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Discussion Starter #1
The Bolt EV carries a lead-acid 12V battery under the hood for accessory power and other functions. These things are HEAVY! Lugging that chunk of lead around for 100,000+ miles will waste a lot of energy.

Are there any technical barriers that preclude reducing a fair bit of weight by swapping out the lead with a much lighter 12V lithium-ion battery? I know that Li-ion is more expensive than lead-acid, but this would seem like a smart upgrade to save energy and money over the life of the vehicle.
 

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Replacing the AGM battery with a Li Ion one would only be a weight difference of about 15 pounds.

The curb weight of the vehicle is 3563 pounds. Reducing the weight by 15 would account for a 0.04% difference.

Assume 100,000 miles at 4 miles per Kwh at $0.13 per Kwh, you would spend $3253 on electricity.

If the weight reduction is directly proportional to energy efficiency gained, you would see a savings of $13.25

A replacement Li Ion battery costs about $200
 

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Cause lead acids handle temperature extremes better than Li batteries? Also, lots of existing OEM parts for 12V systems?
 

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Lithium drop in replacement 12V batteries work with lead acid charging systems with no concerns whatsoever. The round trip efficiency and standby charging losses will be decreased significantly as well. It won't be of any major advantage, but it will save some energy, have larger reserve capacity, and last considerably longer - especially if the battery ever happens to be stored in a low state of charge accidentally for any period of time. This was purely a cost move on GM's behalf.
 

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Discussion Starter #8

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I was referring to one of these types of batteries, which are designed to replace 12V lead-acid batteries with Li-ion: https://www.lithiumion-batteries.com/products/12-volt-lithium-ion-batteries/
Thos seem to have circuitry built into them.

Your kidding right? At that price! For a couple of pounds of weight! Wow i think I have better things to spend my money on. I use agms in all my ice vehicles, one jeep (has 2 optimas yellow tops) 7 years with tons of abuse, winching, dead in winter and they are still 100%! (I have very expensive battery testers (think midtronics) I have agm batteries in all my UPS systems, literally hundreds for as long, for the price they cant be beat sorry.

Now flooded lead acids, they should be banned......:)
 

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Some have tried replacing the 12v battery with ultra-capacitors in gas cars.
 

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Replacing the lead-acid with li-ion is a waste of money, IMHO. If you want to save 15lbs of weight, go on a diet and lose it yourself.

the lead acid is used for cold climates. If you don’t see below freezing temps, go ahead any way. Your money is better spent on a backup Li-ion jump-start battery, but that won’t work at cold temps either.
 

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The more interesting lithium swap question is... a lithium pack of the SAME WEIGHT as the stock lead battery would have how much energy inside of it? And would it extend your range any noticeable amount? By virtue of your accessory bat not needing to feed off of your traction battery. That ought to make the $200 battery look cheap in comparison.
 

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The 12v accessory battery practically doesn't feed off the traction battery. It's charged from the grid when the traction battery is recharged and periodically if it gets below some threshold. It's momentarily used to ready the electrical systems prior to closing the traction contactors. Once the traction contactors are closed, the DC/DC converter begins supplying 12v electrical systems and perhaps replacing what little energy was used in the 12v battery, which mostly lives at or very near to full charge.

What's interesting to me is that 12v lead acid batteries are less than 50% efficient at accepting a charge when nearly full, which is what is required to have a healthy lead acid battery. Lithium ion based batteries are much more efficient at accepting a charge when nearly full, and don't require being maintained at full charge for optimal longevity (less than fully charged being optimal). A LiFePO4 battery will be somewhere around 90% SoC when maintained by an alternator or DC/DC converter, which seems fairly optimal. In that case, I expect a LiFePO4 battery to last longer than a lead acid battery assuming you can somehow avoid charging it when it's below freezing.

I'm going into my 3rd winter on a LiFePO4 battery in the Prius, which I bought after the original was killed by leaving the drivers door open over the weekend. Since it lives inside the passenger cabin, it's fairly well protected from sub-freezing temperatures. It was slightly less expensive than the OEM at $120, although it has about half the capacity.
 

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Does anyone know the battery ratings for the original ACDelco 12v AGM battery installed in a 2017 Bolt EV? I've looked high and low so if someone responds, would love to know where you found it.
THANKS !
 

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Does anyone know the battery ratings for the original ACDelco 12v AGM battery installed in a 2017 Bolt EV? I've looked high and low so if someone responds, would love to know where you found it.
THANKS !
@drdiesel1 provided
It's a 50 AH @ 520 cold cranking amps.
here:
 

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Greetings. First post and am adding a link to a YouTube segment that I believe is the lead designer of the Bolt electrical system doing a walk through of the disassembled vehicle. Starting around the nine-minute mark the videographer asks why a lead-acid and not lithium, and the response is basically cost savings (the Bolt is manufactured at total loss already based from GM interviews and explanation of offsets for other products). My information is that the Bolt will run continuous 1600 watts from the 12v system with a pure sine inverter off the 12v battery terminals (fed by the main system battery), and that the only reason lithium is not factory installed is cost. I have a Westfalia that I outfitted with lithium phosphate batteries, and the cost in Canada retail from my auto-parts supplier came in much less than half the cost of USA sources as it turns out the premium batteries I purchased are manufactured in Quebec and distributed worldwide from there. My issue is where to locate the inverter in the vehicle. I have removed all the rear seats and interior from my Bolt and have an ongoing project that will get posted in due course. Meanwhile, have a look at the YouTube video:
 

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I'd say "cost" is a pretty safe catchall for the reason why anything better isn't implemented. It has to be better at a price. A lithium ion 12v battery would require environmental regulation just like the traction battery, otherwise it would quickly degrade (possibly instantly in certain conditions).

I found it cheaper to replace my Prius battery with LiFePO4, but that's because it's half the capacity of the 12v it replaces, and doesn't require extra environmental regulation since it lives inside the cabin rather than under the hood. It isn't the solution for everyone, but a lead acid battery is.
 

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I'd say "cost" is a pretty safe catchall for the reason why anything better isn't implemented. It has to be better at a price. A lithium ion 12v battery would require environmental regulation just like the traction battery, otherwise it would quickly degrade (possibly instantly in certain conditions).

I found it cheaper to replace my Prius battery with LiFePO4, but that's because it's half the capacity of the 12v it replaces, and doesn't require extra environmental regulation since it lives inside the cabin rather than under the hood. It isn't the solution for everyone, but a lead acid battery is.
I am new to these forums, so forgive me if I ask undeveloped questions. In context, I use my Bolt as a commercial vehicle and "cost" is not an issue for me at this point as it may have been for GM in the final build as per the engineer. I run my entire company off solar, and the Bolt is being adapted to replenish my batteries on site for cost savings. My tool batteries run $400 each, and I use up ten batteries per day already, and rather than purchase another ten batteries I am looking to continuosly charge them in the Bolt while the others are in use. My understanding from this thread is that lead batteries are an impediment to optimal transfer of energy relative to equivalent lithium, so if the engineer says that the only barrier is cost and that one could install lithium to improve the performance of the vehicle as a power supply, how does this relate to a Prius in the context of a lithium battery that already has regulatory approval in my jurisdiction for standard motor vehicle use?
 

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I am new to these forums, so forgive me if I ask undeveloped questions. In context, I use my Bolt as a commercial vehicle and "cost" is not an issue for me at this point as it may have been for GM in the final build as per the engineer. I run my entire company off solar, and the Bolt is being adapted to replenish my batteries on site for cost savings. My tool batteries run $400 each, and I use up ten batteries per day already, and rather than purchase another ten batteries I am looking to continuosly charge them in the Bolt while the others are in use. My understanding from this thread is that lead batteries are an impediment to optimal transfer of energy relative to equivalent lithium, so if the engineer says that the only barrier is cost and that one could install lithium to improve the performance of the vehicle as a power supply, how does this relate to a Prius in the context of a lithium battery that already has regulatory approval in my jurisdiction for standard motor vehicle use?
What sort of tool batteries are you using that cost $400, and do they even charge off of vehicle 12v power? (Very few tool manufacturers offer 12v chargers... But most also don't have batteries that cost more than $200 either...)

Lithium is better if you're routinely charging and discharging the battery, but that's not how most use cases for the Bolt's 12v battery work. If you're putting significantl loads on it, you want the DCDC power supply to be running (e.g. car is "on").

A potential issue with LiFePO4 in the Bolt as a replacement for the 12v battery is that the original Bolt battery is AGM and not wet-cell. AGM batteries typically have a somewhat higher float voltage than wet-cell, and I've seen that the Bolt's electrical system does seem to run a bit "hot" with voltages as high as 15v reported via OBD (haven't looked with a DMM yet...)

But for your use case, you want the car to be "on" and at that point, it doesn't matter much what's installed in the car.
 
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