Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath

I’m about to wrap up the 1st 3 weeks of charging my Trojan L16RE’s using PV. Here’s my experience.

Some background: I have a Flexpower panel (includes most of the Outback products & monitors), I have 5-6 hours of very good sun/day this time of year, I typically only use about 1.8 Kwh/d, and I am rarely home between 8am and 6:30pm. During this time the only draw is the fridge and the outback inverter (in search mode frequently). The 100% SOC for my newer Trojan RE’s is 1.277 (or 1.280, depending on the Trojan website you visit;)).

Basically I have been experiencing gradual battery SG drop-off, with my CC inputting roughly the same number of amp hours IN (PV) as OUT (my usage). This appears to be a common experience, especially for you Northerners in the winter. Regardless, after reading NorthGuys post some seem happy with (say) 3-5 days of 50-80% SOC, then one day of forced charging (an EQ or an extra long absorb) to de-stratify and achieve ~100% SOC.

But, like Coot said…to paraphrase…if your PV can bring your bank up to 100% each day, then let it. I am convinced my PV can, but perhaps I need to make my Outback system perform longer absorbs.

To cut to the chase, my Outback Flexpower system and my hydrometer appear to be at odds. Although I started 3 weeks ago with a (generator FX charged) battery bank SG of ~1.270, I have seen my SG’s slip at sunset each day from 1.270 to about 1.250 over 3 weeks. At the same sunset time my Mate happily says that my batteries are 100% charged (BTW I did input my amp hour battery bank value into my FlexnetDC battery monitor).

In my CC logs my daily absorb time is typically about 20-35 minutes long (average of 30 minutes?) despite my setting the absorb time to 2 hours in the advanced settings. After reading NorthGuy’s thread, and seeing my shortish Absorb times I upped my absorb voltage from 58.8 to 61v. However, this is obviously not enough since my SG’s still slip. I guess once the battery monitor senses 100% battery state of charge it tells the CC to go to float.

Coot you said: “Nice thing about Outback controllers; you can set minimum and maximum Absorb time as well as End Amps.” However Outback says I can only set a maximum absorb time on my FM80 in the CC advanced settings, but not a minimum absorb time. There is literally no screen I’ve seen that allows you to input a minimum absorb time. The older MX chargers may have had something along these lines.

So, yesterday evening after a day of really good sunlight I came home and performed a 2.5 hour EQ on the generator. My SG’s went up to 1.265/1.270. But I would like the PV to do this ‘for free’ please:roll:.

My thought is that if my Flexpower system/battery monitor cannot accurately sense SOC, a longer Absorb time is a solution to slipping SG’s. Coot, you also said “You may have to increase your End Amps; it has to include the value of any loads drawing while charging.” I checked and I actually did NOT set an end amp value (I thought I did but the advanced CC settings say “00”). Maybe this is a solution (2% of my battery Bank would be 7.4 amps). However, my instinct also tells me that not being home in the day may also influence this end amps parameter.

I know there must be a simple solution. I will try to remember to write down more of my log #’s so that I can provide more concrete stats, but that’s the skinny for now:cool:.

Cariboocoot

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

If no End Amps is set the controller will try to maintain Absorb Voltage until the maximum time runs out. If the panels are not capable of doing this you fall out of Absorb before it is completed regardless of settings.

Pushing the Absorb Voltage higher or using the EQ cycle will force SG higher due to the higher Voltage. This doesn't seem to work as well as an Absorb time at the normal Voltage, at least not long-term.

Crank the Absorb time to the max and see how long the panels can actually maintain that Voltage level.

And no, no method of measuring battery SOC is 100% accurate, including SG readings. Any method of measuring anything is only accurate in reference to another measure. I'm sure every battery monitor has some +/- tolerance to its "100%" or any other number. Likewise not every hydrometer will read the same, nor would every 'same' battery read the same on the same hydrometer. Aggravating as all get-out, but there it is. This is why it is best to fully charge your batteries when new, check all cell readings and make sure they are equal (the "commission charge" you hear about) and then write those numbers down as a base reference.

You know what's worse? Batteries don't maintain capacity over time no matter how well they're treated. This is one of the drawbacks of monitors: you put in 'X' Amp hours to begin with but in a few years the real capacity becomes <'X' and there's nothing you can do about that.

Why Outback would have removed the min Absorb time setting I don't know. They must have felt it unnecessary owing to the inevitable run-up of the clock during Bulk. Not sure that was a good move on their part.

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Hi Coot.
It's hard to tell during the week when I am not at home during the day. However, on the weekends I go into float by mid morning. There ought to be enough sun/PV to keep maintain an absorb for longer than 30 minutes. I get 6:00am to 6:30pm sun now.

I did a commissioning charge as you describe, so I feel good about my benchmarks. If I could set a minimum absorb time I'd probably set it in increments until I could reliably get SG up to the 1.26 mark on a daily basis (and let float do the rest?). But still don't know how to do this.

You originally said I might try increase end-amps, but now you say that if "00" end amps are set then theoretically the maximum absorb time should rule the day. Wonder why it isn't. I may try increasing the absorb time this weekend (I think it maxes at 4hrs). I'll be there to monitor.

inetdog

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Cariboocoot wrote: »

And no, no method of measuring battery SOC is 100% accurate, including SG readings. Any method of measuring anything is only accurate in reference to another measure. I'm sure every battery monitor has some +/- tolerance to its "100%" or any other number.

Which invites the question of what you want to call SOC as the battery's capacity decreases with age.

In the case of sulphation, the SOC, interpreted as percentage of currently available capacity, will be 100% with an SG lower than the original SG of the battery when new because some of the S04 is tied up in sulphate on the plates.
If the loss in capacity is the result of plate shedding or other similar mechanism, then 100% SOC may still occur at the original SG, but that will be at a fraction of the original capacity.

Both how much of the current battery capacity you have and how many amp hours / watt hours that corresponds to are important numbers to know. SG will not, by itself, continue to give you either of those numbers. But is a lot better than knowing nothing or just measuring voltage.

I know! Use only new batteries. :-)

Cariboocoot

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Things that end the Absorb stage in order of operation:

1). Insufficient charging power to maintain the Voltage.
2). End Amps reached providing time has not run out.
3). Absorb time clock has run out.*
4). Absorb max time has been reached.

*This is the tricky one, as the clock "runs up" during Bulk. if it takes 2 hours from start of charge to the Absorb Voltage then Absorb clock is at 2 hours. If you bulk up with a gen and it only takes 1 hour then that's all the Absorb time you get regardless of other settings. This is why the minimum Absorb time setting was valuable. If End Amps is reached before the clock runs out, that shuts down Absorb.

Note this applies to Outback charge controllers not MidNite, Morningstar, Xantrex, et cetera. You've got to read those blasted manuals thoroughly - then try not to forget what you read. I read that somewhere, but I forgot where I read it.

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

One small, interesting observation after I performed my EQ yeaterday and got ~100% chemical SOC, is that the battery electrolyte seemed much 'thicker'.

At first I thought I had an obstruction in my 'turkey baster' hydrometer. However, I think it was just the thicker stuff being stirred up from the depths of my L16's.

For 2 weeks I had gotten used to more watery readings, last night it was more 'soupy.'

My gut tells me that these L16's need this stirring in order to charge in a uniform, healthy way. Who knows.

inetdog

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath wrote: »

One small, interesting observation after I performed my EQ yeaterday and got ~100% chemical SOC, is that the battery electrolyte seemed much 'thicker'.

At first I thought I had an obstruction in my 'turkey baster' hydrometer. However, I think it was just the thicker stuff being stirred up from the depths of my L16's.

For 2 weeks I had gotten used to more watery readings, last night it was more 'soupy.'

My gut tells me that these L16's need this stirring in order to charge in a uniform, healthy way. Who knows.

If the electrolyte really is soupier (more viscous, to use a technical term) but the measured SG is the same, then there is something besides H20 and H2SO4 in that mix. Hard to speculate on what it might be. :-)
It is very normal for the physical characteristics of the electrolyte to change as the SG rises. (BTW, you are using a temperature corrected hydrometer reading, aren't you?)

Cariboocoot

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath wrote: »

My gut tells me that these L16's need this stirring in order to charge in a uniform, healthy way. Who knows.

Da Shadow do!

Yup; getting the tall case batteries stirred up requires more effort. That's why Trojan suggest minimum 10% current and some fairly healthy Voltages.

Electrolyte stratification has been discussed many times on the forum. Can't say we've found any consensus on how, when, why ... or what to do about it.

inetdog

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Cariboocoot wrote: »

Can't say we've found any consensus on how, when, why ... or what to do about it.

Shake, rattle and boil.
Although complicated air pumping systems seem to work for some forklift battery applications, the only consensus I have seen here or elsewhere is that a good charge at above the gassing voltage is always helpful. Just add water as needed.

NorthGuy

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath,

I'm glad your batteries are in good shape and not as bad as mine!

Here's what I've learned when I did the research on my batteries:

Charging is actually 2 separate processes:

1. Chemical reaction. It reverses what was done during discharge. As a result of this reaction, water is replacid with acid and acid falls on the bottom of the battery in big blobs. To complete chemical reaction, you need to put back the exact number of AHs that you took out during discharge. If this reaction is not complete, lead sulphate is left on the plates where it can harden causing sulphation.

2. Mixing electrolyte. This is necessary to drag the acid from the bottom and make nice uniform solution. This is accomplished by splitting water into oxigen and hydrogen. The bubbles coming up mix the electrolyte in the process. For this, you need to supply extra AHs. If this process is not complete, acid will not intermix and stronger acid at the bottom will cause corrosion and other bad things. This is called stratification.

When, and only when both processes are complete, you can get full SG. Full SG tells you that (a) the chemical reaction is complete and all acid came out into the electrolyte and (b) electrolyte is fully intermixed. If you do not get full SG, one of the processes is not complete, but there's no way to find which one. Full SG is an assurance that the battery is fully charged.

When you count AHs to figure out SOC, you need to understand that you need to (a) put back all the AH that you took during discharge and (b) put enough extra AHs to cause bubbling and electrolyte stirring. The makers of your battery monitor, hopefully, knew that. So, there must be somewhere a settings that would let you set the ratio of AHs returned to AHs taken. For example, you put back 15% more than you took, or 20%, or whatever you specify. You need to find a way to increase that number to match your batteries, your usage pattern etc. When you get full SG at the completion of the charge, you know the number is set correctly.

Absorption voltage has little influence on the speed of chemical reaction - battery can only take charge so fast, and you cannot put in much more than it wants to take. However, absorption voltage has huge influence on bubbling. Higher voltages cause way more bubbling than low one. You can manipulate absorption voltage to put chemical reaction and bubbling in sync.

If your absorption voltage is too low, your bubbling will lag behind. You will see that your charging current stabilized and doesn't go any lower (which means chemical reaction is complete), but SG is still low.

If your absorption voltage is too high, your bubbling will go ahead of chemical reaction. In this case your SG will get close to full values while charging current is still dropping.

With good absorption voltage, both processes will be completed simultaneously - your current stabilizes and you get full SG. You can record the current and measure your SG during absorption and see what's going on, then adjust the voltage accordingly. But, of course, this depends on depth of discharge, regime etc. etc.

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

inetdog wrote: »

If the electrolyte really is soupier (more viscous, to use a technical term) but the measured SG is the same, then there is something besides H20 and H2SO4 in that mix.

I'm speaking about draws at different SG's - The electrolyte at 1.25 SG was pretty watery, but at 1.27 it was definately harder to draw it into the turkey baster 'bulb.'

I do have a temp compensated hydrometer. Obviously temps slightly rise during high voltage absorbs & EQ's, but during most of the day they are at at a convenient 80 degrees (F).

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

NorthGuy,
The main thing that perplexes me about your RE batteries is the length of time it takes you to get up to full SG. Anyway, I have read your post and am dissapointed that Trojan has not acknowledged this. Otherwise you are doing an admirable job making the best of it.

You said, "When you count AHs to figure out SOC, you need to understand that you need to (a) put back all the AH that you took during discharge and (b) put enough extra AHs to cause bubbling and electrolyte stirring."

I am trying to do this. Unlike you I have ample sunlight. However, I can't seem to do this conveniently with my Outback gear. Yesterday I used the FX charger & genny to perform an EQ, and I guess if I was at home in the early afternoon I could have also performed a PV equalization. However, why should I need to run an EQ every week to achieve that important stirring that we speak about......when a longer absorb could perform a daily 'bubbling' and 'stirring'?

Ha. Sounds like witchcraft to me..

NorthGuy

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath wrote: »

You said, "When you count AHs to figure out SOC, you need to understand that you need to (a) put back all the AH that you took during discharge and (b) put enough extra AHs to cause bubbling and electrolyte stirring."

I am trying to do this. Unlike you I have ample sunlight. However, I can't seem to do this with my Outback gear.

I don't know about "Outback Flexpower system", but you said you had "FlexnetDC battery monitor". Does this monitor counts AHs to figure out the SOC? If so, there must be a setting on how many AHs must be returned for every AH taken. For example, you should be able to specify that you need 115% of AH returned. Then, for example, you take 100AH, but monitor will not show full SOC until 115AH is returned back. Does it allow for such calibration?

Surfpath wrote: »

Basically I have been experiencing gradual battery SG drop-off, with my CC inputting roughly the same number of amp hours IN (PV) as OUT (my usage).

IMHO, that is not enough. There needs to be more returned than taken. Otherwise, you either don't get enough charge or you don't get enough bubbling.

inetdog

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath wrote: »

The electrolyte at 1.25 SG was pretty watery, but at 1.27 it was definately harder to draw it into the turkey baster 'bulb.'

Not suggesting it as the explanation, but for others out there: If you do not rinse the hydrometer with distilled water before putting it away, you can start building up deposits on the inside glass surfaces.

mtdoc

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

NorthGuy wrote: »

I don't know about "Outback Flexpower system", but you said you had "FlexnetDC battery monitor". Does this monitor counts AHs to figure out the SOC? If so, there must be a setting on how many AHs must be returned for every AH taken. For example, you should be able to specify that you need 115% of AH returned. Then, for example, you take 100AH, but monitor will not show full SOC until 115AH is returned back. Does it allow for such calibration?

Yep - you must specify the Battery Charge Factor when calibrating it.

See THIS tech note on FNDC calibration.

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

inetdog wrote: »

Not suggesting it as the explanation, but for others out there: If you do not rinse the hydrometer with distilled water before putting it away, you can start building up deposits on the inside glass surfaces.

That is actually a valid point Inetdog. I only started rinsing my hydrometer 2 weeks ago after a few months of using it. I have a new one coming on Monday and will compare the two.

Vic

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath,

indtdog is correct IMHO about the careful rinsing of the Hydro after use. Personally I'd rinse it at least twice after each measuring session with real Distilled Water, and at least the tip before each session if it has been sitting exposed to dust etc for a week or more. Would not trust Deionized water, or purchased ROed water with my expensive batteries.

Any of the sticky residue will allow smallish air bubbles to stick to the float, causing additional bouyancy which can cause erronious high SG readings. The bubbles adhearing to the float are quite visible. In my experience, this sticky residue is nearly impossible to remove with casual cleaning efforts. There may be a solvent or cleaner that will clean it, and be easily removed by some additional cleaning step, but I do not know what any such cleaner might be.

Having several Hydrometers is very nice -- allows voting and is a backup WHEN something happens to the main Hydro.

Good Luck with the new bank

NorthGuy

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Vic wrote: »

Having several Hydrometers is very nice -- allows voting and is a backup WHEN something happens to the main Hydro.

I had one hydrometer and then bought two more. The new ones matched each other, but the old one was on a low side, so I don't use it any more. But now I'm sure that my measurements are correct. The more hydrometers the better!

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

See the attached data regarding my last few weeks of charging.

A few relevant points:

• Absorb time is set on my CC as 2 hrs. I have been getting about 30 minutes of absorb in reality.
• Coot, I upped the Absorb time to 4 hrs on Friday nighte as you suggested. I don't think it made a difference. I think I got 20-something minutes of absorb on Saturday.
• On Sunday (today) I did something different. I was home the whole day so I performed a 1.5 hr "low voltage" EQ. Basically I wanted to see if I could force a longer "absorb-like" charge. This was about an hour after actual absorb ended. I set EQ voltage around my regular Absorb voltage setting. It seemed to work, it added more amps into my bank and brought SG's more in line.

Basically I am still hoping to find a way to increase my typical daily Absorb time (to, say, an hour - just to see what effect that would have). I go into system float each day by about 11am, so I have lots of available sun. Every weekend I can do a lowish voltage EQ like I did today to bump up my SG's to roughly 90%-100% SOC, however I'd rather bring my system up to 90-100% chemical state of charge (ie. I am asking for 1.260-1.265) on a daily basis, automatically.
Attachment not found.
**Note regarding the Battery Bank SG column: The EQ ones were logged, however the others were taken but not logged. They are an estimation of SG at the conclusion of charging each day based on memory.
BTW: my commissioning EQ resulted in all cells around 1.270/1.275.

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Yup, I will use the new hydrometer tomorrow and see if the voting is different.

Overall, I am not unhappy with how my bank is performing. It seems to respond to EQ well and bounce back to commissioning SG's in a reasonable amount of time. I'd just like to tweak things slightly and see if I can get slightly higher SOC's at the end of each day so I don't have to EQ every week. Like many others on this forum seem to be experiencing now, my SG is dropping with time (but that seems to be because my CC wants to only input each day, roughly, what the inverter takes out - it's not because I don't have enough sunlight due to Winter).
-SP

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

By the way, I recently read in my CC manual that if you have an accurate voltmeter you can "recalibrate" your CC. Here's the text.

A quality calibrated voltmeter will provide even more
accurate Charge Controller battery readings if an undesirable
voltage drop occurs. When measuring battery voltage,
ensure a good connection is made to the four wire
lugs. Check the battery temperature compensation voltages
if the voltages are much different than you expect
from the charger setup Absorb and Float voltage settings.
Use the <-> and <+> soft keys to match the readings
from the voltmeter (use of appropriate wire gauge
will minimize voltage drop).

In short, perhaps I should also double check that my CC is recording the right voltage for my bank?

After reading the CC manual again it seems like the trigger for the CC to go from absorb to float is typically a simple voltage-related one (unless end amps is set). If one's system is not measuring the voltage 100% accurately then perhaps the charging process could be slightly affected?

What defines as a quality calibrated voltmeter? Does my ANCOR marine multimeter pass?:D:
Measures to 1000V DC, 700V AC. measures AC/DC current to 10 Amps.
Input impedance 10 MEG Ohms.
Easy-to-read 32. digital LCD display, includes heavy-duty test leads and Instruction manual.
Protective rubber shell with bench stand and built-in lead storage.
Fuse protected up to 10 Amps, 9V battery included.
Auto power off, low battery indicator, audible continuity beep.
Probably not...

inetdog

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath wrote: »

What defines as a quality calibrated voltmeter? Does my ANCOR marine multimeter pass?:D:
Measures to 1000V DC, 700V AC. measures AC/DC current to 10 Amps.
Input impedance 10 MEG Ohms.
Easy-to-read 32. digital LCD display, includes heavy-duty test leads and Instruction manual.
...

Nope. Not without some additional work.

First of all, a quality meter will include some accuracy specifications in the manual and sales literature.
Something like a "+/- 5% on xx range" for all of the ranges. And it will maintain that accuracy over time.
Second, if the +/- figure is small enough to make the voltage distinctions you need to make (e.g. between 14 volts and 14.2 volts), you can go with it as is, but check every now and then to make sure it has not gone inaccurate for some reason.
But even if the accuracy figure is not as good as you need for setting charging voltage, you can calibrate it by using it to measure a known exact voltage which is in the same range as what you are trying to measure. That will allow you to calculate the real voltage from the display voltage as long as your meter is consistently off from the real voltage by the same percentage.

A cheap calibration source is a brand new, never used, carbon-zinc battery. Over a wide range of battery sub-types (normal, heavy duty, long life, etc.) the voltage will be 1.54 volts. Just make sure that you do not use an alkaline, mercury, lithium, silver oxide, or some other cell type by mistake.
To get a calibration voltage close to the 12 volts that you need, you can take a carbon-zinc 9 volt battery. The voltage (again, of a new, never used, battery) will be 6 x 1.54 = 9.24 volts.
If nothing else, this will let you periodically check that your meter has not gone bad from age or rough handling.

vtmaps

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath wrote: »

After reading the CC manual again it seems like the trigger for the CC to go from absorb to float is typically a simple voltage-related one (unless end amps is set). If one's system is not measuring the voltage 100% accurately then perhaps the charging process could be slightly affected?

You may be over thinking this. The voltage calibration is not that important. The premise for your concern is wrong:
the trigger for the CC to go from absorb to float is NOT typically a simple voltage-related one.

If end amps is not set, the trigger to float is a timer, not a voltage measurement. The timer runs when the voltage is at the absorb voltage. If the voltage drops below the absorb voltage the timer stops, or may even run backwards if the voltage drops low enough.

Now there's nothing wrong with calibrating your CC voltage, but it is not usually critical. If you feel that your absorb voltage is not high enough to charge your batteries, raise it a bit. You only have two choices: raise voltage or increase time (or both).

By the way, 'Stephendv' has posted several times about how some European chargers do not do a full charge every day. It may be easier on the batteries to not fully charge them every day. As long as you get a full charge a couple of times per week (to avoid sulfation and stratification) the batteries may last longer if you avoid 'overcharging' them with daily hours of high voltage.

--vtMaps

Blackcherry04

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

vtmaps wrote: »

You may be over thinking this. The voltage calibration is not that important. The premise for your concern is wrong:
the trigger for the CC to go from absorb to float is NOT typically a simple voltage-related one.

If end amps is not set, the trigger to float is a timer, not a voltage measurement. The timer runs when the voltage is at the absorb voltage. If the voltage drops below the absorb voltage the timer stops, or may even run backwards if the voltage drops low enough.

Now there's nothing wrong with calibrating your CC voltage, but it is not usually critical. If you feel that your absorb voltage is not high enough to charge your batteries, raise it a bit. You only have two choices: raise voltage or increase time (or both).

By the way, 'Stephendv' has posted several times about how some European chargers do not do a full charge every day. It may be easier on the batteries to not fully charge them every day. As long as you get a full charge a couple of times per week (to avoid sulfation and stratification) the batteries may last longer if you avoid 'overcharging' them with daily hours of high voltage.

--vtMaps

You win the award VT, best advice of the week. You got to love a Post that says " My Batteries are in Float by 11:00 everyday " but never a detail of ending amps or % being accepted prior to going into Float.

Even if you only have Voltage and Time on your charging source, you can use a clamp on amp meter to find the amps going into the batteries and you should be able to adjust the source to give you the ending amps you need prior to going to Float.

jeffkruse

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath I feel for you. This seems to be the most important problem that the people selling solar don’t tell you. I went through the same thing. Batteries in float by 11AM and the SG kept going down and down. I think the most important thing is to set the absorb time to Max. Do you get any clouds during the day? My system was just like yours and I lived in San German, PR. We basically had on and off clouds in the afternoon. With your usage and amount of panels I don’t think there is any harm with setting the absorb time for 4 hours. I wouldn’t do that with an absorb V over 60volts though. I would hope you could have your absorb V set to 58.8 or so.

You need to figure out how to make the absorb time go for the full 4 hours! Good luck!

NorthGuy

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Surfpath wrote: »

See the attached data regarding my last few weeks of charging.

According to Trojan manuals, what you're seeing is expected. The SG dwindles down slowly and eventually gets too low. Then you equalize. It appears you need to equalize twice a month, but equalizations are relatively short (3-4 hr probably would do it) and manageable. Equalization restores SG and so on ...

However, you only discharge 10-15% of your batteries (hence equalizations are short). I suspect that at bigger discharges, it'll be harder to maintain this regime. Are you planning on bigger discharges in the future?

Also, some would say that you would need to have few relatively deeper discharges at the beginning of the battery life to break the batteries in. I don't know if that has some merit, but it may be important if your discharges are so shallow.

jeffkruse

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Everything I have read indicates equalizations are for imbalanced cells, not for generally low SG. You shouldn’t do an EQ unless your batteries are “fully” charged.

I am starting to wonder if a full charge every X (3-10) number of days is better for the life span of the batteries than a full charge every day or two. Maybe we are obsessing too much on getting the SG up every day or two. If this is true then maybe charge controllers need to be flexible enough to allow the user to program it this way.

Maybe you should be able to tell the charge controller to charge to 85% every day and do a “full” charge (higher V or longer absorb/mini EQ) every week. The batteries could operate in a much more efficient area and it might be less stressful on the batteries. I wish we knew.

vtmaps

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

jeffkruse wrote: »

Everything I have read indicates equalizations are for imbalanced cells, not for generally low SG. You shouldn’t do an EQ unless your batteries are “fully” charged.

You are sort of right... what you are referring to is 'corrective equalization' for imbalanced cells. Some batteries (especially calcium lead acid) need high voltages to achieve their maximum SG. These voltages are so high that we call them equalization voltages. Some folks set their daily absorb voltage too low to get a full charge and then once or twice a week run an 'equalization' to achieve a full charge with SG to specification.

Maybe you should be able to tell the charge controller to charge to 85% every day and do a “full” charge (higher V or longer absorb/mini EQ) every week.

Some chargers do allow for an automatic weekly equalization. This can accomplish what you suggest.

--vtMaps

NorthGuy

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

jeffkruse wrote: »

Maybe you should be able to tell the charge controller to charge to 85% every day and do a “full” charge (higher V or longer absorb/mini EQ) every week. The batteries could operate in a much more efficient area and it might be less stressful on the batteries. I wish we knew.

That is also a question of available power. If you get good solar, it's essentially free for you to get more charge into batteries because absorption/equalization takes relatively little current. In this case you do not need high efficiency because you throw away the available power anyway. If you have to run a generator to get extra charge every day, that's a different story.

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

jeffkruse wrote: »

You need to figure out how to make the absorb time go for the full 4 hours! Good luck!

Hi Jeff.
From several responses I guess this drop off in SG is a normal thing. I am not too worried about it. My SG's drop gradually and I know that on weekends I can perform an EQ, like I did last week, if need be.

When I extrapolate the rough SG numbers on my chart it appears that I'd have to perform this EQ every 10-14 days (roughly: when end of charge SG's are about 1.240/1.235....ie. when I am cycling from 80% to 50%?). This parallels what NorthGuy said here, and what others have called the "European" method.

That said, I still have not dropped my original thought. Ie if I can slightly increase the number of positive AMPs coming into my bank each day, this SG drop would be just very slight and I would only have to perform EQ's once a month, as opposed to every 10-14 days. EQ's seem to be harder on my batteries.

Also, I have seen the charts where battery life is so much higher when DOD is 20-25% as opposed to 35-50%. Per Trojan Battery Trojan Tips #4: "Battery life is related to depth of discharge. The deeper the discharge the less cycles the battery can achieve. To maximize battery life you should limit depth of discharge."

I presume DOD here means the DOD (SG) of your actual battery, not the percentage of depth that you draw down each day.

Is this draw down to 20% or 25% just a mythical thing?

Surfpath

Re: Charging my Batts: Round one - "Outback vs the Hydrometer"

Hi Blackcherry,
You said: "You got to love a Post that says " My Batteries are in Float by 11:00 everyday " but never a detail of ending amps or % being accepted prior to going into Float. Even if you only have Voltage and Time on your charging source, you can use a clamp on amp meter to find the amps going into the batteries and you should be able to adjust the source to give you the ending amps you need prior to going to Float."

I'd like to learn a little more about the (Outback) end amps feature. Perhaps this will help me to tinker with absorb times. In an earlier post I did detail my daily AMP usage on a chart. I am also aware of the 2% recommendation (7.4 AMPS for my bank) if one is to enter an end-amp value. However are you suggesting another more accurate way to set this feature?