Parallel Battery Packs

ServoScanMan · 07-30-2006, 08:51 PM

I had some time to kill the other day and noticed a used 2006 Prius HV battery pack on Ebay sold for less than $600 USD. It apparently came out of a car that had less than 6,000 miles. That got me to thinking...uh, oh....not again.

Anyway, if I put 2, 3, or 4 battery packs in parallel, would the ECU know the difference? I'm only dreaming about installing multiple packs and building my own HV plug in charger for the batteries. Thoughts? Is it possible?

**efusco** · 07-30-2006, 09:25 PM

Yes, it would know the difference, in most situations. It's possible to connect additional battery capacity without triggering error codes however.

This is no easy job, it is dangerous, and the battery has no means of being cooled, no means of monitoring the temp, and is not protected should you be in an accident....but it can and has been done.

Cheap! · 07-30-2006, 09:36 PM

<div class='quotetop'>QUOTE(ServoScanMan @ Jul 30 2006, 07:51 PM) [snapback]294800[/snapback]</div>

Quote:

I had some time to kill the other day and noticed a used 2006 Prius HV battery pack on Ebay sold for less than $600 USD. It apparently came out of a car that had less than 6,000 miles. That got me to thinking...uh, oh....not again.

Anyway, if I put 2, 3, or 4 battery packs in parallel, would the ECU know the difference? I'm only dreaming about installing multiple packs and building my own HV plug in charger for the batteries. Thoughts? Is it possible?
[/b]

Bwahhh, haaa, haa. Another madman in Texas!

How far is Lorena from Houston?

Should we try to conquer the world?

ServoScanMan · 07-30-2006, 10:04 PM

<div class='quotetop'>QUOTE(Cheap! @ Jul 30 2006, 08:36 PM) [snapback]294819[/snapback]</div>

Quote:

...How far is Lorena from Houston?...

[/b]

Don't you mean, "How far is Houston from Lorena'?

I'm kidding. I'm about 4 hours from Houston, give or take a traffic jam or two.

200Volts · 07-31-2006, 04:08 PM

What about a second 12V battery?
Now hear me out before you laugh.... The A/C is driven off the 12V system (from what I've read) so having more 12V amp hours in reserve (or a slower voltage drop in the 12V battery-s) will mean less ICE running to help cool down the car after sitting a while in hot weather.

or should I move to Texas also?

donee · 07-31-2006, 07:29 PM

<div class='quotetop'>QUOTE(200Volts @ Jul 31 2006, 05:08 PM) [snapback]295276[/snapback]</div>

Quote:

What about a second 12V battery?
Now hear me out before you laugh.... The A/C is driven off the 12V system (from what I've read) so having more 12V amp hours in reserve (or a slower voltage drop in the 12V battery-s) will mean less ICE running to help cool down the car after sitting a while in hot weather.

or should I move to Texas also?
[/b]

Hi 200Volts,

Nope, the AC is run off the 200 volt battery. You should know that Mr. 200Volts! Don't you feel kinda dragged out when its hot outside ?

hobbit · 07-31-2006, 08:38 PM

Go read Wayne Brown's site ... http://privatenrg.com/
Go catch up on the earlier archives of http://calcars.org/ to see
some of the early problems they ran into...
.
Parallel packs are doable and rumor has it that the Prius BMS
can learn about the larger capacity but you'd better have SOC and
temp control just as rigid as the Prius ECU itself and all the
appropriate safety stuff in place.
.
_H*

ken1784 · 07-31-2006, 09:31 PM

Parallelling NiMH battery is not a good idea.
I've never seen any good professional application using parallelling NiMH batteries.
Does anyone see any?

Ken@Japan

c4 · 08-01-2006, 11:34 AM

The problem with paralleling battery packs is that the two packs must be exactly matched in capacity and charge level.. The problem is mainly with the charging of the packs- you can make things work for a while, but as soon as the two packs show any significant difference in charge level, the whole thing goes unbalanced and you end up cooking one battery while chronically undercharging the other until both batteries are dead.. This is why, except for early testing, all the EV mods have gone with complete battery replacements, or only allowing discharge in parallel and preventing parallel recharging via a diode (the aux pack would then be mains charged, creating a PHEV)..

Even the 12V systems are not true parallel systems, because they have an isolator in between and the charging paths are independent to prevent battery damage.

ekpolk · 08-01-2006, 01:20 PM

At the outset, please forgive my ignorance -- I'm brand new to the Prius thing (just got mine on Saturday), and I'm at best an armchair engineer. All that admitted, what would be advantage to the parallel battery? I certainly have not explored all the dark corners of the "envelope" with my car yet (I've put ~350 miles on it so far, 75/25 highway/city), but I have not seen the HV battery either completely full or completely drained. Since, of course, the battery merely stores energy, rather than generating more of it, how would more capacity help when one battery does not seem to "fill up" by itself?

08-01-2006, 01:20 PM	#10
ekpolk The Regenerator Join Date: Jul 2006 Location: Pensacola FL Posts: 363 My Car: 2004 Prius Package: #9 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	At the outset, please forgive my ignorance -- I'm brand new to the Prius thing (just got mine on Saturday), and I'm at best an armchair engineer. All that admitted, what would be advantage to the parallel battery? I certainly have not explored all the dark corners of the "envelope" with my car yet (I've put ~350 miles on it so far, 75/25 highway/city), but I have not seen the HV battery either completely full or completely drained. Since, of course, the battery merely stores energy, rather than generating more of it, how would more capacity help when one battery does not seem to "fill up" by itself? __________________ ScanGauge-IIx for the TCH CAN View V3 (for when I care about maximizing Prius benefits). Valentine V1 (for when I *don't* care. . . ). Now in the TCH -- with Remote Display. Black 09 Camry Hybrid Cassis Pearl 07 Avalon XLS Black 04 Prius

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07-30-2006, 08:51 PM	#1
ServoScanMan Senior Member Join Date: Apr 2006 Location: Lorena, TX Posts: 238 My Car: 2006 Prius Package: #1 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I had some time to kill the other day and noticed a used 2006 Prius HV battery pack on Ebay sold for less than $600 USD. It apparently came out of a car that had less than 6,000 miles. That got me to thinking...uh, oh....not again. Anyway, if I put 2, 3, or 4 battery packs in parallel, would the ECU know the difference? I'm only dreaming about installing multiple packs and building my own HV plug in charger for the batteries. Thoughts? Is it possible?

07-30-2006, 09:25 PM	#2
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 14,247 My Car: 2004 Prius Package: #9 Nominated 1 Time in 1 Post TOTM Awards: 0 Friends: 24	Yes, it would know the difference, in most situations. It's possible to connect additional battery capacity without triggering error codes however. This is no easy job, it is dangerous, and the battery has no means of being cooled, no means of monitoring the temp, and is not protected should you be in an accident....but it can and has been done.

07-31-2006, 04:08 PM	#5
200Volts Senior Member Join Date: Nov 2004 Location: Northern CA Posts: 346 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	What about a second 12V battery? Now hear me out before you laugh.... The A/C is driven off the 12V system (from what I've read) so having more 12V amp hours in reserve (or a slower voltage drop in the 12V battery-s) will mean less ICE running to help cool down the car after sitting a while in hot weather. or should I move to Texas also?

07-31-2006, 08:38 PM	#7
hobbit Senior Member Join Date: Mar 2005 Location: Bahstahn Posts: 2,989 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Go read Wayne Brown's site ... http://privatenrg.com/ Go catch up on the earlier archives of http://calcars.org/ to see some of the early problems they ran into... . Parallel packs are doable and rumor has it that the Prius BMS can learn about the larger capacity but you'd better have SOC and temp control just as rigid as the Prius ECU itself and all the appropriate safety stuff in place. . _H*

07-31-2006, 09:31 PM	#8
ken1784 SuperMID designer Join Date: Dec 2003 Location: Yokohama, JAPAN Posts: 1,391 My Car: 2004 Prius Package: G Touring Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 3	Parallelling NiMH battery is not a good idea. I've never seen any good professional application using parallelling NiMH batteries. Does anyone see any? Ken@Japan

08-01-2006, 11:34 AM	#9
c4 Join Date: Mar 2005 Posts: 523 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	The problem with paralleling battery packs is that the two packs must be exactly matched in capacity and charge level.. The problem is mainly with the charging of the packs- you can make things work for a while, but as soon as the two packs show any significant difference in charge level, the whole thing goes unbalanced and you end up cooking one battery while chronically undercharging the other until both batteries are dead.. This is why, except for early testing, all the EV mods have gone with complete battery replacements, or only allowing discharge in parallel and preventing parallel recharging via a diode (the aux pack would then be mains charged, creating a PHEV).. Even the 12V systems are not true parallel systems, because they have an isolator in between and the charging paths are independent to prevent battery damage.