high rate charging on generator

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".