How Can I Use A Low C-Price Battery To Cost A Excessive C-Price Battery?

Join each day information updates from CleanTechnica on electronic mail. Or observe us on Google Information!

Is the C fee of a pack adjustable relying on the design of the cell connections inside a pack? No.

Now you should surprise, how can this be?

I can describe C fee this manner. You probably have a 1A hr cell, and it may possibly discharge all of its cost in half an hour, it has a C fee of two. You probably have one other 1A hr cell, and it has a C fee of 0.5, it could be discharged in 2 hrs. C fee is at all times in reference to time, often hours. C fee is simply the utmost fee a cell can discharge. Its a attribute of a selected cell chemistry, and it doesn’t change for a given cell, until that cell modifications.

Simply as an apart. We’re going to use models of amp hours, abbreviated A hr. This can be a most popular technique of describing batteries and its used an incredible deal. Right here is an easy instance: Let’s select a 1A hr cell with a C of 1.

There are the ideas of parallel and collection in electrical engineering. For voltage sources in collection, the voltage provides, and the present is similar. For voltage sources in parallel, the voltage stays the identical, and the present turns into the sum of the currents. You will discover this in fundamental electrical engineering texts.

What occurs if we put 4 cells in collection? We nonetheless have 1A, however now we have 4x the voltage. What’s the C fee? One. It will probably solely discharge in 1 hour.

What if we put all 4 cells in parallel? We then have a 4A hr grouping, however solely 1x the voltage. What’s the C fee? One. It, too, can solely discharge its full output in 1 hour. All 4 of the cells can solely discharge in a single 1 hour.

You see this? C fee is simply a measure of the speed a cell might be totally discharged. It’s actually about time and nothing else, so it’s unbiased of V and A.

In our examples, we differ A and V, however the outcome nonetheless has the identical product, VxA, or energy score.

This is likely one of the fascinating issues about C fee. You are able to do no matter you need with the cells — parallel, collection, and as many occasions and with any type of capability. The C fee is at all times the identical because the C fee of the cell.

How do I get a low C-rate battery to cost a excessive C-rate battery?

You don’t actually get a unique C fee if you clump extra cells collectively, however you are able to do one thing else about it.

An even bigger pack with a decrease C fee can ship the identical fee of cost as a smaller pack with the next C fee this manner.

Say we have to ship 100 kWh in 40 minutes. We’ve two sorts of chemistries. Chemistry A has a C fee of 1.5, and Chemistry B has a C fee of 0.33. With Chemistry A, we will use a 100 kWh pack to ship 100 kWh in 40 minutes, as a result of with a C fee of 1.5, which means it may possibly ship its full cost in 1/1.5 hr = 0.666 or ⅔ of an hour, precisely 40 minutes.

How will we do it with Chemistry B? With Chemistry B, we will solely ship the total pack cost in 3 hours, slightly than 2/3 hour. We will use a bigger capability pack in kWh to ship the cost. What measurement pack do we’d like? Properly, we wish to ship the cost in ⅔ of an hour and the pack discharges full on the fee of three hours. The ratio between them is 3/(2/3) or 9/2, 4.5. This implies a 450 kWh pack is required.

Let’s examine the maths.

450 kWh/3 hrs is 150 kWh/hr. Its can be 100 kWh/0.66 hr or 100 kWh/(2/3)hr.

A battery pack with decrease C fee have to be made bigger in energy or VxA to be able to match the charging fee, or C fee, of a better C-rate battery pack. The voltage have to be the identical, however the present has to extend. It is going to be a much bigger battery pack or extra cells in parallel. It requires extra cells.