high rate charging on generator

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.

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.

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.

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"

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".

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
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.

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.

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.

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.