Boost charging fully charged battery

[Ampster]

What is reporting "100%"? If it's a charge controller, it's a completely worthless value as it's based on voltage.

Please clarify. I agree voltage is not a useful tool for estimating SOC except at 3.65 volts on an LFP cell. That voltage is a pretty accurate guess that the cell is at 100% SOC. I charge to 3.45 volts per cell and my guess is that I might be 95% give or take a percentage or two.

 

[sunshine_eggo]

User battery config at 13.8 didn't make any difference.

So basically i either have broken batteries or a broken charger? But i dont know which one is broken.

Spikes at 13.8?

Try 13.6/13.6

 

[sunshine_eggo]

Please clarify. I agree voltage is not a useful tool for estimating SOC except at 3.65 volts on an LFP cell. That voltage is a pretty accurate guess that the cell is at 100% SOC. I charge to 3.45 volts per cell and my guess is that I might be 95% give or take a percentage or two.

The "100%" reading on a charge controller is almost always based on lead-acid voltage values and is particularly inaccurate when applied to LFP as LFP take on more capacity at lower voltages.

Per the OP's post, he was using "100%" as an accurate representation of battery charge even though the battery was getting nowhere near fully charged cell voltages and expecting that the "100%" value in some ways influences the charge controllers behavior.

 

[Hauxihaux]

13.6 and 13.4 also spike

 

[sunshine_eggo]

13.6 and 13.4 also spike

Flabbergasted.

Again, this behavior is extremely common with imbalanced cells within a battery when a BMS. Given that these are Battleborn, I would not expect this sort of behavior unless they've been in storage for months.

Do you have a 12V lead-acid battery to try this on?

Do you have a loose connection somewhere?

 

[Ampster]

The "100%" reading on a charge controller is almost always based on lead-acid voltage values

Thanks for the clarification. I agree with your statement in that context.

 

[Hauxihaux]

Thanks again for all of your help. I am happy to report that i seem to have solved the problem, although i am also sorry to say that i seem to have waisted your time.

The problem was a bad connection at the busbar of the charge controller. I think what happened was that i forced the screw too much the first time i hooked the system up. Then, when i disassembled everything to change my setup to parallel instead of in series, what happened was that the wire of the battery somehow went under its prescribed hole in the busbar instead of into it. I noticed the bent busbar when i disassembled my charge controller to see if there was any bad wiring inside. I bent the busbar straight again with some pliers and everything seems to be working fine now. So as you said, the problem was a lose wire. Will even mentions the poor build quality of the rovers busbar as one of its major downsides in his review of it.

Completely my mistake, im sorry to have wasted your time.

 

[sunshine_eggo]

Thanks again for all of your help. I am happy to report that i seem to have solved the problem, although i am also sorry to say that i seem to have waisted your time.

The problem was a bad connection at the busbar of the charge controller. I think what happened was that i forced the screw too much the first time i hooked the system up. Then, when i disassembled everything to change my setup to parallel instead of in series, what happened was that the wire of the battery somehow went under its prescribed hole in the busbar instead of into it. I noticed the bent busbar when i disassembled my charge controller to see if there was any bad wiring inside. I bent the busbar straight again with some pliers and everything seems to be working fine now. So as you said, the problem was a lose wire. Will even mentions the poor build quality of the rovers busbar as one of its major downsides in his review of it.

Completely my mistake, im sorry to have wasted your time.

Glad it sorted! No worries!

It took me until post #25 to suggest connection issues. It's just another example of how I have to keep reminding myself that checking connections is always step one.

 

[Hauxihaux]

Glad it sorted! No worries!

Actually, this morning i noticed that the batteries still werent equalized. So i put them back in parallel to repeat step one of what you told me to do, and to my frustration i had the exact same problem again. Voltage spikes and everything. I triple checked my connections and everything was connected perfectly. Then i suddenly had a realization. My 660w panels are oversized for my controller on a 12v system! So i disconnected one of the panels and charged my parallel batteries on only one panel. And finally it worked! My panels are finally parallel boost charging as we speak.

 

[Hauxihaux]

Im sorry, i just dont seem to be able to let go of this. Now i let the batteries boost charge in parallel for over 2 hours. They were both perfectly equalized at 14.4v according to my multimeter. As soon as i disconnected them to put them back in series, i remeasured them completely unconnected. One of the batteries was still at 14.4v yet the other one immediately dropped down to 13.3v. Somehow its proving impossible to keep them equalized. Why is that?

 

[sunshine_eggo]

Im sorry, i just dont seem to be able to let go of this. Now i let the batteries boost charge in parallel for over 2 hours. They were both perfectly equalized at 14.4v according to my multimeter. As soon as i disconnected them to put them back in series, i remeasured them completely unconnected. One of the batteries was still at 14.4v yet the other one immediately dropped down to 13.3v. Somehow its proving impossible to keep them equalized. Why is that?

It may be that you've found the cause of the spike when in 24V mode. Recommend you try tomorrow, one battery at a time. 14.4V for 30 minutes each. See if either spikes.

 

[Substrate]

Huh, wonder if the Renogy CC has been damaged. They have repeated warnings in the manual about not having the panels hooked up to the CC without the batteries being connected first.

Normally this is sage advice anywhere, (batteries to CC first, and then connect panels last) but the first time I've seen it so emphasized by a manufacturer. Page 02

I suppose it is possible if you've been hooking and unhooking batteries, without disconnecting the panels, that you may have damaged or confused the CC when you reintroduced the batts.

While you may still have other issues, I'd recommend watching for the proper reconnection sequence (batts first, then panels) to the CC if you are troubleshooting.

 

[Hauxihaux]

They have repeated warnings in the manual about not having the panels hooked up to the CC without the batteries being connected first.

I was very careful always to comnect everything in the right order