Author Topic: 48v flooded led acid battery lower max charge voltage good or bad?  (Read 1844 times)

0 Members and 1 Guest are viewing this topic.

fabieville

  • Jr. Member
  • **
  • Posts: 74
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

  • Hero Member
  • *****
  • Posts: 769
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

  • Jr. Member
  • **
  • Posts: 74
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

  • SuperHero Member
  • ******
  • Posts: 2267
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

  • Jr. Member
  • **
  • Posts: 74
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

  • Jr. Member
  • **
  • Posts: 74
Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #5 on: February 19, 2017, 11:11:36 AM »
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

  • SuperHero Member
  • ******
  • Posts: 2267
Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #6 on: February 19, 2017, 06:24:06 PM »
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.

fabieville

  • Jr. Member
  • **
  • Posts: 74
Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #7 on: February 24, 2017, 07:00:06 AM »
If i place a Battery Desulfator Circuit on the battery bank will that prevent sulfation from occuring charging the battery bank to only 57.1v at all times and not performing any equalizing?

Or suppose I place the battery desulfator circuiut on the battery bank and I equalize every once a month will this method give me back my full capacity ready every once a month and prevent long term sulfation from occuring on the battery bank due to the fact the the desulfator circuit is always connected and doing this routine will allow me to get the full life span out my battery bank?

mab

  • Sr. Member
  • ****
  • Posts: 294
  • Country: wales
Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #8 on: February 24, 2017, 12:47:54 PM »
I don't have the same experience as others with flooded deep cycle batteries (I've been using sealed AGM for 10yrs or so), but because you shouldn't push sealed AGMs up to 60v, I found that they do equalise at a lower voltage - but it does take longer.

with my original solar-only setup using 'yuasa endurance' AGMs I never went over 13.8v (12v battery). on long sunny summers days the battery would equalize over several days of sun, but in the winter I would periodically give them a continuous 13.8v over 24hrs (from grid power) to equalise them. nowadays I have hydro as well as solar and equalising isn't an issue despite never taking them over 13.8.

In theory flooded batteries should also equalise at the lower voltage, but having said that, flooded 'traction' deep cycle batteries might require more equalisation than AGM's (I think yuasa literature for my batteries say they make a point of using close manufacturing tolerances to keep the cells matched). I guess for you it depends on how long your battery will have to equalise before you start discharging it again - If you're using solar only and you deeply discharge every day, then you may have to periodically do an equalisation at the higher voltage; if you have wind/hydro and solar you may find they equalise OK when they see an extended period at 57v, especially if you don't deeply discharge every day.

Warpspeed

  • Jr. Member
  • **
  • Posts: 84
  • Country: au
Re: 48v flooded led acid battery lower max charge voltage good or bad?
« Reply #9 on: February 24, 2017, 05:01:43 PM »
One possible solution would be to build a diode voltage dropper for the inverter.
This involves fitting several suitably rated diodes in series, each diode dropping around roughly 0.6v to 1.0v.

The advantage of using diodes is that the voltage drop stays reasonably constant over a very wide load current range. The diodes themselves will need to be large and have sufficient heat sinking. But its cheap, simple and very robust.

As the battery voltage falls during a normal discharge, you can arrange for a power relay or contactor to short out all or part of the diode stack, to restore full battery voltage to the load as soon as it is safe to do so.

This is a system historically used in very large dc emergency lighting systems to ensure the dc bus voltage from the battery never rises high enough to start popping incandescent lamps.  This can be a problem if you are equalising the battery at high voltage and suddenly need to connect the load because of an unexpected mains failure.

If you are powering several hundred incandescent lamps in a theatre or airport runway, you could imagine the damage a significant over voltage wcould cause.

No reason why it could not also be used with an inverter.