To float charge, or to not float charge: that is the question!

ThreeCW

“To be, or not to be: that is the question:
Whether 'tis nobler in the mind to suffer
The slings and arrows of outrageous fortune,
Or to take arms against a sea of troubles”

If William Shakespeare was part of this forum, he might have been able to provide some good guidance on float charging lead acid batteries.

We see a lot of different chargers available … whether they be for golf carts or automotive batteries … some with and some without float charging capabilities.

I personally “believe” that keeping a light float charge is a good idea to keep my batteries full and ready for the next use (Trojan suggests 2.25 volts per cell … 54.0 volts on a 48 volt system) … but I also used to believe in the Tooth Fairy until I found out that she was more in my imagination than she was real.

And I am beginning to wonder how “real” the float charge recommendation is … and WHERE this recommendation actually comes from?

In my reviews of major battery manufacturer’s websites, I have not found any solid technical evidence or recommendation on float charging.

The Battery University website has an interesting discussion on float charging at: https://batteryuniversity.com/learn/...d_acid_battery

I have attached the chart from the Battery University below which shows after 4 years of a float charge operation, permanent capacity losses of 20% are present in their test case.

Thus begs the question: To float charge, or not float charge?

Attached Images

	Battery University - Float Charging.JPG (79.7 KB, 0 views)
	Trojan Charger Voltage Settings.JPG (55.7 KB, 0 views)
	William S.JPG (72.9 KB, 0 views)

BGW

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scottyb

I'm an advocate of the float charge for lead acid batteries simply because JB taught us that below 90% charge sulfation begins. So if we should recharge at 50% and we sulfate below 90% that leaves a lot of time our batteries are sulfating when they could be ohming like a Buddhist monk.

We recognize Trojan as one of the worlds leading golf cart battery manufactures. This is why we had the Yewy 1200z finish voltage set to 60v and the float charge voltage set to 54 volts to match their optimum recommendations.

ThreeCW

So if you fully charge your pack ... and while it sits waiting for your next ride, it does NOT lose charge to below 90%, then is there any advantage to float charging other than ensuring that your battery is completely topped up when you head out?

Is 60 volts the Finish Charge or the Bulk Charge on the Yewy charger? See the Trojan voltage chart below for reference.

The only thing I could find on any Trojan technical information is on the attached voltage chart that states: "Float Charge (if desired 2.25 VPC)" = 54.0 volts for a 48 volts battery pack.

For comparison, US Battery suggests an "Optional float charge of 2.17 volts per cell for unlimited time" = 52.1 volts for a 48 volt pack". It would be very interesting to see either Trojan's or USB's technical studies on float charging ... does anyone know if that information exists?

I am not aware of any other technical recommendations that say a float charge is actually good for your batteries ... to the contrary, the Battery University information posted earlier seems to indicate it is damaging (20% reduction in storage capacity over 4 years).

I have been float charging my other batteries (automotive, farm and storage) on occasion using my NOCO smart chargers and I am now questioning if it really is a good practice.

Attached Images

	US Battery Charging Instructions.JPG (106.0 KB, 0 views)
	Trojan Charger Voltage Settings.JPG (55.7 KB, 0 views)

ThreeCW

I found the source of the float charging information on the Power Sonic website. Power Sonic manufactures sealed lead acid batteries. Other than being sealed, I believe that this test data should also apply to regular lead acid batteries as the chemistry would be the same.

Figure 10 shows the float service life or life expectancy under continuous charge.

Figure 11 shows how the float service life is affected by temperature ... at a higher ambient temperature, you can expect a lower float service life.

I have also attached the Power Sonic Technical Manual from where this information came from.

Does anyone else know of any test data regarding float charging service life from any conventional lead acid battery manufacturers to compare to?

Attached Images

Power Sonic Float Service Life.JPG (104.9 KB, 0 views)

Attached Files

Power Sonic Sealed Lead Acid Battery Technical Manual.pdf (2.12 MB, 0 views)

Mooncarter

"Oh woe upon storage of direct current; 'tis for minds greater than ours."

MOONCARTER