Multiple Simultaneous Charging - 12v Battery

[ol' boy]

Ok, i'm really interested to hear from some of you solar gurus on this topic

"Having multiple charging devices connected to the same battery and the same time"

Whether that be 2 or 3 Solar Controllers at the same time, or Solar Controllers + Alternator at the same time, or Mains Charging and Solar at the same time.

Reasons you might connect multiple Solar Controllers might be your Solar Array (panels) exceed the Max wattage the Controller can handle
Hence you run 2 or 3 or 4 in Parallel.

At this point the Battery can be looked as a Load with a Resistance value (talking Lead Acid here, but that may be the same for Lipo, i don't know)
The rate of charge would be governed by the resistance in the battery... And the batteries C-rating or Construction limits.

Is the above possible?
Would the charge voltage coming from one device trigger another device to stop or reduce charging?

In the case of 2 Solar Controllers connected in parallel both having the same wattage panel
Would they charge the battery twice as fast (in basic speak) or would they share load based on resistance in the battery
Or would they compete against each other

Is it just simple Ohms Law?

Hence you can stack chargers and solar controllers in parallel to your hearts content so long as you don't exceed the Max charge limit of the Battery?

For this example, lets consider a Lead Acid or LifePO4 12v Battery with a low state of charge which is ready to accept a bulk charge

[Tiny]

Yes it's possible, I have 2 charge controllers on my home batteries.
One is simple, just solar input, dumps power at a user set level which I set just below the smart controllers float voltage to prevent latching & ultimately prevent the smart controller disconnecting due to it's perceived over voltage.
The smart controller has the micro hydro + solar input & does the automated regular float, boost, equalise & absorption cycles.

That's an issue you will have to deal with if you have multiple smart controllers, as they can get cranky if one is trying to do an equalise charge & the other wants to be at float voltage.
I have also had mains charging hooked up at the same time in parallel, but I turn it off before it gets a high enough voltage to effect the smart controller.

IIRC there are some smart controllers that are designed to talk & work with each other. The Midnight charge controller/regulator comes to mind.
My neighbour runs 2 side by side on his large solar array to battery setup.
Yep it says "Internally parallel-able. No extra hub required"

[ol' boy]

Yeah, love the Midnight Chargers Tiny, they seem to be the pinnacle for Home Off Grid set ups
Im more thinking RV, Caravan, Yacht application size gear, but agree the principles should be the same

And my question is a basic hypothetical with consideration to a low state of discharge battery
Getting to the final charge stages i'm not considering for the principle of the exercise (but you make a very good point)

So in your case Tiny, each of the 2 separate charge controllers joined the same battery bank, they can change current output independently of each other?
Even though output circuit voltage stays the same? ie: The Battery terminals

eg: Hyrdo Controller pushing out 20Amps @ 14.7volts, Solar Controller pushing 30Amps @ 14.7v thus the Battery @ 12.4volts (disconnected voltage) can receive 50Amps of charge current at 14.7volts

Or you could have 2 Solar Controllers doing the same thing, for the same example.

Now....

What if you had 1 MPPT Controller and 1 PWM Controller connected in Parallel on the same 12.4v SoC LA Battery?

Same deal? Its just another charging source?
I guess this answers my question

[ol' boy]

So for a practical application of this,
I could have a North East facing PV array and a North West Facing panel array both with their own MPPT or PWM charge controllers
Which would be better than having the same East + West PV arrays connected through the 1 controller

[Tiny]

So in your case Tiny, each of the 2 separate charge controllers joined the same battery bank, they can change current output independently of each other?
Even though output circuit voltage stays the same? ie: The Battery terminals

eg: Hyrdo Controller pushing out 20Amps @ 14.7volts, Solar Controller pushing 30Amps @ 14.7v thus the Battery @ 12.4volts (disconnected voltage) can receive 50Amps of charge current at 14.7volts

It comes down to Ohm's law. V = I R
The battery controls the volts, so the current has to follow the rules.

[hinekadon]

Where on earth are you going to get devices that are the same exact output voltages .
b/s the one with the highest voltage wins over everything else and that will be the charger
until some thing changes and then the other one will take over ,
the output current of the devices has no authority as these are voltage controlled devices so highest WINS

[ol' boy]

Where on earth are you going to get devices that are the same exact output voltages .
b/s the one with the highest voltage wins over everything else and that will be the charger
until some thing changes and then the other one will take over ,
the output current of the devices has no authority as these are voltage controlled devices so highest WINS

When you bolt them together

[george65]

Battery charging is about getting the longest rather than the highest charge.

IE, if you have 2 panels you are better off to point them east and west rather than point both north. The battery will only take so much power so rather than have low ramp up and ramp down and a peak that can't be fully used, one is much better to have a more constant and longer charge than a peaky one.
Standing panels at a 60 o angle east west gives a uniform charge output all year round. Not the same all year round but a constant charge.

Going east west with 2 controllers would also make things easier because one will be dominant for most of the day with only a small equal overlap. They will share the charge but never entire equally. Resistance in wiring and manufacturing tolerance will take care of that but for the most part they will work OK. The other thing is that charging increases the battery voltage. once you take the charger off it will drop.

Not sure but I do see a possibility of 2 chargers actually taking longer than one for the final end charge as they could both back off feeding off one another input. The battery voltage may come up but may not be with enough amp input. Rule of thumb is the last 20% of charge takes 80% of the time anyway so you may never notice.
If the battery is below 50% charge then 2 Chargers may, depending on their rating, be able to supply more charge than one. As the charge and voltage comes up, depending on battery and charger size they may both just be Idling as it were and no faster than one.

Last year I ran a setup with a light in a fridge I was raising seedlings in. I had an LED light powered by 2 Solar panels and a battery charger wired together. During the day the panels put out a higher voltage than the charger so supplied all the power the light bar wanted. As the daylight faded, the charger supplemented then took over for the night. as the sun came up the panels started ramping up again until they took over and so on. On cloudy days the panels supplied what they could and the charger made up any shortfall. Worked VERY well.

Similar setups could be done with batteries.

I have a 2 step on one of my solar Circuits atm. I use a small solar panel ( about 10W) to control the DC diversion to 2 inverters. As they are different orientations, When one is peaking out at mid day, the other doesn't come on full song till later in the afternoon. The small panel switches a DPDT relay that gives the west array some of the DC feed from the north array. this allows other wise wasted power to go to the other inverter on a separate phase. As the sun moves and the peak falls off, the panels shades and with the help of a small bleed resistor the relay switches back all the dc feed to the first phase allowing the second one to put full output back into it's phase.

Depending on how much solar or other power you had, a similar setup could be done to automate input to different generation sources. As you note this will be best for dump charging where you can run max amps into the battery which is up to 80% charge then you have to back off a lot.

There are also battery controllers that multi step charging that are commonly used in marine applications with 24V automotive type alternators. They can turn a 24V alt into a 48V and use a step charge system which is much more efficient than the built in regs. Automotive alts are as efficient as the ones in a power station, it's the regulation that's shit house. Put an external reg on a Leece Nevile alt and you get very good charging and you can program all sorts of charging profiles as well.

[hinekadon]

Yep carry on dreaming the charge rate is made from watts IE the total energy available I defy any one to connect two chargers to one battery
then disconnect one and say the charged voltage has dropped

[ol' boy]

Yep carry on dreaming the charge rate is made from watts IE the total energy available I defy any one to connect two chargers to one battery
then disconnect one and say the charged voltage has dropped

I thought the charge rate was governed by the internal resistance of the battery?
Plus Battery Chemistry and C-Rates.

Hence a connection like the below is possible with each Solar Controller inputing what ever the battery (or Battery and Load) will take during Bulk charging phase.

[Tiny]

I thought the charge rate was governed by the internal resistance of the battery?
Plus Battery Chemistry and C-Rates.

Correct for maximum charge rate, any charge rate below that is free to be varied.

Nice diagram BTW. Good example of combining inputs.
Edit: actually it's technically incorrect as pointed out by hinekadon.
So I modified it to resemble the real world. See below.

[ol' boy]

Nice diagram BTW. Good example of combining inputs.

I guess once the LA Battery has got 80% SoC and the chargers move from Bulk to Absorption and finally Float, things might get a bit tricky with multiple chargers, especially with temperature compensation.
With a LiFePO4 you could just charge on through at 14.4v until the Battery is 95% charged and current rolls off as internal resistance dictates

[hinekadon]

Correct for maximum charge rate, any charge rate below that is free to be varied.

Nice diagram BTW. Good example of combining inputs.

thats not a nice diagram as it in correct as the so called charging systems are not going to regulate any thing as they are all in parrallel and the panels are a mishmash of hope any one who has any electrical knowledge knows that circuit is wrong as the controllers are in series with the charging devices and also different voltages all connected together dont want you doing any wiring for any one ??????

[ol' boy]

thats not a nice diagram as it in correct as the so called charging systems are not going to regulate any thing as they are all in parrallel and the panels are a mishmash of hope any one who has any electrical knowledge knows that circuit is wrong as the controllers are in series with the charging devices and also different voltages all connected together dont want you doing any wiring for any one ??????

Keh? "Controllers are in Series"?

[hinekadon]

bull shvt they are across the battery and across the sources ( OPEN EYES) in the drawing douh!!!!!
diagram belongs in the joke section

[ol' boy]

bull shvt they are across the battery and across the sources ( OPEN EYES) in the drawing douh!!!!!
diagram belongs in the joke section

Looks Parallel connected to me.

Any Series connection would mean an increase in voltage... Pls explain where that is happening.

[hinekadon]

so how is that going to reduce the voltage to do regulation , they can only work if they are in series with the source not in parallel Engage brain please

[Tiny]

thats not a nice diagram as it in correct as the so called charging systems are not going to regulate any thing as they are all in parrallel and the panels are a mishmash of hope any one who has any electrical knowledge knows that circuit is wrong as the controllers are in series with the charging devices and also different voltages all connected together dont want you doing any wiring for any one ??????

Yes, I see what you mean by incorrect, it was drawn a little simple.

This look better.
I'm sure this is what the author meant.

[ol' boy]

Yes, I see what you mean by incorrect, it was drawn a little simple.

This look better.
I'm sure this is what the author meant.

Oh, i thought that was obvious for the point of the exercise
Nicely improved Tiny

Lets hope this one passes the test

[Tiny]

Oh, i thought that was obvious for the point of the exercise

Yes me too!
I can see how the original could confuse some people though, as it was technically incorrect, well spotted hinekadon