Assume an 8AH (amp hour) battery.

A full charge (or discharge) is 8A in 1 hour, or 16A in 1/2 hour, and so forth.

The cars can charge at something like 100A (I don't recall the exact number, so let's use that.) 8AH = 8A*60m = 100A*8*60m/100 => 8*60/100 ~= 5m

They can charge at that rate because there are very big electrical cables involved, active cooling of the battery, and active monitoring of the battery.

The chargers you are more familiar with use a much lower current so that the batteries being charged do not heat up and so that they will last longer. Also some of the chargers are "dumb" and just put in a low enough current that they can be left on for a very long time, so that careful monitoring of the battery and cooling are not needed. A NIMH battery can be overcharged at C/20 amps (C is the capacity) for a very long time without damaging it because there is a catalyst in it which reforms the hydrogen generated back into water. Overcharge it with more current than that and the catalyst cannot keep up and the battery will burst. See for instance:

https://www.powerstream.com/NiMH.htm

 

Thanks for the reply... Will look into your link in detail.

 

Just cleaning up a few points specific to the HCH2.

• 5.5Ah total, 2.2Ah usable capacity (HCH2 patch uses less capacity).
• HCH2 and most IMA vehicles charge at 50A max. I have witnessed HDS report 60A charging momentarily when an HCH2 battery is low.
• Electrical cables are actually pretty small - 6-8awg.
• NiMH can can handle that kind of current because they're inherently low resistance when designed to be.
• They can also handle such high current because they are being used in the range of about 40-80% of their capacity where they are nearly 100% efficient.
• High charge/discharge currents are brief. The average current in or out over a typical combined driving trip is about 15-20A.

The real reason your battery fills and drains so quickly is because it's severely deteriorated and has lost much of its usable capacity. So instead of 5.5Ah of total capacity, it has likely closer to 2.3-3.0Ah. This means you may have as little as 1Ah of usable capacity.

 

 

Cost. A comparable capacitor bank with about 1.2Ah of capacity currently runs about $5000. That doesn't include the case, interface, electronics, etc... just the "cells".

And technology. What was available in 2005 was less capable and even more expensive.

 

 

Somehow I missed the part about a "long incline" - that will tap out even a new battery. If you can reduce the working range of the battery as you described, that's how you maximize the life of the battery. Hauling a$$ up a hill until the battery is empty, and then charging it back up to full is a great way to minimize its life.

The less the battery gauge moves, the better.
The more time it stays in the 5-7 bar range, the better.

BTW... the hybrid battery contains:

158V * 5.5Ah = .869kWh of which 0.348kWh is usable
The 151R 12V battery under the hood has 12V * 24Ah = 0.288kWh

So, the USABLE electrical energy in the hybrid battery is only about 18% more than the total electrical energy in the 12V battery under the hood. Hopefully, that helps lend perspective on things...

Concerning the grid charger, consult with your battery supplier.

 

It may be that even going slowly up and down that hill is bad. There is a roughly 110m difference in elevation between my home and my work, and in normal city speed driving that is enough to discharge a full battery at least half way, while in the other direction the battery is fully charged. Even a brand new battery does that - it seems to be a function of the control logic, which is too dumb to compensate for known grades. Those are not full discharge/recharge cycles, but are a pretty big swing. So 300 or so of those a year and in 3 years that's about 1000 cycles (there is other driving) and that is about as long as my IMA batteries seem to last.

But there are other variables, like the hot weather where I live, so other things could be determining battery life. In any case, it is an anecdotal observation, I don't have an identical second car driving the same length route at the same temperatures, always on level ground, for a control!



Which brings up the question - why didn't they just use lead acid batteries instead?
This table suggests a few things:


http://batteryuniversity.com/learn/a...e_best_battery


1. the cycle life is half as long for the lead acid battery, so they would have to be replaced twice
as often. On the flip side, a 12V car battery is only around $100 dollars, currently 20X less than an IMA battery.
(Car batteries are only good for around 3 years here too, by the way. Definitely the heat in that case.)



2. Lead acid batteries actually have a lower internal resistance, so that would have been a plus. But when charging rapidly they are very difficult to cool Conversely, one can blow air around the smaller NiMH batteries to draw off the heat.


3. Peak current is higher for NiMH. To provide as much for Lead Acid batteries they would have to be in parallel.


4. Easier to do the power electronics with higher voltages, so 120 NiMH cells in series. Stepping up and down from 4(?) parallel 12V batteries might have been very lossy.


Today though, one could get a pretty big capacitor to help things out. So say two batteries for power storage and the capacitor for dumping/storing current rapidly. Others are working on lower voltage, milder hybrids along these lines, see:


https://www.nytimes.com/2018/02/08/b...-48-volts.html