Battery Pack Marketing Teams Confound Us with Capacity Claims…..But they’re just doing their jobs.

A letter from Jaguar Wearable Technologies Founders

Dear Reader,

Sales teams commonly conflate “sets of numbers” with product value. Higher mileage numbers are good. Fewer calories is good. A higher price tag on a restaurant menu must mean it’s tastier. We all know sales teams can be loose with the truth.

Battery pack pitch teams are no different than those selling cars or diet food. They use a confounding assortment of numbers, inserted among long strings of mysterious words to convince us the product they’re pitching is preferable to a competitive product. If you’ve been shopping for a battery pack you’ve likely seen lots of numbers associated with terms like volts, amps, milliampere hours, watt hours, etc. Some numbers you recognize because you’ve put them to use. You understand that devices you operate require a certain number of volts / amps, but many other numbers, however, are difficult to relate to practical experiences.

This brief letter intends to provide you with some practical battery pack capacity information, which we hope you can put to good use so you make the best decision “for you.”

Recharging time is just as important as pack capacity

You likely know the range your car / truck will travel via a single tank of fuel. It’s important because the range reflects the cost of traveling a specific distance. It’s important because you may be concerned about the availability of fuel along a long stretch of isolated road. What’s less important is the amount of time you will spend pumping fuel into your vehicle; because pumps refill your tank in a small handful of minutes. Only if there is a shortage of refueling stations and fuel pumps could “refueling time” become an issue.

Unlike refilling your car’s gas tank, the practical use of rechargeable batteries has a lot to do with recharge times.

Some of us who use combustion engine cars may consider owning an electric car, dependent upon rechargeable battery technology, if we lived very predictable lives that accommodated multiple hours of recharge time. If we typically traveled distances daily (to and from home) less than the range supported by a single “charge,” and we could always fully recharge our car’s batteries over night, electric vehicles might have some cool perks we would enjoy.

Once drained, most high capacity (so-called) portable battery packs require between 8 - 24 hours to fully recharge, via a typical home’s power outlet, thus leashing the pack to that outlet for 8 to 24 hours.

If you must own a typical plug-in, rechargeable battery pack, we advise that you (1) do your best to predict how many “contiguous hours you are willing to forfeit your pack’s availability,” in order to completely recharge your pack after each usage period; and then (2) purchase only the amount of pack capacity that you can fully recharge within that number of hours. For example, if you can commit to plugging in your pack each night for 8 hours, purchase a pack that can be fully recharged in 8 hours. If you need more (drainage) capacity, buy additional packs instead of purchasing a higher capacity pack. If you drain 2 packs, you can charge each pack for 8 hours via their own outlet.

Do you sense a “pattern” here? If you cannot predict the availability of recharging resources, or you cannot predict how long you can forfeit a pack’s availability (to recharge it), a single plug-in rechargeable battery pack is not a practical power source, no matter what’s its capacity.

Redundancy is often more valuable than pack capacity

Batteries degrade as they are drained and recharged. Individual batteries, even those of the same model, made by the same company, degrade at different rates. Most packs contain groups of batteries (referred to a “series”), which are wired and or spot welded together, and thus, interdependent. Just a single degraded battery in a series can degrade the other batteries ability to drain and to recharge. Over time, pack capacity degrades.

Here is a simple example (just for comparison) of how things can go wrong when charging groups (series) of batteries. Imagine you have a row of 6 identical bath tubs side by side. You install big cylinders, horizontally, connecting tub 1 to tub 2, tub 3 to 4, 4 to 5 and 5 to 6. The cylinders (connecting the tubs) are at the same height from the floor. You fill up tub 1 and when tub 1’s water level reaches the cylinder, water flows into tub 2. When the water level in tub 2 reaches the cylinder connecting it to tub 3, tub 3 fills up to the same level as tubs 1 and 2. Eventually, all the tubs end up with the same water level. Now, empty the tubs and drill a big hole in side wall of tub 3 (bigger than the the internal diameter of the cylinders) below the height of the cylinder connecting tub 3 to tub 4. Refill the tubs, via tub 1. As a result of the hole in tub 3; tubs 4, 5 and 6 never refill.

To mask this problem, pack makers install multiple groups of batteries (which run in parallel) and try keep the groups’ charges in balance, but masking the problem doesn’t halt degradation, that’s why most reputable battery and battery pack makers publish the estimated number of recharge cycles their battery or pack can endure, prior to 20% its (capacity) degradation (under ideal conditions).

Masking the problem becomes more and more complex as a greater quantity of battery groups are managed by a pack’s battery management system.

The Jaguar team believes their truth in the saying: “don’t put all your eggs in one basket” however, we believe that the solution is to NOT interconnect more and more batteries in a single pack. If you need capacity and must own a “plug-in” pack, you’re are better off owning and operating multiple packs.

If you’re open to learning about SlingIt, our team’s solution to the “plug-in pack” dilemma, please read-on.

18650 battery and SlingIt capacity

Standard size 18650, 8 and 10 amp, rechargeable batteries typically advertise capacities between 2500 and 3500 milliamp hours (mAh). You load six of the same 18650 batteries into a SlingIt to generate 12 volts and up to 10 amps of power. When the system can’t deliver 12 volts via the power provided by the batteries, SlingIt shuts down the power to its 12 volt socket. When the power shuts down, swap out the drained batteries with charged batteries. Insert the drained batteries into smart chargers (of the same make and model) and they will tell you if any of the individual batteries are degraded. Replace any number of degraded batteries with good batteries. The degradation problems are resolved, not masked.

Why are we willing to let you quickly replace drained batteries with charged batteries rather then taking the pack off line to accommodate hours of (pack plug-in pack) recharging? Why do we enable you to detect and replace degraded batteries? Because, it’s not our job to sell batteries, whether or not those batteries are packed into packs. It’s not our job to sell you multiple packs, to overcome recharge times and degraded batteries.

We consider it our job to enable you to build a battery and smart charger inventory which best meets your needs.

We consider it our job to ensure you have safe access to power almost any where and almost any time.

During our SlingIt application tests:

Six 3500 mAh batteries energized a WOW 2160 lumen LED work light for over 3 hours.

Six 3500 mAh batteries recharged a lower capacity internal mobile phone battery 7x (from 0% to 100%).

Six 3500 mAh batteries energized 1 of the water pumps we intend to deploy in our CleanIt water filtration system for over 5 hours.

Not bad for less than 12 ounces of battery weight.