FireFly Carbon Foam Batteries

[tpbrady]

Back in June our 4 8D AGM house bank gave up after 8.5 seasons. Since the only way to get batteries into the boxes is to tilt them, I couldn't go with flooded batteries so that left me with either 6V or 12V AGMs or the Firefly Group 31 carbon foam. The least expensive non flooded route was 6V AGM's. However if you factored in the useable amp hours, they were only a $.01 less per usable AH based on 80% DOD for the Firefly's and 50% for the AGMs. Without going into a long story here is what I am seeing from the bank of 6 Firefly's (696AH total) over the last week:

The first column is the amps consumed as measured by a Link 2000. The second column is the percent remaining capacity on the Balmar Smart Gauge. The third column is the amps used based on remaining capacity predicted by the Smart Gauge (.2*696=139.2). 4th column is amps consumed per battery. 5th column is the number of hours, 6th column is average amps consumed per hour, and the last column is the average amps consumed per hour for each battery.

162 80% 139.2 27.0 17 9.5 1.6
149 86% 97.44 24.8 16 9.3 1.6
96 91% 62.64 16.0 10 9.6 1.6
117 85% 104.4 19.5 10.3 11.4 1.9
107 93% 48.72 17.8 11.5 9.3 1.6

What I don't understand is why the large discrepancy between the Smart Gauge and the amps consumed by the Link 2000 (all grounds are tied to the a shunt). In only one case are they close, 117 consumed versus a predicted 104. Any ideas out there?

Tom

 

[O C Diver]

There's an old saying that a man with 2 watches never knows what time it is.

The gauges use different programs to tabulate consumption and predict remaining power. While I can't speak to the Balmar Smart Gauge which I assume is the newer of the two, my guess is that Link 2000 may not be able to adjust for the Firefly chemistry. Both gauges were obviously able to interpret shunt information for open lead acid and AGM. One or both gauges may not be able to process the information based on being able to do deeper depths of discharge.

Ted

 

[Frosty]

That's interesting. For anyone who isn't familiar with it, the Smart Gauge doesn't use a shunt. Instead it uses "jillions" (my interpretation) of voltage readings plus an algorithm to give you SOC (which is its main function). It was invented by a canal boater in the UK.

(Not to be confused with the new Balmar SG200, which is shunt based and a different beast.)

I have a bank of three Group 31XT AGM's (375ah) and I have one Smart Gauge and one Victron BMV (shunt based) monitor.

So interesting chart. One question that came to mind is when are you looking at the SG's SOC percentage? I ask that because it is not accurate while charging (no surprise, designer states it) due to the way it works.

When do you look at the SG SOC percentages listed here? Is it during charging or shortly thereafter? (Just to rule that out.)

 

[tpbrady]

Frosty

I look at in the morning before starting the gen or main so charging isn’t involved.

Tom

 

[Gordon J]

I had a link 20 in last boat and found that it was accurate only after I recharged batteries 100%. It would start to go wrong after first discharge cycle. Since we were living on the hook, I estimate 1-2 percent per day.

I installed fireflies last year and use the smart gauge. I think it’s numbers are pretty accurate, but it took awhile for the gauge to “learn the batteries.” My bank is a combination of four group 31s and the 3 of the higher capacity L-15s. Total AH is about 930.

 

[Frosty]

Tom,

Okay, so reading the SG while charging is not the issue.

I had a link 20 in last boat and found that it was accurate only after I recharged batteries 100%. It would start to go wrong after first discharge cycle. Since we were living on the hook, I estimate 1-2 percent per day.

I hear you on that; but Tom isn't using the shunt-based gauge for SOC, but actually reading out the amps used for a given day. That should be completely accurate. But when he extrapolates amps used via the percentage on the SG, they don't completely agree (if I'm understanding correctly).

I suppose one issue could be if the Firefly bank capacity is not exactly what is claimed (not saying they duped you, but capacity changes can change things). Thinking out loud what if the bank capacity were 650ah....?. Then if you used 162 ah, that would put you at 488ah 80% of 650 is 520ah left. So okay, that's a nope for that theory.

Also, your inaccuracies are on both sides of the absorption start (about 85%).

Okay, I'm stumped for ideas, but I will let it percolate.

I don't actually pay much attention to my shunt-based gauge for how many amp hours used, so I can't say if I have that discrepancy or not. I mostly use it to see how many of my solar controller amps are going into the battery vs. going to loads or to check that I have no parasitic or unexpected loads happening. I can say that the SG seems accurate based on watching it's SOC percentage vs. when my charger goes into absorb. For example if the SOC is at 75%, then I know that after around 30 ah go in, I should hit absorb (my battery bank is six years old so no longer at full capacity). And that's about what happens. That's not super precise, but just saying I don't notice anything that makes me say "Huh?"

I wonder what that table would look like if you checked your gauges in the evening (after charging). Maybe no different....?

Definitely interested in how this thread goes.

 

[DDW]

The Link AH consumed is a measurement. The Smartgage AH consumed is a guess. I'd go with the measurement.

 

[Frosty]

The Link AH consumed is a measurement. The Smartgage AH consumed is a guess. I'd go with the measurement.

I agree that the shunt-based meter is a measurement, but I don't think I'd say the SG is a guess. Maybe it depends on how you define guess, but I'm just saying it's a bit more than that. I suppose I'd say it's an estimate based on an ongoing algorithm.

Maybe I should compare my Victron BMV (shunt-based) to my Smartgauge the same way you have, Tom. It might be interesting. Because like you, I'd be curious about how the figures compare.

 

[tpbrady]

I have a working theory that the SG doesn't accurately report SOC at low battery loading That may only be until it "learns" more. While that is only based on a single data point so far, when the load per battery went from 1.6 to 1.9 amps per hour the SG as compared to actual amps consumed were reasonably close together. When batteries are rated for amp hours it is based on draining the batteries over a time period at a constant current. The Firefly's are rated at 116AH at the 20hr rate, indicating a constant current of 5.8 amps for 20 hrs. Since most of my measurements are at an average current of 1.6 amps per battery that is 27.5% of the amps used for the 20hr rating. I had the one 1.9 amp hourly per battery consumption which brought the consumed AH on the Link 2000 closer to the SG SOC. If current draw is low per battery the SG may not be that accurate since the voltage impact is very small.

Sounds like a question for Balmar.

 

[Beaverlake]

Check out Panbo.com for a review of the new Victron device and a link to their review of the Balmar SG 200. It would appear that both devices have overcome some of the limitations to which you guys refer and the Victron unit has an app and Bluetooth connection - and it is surprisingly affordable. I’m thinking of adding one because I wouldn’t have to run any wires (the SG200 also has a BT option).

 

[dhays]

Tom, I am ignorant on electrical....


How long have you used the SmartGauge with the Firefly batteries? It is my understanding that it takes a while for its accuracy with a given bank to improve. The more times the bank is discharged to various depth of charge the better its algorithms get.


The other thing I don't know is if the SmartGauge works as well with carbon foam batteries. Also, did you use the SmartGauge on your prior bank? Might it need to be "reset" somehow with the new bank?


If CMS would chime in on this one, lots would be made clear I would assume.

 

[DDW]

I agree that the shunt-based meter is a measurement, but I don't think I'd say the SG is a guess. Maybe it depends on how you define guess, but I'm just saying it's a bit more than that. I suppose I'd say it's an estimate based on an ongoing algorithm.

Maybe I should compare my Victron BMV (shunt-based) to my Smartgauge the same way you have, Tom. It might be interesting. Because like you, I'd be curious about how the figures compare.

Perhaps "guess" is a little harsh, but it is a calculation inferred from other indirect measurements. The Link (or any shunt) is as accurate as the shunt (generally better than 1%). The marketing reason for the Smartgage is the assumption that most users will not bother properly to set up a shunt gage, and that the most important reported value is SOC. The former may be true, but I'd dispute the latter. SOC tells you little without also knowing your capacity, discharge rate, charge rates from various sources, etc.; and knowing that, SOC tells you nothing extra. After it learns, the SmartGage claim is that it more accurately reports SOC than a shunt gage. This may be true, but to me, accurate reporting of a useless number is not useful.

The new Victron is a shunt based system, just nicely packaged and connected. I thought the newest SmartGage also included a shunt, which suggests they've seen the light

In general, Victron is getting further and further ahead of it's competition.

 

[tpbrady]

Dave,

The SG actually has a setting for carbon foam batteries. I only have a week of operation so yes, it may get better over time.

DDW,

I agree with you on the shunt based measurements, and but SOC as calculated by the SG if it is more accurate, will show you degradation of the battery bank over time. It gets down to interpreting the data. With my last battery bank, if I had collected a little data over time, I think I would have seen the battery bank going down hill as in the end consuming 80 amps showed a SOC of 90% but consuming 100 amps showed a SOC of 70% and rapidly falling. At 120 amps we were at 10%. The Link 2000 thought everything was good, but the SG said we were toast. The old bank had a rated capacity of 800AH so it was only providing just shy of 15% of its capacity. What we need is a SG that uses data from a shunt to show that your rated battery capacity is degrading so you see a battery failure coming as opposed to see it actually happen. By understanding the comparison between the amps consumed from the Link 2000 compared to the SG SOC, I hope to see if the Firefly claims are truthful. I have no reason to doubt them; however, trust but verify.

Tom

 

[Frosty]

I have a working theory that the SG doesn't accurately report SOC at low battery loading That may only be until it "learns" more.

I've been using the Smart Gauge full time for 5 years now (along with the Victron BMV), and I have that exact same feeling/observation. I thought about mentioning it above, but don't really have "proof," you know?

But yes, if my loads are light for some reason (and batteries are full or nearly so), I think it sort of stays in charging mode. In other words it doesn't have enough "usage" data to work its algorithm.

Once I'm back to charge/use/charge/use in a heavier pattern it seems very good.

So for me, those "confused" times are when I don't really have any reason to worry, because either I'm charging or I'm only lightly loading. Not saying it wouldn't be be better if it were always dead on; but I can understand why it would not be able to really work its algorithm when inputs are not appropriate.

**************
The new SG200 looks really interesting, and is (as I understand it) kind of a combo of the two. Also it will work on LiFeP0 batteries where the original Smart Gauge will not. I still think the original has some things going for it. One is that for people who might not be willing/able/interested in installing a shunt-based meter (that's not the OP or me, but I think covers a number of people) the Smartgauge is a very simple install (two 14AWG wires to pos and neg of battery) that does give SOC in most circumstances.

I just like trying things and having data, so I went with them both back in 2014 or so. In a new setup it would be fun to try the SG200.

 

[sunchaser]

TP
Two questions:
Smart gauge questions aside, what are you finding for FF comparisons to FLAs? Are the NOAA guys after you this year?

 

[CMS]

What I don't understand is why the large discrepancy between the Smart Gauge and the amps consumed by the Link 2000 (all grounds are tied to the a shunt). In only one case are they close, 117 consumed versus a predicted 104. Any ideas out there?

Tom

Tom,

If you read this article carefully you will understand why the Ah counter and Smartgauge often disagree.

https://marinehowto.com/programming-a-battery-monitor/



.

 

[w8n4sun]

CMS, thank you for the link - very informative!

 

[tpbrady]

Tom,

I don't have much for a comparison but the FF are 250lbs lighter in total than the 4 8Ds they replaced and I had room in the battery boxes to add 8 ft of 2/0 cable to make the port and starboard cable runs to the battery switch the same length. On NOAA, the only NOAA vessel I have seen thus far was the fancy RIB from last year on a trailer in a parking lot in Sitka with a deflated port chamber.

CMS,

That was a good read and I need to look at it again to be sure I understand it. The premise seemed to be you need to constantly update the parameters in a SOC monitor to keep it accurate and periodically test battery capacity. Toward the end the answer I was looking for sort of popped out. The comparison between consumed amp hours and SOC is only valid for a specific set of conditions. Change the temperature, the load on the batteries and amps consumed from the batteries could be identical but the SOC different. The lesson in the article was at the end. Count amps so you know what you are using and if your charging system is working, and use the SG to figure out SOC unless you want to spend time updating your battery monitor system over time with new parameters.

Tom

 

[catalinajack]

I have followed the issue of battery monitoring for a long time. Here is what I have concluded based on some constants.

1. We know what our nominal capacity of our batteries are when new.
2. Nominal, yes, plus or minus, but the difference, in use, does not matter.
3. Batteries lose capacity over time but can be estimated to an amount that, again, with a difference from precision that does not matter.
4. Battery monitors such as the Victron BMV series can measure amps in and out accurately.
5. Working from an assumed battery capacity, adjusted for age from when new, one can know, with reasonable accuracy, when 50% of capacity has been withdrawn.

Therefore, does the Balmar Smart Gauge or the SG-200 tell us anything we cannot deduce for ourselves? The SG-200 does purport to calculate a State of Health (current battery bank capacity) but of how much value is that given that with the knowledge of its age and original capacity we can, generally, estimate its capacity with reasonable accuracy without the SG-200?

Just some musings. I do have a Smart Gauge that I installed before reaching the forgoing conclusions. I rarely even look at it.

 

[DDW]

DDW,

I agree with you on the shunt based measurements, and but SOC as calculated by the SG if it is more accurate, will show you degradation of the battery bank over time.

The Link will tell you all that, but requires some knowledge and interpretation. Simply looking at the voltage and AH down will give you a pretty good guess of capacity reduction. A coulomb counter gage requires interpretation of SOC, the Smartgage attempt to tell you that but you requires interpretation for everything else. What I want to see is AH consumed, discharge rates, charge rates, and voltages. Very rarely do I look at SOC. It provides very little information that the other measurements lack, while lacking much of the information the others provide.

 

[Joe Pica]

The only true determinate is to do a fixed drawn down test of each battery after no loads for 24 hrs.. Then recharge as directed and test again.
Good luck.

 

[Hippocampus]

Joe gots it right imho. However there are fairly accurate ways to get in effect a formal load test without doing a formal load test. Most boats have some parasitic draw even when you turn all available switches off. Truly disconnecting all batteries is a bit of bother. Most impressed by MaineSail’s website site. Seems to be extremely knowledgeable. Have been using a German system, Phillipi , to monitor batteries and all charging sources (wind, solar, generator and alternator. It also monitors engine, all tanks, battery temperature. Most impressive. result have matched residential capacity gotten by load testing and SOC.