Battery Banks From Gen2 Battery Modules

Hi all,
Been away from the forum for a while, probably cause my 2006 Gen2 going quite well after replacing the traction battery 3 years ago with a 3 month old unit from a wrecked taxi.
Got it for $300 AUD, pretty happy with the purchase as Toyota after initially agreeing to warranty my battery
as I had only 130 kms on ODO, the dealer then reneged after I took car in for analysis, quoting I hadn’t had the last service carried out by Toyota.
As if they service the traction battery, most techs would be too scared to go near it........

anyway within 3 weeks of the first battery code P0030 from memory, the top blew off one of the modules.
Pretty crazy and loud, I happened to have enginelink connected via OBD at the time, the faulty hv block exceeded 20 volts then quickly went up further as the module blew up.

I had to rejoin this forum as my email got hacked, previously my tag was OZTRAX
and if you search this name you can see my previous posts.

here is my ex taxi battery, I did clean up the terminals before installation

 

Ok so I got 6 hybrid battery assembly’s for $600
1 prius gen 2 and 4.5 Camry for a total of about 220 modules.

I call these modules by their model number NP2



That includes the 26 modules I removed from my original battery
I cycled the original modules with an imax X100 touchscreen RTC charger
Nice unit but overheated and died after I completed about 18 modules


these are the photos I can find using that unit, I think it still charges but won’t discharge.
That was about 3 or 4 years ago and after I got the extra 200 modules decided this would be my stay at home “covid19” project. We had police enforcing staying at home over here, eg if you were in public in groups you could be fined.

idea is to put 3 modules in series to get 24 v (I couldn’t see the maths working to get a 12 v equivalent eg 2 modules in series)
Then parallel 4 of the series blocks to get a bank of 12 modules with an expected capacity around 600 wh

regards
X

 

So I threw together 12 modules to get a 24 volt Bank.
estimated an 26AH or 620 WH
Eg 2 of these blocks would be over 1 kilowatt hour of useable power.

:


I bought 2 Astroflight constant current RC chargers from eBay for $20 each.


these charge at around 7 amps max at 24-26 v
Which is pretty good that’s like 180 watts. Fed by 12 volts via a 300 watt RC EFUEL power supply.

So 4 modules at once, are first cycled in the IMAX B6 Quattro with the following settings:

charge current 1 amp
Discharge current 2 amps
Discharge voltage 6.0 v
wait time 60 mins
discharge/charge cycles 2
delta V peak 2
capacity 7 AH

I now use 9 AH as my capacity limit.

I have capacity checked using this method about 100 modules so far.
80% of those cells exceeded selected capacity within 2 charge/discharge cycles.
Another 10% require 2 or more cycles, but after 4 cycles I leave them recover for a day or 2.

im probably down to 70% passing 9AH as the new capacity as I now measure capacity both for charge and discharge cycles.


The idea is to leave the modules at 6 v and then link 3 in series, trying to maintain not only capacity but end point charge and discharge voltage for cell balancing. (Very tricky in reality)

I then charge the (3 module) 24 v block on the Astroflight initially a trickle 0.7 amp to 21 v C/10
Then 2.1 amp to 23 ish. C/3
Then the full 7 amps to 26.2 to 26.4 V. C/1
But my cutoff for charging is via temp gradient rise or a temp above ambient of 5 degrees C.



I have used various PCBs and gadgets, but ultimately when I develop a definitive procedure will use an ATTiny24 microprocessor to be the brains.


load test is via a 24 volt 100 watt aircraft taxi light, at around 90 to 96 watts discharge.
At 18 v a relay shuts off the discharge and an exotic shunt with as wireless screen acts a coulomb counter

 

Mmmmmm no comments or replies yet,

well how about some of you experienced battery cycling members give me your opinion on if I succeeded or not.

Shall we say a guessing game on the maximum WHs I achieved from 26 to 18v with the 100 watt load, which is close enough to the standard C4 rating most auto batteries utilise.

So remember charging NiMh batteries in parallel is fraught with peril, and I’m charging in series/parallel together
I guess I have made a 18S/4P battery , for those of you that know that terminology.

I know the WH answer of course, but am curious what sort of CCA I could get out of one of these 12 modules banks, if someone with experience has done any higher discharge testing , I would appreciate their input.

also if anyone wants to seriously give this bank idea a try, contact me and we can share some of the workload, eg building the ATTiny circuit and the eprom programming , which I will be doing in “C”

A 7 module in series 48 volt block could have good potential for solar off grid application.
I estimate the end point discharge would be no less than 42 volts, meaning the inverter won’t have cutout,
On the charge end we could be looking at 58 volts, possible on some off grid chargers.

so say 8 amps in series by 50 volts
350 watts of power from 7 modules, gutsy effort.

food for thought

regards
X

 

i agree with ur methodology here
by the time i reach 26v the temp is starting to rise
would like like to trickle to finish off
might try 1.5 amps as i think 0.7 per module makes sense

i melted 3 modules in 15 mins when i got distracted previously

reached 70 deg C

to quote bob wilson u only have to drop ur guard for a few mins to cause
a chernobyl melt down

i have been a bit conservative with final temp rise since then.....

X