high rate charging on generator

[pianotuna]

Hi all,

The batteries:

556 amp-hours of surplus acid AGM batteries 12 volt jars 105 lbs each. They are wired as two banks with balanced wiring.

The depth of discharge:

12.1 volts under 425 watts of load plus normal RV overhead applied for 4 hours. During the day the fridge (325 watts) was run for 5 hours and the RV was driven at highway speeds for 3 hours. On the last hour of driving charging was initially 50 amps but that soon tapered to 25 amps. The solar contribution was about 5 amps.

The generator:

Yamaha Sieb 2800 Va (23 amps of output @120 volts AC)

The inverter/charger:

Magnum 3000 hybrid.

What happened:

I deliberately took the battery bank down farther than I normally would. I turned on the generator after setting the Magnum to draw no more than 23 amps.

Within one minute the Magnum remote reported "fet over load". Remote was showing 127 amps of charging at 12.9 volts DC just before the over load shut down.

I reset the Magnum by removing all power sources. I "dialed down" the possible input to 15 amps from 23. This still caused the Magnum to display 125 amps of charging. I finally dialed it down to just 13 amps to prevent over load on the fets. At that level charging was 90 amps @ 12.5 volts.

I've been charging for 45 minutes at 90 (+) amps and the voltage had risen to 13.8.

I 'opened up' the input to 23 amps and after 15 minutes it is now charging at 14.3 @ 98 amps. The remote is saying absorb charging.

15 minutes later and the remote says 14.3 at 80 amps.

1.5 hours and charging is 14.4 @ 27 amps.

During this time frame I did also run the microwave and three oil filled heaters (400 watts each).

The generator was running with the eco switch on and at the 45 minute point started throttling back as the load shifted.

Next time my voltage is so low I'll dial the Magnum down to 13 amps to start out.

[pianotuna]

Hi Mex,

Thanks for the voltage under load tip. That will be a useful "go, no go" limit.

I've run a second cord (#12) for power for space heating now so I won't be using the load support feature so much. I'd still love to give a piece of my mind to the nutter who chose a 1591 watt draw microwave for the RV.

My OEM cord is #10 cold weather and a bit over 100 feet so I'm seeing a no load voltage of 112. That is until meal time when every house on the block turns on their stoves at once. The blasted microwave causes the voltage to drop to 105. I truly wish the Magnum load support worked as voltage support. Maybe this years RV budget will stretch to an autoformer.

[MEXICOWANDERER]

Don you are doing an involuntary load test. Monitor voltage and temperature. An IR scan of a couple of random terminals. Do not continue if temperature of the terminal ascends to 45 c. with a (guesstimate) ambient temp of 10c.

Again, lead acid batteries provide plenty of hints if they are suffering under the lash and are on the verge of rebellion. The first is common sense discharge amperage limit. if you are REALLY curious, perform a standardized BCI CCA test with a variable carbon pile load tester. Single battery. If any time during the actual discharge cycle (not the test) voltage slumps to 11.0 volts, cease the discharging. Peukert factors in (or not) at all levels of discharge. Your posted values are not outrageous.

Again this is working with a lead acid battery not fulminate of mercury.

[pianotuna]

Hi Imurphy,

Thanks for your answer but I guess I did not ask the right question.

I wanted to know what was the upper limit for demand on the bank of four (total 556 amp-hours). Am I damaging it by asking it to provide 208 amps for say six minutes?

Imurphy wrote:
Discharge. Everything in telcom is designed around a min 8 hour cycle life(load supporting). BUT, it is all to common for equipment growth to over run plant growth. Many systems have gone from 8hr min battery plants to battery plants to provide "carry through service". Basically last just long enough for the generators to come online.

[MEXICOWANDERER]

Yep there I went thinking of the brand-new to the industry Telecomm batteries of 25-years ago. To update my rain further I would need to know the positive plate thickness and how much -more-calcium has been added to the negative plate. Surely they did not get stupid and add calcium to the positive plate paste? 0 percent remaining at an 8 rate and 7 -year functional lifespan calls for some fancy footwork. The first being acid surplus capacity mats.

How many cells in a typical installation? Down here TelMex torres microondas have 12.5 KV feeder lines which mean they -can- have a substantial charger. Sadly towers, some intallations have a 10 minute reserve. Enough time to call the power company. Carlos Slim the owner of TelMex did not get to be the third wealthiest man on earth from poor Mexico by offering world-class performance. "Me? Pay for batteries? Har har har"

[Imurphy]

MEXICOWANDERER wrote:
The "forever and a day" now needs elaboration.
A C20 rate is plenty to meet OEM specs about minimum initial charge protocol. With fuel costing what is does I whack AGM with a C10 as long as cell temps do not increase at a rate of 1c hr or more. At 1c I back off. One thing everyone has to remind themselves of now and again. Is that rates and capacities are designed for the basic hands off user. If someone has the ability and/or attention span to actually pay attention, you can get away with a lot more than they will ever put on paper.

The "forever" means gaining that last 5%. The bitter .5% goal is frustrating to the point of causing neurosis with generator recharging. The less frequent the batteries recharge min C20, the more infrequent full recharge is achieved to half percent of total capacity the more frequent Conditioning must br performed and if the option means burning diesel and knowing lots of expensive parts are rubbing in the process, personally I'd rather endure a root canal.

Six hours. 6-lousy hours connected to public power is magic after an AGM sees a recycle. Six lousy rotten hours that a dedicated off-grid bank will never see.

This is exactly and precisely where and when a modest solar array can become it's weight in gold. An array engineered to provide a winter solstice quantity of amp hours equal to this missing quotient amp hours caused by a battery that refuses to accept economical charging energy from burning petroleum. A 7 Kw genset loafing at 200-watts is tough to endure especially when a person is mesmerized by an exhaust plume.

Either size the solar array to have 110% amp hour capacity of worst case winter solstice production or size the array to provide the last five percent or whatever factor is missing from generator charging. Hitting an accumulator hard is less damaging than slow starvation (within limits). The batteries must recharge or they are going to suffer. It is up to the owner as to how they wish to configure this task. Anyone can agree trying to 100%SOC off diesel is pointless. You "could" do it, but it would require multiple stages of AC power supply to be anywhere near efficient. Even running a Honda 2000 pushing a 20 amp automotive charger is a waste of fuel. This is where Solar can really shine. If you are able to bulk off a generator and let the solar do the rest you will be a winner almost every day.

My philosophy on battery management is simple. The lowest cost per a given amount of kWh rendered. Sounds easy but it's a worthy challenge. An outage is not an outage. A Telecomm battery cannot fail without dire consequences. Fail means deliver performance not necessarily self-destruct or die of old age. An off grid bank can be rigged to provide a work around. This skews the design philosophy to the point where one cannot compare to the other. Telecomm failures cause heads to roll. So over compensation must over rule initial and operational cost. Unforgiving.

Private banks are under intense scrutiny economics wise from inception. A heartbreaking majority are under intense pressure far beyond their capability (and reality). Little if any genuine attempts to match loads with realistic scenarios for recharging. An array is coupled to a bank then to a load. By error and trial shortcomings are discovered then "fixes" are cobbled according to budget and whim. Get your dander down people! I'm talking about the market in general and not the members of this forum.

We need an example so allow me to play the Rhesus monkey. I needed a battery to perform a specific duty. It had to be AGM due to it powering a BiPap and emergency lighting in hotel rooms on the road yaddah. Power outages down here are a curse. Narrows the choices. A fast recharging durable 100 amp hour battery. Lifeline met the criteria. But experience taught me recharging via public power had to be fast. So I opted for an 80-amp charger. The load, the storage and the replenishment all met specs in all respects.
My bank at home is a 3300 amp hour 12-cell flooded system. But an aggregate total of 400 +385+120+100 amperes charging via a 12.5 Kw genset allows me total latitude in powered recharging. Solar is not an option. Run and maintenance costs is the weak link. But the magic is I have full access to 60 amp 254 vac for enough hours to vastly simplify my life.

That is the key. Does a system have access to public power and for how many hours a week? Total off-grid is challenging. Total off grid in conjuntion with trying to utlilize insufficient solar voltaic kWh is simply not resolvable unless adequate alternative charging is made available.

A GRAND WELCOME TO THE FORUM from Mex is in order. And enveloped plates are not far off for telecomm batteries. You have a job worthy of calling challenging. The issues here are capacity, money, performance, money, maintenance, money, metering, money, lifespan, money, and last but not least, money.

I play a hard role that is for sure. During the day I have to see things in black and white teletype'd name plate ratings. While at home, we get to do just about what ever we want. But there are a few things I do bring over from the telco world. Voltage loss restrictions on wiring and other wiring standards(efficiency and safety). As well as understanding the difference between a name plate rating and what a product will actually do. But when ever possible I try and engineer mixed grid and off grid systems as robust as I can based on budget. And many times using those very telco standards gets you there.

One thing that is always in the back of my head when it comes to capacity and ratings. Under promise, over deliver.

I never want to put out a system that does not meet its design spec, or barely meets the spec. I want a system built tough enough and based on numbers conservative enough that meeting the standards is the minimum performance. And that in 3-5-7-10 years that system is still meeting the standards.

It is especially hard for off grid up here in AK. In the summer we have nearing endless hours of sun. And can see 18 hrs of "noon quality" light in a single day. This makes systems easy. But on the flip of that coin is the winter, when we may only get 45 minutes of noon quality sun a day. And sometimes not even that. I have designed and installed off grid systems for several customers living in full 2500 sqft homes with all the joys of a normal home. Having a system that leaves them dead in the water is not an option. Could it have been done cheaper, hell yes. But it would not have been "right". My personal systems are much less "complete" as I have no one to let down, no one to get cold in the night. Just me to be mad at myself. but I like to tinker, so having several systems that work but require constant toying with keeps me sane.

I will help anyone put together a system. But you have two options.

1. cheap. but I will tell you upfront and in no uncertain terms that what you will get will require maintenance. and may not perform to spec for more than a year or two.

2. Will fulfill all of your needs plus reasonable performance and life margins.

When given the two options, most people come around to the economics of a system that is overbuilt. After all these days no one seems to remember the term "duty cycle".

[Imurphy]

pianotuna wrote:
Hi Imurphy,

Welcome to RVnet!

By hit it hard, do you mean discharge rate? Or charging rate?

What would you suggest for the 139 amp-hour 12 volt battery for a maximum (safe) discharge rate?

Imurphy wrote:
Where in telcom we generally hit it hard, and there for don't get as many cycles out of them.

Discharge. Everything in telcom is designed around a min 8 hour cycle life(load supporting). BUT, it is all to common for equipment growth to over run plant growth. Many systems have gone from 8hr min battery plants to battery plants to provide "carry through service". Basically last just long enough for the generators to come online. I know of many places that have 16,000+/- AH's of battery. But if the generator does not come online within 15 minutes things are going down. Usually due to space for batteries they start to shift focus not to battery backup but minimizing power loss all together. So they just buy a generator or two. And as long as that generator will run for more then 8 hrs with its fuel supply it makes the FCC happy. NEW E911 requirements have jumped this rating for many facilities to 24hrs as of Oct 15th of this year. That has caused a bit of a scramble for abilities pulling 302,000+/- watts, as there just is not anywhere left to put batteries. And the cost of huge Lithium plants is still largely out of reach for backup purposes.

[JiminDenver]

JiminDenver
Are you sure you could live with the other differences? AGM is heavy and the CCA ratio is something like 2/3rds. If one has the space and the springs, no sweat.

Mex

Four of the Telecom batts that were new, 149 Ah and $125 would have been 75 Ah lower and weighed 50 pounds less than the three Lifeline 8-Ds. We have a 3000 lb CCC so it's not a big deal and the batteries go over the axles.

Our system isn't intended to cycle the bank much daily. Overnight it is so shallow the remote display doesn't show it and the rest of the day the solar covers nearly all the loads directly. What the system can handle is a week or more of cloudy, cool weather when we start snow birding. I'll take the Champ on a extended trip but the system gets a chance to show its stuff first.

I have the panel, controllers, etc to create a system here at the house, just need the bank. The thing is it would take quite a while to recoup the $500 for the bank.

[MEXICOWANDERER]

The "forever and a day" now needs elaboration.
A C20 rate is plenty to meet OEM specs about minimum initial charge protocol. With fuel costing what is does I whack AGM with a C10 as long as cell temps do not increase at a rate of 1c hr or more. At 1c I back off.

The "forever" means gaining that last 5%. The bitter .5% goal is frustrating to the point of causing neurosis with generator recharging. The less frequent the batteries recharge min C20, the more infrequent full recharge is achieved to half percent of total capacity the more frequent Conditioning must br performed and if the option means burning diesel and knowing lots of expensive parts are rubbing in the process, personally I'd rather endure a root canal.

Six hours. 6-lousy hours connected to public power is magic after an AGM sees a recycle. Six lousy rotten hours that a dedicated off-grid bank will never see.

This is exactly and precisely where and when a modest solar array can become it's weight in gold. An array engineered to provide a winter solstice quantity of amp hours equal to this missing quotient amp hours caused by a battery that refuses to accept economical charging energy from burning petroleum. A 7 Kw genset loafing at 200-watts is tough to endure especially when a person is mesmerized by an exhaust plume.

Either size the solar array to have 110% amp hour capacity of worst case winter solstice production or size the array to provide the last five percent or whatever factor is missing from generator charging. Hitting an accumulator hard is less damaging than slow starvation (within limits). The batteries must recharge or they are going to suffer. It is up to the owner as to how they wish to configure this task.

My philosophy on battery management is simple. The lowest cost per a given amount of kWh rendered. Sounds easy but it's a worthy challenge. An outage is not an outage. A Telecomm battery cannot fail without dire consequences. Fail means deliver performance not necessarily self-destruct or die of old age. An off grid bank can be rigged to provide a work around. This skews the design philosophy to the point where one cannot compare to the other. Telecomm failures cause heads to roll. So over compensation must over rule initial and operational cost. Unforgiving.

Private banks are under intense scrutiny economics wise from inception. A heartbreaking majority are under intense pressure far beyond their capability (and reality). Little if any genuine attempts to match loads with realistic scenarios for recharging. An array is coupled to a bank then to a load. By error and trial shortcomings are discovered then "fixes" are cobbled according to budget and whim. Get your dander down people! I'm talking about the market in general and not the members of this forum.

We need an example so allow me to play the Rhesus monkey. I needed a battery to perform a specific duty. It had to be AGM due to it powering a BiPap and emergency lighting in hotel rooms on the road yaddah. Power outages down here are a curse. Narrows the choices. A fast recharging durable 100 amp hour battery. Lifeline met the criteria. But experience taught me recharging via public power had to be fast. So I opted for an 80-amp charger. The load, the storage and the replenishment all met specs in all respects.
My bank at home is a 3300 amp hour 12-cell flooded system. But an aggregate total of 400 +385+120+100 amperes charging via a 12.5 Kw genset allows me total latitude in powered recharging. Solar is not an option. Run and maintenance costs is the weak link. But the magic is I have full access to 60 amp 254 vac for enough hours to vastly simplify my life.

That is the key. Does a system have access to public power and for how many hours a week? Total off-grid is challenging. Total off grid in conjuntion with trying to utlilize insufficient solar voltaic kWh is simply not resolvable unless adequate alternative charging is made available.

A GRAND WELCOME TO THE FORUM from Mex is in order. And enveloped plates are not far off for telecomm batteries. You have a job worthy of calling challenging. The issues here are capacity, money, performance, money, maintenance, money, metering, money, lifespan, money, and last but not least, money.

[NinerBikes]

pianotuna wrote:
Hi Imurphy,

Welcome to RVnet!

By hit it hard, do you mean discharge rate? Or charging rate?

What would you suggest for the 139 amp-hour 12 volt battery for a maximum (safe) discharge rate?

Imurphy wrote:
Where in telcom we generally hit it hard, and there for don't get as many cycles out of them.

I'd suggest no more than a C/10 to C/7 discharge rate, and a C/5 recharge is hitting it hard, as is using 14.8V to recharge in bulk mode. 14.4V seems to do it all on my DEKA model, consistently. Case doesn't get warm, when recharging.

[pianotuna]

Hi Imurphy,

Welcome to RVnet!

By hit it hard, do you mean discharge rate? Or charging rate?

What would you suggest for the 139 amp-hour 12 volt battery for a maximum (safe) discharge rate?

Imurphy wrote:
Where in telcom we generally hit it hard, and there for don't get as many cycles out of them.

[NinerBikes]

Imurphy wrote:

MEXICOWANDERER wrote:
Telecomm companies establish parameters for maintenance based on OEM guidelines. OEM is aware that their client wishes the very highest degree of performance reliability. So a operating lifetime max hours is agreed upon. Max hours of guaranteed reliability. Zero non performers. The batteries have a specified level of max discharge at which Telecomm shuts down transmission and the batteries go dormant. The percentage of charge remaining is unknown to me. We allow many plants to go as dead as they want. And rely on equipment's power supplies to shut down or brown out. Thou some sites we do terminate service for the sake of the batteries.

Technicians operate by holy writ in the form of rote. They follow maintenance, troubleshooting and testing exactly and precisely according to company doctrine. It is all well documented then entered into a computer database for reference, study and analysis. Job one is the repeater must not fail. The largest piece of this information is trending. With out an accurate history of how the battery lives, one may declare it deceased early. Or worse off, wait to long to bury it.

Transcribing telecomm writ to a usable form for RVers can be deceptive. What worked excellently for telecomm may not be in the best interest of somone whose use of the used batteries may be totally different. Telecomm is after 100.0% reliabilty at the expense of trade-offs. Are you aware of the tradeoffs?Most telcom plants trade cycle's for depth or discharge. As with any battery the less you use it, the longer you can use it. Where in telcom we generally hit it hard, and there for dont get as many cycles out of them.

Understand this point. After an outage, telecomm batteries have forever and a day to recharge. Do you? Charge amperage ceilings are based on acheiving ultra maximum longevity. This is a moot point if telecomm batteries spend a majority of their golden years connected to shore power with incidental short interruptions for boondocking. In that scenario following Telecomm rote is the wisest choice as it most closely mimics what the batteries were designed for.Every battery mfg. has recommendations on how to use their battery. No one says you have to. But pumping to much current into a plant is a sure way to ruin it. And Telcom has restrictions on recharge. We do NOT have forever and a day to recover a plant. We have FCC regulations that state our systems have to maintain between 8 and 24hrs of backup at any given time. We recharge our plants as fast as we can. Its not uncommon to have an outage just hours after a previous one. This is the worse case. We also have to have the equipment to properly supply power to the load, and be able to charge the batteries ASAP. Even a back up generator or a fire alarm panel has regulations on max recharge time.

When things shift to off-grid rote gets chucked out the window. Calculated charge maximum absorbsion voltage is not the same animal. Neither is maximum absorbsion voltage. Only float voltage remains thec same.Many battery MFG. understand the different use of their batteries. In the case of these UPS12-490's they call for a float of 13.65 ± 0.15 VDC average per 12V unit. While recognizing they may be used in a cycle service thus also state 14.40 to 14.80 VDC average per 12V unit for such use. Upping the voltage while still maintaining the recommended amperage increases the wattage of absorbed power.

If you stick like glue to telecomm rote prepare to rum your generator a lot longer. You are mimicking unlimited time value recharging via your generator. Your fuel and your time.

When I generator recharge 3300 amp hours of 24 volt battery it is absolutely different from charging using CFE shore power. One is 500+ amperes. The other is 120 amperes (the 4024 Trace). Coursing 120'amperes through a 1650 amp hour battery / 2 banks is a gentle recharge. Life with public power available is absolutely unlike recharging via a generator. The issue is time. The issue is money. Lots and lots of money. To do an in-frame on the Kubota is around five thousand dollars. Add that to $3.35 fuel, filyets, lube oil and labor and it makes shore power recharging calculations totally, completely and absolutely irrelevant. To the point of becoming absurd. Cost of kWh hr transcribed to usable battery kWh includes the ACTUAL cost of fuel plus generator wear and tear. I an not a telecomm company and nothing I manage even remotely can serve as a model for both economics nor management.

Trust me not much we do is a model of economics either. In many cases with remote prime power sites. We would rather buy a new generator ever 2-3 years and burn thousands of gallons of fuel. Than have to purchase a new battery plant every fuel years. Its it alot cheaper to fuel and replace a generator than replace a battery plant.

One of the things I love about Telco batteries is they are always available. They take a 48v string and toss it out. We get to run to the pile and pick out the best of whats left to make out 12 or 24v systems. I know I have a huge pile of batteries at home that were tossed aside. I currently have 8 180ah AGM batteries I am "reviving" from the telco world. they were taken out of service and left on a pallet for 2 years with out a charge. I have been able to bring them back to life quite well. And they currently follow their historical trending withing 80% of rated capacity. These cells were deemed to have a 7yr life span. They spent 9 years in service. 2 on a pallet and are about to be connected to an outback GS series radian, where I expect another hand full of years out of them in UPS mode.

The biggest problem with most telco batteries is the amount of calcium they have. during discharge the plates swell. Over time this causes plates to short and the battery than no longer works.

I would not hesitate to use old telco batteries. But I certainly would not buy them new for this use. For the money there are batteries that will serve the offgrid world better. But for cheap/free batteries, why not finish them off.

When you get two guys from different ends of the battery business, and telecom business, in the same post, you should find a moderator that can make this a sticky for Telecom batteries. I think you can take this post above to the bank.

I will be stunned if I don't get 7 years or more out of my Deka Telecom battery, knowing how I care and use it, thick plates and acid rich concentrate at 1.300 SG.

[Imurphy]

MEXICOWANDERER wrote:
Telecomm companies establish parameters for maintenance based on OEM guidelines. OEM is aware that their client wishes the very highest degree of performance reliability. So a operating lifetime max hours is agreed upon. Max hours of guaranteed reliability. Zero non performers. The batteries have a specified level of max discharge at which Telecomm shuts down transmission and the batteries go dormant. The percentage of charge remaining is unknown to me. We allow many plants to go as dead as they want. And rely on equipment's power supplies to shut down or brown out. Thou some sites we do terminate service for the sake of the batteries.

Technicians operate by holy writ in the form of rote. They follow maintenance, troubleshooting and testing exactly and precisely according to company doctrine. It is all well documented then entered into a computer database for reference, study and analysis. Job one is the repeater must not fail. The largest piece of this information is trending. With out an accurate history of how the battery lives, one may declare it deceased early. Or worse off, wait to long to bury it.

Transcribing telecomm writ to a usable form for RVers can be deceptive. What worked excellently for telecomm may not be in the best interest of somone whose use of the used batteries may be totally different. Telecomm is after 100.0% reliabilty at the expense of trade-offs. Are you aware of the tradeoffs?Most telcom plants trade cycle's for depth or discharge. As with any battery the less you use it, the longer you can use it. Where in telcom we generally hit it hard, and there for dont get as many cycles out of them.

Understand this point. After an outage, telecomm batteries have forever and a day to recharge. Do you? Charge amperage ceilings are based on acheiving ultra maximum longevity. This is a moot point if telecomm batteries spend a majority of their golden years connected to shore power with incidental short interruptions for boondocking. In that scenario following Telecomm rote is the wisest choice as it most closely mimics what the batteries were designed for.Every battery mfg. has recommendations on how to use their battery. No one says you have to. But pumping to much current into a plant is a sure way to ruin it. And Telcom has restrictions on recharge. We do NOT have forever and a day to recover a plant. We have FCC regulations that state our systems have to maintain between 8 and 24hrs of backup at any given time. We recharge our plants as fast as we can. Its not uncommon to have an outage just hours after a previous one. This is the worse case. We also have to have the equipment to properly supply power to the load, and be able to charge the batteries ASAP. Even a back up generator or a fire alarm panel has regulations on max recharge time.

When things shift to off-grid rote gets chucked out the window. Calculated charge maximum absorbsion voltage is not the same animal. Neither is maximum absorbsion voltage. Only float voltage remains thec same.Many battery MFG. understand the different use of their batteries. In the case of these UPS12-490's they call for a float of 13.65 ± 0.15 VDC average per 12V unit. While recognizing they may be used in a cycle service thus also state 14.40 to 14.80 VDC average per 12V unit for such use. Upping the voltage while still maintaining the recommended amperage increases the wattage of absorbed power.

If you stick like glue to telecomm rote prepare to rum your generator a lot longer. You are mimicking unlimited time value recharging via your generator. Your fuel and your time.

When I generator recharge 3300 amp hours of 24 volt battery it is absolutely different from charging using CFE shore power. One is 500+ amperes. The other is 120 amperes (the 4024 Trace). Coursing 120'amperes through a 1650 amp hour battery / 2 banks is a gentle recharge. Life with public power available is absolutely unlike recharging via a generator. The issue is time. The issue is money. Lots and lots of money. To do an in-frame on the Kubota is around five thousand dollars. Add that to $3.35 fuel, filyets, lube oil and labor and it makes shore power recharging calculations totally, completely and absolutely irrelevant. To the point of becoming absurd. Cost of kWh hr transcribed to usable battery kWh includes the ACTUAL cost of fuel plus generator wear and tear. I an not a telecomm company and nothing I manage even remotely can serve as a model for both economics nor management.

Trust me not much we do is a model of economics either. In many cases with remote prime power sites. We would rather buy a new generator ever 2-3 years and burn thousands of gallons of fuel. Than have to purchase a new battery plant every fuel years. Its it alot cheaper to fuel and replace a generator than replace a battery plant.

One of the things I love about Telco batteries is they are always available. They take a 48v string and toss it out. We get to run to the pile and pick out the best of whats left to make out 12 or 24v systems. I know I have a huge pile of batteries at home that were tossed aside. I currently have 8 180ah AGM batteries I am "reviving" from the telco world. they were taken out of service and left on a pallet for 2 years with out a charge. I have been able to bring them back to life quite well. And they currently follow their historical trending withing 80% of rated capacity. These cells were deemed to have a 7yr life span. They spent 9 years in service. 2 on a pallet and are about to be connected to an outback GS series radian, where I expect another hand full of years out of them in UPS mode.

The biggest problem with most telco batteries is the amount of calcium they have. during discharge the plates swell. Over time this causes plates to short and the battery than no longer works.

I would not hesitate to use old telco batteries. But I certainly would not buy them new for this use. For the money there are batteries that will serve the offgrid world better. But for cheap/free batteries, why not finish them off.

[MEXICOWANDERER]

JiminDenver
Are you sure you could live with the other differences? AGM is heavy and the CCA ratio is something like 2/3rds. If one has the space and the springs, no sweat.

Let's suppose a given AGM is supposed to last 5-years treated correctly. Let's suppose out of those 5-years a total of three months SPREAD EVENLY over the 5-years the batteries were charged to 95%. How much lifespan would be sacrificed? I suspect less than one month.

AGM batteries can "handle" 14.7 volts charge limit from 95-98% capacity just fine. They are a battery not fulminate of mercury.

When an individual DEVOTES an AGM to dedicated low value solar charging, penalties are invoked. Some of them are unpleasant. Loss of capacity recovery is a royal pain-in-the-ass, review the Lifeline manual PDF and groan. Avoiding the use of a generator without benefit of having a very large solar array, just isn't worth it. Take this advice from someone who got their rear scorched learning the hard way...

Too late in life for me to learn exactly why but AGM hates with a passion to start from cycle low point with less than a 20% of amp hour recharge rate. I can guess the following scenario: Discharge AGM to 50% capacity. Turn off all loads then recharge at 5% amp hour capacity all day every day until charge amperage droops to point five percent amperage rating one half amp per 100 amp hours. Battery will lose 40% of it's lifespan, perhaps 25% of it's lifespan when pain-in-the-ass recovery is used. It just isn't worth it. If a 100 amp hours worth of AGM is not recharged at 20% prepare for the consequences. As in every electrochemical action, time and amplitude enters rudely stage left. A fifteen percent recharge rate is not nearly as destructive as a five percent recharge rate. Having the charge cease during no sunlight just makes things worse (if that's possible). The answer is to achieve a minimum amperage into the battery recharge of 20% AND leave the battery at 95% SOC when it's margarita time. Hitting 100% SOC is hard to do, but the top missing 5% is not Armageddon. The 5% should be made up similar to what top charging does for a flooded battery (See! The batteries have something in common).

I wish things were different, but I have to play by "their" rules, as well.

I wish John Marles (Megawatt) could come up with a large charger that could be tweaked to 14.4 volts.

[JiminDenver]

I think that they would be like 6 volt jars in that if you did want to run the larger loads, you will need to spread it out with more batteries. Having a larger bank is so nice when you do fire up the MW or coffee pot. I was so use to seeing the last bank take a dive that even with the solar assist that it was hard to believe when I ran the MW for 12 mins and barely dropped into the 12's.

So possibly the 600 Ah bank would have served me as well as the 675 Ah Lifelines. Loads are spread out or covered by the solar. The solar itself isn't enough to cook them and the cycling over night is very low. All that remains to be seen is how they would handle a week of cloudy weather and reduced solar output. Mex says they can take forever to recharge, does that mean they wont be damaged by not getting back up to full for a extended time?

I can't wait for LiPo's to become affordable. We will be having a good ol time then. 😉