Solar Generator - Adding shore power

karlg

New Member
I've search the site but I've not been able to find a post that answers my question, in particular, provides a diagram for best practices in this area.

I'm designing a solar generator and want to have the option to charge the LiFePO4 batteries from shore(house) AC power if it is available, particularly if I'm encountering cloudy days. The generator will be moved around and used for the everyday use cases that other popular solar generators are used for.

1) What is the recommendation for where I should attach the shore power (AC) charger? (besides the obvious + and - of the battery? I don't want to cause a problem with the MPPT)

1a) Can both the MPPT and AC charger be attached at the same time? Or do I need to power down the MPPT to charge with shore power?

Solar Generator Design - Shore Power Question.png

2) Is there a better design that would facilitate MPPT and the use of available shore power to charge the batteries?

Thank you in advance for your thoughts and feedback.

Karl
 

DThames

Photon Sorcerer
Look at this thread. Note that the versions of these "chargers" that will go up to 48v+ have less output current than the similar product that will only go up to 24v+. If you want more amps, get the one that most closely matches your battery voltage.

These are constant current, constant voltage type power supplies. They work fine for LiFePo4 batteries.
 

karlg

New Member
@DThames - thank you very much for your response and pointing me to the thread and the chargers.

Do you know if I have to shut down the MPPT charge controller if I want to engage the shore power/AC charger? I didn't know the additional voltage seen would confuse or worse yet, damage the charge controller.

Thank you!!!
 

sunshine

Solar Addict
I didn't know the additional voltage seen would confuse or worse yet, damage the charge controller.
If the power supply V is below the CCs voltage limit it should only see the PS as another battery and react accordingly.
There may be a problem with the PS when the CCs V output exceeds PSv depending on the PS brand.

I have one of these from their shop on AEx

1500w ZJIVNV set at 12.6v

for 12v lead acid and though diodes. to prevent possible damage to the PS.
Doesn't effect the PWMs
 

12VoltInstalls

Solar Addict
Provided ^^^above is followed, the obvious concern I can imagine is connecting/powering up the charger… I don’t know if that sudden push would rub the mppt fur the wrong way.
 

Porch

Solar Addict
Your best case would be to buy an inverter that has a built in charger. If you are planning to run this off a smaller generator, get one that you can configure to not use more then the X watts your generator makes.
 

DThames

Photon Sorcerer
@DThames - thank you very much for your response and pointing me to the thread and the chargers.

Do you know if I have to shut down the MPPT charge controller if I want to engage the shore power/AC charger? I didn't know the additional voltage seen would confuse or worse yet, damage the charge controller.

Thank you!!!
Short answer, no you can have more than one charger.

Long answer....
For bulk type charging (when battery is down a bit) a charger will look like a current source (current limited) and the battery will look like a load. So the lowest voltage point in the circuit will be at the battery terminals. So other chargers connected to this battery will see the battery voltage as "still needs charged" and do their thing. At some point, the battery voltage will approach the set "charge to" voltage and a CC/CV (Constant Current/Constant Voltage) charger will not charge to a higher voltage (holding voltage at 3.60v/cell or whatever). At that voltage, the battery will slowly take less and less amps for the charger to hold that voltage and we will see the charge current drop toward zero. If you have more than one charger and you try to make them charge to the "exact" same voltage, in real life one will be a tiny bit different than the other and that one's current will rather quickly go to toward zero (when its charge to volts are met) while the one with the very slightly higher voltage setting will then continue on by itself. That is the typical behavior. I had two EPEver Tracers (40a and 60a) on one battery, then replaced those with two Growatt all in ones. In both cases the behavior was as described above.

You might find some oddball charger that will turn off, sample battery voltage, turn back on again, and keep doing at as it nears the end of the charge cycle. I don't think this is typical but I recall seeing that on some small chargers. I don't think it was for a lithium type battery. If you ran into a case like that you might see some odd behavior.
 

karlg

New Member
Short answer, no you can have more than one charger.

Long answer....
For bulk type charging (when battery is down a bit) a charger will look like a current source (current limited) and the battery will look like a load. So the lowest voltage point in the circuit will be at the battery terminals. So other chargers connected to this battery will see the battery voltage as "still needs charged" and do their thing. At some point, the battery voltage will approach the set "charge to" voltage and a CC/CV (Constant Current/Constant Voltage) charger will not charge to a higher voltage (holding voltage at 3.60v/cell or whatever). At that voltage, the battery will slowly take less and less amps for the charger to hold that voltage and we will see the charge current drop toward zero. If you have more than one charger and you try to make them charge to the "exact" same voltage, in real life one will be a tiny bit different than the other and that one's current will rather quickly go to toward zero (when its charge to volts are met) while the one with the very slightly higher voltage setting will then continue on by itself. That is the typical behavior. I had two EPEver Tracers (40a and 60a) on one battery, then replaced those with two Growatt all in ones. In both cases the behavior was as described above.

You might find some oddball charger that will turn off, sample battery voltage, turn back on again, and keep doing at as it nears the end of the charge cycle. I don't think this is typical but I recall seeing that on some small chargers. I don't think it was for a lithium type battery. If you ran into a case like that you might see some odd behavior.
Great - thank you for the more detailed explanation!
 
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