Author Topic: 48v flooded led acid battery lower max charge voltage good or bad?  (Read 357 times)

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fabieville

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I see on the internet where most manufacturers recommend a max charge voltage or absorption voltage of 57.6v-58.8v for flooded led acid battery. I have a nova 48v 3000watt 110vac pure sinewave inverter that allows a max of 57.1v input voltage. Because of this i cannot set my charge controller to 57.6v-58.8v according to what most manufacturers said you should charge a 48v flooded led acid battery to.

If I set the charge controller to cut off at 57v or 57.1v which it will go in the absorption stage at that voltage  and then afterwards it will cut down to a float charge voltage of around 54v will I still be able to fully charge the flooded led acid battery? Is there any pros and cons with charging the 48v battery bank at a lower voltage setting than the recommended charge voltage which is 57.6v to 58.8v?

Is charging at the lower voltage setting increase my charging time to fully charge the battery?
is charging at a slightly lower voltage better for the battery?

kitestrings

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Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #1 on: February 14, 2017, 08:53:50 AM »
Fab,

This sounds too low to me, especially if the batteries are in a cool location where the temp comp setting would need to be lower still.  At 59 degF the bulk charge is about 60.5V, and equalization you need to be up around 66V.  Rob B. had some good recommendations a short while back, here:

http://www.fieldlines.com/index.php/topic,148983.0.html

I wonder though, if you could live with this for the daily charge level, but then disconnect the inverter for periodic (monthly) equalization charging.  I assume your charge controller will go higher, but just that the inverter won't tolerate over the 57.1V max, correct?

~ks

fabieville

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Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #2 on: February 14, 2017, 09:19:14 AM »
yes that is correct. Is there a way to increase my inverter input voltage? Most 48v inverters go up to 60v input but mines cannot pass 57.1v . I am hoping for a way to increase it up to 58.8v before it starts to beep.

dnix71

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Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #3 on: February 14, 2017, 03:20:08 PM »
fabieville I wouldn't mess with the HV limit on the input of your inverter. There are elctrolytic capacitors inside that will leak/explode if you go to much over their limits. I had 2 versions of BZ brand charge controllers. The limits on panel input were 50v and 100v. You got what you paid for, the limits were there to protect the internals.

A 12v flooded lead acid battery is 12.6v at rest and at 14.2 has to begin hydrolysing water. 14.2v x 4 = 56.8v
Equalizing a string of 4 batteries is pretty hard to do without cooking off the weakest cell in the string.

I can tell you from experience with forklifts that you need over 30v to equalize a 24v nominal stack. Careful charging and lots of water. But with a 48v nominal stack you will need over 60v to equalize and over 60v in the US means you are no longer dealing with "low voltage" from a legal/national electrical code point of view. That is probably why the limits on your inverter are set that way. One less certification to pass for the manufacturer. 60/57.1 = 1.05 Assuming a 5% margin of meter error in reading the voltage if the limit is set at 57.1v you won't go over the 60v limit.

fabieville

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Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #4 on: February 17, 2017, 03:05:42 AM »
If I use the same low voltage of 57.1v for the cutoff voltage for the charge controller and the battery starts to charge going through the normal stages: bulk, absorb and then reaches a point where the float charge current is now charging at 1% of the battery bank amps capacity, would this suggest that the battery bank is completely charge? And in that case would the SG of the cells always be in the full charge stage/normal level whenever the charging stops and the battery comes to the rest voltage?

Would this prevent electrolyte from stratifying once the battery SG reading is showing normal level for all the cells when you check them at the rest voltage?
Would you still need to equalize the battery bank even thou the battery bank has got a full charge at least once in less than one week? or in less than 2 weeks?
Would you still get maximum capacity and avoid sulfation on the negative plate once you manage to get full charge for the battery at this low voltage setting?
Would you manage to get full charge for the battery at the same low voltage below room temp once you have high amps kicking into the battery most of the time from an oversize solar array?

Therefore if you oversize on you solar array so that you can get full charge and get the SG readings for the cells in the normal level most of the times then these limitations would not occur charging at the low voltage setting all the time
"Slow charge time; capacity readings may be inconsistent and declining with each cycle. Sulfation may occur without equalizing charge"

Am I correct?


Is there a way to disable the OVP on the inverter instead of adjusting it?
« Last Edit: February 17, 2017, 11:08:44 AM by fabieville »

fabieville

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If I disable the ovp I don't think the inverter will fry. The Labelling and the specs shows that it can
Handle 42-60v input. I am just wondering if is the manufacturer limit it to 57.1v. The voltage during charging won't pass 58.8v. The charge controller will limit it from going any further. So is there a way to disable the ovp instead of adjusting it?

dnix71

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The 57.1v limit is for legal reason's. It's 60v - 5%.
If you fail to equalize the string it will appear to be fully charged, but the string capacity will drop and sulfation will occur.