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Old Seagull Man
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Joined: 21/12/2019
Location: Australia
Posts: 55

Posted: 02:51pm 29 Sep 2020

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Looking around for battery protection. Low voltage disconnect, in particular.
Suitable for a 60volt lead Acid Pack.

I can find plenty of 24, 36, and some lovely 48volt stuff, from victron.

But what are those of you with 60, 72, and 96v battery system using.

I thought of High power SSR, Crydom make 150 amp 200 volt units at about $300.
There are Chinese ones but they don't seen to be quite the same when it comes to ratings. If you have found a brand that is reliable please let us all know.

So please all ideas most welcome.

Solar Mike
Guru

Joined: 08/02/2015
Location: New Zealand
Posts: 1138

Posted: 08:53pm 29 Sep 2020

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Plan B failsafe: these voltage sensing relays or similar can be used, connect them to a high current evac relay to turn off your high current battery loads.
Voltage Relay

Suitable evacuated relays similar to this are suitable for the load disconnect.

Aliexpress have quite a few different low voltage sense modules that may be suitable. I wouldnt attempt to use any solid state DC relay, they are easilly zapped by voltage spikes and are not very efficient with large currents, requiring a big heat-sink to cool them.

Cheers
Mike

Warpspeed
Guru

Joined: 09/08/2007
Location: Australia
Posts: 4406

Posted: 08:55pm 29 Sep 2020

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Low voltage disconnect can be tricky.

When the battery gets a bit down, sudden surge loads such as starting up a refrigerator can pull the battery voltage way down for a second or two.
That can trip a low voltage disconnect, even though at normal steady load, there may be many hours of useful battery capacity remaining.

I suggest you use a voltage divider to reduce the voltage being sensed so that a lower voltage rated sensing circuit will work.
Also include a large electrolytic with a time constant of several seconds to smooth out any violent dips in voltage.

Cheers, �Tony.

brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548

Posted: 10:03pm 29 Sep 2020

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I made up a panel with cartridge type 120v fuses plus those el,Cheapo battery switches from e-bay ..

Never had a problem ,though someone on this forum had welded contacts with his.

I make sure the load is low at the time of switching or pull the fuse.

This is the back ,the cable is divided because its 50mm and those entry holes are for 20mm or so .

Oh, forgot --- those connections on the back of the switches are contacts for a relay or other external device that could be activated when switching the red key.on or off.

�

Bruce
Edited 2020-09-30 09:51 by brucedownunder2

Bushboy

Old Seagull Man
Regular Member

Joined: 21/12/2019
Location: Australia
Posts: 55

Posted: 12:28pm 02 Oct 2020

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Thanks to all for the excellent ideas, stuff has already been bought.
And a solution is well in hand.

Thanks Andrew

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