If only one cell has failed, why do I have to replace the whole pack?

While that seems like a good question, when one understands how these things work and what happens to them over time and what’s entailed in ensuring a healthy pack, the question answers itself - because a game of whack-a-mole is only fun in an arcade - not inside a hybrid battery.

Let me present you with an analogy: You have an 18 wheeler with 18 bald tires. One has blown out. You take it to a truck stop, but before you do, you put covers over the other 17 tires, so they can’t see anything but the valve stem. They replace the blown tire with a used one, and they confirm the pressure is good on the other 17 tires.

What do you think will happen with one of the 17 bald tires? Yeah, one of them is going to blow soon.

Let’s break it down a little. Why did I do something silly like covering the tires? It’s to illustrate the point that the truck stop can’t even inspect the health of the tire tread or sidewalls for cracking - because those tell you something about the health of the tire. The only thing you can check is the tire pressure - which tells you nothing about the health of the tire - much like voltage tells you almost nothing about the health of a cell (a very low voltage can tell you a cell has failed, but a good voltage reading can’t tell you all cells are good).

Let’s say in 3-6 months, when you have a different tire blow, would you take it back to the truck stop and expect them to replace that tire for free because they checked the pressure (voltage) of the tire, but they weren’t allowed to assess the health of the tire? Of course not.

What you can’t see with a voltage check is the state of health of each module. At the time of a cell failure, the majority of the cells in the battery pack have deteriorated to 30-40% of their rated capacity (we’ve seen them as low at 20%). At this level, their cycle wear accelerates and failure occurs more frequently. When you replace a module, you have 20+ other modules with dramatically reduced capacity and reduced life. The reconditioning process restores the cells to their highest potential state of health expanding the available capacity and minimizing cell damage due to cycling.

From pull-up to drive-away, just replacing a module and maintaining an acceptable level of workmanship is going to require 3-4 hours of labor plus parts, and that’s without ANY diagnostics beyond checking voltages. Even at rock bottom shop rates, you’re looking at $300-350, and you’re looking at that EVERY time a module needs to be replaced… every 3-6 months.

Here at Phoenix Hybrid Batteries, we have 10-12 hours of touch-time wrapped up into testing and reconditioning each battery over a 3-5 week period. We’ve invested several thousand dollars in CUSTOM equipment that yields far superior results when compared to commercial options that cost many times as much (e.g., NuVant). We replace an average of 5-6 modules on every pack because they don’t meet our standards. THAT is what it takes to properly test and confirm a pack is as healthy as possible.

If it’s not worth doing right, it’s not worth doing. We’ve turned away many thousands of dollars of “module replacement” business over the years, and we don’t regret a single penny of it.

Many have presented an argument that they just want to get the car running, so they can sell it. Well, that’s just passing the buck. We won’t take part in screwing the next guy down the line.

If the above hasn’t answered your question, please give us a call or shoot us an email.

Thanks for reading!