Avoiding sulfation and loss of capacity: How frequently must I charge to 100%?

[chrisski]

So you prefer a 16 volt overcharge with the caps off and little drops of electrolyte jumping out and the place stinking like yellowstone vs drawing them down to 11.5v fairly quickly and then charging them back up at 14.4 with some decent amps?

How is the overvoltage way of stirring the electrolyte better?

Is discharging to 11.5 volts a technique you use frequently and your batteries have lasted for years? If so, then you are correct; otherwise I can only go off what is on spec sheets and user manuals. Too expensive for me to experiment. If it works for you, I’m still reluctant to experiment off one good result.

I think the most important thing is to follow whatever spec sheet the battery has.

I prefer to not draw batteries below 50%. At 11.5 volts on a FLA battery, that is just above 10% SOC, 90% DOD. Going below 50% is supposed to significantly reduce the life of a battery. My chart puts 50% DOD at 2000 cycles, and stops at 20% DOD is 1000 cycles. 10% is not listed. Not somethign I want to do when spending over $1k for four GC2H golf cart sized solar batteries, or even cheaper GC2 golf cart batteries from COSTCO.

I’m assuming an FLA battery. The Trojan user manual I have says a battery should be equalized monthly. When I did equalize you could here it bubbling, which is certainly circulating the electrolytes.

I did not equalize monthly. I did add water monthly and check specific gravity, and this is a good way to circulate the electrolyte. Take it into and eject from the hydrometer three times before measuring. If the electrolyte is out of tolerance, than equalize. Mine was almost perfectly matched for the 18 months I had the batteries and only equalized once.

 

[Goboatingnow]

Fully charged batteries sitting idle tend to die fairly quick deaths as well.

Less if they are equalized regularly but overvoltage equalization and drawing them down and charging them up quickly give the same benefits but without the side effect that over voltaging the battery does.

Your car does not equalize its battery using overvoltage.

No AGM and Gels are designed to hold 100% Soc for long periods approaching 2 years in some cases. Whereas lithiums are not. The downside is they hate partial SOC

 

[Vigilant24]

My understanding is while yes you want to charge an AGM bank at 0.2C, it doesn't need to be done every single day. Once or twice a week is fine, as long as you're respecting the 50% DoD. Every day would be even better, but it's not critical.

Well, that certainly opens up some possibilities. I can think of several ways to get to 0.2C or better on an infrequent basis, especially for one subset of batteries at a time.

Now I learned recently, you can throw as many charge sources at a battery bank as you have available.

I saw that Will P referenced this in one of his videos, and I need to learn more to understand it. It seems to me that each charge controller needs to periodically monitor the battery voltage to determine the state of charge, and if charge controller B is feeding the battery a higher voltage then charge controller A would see that as the actual battery voltage, which would be inaccurate. Probably too simplistic (maybe the pulsed high voltage of the "active" charge controller is cancelled out and the "sensing" charge controller just chooses the lowest voltage senses over the monitoring period as being the voltage of the battery? Seems pretty sophisticated for this application).

Multiple charge controllers is appealing to me for this application, since it allows for redundancy, and because I have shading issues. Charge controllers seem to be largely priced linearly per amp, so getting a few smaller ones doesn't come at a big premium over a single bigger one.

I looked into a DC-DC charger off the alternator, we even bought and then returned one, because for a 12V system carrying 40A, you need 4AWG cable - and the good stuff ain't cheap. $115 for 40 feet of black and 40 feet of red. You can get CCA (copper clad aluminum) for much cheaper, but it's just not as good as pure copper.

An exercise I've wanted to do, will get to soon: If I dump all my pride and don't care how things >look<, can I save money by using bundled 12 gauge stranded wire or even solid 12 AWG wire (from Non-Metallic cable, aka "Romex") in lieu of fat 4 AWG awg? Solid wire is not very flexible and will eventually break if repeatedly flexed in the same place, so it is far from ideal for most uses. But, I'm thinking of a relatively short-term application, and it will stay put, not re-folding it daily.

Thanks. I'll have more dumb ideas later....

 

[Checkthisout]

Is discharging to 11.5 volts a technique you use frequently and your batteries have lasted for years? If so, then you are correct; otherwise I can only go off what is on spec sheets and user manuals. Too expensive for me to experiment. If it works for you, I’m still reluctant to experiment off one good result.

I think the most important thing is to follow whatever spec sheet the battery has.

I prefer to not draw batteries below 50%. At 11.5 volts on a FLA battery, that is just above 10% SOC, 90% DOD. Going below 50% is supposed to significantly reduce the life of a battery. My chart puts 50% DOD at 2000 cycles, and stops at 20% DOD is 1000 cycles. 10% is not listed. Not somethign I want to do when spending over $1k for four GC2H golf cart sized solar batteries, or even cheaper GC2 golf cart batteries from COSTCO.

I’m assuming an FLA battery. The Trojan user manual I have says a battery should be equalized monthly. When I did equalize you could here it bubbling, which is certainly circulating the electrolytes.

I did not equalize monthly. I did add water monthly and check specific gravity, and this is a good way to circulate the electrolyte. Take it into and eject from the hydrometer three times before measuring. If the electrolyte is out of tolerance, than equalize. Mine was almost perfectly matched for the 18 months I had the batteries and only equalized once.

When not cycled on a regular basis

Is discharging to 11.5 volts a technique you use frequently and your batteries have lasted for years? If so, then you are correct; otherwise I can only go off what is on spec sheets and user manuals. Too expensive for me to experiment. If it works for you, I’m still reluctant to experiment off one good result.

I think the most important thing is to follow whatever spec sheet the battery has.

I prefer to not draw batteries below 50%. At 11.5 volts on a FLA battery, that is just above 10% SOC, 90% DOD. Going below 50% is supposed to significantly reduce the life of a battery. My chart puts 50% DOD at 2000 cycles, and stops at 20% DOD is 1000 cycles. 10% is not listed. Not somethign I want to do when spending over $1k for four GC2H golf cart sized solar batteries, or even cheaper GC2 golf cart batteries from COSTCO.

I’m assuming an FLA battery. The Trojan user manual I have says a battery should be equalized monthly. When I did equalize you could here it bubbling, which is certainly circulating the electrolytes.

I did not equalize monthly. I did add water monthly and check specific gravity, and this is a good way to circulate the electrolyte. Take it into and eject from the hydrometer three times before measuring. If the electrolyte is out of tolerance, than equalize. Mine was almost perfectly matched for the 18 months I had the batteries and only equalized once.

Yes. I manage over 100 batteries in intermittently used equipment.

I will say the new battery tenders are much better at not boiling over batteries.

I will also say we have a pistenbully snowcat that has 8 year old costco batteries in it and it just sits there 9 months out of the year with no tender...no nothing and they are still fine.

When reaching conclusions, battery quality plays a big role. We have 4 Deka vrla's that go completely dead in 3 months if left without a tender. They charge right up and load test fine but they have a huge self-draw.

 

[Substrate]

When reaching conclusions, battery quality plays a big role. We have 4 Deka vrla's that go completely dead in 3 months if left without a tender. They charge right up and load test fine but they have a huge self-draw.

That means your high-quality Deka's have been improperly charged and maintained. Easy to do if you are playing around with intermittent maintenance - and especially so if you are not the first owner.

Applying a maintainer to one in neglected shape - despite being able to support a starting application (assuming you know the difference between a C/20 cycle test, and a starter-load test) is the reason.

Some maintainers, like the real Battery-Tender brand, stay in absorb until about 100ma of tail current is reached, before dropping to 13.4v float. Even at 100ma, if the Deka has been improperly maintained, that is enough to gas out highly unbalanced and hard-sulfated internal cells. One cell goes into a never-ending recombination, and eventually blows the seal. And now never recharges properly.

I'm just saying to be careful throwing out your brand quality assumptions.

Far too many times the problem is improper maintenance from the get-go, mis-application, or the things slapped on a battery as a bandaid for it.

 

[Checkthisout]

That means your high-quality Deka's have been improperly charged and maintained. Easy to do if you are playing around with intermittent maintenance - and especially so if you are not the first owner.

Applying a maintainer to one in neglected shape - despite being able to support a starting application (assuming you know the difference between a C/20 cycle test, and a starter-load test) is the reason.

Some maintainers, like the real Battery-Tender brand, stay in absorb until about 100ma of tail current is reached, before dropping to 13.4v float. Even at 100ma, if the Deka has been improperly maintained, that is enough to gas out highly unbalanced and hard-sulfated internal cells. One cell goes into a never-ending recombination, and eventually blows the seal. And now never recharges properly.

I'm just saying to be careful throwing out your brand quality assumptions.

Far too many times the problem is improper maintenance from the get-go, mis-application, or the things slapped on a battery as a bandaid for it.

What kind of maintenance should I be doing to the Dekas and what was neglected vs the costco batteries in our snowcat that I know are neglected but do not self-discharge?

We are open to any all advice so long as it's something i can chew on.

 

[Substrate]

No problem - here are two classic documents, and there are clues for two common issues with Deka's, especially in regards to VRLA (Gel or AGM).

The "1927" (not the year!) document is generic info, BUT sharp-eyed users will note the recommendation to recharge at 0.3C for best results. What this implies, and is often missed by consumers less knowlegeable than you or me, is to not try to charge one from a deep discharge with a maintainer current. I know you aren't doing this.

https://www.dekabatteries.com/assets/base/1927.pdf

And here is the other classic, the 1913 pdf document. (again, not the year).

https://www.eastpennmanufacturing.com/wp-content/uploads/Renewable-Energy-Charging-Parameters-1913.pdf

An initial issue that is often missed, is that Deka / East Penn agm's have a top CV limit of 14.4v. Temp compensated.

BUT, a lot of maintainers that have "AGM" settings or labeled "designed for AGM", may have a CV that does to 14.6v. That's a small enough difference to make them go rice-crispy.

So if one is choosing a maintainer, and using them on Deka's, you want to make sure you are at the right CV voltage - which may differ from the "canned" settings of something say normal vs agm.

Example - my favorite maintainers are from "Battery MINDER" - their algo's are tight, AND they usually come with a remote temperature probe! Perfect. But they make models that are 14.4, 14.6 and so forth. Choose the right one for the Deka based on voltage, not a canned "agm model - since that may mean a higher 14.6v which other agm's are usually spec'ed to.

Example: Their 2012-AGM model has a CV of 14.7v. Their standard 2012, designed for flooded, has a CV of 14.4v The Deka agm will like the standard model. Fortunately, one can read the users manual detailing the actual CV in use, and decide based on that. Check it out:

https://www.batteryminders.com/content/manuals/2012-AGM.pdf

Note - you can safely ignore the desulfation hoopla associated with the Battery Minder brand. The underlying main algo, temp comp, timeouts etc are SOLID. For most battery nerds, this desulfation feature can be considered a "value add" feature or a reason to overlook them. Ignore that feature if you like.

Pretty sure that the average Battery-Tender brand models go up to 14.6, so lookout. Not recommended for Deka's, although most consumers won't know or care. At one point, they even had "gel specific" models at 14.1V cv.

It's all these little details that drive us battery nerds like you and me nuts. But it pays off!

 

[Substrate]

Heh, if Will ever gets bored, we can drag him kicking and screaming back into VRLA land.

"Look at this you guys - this 2012-agm maintainer is cooking my Deka's well past their 14.4v CV limit. Putting my ear close, you can hear the rice-crispies!". If one is going to do this, for a Deka, it's better to use the standard flooded 2012 model! "

 

[Vigilant24]

Now how to power those two AC chargers when off-grid...yep, a generator. A good friend of ours gave us a screaming deal on a Honda 2000W (peak 4000W) generator. Those things are the quietest things on the market. And I plan to build an insulated box to put over it (need to vent the exhaust) which will cut the minimal noise to almost nothing. Or if you're stationary, you could dig a hole, put the generator in it, vent the exhaust and put an insulated lid on top.

The sound muffling enclosure would be an interesting project. Obviously, the challenge is providing for the airflow while trapping te sound. I'd guess baffles/turns would be key, along with the right materials. I think it would be worth experimenting with "rock wool" (aka "mineral wool") insulation. It can be pulled into approx 1" thick sheets (wear gloves), it is dense and has lots of nooks/crannies, and it will not burn under any conditions it's likely to encounter in this application, I'd think.

These inverter generators start by making alternating current (with an alternator driven by the engine), that gets converted to DC with a rectifier, and then it gets converted again using an inverter similar to the types you'd use to convert your battery current to 120 VAC. It's crazy. And then we propose to take that AC from the generator and convert it BACK to DC to charge a battery. It's kooky, and amazing it works at all. It's too bad the
generators don't just tap into the DC and have a buck converter/battery charger output in addition to the AC plugs. It would be ore efficient for charging batteries and, as a plus, provide another way to get power if the inverter in the generator fails.

It would be an interesting project to hack into an inverter generator to do that. There are no new ideas under the sun, so I'm sure someone a lot brighter than I am has done it.

 

[Checkthisout]

The sound muffling enclosure would be an interesting project. Obviously, the challenge is providing for the airflow while trapping te sound. I'd guess baffles/turns would be key, along with the right materials. I think it would be worth experimenting with "rock wool" (aka "mineral wool") insulation. It can be pulled into approx 1" thick sheets (wear gloves), it is dense and has lots of nooks/crannies, and it will not burn under any conditions it's likely to encounter in this application, I'd think.

These inverter generators start by making alternating current (with an alternator driven by the engine), that gets converted to DC with a rectifier, and then it gets converted again using an inverter similar to the types you'd use to convert your battery current to 120 VAC. It's crazy. And then we propose to take that AC from the generator and convert it BACK to DC to charge a battery. It's kooky, and amazing it works at all. It's too bad the
generators don't just tap into the DC and have a buck converter/battery charger output in addition to the AC plugs. It would be ore efficient for charging batteries and, as a plus, provide another way to get power if the inverter in the generator fails.

It would be an interesting project to hack into an inverter generator to do that. There are no new ideas under the sun, so I'm sure someone a lot brighter than I am has done it.

I rented a Genie tow behind lift that had an si alternator hooked via belt to a Honda engine.

This isn't more efficient than an inverter generator with automatically varying throttle

 

[Vigilant24]

Example - my favorite maintainers are from "Battery MINDER" - their algo's are tight, AND they usually come with a remote temperature probe! Perfect. But they make models that are 14.4, 14.6 and so forth. Choose the right one for the Deka based on voltage, not a canned "agm model - since that may mean a higher 14.6v which other agm's are usually spec'ed to.
.....

Note - you can safely ignore the desulfation hoopla associated with the Battery Minder brand. The underlying main algo, temp comp, timeouts etc are SOLID. For most battery nerds, this desulfation feature can be considered a "value add" feature or a reason to overlook them. Ignore that feature if you like.

Regarding BatteryMINDer: They don't appear to sell any products with outputs above 8 amps, and those are priced at above $200. Apparently they can service multiple batteries using a proprietary Y cord(s). So, do you do your bulk charging with something else and just use these as maintainers?
For my two $90 110AH 12V batteries I'd probably go with something else, but I can see the attraction for bigger requirements.

 

[Vigilant24]

I rented a Genie tow behind lift that had an si alternator hooked via belt to a Honda engine.

This isn't more efficient than an inverter generator with automatically varying throttle

Yeah. But if that OTS Honda inverter generator would let you tap into the DC voltage directly and perform the throttle management just as it does now to keep that internal DC voltage stable while it powered the battery charger, it would be the bee's knees for folks needing to charge batteries. Failing that, just providing a tap into a steady 12VDC that could handle full generator output amperage would be useful. An aftermarket 12VDC to XXVDC smart battery charger would complete the package.

Even a "small" light 1000W generator could provide about 60A at 15VDC. That's enough to charge a 300 AH battery at 0.2C and keep it very happy.

 

[Checkthisout]

Yeah. But if that OTS Honda inverter generator would let you tap into the DC voltage directly and perform the throttle management just as it does now to keep that internal DC voltage stable while it powered the battery charger, it would be the bee's knees for folks needing to charge batteries. Failing that, just providing a tap into a steady 12VDC that could handle full generator output amperage would be useful. An aftermarket 12VDC to XXVDC smart battery charger would complete the package.

Even a "small" light 1000W generator could provide about 60A at 15VDC. That's enough to charge a 300 AH battery at 0.2C and keep it very happy.

Yeah. But if that OTS Honda inverter generator would let you tap into the DC voltage directly and perform the throttle management just as it does now to keep that internal DC voltage stable while it powered the battery charger, it would be the bee's knees for folks needing to charge batteries. Failing that, just providing a tap into a steady 12VDC that could handle full generator output amperage would be useful. An aftermarket 12VDC to XXVDC smart battery charger would complete the package.

Even a "small" light 1000W generator could provide about 60A at 15VDC. That's enough to charge a 300 AH battery at 0.2C and keep it very happy.

Nobody would buy it.

You might save 5% in fuel and be limited to one specialized task.

There isn't much power loss in those 3 conversion processes. Ponder how much heat your inverter and charge controller give off and convert that to watts.

If the batteries you were charging were not right next to the generator you get a lot of voltage loss and have to spend more money on large cables.

It's easy to homebrew a gen/ engine battery charger. They aren't worth the hassle.

 

[MurphyGuy]

Nobody would buy it.

You might save 5% in fuel and be limited to one specialized task.

There isn't much power loss in those 3 conversion processes. Ponder how much heat your inverter and charge controller give off and convert that to watts.

If the batteries you were charging were not right next to the generator you get a lot of voltage loss and have to spend more money on large cables.

It's easy to homebrew a gen/ engine battery charger. They aren't worth the hassle.

Generac just came out with a DC generator.

https://investors.generac.com/news-releases/news-release-details/generac-unveils-new-pwrgenerator-designed-dramatically-extend

 

[Checkthisout]

Generac just came out with a DC generator.

https://investors.generac.com/news-releases/news-release-details/generac-unveils-new-pwrgenerator-designed-dramatically-extend

Well ok. Shows my narrow-minded thinking.

How does it work?

I'll read up on it.

Edit: No, I'm pretty smart. That generac dc generator outputs 380 volts dc.

 

[Checkthisout]

Heh, if Will ever gets bored, we can drag him kicking and screaming back into VRLA land.

"Look at this you guys - this 2012-agm maintainer is cooking my Deka's well past their 14.4v CV limit. Putting my ear close, you can hear the rice-crispies!". If one is going to do this, for a Deka, it's better to use the standard flooded 2012 model! "

I'll get a photo tommorrow. We don't tender those Dekas. They are in a military vehicle called a growler. It's 24 volt so it's two in series.

I installed a battery switch as we do on most our rigs thinking (but without checking) that it had a parasitic draw. Nope.

Totally disconnected, they go dead after a few months. They gobble up a charge and were back in business but a few months later dead.

The vehicle arrived to us and the batteries were brand spanking new. I was happy since Dekas are supposed to be good.

Two batteries I know are good.

Old Panasonics and Yuasa.

 

[hyberlut]

The sound muffling enclosure would be an interesting project. Obviously, the challenge is providing for the airflow while trapping te sound. I'd guess baffles/turns would be key, along with the right materials. I think it would be worth experimenting with "rock wool" (aka "mineral wool") insulation. It can be pulled into approx 1" thick sheets (wear gloves), it is dense and has lots of nooks/crannies, and it will not burn under any conditions it's likely to encounter in this application, I'd think.

I've only watched one youtube video so far, but the guy built his box with some sort of non-combustable lightweight board. Double-walled, wall filled with basic fiberglass insulation. He put an extension tube on the exhaust of the generator and cut a hole in the box all the way to the ground. No other vents. The hole must've been big enough to allow enough air in. He had a very noisy generator and it made a huge difference. It would make a Honda be nearly silent in comparison.

 

[Substrate]

Regarding BatteryMINDer: They don't appear to sell any products with outputs above 8 amps, and those are priced at above $200. Apparently they can service multiple batteries using a proprietary Y cord(s). So, do you do your bulk charging with something else and just use these as maintainers?

Yes, your bulk charge is usually done with the vehicle's own chaging circuit, or other bulk charger, so these maintainers are applied afterwards to finish the job, and in the case of AGM or Gel, get that so important last 1% of charge in safely and smartly. And of course float.

The splitter cables last I looked incorporated fuses in each separation, so if any battery suffers a shorted condition, the other or rest of the batteries being maintained won't dump their load through the tiny maintenance wiring, and set them on fire or turn into a fusible link!

For my two $90 110AH 12V batteries I'd probably go with something else, but I can see the attraction for bigger requirements.

There are many options depending on how critical your battery care is. A real contender, and my personal favorites are Tecmate / Optimate charger and maintainers. I'm in love with the 30 minute on/off duty cycle of float that they use amongst all the other testing features.

Then there's the step down to more simplistic things. Just make sure the CV fits with what your battery manufacturer recommends. As in the case of Deka, it can be easily exceeded if one isn't careful and check.

 

[Goboatingnow]

I saw that Will P referenced this in one of his videos, and I need to learn more to understand it. It seems to me that each charge controller needs to periodically monitor the battery voltage to determine the state of charge, and if charge controller B is feeding the battery a higher voltage then charge controller A would see that as the actual battery voltage, which would be inaccurate. Probably too simplistic (maybe the pulsed high voltage of the "active" charge controller is cancelled out and the "sensing" charge controller just chooses the lowest voltage senses over the monitoring period as being the voltage of the battery? Seems pretty sophisticated for this application).

Multiple charge controllers is appealing to me for this application, since it allows for redundancy, and because I have shading issues. Charge controllers seem to be largely priced linearly per amp, so getting a few smaller ones doesn't come at a big premium over a single bigger one.

.

Anyone suggesting this is how paralleled charge sources work clearly has no understanding of basic DC circuit analysis theory , Kitchoffs laws etc.

A large battery battery controls the battery terminal voltage not the charge source as the battery is a “ load” from the point of view of the system under charge

Hence to proclaim what Will P said is to demonstrate his extremely poor understanding of dc circuit analysis.

 

[Checkthisout]

Anyone suggesting this is how paralleled charge sources work clearly has no understanding of basic DC circuit analysis theory , Kitchoffs laws etc.

A large battery battery controls the battery terminal voltage not the charge source as the battery is a “ load” from the point of view of the system under charge

Hence to proclaim what Will P said is to demonstrate his extremely poor understanding of dc circuit analysis.

Bruh, lighten up......