Custom built, large Ah HV Pack replacement

What is your motivation to do this:

1) You want a higher capacity battery than the original
2) You want a less expensive alternative for battery replacement
3) or ??

If 1), the Prius is not really set up to use a higher capacity battery than it is equipped with.

If 2), my guess is that you could spend $1.5K or more on 38 6 volt batteries, they collectively would be quite heavy, and this is not an economical alternative compared to buying a salvage battery, for example.

If you have some other motivation for doing this, let us know what it is.

 

FAQ

 

You could make a double pack with the BMS+ system, and also add a 2kwh enginer style system. that way you have a big traction pack for longer EV and large regen, and can top off from an auxiliary pack as well. Although, the einginer system allows better mpg by keeping the traction battery at a high SOC, but yours would stay lower if using the BMS+ system.

I'd rebuild it with normal gen2 cells, and add an Enginer style plugin auxiliary pack.

 

You might consider posting "hello" to get your posting count up to 5, which I understand is the threshold. Perhaps, "Testing 3" with a link, "Testing 4" with a link, and "Testing 5" with a link.

I think you may want to reconsider some of your assumptions by comparing the various battery charging curves and characteristics. Orange4Boy posted a note about a modified 12 V battery configuration that included a separate set of cells from another, partially destroyed battery. This gave him a 14 V, lead-acid battery for his plugin that drives the 12 V DC system. I suspect you may need something along the same lines.

Bob Wilson

 

sweet! and you can pulg itin as well?

 

Congratulations to you!

Please do not say that the engine is "dying", unless the car logs DTC P3191.

Absent any DTC being logged, the engine is merely "resting".

 

Calculate the peak-voltage for half-wave, 120 AC. My rough order magnitude calculation is 1.414 * 120 ~= 169.7 V.

So take a power cord and power diode and 200 VDC capacitor. Wire it up so the capacitor is charged from the AC line and measure the DC voltage on the capacitor.

The power factor s*cks but you'll be pretty close to 160 V. AC.

Now if you want to draw some serious power, two caps and two power rectifiers. you should easily achieve ~300 VDC and be able to draw some serious power. You'll probably want a switching buck regulator to bring the output voltage down to a reasonable level but we can go into that in another posting. Or get a full-wave rectifier from Radio Shack (you can get less but you can't pay more) and a single cap. Toss in a choke and you can put something together, quickly.

Bob Wilson

 

Yes but think of this simple power supply as a quick hack ... more of a 'I need something right now.' Also, be very, very careful about the hot and neutral. Without an isolation transformer, any piece of earth ground could be lethal. . . .

You might check Ebay as I've often seen lab supplies for reasonable numbers. They often have voltage and current readout and are isolated from line power.

Designing and building power supplies is a lot of fun the first two or three times. But it is much easier to buy one and concentrate on the interesting physics.

Bob Wilson

 

Statultra built one from scrap parts. Unfortunately he removed the pictures. Might want to try and contact him. Pretty funny since he used a big tin can as the charger body. It has been done and proven to work.

 

Is it truly parallel with the stock pack? If so, what are you
doing with the point where the mid-pack safety plug hooks in?
.
Be prepared for problems if you're paralleling mixed chemistries
without any kind of current limiting between them. I have a
minor rant on this in the recent battery exploration, and have
gotten more than one report of stock packs and ECUs getting
totally confused by what's going on with direct-connect based
systems.
.
Now if you design a nice bidirectional switching current regulator
for the whole thing, be sure to post your schematics!
.
_H*

 

Since the traction battery banks are normally isolated from the chassis, the risk is somewhat mitigated. I would recommend using a polarized, AC plug, and make sure the neutral is on the nominal ground or negative lead.

One quick hack for a current limiter uses an LM317T:
Regulators and Power Supplies

The LM317T is available from Radio Shack and rated at ~35 V. As long as the voltage difference between the pack and the regulator is less than 35 V, the part should handle current regulation. Just make sure you have a heat-sink and thermal paste. You'll probably want to limit the current to 500 ma or less just to stay on the safe side.

Now I'm a fan of using solid-state relays because they typically have a low-voltage control line. A simple voltage divider can provide the feedback in either a current limit or voltage limit mode. Ebay shows a bunch under $10.

Bob Wilson

 

i didnt remove the pictures, i guess it removed itself ( imageshack ) . well anyway i havent touched my charger since 2005, ill dig it out and take it apart and take pictures, it goes to like 160-170 volts floating above the half of the hv battery, its a very low amp charger that way i dont blow up my battery.