Boost charging fully charged battery

[Hauxihaux]

Hello,

Yesterday i finally installed my first pv system. At first everything seemed to be working perfectly, but slowly im beginning to doubt the correct functioning of my renogy rover 40a controller.

The first red flags came up when i noticed that the battery state of discharge didnt seem to be working properly. I have two 12v 100ah battle born batteries wired in series. Even after putting on some test loads of a full washing machine cycle and some jigsaw work the battery never discharged more than 90%. This on a super cloudy and rainy day. According to my controller, it took the battery about 10 minutes to reach 100% charge again (i have 660w on the roof).

Now, whats confusing me even more, is that the charge controller has jumped into boost mode twice in a row, despite indicating the battery as fully charged. Is this normal? At the same time the over voltage error started coming up on the display for a few minutes before disappearing again.

Im worried something is working incorrectly and that i might be harming some of my system components

 

[sunshine_eggo]

Hello,

Yesterday i finally installed my first pv system. At first everything seemed to be working perfectly, but slowly im beginning to doubt the correct functioning of my renogy rover 40a controller.

The first red flags came up when i noticed that the battery state of discharge didnt seem to be working properly. I have two 12v 100ah battle born batteries wired in series.

Did you individually charge each battery and then in parallel to full before putting them in series? Do you have a plan to monitor and rectify imbalance between the batteries per the Battleborn manual?

Even after putting on some test loads of a full washing machine cycle and some jigsaw work the battery never discharged more than 90%. This on a super cloudy and rainy day. According to my controller, it took the battery about 10 minutes to reach 100% charge again (i have 660w on the roof).

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

Your Battleborn is charged after it's been held at 14.4V for about 30 minutes, not when the charge controller says, "100%."

Now, whats confusing me even more, is that the charge controller has jumped into boost mode twice in a row, despite indicating the battery as fully charged.

Again, if charge controller is reporting 100%, it's a meaningless number.

Is this normal? At the same time the over voltage error started coming up on the display for a few minutes before disappearing again.

Over-voltage may be caused by one of the two Battleborn batteries' BMS entering high voltage protection mode due to imbalance between the batteries because you didn't fully charge them as described above. When this happens, the battery immediately cuts off charge, and most of the time, charge controllers can't react quickly enough, so they spike.

Im worried something is working incorrectly and that i might be harming some of my system components

Individually charge each of your 12V batteries to 14.4V AT the battery terminals.
Place them in parallel and charge them to 14.4V AT the battery terminals and hold for 2 hours.
Place them in series and assess.

 

[Hauxihaux]

Thank you for your super quick answer.

Did you individually charge each battery and then in parallel to full before putting them in series?

No, I didn't know i was supposed to Do that. Can i still Do that now or is it too late. Did i hurt my batteries?

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

Yes, this is just based on what my controller is telling me.

 

[sunshine_eggo]

Thank you for your super quick answer.

No, I didn't know i was supposed to Do that. Can i still Do that now or is it too late.

Yes.

Did i hurt my batteries?

No.

Yes, this is just based on what my controller is telling me.

Ignore it. It can only cause confusion as demonstrated by your post.


The top 3 battery monitors on this page provide an accurate means of reporting true % charge:

Off-grid Solar Battery Monitors

Building a vehicle mounted solar power system? Let me help.

www.mobile-solarpower.com

 

[Hauxihaux]

Sorry for the double post before.

So i tried doing what you told me to do. I first disconnected the panels from the controller. Then i disconnected one of then i disconnected the batteries from each other and hooked the controller up to one so gle battery. Now i get the ACr error message on my controller. Cant do anything anymore. Pv is completely disconnected.

 

[sunshine_eggo]

Sorry for the double post before.

So i tried doing what you told me to do. I first disconnected the panels from the controller. Then i disconnected one of then i disconnected the batteries from each other and hooked the controller up to one so gle battery. Now i get the ACr error message on my controller. Cant do anything anymore. Pv is completely disconnected.

If you plan to use the Renogy, you may need to change the configuration to 12V before disconnecting from 24V. if it has an "auto" setting for determining system voltage, that's probably best.

Given that solar isn't 100% reliable, in these cases, most would opt for an AC charger to charge the 12V to full.

 

[Hauxihaux]

Thank you so much for your help. Really! Ok, so now the error message disappeared. I was able to switch to 12v and hooked the panels back up. I am off grid so I guess i dont have another good option to fully charge my batteries than solar. Can i rely on my controllers indication of battery voltage when it has reached the required 14.4v?

 

[sunshine_eggo]

Thank you so much for your help. Really! Ok, so now the error message disappeared. I was able to switch to 12v and hooked the panels back up. I am off grid so I guess i dont have another good option to fully charge my batteries than solar. Can i rely on my controllers indication of battery voltage when it has reached the required 14.4v?

I would confirm that it's reasonably accurate by checking battery terminal voltage with a separate meter.

Since you're dealing with solar only, skip to the parallel step. Parallel them, set boost to 14.4V and boost duration to 120 min. Make sure you attach your charge leads to opposite battery posts, i.e., (+) on one battery and (-) on the other battery.

 

[Hauxihaux]

Will do so as soon as we get daylight tomorrow morning.

Do you have a plan to monitor and rectify imbalance between the batteries per the Battleborn manual?

What would be a good plan to stay on top of this in the future?

 

[sunshine_eggo]

Will do so as soon as we get daylight tomorrow morning.


What would be a good plan to stay on top of this in the future?

Read the Battleborn manual to familiarize yourself with their recommendations.

This device will monitor the individual 12V and MOVE charge from the higher voltage one to the lower voltage one:

KiloVault Battery Balancers

KiloVault Battery Balancers help extend the life of a battery bank in your solar power system. 24V and 48V versions are used to maintain battery voltages across a series connection of batteries.

www.altestore.com

This should help maintain the balance of the individual 12V to the point that you never need to worry about it.

ensure that your batteries are regularly charged above 14.2V and held there for a couple hours at least a couple times a month. Battleborn BMS don't balance at lower votlages.

 

[Hauxihaux]

Today i did as you recommended me to do. I paralleled my batteries and am attempting to charge to 14.4v. Everything seemed to work fine for a couple of hours, but at 13.5v charging suddenly stopped. My multimeter confirms 13.5v at the battery terminals. Did the charge controller stop charging because it considers my batteries to be full?

 

[sunshine_eggo]

Today i did as you recommended me to do. I paralleled my batteries and am attempting to charge to 14.4v. Everything seemed to work fine for a couple of hours, but at 13.5v charging suddenly stopped. My multimeter confirms 13.5v at the battery terminals. Did the charge controller stop charging because it considers my batteries to be full?

I've been assuming the controller is configured to charge to 14.4V and 2 hr boost time. Confirm that.

I would:

disconnect the PV from controller
disconnect the battery from controller
reconnect the battery to the controller
reconnect the PV to the controller

This should restart the charging.

If it terminates prematurely again, the batteries may be engaging in charge protection, or it could be some other charging time limit I'm not aware of.

 

[Hauxihaux]

I unplugged and reset everything. Nothing changed. I cant find out how to set the controller so that it will charge to 14.4v. I seem to only be able to edit boost, float, equalization, under voltage and voltage recovery.

Observing the monitor of the controller for a while, i see that every minute or so it jumps into boost for a millisecond, then voltage spikes and then it settles at 13.5v again without charging.

 

[sunshine_eggo]

I unplugged and reset everything. Nothing changed. I cant find out how to set the controller so that it will charge to 14.4v. I seem to only be able to edit boost, float, equalization, under voltage and voltage recovery.

Observing the monitor of the controller for a while, i see that every minute or so it jumps into boost for a millisecond, then voltage spikes and then it settles at 13.5v again without charging.

hat may be a sign that BOTH batteries are engaging in over-voltage protection, but I would not expect that from Battleborns.

Assuming it's this one:

https://www.renogy.com/content/RNG-CTRL-RVR40/RVR203040-Manual.pdf

Just set it for sealed:

 

[Hauxihaux]

Yes, this are the settings from the manual i have.

Setting it to sealed doesnt change anything. Still, i can see that the panels are connected and producing power, yet the charger isnt passing on voltage to the battery. Boost gets turned on for a moment yet turns straight off again. Then there is the voltage spike and it resettles at 13.4 (not 13.5 anymore).

Im starting to wonder if maybe i am making a problem out of nothing? Could it be that my batteries actually are fully charged and i can switch them back to in series and just regularly use them with my inverter?

 

[Hauxihaux]

The voltage spike after going into boost mode spikes all the way up to 15.5 though, so maybe the battle borns do go into overvoltage protection? Yet this still doesnt explain why its not just charging regularly..

 

[sunshine_eggo]

That really sounds like BMS over voltage protection (OVP), and it shouldn't be happening at 13.5V. I'd contact battleborn.

 

[Hauxihaux]

After the charger attempts to boost charge the voltage spikes all the way up to 15.5v. wouldnt itbe normal for it to go into over voltage protection then?

 

[sunshine_eggo]

After the charger attempts to boost charge the voltage spikes all the way up to 15.5v. wouldnt itbe normal for it to go into over voltage protection then?

When you say SPIKE, that refers to a near instant increase in voltage. That shouldn't happen. The charge controller should charge to 14.4V, hold that for two hours and then drop to the float voltage and hold that.

The only way a spike can happen is:

1) Failed charge controller.
2) Battery cuts itself out of the circuit and the charger is suddenly charging nothing and can't pull back the voltage/current quickly enough.

Try a USER battery config with boost and float at 13.8V

 

[Hauxihaux]

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.