (0.250" spade terminal). This is the "common" or #30 terminal on a 12v Bosch type relay.

"To 12v Accessories" goes to your fuse box (0.250" spade terminal). This is the "Normally Open" or #87 terminal on a 12v Bosch type relay.

The two terminals on the left are the 48v relay coil (0.187" spade terminals). These are equivalent to #85 and #86 on a 12v Bosch type relay.

I kept repeating the "12v Bosch type relay" because you cannot use that type relay in this application since You need a 48v relay.

The diode needs to have the "Cathode" or end with a "stripe" pointing to the relay coil terminal that you put the +48v from the Key switch.

The idea is that when the key switch is OFF, the 48v relay is off and all power to the fuse box is off. You can still wire your individual switches for lights, etc, but they will all go off when the key switch is OFF.

The +12v constant output will be on the "converter" side of the relay (#30 on your terminology).

You can wire a "long term" ON/OFF toggle storage switch on the +48v side of the converter, or just remove the fuse if you are going to store the cart for a few months.

Also, If you are still using the OBC, You must connect the negative to the controller B-, not the pack negative. This is necessary so that the OBC can measure the current being used by the converter.

[jabber82]

Yes, I was using the terms for a 12v bosch style (as those are the only ones I have experience in) just so I could wrap my head around the wiring. I completely understand the need for the 48V coil type. I could use the Bosch style one for about 6 seconds :). But then the melted black plastic would be hard to clean up.

And a REALLY newb question, the OBC. I assume you are talking about an OnBoard Charger. I am using a powerwise charger that came with the cart. Same thing?