Using an AGM battery

[xrated]

@jkwilson I do not think it's marketing. I do believe there is a difference. That difference will get you the maximum life out of your battery.

Is it worth the additional cost to buy a new converter to get a few extra minutes [or life] out of your battery? As cheap as I am, probably not.

@xrated Just because your charger has those settings does not mean the battery manufacturer supports those voltages.

Not trying to start anything. It's best that you educate yourself about your battery and your converter vs asking people what you should do.

Just saying, if you Google AGM charging profiles, they are all over the place. What is right and wrong? Contact the battery manufacturer to get the real facts.

A specific battery chemistry....FLA, AGM, GEL, or LFP all have specific voltage requirements in order to properly charge them....and not overcharge them.....that doesn't change unless the battery chemistry changes....even with a certain groups of battery chemistries.

My DIY LFP battery build, composed of four 3.2V LFP battery cells have very specific characteristics that are considered Maximum and Minimum voltages that the cells must stay within.....just like any other battery chemistry. In the case of LFP, 3.65V is the max that a cell should ever receive when charging. The minimum that the cell should ever be drawn down to is 2.5V. I could, and certainly did research those requirements in the process of building my battery. I also found that a LFP battery is considered to be fully charged at 3.45V/cell....not the 3.65V/cell that is considered the Max. voltage. So in order to find a happy medium for both longevity of the battery/cells..AND...to be able to charge them quickly, there is some middle ground. If all you are concerned about is the fastest charge possible (many people place this as a priority), the you get a charge that provides 14.6 volts to the battery (3.65 volts per cell) and your time spent charging the battery is pretty much at max speed, within the boundaries of the charger amperage, the associated wiring/switches/breakers/etc in the charging circuit. Then, if that charger drops down to 14V for float voltage, the charger will then keep the battery at 14 volts, which is 3.5V/cell.....which is over the amount required to be fully charged. If you are more concerned about the middle ground, you choose a charging voltage that will provide the cells/battery to receive a full charge, but it takes a bit more time to achieve that. I also is not as stressful on the cells/battery, because they never reach maximum cell voltage. Then, when it does finish charging and drop to float voltage, it will also not be keeping the cells above the 3.45 voltage that is considered to be fully charged.

Bottom line in all of this, do what works best for you, but just be knowledgeable about the resulting effects of what you are doing to the battery and how you may be affecting the longevity of it. If none of that matters.....charge it fast and let it rip.

[Soundsailor]

The OP mentioned the Renogy 200 A AGM battery. The specs on their website for that battery seem a lot closer to Lithium than lead-acid.

[Butcher]

@xrated I agree 100%. That is why I think it's weird to ask others what to do. Better to ask what have you all done.

Tomorrow, I will be building my LifePo4 batteries [304v EVE x 2]. I too have looked into charging voltages and what is best. As you found out, they are all over the place. Most have sound advice and some are down right scary. The only way to make the right decision for yourself is to take a few hours learning what your parameters are. The more time you look into this, the better decision you will make.

The other option is to take the factory settings and be fully content that they know what they are doing. You could always sublet the entire job out and have the installer tell you what you need to do.

It sounds like your settings are going to be very close to mine. I'm not looking for something to be the fastest charge or the longest life. Something that I will be happy with. Without I doubt, I do know more now than I did 6 months ago.

To come back to the AGM in question, find out what Renogy likes their batteries to be charged at and find out what your actual converter can do. Contacting Renogy may let you know if you are ok too.

[xrated]

@xrated I agree 100%. That is why I think it's weird to ask others what to do. Better to ask what have you all done.

Tomorrow, I will be building my LifePo4 batteries [304v EVE x 2]. I too have looked into charging voltages and what is best. As you found out, they are all over the place. Most have sound advice and some are down right scary. The only way to make the right decision for yourself is to take a few hours learning what your parameters are. The more time you look into this, the better decision you will make.

The other option is to take the factory settings and be fully content that they know what they are doing. You could always sublet the entire job out and have the installer tell you what you need to do.

It sounds like your settings are going to be very close to mine. I'm not looking for something to be the fastest charge or the longest life. Something that I will be happy with. Without I doubt, I do know more now than I did 6 months ago.

To come back to the AGM in question, find out what Renogy likes their batteries to be charged at and find out what your actual converter can do. Contacting Renogy may let you know if you are ok too.

Hey man, good luck on the battery build. I'm like you, last year at this time I knew very, very little about LFP batteries and had no reason to learn or know about them. Then, because I was going to have JC Refrigeration convert my "Nevercold" over to the twin 12VDC compressor setup, I knew that having enough battery capacity was going to be paramount, since it obviously cannot run on propane or 120VAC.....so I dove in headfirst and started learning about LFP, since that gave me the most capacity usage for the AH size of a battery.

In that learning process, I quickly saw that there is really no need to take them to the 14.6 voltage for charging in my purpose....and I learned that there are other options out there for chargers besides the WFCO and Progressive Industries. I settled on the Mean Well for the reasons stated in a previous post above, and I am 100% happy with it so far. Once I got rid of some of the factory wiring and switches/breakers that were causing me a huge voltage drop when charging, I am now looking at approx. 41 to 41.5 amps out of the charger that has a 43 amp rating. It just doesn't get much better than that. Hopefully you have done a top balance on the cells and maybe even a capacity test to see if they are in fact up to advertised capacity. My load test on my built battery returned a 305AH capacity, and there was a bit more that I didn't "capture" as I have my BMS set to 2.55V for the low voltage cutoff instead of the 2.5V hard bottom.

Holler if you need anything.....I'm certainly not an expert, but I did have a lot of advice from one of the smartest guys I know over on the DIYSolarforum...

[jkwilson]

@jkwilson I do not think it's marketing. I do believe there is a difference. That difference will get you the maximum life out of your battery.

Is it worth the additional cost to buy a new converter to get a few extra minutes [or life] out of your battery? As cheap as I am, probably not.

@xrated Just because your charger has those settings does not mean the battery manufacturer supports those voltages.

Not trying to start anything. It's best that you educate yourself about your battery and your converter vs asking people what you should do.

Just saying, if you Google AGM charging profiles, they are all over the place. What is right and wrong? Contact the battery manufacturer to get the real facts.

I worked for almost 11 years testing batteries and charging systems for the Navy, from submarine batteries to Trident Missile batteries (which don’t charge BTW) The whole idea that a charger even has a profile is false. The data they show is how a battery responds to having a fixed voltage DC supply attached. All of the ramps, current and voltage changes they show are the simple result of the current limit of the charger. Then they act like it’s a feature! It’s not just marketing, it’s complete and total BS.

[xrated]

I worked for almost 11 years testing batteries and charging systems for the Navy, from submarine batteries to Trident Missile batteries (which don’t charge BTW) The whole idea that a charger even has a profile is false. The data they show is how a battery responds to having a fixed voltage DC supply attached. All of the ramps, current and voltage changes they show are the simple result of the current limit of the charger. Then they act like it’s a feature! It’s not just marketing, it’s complete and total BS.

So you're telling me that when you start charging a battery at let's say 50% SOC and the charger's first stage is C/C, which they are, that the voltage is fixed at that time of charging? Not in my experience. As the battery starts taking on a charge and the voltage of the battery is increasing, the voltage from the supply (charger) has to increase in order to keep bringing the charge up...and at that stage, keep the current steady into the battery.

[jkwilson]

So you're telling me that when you start charging a battery at let's say 50% SOC and the charger's first stage is C/C, which they are, that the voltage is fixed at that time of charging? Not in my experience. As the battery starts taking on a charge and the voltage of the battery is increasing, the voltage from the supply (charger) has to increase in order to keep bringing the charge up...and at that stage, keep the current steady into the battery.

Just to avoid clutter, I’ll completely ignore float mode below as it’s the one exception when a charger actively adjust its output.


The voltage output of the charger is set by a regulator. Let’s use 14.6V as a discussion number as it’s common in modern chargers. The regulator setting doesn’t vary, but actual output of the charger is limited by the available current. The charger has no constant current stage. It’s only constant current because the charger is doing everything it can to raise the voltage to 14.6V but doesn’t have enough current to do so. The current stays flat at the maximum current available. It’s running wide open, but can’t get there. As the battery charges, the charger voltage rises slowly because the voltage it’s able to reach at that max current slowly increases. Once the charger can reach it’s fixed voltage, the current begins to drop because it takes less current for a specific charging voltage as the battery charges.

The charger NEVER adjusts output voltage or current during the charging process. Let me emphasize never. It’s actually physically impossible to change either voltage or current because any change in one requires a change in the other unless the load changes, which is what happens over time as the battery charges.

Every change you see in voltage or current is exactly the same as what you’d see if the battery was connected to a 14.6V DC power supply with the same maximum current as the charger. This is because a battery charger is nothing more than a fixed output DC power supply during the charging process.

Any reference to CC or CV mode as if the charger is selecting it is absolute BS. There would be no such thing as a CC period of charging if the charger had sufficient power (and indeed there is no CC period when charging a lightly discharged battery), and the entire charging process would be at 14.6V with slowly decreasing current.

[xrated]

Just to avoid clutter, I’ll completely ignore float mode below as it’s the one exception when a charger actively adjust its output.


The voltage output of the charger is set by a regulator. Let’s use 14.6V as a discussion number as it’s common in modern chargers. The regulator setting doesn’t vary, but actual output of the charger is limited by the available current. The charger has no constant current stage. It’s only constant current because the charger is doing everything it can to raise the voltage to 14.6V but doesn’t have enough current to do so. The current stays flat at the maximum current available. It’s running wide open, but can’t get there. As the battery charges, the charger voltage rises slowly because the voltage it’s able to reach at that max current slowly increases. Once the charger can reach it’s fixed voltage, the current begins to drop because it takes less current for a specific charging voltage as the battery charges.

The charger NEVER adjusts output voltage or current during the charging process. Let me emphasize never. It’s actually physically impossible to change either voltage or current because any change in one requires a change in the other unless the load changes, which is what happens over time as the battery charges.

Every change you see in voltage or current is exactly the same as what you’d see if the battery was connected to a 14.6V DC power supply with the same maximum current as the charger. This is because a battery charger is nothing more than a fixed output DC power supply during the charging process.

Any reference to CC or CV mode as if the charger is selecting it is absolute BS. There would be no such thing as a CC period of charging if the charger had sufficient power (and indeed there is no CC period when charging a lightly discharged battery), and the entire charging process would be at 14.6V with slowly decreasing current.

Does this explanation remain accurate if the charger is utilizing PWM control for the input switching source to the step down transformer.....which would be a resultant change of power to the battery after going through rectifiers and filters?

[jkwilson]

Does this explanation remain accurate if the charger is utilizing PWM control for the input switching source to the step down transformer.....which would be a resultant change of power to the battery after going through rectifiers and filters?

Yes. It’s just a behind the scenes control mechanism.

Another thing I failed to mention is that a converter is more than a charger, but the above applies to the charging function of the converter.

[xrated]

Yes. It’s just a behind the scenes control mechanism.

Another thing I failed to mention is that a converter is more than a charger, but the above applies to the charging function of the converter.

Well, OK....I learned something today. I appreciate the explanation and time you've spent on this. Just goes to show ya, a person is never too old to learn something new.