Battery Equalization

[Jim Burrow]

2 August 2020 – 12 Battery equalization and Voltage (2 batteries)

That I would sure my battery equalization procedure.

Today I thought I would take my (2) 12volt batteries I found in the throw-away/recycle bin out at my local airport to do my MPP testing. I’ve been testing the MPP to see how it will perform under various conditions with respect to the loads that my house on the average draws. – roughly 300 to 5oo watts depending on what I have on and no heavy appliances like a microwave, washer/drier, air conditioner, or heater.

I’m surprised that the batteries are holding up real well since I didn’t bother with voltage and capacity equalization that everyone does with their BMS units.

Starting my battery equalization, (note I’m not using any BMS, just old fashion method) the red battery is holding a voltage of 12.4v, and the blue battery holding at 13.0v with 420 ma going from the blue battery to the red battery.

When the voltage of the two batteries is the same, there should be no current flowing between the two batteries. So, in theory, the two batteries should be in equilibrium or both with the same voltage and capacity. I’m assuming both batteries are 35-ah as I couldn’t read what they were, but they are small for aircraft.

Also, note the only thing that I saw wrong with these two batteries is that they built up pressure inside and the sides bulged out.

Now that these batteries are connected in serious for 24v to my MPP controller/inverter, if one battery can’t hold a charge after a period of time, there will be a major drop in battery voltage.

 

[gnubie]

The sides should not bulge out at all. I can't get a good look at the batteries from your picture but if they are doing that it says your charge rate is far too high causing gassing at a rate the batteries can't cope with via venting. If they are a open cell flooded type remove the caps during equalisation charging.

Keep in mind that an old 100AH battery may well have degraded to 50AH and that's the figure that matters when setting the charge rate not the original 100AH.

 

[Jim Burrow]

The sides should not bulge out at all. I can't get a good look at the batteries from your picture but if they are doing that it says your charge rate is far too high causing gassing at a rate the batteries can't cope with via venting. If they are a open cell flooded type remove the caps during equalisation charging.

Keep in mind that an old 100AH battery may well have degraded to 50AH and that's the figure that matters when setting the charge rate not the original 100AH.

That's how I found the batteries, that is why they were thrown away. but for my testing purposes, as long as they showed 12v and holding, they were good enough for my testing out the MPP. These are aircraft lead-acid 12v batteries.

 

[snoobler]

Equalization? Do you mean trying to get the 12V equal in parallel, or are you actually running an equalization charge on the batteries?

If you have them paralleled together, this is a waste of time. Even when they're at "equilibrium" voltage-wise with negligible current, they won't be "equalized." they will be at different states of charge. The only way this method works is if you are charging while in parallel.

Since I'm not sure what you're trying to accomplish, here's what should be done to maximize performance of the batteries:

1) Fill cells with distilled water just full enough to ensure the plates are covered.
2) Charge each battery individually on a 12V charger.
3) top off each battery to the full line.
4) let sit in float mode for 24 hours.
5) loosen covers/caps so they will freely vent
6) charge to 16.2V and hold.
7) Continue until the sooner of 4 hours or the case raises above 100°F

That's how you "equalize" a battery.

 

[Ampster]

The batterty in front looks like a FLA because of the caps. The one in back that is swelled has no caps so maybe AGM? If that is the case it won't take well to an equalization charge at 16 volts.

 

[Zil]

What Ampster said.

 

[snoobler]

Steps #3 & 5

 

[Jim Burrow]

Equalization? Do you mean trying to get the 12V equal in parallel, or are you actually running an equalization charge on the batteries?

If you have them paralleled together, this is a waste of time. Even when they're at "equilibrium" voltage-wise with negligible current, they won't be "equalized." they will be at different states of charge. The only way this method works is if you are charging while in parallel.

Since I'm not sure what you're trying to accomplish, here's what should be done to maximize performance of the batteries:

1) Fill cells with distilled water just full enough to ensure the plates are covered.
2) Charge each battery individually on a 12V charger.
3) top off each battery to the full line.
4) let sit in float mode for 24 hours.
5) loosen covers/caps so they will freely vent
6) charge to 16.2V and hold.
7) Continue until the sooner of 4 hours or the case raises above 100°F

That's how you "equalize" a battery.

Yes, you are right for doing the equalizing correctly. However, these 2 batteries are ceiled aircraft 12v batteries. They came out of aircraft after the aircraft did their 100 hours required inspection.

These are 2 junk batteries that I found in a throwaway bin. I have no idea what connection they are in other than they look like they have been grossly overcharged based on the bulging out of the cases. I don't care about these batteries once I'm done checking out my MPP and how to set it up. After that, I will throw them away.

Once my MPP testing is over and I am happy with it, then and only then will I spend the $650 to buy the 24V LiFePO4 Powerwall battery that Well Powers tested in his videos. - I don't have a lot of money to blow so I need to spend it wisely - one step at a time.

And my final setup when ready to connect to between my Utility line and my house sub-panel has to fit in a small space and look clean. I can't have tons of components connected together and looking ugly or my wife will not let me install the system.

All I am doing is getting both batteries to the same state of charge with respect to the voltage before charging them back up via the MPP PIP-2424LV-MSD controller/inverter (again another test of the MPP). Once I have the batteries at the same full charged condition, I can continue with my testing with a know condition of the batteries.

Again, I'm not really concern about the health of the batteries, I just want a good initial condition testing point. These 2 batteries are in series to make up a 24v battery pack and will be thrown away back in the recycle throwaway bin at the airport. - I have a hanger out at my local airport and that is how I have excess to the bins.

 

[snoobler]

The only way you can confidently get them to the same state of charge is to charge them in parallel with a 12V charger. Letting them sit there in parallel would take months where self-discharge rapidly overtakes any benefit you get from parallel.

 

[chrisski]

Since I'm not sure what you're trying to accomplish, here's what should be done to maximize performance of the batteries:

1) Fill cells with distilled water just full enough to ensure the plates are covered.
2) Charge each battery individually on a 12V charger.
3) top off each battery to the full line.
4) let sit in float mode for 24 hours.
5) loosen covers/caps so they will freely vent
6) charge to 16.2V and hold.
7) Continue until the sooner of 4 hours or the case raises above 100°F

Getting ready to do my first equalization, so any tips would be appreciated.

When I do this, it will be done with the Victron SCCs at around 10 am when the solar panels can deliver plenty of energy, and that will give me at least 4 hours, clouds cooperating.

I will also be removing the fuses in my DC fuse box since some of the items attached to it won’t like the 16.2 volts.

I notice on your step 5, it says to loosen the caps, but the Trojan Battery users guide says to secure the vents. In your experience, do these batteries bubble so much the vents need to be loosened?

Also, the Trojan Battery guide says to check every hour until the hydrometer readings stop going up, and then its time to stop equalization. I’ll certainly monitor for 100 F.

My batteries measured at pretty close to 1.277 temperature compensated with some a little above, and some a little below, with the biggest difference about .015. I‘m going to check the data again, but the cells closest to the positive cable leading to the bus bar were the weaker ones.

 

[snoobler]

Since you have some below 1.277, you meet the criteria. Timing should follow full charge/float. If you're floating by 10am, that's fine, but don't start before you're floated.

I find it valuable to have before and after SG values to assess the effect of the equalization. I always prefer to do an equalization a day after a full charge and topping off the cells.

Day 1: fully charge, top off cells to proper levels.
Day 2: fully charge, float for 2 hours, check SG, equalize
Day 3: fully charge, float for 2 hours, check SG, compare to yesterday.

Concerning caps/vents, whatever Trojan says is fine. My instructions were generic as I have both Rolls and Trojans, and they have different systems.

Good call on the fuse pull. CO and LP detectors will often squawk above 15V. Some inverters object as well.

 

[chrisski]

My charger allowed me to equalize for an hour at a time, and after the first hour all cells were at a temp adjusted 1.296, so I’m happy with that. Equalizing actually equalized my cells!

I’ll be back tomorrow a couple hours to see if the batteries are closer to the 1.277 Trojan wants.

 

[chrisski]

Two days after equalization all cells were at a temp adjusted 1.296.

The RV has been in the storage with the batteries floating and will get some use in a couple days when we take it out.