Need help understanding this.

[Jemplayer]

Here is the deal.


I have two separate solar systems in two houses close to each other.

In one house I have a set of 8 Trojan L16H-AC 435ah batts in series for 48V, this set is 6 months old.

In the second system I have a set of 8 Trojan L16 RE-B 370ah in series for 48V, this set in one month old.

Both battery banks fully charged to SG of 1,280 temp compensated.

After a 15 hour nightly discharge totaling 90AH on each bank on the same day under indentical conditions (i.e hourly draws match etc) , the SG readings on both banks are exactly the same 1,240 temp compansated.

Does the 370ah actually then have a capacity closer to 435ah? As SG reading indicates a 20% discharge on both sets despite one has less capacity. Therefore SG on 370ah RE-B should be a bit less, NO?

SunKing??????

[Sunking]

OK a couple of questions I need to know to give a decent answer and educated guess.

How do you know each battery is delivering exactly 90 AH? I find that odd unless the load device is say something like a 270 watt light bulb on a timer.

Are the two different loads discharging at the same rate? Example both are 5.625 amps for 16 hours.

At this point my best guess is Peukerts Law is at play, and/or your loads are not identical as you may think. Best I can do based on the limited information you have given.

[Jemplayer]

OK a couple of questions I need to know to give a decent answer and educated guess.

How do you know each battery is delivering exactly 90 AH? I find that odd unless the load device is say something like a 270 watt light bulb on a timer.

Are the two different loads discharging at the same rate? Example both are 5.625 amps for 16 hours.

At this point my best guess is Peukerts Law is at play, and/or your loads are not identical as you may think. Best I can do based on the limited information you have given.

Total AH drawn is taken from the Victron battery monitors on each sys. As for how aligned the actual hourly draws are, well, let's say, too close that in would effect, houses are mirror builds and have same appliances lights etc and and base draws.

I did the test because, I had he 435ah set in my main house for a time and the morning SG was always around 1,240, as I was using 20% a night. When I moved them over and put the new 370ah bank in my main house I noticed the Morning SG reading where the same as the larger Ah set.

Thinking it cannot be, and wanting to understand these things, I did the test, which confirmed it.

The best I can come up with is the AH ratings are "approximate" and maybe a bit of marketing to distinguish the models over each other. Its all I got.

Basically, the 370ah battery is performing as well as the larger 435 ah bank. I don't know why, but the reading don't lie and the tests were reliable.

[Jemplayer]

Can no one with more experience provide any insight here?

Is there some basic principle I am missing? We measure batteries SOC by SG values, then according to this, these two batteries have equal capacity, or at least very close, closer than the manafactrutes ratings would suggest.

So if your in the market for one of these models and concerned over the reduced capacity of the RE-B, it would seem don't be. They are almost identical, according to the metrics available to measure.

[SunEagle]

While I do not have experience with either of those batteries I would guess that the RE-B is a better design.

So the question comes to me as to what is the cost difference between the 435Ah and the 370Ah?

[Jemplayer]

While I do not have experience with either of those batteries I would guess that the RE-B is a better design.

So the question comes to me as to what is the cost difference between the 435Ah and the 370Ah?

There is the thing. This is why I posted this. They are much the same cost, and often compared, so thought my findings as detailed in original post my be relevant to someone looking at both.

Its a head scratcher for sure.

[sensij]

I don't have any experience to help. It seems like the difference in age could potentially be a factor, especially if the RE batteries have a better cycle life. Maybe in 6 mo or so you could do the test again and see how things look at that time?

[Sunking]

Sorry for the delay, holiday. The answer lies in the specs. Look at the weights.

The LR16H-AC is signature line, and LR16RE-B is a premium line battery. RE line has more lead in them and underrated with a lot longer warranty. Go to the Industrial line of like capacity and the Industrial line is even heavier. It is the amount of lead.

[SunEagle]

The only hint that the REB is better is mentioned on the spec sheet where it claims Improved Performance and an 8 year life. They also show a life cycle chart based on the DOD% while the HAC just shows performance discharge curve.

I expect the REB to be geared toward solar allowing for many daily cycles while the HAC was an earlier design.

[SunEagle]

Sorry for the delay, holiday. The answer lies in the specs. Look at the weights.

The LR16H-AC is signature line, and LR16RE-B is a premium line battery. RE line has more lead in them and underrated with a lot longer warranty. Go to the Industrial line of like capacity and the Industrial line is even heavier. It is the amount of lead.

That may be but the HAC is actually heavier at 125lb compared to the REB at 118lb. Still that doesn't mention how much of the overall weight is in the plates.

[Sunking]

That may be but the HAC is actually heavier at 125lb compared to the REB at 118lb. Still that doesn't mention how much of the overall weight is in the plates.

I got your point, however do some comparisons. A 5% weight difference does not equate to a 15% capacity difference.

Something to ponder, Look at the T-105 and T-105RE same everything except for weight and warranty. The RE has 5 pounds more lead in it. Lastly look at the dimensions of the two LR16's, the RE-B is slightly larger.

[SunEagle]

I got your point, however do some comparisons. A 5% weight difference does not equate to a 15% capacity difference.

Something to ponder, Look at the T-105 and T-105RE same everything except for weight and warranty. The RE has 5 pounds more lead in it. Lastly look at the dimensions of the two LR16's, the RE-B is slightly larger.

Yeah I noticed the height of the REB was taller than the HAC so the plates are probably longer and bigger overall.

Amazing how something like more lead makes all the difference.

So back to the OP's question. It is possible that the two different 48V battery systems are producing similar Ah usage per day even thought they have a different Ah rating probably because of their construction and operational design.

[Sunking]

Yeah I noticed the height of the REB was taller than the HAC so the plates are probably longer and bigger overall.

Amazing how something like more lead makes all the difference.

So back to the OP's question. It is possible that the two different 48V battery systems are producing similar Ah usage per day even thought they have a different Ah rating probably because of their construction and operational design.

Simple Premium Line AH are underrated. If you were to do a full discharge test on the T-105 and T-105RE, the RE will have more capacity.

Additionally age will make a difference. A RE actually gains capacity for the first 25 to 50 cycles, and Trojan recommends several deep discharges to form the plates. It comes down to you get what you pay for. Industrial Line is top quality followed by Premium line followed by Signature line. The OP has Signature and Premium Line aka Apples and Oranges. I am not surprised at his observations.

[Jemplayer]

I got your point, however do some comparisons. A 5% weight difference does not equate to a 15% capacity difference.

Something to ponder, Look at the T-105 and T-105RE same everything except for weight and warranty. The RE has 5 pounds more lead in it. Lastly look at the dimensions of the two LR16's, the RE-B is slightly larger.

This maybe true per Ah? But overall, the L16H-AC is heavier than the RE-B.

RE- B = 54kg
L16H-AC = 57

And the height difference is only due to the different terminals, the case is identical.

so the signature line battery does seems to have 3kg more lead than RE-B. But as Sunking points out, is this 5% increase in weight (assuming its lead) equal to 18% increase in AH

So back to the head scratching?

[Sunking]

RE line is under rated. The RE line has fewer but thicker/heavier plates aka less surface area, thus less capacity. Battery warranties are based on 80% capacity. Now take a look at the warranties. Signature Line is 12/24, and Premium is 24/60 or 250% longer. FWIW Industrial is 36/96. Premium Line has more lead per AH capacity. Again look a T-105 and T-105RE. Same exact capacity but the T-105RE is heavier in the exact same case. More lead per AH, 5 pounds more in the T-105RE. The Premium Line has more lead to work with.

If you did a capacity test the RE battery will have more than specified. That leaves them more room and time to meet 80% capacity for warranty.

So quit scratching your head.