How much water should I add to old AGM battery?

[GeorgeF]

I see this on their website. 400cycles 80%DoD. For a thin plate battery it is not bad. If I understand well the warranty period is 4 years

[inetdog]

One more question about the so called telecom thin plate pure led batteries like NS Red. According to specs able to 400 cycles DoD 50%. If during 5 years of service cycled lets say only 50 times can you still expect few hundred cycles after service?

Yes and No. Both discharge/recharge cycles and calendar time reduce the capacity and life of the battery. If the warranty is 5 years or 400 cycles, you may have little left (of the typical 809% of original capacity at End Of Life) after 5 years, regardless of the number of cycles. If the warranty is 10 years, then yes, you probably have 200+ cycles left.

[GeorgeF]

One more question about the so called telecom thin plate pure led batteries like NS Red. According to specs able to 400 cycles DoD 50%. If during 5 years of service cycled lets say only 50 times can you still expect few hundred cycles after service?

[inetdog]

Of course I considered that. I should have mentioned that a few of the caps on some batteries had popped off already when I opened the chassis. You can also see the green evidence of overflow on one of the pics I posted before. The surviving battery in question also popped a few caps while doing a prolonged charge. I think in their factory state there is no excess liquid in the cells and because they do not have to be re-filled during their lifecycle they can be called maintenance-free. However that does not mean they cannot overflow on a really hot day.

To me that indicates that the batteries have, at some point, been seriously overcharged. Under normal charging conditions (which may be substantially lower current as a function of capacity, C, for these telecom float batteries than for more typical AGMs intended for cycle service) any oxygen and hydrogen gas produced will be recombined without venting. If electrolyte is actually lost in the process, rather than just gases, I suspect that either the boil-off was particularly violent or the cells were inverted at the time (strongly not recommended!)
AGM batteries should NOT ever be subject to a high current/high voltage charging regime such as that recommended for equalization in a flooded (FLA) battery.

[sdold]

I think the two slots shown below function as the pressure relief valve by letting excess pressure escape past the sides of the cap, even with the cap held tightly by the cover. I bet they would pop off with even less pressure than that if the top was removed.

VRLA valve.jpg

[davethedrummer]

Have you considered the effect on the "flimsy little valve caps" of the plastic cover which you removed to expose them? When constrained from the top from simply popping off, I expect that the rubber caps could provide a very controlled pressure relief function.

Of course I considered that. I should have mentioned that a few of the caps on some batteries had popped off already when I opened the chassis. You can also see the green evidence of overflow on one of the pics I posted before. The surviving battery in question also popped a few caps while doing a prolonged charge. I think in their factory state there is no excess liquid in the cells and because they do not have to be re-filled during their lifecycle they can be called maintenance-free. However that does not mean they cannot overflow on a really hot day.

[inetdog]

I guess you can't really see from the pictures but the caps are made of very soft and elastic rubber that is less than 1mm thick. I seriously doubt those caps would withstand any kind of pressure. There are no valves that I can see, unless they are calling those flimsy little caps valves? Seems like a bit of a stretch of the term.

Maybe this is an older design? Would be interesting to see if the "valves" on the new Northstar batteries are also just thin rubber caps.

Have you considered the effect on the "flimsy little valve caps" of the plastic cover which you removed to expose them? When constrained from the top from simply popping off, I expect that the rubber caps could provide a very controlled pressure relief function.

[davethedrummer]

Once you have defeated the pressure relief valves, the battery will no longer be able to recombine the hydrogen and oxygen gas produced by electrolysis during normal charging. That means that you will soon have to add water again instead of having a sealed, maintenance-free battery. The volume of electrolyte compared to capacity is far smaller than in an equivalent FLA cell.

Like I said before, these aren't actual valves, they are just flimsy little rubber caps that provide basically no pressure resistance. Anyways I'm not expecting it to suddenly be like a new battery but for now it works and I saved a bunch of money by not having to replace it (at least in the short term).

[inetdog]

And,
how can such a tester defines the SoH in regard of degration, corrosion etc...???

Only to the extent that the deficiency in the battery increases the internal impedance of the battery.

[GeorgeF]

And,
how can such a tester defines the SoH in regard of degration, corrosion etc...???

[inetdog]

I did ask before about NorthStar Red. There are some resellers of used NS red. Ignorant PV users beleive that the SoH of these dumped batteries is 100% cause they show them pictures like this.

Can anyone explain me how is it possible that such kind of measuring tool can show a SoH of 100%?

I am deeply concerned about the 1000A and 1815A figures on the screen of the battery tester. I suppose those are intended to represent some sort of current capability at a specified voltage drop (short circuit???). But there is no way that the clip on leads shown could carry even 1/10 of that current for any significant time. The tester may be applying a very brief high current pulse which will not overheat the wires, but the lead resistance and clip to terminal resistance should make that measurement very unreliable. Or else it is applying a small current (say 10A), measuring the voltage drop, and extrapolating it to higher current.
Note also that knowing that the battery can deliver power in the form of some very high current for a short period of time is not necessarily an indication that it has the capacity to deliver energy in the form of watt-hours, over a longer period of time.
In short, despite what the person who tested your batteries said, they may only be able to deliver some small fraction of their original rated energy before dropping the voltage to an unusable level.

And the SOC level shown is almost certainly just an estimate based on the open circuit voltage. Not to be taken seriously.

[SunEagle]

I did ask before about NorthStar Red. There are some resellers of used NS red. Ignorant PV users beleive that the SoH of these dumped batteries is 100% cause they show them pictures like this.

Can anyone explain me how is it possible that such kind of measuring tool can show a SoH of 100%?

Depending on the type of instrument some of the quality battery testers can measure the voltage of the battery under load. Just for clarity that 100% is the SOH not the SOC.

[GeorgeF]

I did ask before about NorthStar Red. There are some resellers of used NS red. Ignorant PV users beleive that the SoH of these dumped batteries is 100% cause they show them pictures like this.

Can anyone explain me how is it possible that such kind of measuring tool can show a SoH of 100%?

[inetdog]

So one out of the 8 batteries has been revived. Charging and discharging perfectly without large voltage drops under load. Was hoping for a slightly better result but overall I'm very happy that I tried this out.

Once you have defeated the pressure relief valves, the battery will no longer be able to recombine the hydrogen and oxygen gas produced by electrolysis during normal charging. That means that you will soon have to add water again instead of having a sealed, maintenance-free battery. The volume of electrolyte compared to capacity is far smaller than in an equivalent FLA cell.

[davethedrummer]

So one out of the 8 batteries has been revived. Charging and discharging perfectly without large voltage drops under load. Was hoping for a slightly better result but overall I'm very happy that I tried this out.