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Help replacing/upgrading batteries

1666 Views 10 Replies 5 Participants Last post by  raphen
Hello community,
I have a Geo Metro electric conversion that needs its batteries upgraded. Currently installed are twelve Walmart branded 12 volt 114 amp hour deep-cycle lead-acid batteries. They got toasted trying to climb home. The road to my house has about 1/3 of a mile of 22% grade and nuked the batteries. It is an interesting feeling and experience climbing that hill as you can feel the electricity get pulled from the core of the batteries to the motor. It made it once but the second time had no chance of hitting the half-way mark and the brakes could not hold the weight. Thankful for my superb driving skills :rolleyes: :)

Anyway... I would like to upgrade my batteries to be able to use the vehicle. My aging CRV does not get very good gas mileage and need to watch the budget commuting to and from employment.

Have been interested in buying a salvaged LEAF or similar EV to scavenge the batteries and resale parts. That seems like the more economical route versus buying new "drop-in" batteries.

So this is why I come to the community. Looking for help in the calculations of what I will need. How many LEAF batteries? If I do the "drop-in" LiFeOS4 do I just match the number of batteries I currently have? What other alternative solutions may be out there?

Here are the details of the EV:

Motor: Netgain Impulse 9" motor
Controller: Open ReVolt 144 volt, 500 amp
Batteries: twelve 12 volt 114 amp hour deep-cycle lead-acid
System Voltage: 144 volts
Chargers(2): Quick Charge Octopus-AGM 10 Bank Charger
Quick Charge 2 Bank
DC/DC Converter: Kelly HWZ Series 144V TO 12V 300W
PakTrakr Battery Monitoring System, which monitors instantaneous
voltages of each battery in the pack.
Paktrakr Current Sensor, which monitors instantaneous
current delivered by the battery pack.
PakTrakr ES1R automatic logging serial interface for
recording instantaneous battery voltages and current.
The recorded data can be downloaded to a PC for detailed
analsys. 800.htm

Bluetooth RS-232 adapter for use with smartphone app
to display dashboard metrics on your smartphone.

adapter port, which allows it to accept a standard
Level 2 charging station J1772 plug.

And finally any suggestions on proper battery disconnect? Would like to remove old dead batteries so I can push the card around the yard and avoid potential damage from leakage etc.

Thank you in advanced!
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I would suggest a Chevy Volt pack - you can get them for about $2000 and while on paper they will have the same capacity as your lead in reality you will get double the capacity
I suggest you read this thread - I know it's long but there is some interesting stuff

The Volt battery is 9 modules - 7 off 2 kWh and 2 off 1 kWh

It's not difficult to re-organise at the module level - going below that to the cell level is nearly impossible
Hi again,
I feel more confused now after reading that post. Math and numbers added with internet forum short speak just will spin me upside down. But after a little deducing I may be on the right track. So here goes, please let me know if it is correct or not!

From what I understood from that post is that the Chevy Volt battery is 288v.

From what was stated above and in the post the battery pack is 7 batteries @ 2kwh each plus 2 batteries @ 1kwh.

The math of that is 16kwh.

16kwh is 16,000 volts.


Ok so realistically the 288v number is more of what I should be working off of. If my system is 144 volt max then I could assume that I would need half of the Chevy Volt batteries? I could do 4 @ 2kwh?

Update: @McRat says

Roughly 18 x 12 x 11 high for 2 x 2kWh in a block.

There are 4 blocks:

2kWh + 1kWh (72v)
2kWh + 2kWh (96v)
2kWh + 2kWh (96v)
2kWh + 2kWh + 1kWh (120v)

so I could do the 2+2+1 configuration.

Would be nice to be able to put the drivers seat back further so I could actually drive it.
Lets start
FIRST there are Volts and Amps - Volts x Amps = Power - Watts
Then there is capacity - measured in Amp Hours - one amp for one hour

16 kWh - is capacity and means that you can DRAW 16 kW for one hour - or 160 Kw for six minutes

The Volt battery has 288 CELLS
These are arranged in threes
So it has 96 Groups of three cells - the three cells are in PARALLEL

The Modules are

12 Series x 3 Parallel - 2 kWh - Seven of these

6 Series x 3 Parallel - 1 kWh - two of these

The individual CELLS are 3.5 volt empty and 4.1 volt full
So a 2 kWh module goes from 42 volts to 49.2 volts

The whole pack of Seven 2 kWh and two 1 kWh goes from 336 volts empty to 393 volts full

The whole pack is 16 kWh and nominally 350 volts
Which gives 45 Amp Hours - for the three cells in parallel - so each one is 15 Amp Hours - 15Ah

You can divide the pack up in all manner of different ways - it's generally best to use the highest voltage that you can

You have an Open Revolt - good controllers - I would run two "strings" each one would be three of the 2 kWh modules

The voltage would be 126 volts empty and 147 volts full
Which would give 45 x 2 = 90 Ah

That sound like less than your old 114 Ah batteries but with Lead acid you only get the 114 Ah at a very low discharge rate - far too low to be useful in an EV - in practice you would be lucky to get 60 Ah out of the 114 Ah batteries - so 90 Ah is about 50% more

That leaves one 2 kWh module and two 1 kWh modules left over - you could either get hold of another 2 kWh module to make up another string or use them for another project
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