Good catch. Corrected...
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If your car could travel 400 miles on a tank we could say it has a range of 400 mile hours. So at 50 miles per hour you could drive for 8 hours.
And theoretically at 400 miles per hour you could drive for 1 hour. Practically though, you probably can't drive that fast, and if you tried, your fuel would run out before 1 hour had elapsed.
Also, if you drove a little slower than 50 mph you may find the fuel lasted for slightly longer than expected.
This also happens with batteries, and one major cause is described using the same word... "resistance". In one case its electrical resistance, the other wind resistance.
And theoretically at 400 miles per hour you could drive for 1 hour. Practically though, you probably can't drive that fast, and if you tried, your fuel would run out before 1 hour had elapsed.
Also, if you drove a little slower than 50 mph you may find the fuel lasted for slightly longer than expected.
This also happens with batteries, and one major cause is described using the same word... "resistance". In one case its electrical resistance, the other wind resistance.
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Thanks, I had no idea modern batteries had those limitations! So, in your opinion, dinosaur lead/acid (with all their shortcomings) still afford the most durable longest lasting, affordable solution for solar energy storage bank? 24 volt optimal? Thanks....Yup!
Although it may not be the best idea unless you are somewhat familiar with it... I'll give you some details and you can see if you want to try, or go for something else...
Lithium Ion and Lithium Polymer are sensitive chemistries that don't like excess heat, and are very sensitive to over-charge and over-discharge... There are also well defined limits to the peak and constant draw of current from these batteries.
So, extra care MUST be taken to charge and use Lithium rechargeable batteries compared to NiCd, NiMh and Lead-Acid.
So, other than the Lithium part, lets talk about battery banks in general.
In parallel, their capacity is added together. (Both their current supply, and mAh rating...)
In parallel, you typically have a lower voltage, but a higher current. All of the cells in a parallel pack are self-balancing.
In series, their voltage is added together, but their current supply is not.
In series, you typically have a higher voltage, but a lower current. The cells do *not* self-balance, so there is a risk with under-charging or over-charging a single battery in a pack, even if the pack is not 'empty' or 'full' ... For a series type pack, it's a good idea to use more forgiving batteries, or you will find that the pack as a whole will degrade quickly and require that one or more cells need to be replaced. You can build a circuit to keep them balanced, but that's extra work
The more cells you have in series, the more likely this problem is to occur with repeated charge/discharge cycles.
It's not all bad, it's just the lithium based ones that tend to be more touchy than most. ALL batteries suffer from this kind of behaviour though. If you are looking for larger scale solar storage, I would certainly suggest Lead-Acid simply based on the cost of the cells and the availability of information to charge/take care of them, and existing hardware you can buy/build.
Don't get me wrong, Lithium is GREAT when it comes to energy density and it's output capabilities, they are simply a tad harder to work with. Many of the lithium cells actually have a built-in protection circuit to prevent over-discharge, over-charge, and over-current conditions that are so harmful. Not all though, so be careful!
I would also strongly recommend against using used cells to make a battery pack unless you are more familiar with their charge characteristics. The cells in a laptop battery pack most likely do not have individual protection circuits, so you need to build something yourself. Additionally, maxing any chemistry battery used/new cells makes things kind of tricky with larger packs. You may find that unless you take very special consideration, some cells in series may die sooner than others... you can't balance this when you are discharging the pack... so a couple bad seeds can cripple the total capacity of your pack because you should stop using the pack once any of the cells deplete. This is not as much of a problem with cells in parallel though, but most packs will usually involve a mix of both series and parallel batteries depending on the voltage/current requirements.
Alsmith has a good idea here for you as well... Take a look at existing systems. Pricing, or at the very least, how they work. In particular, grab (or research) the battery chargers for hobby RC vehicles. They commonly use Li-Po and Li-Poly and include a balancing circuit to keep all the cells in a pack charged properly
