I am considering purchasing a used 2008 Escape Hybrid 70k miles. Should I be worried about the hybrid battery life and the cost to replace them? This would be our first hybrid.

 

Yes.

The question all prospective buyers of used hybrids should ask themselves is, "if I had to replace this battery in a month, would I be okay with the purchase?"

Assuming it's out of warranty. If it's under warranty, then you just re-frame the question to reference the warranty end date vs. "in a month."

 

We passed on it. The price being asked isn't worth the risk of having to make a $5k repair in the unknown future. The cost to replace the batteries would be more than half of the price of the vehicle. Thanks for the reply.

 

The risk is extremely low. The failure rate of these batteries is close to zero. The $5000 battery replacement concern amounts to an urban myth perpetuated by automotive traditionalists who don't like hybrids.

The need for replacement batteries is more than filled by batteries available from wrecks. Asking prices for used FEH batteries on eBay currently range from about $600 to $6000. In the completed listings, only two have sold recently, for $100 and $450. Facilities set up to recycle these batteries never got going because almost all the batteries are still in use. And with no degradation in performance.

Since they contain ordinary cells, the few bad packs also can be renewed by replacing a few degraded cells.

 

Cite a reference for that claim please. The Sanyo produced cells are absolutely, positively not "ordinary cells" in any way shape or form.

 

I didn't mean to suggest the individual cells are so common that you can buy them at the local drugstore. There are all sorts of rechargeable and non-rechargeable battery formats that don't appear at the consumer level. I don't see why a special format would be developed just for hybrid car batteries. However if you know that is indeed the case, perhaps you could provide a citation.

The way the batteries are bundled may be unique, but that's trivial manufacturing and therefore irrelevant.

http://www.hybridcars.com/hybrid-car-battery/
"The Ford Escape Hybrid’s battery pack, made by Sanyo, consists of 250 individual nickel metal hydride cells. As with other hybrid battery packs, the cells are similar in shape to a size D flashlight battery. Each individual battery cell, contained in a stainless steel case, is 1.3 volts. The cells are welded and wrapped together in groups of five to form a module. There are 50 modules in the battery pack. The total voltage of the battery pack is 330 volts."

http://www.thehybridshop.com/media/b...escape-hybrid/
"According to data from Ford, of the 190,000 Escape hybrid batteries built prior to 2011, dealerships have only logged five instances of battery unreliability due to cell failure. "

I question that statement, since nowhere near that many FEH's and similar were built, and I'm sure there have been more than 5 battery failures. But the gist is the same, that the batteries are extremely reliable.

 

A better overview of the durability of the Escape Hybrid batteries:

http://wardsauto.com/news-analysis/h...ity-stuns-ford

Now I see where the 190,000 number came from. Unlike what the hybridshop article stated, the number included some Fusion Hybrids.

"
Ford recently bought back some Escape HEVs that, combined, had racked up millions of real-world miles for teardown and evaluation. Included were vehicles that served in Yellow Cab's San Francisco fleet and had accumulated more than 250,000 miles (402,336 km) during their tour of duty.
“I was very impressed,” says Chuck Gray, chief engineer-global core engineering for hybrid and electric vehicles. “Normally, with a taxi at the end of its service life, there's more degradation in the powertrain system.
“While we had very good simulations and tests, with the battery in particular, we're seeing results that are even better than our testing,” he tells Ward's.
Even after a quarter-million miles, the battery cells still had 85% of their original energy capacity, engineers say.
Of the 42.6 million individual cells that went into the nearly 190,000 HEVs Ford has sold, only five have failed, with the last failure occurring in 2007, the auto maker says.
“The odds of experiencing an issue with one of our hybrid battery cells is 8.5 million to 1 — about the same odds as a person being struck by lightning,” Gray notes."


Even, if after 250,000 miles, the typical FEH hybrid battery has lost 15% capacity, the regeneration system is only one way the FEH gets good mileage. Battery performance affects only the regeneration system. You still have a relatively small engine, stop/start, Atkinson cycle, and CVT. So depending on the style of driving, the battery/regen would be less than 50% of the efficiency measures of the vehicle. 15% of 50% is 7.5% 7.5% of 32mpg is a loss of about 2mpg. Not a big deal, and not until very high total mileage. At half the mileage, 125,000 miles, the impact would be 1mpg. This is why most FEH owners report no loss of mileage as the vehicles age.

I should also mention that some (or even most) of the very few used hybrid battery packs being bought probably are for FEH's that have seen their batteries damaged in accidents, rather than battery performance issues.

 

It's clear you have absolutely no relevant knowledge of hybrid batteries. The current (amperage) demands of a hybrid electric car or all electric car are orders of magnitude beyond anything even close to consumer grade cell/application. While these cells may not have been developed specifically for use in the Escape, they currently have no use in any significant application for the past several years due to high current NiMH cells in industrial applications being replaced by Lithium chemistries.

How the cells are bundled is not trivial or irrelevant. They are WELDED end to end because any other practical method of joining is insufficient for the current. Replacing an individual cell is a recipe for failure unless one possesses both specialized skills and equipment.

And there you have it... welded together.

Additionally, nominal NiMH chemistry voltage is 1.2V. Technical merit of the information is in question if that detail is overlooked.

I'm not going to cite marketing material in support of technical/service claims. I've seen the kind of work that The Hybrid Shop affiliates put out, and their level of service, and I am completely unimpressed.

IMHO, anything they say is suspect.

 

There have been variations in NiMh battery technology, and NiMH in general is known for fast discharge rates. So I'm not sure what would qualify as being relatively specific to hybrids.

Welding cells is not high technology, and probably is done precisely because this allows use of common cells rather than engineering special large format NiMH cells.

Welding them end-to-end certainly varies from the practice seemingly standard in power tool batteries etc, which is to use welded straps or wires to join them.

So in the extremely unlikely event you have a cell sufficiently degraded to need replacing, you replace a stick of 5. Big deal.

Is the nominal capacity of NiMH batteries used in cars different from the nominal capacity of NiMH cells used in other applications?


This is a youtube version of the article about Ford engineers examining the hybrid battery from a heavily used FEH taxi.

These are youtube videos of someone building a battery pack for an electric motorbike, from FEH battery sticks.

Until I looked these up, I assumed people were replacing individual cells. Instead, they are dealing with the sticks of 5 welded cells.

In neither of these cases were the sticks of 5 batteries disassembled. Other documents have referred to failure of individual cells. That's why I thought people were dealing with individual cells.

Presumably it's easier to diagnose a stick that contains a bad cell, than to cut apart a stick and locate the individual bad cell. Ford must have done that in order to make their pronouncement on the rarity of failures of cells, not sticks. Or maybe they just didn't bother to make a distinction.

Given the availability of used battery packs, I would assume those who recondition these battery packs are doing so by replacing sticks rather than individual cells. I don't know if new sticks of 5 batteries are available.

But in the form of used sticks, there seems to be no shortage of them and no great difficulty in dealing with them. This makes availability of the cells themselves irrelevant. Because failure of the pack is so rare it's vanishingly unlikely that anyone is going to have to deal with this. And if they do, it's not going to be a crippling expense.

 

I did a quick search on a junkyard search http://car-part.com/ and found quite a few just on that from about $400 up. I bet I can find them even cheaper in person if I call around. I was also worried about that at first when I bought mine but now its no concern to me.