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Chargery and 48v coil relays?

Maast

Compulsive Tinkerer
Joined
Oct 31, 2019
Messages
773
Location
Washington State
After a good bit of thrashing around, I'm now thinking its a very good idea to use 48v coil contactors/relays for 200A and more. The reason being is that you have a 48v source ready to hand and you wouldnt need an additional 12v power source thats burning additional juice to run. The same reasoning applies to a 24v system.

The Chargery outputs 12v to drive relays, but it can only do 3 amps. Thats fine for up to about 150A but above that the contactors are pulling 3.5-4 amps at 12v to actuate - which makes sense because you're moving big chunks of metal around.

After they actuate if you get the right model contactor the power usage goes down to about 2 watts to hold. Gigavac at least has dual coil 2 watt models at any size you could ever want. You'd need a top quality SSR to drive them like a Crydom and they run about $35 US but their power use is minimal.

Also, for the Chargerys longevity I realized I don't WANT to have the Chargery directly driving relays, the lower the amount of power flowing through it the less stressed it is and the longer it'll last, same reason I've turned off its balancing feature.

The system I'm building has every chance of being in place for the next 15 or 20 years so reliability is THE top priority and the Gigavac/Crydom route will outlast me, and use minimum power while doing it.

BTW, I'd never EVER pump 300 amps through a inexpensive Chinese SSR, the only SSR I'd trust to last for the next decade would be a Crydom/Odom quality level SSR and at that amperage they're horribly expensive, and even then I don't think I'd trust it. Industry uses contactors for big loads for good reason.

The downside to the 48v coil Gigavac/Crydom is that I'm spending more on contactors/SSRs that I did on the Chargery itself but the contactors are "where the rubber meets the road" so I consider that money well spent.

Thoughts?
 
Sorry to say it, you won't like it but it is a false economy.
I've pushed 250A through 300A DCC's and they never even got warm to the touch, let alone starting their fans.
DCC's only use 11ma. which is NOTHING and no trouble at all for the Chargery BMS.
If you are that paranoid over it, then goto the 600A DCC and never look back again.

But.. I AM the Chargery Guy, so what can I say...
Waiting on the release of the new P Series BMS with Active Balancing and better comms, +++ Due next month.
 
Sorry to say it, you won't like it but it is a false economy.
I've pushed 250A through 300A DCC's and they never even got warm to the touch, let alone starting their fans.
DCC's only use 11ma. which is NOTHING and no trouble at all for the Chargery BMS.
If you are that paranoid over it, then goto the 600A DCC and never look back again.

But.. I AM the Chargery Guy, so what can I say...
Waiting on the release of the new P Series BMS with Active Balancing and better comms, +++ Due next month.
We're gonna have to agree to disagree on that, I might change my mind is 10 years but for now I'm sticking with contactors since I KNOW they'll last.
 
I wouldn't load the Chargery disconnects by more than 500 mA each. If you want to drive a relay coil then I suggest interfacing the 12V disconnect signal to an opto isolator and then use a mosfet to control the relay.
 
I wouldn't load the Chargery disconnects by more than 500 mA each. If you want to drive a relay coil then I suggest interfacing the 12V disconnect signal to an opto isolator and then use a mosfet to control the relay.
Er, thats exactly what I'm saying. Using a low power SSR to drive a much higher power contactor. Opto isolation is fairly irrelevant at these voltages and in any case every SSR that I know of is already opto-isolated, even those uber-crappy chinese fosteks.
 
We're gonna have to agree to disagree on that, I might change my mind is 10 years but for now I'm sticking with contactors since I KNOW they'll last.
Especially as I'm using a 40kohm resistor as a precharge circuit, only passes about .1millamp @ 51v but the numbers say it'd keep/pre charge the capacitors in about 25 mins but keep the voltage low enough that the inverter doesnt try to turn itself back on.
 
Sorry to say it, you won't like it but it is a false economy.
I've pushed 250A through 300A DCC's and they never even got warm to the touch, let alone starting their fans.
DCC's only use 11ma. which is NOTHING and no trouble at all for the Chargery BMS.
If you are that paranoid over it, then goto the 600A DCC and never look back again.

But.. I AM the Chargery Guy, so what can I say...
Waiting on the release of the new P Series BMS with Active Balancing and better comms, +++ Due next month.
Which DCC do you use. I’m using two 200amp EV relays that get quite warm and use roughly 13watts constantly
 
Which DCC do you use. I’m using two 200amp EV relays that get quite warm and use roughly 13watts constantly
FWIW the gigavacs I'm using never get above ambient as far as touching it goes. And their being held closed 24/7. They're screwed down to a metal plate so that could be acting as a heatsink.
 
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