Charging and SOC

[Mobilesport]

When I'm charging my batteries with a battery charger and my amps start to taper , does that give me a indicator of what % of state of charge my batteries are at?

For example would 50 amps mean 40% charged 
                                    45 amps mean 55% charged
                                      40
                                       35
                                        30 amps 75 % charged
                                         25
                                          20 amps 85 % charged
                                           15
                                            10
                                              5  amps    95% charged
                                               0 amps fully charged
If so is there a chart I could download ?
 could of swere I saw something like that

 

[SternWake]

Nope.

Generally. perhaps but it depends on the batteries being charged

Once batteries get to absorption voltage then amps start tapering.

One would need to be able to achieve absorption voltage instantly, That might require 120 amps on a healthy pair of 6v gc-2.

When my 40 amps reaches absorption voltage, how fast the amps taper depend on way too many factors for their amperage acceptance to ever equate to a state of charge with more than 60% accuracy.

YOur interest in this can be satiated by experimenting.  It is how I learned.

Check SG as you charge.  Keep records tracking voltage at battery terminal, amps flowing into battery( subtract DC loads present) and specific gravity.

Since you never get them to 1.280 such an experiment will only really be valid on batteries in the same state of health as yours are now

 

[Optimistic Paranoid]

I think you are confusing amps and volts.  There are charts that show ROUGHLY what the resting voltage is at different SOC.

A smart charger operates in three stages. 

In the first, or bulk stage, it is a constant amperage charger.  That is, it will put whatever it's maximum amps is into the battery bank until the batter voltage rises to it's set point.  This might be 14.4 volts or it might be higher.  It might be locked in by the manufacturer, or you might be able to change it.

Anyway, once it hits it's set point, it becomes a constant voltage charger.  It sees to it that the battery voltage goes no higher than that, and it does that by cutting back on the amperage.  Eventually, the amperage falls to the point where the charge assumes the battery is fully charged, and it goes to it's third, or float stage.  The voltage will drop to something like 13.4 or 13.2 and it will stay there.

That's the point that drives Stern crazy, he says they ALL go into float stage prematurely and the battery isn't really fully charged.

Anyway, the point is that the charger will dump it's maximum amperage into the batteries from the starting point  - whether that's 50% SOC or 30% SOC or whatever until it hits approximately 80% SOC, then it will begin to taper.

Edit:  I see Stern posted his response while I was working on mine

 

[Mobilesport]

[font=Verdana, Arial, sans-serif]One would need to be able to achieve absorption voltage instantly, That might require 120 amps on a healthy pair of 6v gc-2[/font]

[font=Verdana, Arial, sans-serif]This last time I charged it went to absorption almost instantly , but I think that was due to me doing some charging yesterday and then not using much juice.[/font]
[font=Verdana, Arial, sans-serif]I didn't think I could put a 120 amp charger on two 6 volt gc2.[/font]
[font=Verdana, Arial, sans-serif]I thought the most I could use was like a 75 amp power corrected charger , maybe a 80 amper[/font]

 

[Optimistic Paranoid]

General rule of thumb is to have a charger about 25% of the battery bank's AH capacity.  In other words, a battery bank of 400 amp hours should ideally have a 100 amp charger.  Two 6 volt GC are usually around 220 amp hours, so 50 or 60 amps is about max for them.

 

[Mobilesport]

Almost instantly

 

[SternWake]

Not many 120 amp chargers available.

I am not sure what the instant absorption voltage amperage is on a pair of gc-2

70 or 80 amps is just kind of the upper edge of what one would want to provide a pair of gc-2 on a regular basis

When my northstar AGM was new and depleted to 50%, 106 amps was not enough to bring it instantly to 14.5v. Now that is down to about 85 or 90.

but it depends on how many cycles passed without the high amp recharge and how many recharges were not quite full. When it is punch drunk it achieves 14.5v much faster at a lower amperage.

 

[Mobilesport]

I think you are confusing amps and volts.  There are charts that show ROUGHLY what the resting voltage is at different SOC.

A smart charger operates in three stages. 

In the first, or bulk stage, it is a constant amperage charger.  That is, it will put whatever it's maximum amps is into the battery bank until the batter voltage rises to it's set point.  This might be 14.4 volts or it might be higher.  It might be locked in by the manufacturer, or you might be able to change it.

Anyway, once it hits it's set point, it becomes a constant voltage charger.  It sees to it that the battery voltage goes no higher than that, and it does that by cutting back on the amperage.  Eventually, the amperage falls to the point where the charge assumes the battery is fully charged, and it goes to it's third, or float stage.  The voltage will drop to something like 13.4 or 13.2 and it will stay there.

That's the point that drives Stern crazy, he says they ALL go into float stage prematurely and the battery isn't really fully charged.

Anyway, the point is that the charger will dump it's maximum amperage into the batteries from the starting point  - whether that's 50% SOC or 30% SOC or whatever until it hits approximately 80% SOC, then it will begin to taper.

Edit:  I see Stern posted his response while I was working on mine

So when amps start dropping I'll know I'm in the ballpark of 80% state of charge ? Is this correct? 
I try not to learn anything about automatic chargers because I'll be boondocking 100 % of the time

 

[SternWake]

So when amps start dropping I'll know I'm in the ballpark of 80% state of charge ? Is this correct? 
I try not to learn anything about automatic chargers because I'll be boondocking 100 % of the time

Not necessarily.  It depends on the amperage at which they were brought to 14.8v

Say one applied 100 amps to 220AH of batteries depleted to 50%.  Say it took 4 minutes  at 100 amps for the batteries to reach 14.8.  Amps would than have started tapering at  ~52% SOC

Say one applied 10 amps to 220AH batteries depleted to 50%  about 8 to 9 hours later and that 10 amps would start tapering and the batteries would be in the 90% range.

50 amps into 220AH of 50% depleted batteries, Well I could guess, but would be wrong.  The numbers above are also not written in stone, but a guestimate to prove a point

Given the same charging current and the same absorption voltage setpoint and the same capacity of battery:
    Abused batteries will reach absorption voltage earlier at a lower state of charge and amps will taper faster
     Healthy batteries will reach absorption voltage later at a higher state of charge and amps will taper slower

So I will not guess.  You tell me. At what amperage does the specific gravity reach 1.238?

You can see that keeping the batteries healthier for longer, will also reduce generator run times, saving you fuel

I am surprised your meanwell rsp-500-15 can do 50 amps.  Mine tops out at 40.

 

[frater secessus]

That's the point that drives Stern crazy, he says they ALL go into float stage prematurely and the battery isn't really fully charged.

Can't you tune the voltages and absorption period on the better charge controllers?

 

[SternWake]

Good solar controllers allow one to set either absorption voltage duration or a threshold of amps at which to trigger float voltage.

To get these features in a plug in charger, one is spending 500$ or more.

Sick of premature float voltage, and not willing to part with 500+ dollars, I use an adjustable voltage power supply, and I choose the voltage and when to lower it.

https://vanlivingforum.com/Thread-My-newest-electrical-toy

 

[Mobilesport]

[font=Verdana, Arial, sans-serif]Sternwake wrote[/font]
[font=Verdana, Arial, sans-serif] "I am surprised your meanwell rsp-500-15 can do 50 amps.  Mine tops out at 40."[/font]

[font=Verdana, Arial, sans-serif]Yeah , I noticed that when reading your charts but I just thought it was because my battery bank has more amp hours .[/font]
[font=Verdana, Arial, sans-serif]I figured my battery charger is the same as yours but my batteries are working it alot harder , it gets pretty warm at first  , my Meanwell fan comes on within 4 minutes and then Its pretty warm for the first 1/2 hour .[/font]
[font=Verdana, Arial, sans-serif]It took a hour for the Meanwell fan to turn off , it was at 26 amps when the fan shut off.[/font]

 

[SternWake]

Not the battery. If it was the battery limiting amperage then it would reach absorption voltage instantly and amps would begin to taper immediately.
My ~50% depleted 90AH AGM takes 40 amps for around a half hour before the tapering begins.

Varies with load still on DC system and actual battery state of charge.

 

[Mobilesport]

Not necessarily.  It depends on the amperage at which they were brought to 14.8v

Say one applied 100 amps to 220AH of batteries depleted to 50%.  Say it took 4 minutes  at 100 amps for the batteries to reach 14.8.  Amps would than have started tapering at  ~52% SOC

Say one applied 10 amps to 220AH batteries depleted to 50%  about 8 to 9 hours later and that 10 amps would start tapering and the batteries would be in the 90% range.

50 amps into 220AH of 50% depleted batteries, Well I could guess, but would be wrong.  The numbers above are also not written in stone, but a guestimate to prove a point

Given the same charging current and the same absorption voltage setpoint and the same capacity of battery:
    Abused batteries will reach absorption voltage earlier at a lower state of charge and amps will taper faster
     Healthy batteries will reach absorption voltage later at a higher state of charge and amps will taper slower

So I will not guess.  You tell me.  At what amperage does the specific gravity reach 1.238?

You can see that keeping the batteries healthier for longer, will also reduce generator run times, saving you fuel

I am surprised your meanwell rsp-500-15 can do 50 amps.  Mine tops out at 40.

Very good post , its making sense now

 

[BradKW]

Looks like MikeRuth has a battery filler of some sort:

 

[ccbreder]

These directions for resetting an amp counting battery monitor by MaineSail should help with what you want to know.

Know Full reset:
#1 Turn all DC loads OFF
#2 Fire up battery charger or engine & allow to run 4-5 minutes
#3 Voltage should be at ABSORPTION level or 14.4V+ = CHECK (GEL 14.1V)
#4 Net accepted charge current less than 1.5% -2% of Ah capacity = CHECK
#5 Okay to MANUALLY reset to 100% SOC

NOTE: Battery voltage should be at absorption voltage not float voltage, unless it has been floating in excess of 24 hours.
A known-full reset takes but a few seconds once the charge source has run for a few minutes. Easy and known accurate.
You can use 2% as your known-full current threshold but 1% or 1.5% is a fuller and healthier battery. For example most AGM batteries are not even considered full until they hit 0.3% - 0.5% of their capacity in net charge current at absorption voltage. This is 0.3A - 0.5A at absorption voltage on a 100Ah battery.

 

[Optimistic Paranoid]

Looks like MikeRuth has a battery filler of some sort:

Looks like a Trojan Hydrolink system that they make specifically for their own batteries.  Not sure if it could be adapted to other brand batteries or not.  Details here:

http://www.trojanbattery.com/products/hydrolink-watering-system/

 

[BradKW]

That looks nice...see any reference to how SG testing works with it?

 

[Optimistic Paranoid]

That looks nice...see any reference to how SG testing works with it?

Looks to me like you've still got to pull the caps off to draw electrolyte.  The hoses and such only contain pure water.

 

[ccbreder]

That device only adds water to the cells. You would have to remove the caps to pull a sample of liquid for SG test. The auto fill would need to be off for a while to avoid diluting the test. There are systems for auto watering available for almost any battery with caps. If your batteries are accessible and your charging system properly adjusted, I would not use these systems. I find it better to have a look at my stuff 4 or 5 weeks.