How does converter sense battery state of charge?

[Wellibe]

New-to-me 2018 Arctic Fox 27-5L. I'm doing lots of odds and ends trying to get this rig ready for possible full time living by April.

Question of the day relates to the converter (Progressive Dynamics Inteli-Power 9200 series, model PD9260C).

How does the converter sense battery state of charge so that it knows when to be in boost mode (14.4v) vs normal mode (13.6v)? I've read the manual and various other things on line that talk about the charge wizard continuously reading voltage, but I can't find any information on how it reads voltage. As in, what wires, connections, fuses, or other components are involved in case I need to troubleshoot a problem with the converter not selecting the correct charge mode?

O.K., here's the long background story, which you can skip if you're not interested.

Yesterday I did a really stupid thing and ended up shorting the positive battery terminal to the metal frame around the battery bay door opening. The rig was not connected to shore power at the time, and the battery shut off switch was set to off. Sparks flew, so I'm pretty sure that battery shut off switch doesn't actually shut everything off. I stopped the shorting within a second or two, then disconnected the negative battery terminal and fixed the bone-headed mistake that caused the short. I reconnected the batteries (two FLA 6v GC2 batteries), turned the shut off switch to on, and connected to shore power. Lights and fans worked, so I figured I dodged a bullet.

A few hours later I looked at the solar charge controller and saw that it was indicating a battery voltage of 14.5. I checked terminal voltage at the batteries and confirmed 14.47v. I thought that was odd since I had been connected to shore power for a week or more prior to this, so the batteries should have been fully charged and the converter should have been in normal mode. So I unplugged shore power, turned off the battery switch, and disconnected batteries at the negative terminal, and left it that way overnight. Terminal voltage this morning read 13.21 with everything still disconnected, so clearly the batteries were more than fully charged.

I checked every 12v blade fuse that I could find. Found one 3A fuse for the propane leak detector that was blown, which I suspect was pre-existing because I had previously discovered that someone cut the wires to the detector. I also found a blown 15A fuse on one of the panels next to the converter (two large positive wires come out of the converter and go to a small fuse panel next door, where the current gets divided into multiple smaller wires). I have no idea what the blown 15A fuse went to. The three fuses on the converter itself were fine.

I replaced the blown fuses and did the voltage check procedure that I found on a Progressive Dynamics web page. That involves disconnecting the large 12v negative wire, turning on shore power, and then checking output voltage via the positive and negative terminals. Output read 13.7v. The spec is 13.6, but I figured that's pretty close.

So I shut off shore power again, reconnected the negative wire on the converter, reconnected the batteries, turned the battery shut off switch to on, and plugged back into shore power. Now the solar controller is showing battery voltage as 13.7, same as the output I measured from the controller.

So the controller seems to have regained its composure and is now running in normal mode with the fully charged batteries. Hopefully I didn't fry it, but just in case it acts up again, I'd like to know if there is anything else I can do to troubleshoot.

Sorry for the long saga. Thanks for bearing with me.

[Sunnyfalls]

Currently camping and don't have the Progressive Industry manual for our charger/converter with me. But going from memory, it uses voltage and change in voltage with time to determine the charge profile to use. It also starts out out in bulk charge profile when first turned ON. And we have a remote pendent that enables seeing what charge profile is currently being used and then manually change the charge profile as desired.

Gayle & Bob
"Los Gatos Casita"

[NoviBill]

The battery disconnect - is normally connected to the Positive cable between the battery and the Converter and distribution box. So the terminal on the battery will always be hot and the trailer will always be connected to ground.
*If it's a stupid move almost everyone who has ever worked on a car/RV is guilty. Don't ever try to grab a wrench that falls between the termials. Just trust me on that...

I don't know anything about your converter...\
How a charger/converter detects state of charge (SOC) depnds. Most use voltage and sometime a small resistance (load). This can be used to detect both the SOC and battery type (95% of the time). Nearly dead LifePo4 look a lot like a LA battery and can cause some converters to miss identify.

[Mark_K5LXP]

It's a combination of voltage setpoints, time and assumptions. All things being correct, it will follow the prescribed stages per their pendant documentation:



You get what PD decided is the appropriate charge profile but the pendant offers an option to manually select the charge mode, so that's what makes their product somewhat unique and more useful when operation isn't typical.

Mark B.
Albuquerque, NM

[d23haynes57]

For lead acid batteries chargers do not set charge cycle on existing state of charge. If you cycle power off, when powered back on it will go to normal IEI profile and voltage will build again until current drops and then the forced current absorption cycle, up to 3 hours will go again. This over 80% is a charge cycle. Same as going below 50%. If you have solar it is possible that the solar is doing the same thing everyday.
For the charger you have it is also a power supply. It will hold the voltage at float and carry the load up to the current that is available. If the load is such that it does not keep up and the battery voltage drops below ~13.2 for some period of time, it will also start the charge cycle again.

[SafariBen]

I can't speak to that converter specifically, but typically chargers use amperage to set voltage between bulk, absorption and float.



A small one that's labeled will put out 6A until the battery reaches 14v, then maintain 14V until the amperage drops below 1A, then will drop to float voltage of 13.6 or so. That's bulk, absorption, and float stages, and how they are determined.

[traveldawg]

So... the short answer is... the voltage (bulk, absorbstion, float) is controlled by how much current the battery draws during each mode?????

[twinboat]

Originally Posted by traveldawg

So... the short answer is... the voltage (bulk, absorbstion, float) is controlled by how much current the battery draws during each mode?????

No, the battery doesn't draw current, the charger forces it into the battery.
It forces current in until bult voltage is reached and then backs the current down until the voltage drops to absorb voltage. It runs thru absorb time and drops to float voltage as long as the battery is on the charger or you put a load on the battery that's more then the converters output.

[traveldawg]

I looked at my Xantrex Freedom 2000 XC Inverter/Charger. This is what it reads....

Bulk charge is the first stage in the charging process and provides the batteries with a controlled, constant current. Once the battery voltage rises to the absorption voltage threshold, the charger switches to the absorption stage.

During the absorption stage, the Freedom XC begins operating in constant voltage mode and the current falls gradually as the amp hours are returned to the battery.

The Freedom XC transitions to the float stage if either one of the following two conditions are met:
1. The charge current allowed by the batteries falls below the exit current threshold, which is equal to 10% of the programmed charge current and a minimum of 2A.
2. The Freedom XC has been in absorption for the programmed maximum absorption time limit. The default is 6 hours.

So now I know how my unit works (I think).... Bulk state at up to 80 amps until it reaches 14.5v; then it absorption stage at 14.5v until it senses it is outputting 8 amps (10% of my charge current) or 6 hours has elasped; then it drops to float stage at 13.8 volts.

Having done all that, I looked up the owners manual for the PD9260C (no longer in production) and found this...

9200 - The full rated load is available for load, battery charging or both. When charging the battery, the converter has a nominal voltage output of 13.6 VDC for 12 volt models and 27.2 VDC for 24 volt models. The system will sense voltage on the battery and automatically select one of three operating modes (normal, boost and storage) to provide the correct charge level to the batteries.

BOOST MODE: If the voltage drops below a preset level the output voltage is increased to approximately 14.4 VDC (28.8 VDC for 24 volt models) to rapidly recharge the battery.

NORMAL MODE: Output voltage set at approximately 13.6 VDC (27.2 VDC for 24 volt models).

STORAGE MODE: If there is no significant battery usage for 30 hours the output voltage reduces to 13.2 VDC (26.4 VDC for 24 volt models) for minimal water usage. In storage mode, the output voltage increases to 14.4 VDC (28.8 DC for 24 volt models) for approximately 15 minutes every 21 hours to help prevent sulfation of the battery plates.

Now I've learned a bit and hopefully the OP sees what his converter does.

[Wellibe]

Thanks for the discussion folks. I've read the manual for my converter and I understand what it says about sensing voltage and selecting the appropriate charge stage based on that voltage. But what it doesn't tell me is how it senses the voltage. So if it seems inappropriately stuck in the bulk stage when I know the batteries are fully charged, I've got no way of troubleshooting.

My understanding of electrical systems is rudimentary at best, but as I understand it, there is a wire that carries current from the converter directly to the battery. Battery terminal voltage (surface charge) will quickly rise to match the converter's output voltage, so it seems unlikely that the converter is actually sensing battery voltage. Seems more likely that it is inferring the battery's internal voltage based on how much current it is able to push to the battery at a particular output voltage. Which suggests that the microprocessor in the converter is actually keeping track of amps pushed.

If that is the case, unfortunately it still doesn't help me with troubleshooting, as it suggests that getting stuck in bulk mode is an internal computer error. Which I have no hope of troubleshooting and repairing myself.

[Bill Gail]

The pendant prior posts refer to is the Progressive Dynamics Charge Wizard .
It plugs into a port on the converter and provides constant monitoring of the current charge program and provides the ability to manually change the charge program. After manually changing the program and it completes the program chosen , it will automatically go back into auto monitoring .
I have one connected to our converter and it's nice to be able to see the charging program at a quick glance .
The Wizard is available on "A" large online seller for around $20 .

[SafariBen]

Originally Posted by Wellibe

... it seems unlikely that the converter is actually sensing battery voltage. Seems more likely that it is inferring the battery's internal voltage based on how much current it is able to push to the battery at a particular output voltage. Which suggests that the microprocessor in the converter is actually keeping track of amps pushed...

Yes, many chargers MEASURE amps to change to float at the appropriate time. Most would not KEEP TRACK of amp hours, as lead wastes power, amps at volts is a better measure of state of charge.



Battery voltage and charger output voltage are the same thing. The cables have low enough resistance that .1V difference is irrelevant. You're way overthinking this. The batteries voltage will drop once the charge current stops, that is built into the charge protocol.

[Wellibe]

Originally Posted by Bill Gail

The pendant prior posts refer to is the Progressive Dynamics Charge Wizard .
It plugs into a port on the converter and provides constant monitoring of the current charge program and provides the ability to manually change the charge program. After manually changing the program and it completes the program chosen , it will automatically go back into auto monitoring .
I have one connected to our converter and it's nice to be able to see the charging program at a quick glance .
The Wizard is available on "A" large online seller for around $20 .

Based on what I read it seems like the charge wizard is internal to the converter and is the component that makes the decisions about what stage to apply. The pendant allows the user to see and control what the charge wizard is doing. At least that's how I read it.

I didn't see a port for plugging in a dongle on my charger. Either it doesn't have the option, or I'm not looking in the right place.

[Wellibe]

Here's a related question for those who know something about electricity.

Does the voltage of the 120v input have any effect on the voltage of the 12v output? I ask because my output voltage was hovering at 13.7-13.8 all day yesterday, instead of the specified 13.6. The 20A shore power circuit that I'm plugged into consistently runs 128-130v when no load is applied. I'm wondering if the 120v source running a bit on the high side might cause the 12v output to also be a bit high.