I was hoping Lee would chime in. :-)
See my anti-rant replies below:
On Mar 1, 2021, at 10:41 AM, Lee Hart <leeahart@...> wrote:
Michael Diehr wrote:
Lead acids do vent nasty stuff - hydrogen gas (explosive) and sulfuric acid vapor (toxic, corrosive). Ventilation is required.
Have you considered upgrading to a Lithium battery? They are much more expensive in initial purchase, and can't be charged at temperatures below freezing, but on pretty much every other metric they are vastly superior to lead acid batteries and will probably outlive the van. One Lithium battery will outperform two lead acids, and they don't require any ventilation, etc.
Time for my battery rant. :-)
In the best-case scenario, lithiums can be pretty good. But frankly, that's true for lead-acids as well.
Energy storage:
Lithiums have about twice the energy storage per pound as lead-acids. But they occupy about the same physical space for the same energy storage. So a 12v 100ah battery is about the same size, whether lithium or lead-acid... the lead-acid just weighs more.
Disagree.
Lithiums are advertised and rated on their true capacity (e.g. a 100AH lithium battery delivers an honest 100AH, at a 1C rate).
Lead Acids are rated on some voodoo number (typically a 1/20th C rate of very low current) *and* every time you discharge a lead acid battery below 50% (or allow it to sit below 100% charge) you are killing it.
Safety:
Lithium batteries BURN! The failure modes in lithium batteries can easily start a fire; and it's the type of fire that can be very difficult to extinguish. Keep in mind; you are going to use the battery until it fails. And one of a lithium's failure modes is a fire!
There are multiple Lithium battery chemistries, and this burning issue is really not a problem with LFP (Lithium Ferrous Phosphate chemistry, aka "LiFePo" or sometimes "Iron Phosphate").
LFP batteries are some of the safest around and (in my opinion) safer than Lead Acids by far.
Example: LFPs all come with BMS (battery management systems) which will cut off the charge (or discharge) current if the battery SOC (state of charge) is too high or low. Lead acid batteries do not, and will overcharge (venting hydrogen and sulfuric acid) or undercharge (causing self damage).
Lead-acids don't burn. They might leak acid or vent hydrogen; but they won't start a fire except in the most extreme scenarios.
They can explode. Hydrogen gas is no joke.
If you're worried about venting or hydrogen, use a sealed AGM type lead-acid.
True, AGM are better, but I believe these can also vent when seriously abused (e.g. if you have a malfunctioning charger)
Life:
The main problem is that people buy mostly on price. Consumer-grade lead-acids *and* lithiums are only likely to last 3-6 years (no matter what the ads claim).
Agree, that paying bottom dollar is not wise, for any technology.
Think about the batteries in your laptop or phone; they are lithium, and most of them get weak and fail within 3-6 years.
Again, different kind of "lithium" - laptop batteries are "Lithium Ion" not LFP.
Lithium Ion batteries are used because they are energy dense (great for lightweight laptops) not because they are safe. They aren't very safe.
LFP are different - not as energy dense, but much much safer. Also, they have some of the best longevity around. One major brand has a 3000-5000 cycle estimated life - and at that point, they say the battery still has 75% capacity! They could be lying, of course, but the sorts of stats are not unheard of for LFP batteries.
If you want a lead-acid battery to last, don't buy a 12v starting, marine, or RV battery. They are short-life batteries. Buy a pair of 6v golf cart batteries, or an industrial EV battery, or one for big commercial UPS backup power supplies. These can last 10 years or more.
I managed to go through 3 sets of 6V golf cart batteries in 10 years, and I'm not a dummy when it comes to this stuff. Keeping Lead Acids happy is not easy.
I have Deka gels and Enersys AGM batteries that are over 20 years old and still have more than half their original capacity.
If you want a lithium to last, forget the mass-market "lead-acid replacements" and Chinese ebay specials. Get a used electric vehicle battery -- the EPA *requires* the manufacturers to warranty them for 10 years, so the quality is far better.
This was true a few years ago, but LFP drop-in 12V batteries are quite good now.
Abuse:
Most batteries don't die of old age -- they are *murdered* by negligence and abuse. Bad chargers are everywhere (the Magnetek in the EV is a good "bad" example). Running any battery dead is like giving it a heart attack. Even if it survives, it's been damaged.
True, but note: this *only* applies to lead acid batteries.
Marketing: It's said that there are liars, damned liars, and battery salesman. Most people's understanding of batteries is so poor that they fall victim to every kind of puffery and exaggeration. They don't test a battery; they just blindly believe what the salesman and old wive's tales say.
It's currently fashionable to claim that a lithium battery is "equivalent" to a lead-acid. This is mostly a marketing lie. If you're starting an ICE, all you need is a few seconds of high current. That amounts to less than 1 amphour. Lithiums tend to be better for this type of high-current pulse. So a tiny cheap low-capacity lithium can start an car engine... once.
Not true - LFP batteries are *not* rated for use as starting batteries. They can deliver 100A to 200A easily, but that's not enough for a starting battery. Use LFP for house, and lead acid for starting battery.
Car batteries have far higher amphour capacities -- not just to start the engine; but also to maintain power for long periods of time. Modern cars have dozens of always-on loads (clocks, radio presets, keyless entry, security systems, electronic odometers, etc). Our Eurovans have even more (CO detectors, etc.) So the batteries are sized to be able to handle all these "vampire" loads for weeks on end, in case the vehicle is not driven.
Lead-acids are *good* at providing small amounts of power for a long time -- you get *more* than the rated amphour capacity when discharged this way. A lead-acid "equvalent" battery can't power these loads.
This is true, but misleading. If I leave my Eurovan Camper off shore power, the LFP battery will discharge and stop powering the house electronics. True. But when I come back to it and plug it in, the LFP battery will charge quickly back up to 100% and be 100% healthy. Do this with your lead acid house battery and you've damaged it quite severely.
"There are few industries with more BS than the battery industry." -- Elon Musk
Did you know model 3s are now being built with LFP batteries? Almost like he knows his stuff ;-)
"The storage battery is one of those peculiar things which appeals to the imagination, and no more perfect thing could be desired by stock swindlers. Just as soon as a man gets working on the secondary battery, it brings out his latent capacity for lying." -- Thomas A. Edison
Grumpy old Lee Hart
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Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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