AGM Batteries

[Not Sure]

Originally Posted by billyehh

The caveat is that AGM's are not forgiving to non smart chargers, regulators or controllers. But if they are taken care of they will last as long as a Surrette or Rolls. Mine are almost 9 years old and passed a load test withflying colours last year.

And I've got 2 old used automobile batteries that every 2 weeks or so I drain down to near dead, then charge them back up using a 45watt 72v (that's 72 volts) solar panel, and I've been doing that for almost 3 years now, and the batteries are still taking a charge above 12.55v.

All that that proves, however, is that there are exceptions to every rule. It certainly doesn't mean that automobile batteries are suitable for deep cycling and high voltage charging, nor that they will last for years when treated in such a manner.

[billyehh]

You and your 2 old batteries are the perfect example of what I have been saying. Anyone who is hard on batteries should stick with the cheapest flooded batteries which can be replaced when you destroy them. Charging batteries at 72 volts and surviving means you have an minor miracle. Congratulations.

By the way Peukerts effect is part of physics the last time I checked and is the reason AGM's can take a higher charge.

Again for all those interested in a well thought out article on batteries I still recommend How Lead Acid Batteries Work

With a little search you can find many sites discussing the different merits of thevarious battery chemistries

[Not Sure]

Originally Posted by billyehh

You and your 2 old batteries are the perfect example of what I have been saying. Anyone who is hard on batteries should stick with the cheapest flooded batteries which can be replaced when you destroy them. Charging batteries at 72 volts and surviving means you have an minor miracle. Congratulations.

By the way Peukerts effect is part of physics the last time I checked and is the reason AGM's can take a higher charge.

Again for all those interested in a well thought out article on batteries I still recommend How Lead Acid Batteries Work

With a little search you can find many sites discussing the different merits of thevarious battery chemistries

Actually the exact opposite is true. If you're prone to be hard on, or ignore batteries, then AGM's and gel cells are made for you, as you're easily able to run down to Walmart or Sears and grab another after you've ignored them and/or abused them for several years.

Batteries such as the Trojan 105's, however, are for those who take care of and monitor their batteries, fill them up with distilled water as needed, and otherwise try and cycle them not more than 50% down. It is ludicrous to claim that people who buy Sear's Diehard AGM Marine batteries (and the like) so that they don't have to monitor and take care of the battery, know more about what is the better battery and the proper way to take care of it then the off-grid energy users whose lives literally depend on keeping their regular wet-cell deep cycle batteries (such as the Trojan 105 'beginner'* batteries) well cared for.

*'beginner' - Trojan 105's are referred to as 'beginner' deep cycle in the off-grid power industry because they are used to teach battery owners how to properly care for expensive deep cycle batteries used in off-grid alternative power installations. They (T-105's) are robust and inexpensive, and there is not the monetary loss involved when new alternative power system owners neglect to properly care for them and/or deep-discharge them below 50%, which reduces the life of deep-discharge batteries and is costly if you're doing it to $800+ industrial quality deep cycle batteries as a 'learning' experience.

[Not Sure]

Originally Posted by billyehh

Charging batteries at 72 volts and surviving means you have an minor miracle. Congratulations.

Uh, no. No 'miracle' necessary. The current, while 72 volts, is very low amps, and doesn't appear to put much stress on the batteries at all. I've left batteries charging on the 72v charger all day (8+ hours in full sun), with nary a hint of boiling over of the fluid, ever. The fact is, you can hold the 72volts in your hand and at peak output it only produces a mild burning sensation similar to touching your tongue to a 9v cell (which I assume everyone has done as a kid).

Do the math. 45 watts, 72volts. I'll let you figure the amps.


By the way, I've also taken completely dead used automotive batteries that have been sitting for several years dead, hooked them up to the 72v solar charger, and was able to bring them back to life in about 16 hours charging time.....again, approaching 12.5v as their new 'full' charge (measured after resting following charging, of course). Put that one in your pipe and smoke it. (It kinda goes against the grain of everything you've ever been led to believe about batteries, huh.)

If you want to make your own 72v solar battery charger/equalizer, I'll tell you what mine is made of. (Of course, I assume no responsibility if you blow something up, burn down something, or otherwise harm life or property, as this is for informational purposes only.)
Find an old Unisolar 45watt 72v direct-to-grid solar panel and wire up a jumper cable (with 1 set of ends left on for battery 'clamps') to the output leads of the solar panel. I clamp the jumper cable ends to either end of a 1"x12" block of wood when they are not being used, and make sure that they don't come in contact with anything while 'open circuit' (which can go as high as 90v or so).

[hellosailor]

"Um, how can I put this nicely....that is not exactly correct. When you fast charge a battery (higher charging current) you create more gassing and higher temps, which is exactly what you're supposed to avoid with AGM's (and Gels)."
Actually, when AGMs or any other type of lead acid battery are used with pulsed-DC charging, they can and will charge at a higher rate because the pulse charging allows micro intervals where the electrolyte cools enough so it does not buble. Bubbles create high resistance and high heat during a charge, so simply by using a PWM charger (MPPT, PWM-DC, etc.) you can often recharge a lead acid battery 10% faster without overheating it or doing any other damage.

The lab results and actual physics to back all this new stuff up are fairly recent and generally considered TRADE SECRETS and so not publicized in great detail by the folks making both the batteries and the chargers. Including alternators.

Sure, someone with somthing to sell is always suspect, but some of them have outstanding reps and can back their stories up with hard lab results. The information is out there and not hard to dig down to. Hidden pretty neatly by obsolete information and folks elling magic potions, but not really hard to find. Universities, government labs, other reasonably pobjective places all publish agreeing results.

You want to do things the old fashioned way with wet cells, that's your option. They're still the cheapest way to store power, and that's the only reason to still use them.

[Not Sure]

Originally Posted by hellosailor

"Um, how can I put this nicely....that is not exactly correct. When you fast charge a battery (higher charging current) you create more gassing and higher temps, which is exactly what you're supposed to avoid with AGM's (and Gels)."
Actually, when AGMs or any other type of lead acid battery are used with pulsed-DC charging, they can and will charge at a higher rate because the pulse charging allows micro intervals where the electrolyte cools enough so it does not buble. Bubbles create high resistance and high heat during a charge, so simply by using a PWM charger (MPPT, PWM-DC, etc.) you can often recharge a lead acid battery 10% faster without overheating it or doing any other damage.

The lab results and actual physics to back all this new stuff up are fairly recent and generally considered TRADE SECRETS and so not publicized in great detail by the folks making both the batteries and the chargers. Including alternators.

Sure, someone with somthing to sell is always suspect, but some of them have outstanding reps and can back their stories up with hard lab results. The information is out there and not hard to dig down to. Hidden pretty neatly by obsolete information and folks elling magic potions, but not really hard to find. Universities, government labs, other reasonably pobjective places all publish agreeing results.

You want to do things the old fashioned way with wet cells, that's your option. They're still the cheapest way to store power, and that's the only reason to still use them.

I see...it's 'trade secrets' and 'new physics', eh? LOL! Yeah, and 'Extends' (or whatever its called) is scientifically developed to make one's penis larger too, as seen on TV.

[hellosailor]

Not Sure, you've sure been lucky. Every auto battery maker (and that's an "SLI" battery, not an "auto" battery, to use the correct name) says that if you drain it nearly all the way and then recharge it, you might get six to ten full cycles out of it before it turns to junk. They're just not intended for deep cycling, and not one company making them will warranty them in that use.

Of course, it could be something in your "well the numbers don't matter its close enough" philosophy that is giving you misleading results. The difference between "dead" and 60% discharged is significant. As is the difference between 60% charged, and "full".

Apparently you've proved what Einstein said, that all the laws of physics are simply relative, and tend to vary from time to time and place to place.

[Not Sure]

Originally Posted by hellosailor

Not Sure, you've sure been lucky. Every auto battery maker (and that's an "SLI" battery, not an "auto" battery, to use the correct name) says that if you drain it nearly all the way and then recharge it, you might get six to ten full cycles out of it before it turns to junk. They're just not intended for deep cycling, and not one company making them will warranty them in that use.

Of course, it could be something in your "well the numbers don't matter its close enough" philosophy that is giving you misleading results. The difference between "dead" and 60% discharged is significant. As is the difference between 60% charged, and "full".

Apparently you've proved what Einstein said, that all the laws of physics are simply relative, and tend to vary from time to time and place to place.

Actually, I don't believe I've been 'lucky' with those used automotive batteries (which aren't being used in a boat I might add, but rather in other remote 12v applications), particularly since I've got several more -- one an old 8D CAT battery -- that I treat the same way with similar results. I tend to take a more scientific approach. And that is that battery technology has improved to the point that even decent regular wet cell automotive-type batteries are built far better today than they were in the past and can take some repeated abuse, combined with the fact that my high-voltage (72v) solar panel is probably providing enough current to prevent the permanent sulfurization of the lead plates which occur with such deep discharges (and are what prevents the battery from taking a charge), that and the honeycombed lead plates of the automobile batteries are robust enough now that they are not deteriorating rapidly under such treatment, as they commonly did in the past. In other words...science.

[Not Sure]

Actually, I'll provide you the specs on the (amorphous) solar panel for science's sake -- yup, it even tolerates shade. (Solarex Millennia MST-43MV is the panel -- a subsidiary of BP Solar, and no longer in business) It's actually rated at 43watts, not 45w.
voltage at P: 72v
current at P: .6a
open circuit voltage(V): 98v
short circuit current: .8a
design max V: 117v
nominal voltage: 48v
minimum blocking diode: 3a
maximum system voltage: 600v
series fuse rating: 20a

In other words, if you wanted to hook this panel up to a battery bank permanently, it would need to be a 48v battery system with a 48v charge controller rated to take the 72v input. (Of course, you could hook it up permanently to a 12v battery if you ran it through a ceramic resistor that knocked the voltage down to around 12v, but then....what's the use, as you've effectively neutered the panel at that point, and it's low voltage low amperage output would be next to useless.....about 7watts or so)

[goboatingnow]

By the way, I've also taken completely dead used automotive batteries that have been sitting for several years dead, hooked them up to the 72v solar charger, and was able to bring them back to life in about 16 hours charging time.....again, approaching 12.5v as their new 'full' charge (measured after resting following charging, of course). Put that one in your pipe and smoke it. (It kinda goes against the grain of everything you've ever been led to believe about batteries, huh.)

Stuff and nonense, any old battery will accept a recharge and display a terminal voltage, what matters is the amount of energy stored and available. You need ot do discharge tests and I expect the capacity of that battery is a fraction of what it should be. Terminal voltage is completely misleading

[s/v Jedi]

Not Sure: you are obviously clueless about the whole issue and walk over laws of nature like if they would make way for you and your starter batteries. Some facts: you do not charge your 12V battery at 72V, period. You might measure 72V at the solar panel when it is disconnected but not when you connect it to the battery. Your battery pulls it down to the 12V level, which puts the panel at a very low performance point of it's output curve and I estimate the current at 0.5A (20% under panel spec, even at short circuit (0V) you only get 0.8A) at 12V service. So, when your magical system has been charging for an 8-hour day, you have put the fabulous amount of 8 x 0.5 = 4 Ah into the battery. If you call that running it dead down before charging you are right but that is because you never fully charge it or it doesn't take a charge anymore (it is empty all the time). To charge an 80Ah battery from empty you need well over 200 hours of full sun without any power-draw. That battery must be powering a very low-power system. Also, your view of acceptance-rate is seriously flawed. You sound like those people who don't believe man from Earth actually walked on the Moon. You will dismiss any evidence and scientific information while dreaming up your own laws of nature and never give in. ciao! Nick.

[Not Sure]

Originally Posted by s/v Jedi

Not Sure: you are obviously clueless about the whole issue and walk over laws of nature like if they would make way for you and your starter batteries. Some facts: you do not charge your 12V battery at 72V, period. You might measure 72V at the solar panel when it is disconnected but not when you connect it to the battery. Your battery pulls it down to the 12V level, which puts the panel at a very low performance point of it's output curve and I estimate the current at 0.5A (20% under panel spec, even at short circuit (0V) you only get 0.8A) at 12V service. So, when your magical system has been charging for an 8-hour day, you have put the fabulous amount of 8 x 0.5 = 4 Ah into the battery. If you call that running it dead down before charging you are right but that is because you never fully charge it or it doesn't take a charge anymore (it is empty all the time). To charge an 80Ah battery from empty you need well over 200 hours of full sun without any power-draw. That battery must be powering a very low-power system. Also, your view of acceptance-rate is seriously flawed. You sound like those people who don't believe man from Earth actually walked on the Moon. You will dismiss any evidence and scientific information while dreaming up your own laws of nature and never give in. ciao! Nick.

Actually, the panel measures 90v+ when open circuit. Output is 72v, and of course when connected to the battery what you will be measuring is the battery voltage ...which you can literally watch increase every few seconds on a multimeter when the panel is connected. Naturally the old formerly dead batteries aren't taking a full charge, and I already stated that their 'full charge' is around 12.5v or so.

Frankly, I don't give a rat's azz what you choose to believe or not believe. I'm telling you what happens. And for the record, this panel is putting out close to 100% of its rated capacity, which is excellent (and surprising) for a 20 year old amorphous (thin film) solar panel. They're not supposed to do that either, but there it is nevertheless.

Actually, it's quite funny to see the comments range from "You'll blow yourself up!" to "It's not putting out hardly any charge!". Clearly I'm not the one who 'doesn't know what they're talking about', and just as clearly the truth lies somewhere in the middle of the two extremes.

[s/v Jedi]

NotSure,

You agree with what I wrote: the voltage is the battery voltage so 12-14V. The panel can deliver an absolute maximum of 0.8A at short-circuit so the output for charging the battery is at best 14 x 0.8 = 11.2 W. (power equals voltage times current). If you want more power out of the panel you have to connect it to a 48V battery bank, or use a MPPT controller that can take 100V input and create a 12V charger-output from that.

Also, after 8 hours in the sun (one day), you get 6.4Ah into the battery which is nothing really.

You approach of the truth must be between two extremes is a polical one, not a scientific view.

cheers,
Nick.

[Not Sure]

Originally Posted by s/v Jedi

NotSure,

You agree with what I wrote: the voltage is the battery voltage so 12-14V. The panel can deliver an absolute maximum of 0.8A at short-circuit so the output for charging the battery is at best 14 x 0.8 = 11.2 W. (power equals voltage times current). If you want more power out of the panel you have to connect it to a 48V battery bank, or use a MPPT controller that can take 100V input and create a 12V charger-output from that.

Also, after 8 hours in the sun (one day), you get 6.4Ah into the battery which is nothing really.

You approach of the truth must be between two extremes is a polical one, not a scientific view.

cheers,
Nick.

So, is your claim that a 72v 45 watt solar panel directly hooked up to charge a 12v battery puts a similar amount of juice into the 12v battery as a 12v 5 watt solar panel directly hooked up to a 12v battery? Because that is essentially what you are claiming here. Is that your position?

[hellosailor]

You know, Nick, I've been playing around with batteries and circuits for maybe 45 years. Some formal education, some less formal. And the one thing I've found? You can often beat or exceed a spec, in some way, for some time, at some point. But when you're trying to do the fuel load for a 72-hour race and including electrical charging and a budget...funny thing but you'll either go black or silent or both when you try to make those "blue moon" numbers work instead of the ones supplied by the battery makers, charger makers, Sandia Labs, all those nice folks who have acid burns in their white lab coats and can repeat their experiments and conclusions all day every day, all year long.

Somebody wants to put a dying battery into some kind of use and keep it out of the recycling bin for an extra couple of years, great. More power to him. I know when I spec a circuit, I can relay on the performance all the way from one end to the other, and squeeze a bit more out when I really need it.

Listen, there are still some 2000 portable strontium piles missing inthe former USSR. If we go looking now....surely there are a few still up for sale?