Author Topic: Float charge or higher which to use for a valve regulated sealed lead battery?  (Read 1130 times)

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fabieville

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I am using a 24v system and I have (4) EnerSys PowerSafe 12V190F 180Ah valve regulated sealed lead acid battery which I connect in series and parallel so my battery bank is 24v at 380Ah. I am trying to figure out what is the correct max charge voltage it is suppose to get. The specs on each of the batteries says max float charge voltage per cell is 2.29v which works out to be 13.74v per battery and when you double for 24v that works out to be 27.48v.

So should I set the max charge voltage to be always 27.48v on my charge controller?
What if I run down the battery to 23.3v or slightly below 24v sometimes should it still charge up to 27.48v or do I need to go a bit higher sometimes because of the lower discharge?

Does this battery bank require equalization charge sometimes and if yes how often should it be applied and what is the max charge voltage I should use for equalization charge and how long should it remain on equalization charge?

dnix71

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Most of our walk-behind pallet jacks use valve regulated 6V batteries in series to 24v total. A float charge is for standby use. That voltage prevents excessive water loss. Our pallet jacks charge to 28.8 in cyclic use, hard up and hard down. That keeps them equalized, but they don't last very long like that. They dry out after 2 years or so.

If you want to get the maximum life out of your batteries, they need to be charged individually to 14.2v
That won't ionize water in the battery much.

If you run them way down, don't let them sit that way. That leads to hard sulfation. Below 12.4v is where hard sulfation begins, don't let them sit for hours each day at that level and you should be fine.

A parallel/series setup makes it hard to equalize, unless you have a separate charger for each battery.

fabieville

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My charge controller does not allows you to set bulk/absorb then set float voltage.  It just allows you to set the pv cut off voltage and whatever voltage you set it at that's where the charge voltage doesn't pass. It will remain at that voltage sending high current into the battery until the current drops down to a small amount and will start to float at that same voltage. So in my case If i set it at the 27.4v will the battery get a full charge? Also what would be the float current going into the battery that would suggest my battery bank is fully charged? My bank is 380Ah so what current or percentage of the 380Ah going into the battery at 27.4v would suggest it is fully charged?

dnix71

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27.4v is not full and the batteries will get badly out of equalize/balance very quickly. A float charge is a standby charge for occasional use.

fabieville

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So basically if I set my controller to 28.8v is it safe to float charge my value regulated battery at that voltage once the battery temp is @25C or below?

dnix71

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28.4v is the highest you can go without excessive water loss. 28.8v is for equalizing.

At 28.4v your strings will still get out of balance after a while, but you can manually equalize the setup by charging the weaker batteries separately to 14.2. Forklift batteries are treated roughly. They are charged to 28.8v to keep them equalized even though it shortens their life a bit.

If you keep track of individual battery voltage and manually equalize the weaker ones you will get much better life out of your setup.


fabieville

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Charging my current battery bank with my regular PWM charge controller how long should I let the battery bank stay at the bulk/ absorb voltage of 28.8v before I cut it down to 27v for float charge?

Will Regular(most) pwm controllers terminate the Pv cutoff voltage that you set for eg.28.8v and then switch to a lower voltage setting automatically for eg.27.4v and then commence float charging at that lower voltage or will still maintain the high voltage setting that you set but then switch to a lower current charging?

My controller just has one setting in which i set the cutoff voltage and whenever it reaches that voltage setting it remains at that voltage setting and then the current decrease gradually as the battery starts to get closer to the full charge level so in my case the controller won't decrease the high voltage setting once the battery gets full charge and then switch to a float charge voltage for eg. 27.4v unless i manually adjust it at every charge cycle. It just has one cutoff setting which it floats at that same setting.

Is there a way for me to let the controller automatically switch from that high bulk charge/absorb voltage after a certain length of time and then switch to a lower voltage setting to float charge at?

​​​​​​​Or suppose i use a temp sensor (BTS) which attaches to the battery bank will the regular pwm controller ignore the voltage setting that i set and auto adjust the voltage/current once the battery starts to get too warm or too hot or pass the safe temp range?
« Last Edit: September 18, 2017, 10:18:13 PM by fabieville »

fabieville

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If i install a BTS between my current VRLA battery bank which are factory default to float at 27.4v and set my one setting controller to cut the bulk charge at 28.8v which it will begin to float at that same voltage, will the BTS prevent the battery from getting too warm or pass the safe temp range by reducing the current or the voltage or both to a very minimal amount that will prevent the battery from gassing too  much and prevent water loss or go into thermal runnaway at that 28.8v setting?

My controller has a Temp compensation of 4mV/Cell/'C does that indicate that once a certain battery temp is reach, the controller will decrease the charging voltage according to the temp reading and it will even reduce it more if the temp increase again?