Solar charge controllers

ELI5, please, why a buck/boost module couldn't or shouldn't be used to regulate voltage of a solar panel instead of a 'charge controller'

Charge controllers come in PWM and MPPT types, where would a buck/boost module fall in terms of efficiency?

INTP: ELI5, please, why a buck/boost module couldn't or shouldn't be used to regulate voltage of a solar panel instead of a 'charge controller'

Charge controllers come in PWM and MPPT types, where would a buck/boost module fall in terms of efficiency?

Hmmm. This appears top be an orphan posting. We used to build hundreds of the PWM types. All charge controllers will STOP trying to charge when the battery voltage shows charge is complete and will STOP trying to charge when the solar panel input is too low. A buck/boost module will continue to TRY to charge forever.

Paul

Guess that leads back to my other thread about dumb chargers- voltage potential automatically stops charging, so if input voltage matches battery voltage, there isn't any movement to quantify this 'keeps trying to charge' idea. And even if so, isn't that a trickle charge that makes up for the constant slow self discharge of the battery?

Oh, I didn't mention a battery. I have one of these bad boys and was duly assuaged by the store clerk that the SLI in the part number is an oops by their naming convention and not a naming used by Duracell- I.e., it's not an SLI battery.

It'll do just fine getting charged by my alternator. But I'm planning for days where I'm camping and not driving, and solar panels may come into consideration.

So previously, I asked what the harm is in having the alternator constantly 'try' charging the second battery while driving. The results seemed to indicate that there was no harm. When voltage matches, current is nil-ish.

So that'd be the case with a solar panel run through a boost/buck- if the converter was set to something like 14.7V, then once the battery is full, the converter isn't passing anything.

Right? or not right?

INTP: Guess that leads back to my other thread about dumb chargers- voltage potential automatically stops charging, so if input voltage matches battery voltage, there isn't any movement to quantify this 'keeps trying to charge' idea. And even if so, isn't that a trickle charge that makes up for the constant slow self discharge of the battery?

Oh, I didn't mention a battery. I have one of these bad boys and was duly assuaged by the store clerk that the SLI in the part number is an oops by their naming convention and not a naming used by Duracell- I.e., it's not an SLI battery.

It'll do just fine getting charged by my alternator. But I'm planning for days where I'm camping and not driving, and solar panels may come into consideration.

So previously, I asked what the harm is in having the alternator constantly 'try' charging the second battery while driving. The results seemed to indicate that there was no harm. When voltage matches, current is nil-ish.

So that'd be the case with a solar panel run through a boost/buck- if the converter was set to something like 14.7V, then once the battery is full, the converter isn't passing anything.

Right? or not right?

First, your alternator has a voltage regulator built into the alternator. Has been that way for quite a number of years. It senses the voltage on you battery before allowing the DC from the rectifiers to charge the battery. My truck has two 12 volt batteries charged by the alternator, so if your alternator can produce enough power to charge two batteries, you are good to go.

The problem with charging batteries from a solar panel without using a controller is when the panel power (voltageXcurrent) is not enough to drive the boost/buck converter, then what? Does it allow the battery to discharge?

Is there a set point on the boost/buck to cause it to stop trying?

Solar charge controllers are so cheap, I wonder why you are concerned? Also, years ago, there were ICs that controlled the whole solar charge process. Look into building something with one of them.

Paul

This is about learning. I will buy a charge controller as like you say, they are inexpensive, and they do have a good amount of info on readout.

Just wondering for the sake of wondering and learning. The charge controller bucks and boosts, so I just drew the conclusion of using a buck/boost.

I suspect it may limit current based on battery type, which isn't native option on the standardish hobby grade buck/boost converters I have in mind.

Car battery can be charge safely by current 1/10 of it capacity, in your case 10.5 A, so use 14.4V from your solar and current limiter 10A.

Nah.

INTP: voltage potential automatically stops charging, so if input voltage matches battery voltage, there isn't any movement to quantify this 'keeps trying to charge' idea.

I've wondered about that too. I suspect that efficient charging requires a voltage considerably higher than the target voltage for the battery, which would of course damage the battery once the battery has reached full charge. I'm curious about how well the battery would charge if, as you propose, it's charged by a source that's fixed at the target battery voltage.