Waking up from dead battery situation.

[Craig]

I want the buck converter to be more like a charger
it could be programmed to stop the current when the current flow drops to a configurable percent of CC
or optionally it could drop the voltage to a configurable value
Then if the battery is under load and the voltage drops enough the charger starts helping with the load.

The Idea I have in my head would allow for this.

 

[John Frum]

The Idea I have in my head would allow for this.

I am curious, if and when you want to share.

 

[SCClockDr]

You need to set up your pi to kill everything not essential after 2 days of no charging or some such.

 

[Craig]

Well... Not to put too fine of a point on it,
But that's why I pointed a voltage regulator instead of plain converters...

For an odd voltage like 22V, you would probably have to spend another $5 on voltage regulator & $5 on a relay, but it's very doable...

How many amps can I get through a cheap voltage regulator. Right now I'm looking at maybe 16 amps from panels at 200 volts. Which is about 100 amps at battery voltage.

 

[SCClockDr]

Possibly even shifting to a Arduino minimal controller till charging resumes.

 

[Craig]

You need to set up your pi to kill everything not essential after 2 days of no charging or some such.

Yes that is planned for future. I'm thinking worse case scenario pi might need to be killed as well.

 

[Craig]

Possibly even shifting to a Arduino minimal controller till charging resumes.

Right these would use way less power I was thinking an arduino could turn Pi on and off every so often. I like using the PI mainly because I have more experience with them than arduino.

 

[SCClockDr]

Right these would use way less power I was thinking an arduino could turn Pi on and off every so often. I like using the PI mainly because I have more experience with them than arduino.

Even an AT Tiny might be an option direct off the battery through a latching relay with a program feature to trigger itself off as a last resort. Operator intervention required to reactivate though.

 

[JeepHammer]

How many amps can I get through a cheap voltage regulator. Right now I'm looking at maybe 16 amps from panels at 200 volts. Which is about 100 amps at battery voltage.

Over/Under regulator hooked to a relay of any 20 amp relay.
70-80A 24V automotive style jumps to mind, but use a DT so it doesn't have to be powered all the time to work.
When there is power from the panels, it closes, when power drops from panels it opens.
No power from BATTERIES required.

As soon as power from panels come up to an acceptable level, relay closes and batteries get charged.
Power from panels drops, relay opens and there is your reversion protection to keep panels from sucking batteries instead of a diode.

You *Could* fine tune the open/close voltage with a Resistor on the coil circuit, making it more or less a current regulator like old breaker points regulators were...

I suggested this, and I have run it myself with panels/lead acid batteries but I got reamed a new one on the open forum about it...
A diode & Resistor in the coil circuit keeps the relay from 'Chattering' at the break over voltage point,
A diode having a specific voltage it closes at, Resistor and then diode, let the forward voltage limit of the diode control the on/off cycle during those times when Voc from panel will activate relay, but converter is too much for the panel output and the circuit opens again, over & over...
(Not a 'Flyback' diode)

Ever hear a Ford starter relay just sit an snap over & over?
Stops that from happening.

Of course the 'Easy Button' is a over/under voltage regulator.
Same thing all simple battery chargers use but for over voltage.
Simply shuts down the converter/charger when voltage from the panel drops.
Use a voltage regulator and relay (if it's not built into the board) to control power to the converter.
Set over volt to what the batteries can handle and under volt to minimum voltage you want the cut off to on batteries to be.

Double pole, Double Throw relay let's you cut off the load on the batteries so they don't get sucked dry.
That's *IF* you want to use the cheap crap off eBay and not buy something proprietary for $200...

Same deal I use for my battery under volt and over volt protections, about $20 plus relay.

 

[SolarRat]

my off grid system at times may have weeks of snow

Sorry this is off-topic at the moment, but since you can remotely monitor/control with an Arduino, how about heat pads on the undersides of the panels that you can turn on remotely to melt the snow off? Before the battery goes flat of course.

 

[Craig]

Sorry this is off-topic at the moment, but since you can remotely monitor/control with an Arduino, how about heat pads on the undersides of the panels that you can turn on remotely to melt the snow off? Before the battery goes flat of course.

Yes this is in the plan I'm also planning on tripling the storage capacity to get through the long winter.

 

[michaelgdobbins]

I had a situation this week where my 48v 200ah battery bank BMS shut down and my Sol-ark 8k didn't see enough battery voltage, marked it No battery. Neither one would move without seeing the other. A true stand off.
I tried to reset the BMS with battery tech support help. No go.
I bought a 48v 2a scooter charger, jury rigged a connection to the battery cables between the sol-ark and battery bank, turned on the charger.
The charger was pushing something over 48v at 1.5a. Both sides saw that. Woke up, after a couple of very short charge drain reversals. Both came on line in about a minute and operated normally.

 

[jasonhc73]

In the land of Motorcycles, things that often sit as dust collectors there is a type of battery that is designed to drain and then cut itself off.

Would that simplify this idea of being able to get back online?

LITHIUM BATTERIES, MICRO-STARTS

Smallest, Lightest, Most Powerful Lithium Motorsports Batteries - the First with Built-In Jump-Starting! Top Rated MICRO-START Jump-Starter Power Supplies

antigravitybatteries.com

 

[ytwytw]

Is adding more panels an option?

Throw some more panels in different angles, do some silicon coatings, should help to get some more powers for the batteries.

Looks like to me it's not generating enough power to the battery :think

 

[Craig]

Is adding more panels an option?

Throw some more panels in different angles, do some silicon coatings, should help to get some more powers for the batteries.

Looks like to me it's not generating enough power to the battery :think

Yes it is for sure the problem thus year was between snow and clouds I had no Sun for 3 weeks. Again realize this is a remote situation and I'm looking for Something that will automatically restart my SCC.

 

[Itsasprinter]

Wouldn't it be simpler to go into a low-power-consumption hibernation state based on low SOC that the system can sustain for weeks or months while keeping the charge controller alive? The system checks once a day if SOC has gone back to a safe state and wakes the rest of the systems up again if that is the case. I assume the self-consumption of the charge controller isn't a substantial problem relative to the size of your batteries.

 

[Craig]

Wouldn't it be simpler to go into a low-power-consumption hibernation state based on low SOC that the system can sustain for weeks or months while keeping the charge controller alive? The system checks once a day if SOC has gone back to a safe state and wakes the rest of the systems up again if that is the case. I assume the self-consumption of the charge controller isn't a substantial problem relative to the size of your batteries.

Yes it would and I will. But even then there is a possibility of a long cold winter with snow on my panels for an extended period. I also plan on greatly increasing my battery bank.

Right now I am thinking of putting up a 24 Volt panel without a SCC that goes directly to battery with just a blocking diode for reverse current protection. Just 1 smaller panel that will have a maximum voltage of less than my banks rated max voltage this way it can not overcharge the batteries but hopefully bring it up to where the SCC can turn on.

Im trying to think of a way to add a latching relay so the panel is only on when SCC is off

 

[Itsasprinter]

Yes it would and I will. But even then there is a possibility of a long cold winter with snow on my panels for an extended period. I also plan on greatly increasing my battery bank.

Right now I am thinking of putting up a 24 Volt panel without a SCC that goes directly to battery with just a blocking diode for reverse current protection. Just 1 smaller panel that will have a maximum voltage of less than my banks rated max voltage this way it can not overcharge the batteries but hopefully bring it up to where the SCC can turn on.

Im trying to think of a way to add a latching relay so the panel is only on when SCC is off

That makes sense but wouldn't you still have to disconnect the load(s) from the battery to avoid feeding the load(s) an unstable voltage and from sucking up most or all of the power?
Do all charge controllers get exclusively powered from the battery side? I remember accidentally connecting a small Victron to PV without the battery connected (something the manual says you shouldn't do) and it turned on at least based on the LED status. But it might not have put out a voltage on the battery side because it first needs to figure out if connected to a 12 or 24 V battery. There might be some charge controllers that don't do that and can be set to your system voltage. Maybe worth some research.

 

[Craig]

That makes sense but wouldn't you still have to disconnect the load(s) from the battery to avoid feeding the load(s) an unstable voltage and from sucking up most or all of the power?
Do all charge controllers get exclusively powered from the battery side? I remember accidentally connecting a small Victron to PV without the battery connected (something the manual says you shouldn't do) and it turned on at least based on the LED status. But it might not have put out a voltage on the battery side because it first needs to figure out if connected to a 12 or 24 V battery. There might be some charge controllers that don't do that and can be set to your system voltage. Maybe worth some research.

That is an option I have not thought of I do have some drok buck converters that can be preset to a constant voltage when they turn on so this could keep the voltage regulated. or even a simple preset 24v buck converter would work. Great Idea

Yes I will be turning off the loads when things get critical. Its just getting my SCC rebooted that is the problem. I do not know of any "MPPT Solar" charge controllers that can turn on when the PV starts putting out energy.

 

[SolarRat]

I do not know of any "MPPT Solar" charge controllers that can turn on when the PV starts putting out energy.

This cheapie turns on with solar input. It's a boost controller so you'll need to use a 12v panel for your 24v battery, which may be a good thing for your idea as you can use tiny panels. It can be adjusted to any voltage and locked in (preset 1 only I think!). To just kick charge your dead battery enough to get your main CC to turn on, I'd hook one of these to two dedicated and paralleled 10-20w or so panels, faced nearly back to back and nearly vertical to shed snow. Obviously bigger panels would be better...but for size/cost concerns I don't think you'd need much.

Even with only a 10w panel, it should give enough surface voltage in the morning or evening (because of the vertical panels of course) to kick on your main CC, but if the main panels are still covered in snow when the CC kicks on...you'll have to figure out what happens and solve any problem that may arise....