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How much draw can I put through a DS Low Voltage Cut-out?

Submitted: Tuesday, Aug 01, 2006 at 19:53

Trevor M (SA)

After reading about it in the archives I have purchased a DSE Low Voltage Cut-out kit (K3124). I have not put it together yet but I wonder if one of the electronics gurus can give some advice.

My primary intention was to connect it on the accessory plugs at the back of the Troll where the fridge runs. I have run a dedicated cable from the battery to the 2 outlets at the back and started to wonder whether it is best to locate the cut-out unit at the back near the fridge or under the engine bay near the battery? If there is no difference my preference would actually be for in the engine bay so I don't take up space at the back and also it would be easier to get to.

The next thought was how many accessories could I run through the cut-off unit? I have a second cable direct from the battery which powers another couple of ciggie plugs under the drivers seat and a 300W Pure Sine Wave inverter (also under the seat).

Would I be pushing it to route all of these accessory wires through the cut-out unit (would be easy if it was under the bonnet near the battery) or is there too much current etc? The specs of the kit do not address the subject. Each cable is separately fused at the battery and they are heavy gauge.

As mentioned, I bought it initially just to go at the back for the fridge but if it can cover more with no problems then why not?

Thanks in advance for advice

Trevor

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ThreadID: 36367 Replies: 6
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AnswerID: 186578   Submitted: Tuesday, Aug 01, 2006 at 20:07

Derek from Affordable Batteries & Radiators replied:

There are ready made units. Why build one.

They range from 10amps to 60amps.

Engel have a new 15 Amp one with digital volt meter built-in. $98.00 RRP. and it has a voltage selector switch 10.5v or 11.5v cut out.



Regards Derek
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FollowupID: 443644   Submitted: Tuesday, Aug 01, 2006 at 20:47

HJ60-2H posted:

Because it can be fun, interesting and satisfying to build stuff. Why pay more than you need to?

I would put it close to the battery. Covers more.
FollowUp 1 of 1
AnswerID: 186593   Submitted: Tuesday, Aug 01, 2006 at 20:58

Member - Phil G (SA) replied:

Trevor,

10amps is the limit of the relay.
The voltage cutout is adjustable from 10.9 to 11.9 volts. Mine cuts out at 11.7 when the variable resistor is turned to the highest setting.

Install it next to the fridge. If it does cut out, you press the red button to restart it. Can't see that under the bonnet! And the most likely time it will do that will be overnight, so having it visible is good.

I wouldn't have anything else on the cutout - just the fridge - the fridge is the only accessory thats likely to flatten a battery past the point of no return.

You haven't mentioned what brand fridge you own, but a waeco has a built-in cutout with 3 settings; and the latest Engel won't cycle at below 10 volts, which is too low for the battery anyway.

The DSE cutout uses 30 milliamps continuously, so its best to have it out of the circuit when not being used, otherwise it can gradually flatten your 2nd battery.

Jaycar sell a different kit that uses transistors, and consumes about 8 milliamps.

And like Derek says, theres a heap of made up units on the market now. The kits came out well before the ready-made units - I think I've been using mine for about 8 years now.

Cheers
Phil
Mt Finke
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AnswerID: 186596   Submitted: Tuesday, Aug 01, 2006 at 21:07

Member - Mike DID replied:

Oatley Electronics sell an excellent kit that can be used as Battery isolator or LowVoltage Cutout and it costs only $19.

It can handle EIGHTY amps continuously and uses minimal current when on or off because it uses a latching relay.
Mike R
Reply 3 of 6
FollowupID: 443687   Submitted: Tuesday, Aug 01, 2006 at 23:38

drivesafe posted:

A little care should be take when using any device with an AC specific relay.

Of the couple of these devices I have seen, the relay is marked for AC switching.

When a relay is designed for DC or AC and DC use, it will have much more robust contacts and even then, they are usually marked to be able to switch a higher AC load than the DC load.

If a relay is marked only as an AC relay then it is probably going to have a short operating life if it is used to switch any heavy DC loads as the contacts will be burnt out by the arcing that occurs with switching DC.

Cheers
FollowUp 1 of 2
FollowupID: 443719   Submitted: Wednesday, Aug 02, 2006 at 09:09

Member - Mike DID posted:

True, though hopefully a low-voltage cutout won't even do 1000 cycles.
Mike R
FollowUp 2 of 2
AnswerID: 186601   Submitted: Tuesday, Aug 01, 2006 at 21:30

Marn replied:

You would be better off putting it next to the battery as then it would not "see" the voltage drop of the cable running to the back.
Reply 4 of 6
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AnswerID: 186625   Submitted: Tuesday, Aug 01, 2006 at 22:25

Crackles replied:

Trev...Fit it inside the car out of the heat, dust & water in a location easy to reset. I would run the fridge & lights off the discinnect switch (items that may be left on) & the rest on a separate circuit.
Cheers Craig..........
Reply 5 of 6
AnswerID: 186678   Submitted: Wednesday, Aug 02, 2006 at 09:41

Member - andrew B (Kununurra) replied:

I'm in the process of doing something similar. Have you considered running all of the accessories through a heavy duty solenoid, and use the low voltage cut out to control the solenoid. That way, the low voltage cut out has very little load, and there should be minimal voltage drop.

Cheers Andrew
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FollowupID: 443731   Submitted: Wednesday, Aug 02, 2006 at 09:50

Member - Phil G (SA) posted:

Andrew, any idea what the power consumption is of the solenoid coil? Maybe that would be an issue when the vehicle is stopped?
Mt Finke
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FollowupID: 443749   Submitted: Wednesday, Aug 02, 2006 at 11:27

Member - andrew B (Kununurra) posted:

No idea sorry, will have to investigate at some stage

Cheers Andrew
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FollowupID: 443764   Submitted: Wednesday, Aug 02, 2006 at 12:37

Member - Mike DID posted:

The Oatley Electronics solenoid kit draws zero current, except when switching on or off.
Mike R
FollowUp 3 of 4
FollowupID: 443831   Submitted: Wednesday, Aug 02, 2006 at 18:23

Member - Phil G (SA) posted:

Andrew, Mike,

Out of interest, just measured the current that the coil on a 30amp Bosch relay draws - 170 milliamps. And it would be a lot less than your average solenoid - I'm not aware of the solenois used in the Oatley kit.

Anyway, if you used that simple relay, you'd lose 4Ah per day for no good reason.

Mt Finke
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