144v dc on/off switch

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Paul9
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144v dc on/off switch

Post by Paul9 »

Hi people

I'm looking for an on/off switch rated to 144v DC or at least I think I am?

The aux battery in my conversion is charged by both a solar panel on the roof of the car and a DC-DC converter. Many times the sun is shining and the solar panel provides more than enough charge into the battery. At these times I do not need the dc-dc to draw from my traction pack when the solar panel is doing a perfectly adequate job by itself. My dc-dc is a Mean Well HLG-600H-15AB.

I asked the Aust distributor for Mean Well about an on/off switch either on the 12v dc output side or on the 144v dc input side of the converter. He said it would be best to put it on the input side. He said "In regards to switch, I would put it on the AC side so there is no power going to the LED Driver"

So I suppose I am looking for an on/off switch rated to 144v DC? Anyone know where I can buy one? My google searches have turned up nothing. Any alternate solutions welcome.

Thanks in advance
Paul
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coulomb
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Re: 144v dc on/off switch

Post by coulomb »

Paul9 wrote: Tue, 26 Jul 2022, 14:17 So I suppose I am looking for an on/off switch rated to 144v DC?
That's actually tricky to do properly and safely. In Weber's MX-5, he has a pair of EV200 contactors to do this (he has two Meanwell DC-DCs, one for each half pack). These have a 12V coil, which is easy and safe to switch.

But these are now quite expensive, and I question whether you actually need to switch off the DC-DC when the solar is working well. The solar will be pushing up the auxiliary battery voltage, so the DC-DC will draw little power anyway. Plus, it would be easy to forget to turn the DC-DC back on later.

Also, don't you already have a way of turning off the DC-DC? Or does it run 24/7?
MG ZS EV 2021 April 2021.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
Patching PIP-4048/5048 inverter-chargers.
antiscab
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Re: 144v dc on/off switch

Post by antiscab »

Put the dcdc on the other side of your main contactor, so it's always off when the ignition is off. Sounds like your 12v battery is never really going to go flat
Matt
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Paul9
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Re: 144v dc on/off switch

Post by Paul9 »

Thanks Mike and Matthew

You are right Mike I do already have an on/off switch controlling the dc converter but it is on the 12v output side of the converter. It seems to work satisfactorily but it appears that the distributor of the converters prefers the on/off switch to be on the input side. Hence my concern.

Matthew, my aux battery hasn't ever gone flat but at times it has gone "weak".

To give you both a little background, my main problem is with the MC600 ZEVA motor controller. When I turn my headlights on the motor controller turns off. This doesn't happen all the time. It happens mostly when I first turn on the ignition and then the headlights. Once it happened half way through a trip at night. This is something that the ZEVA motor controller manual warns about. The controller manual specifically mentions that turning on the headlights can cause the motor controller to turn off due to a weak 12v system.

Another factor that may contribute to the problem is that my aux battery is 12v Lithium. I think I need to keep it's voltage higher than a 12v lead acid battery. 12.8v in a lead acid battery is pretty much full but 12.8v in a 12v lithium is close to empty.

Comments on the above are very welcome!
Thanks
Paul
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coulomb
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Re: 144v dc on/off switch

Post by coulomb »

Paul9 wrote: Wed, 27 Jul 2022, 09:26 You are right Mike I do already have an on/off switch controlling the dc converter but it is on the 12v output side of the converter.
It seems that this was wise. From this post in Weber and Coulomb's MX5:
  • "We also found out why our 12 V battery was tending to go flat if the car wasn't used for a week. There were four 1k5 resistors across the output. So we will need to add relays to isolate the DC-DC outputs anyway, whenever their inputs are not powered."
Hopefully your DC-DC is connected after the main contactor, as suggested above, otherwise that means that the DC-DC is operating 24/7, which would not be good for the longevity of its capacitors etc.
MG ZS EV 2021 April 2021.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
Patching PIP-4048/5048 inverter-chargers.
antiscab
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Re: 144v dc on/off switch

Post by antiscab »

What load does the 12v see when the ignition is off? Have you measured it?

12.8v for a LifePo4 4 cell battery isn't empty, it's about half full. If brown out is a problem for the mc600, I would suggest putting in a small 12v-12v supply to lower it's minimum operating voltage
Matt
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T1 Terry
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Re: 144v dc on/off switch

Post by T1 Terry »

Charging voltage is often misunderstood when it comes to lead acid and lithium LFP chemistries. To fully charge a lead acid battery, the voltage needs to reach between 14.4v and 14.8v, depends if it's an AFM or flooded cell that requires the higher charging voltage. Either type, the lead acid battery is now some where between 70% SOC and 80% SOC. Depending how long the battery has been less than 100% SOC as to the length of time that voltage needs to be held. When it comes to solar, the sun doesn't shine long enough to reach the 14.4 or 14.8v and then hold it there to reach 100% SOC, chargers that don't measure the charging current before dropping into float mode severely under charge lead acid batteries.

Lithium, or LFP to be specific, should come up to 3.6v in every cell at least once every 3 mths, but the charging should stop if a cell reaches 3.6v and allows the balancer to move the excess from any high cells, to the lower cells. Recharging in between the 3 mth balance charge of 14.4v, charging to 14v then dropping back to 13.8v will keep the battery close to 100% SOC, but the charging still needs to stop if a cell reaches 3.6v and not restart until the balancer has moved some of the excess to the lower cells. Often when the stop charging is cycling (1 min to 3 mins) the solar controller will drop into float stage and the high cell will not trip the cell over voltage again that day .... and often not trip it at all until the 3.6v in every cell balance occurs.
An LFP cell is considered fully charged if it holds more than 3.5v at rest and fully discharged if it drops below 3v ..... anything in between is either not fully charged nor fully discharged, the cell voltage doesn't change like a lead acid battery indication the SOC, this can be seen when charging an FLP cell, the voltage will remain the same while plenty of current is flowing into it .... till it's full, then the voltage goes up very quickly and into cell damage territory, so cell monitoring is a must.

T1 Terry
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Paul9
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Re: 144v dc on/off switch

Post by Paul9 »

Thanks guys!
coulomb wrote: Wed, 27 Jul 2022, 10:31 It seems that this was wise.
So Mike I may have accidentally done the correct thing!
antiscab wrote: Wed, 27 Jul 2022, 13:13 What load does the 12v see when the ignition is off? Have you measured it?
Thanks Matthew I am currently using a PowerTech MP3722 Solar Charge Controller. While it does display 12v voltage and charge going in, it doesn't show the load current even though the load does go through the charge controller. The previous controller did show load current but none of it's parameters were user adjustable. The MP3722 does allow user adjustment of parameters. From memory the previous controller showed zero load when the ignition is off.

Thanks Terry for the explanation regarding charging. As a result of your advice I think I may have set the converter current and voltage a bit high. I think I best reduce them a little.

Regards
Paul
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