Now that we have the option to install true non-sulfating Partial State of Charge (PSOC) AGM batteries like the Firefly and the Blue Plus range from Meridian/Northstar, we are faced with a new dilemma. These batteries could be at risk of failure due to voltage imbalances when connected as multiple units in a series configuration.
Read the specs of any lithium ion battery and you will see that the individual series-connected cells employ some sort of voltage balancing mechanism. Without this balancing act, some cells would end up working at different voltages and be charged at different rates, and if this situation gets too far out of whack with lithium ion batteries, well .... you know he rest.
Cells in AGM batteries work in a different way to lithium ion cells. Small imbalances between the individual 2v lead-acid cells (six of them in a 12 v battery) do not create any real inherent danger, but stringing together numbers of unbalanced 12v batteries in a series connection to raise the voltage does present the real possibility of premature battery death. The same potential exists also with 6 volt batteries connected in series, but the imbalances should in theory be much smaller, so for simplicity we'll consider only 12 volt batteries here.
How’s everyone been out there? Hopefully, all are well and still kicking and screaming. I’m still lying low and pretty much operating under the radar, but I’ve been badgered lately to get fingers tapping on the keyboard again.
With winter approaching, and with the thought of storms and power outages energizing my little gray cells, I got to wondering just how long I could power up some essentials in the house using my Chevy Volt sitting in the driveway as a power plant.
Oh yes, it’s totally possible, there are tales from those who have done so on the internet, and there are even kits available.
My Volt has a 17 kW-hr, 300v traction battery along with its DC generator plus a 12v battery for all the other normal loads. This 12v battery is charged by a DC-DC converter between the two batteries, so if I were to hook up an inverter to this battery I could supply 110v AC mains power to my household essentials during a power cut, or maybe power up an outdoor event, or fire up a blender and mini-fridge at a beach romp.
Possible? Yes, but for how long?
Challenge your Limits
Are you ready to consider Lithium-Iron-Phosphate batteries (LiFePO4) for your boat or RV? Do you want to make a long-term smart investment for cruising enjoyment, giving you one less thing to worry about – dead batteries or not enough battery power for your DC load, i.e. power hungry equipment on board like a microwave, air conditioning, or electric engine?
In Defense of Lithium Ion Batteries
Yes, it's true; thermal runaway can and does happen in Valve Regulated Lead Acid (VLRA) Absorbed Glass Mat (AGM) batteries, and is not a new phenomenon afflicting Lithium Ion batteries alone. A Google search of "Thermal Runaway in AGM Batteries" will reveal enough technical papers on the subject to keep even the most techno-savvy occupied for a long while, and will save me trying to explain the why's and wherefore's here. The simple fact is that, given the right conditions, an AGM battery can, and will, start a self-perpetuating internal heating process (thermal runaway) that can end in catastrophic failure with the possibility of fire and explosion. So why is there so much negative publicity and bad karma surrounding Lithium Ion batteries, when AGM's are prone to much the same maladies?
Early pioneers of marine lithium battery systems used individual cells in a rectangular format, and some still do. These types of cells are referred to as “prismatic”, which by definition means having the form of a prism, which is hardly a representative description unless you imagine two prisms joined together to make a rectangle. A more accurate description would be: “a right rectangular prism”, as opposed to a “wrong” or a “left” rectangular prism, one supposes. But I digress …
Prepare for those inconvenient power outages, or for the trending living-off-the-grid
We sell a fabulous battery – Firefly’s 2v/4v model, which has all the advantages of their popular Group 31, but in a different format. Here's where I intend to use them in a future project.
With the increasing frequency of heavy storms and threats of power outages, I’ve been reviewing the emergency battery back-up system I have set up in my basement. This currently consists of 8x 185 amp/hr AGM batteries with an Inverter-Charger, plus a mains/generator Transfer Switch with generator plug-in access. There is also a Transfer Box that has six mains/inverter transfer switches with associated breakers and balancing meters which supply six circuits: the fridge, kitchen outlets, sump pump, basement outlets, front room outlets, and the oil-fired furnace.
I saw some communications in a trade journal the other day discussing the common practice of wiring batteries in parallel to increase capacity. Specifically, one writer was warning of the possibility of a cell shorting in one of the batteries, resulting in the other batteries all discharging at a high rate of current into the short circuited cell leading to an apocalyptic event below decks. Is he/she correct? Well, yes and no.
Yes, this is very much a possibility, but is dependent on battery type. An old timer, like yours truly, will probably adhere to the notion that the likelihood of a shorted cell is real, but that’s because our heads are still stuck in “the good old days”, and we are not being practical.
Let’s think about this. How can a cell, one of six in a 12 volt lead acid battery, become short circuited?
OK, that’s not something you’ll hear every day, but it is very much a possibility, where thermal runaway can destroy Valve Regulated Lead Acid (VLRA) batteries like AGM’s (Absorbed Glass Mat). A Google search of “Thermal Runaway in AGM Batteries” will reveal enough technical papers on the subject to keep even the most techno-savvy occupied for a long while and will save me trying to explain the why’s and wherefore’s here.
The simple fact is that, given the right conditions, an AGM battery can, and will, start a self-perpetuating internal heating process (thermal runaway) which can end in catastrophic failure along with the possibility of fire and explosion, or at the very least leave you with a very sad-looking molten battery case.
We’re still on the electrical trail this week, but I promise I’ll have some more entertaining stuff for you soon. Mind you, electricity can get quite entertaining if you don’t do things correctly, just ask this guy!
A conundrum cropped up while helping customers plan the change-over from lead-acid batteries to a RELiON lithium battery bank, and we’ll get to that soon. But first let’s review current practices for charging multiple battery banks.
We are proud to offer RELiON Lithium Iron Phosphate batteries, dedicated to high performance energy solutions for serious yacht and RV owners. They are available in standard industry sizes. Custom sizes available upon request.
These batteries are Safe, Powerful, Versatile, and Practical. Watch our video below and then Go Here to learn more.
We spend considerable time and effort trying to help boat operators understand how to look after their batteries, but we still hear of way too many premature deaths. So in an effort to get the message across from a different angle, we offer the following advice on how to inflict serious harm and punishment on expensive batteries without really trying.
Simply put, there are three main types of abuse you can employ to kill or maim your batteries:
- Excessive heat
- Physical damage (including vibration), and
- Poor charging routines
The first two I hope to be self explanatory, but the third requires some detailed explanation.
Flooded lead acid batteries, including AGM's, don't like being left for extended periods in a partially charged state. Doing so allows some of the lead sulfate crystals that form naturally on the negative plate during the discharge process to harden to the point where they can't then be dissolved the next time the battery is charged. This is known as sulfation which leads to an increasing loss of useable capacity as more and more crystals harden.
It’s a simple and common task for anyone owning or operating a vehicle with a gas tank. You pull up to the pump, stick the nozzle in the filler, pull the trigger, and then wait for either the auto-stop mechanism to operate, or you get a boot-full of gas. The math is simple: Since the last time you filled up you have used x gallons of gas, and now you add exactly x gallons to the tank to bring it back up to the level it was previously. There are no losses other than the boot-full you might have got thanks to the faulty nozzle.
Refilling batteries is a very different kettle of fish.
We received an inquiry recently from a customer who is contemplating installing a large 12v (volt) AGM (Absorbed Glass Mat) battery bank, and he asked a pertinent question: Which would be better; several 12v batteries wired in parallel to multiply capacity, or large capacity 2v, 4v, or 6v cell groups wired in series to produce a high capacity 12v bank? Good question.
This customer estimates he needs around an 800 A/hr (Amp/hours at the 20 hour rate) 12v battery bank to achieve the holy grail of running his air conditioning overnight from batteries through an inverter in addition to supplying the regular daily house loads. This is a popular dream of boat owners these days, and highly achievable with the equipment we have available, and there are several battery configurations to consider. Typically it will all come down to what will fit where, so first let’s look at space constraints and then focus on the technicalities. Cost will not be considered in this article as you can’t put a price on creature comforts, now can you?
Continuing on the theme of the previous blog, regarding wiring individual batteries in parallel to make a higher capacity bank, now we can look at the best way to wire them up.
I included a teaser graphic in that last blog that showed two batteries wired in parallel and with the two main cables, one positive and one negative, both connected to one battery. I expected a flurry of comments on this, but to my surprise received only one. Mr. D said that the configuration shown would result in uneven current draw from each battery, resulting in greatly reduced cycle-life of the first battery in line. Is that so?
And if so, what is the best configuration? What are the alternatives?
Yipee! Time to put on the testing hat once again.
If you haven’t heard on the grape-vine by now, or seen it on our web site, Coastal Climate Control is very pleased to announce that it’s now offering Lithium Iron Phosphate (LiFePO4) batteries from RELiON. These are great products from a great company, and Coastal is stocking the most popular sizes, ready for immediate sale.
Many of you will no doubt be aware of the enormous advantages of LiFePO4 batteries, and there is a whole bunch of information regarding RELiON batteries on our web site here.
We’ve been asked how to charge a lithium battery bank when the boat has been set up for Flooded, GEL, or AGM lead-acid batteries, so let’s look at some of the characteristics of LiFePO4 batteries.
So Elon Musk has parked his Tesla in the Milky Way or wherever. Just imagine having the capability and resources to do that, and the mind boggles at the thought of what else you could dispose of up there in the big blue yonder. I presume that he removed the battery before take-off, because those things are heavy.
Yes, I know they are Lithium Ion (LI) batteries, but those are not as light as some imagine. I know this from when I drive my Chevy Volt to my office in Tesla Drive (a bit ironic don’t you think) and feel how solid and sure-footed it is on the highway. That’s because it weighs about 800 pounds more than a similarly sized Chevy Cruze due to the hefty battery pack. But thanks to that 17kw lump, I have sizzling, silent acceleration and decent range in a very stable platform.
Talk is that there’s soon to be an Electric GT motor racing series featuring a modified Tesla. This will no doubt have phenomenal out-of-the-box performance, but weighs in at about 200 pounds more than my road-going Volt, and where less weight = more speed (i.e. on the race track) that means a lot of lithium to be grappling with lurching around the bendy bits.
I started tinkering with LI batteries six years ago, and even made my own 100 amp/hr pack from bits and bobs I bought online. I did it primarily to investigate whether that might be a viable alternative to the few expensive and complex marine LI systems available back then, but soon realized that the safety aspect was paramount.
Those specialized marine LI systems featured external Battery Management Systems (BMS) that could cut loads and/or charging devices if anything got slightly out of whack, and when you’re in the middle of an ocean that’s a pretty important feature. Most of the online offerings I came across were for auto use, where it’s assumed that if something goes wrong you can pull over to side of the road, hop out, and run away. Not so good for a yacht where the closest land may be a just mile away, but happens to be straight down, on the ocean floor.
What does a mousetrap and winterizing your boat have in common?
That’s what I’m working on right now. Well, not exactly a better mousetrap, but one with additional functionality. The mousetraps I’m using now are extremely well designed and work so much better than the old spring-and-fling models, but like all mousetraps that I’m aware of, they require checking periodically for “yield”.
So what I’m working on is some form of remote indication of when a trap is sprung. That should be easy, right?