Can you run an HCH2 CVT with a dead NiMH battery?
 

:confused:
I want to throw open again the subject of the NiMH battery life on the Civic Hybrid. This battery is an additional part that does not exist on a non-hybrid that is potentially expensive to replace. In Houston where I live, lead-acid batteries often die after only 3 years.
First – How much does it cost…the dealer told me about $2500 when I bought the car, but I have since heard $4000 and I also saw on a post that the price had been reduced, to less than $2000 I think
Secondly – if the battery did fail, could you still drive the car if the battery was dead? I don’t see why not unless the battery would get hot or something. I once accidentally completely discharged both batteries and jump starting via the lead-acid battery was the easiest thing I have ever done, so the motor should keep the lead-acid battery charged up enough to start the car and then the motor would supply all the power needed while driving. Obviously you couldn’t drive a Prius due to its electrical transmission setup but in a Civic the battery serves only as an assist device.
Let’s face it, if the battery died after the 80000 mile warranty was up, it would never make economic sense to spend thousands on a replacement battery unless you absolutely had to.
I ask these questions because my 2007 HCH2 CVT has 32000 miles on it and I was toying with the idea of an extended warranty.
Does anyone have any real facts on this which would help me decide whether it would be worth getting one?

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

1. I'm not sure that anybody really knows. Most failures has been under warranty, the rest seem to be getting "consideration" from AHM so as not to cause bad press.
2. You should be able to, but why would you want to?

You say "if the battery died after the warranty was up, it would never make sense to replace it", but keeping track of all my miles and money, I figure I've saved just under $2000 so far in gas, and that's at 47k miles. So let's say my battery goes to toast at 100k, I'll have saved $4000, spend (for sake of argument) $3000 for a replacement, and still come out $1000 ahead.

Obviously, all numbers rounded. You can check out actual data here

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

It would run until the 12v battery died - there is no alternator or generator on the 1.3L engine - the IMA battery feeds the voltage converter that makes the 12v charge for the battery under the hood and all the other 12v needs.

You have to have the IMA battery to make the 12v for the rest of the car. You would loose your A/C as well as that runs off the IMA battery.
That is why you A/C works in auto when the engine is in auto/stop.

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

It depends on how dead the IMA system is. In some cases the engine battery is charged and you can keep on driving the car. The engine will start via the engine battery and your power will be down because of no assist. I am not sure if pack would heat up with a dead cell. I don't think so. As long as the engine battery is being charged I would keep on trucking! Hal

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

No. The IMA motor would be working as a generator to feed high voltage to the power module behind the back seat. This module then splits the power into a charge current for the NiMH battery pack, and a separate feed that gets converted to 12V for the regular lead-acid battery and the 12V accessories. The IMA doesn't feed the voltage converter except when acting in boost mode. In regen mode (or with a dead battery), it's the motor that feeds the power into the converter.

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

Pull the fuse to your IMA battery - that will simulate a battey failure. - I did that to my 2007 HCH II. it ran almost 20 minutes before the 12v battery was too weak to continue ( probably a lot longer at highway speed but not too good at rush hour traffic). Yes, the IMA motor is a generator, but it not always producing enough power for the converter to keep up without the assist of the IMA battery. ( we put the fuse back and it started right up ). Honda changed the design for 2008 and 2009 and I have yet to try that on my 2009.

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

No, that simulates a completely missing battery. A failed cell or two will not cause the NiMH bus to drop to zero, it'll cause a drop of about 1.2VDC/cell, which if there are only a couple of bad cells, the rest of the battery pack will mask. A more realistic simulation would be to place a low-ohm, high-watt resistor (such as those used to bleed the high voltage bus of a large variable speed drive or UPS system) across one or two cells. Your dash should light up like a Christmas tree on LSD, but the car remains driveable (assuming, of course, that you consider the Yugo-like response we get when going through recals "driveable").

Regardless, it's still in everyone's best interest to get a new battery. What's the point of having a hybrid if you can't take full advantage of it?

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

Missing battery or dead battery - the same to the Hybrid. If the IMA battery can be recharged everything will work. As said above one or two cells failed will not keep the IMA from working a few more will act as if the battery is missing. Test show that the SOC shows no bars at about 120v or less. Full charged ( all bars ) seems to be 168 to 170v by the voltmeter. So maybe 15 cells can fail before a total IMA failure shows?

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

Could be... but before you get that many dead cells, you'll be staring at a dashboard that thinks it's having a bad '60s flashback.

Re: Can you run an HCH2 CVT with a dead NiMH battery?
 

:confused: Wow, these threads are great - so many opinons in a couple of days! From what I have read, I am talking about a pretty unlikely scenario - i.e the battery failing just outside warranty, and I think the numbers quoted by Honda are 0.2% failure outside the 80k warranty period. And if they are prepared to give a 150k warranty in California, Honda must be pretty confident in the life of the IMA battery. I decided to buy the Hybrid because with the $2100 tax credit, I figured that the gas savings would more than pay for the additional $1000 cost vs a regular Civic, and if I had to buy a battery for about $2500 (dealer quoted cost) I would still come out even. But once you get to 80k miles, the gas savings are a "sunk cost" (Of course I did also want to do my bit towards protecting the environment, but not being a film star, I cannot afford to spend money on something that does not make economic sense).
So I was thinking about what I would do if the battery had "failed" relatively soon after the 80k warranty expiration. By then the book value of even a Civic Hybrid (5 years old at my mileage rate) would be not more than $10k at best, so spending $4000 on it would not really make a lot of economic sense if you could still run the car as a less fuel-efficient and somewhat underpowered vehicle.
I think what I am hearing is that there could come a point when enough cells had failed on the IMA battery that the charging control system just wouldn't work anymore, so the lead-acid battery wouldn't get charged via the inverter that steps down the voltage. Then you would have to replace.
Since the IC motor can run while the car is stationary to charge the battery (mine often does when driving in certain hot, hilly environments), I don't see why the A/C wouldn't work if the charging system does still work.
My Civic has had no repair issues other than the rear suspension link problem common to all 2007 Civics so I expect excellent reliability on all non-IMA components. There was a 125K wraparound Honda warranty available at a discount up to 6k mileage which I think would have been worth the money, but I found out about that too late. I think any extended warranty available to me now would give so little extra coverage on the IMA as not to be worth it. I think I would just keep running on the IMA battery as long as I could and then try to replace with one from a wreckers yard and then sell the car while it was still running OK.
I am also anticipating reconditioned IMA batteries appearing on the aftermarket soon. After all, the cells themselves can't be that expensive, and that would be the only part of the system that would need replacing.
Thaks for the feed back -its a great help