Battery Management

[jviss]

Dave, perhaps you misspoke. There is no such things as "[a]pplying constant current at 14.7 v" or "constant current voltage for the AGM batteries you have is 14.4v."

By definition, due to the nature of FLA batteries, at constant current the voltage will change (increase) constantly. You can't hold constant current and constant voltage simultaneously.

If you look at the graphs you quoted, they two plots are occurring simultaneously, and show that during the bulk stage the current is held constant and the voltage increases over time. The bulk stage is terminated when the absorption voltage is reached, and this begins the absorption phase, which is the constant voltage phase. You see here that at constant voltage the current declines as the battery absorbs charge. This constant voltage is recommended to be 14.8 for the Trojan FLAs, and from 14.1 to 14.7 for the Battmaxx AGMs.

Holding the AGMs at 14.7 during absorption at 25°C is within spec for these batteries, and will not damage them. Similarly, holding the FLAs at 14.7 during absorption will not chronically undercharge them. This 0.1V difference is certainly within the measurement error and temperature variability we will see on sailboats. (Of course, you could optimize things with battery temperature feedback to the charger.)

 

[jviss]

That analyzer appears to be a capacitive tester.

It is not. It's a fairly sophisticated (and expensive) tester that measures the internal resistance of the battery by applying a 100A load for a millisecond or so. It is probably the best test you can do except for an actual 20 hour load test.

 

[Maine Sail]

The charging profiles are, remarkably, the same, at least WRT to voltages.

I would not put a lot of faith in the BattMaxx AGM's, longevity wise. The only inexpensive imported AGM batteries we've seen that survive well in deep-cycle use are the Fullriver or Rolls AGM's. With these AGM batteries an ACR will work just fine for charging purposes. Trojan flooded and the BattMaxx batteries are comparable absorption voltages. You may need to route charging to the AGM's first so as to minimize relay cycling, unless you have a pretty beefy alternator.

 

[Maine Sail]

It is not. It's a fairly sophisticated (and expensive) tester that measures the internal resistance of the battery by applying a 100A load for a millisecond or so. It is probably the best test you can do except for an actual 20 hour load test.

As we discovered, the Argus (who were basically sued out of business for stealing proprietary Midtronics information), and others that do this, are all over the map and sadly, do not translate well to SoH as related to deep cycle use.

Are Conductance Testers Worth It?

 

[MightyMike]

Hello, neighbor.
Just noticed you back on the mooring yesterday. Best Times has a similar, though much simpler set up as you are envisioning. It has a standard two bartery setup controlled through a 1-2-both switch. There is an independent bank charged by a solar panel. There is simple switch to choose the engine charged or solar charged banks to run loads. It was installed by the previous owner to solve your use case - to assure power to run sailing instruments and lights without running down house batteries.
It has worked well in the years I have owned the boat.

 

[Maine Sail]

Properly named, there are 3 stages to charging, constant current, constant voltage, and float.

The constant current voltage for the AGM batteries you have is 14.4v. Typical constant current voltages for FLA batteries is 14.7-14.8v.

No such thing... You can have a bulk transition voltage, where the charger switches from CC mode to CV but in bulk/CC voltage is always rising. The graph you posted very accurately describes this...

Applying constant current at 14.7 v to your AGM batteries will damage them. End of story.

Constant Current = The maximum current the charge source can deliver to the batteries

Constant Voltage = Voltage is held at a constant value by the regulation circuitry

In the rest of the world there’s actually a DIN standards that defines the charging process and it looks like this; I, Uo, U

I = Constant Current, CC, Bulk or sometimes called Boost Charging

Uo = CV/Constant Voltage, Constant Over Voltage, Absorption, Acceptance or sometimes Topping Charge

U = CV/Constant Voltage, Float, Finishing Charge or sometimes Maintenance Charge

It is important to note that under all definitions, whether DIN or the US terminology bulk charging is not governed by voltage being held steady, it is limited only by the charge sources current output capability. During bulk charging, using real definitions, not made up definitions by a marketing department, voltage is always rising during bulk charging, voltage is never constant in bulk.

BULK = MAXIMUM CHARGE SOURCE OUTPUT WITH VOLTAGE RISING

As to voltage of AGM's, there are numerous brands of AGM batteries designed to be charged at 14.7V +/-, and yet others where 14.2V or 14.4V is the maximum. Brand, model and manufacturer specifications are important whenever discussing charging.

This is why the typical "dip-switch" chargers with only an AGM, GEL and Flooded setting fail end users everyday by very often charging batteries at the wrong voltages.

 

[jviss]

As we discovered, the Argus (who were basically sued out of business for stealing proprietary Midtronics information), and others that do this, are all over the map and sadly, do not translate well to SoH as related to deep cycle use.

Are Conductance Testers Worth It?

Ugh! I bought this (I actually have two, an AA500 and and AA300) based on your recommendation! Oh, well, at least I know what I have now. It's not likely I'll ever do a 20 hour load test during hte season, but at home in the winter, yes. I built my own test rig with a battery quartz clock and a couple of low voltage disconnects.

 

[dlochner]

No such thing...



Constant current is........ current

There are numerous brands of AGM batteries designed to be charged at 14.7V, and yet others where 14.2V or 14.4V is the maximum.. Brand, model and manufacturer specifications are important whenever discussing charging. I've not yet seen what brand/model the AGM batteries are that are being discussed.

I'm still learning this, and perhaps I was not clear in my language. The manual for JViss's battery provides a table (see prior post with screenshot) where the "Bulk" charging voltage is listed at 14.4 v @ 77° F. The graph shows a constant current level and a rising voltage. As I understand this stage of the charging process, the voltage starts low with a high current and as the battery charges, the voltage rises to the "Bulk Charging Voltage" which I reported as the Constant Current Voltage, meaning the voltage at which the charger changes from providing a constant current to a constant voltage with a declining current.

What struck me as odd, was the the absorption voltage was higher than the bulk voltage.

With respect to battery charging, the problem seemed to me, that using an ACR would not allow either the FLAs or the AGMs to be properly charged. If the Bulk voltage is set to 14.8 for the FLAs, then it would be over charging the AGMs and if it was set to 14.4v for the AGMs, the FLAs would be under charged. I suggested way back in the thread that using a battery to battery charger could deal with this concern, pick one bank and charge it properly and let the b2b charger take care of the other bank.

One other note, when I referred to the battery analyzer I used capacitive tester, I meant conductance.

 

[jviss]

Hello, neighbor.
Just noticed you back on the mooring yesterday. Best Times has a similar, though much simpler set up as you are envisioning. It has a standard two bartery setup controlled through a 1-2-both switch. There is an independent bank charged by a solar panel. There is simple switch to choose the engine charged or solar charged banks to run loads. It was installed by the previous owner to solve your use case - to assure power to run sailing instruments and lights without running down house batteries.
It has worked well in the years I have owned the boat.

Hi there! Yes, we were launched May 29th. I missed this past weekend. I'll say hi if I see you there.

On my electrical panel are plus and minus bus bars connecting each vertical column of breakers. They are connected together at the bottom with wire jumpers. So, it is a simple matter to shuffle breakers around and segregate loads into load groups to be fed with different power sources.

 

[Maine Sail]

Ugh! I bought this (I actually have two, an AA500 and and AA300) based on your recommendation! Oh, well, at least I know what I have now. It's not likely I'll ever do a 20 hour load test during hte season, but at home in the winter, yes. I built my own test rig with a battery quartz clock and a couple of low voltage disconnects.

Think of how much money we spent! Sadly we were misled & blatantly lied by these manufacturers, and it was not just us, but the ABYC as well. We only discovered these gross inaccuracies because we are one of only a handful of marine electrical businesses in the country that actually perform 20 hour testing to BCI testing standards.

They still work well at predicting cranking capacity, and our Midtronics does a lot of other useful stuff, but cranking capacity can't be easily translated into low load deep-cycle use SoH..

 

[jviss]

where the "Bulk" charging voltage is listed at 14.4 v @ 77° F.

Yes, that table is misleading. I think what they are saying is to terminate the bulk phase at 14.4V and let the batteries float up to the absorption voltage once that phase begins. But I can't be sure, and it is confusing.

 

[Maine Sail]

I'm still learning this, and perhaps I was not clear in my language. The manual for JViss's battery provides a table (see prior post with screenshot) where the "Bulk" charging voltage is listed at 14.4 v @ 77° F. The graph shows a constant current level and a rising voltage. As I understand this stage of the charging process, the voltage starts low with a high current and as the battery charges, the voltage rises to the "Bulk Charging Voltage" which I reported as the Constant Current Voltage, meaning the voltage at which the charger changes from providing a constant current to a constant voltage with a declining current.

14.4V is their rather cryptic and meaning less, perhaps Chinese/English, bulk transition point. They are suggesting they want the charger to switch to CV at 14.4V but then go onto say an absorption (CV) of 14.1V to 14.7V is what's next.

They should know that if you set the CV stage to 14.5V, 14.6V or 14.7V then it won't stop bulk charging at 14.4V and it will just continue on until 14.7V is attained.

There are a few charge regulators on the market that can be set for a 14.4V (bulk transition point), then drop lower, such as 14.1V (Balmar regulators for example) but charging any AGM battery for PSoC type use at voltages below the max allowable leads to poor battery life.

Crypitc manuals that contradict themselves is why it is best to avoid buying batteries from companies like this.

What struck me as odd, was the the absorption voltage was higher than the bulk voltage.

Yep, bingo!

With respect to battery charging, the problem seemed to me, that using an ACR would not allow either the FLAs or the AGMs to be properly charged. If the Bulk absorption voltage is set to 14.8 for the FLAs, then it would be over charging the AGMs and if it was set to 14.4v for the AGMs, the FLAs would be under charged. I suggested way back in the thread that using a battery to battery charger could deal with this concern, pick one bank and charge it properly and let the b2b charger take care of the other bank.

But these batteries can be charged at 14.7V. Set the charge source to 14.7V and both banks can be charged together. A bit lower on the Trojan's than is idea but the Trojan's can be equalized and the AGM's can't be.. Yes, a B2B / DC to DC charger, like the Sterling ProBatt Ultra or the Victron Orion TR Smart can work but they are more expensive and for batteries that can charged at similar/same voltages there is little need for the extra cost. When we get into GEL / AGM or Flooded / GEL or LA /LiFePO4 or AGM/Flooded (Dissimilar voltages) then a B2B makes a lot more sense.

 

[dlochner]

As I was considering this, I took a look at the manual for Lifeline AGMs (a 40 page manual for a battery?) and noticed they didn't provide a bulk voltage, only an absorption voltage. They also provide absorption voltages for every 10°.

Again, thanks for your clarification. Perhaps by my next life battery manufacturers will have consistent language.

 

[Maine Sail]

As I was considering this, I took a look at the manual for Lifeline AGMs (a 40 page manual for a battery?) and noticed they didn't provide a bulk voltage, only an absorption voltage. They also provide absorption voltages for every 10°.

Again, thanks for your clarification. Perhaps by my next life battery manufacturers will have consistent language.

This is because Lifeline gets it and knows that bulk is constant current, not a constant voltage..... All batteries should be charged with temp compensation, and again, Lifeline gets it.

Sadly far too many charger manufacturers do not get it. For example on Monday I tossed out a 2.5 year old Xantrex TrueCharge 2 charger. It could not be properly programmed for the customers batteries, did not even come with a battery temp sensor and it was overheating and shutting down because the internal fan was already dead. Xantrex tech support, on the matter "out of warranty buy another". The customer now knows why when he asked us to install a Xantrex inverter we politely declined.

 

[jssailem]

Just when I think I have a basic handle on battery management you guys slip one in and I get a more informed view.

Thanks @jviss for wanting a bit more out of the systems you have... Thanks to Dave and Rod for the insightful questions and observations. I think this is powerful stuff. (no pun intended)

Once again the give and take of ideas shared about boat systems demonstrates what a valuable resource this SBO forum is.

 

[jviss]

From the original post:

For charging, the recommended voltages are pretty darn close, so I assumed I'd add an ACR.

This turns out to be true, agreed?

It would also be nice to be able to switch banks to loads in case there's a bank fault, similarly to the 1-2-BOTH-OFF scheme above.

I think this is a cool idea, especially with banks I don't want to combine unless charging.

I was thinking of splitting loads and running house loads like fridge, lights, stereo, etc., off one bank, and instruments, autopilot, radar, etc., off the other.

I think this is a cool idea, too.

 

[jviss]

Once again the give and take of ideas shared about boat systems demonstrates what a valuable resource this SBO forum is.

Thanks for your comment, John. I'm glad it was a good experience for you. For me, it makes me wonder why I bother.

 

[Stu Jackson]

For me, it makes me wonder why I bother.

Glad it all helped. Always why a healthy discussion is good. Thanks for bringing it all to the fore.

BTW, I almost got banned for saying just that the other day.

Keep up the good work.

Could you summarize for us just what you are going to do?

 

[jviss]

Thanks for your reply, Stu. I've had a time-out here, too.

I just find it distressing when folks jump in, rudely, at times, to tell you how wrong you are about things without the basic knowledge, and without the information about the components involved, when you've already done the research. So, here we are, 39 replies later and we're still pretty much where we began.

That's whey I summarized in post #36. As you well know, there is no one way to skin a cat, no single "correct" way to wire a boat and manage batteries.

There are several advantages to a layout with multiple banks, despite the fact that we've learned that the nearly century old regimen of switching banks on alternate days is not the best approach. But things change very slowly in the sailboat world. The advantages, in a system where you have multiple banks but use them both every day is that you have partitioned potential faults to affect only part of the boat, and can switch loads to the working bank if one has a fault; and, you can perform maintenance, including replacing batteries, without taking the whole system down or having to replace all the house batteries. It's the classic "don''t put all your eggs in one basket."

I'm going to draw what I am thinking of (I am trying out Kicad on linux right now; my mechanical 3D CAD system is lousy for schematics. If all else fails I'll use gimp or even Powerpoint/Google Sheets).

Meanwhile, this is mostly speculative at this point. I am thinking of the two banks, with the alternator and shore power charger connected to the FLA bank, and an ACR to the AGM bank. The banks would lead to two switches like BSS 6008 1-2-OFF. 1 and 2 would the the split of the DC panel, with my "house" loads on 1 and "sailing" loads on two, so I can energize either group of loads from one or the other bank. I'll keep the 1-2-BOTH-OFF and Starter Disconnect as-is on bank one and the starter battery, and keep the echo charger as-is to charge the engine batt from bank 1. Finally, I'll have a single photovoltaic array driving two Morningstar Sunsaver solar controllers (that I have), isolated by Schottky diodes, charging banks 1 and 2. I have to figure out how to prevent the ACR from activating when charging via solar. One of the controllers does an automatic equalization charge every 28 days and the other does not, so the former on the FLAs and the latter on the AGMs.

I could "close the loop" on this by adding a 1-2-OFF switch to select which bank is involved in the 1-2-BOTH-OFF existing scheme.

I know that might not all be clear, and a picture will help, when I make one.

There's the issue of the HUGE loads connected to my single bank now, the inverter and windlass, which I have addressed yet. It would be a bit nightmarish, in cabling and switches, to make them selectable for bank.

That's all I have at the moment.

 

[SBO Police Bot]

BTW, I almost got banned for saying just that the other day.

You are on thin ice because you took it to a personal level and attacked and insulted another poster, a new poster to this forum. There's zero tolerance for that type of behavior and you do know the rules.

"I simply could not help myself in venting my frustration over a truly boneheaded decision."