Recommended Battery Voltage

[Mav123]

Hello,

I'm trying to optimize charging-maintenance conditions for standard lead-acid batteries.

There seems to be a variety of options on the recommended maintenance voltage needed for optimal battery maintenance. Newer battery chargers are mostly maintain batteries at 13.1 Volts, but the Battery University suggests 13.5 Volts is the optimal voltage to prevent undercharging regular lead-acid batteries. https://batteryuniversity.com/article/bu-403-charging-lead-acid

I have an older battery reminder 20ten unit that was made before 2014, and it is currently maintaining a battery at 13.5 volts. I called Better Reminder Technical Support and spoke with Dave. He stated that after that date, their newer units are preset to maintain batteries at lower voltages, 13.1 volts.
It seems they've made the changes because the standards set by the federal government had changed, but he couldn't really answer the question of why the standards have changed when the batteries have not changed.

What are your guys' thoughts on the optimal maintenance (storage) Voltage?
Thank you.

 

[ctechbob]

The federal government sets battery charging standards? That's news to me.

 

[Mav123]

According to Dave from Battery Minder. He also mentioned California standards, which puzzled me.

 

[ctechbob]

According to Dave from Battery Minder. He also mentioned California standards, which puzzled me.

Only thing I can find are efficiency standards, which they're apparently attempting to remove battery chargers from those requirements.

https://www.energy.ca.gov/programs-...rogram-outreach-and-education/federal-battery

https://www.energy.gov/eere/buildings/battery-chargers

Either way, I would follow the voltage that the maker of the battery recommends. Usually there are different float voltages for the battery's intended usage.

Is this for a car that isn't going to be driven often?

 

[JimPghPA]

The ideal voltage to charge a 12 Volt flooded lead acid battery at varies with temperature. And temperature of a battery in an engine compartment varies over a very wide range. In summer heat, a battery can be 130f after the engjne has ran for a while. In winter of course it sees the other end of the scale.

Years ago, a friend had a Yamaha 1000 motorcycle with a bad charging system. I built him a voltage regulator to drive the alternator and I set it to regulate at 13.85 Volts. A few years later he told me that it has worked very good. It kept the battery well charged, and did not overcharge it.

 

[SC Maintenance]

I was about to say but @JimPghPA beat me to it - its temperature dependent.

If its 100F out you can probably get away with 2.2V per cell to actually charge - so 13.2V. At -30F its likely closer to 14V. So I would guess 13.1V is a maintain voltage - it won't charge until the battery drops a little. 13.5V would likely charge slowly in anything near or above freezing. And of course, lead acid batteries are never perfect even when new so there is that part also.

The good news is there pretty forgiving, but if your storing at warm temperatures I would take the 13.1V. 13.5V does sound a little high for long term - but as long as you maintain the water in the battery should be fine also.

 

[Mav123]

I do have batteries that are stored right now. Took them from vehicles not driven (regularly).
I agree that the ambient temperature dictates what the float voltage should be. I have come to adopt completely stopping charging stored batteries during the summer months (here, in the PNW). Right now, it is fall with ambient temps in an uninsulated garage about 60°F.

I found another charger that I bought ages ago, Ctek MUS 4.3. It is already "maintaining" a battery at 13.5 Volts (mimicking older Battery Minder 1510). By the way, I recently bought, Battery Minder 128CEC2 to test it out, it was "maintaining" at 13.1 Volts.

 

[Mav123]

I was about to say but @JimPghPA beat me to it - its temperature dependent.

If its 100F out you can probably get away with 2.2V per cell to actually charge - so 13.2V. At -30F its likely closer to 14V. So I would guess 13.1V is a maintain voltage - it won't charge until the battery drops a little. 13.5V would likely charge slowly in anything near or above freezing. And of course, lead acid batteries are never perfect even when new so there is that part also.

The good news is there pretty forgiving, but if your storing at warm temperatures I would take the 13.1V. 13.5V does sound a little high for long term - but as long as you maintain the water in the battery should be fine also.

This is a valid observation, but then that article from the Battery University notes that to maintain the float charge at around 13.5 V.

 

[SC Maintenance]

This is a valid observation, but then that article from the Battery University notes that to maintain the float charge at around 13.5 V.

The better float chargers like CTEK and NOCO claim to have temperature sensors and compensate for temperature. I never checked - would be interesting to see what they do vs temperature.

 

[NA4U]

According to Dave from Battery Minder. He also mentioned California standards, which puzzled me.

I wouldn't put it past our laws in California soon will be regulated on how many craps a day we take

 

[Mav123]

The better float chargers like CTEK and NOCO claim to have temperature sensors and compensate for temperature. I never checked - would be interesting to see what they do vs temperature.

The one I have, MUS 4.3, does not seem to have a temperature probe. That charger has one of its functions as "Cold" charging, which I select when we are nearing 30°F.

I do remember that I plugged Ctek into one of my batteries, and that battery did have issues when the acid would boil out. I left Ctek connected to that battery over the summer, and I noted a significant acid boil over from the battery, so ever since, I stopped charging all my batteries during the summer months.

 

[Mav123]

I wouldn't put it past our laws in California soon will be regulated on how many craps a day we take

Which reminds me, I used to have an operational Battery Tender unit (not to be confused with Battery Minder), the low amperage ones.

I talked with the Technical Support from BT, and over the years, BT discontinued some of the products and began rolling out newer products just for this reason, because California banned the sale of those non-high-efficiency chargers.

Also, recently, Dave from Battery Minder stated that Cali banned the sale of non-high efficiency units they had to "redesign" all of their products.

 

[f355spider]

The better float chargers like CTEK and NOCO claim to have temperature sensors and compensate for temperature. I never checked - would be interesting to see what they do vs temperature.

The Battery Minder temperature compensation works as described in the owners manual. The only thing I notice is the starting point at 77F is lower than they claim in the manual..."Dave" in tech support said they lowered the float voltage due to overcharging experienced by customers. This was done a few years ago...they never updated any of their manuals about this change.

In my garage in winter, I can see temps drop into the low 30s F and float will rise to close to 14vt. In AGM setting it is supposed to start at 13.6 at 77F, but it is closer to 13.4vt due to their change in the startig float voltage. I have seen the voltage float down to 13vt in summer heat in my garage. I have a Bluetooth monitor so I can graph the voltage as it rises in the evening and early morning hours, then drops during the day.

For their "wet" battery setting it is supposed to be 13.4vt at 77F, but in reality they now have the set point at 13.2vt.

 

[Donald]

The Battery Minder temperature compensation works as described in the owners manual. The only thing I notice is the starting point at 77F is lower than they claim in the manual..."Dave" in tech support said they lowered the float voltage due to overcharging experienced by customers. This was done a few years ago...they never updated any of their manuals about this change.

In my garage in winter, I can see temps drop into the low 30s F and float will rise to close to 14vt. In AGM setting it is supposed to start at 13.6 at 77F, but it is closer to 13.4vt due to their change in the startig float voltage. I have seen the voltage float down to 13vt in summer heat in my garage. I have a Bluetooth monitor so I can graph the voltage as it rises in the evening and early morning hours, then drops during the day.

For their "wet" battery setting it is supposed to be 13.4vt at 77F, but in reality they now have the set point at 13.2vt.

Are you describing how Battery Minder has it set or describing a problem?

I have at least 3 Battery Minders. All have temp compensation. So it may depend upon when they were bought as to exactly what voltage they float charge at. Mine are used for boat batteries. So only worried about the cold weather temp compensation. My garage gets cold but hopefully not below 40F.

 

[f355spider]

Are you describing how Battery Minder has it set or describing a problem?

I have at least 3 Battery Minders. All have temp compensation. So it may depend upon when they were bought as to exactly what voltage they float charge at. Mine are used for boat batteries. So only worried about the cold weather temp compensation. My garage gets cold but hopefully not below 40F.

I am only saying the it does not float at the voltages stated in the owners manual. It compensates exactly as described, but the initial set point at 77F it lower than indicated. The amount +- it compensates with temperature change is as described. They claim they lowered that initial set point due to overcharging batteries. This change took place several years ago, but never updated their documentation.

 

[repairman54]

Don't over think it. I've got 9 Battery Minders in play currently. Half old non temp. compensated 1A ones along with 1.5A temp compensated ones also.
-20f winter temps in unheated storage on MC, sleds and OPE. Several over 10 yr. old batteries also.
Just hook'em up and fugetaboutit.

 

[f355spider]

Don't over think it. I've got 9 Battery Minders in play currently. Half old non temp. compensated 1A ones along with 1.5A temp compensated ones also.
-20f winter temps in unheated storage on MC, sleds and OPE. Several over 10 yr. old batteries also.
Just hook'em up and fugetaboutit.

I am not over thinking, worried or describing a problem LOL. I am just offering the observation for others, that the voltages are not as described in the user manual with Battery Minder. The thread title is "recommended battery voltage" and the discussion is about charging and float voltages.

I own four Battery Minders two are the 128CEC2, one 2012AGM and one of the little "wall wart" 1 amp units you are using. I like them very much...well the 1 amp less so...as the temperature compensation is weak compared to the 2012AGM and 128CEC2. Whereas the larger units can compensate up to +1.25vt or -.625vt, the wall wart units compensate maybe +.3vt to -.3vt from what I track with my bluetooth monitor...very mild compensation.