Configuring generator to fully charge batteries

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DavzRVPort
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Re: Configuring generator to fully charge batteries

Post by DavzRVPort » Tue Jan 22, 2019 4:12 pm

If you are using 29.4 that equates to 2.45/cell. (dividing by number of cells... assuming 2v cells)
If you don't already have a vented battery box, you should make one.
Be sure to use an explosion proof fan (like a Zephyr 12V Power Vent) and wire to one of the FM80's to come on at a specific voltage using an aux port.
http://www.cleanenergybrands.com/shoppi ... ystem.html
Mine comes on at 56.6V on a 48 volt system, maybe around 28.2 will exhaust any gases created by yours.
Last edited by DavzRVPort on Thu Jan 24, 2019 3:38 pm, edited 2 times in total.

JRHill
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Re: Configuring generator to fully charge batteries

Post by JRHill » Thu Jan 24, 2019 1:31 pm

Just an FYI and for those pondering Absorb charges: I've been on the genset, autostart, 2 minute @ 48.8 all winter, w/a full charge cycle for 2hrs, for whatever winter it was... but the sun still set behind the trees and almost no snow on panels. A little over a month ago I bumped the Absorb to 2.5hrs, each cycle on the genset. Guess what? I still lost ground each day and the FNDC is so far out of calibration that I just use it for day-to-day comparison. SGs compared to the FNDC were worthless. I'll reset this summer when the sun comes back out - as I do each year.

These batteries are starting their 3rd year. They were, forgive me, PERFECT, heading into the winter. I hope to be good to them. But 2, 2.5, 3 or more absorb hours... does that bother you? In the summer they bulk at 61.1 get 4.5hrs absorb @ 58.8.

I charge the $%&^% out of the flooded batteries. It costs literally pennies for water and no, within reason you won't hurt them as long as you look at them each few weeks. They do go into a "Partial Shutdown" each winter but unlike some things, you can resolve the issue without a presidential resolve.

Push your Absorb cycle. You might be surprised at the performance.

rpbancroft
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Re: Configuring generator to fully charge batteries

Post by rpbancroft » Wed Jan 30, 2019 2:38 pm

Thanks for the suggestions, DavzRVPort. We do wish to integrate some venting (they do have a few small holes in them to at least allow a bit of circulation), but I've been told that these batteries do not create appreciable amounts of gas except in overcharge scenarios. We're still trying to figure out the root issue, why these AGM batteries, which I've been assured by their vendor do not need any venting (supposedly they're specifically designed to be installed in poorly ventilated spaces), would be producing (presumably) so much hydrogen gas. It's hard to know if they're producing a "lot," as a CO detector isn't really equipped to identify exactly how much they're producing. It's reporting a number, but how accurate is that? Since it's not calibrated for it, I have no idea. The only hydrogen gas detectors I've seen run $300 or so, and that seems like too much invest.

I've also read that hydrogen is not combustible until 40,000 ppm, but the OSHA recommendation for the maximum safe aerial concentration is 400 ppm. Again, I have no idea if the value reported on the CO detector is true to this #, so it feels like we're playing a dangerous guessing game, especially since the propane heater we use for heat is only a few feet away from the battery boxes (and only a bit move-able, given the tiny nature of the home).

It seems that, once our batteries reach the absorb phase (this doesn't seem to happen on cloudy days), they seem to start emitting tons of (I assume, since it's the only gas research has revealed could come out of an AGM battery) hydrogen gas, enough to push the meter to pretty high values. I've seen passive readings upwards of 15 feet away from the batteries of 35 - 150. The meter tops out at 999. If I remove the top on the battery box and put the CO detector right next to it, after about 45 seconds, it spikes to a 999 reading, and beeps. Keeping the boxes open and ventilating them seems to help, and, once the sun goes down, we can get the levels back down to zero after about 30 minutes. We are seeing readings in the low to mid 100s several hours into the absorb phase (just discovered that today).

These batteries are installed inside, in conditioned space, but they're in contact with the floor in a tiny house on wheels (as yet unskirted), which can be as cold as 45 - 50 degrees some mornings / days. I'd guess that, during winter, they're sitting around 50 - 65 degrees. The ratings I see for voltages for these batteries seem to be at 77 degrees. Does this mean I should drop the voltage?

What are the impacts that modifying the batteries' voltages can have? Should they be modified seasonally (based on battery average temp), or is there some other setting I should consider changing? Has anyone else encountered this issue?

For reference, we did not encounter this issue (though, to be honest, we didn't have a CO meter that could report the detected amounts until after this problem showed up) until we revamped the battery voltages, absorb, and float values. Any thoughts on changes we ought to consider that would / could minimize damage?

Thank you!

~Ryan

blackswan555
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Re: Configuring generator to fully charge batteries

Post by blackswan555 » Wed Jan 30, 2019 2:45 pm

We're still trying to figure out the root issue, why these AGM batteries, which I've been assured by their vendor do not need any venting (supposedly they're specifically designed to be installed in poorly ventilated spaces), would be producing (presumably) so much hydrogen gas.
If you have "off gassed" you AGMs,,, You have a very serious problem, Overvoltage was most likely the cause, possibly caused by lack of good temp sensing ?

But Basically, They are dead and I would suggest you do not use them anymore, They may have become dangerous,

Tim
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.

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Re: Configuring generator to fully charge batteries

Post by raysun » Wed Jan 30, 2019 2:51 pm

seems that, once our batteries reach the absorb phase (this doesn't seem to happen on cloudy days), they seem to start emitting tons of (I assume, since it's the only gas research has revealed could come out of an AGM battery) hydrogen gas, enough to push the meter to pretty high values. I've seen passive readings upwards of 15 feet away from the batteries of 35 - 150.
AGM and all VRLA (valve regulated lead acid) batteries are designed to recombine the hydrogen and oxygen dissociated during charging. If they are venting gas, it represents loss of electrolyte and subsequent battery capacity.

I've never seen a specification of allowable venting per charge cycle, but would assume it to be near zero.

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Re: Configuring generator to fully charge batteries

Post by rpbancroft » Wed Jan 30, 2019 2:51 pm

blackswan555 wrote:If you have "off gassed" you AGMs,,, You have a very serious problem, Overvoltage was most likely the cause, possibly caused by lack of good temp sensing ?

But Basically, They are dead and I would suggest you do not use them anymore, They may have become dangerous,

Tim
Oh... I hadn't considered that as a possibility. They seem to work normally except in this scenario, though. They never run hot, don't have any physical deformations, and they seem to still have their rated capacity of power (at least they run the house well enough). Is it still possible that they're busted and dangerous? Do batteries come with warranties?

Also, how does temperature sensing work in conjunction with the whole system? That's the first I've heard of that being part of the charging / voltage-regulation process.

rpbancroft
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Re: Configuring generator to fully charge batteries

Post by rpbancroft » Wed Jan 30, 2019 2:53 pm

raysun wrote:I've never seen a specification of allowable venting per charge cycle, but would assume it to be near zero.
That's what I'd assume, too, given what I've read and been told about them. That's why I'm so puzzled. We haven't set any voltage values very high or anything, just to what was recommended here. It's possible that the amount being vented is actually pretty small, but that a CO detector can't figure out what's going on. I just don't know, and I doubt any CO-detector manufacturer would know all that well (we've talked to Kidde, but they obviously know more about what their device is designed to do, not specific conditions that trigger false positives).

blackswan555
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Re: Configuring generator to fully charge batteries

Post by blackswan555 » Wed Jan 30, 2019 3:19 pm

The "VRLA" bit is the important bit, It is an emergency blow off valve, Which in your case seems to have blown,,,,, There is NO permitted venting otherwise,

No Warranty on venting,
CO2 detector is useless as you are looking for hydrogen,
lso, how does temperature sensing work in conjunction with the whole system? That's the first I've heard of that being part of the charging / voltage-regulation process.
When a battery is cold, It needs a higher voltage to charge, When warm, a lower voltage ( usual spec at 25c) If it is warm and you do not turn voltage down, The battery gets hotter,,, needing less voltage, You do not turn it down,,,It gets hotter,,,,,,,,,That ends with off gassing,,,,,,
You should have a remote battery temp sensor connected to ALL charge sources, Either individually or to whatever is in port 1 ( pref inverter) if it is a full OB interlinked OB system,

Tim
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.

rpbancroft
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Re: Configuring generator to fully charge batteries

Post by rpbancroft » Wed Jan 30, 2019 4:08 pm

blackswan555 wrote:The "VRLA" bit is the important bit, It is an emergency blow off valve, Which in your case seems to have blown,,,,, There is NO permitted venting otherwise,

No Warranty on venting,
CO2 detector is useless as you are looking for hydrogen,
lso, how does temperature sensing work in conjunction with the whole system? That's the first I've heard of that being part of the charging / voltage-regulation process.
When a battery is cold, It needs a higher voltage to charge, When warm, a lower voltage ( usual spec at 25c) If it is warm and you do not turn voltage down, The battery gets hotter,,, needing less voltage, You do not turn it down,,,It gets hotter,,,,,,,,,That ends with off gassing,,,,,,
You should have a remote battery temp sensor connected to ALL charge sources, Either individually or to whatever is in port 1 ( pref inverter) if it is a full OB interlinked OB system,

Tim
Great, thanks! That's kind of fortunate, actually, as our voltages were lower (28.8v I believe) during the summer when it was hotter, and have only in the winter been turned up. This whole episode has only happened during cold weather, when the voltage was increased. Given that, is it possible a voltage issue is happening, or could it be something else? Perhaps something actually physically wrong with these batteries? I imagine, like anything else, it's possible they're faulty, which only showed up under certain conditions.

raysun
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Re: Configuring generator to fully charge batteries

Post by raysun » Wed Jan 30, 2019 10:48 pm

The great thing about AGM batteries is you don't do have to do much to maintain them.

The bad thing about AGM batteries is you can't do much to maintain them.

Unlike flooded batteries, water cannot be replaced under normal circumstances. Also, the state of charge is hard to determine because specific gravity cannot be measured as in flooded batteries.

The only practical method to maintain AGM batteries is to very carefully charge them. That includes controlled three-stage charging with full-time temperature compensation. Even with that, AGMs have a lower cycle life, and the far higher per-cycle cost compared to flooded lead-acid batteries.

AGM batteries are very easy to kill with overcharging. Also, they are chronically degraded by persistent under charging. Further, it's really difficult to know when they are correctly charged.

The old maxim: "You will destroy your first set of batteries" is nearly universally applicable in PV storage applications. If this is your first set, consider "mission accomplished".

Please do take your batteries offline and contact the manufacturer about safe methods to test their state of health.

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Re: Configuring generator to fully charge batteries

Post by rpbancroft » Thu Jan 31, 2019 1:13 pm

Oh how delightful. I guess this can happen when the company who does something for you is profoundly inept (there is so much backing this statement that I won't bore you with the details). And I guess I should include myself in that camp for not being more skeptical and aggressively evaluating their work (not that I had the knowledge to do so at the time, but I could've pursued it had I considered the implications of misconfiguring voltages). I can scarcely believe I've made it to 35 without becoming more jaded. Yay.

Funny how no where in the AGM literature does it mention how "sensitive" they are (unless it's buried somewhere, or "coded" somehow, I haven't managed to unearth/decipher). They even mention that they can operate (both charge and discharge) within quite a wide range of temperatures, never once mentioning the need for variable voltages. I didn't even get to choose the batteries, and didn't even know what they were until several days past installation (had to retroactively request the documentation). I guess we may come to a point where I need to call some form of false advertising or malpractice on the part of the company that provided the system. I'll see what I can marshal in the meantime. On that note...
SandyP wrote:It sure is a strange battery charging graph, and something the the Outback FM charge controllers cannot exactly follow i.e :
Stage 1 : indicates constant current during Bulk charging - cannot see this happening (maybe using the inverter's charger)
Stage 2 : a two hour charge period at the end of the bulk phase at a slightly lower charge rate
Stage 3 : Absorb charge phase (no specific time period shown but seems to be 2 hours)
Stage 4 : A time limited float (or just a time limited stage but not float based on what they say the float voltage should be?) - maybe via the FX inverter but not via the FM?

So not batteries typically used for solar applications.
This is an interesting observation. The company that provided the hardware (not the same company that installed it) for this system specializes in solar. Can anyone else corroborate whether or not SandyP's analysis is correct, specifically that these are poorly designed for solar applications?

-----------------

I've been in touch with Centennial's help for the past several days, but the "front desk" folks don't have a whole lot of deep-level knowledge, so they haven't been able to provide any clear testing methods. They're trying, or so they assure me, but nothing tangible has come of it yet.

I managed to find a local off-grid, solar-installation expert who can come out tomorrow to take a look at things. Perhaps he'll be able to put us on the right path. I'll let you all know how things develop.

~Ryan

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Re: Configuring generator to fully charge batteries

Post by JRHill » Thu Jan 31, 2019 4:00 pm

raysun wrote:The old maxim: "You will destroy your first set of batteries" is nearly universally applicable in PV storage applications. If this is your first set, consider "mission accomplished".
This is an absolute, for sure. There are so many variables in PV systems....

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Re: Configuring generator to fully charge batteries

Post by rpbancroft » Mon Feb 04, 2019 2:46 pm

At the recommendation of the off-grid system expert (who, unfortunately, uses simpler charge controllers, so he's not an expert on batteries), I backed off the voltages on my batteries to see if the detected off-gassing would stop. I scaled all of them back .4v (their original setting, as shown earlier in this thread, was .6v back). He did say that his experience with AGM batteries has shown that they're quite resilient, so I'm hoping I got a lucky roll of the dice and mine happen to fall into that category. So far, they haven't failed in powering their loads yet.

It mostly did (no detected off-gassing during the absorb phase); even during the absorb phase, where the voltage was hovering between 28.9v and 29.0v, no off-gassing was happening. However, it did occur again this time after the absorb phase once the bank (as reported by the FNDC at least) was at 100%. The generator kept pushing current into the batteries (about .7 kW) despite them being finished charging, which I found odd, even though the reported voltage of the batteries (according to the Mate3s) was in the 27.6v ballpark. I'm hoping it's possible to force gen power to stop pushing current once they're finished, not sure why it didn't.

Just as a precaution, I backed voltages off that extra .2v for today (which was pretty sunny; I'll see what happened when I go home tonight). I feel like, at this point, I need to get to a stable point where off-gassing no longer occurs at any point in the charge cycles. Once I'm there, I feel like I can strive to optimize.

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Re: Configuring generator to fully charge batteries

Post by NatalieRoberts » Fri May 22, 2020 4:57 am

I think before you bring in your RV batteries for recharging, you should clean the terminals thoroughly first and make sure that they are in good condition. When you are at the charging station, make sure that the charging timeframe is followed. You should avoid rushing to charge the batteries. Using undercharged batteries will only cause considerable damage to them.

It will take roughly 72 hours to charge the batteries of an RV completely. Many rookie RVers leave their batteries to charge for a day, only to find out later that they do not have enough stored energy for their camping needs \:D/

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Re: Configuring generator to fully charge batteries

Post by raysun » Fri May 22, 2020 10:35 am

NatalieRoberts wrote:
Fri May 22, 2020 4:57 am
I think before you bring in your RV batteries for recharging, you should clean the terminals thoroughly first and make sure that they are in good condition. When you are at the charging station, make sure that the charging timeframe is followed. You should avoid rushing to charge the batteries. Using undercharged batteries will only cause considerable damage to them.

It will take roughly 72 hours to charge the batteries of an RV completely. Many rookie RVers leave their batteries to charge for a day, only to find out later that they do not have enough stored energy for their camping needs \:D/
Undercharged batteries have a very short service life, to be sure.

72 hours sounds like an exceptionally long time, but may be factoring in a low rate of charge during the Bulk phase. Ideally, a Flooded Lead Acid battery is charged at about 10-13% of its C20 Amp Hour capacity during the initial "constant current" phase. A lower rate of charge risks not "stirring up" the electrolyte enough to correct stratification and eventual capacity loss to sulfation.

Hopefully the charging stations for RV batteries are "smart" enough to execute an Absorb and Float stage, but it sounds like maybe it's only a low rate constant current charge.

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Re: Configuring generator to fully charge batteries

Post by NatalieRoberts » Mon May 25, 2020 6:52 am

Oh, is that right? Because I read information in here: https://www.listatrailer.com/how-long-d ... ally-last/ I thought that it exactly

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Re: Configuring generator to fully charge batteries

Post by Mike Curran » Mon May 25, 2020 7:14 am

This thread is a bit more specific https://www.rv.net/forum/index.cfm/fuse ... 175397.cfm

If you're using a low current charger like a "battery tender" that may explain the 72 hour duration datum.
20200525_101257.jpg
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

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