Lead and LIthium

There are a lot of people, "experts", some might claim, who argue endlessly about the virtues of lead acid batteries, lithium batteries, and everything in between. Ultimately their arguments always come down to cost. I care about what works more than cost and so my arguments are a little different. I care about more bang for my buck and the quality of craftsmanship. I can't afford to keep spending money on something that shouldn't break or wear out after only a week of use. My projects always seem to be broken often enough without crucial parts aiding their state of being broken. I digress, this is supposed to be about batteries. This may be a "growing post", one that I add to as I think of things that I've forgotten.

Lead Acid is the most common battery type. It's over 150 years old. There is a lot of information, misinformation, and myths concerning them. Some of which is still viable, and some not. Here are a few things about lead acid that you should know;
1. LA batteries are heavy.
2. LA Can be lethal. Unsealed LA spew toxic fumes and must not be used in areas where you want to stay alive. I know of people who have used them in houses. My parents had one hooked up to a CB radio when I was a kid. Our house was drafty and the battery (which leaked I might add) was near a window. That didn't keep the gases from building up at times. It's a bad idea, don't do it.
3. There are Sealed Lead Acid batteries. SLA batteries can be used in living quarters. These are the only ones that I recommend for robots if you have to use lead. SLA batteries are not as heavy because they are starved. That means they don't have extra electrolyte adding weight and they won't leak if you crack the case.
4. LA batteries are cheap. If you pick one up and find it to be kind of light, it's really cheap. That is because modern LA batteries use a lead foil or mesh instead of plates. It makes them cheaper to make and ship, but it also makes them last only a few years as opposed to a few decades. Of all of the lead acid batteries I have bought over the years, I only have 2 left and only one is more than 4 years old. Most only last a year or two.
5. LA may have it's shortcomings, but unlike Lithium, LA batteries can be charged while they are being used. That's why ROB uses a LA for his locomotion power.
6. LA batteries make great ballast weights. Instead of using lead weights, or bricks for ballast, use SLA batteries. The space will be comprised of something useful, and you can always use more space to store power.
7.LA batteries should never be rapid charged as it can warp the lead structures and cause the battery to die. So they should be charged slow and steady.

Myth #1 Don't put lead acid on a concrete floor; This is one that used to actually be true. Originally lead acid battery cells were made from glass jars. In cold climates, if you put glass jars on concrete floors and the ground freezes, the jars break. I'm talking about really frozen ground, not just a little cold.

Myth #2 Lead Acid batteries are the only true battery; False. It is a battery only in the sense that it is a battery of cells. These cells are "Super Capacitors". They cannot produce a charge. They merely store it, then release it in a controlled manner.

Lithium Batteries are not all equal and you need to know a lot more about them before you even try to use them. They were invented in the 1950's (I think), but it wasn't until the 1990's that they became viable. Actually, I seem to remember a version of the lithium battery being at least attempted around 1890. If you want to pick nits, some alkaline batteries have had some lithium in them since about that time. The problem is that most of the chemistries suffer from "thermal runaway". They literally melt down. With some of the chemistries that can be lethal, because some of these power houses contain cobalt and some other nasty ingredients. I recommend only using true lithium Iron Phosphate (LiFe), yes there are some fakes out there. True LiFe batteries contain no toxic metals and cannot combust. I prefer Lithium batteries, but they have some shortcomings. All of my information will concern the LiFe chemistry, because it is the safest and a good compromise between "goods" and "bads".

1. Li batteries are light.
2. Li seem to be expensive, but they really aren't. Under good conditions you can  harvest several more amps a day with Li when compared to LA, and they last many years longer than LA.
3. You MUST use a BMS (battery management system) with Li. Otherwise you will ruin the battery. Actually, I've never understood why BMS boards aren't used with lead, as well. The life of the battery would be greatly increased, and recharge rates would be improved, because the discharge wouldn't be so great.
4. Li batteries "generate" power. This is confusing to most people. LA batteries only "store" a charge, but Li generate power. This is because for the Li battery to work, lithium moves from one pole to the other. When you "recharge" a lithium battery, you aren't renewing the charge as you would with LA, you are running the battery backwards very quickly to get the lithium back  to the negative pole.
5. Li cannot recharge and discharge at the same time. This is because of what I just stated. The lithium cannot move both directions at once. If you try to make it do so, you run the risk of frying the battery. Instead, we use "power paths" to give the appearance of recharging while discharging. I don't understand why doing this works, I just know from experience that it does.

I know this is a lot of boring information, but it's stuff you need to know if you are to understand anything about digital robotics.