2001 prius hv battery help

Your choices:

• ~$2,300 - buy traction battery from Toyota, swap electronics/modules
• ~$1,500 - buy Dorman rebuild, $1,000 core charge, swap batteries
• $?? - buy modules, learn how to rebuild pack, and repeat

Speculation on my part, it sounds as if an internal short drained the modules on one side of the pack. Alternatively, someone tried to rebuild the pack and failed to balance the modules. Check the module serial numbers and see if there is a break in the order that corresponds to the failed modules. Also, check the sensor connector.

The battery has module pairs and the voltages are monitored by one connector to the battery control electronics. You want to see if there is any evidence of a problem with the connectors.

Bob Wilson

 

The newer modules have lower internal resistance so their voltage swing is more moderate than the older modules. Since you are replacing at least 12, I would recommend get 20 new modules and keep the 20 best old modules. Then pair old and new . . . assuming you can handle the slight offsets of the terminals. Alternatively, stack one side new and the other side old.

Check some of the early postings but the problem becomes:

• matching amp-hour (Ahr) capacity - the weaker modules, each contains six cells, will have a greater voltage swing as a function of State of Charge (SOC). A weaker module can go into voltage ranges either too high, out-gassing and heat, or too low, loss of NiMH function.
• matching initial SOC - all 38 modules need to start at the same, middle value. The Prius will seek to maintain 60% SOC and if any are too high or too low, it again can drive those modules into too high or too low voltage regions.

Don't forget you will need NiMH aware, battery charge-discharge units to measure what you've got. The balance charge is not too hard by wiring them all in parallel and either charging up to a set voltage or discharging down. But knowing the module capacity is key to re-stacking the modules:

• pair weakest and strongest on ends of string - this way the measured pair will appear to the battery controller to be 'like the others.' The ends are the coolest parts of the stack and heat is the enemy.

GOOD LUCK!
Bob Wilson

 

Correct, a total of 38. The challenge will be matching Ahr capacity. So look for a battery charger-conditioner:

• NiMH chemistry, 6-cells (each module)
• Stops charge based upon all three:
  • dV/dt - the voltage drop that signals fully charged
  • temperature limit - sometimes dV/dt does not work so don't let it thermally runaway
  • charge limit - these are rated 6.5 Ahr so no more than 6500 mahr or 6.5 Ahr

Do take the buss bars off and start working on removing the corrosion. Look carefully at which ones are closest to the 8-12 failed modules. Search the message archives as I remember someone having success with acetone. Pay close attention to the 19 sense wires. Corrosion can 'eat' the copper inside the insulation.

Bob Wilson

 

Owch! Let me suggest find the URLs for the top 3-4 charger User Guides and post them here. List them in order of what makes sense to you (some may be written in Chinglish) and I'll review them and post my opinion. I need you to start the selection and 3-4 on your top list lets me and our collaborators offer our experienced opinions.

I am not trying to be coy but it will be your tool and what appeals to me might be poison ivy to you.

Bob Wilson

 

I'd assume without looking in any detail that they are all essentially similar. One word of advice - pay attention to maximum discharge rate. If you plan to cycle through charge/discharge cycles (and you probably should plan to do tht!) it's the discharge cycle that takes time. Most small chargers have a 50-80 watt charge but only a 5 watt discharge, so it takes 10x longer to discharge than to charge. I ended up springing for the Thunder Power 1430 mostly to get the higher discharge capabilities, 50 watts IIRC. TP has a good name in the hobby community. Most of the specs focus on charge rate but it's really discharge rate that's the bottleneck in our case. Also remember that many of these chargers need a power supply, and if you're charging banks of modules the poser demands can be pretty high - in the case of the TP1430 the charger is capable of delivering up to 1000 watts. I had a big power supply already, but if you're buying this stuff you can pay as much for the power supply as for the charger. Hope this helps. Jeff

 

You really should measure capacity of each module and rebuild the pack with similar capacity modules. Throwing some new cells at the pack is only a short term fix. Get ready to play whack-a-mole!

 

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  • delta V, good
  • charge/discharge cycles, good
    • single display of last charge/discharge, weak
  • battery setup memory, good
  • discharge 1A, adequate by means Ahr = hours per module
  • AC powered version, good
  • no temperature limit detect, bad
  • no charge limit setting, only delta V, bad
  • Recommend call Thunder Power as these may have been resolved
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  • has charge limit setting, good
  • has time limit setting, OK, mitigates lack of module temperature monitoring
  • requires a high amp, external 12V power supply

I would recommend calling the sales lines of the vendors and explain you need to measure the amp hour capacity of Prius, six-cell, NiMH modules rated at 6.5 Ahr. At a minimum, you need to cycle discharge-charge the six-cell modules safely. The clueful ones will work with you. The others . . . . have another business model.

RECOMMENDATION:

1. Buy battery charger from someone with a fair return and/or upgrade policy.
2. Practice with the discharged modules
   1. return or replace as you find what works and doesn't

Understand building a good battery on the cheap takes time. There will be at least 38 modules to test and rate.

Bob Wilson

 

The economics will dictate whether replacing cells or replacing the whole battery is the answer. If only a few cells are bad in an otherwise good battery, just replace the cells. If most of the cells are poor, you're wasting your time and money replacing cells.

 

Over the last 18 months I've been seeing a lot of dying Gen1 modules. Some of them are now 14-15 years old, and even low mileage cars have batteries dying because of age (not mileage). If you are a hobbyist with lots of spare time (and another vehicle to use while the Prius is down) you can try refurbishing the modules with RC chargers, but it's a gamble.

Cook71, you should log all the time you spend on the project and share results so others can determine if it's worth the time involved.

 

I'm surprised any of them lasted that long, quite frankly.