# Adding Batteries to Tired Battery Pack?



## rwaudio (May 22, 2008)

irish_pilot said:


> Hi All,
> My first post here. I just bought a converted GEO with 10 AGM batteries.
> These were great batteries in their day, but are becoming tired (C&D Technologies UPS12-475FR) I am getting 5 miles or so out of them (easy) 25 to 45mph ... during this cold weather (35-44degrees) and thats all we really need for our runs to the store. So I hope to get a few more months use out of them.
> I have done a refresh charge on them (as per the manufacturer) of 2.4v per cell. And maybe that helped but not by much.
> ...


Welcome Paul,

If you added two batteries to the series and charged them how you described it would work IF the chargers are isolated.

Adding cells in series will decrease the current required for your normal driving and will increase your range. Normally adding new cells to old cells would be bad if you were going to charge them together, however if you charge them seperatially then you should be fine. Also running the dc/dc converter off part of the pack would be bad if you weren't charging seperatially.

It's not the ideal solution, but it would get you a little life and extra range out of the pack.


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## ngrimm (Oct 19, 2007)

Do all of your current batteries show the same voltage after driving or are some lower than others? Once one is dead you are pretty much shut down regardless of the charge remaining in the others.


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## irish_pilot (Jan 25, 2011)

RWAudio,
Thanks for the response. By "Isolating" the chargers, do I need to do more than
hook the 120v where it is now, and then hook the 12v or 24 charger to the new batter(s) during charging... Is any other "isolation" needed? (diode...battery isolator circuit?)

ngrimm,
They are within .2 volts of each other...not ideal, but they don't seem kaput.

Thanks
Paul


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## rwaudio (May 22, 2008)

irish_pilot said:


> RWAudio,
> Thanks for the response. By "Isolating" the chargers, do I need to do more than
> hook the 120v where it is now, and then hook the 12v or 24 charger to the new batter(s) during charging... Is any other "isolation" needed? (diode...battery isolator circuit?)
> 
> ...


By isolated I mean it's part of the battery charger design. Some chargers will have the negative output connected to AC ground or neutral, if you tried to connect a couple chargers like that to a pack in series they would short out or go up in smoke etc. Often the manufacturer will list "Isolated" as a feature or spec. 

Basically since you need to add 1 or 2 chargers to make your plan work, make sure they are isolated chargers. As long as the chargers you add are isolated then it doesn't matter if the existing one is or isn't.


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## dtbaker (Jan 5, 2008)

irish_pilot said:


> ...I hope to get a few more months use out of them.


unbalanced pack kludges generally lead to more pain than savings.....
turn them in for salvage/recycle, and go lithium!


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## irish_pilot (Jan 25, 2011)

Dan,
Of course I like the Lithium Idea. Please everyone keep me posted on reasonable prices for lithium. Some how the concept of spending way more for the batteries than the car cost is hard to deal with. The other thing is driving a $10,000 Geo metro seems just wrong. I think If I had a converted Jensen Healey or Corvette I could stomach the 5-6k battery pack.

The funny thing about a Metro, is with ICE it would get 40+mpg, pretty low cost per mile even at $4 per gallon. I enjoy driving one as an electric. But the cost per mile with Lithium over 5-8 years, just does not calculate...perhaps that will change soon on Lithium prices.


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## dtbaker (Jan 5, 2008)

irish_pilot said:


> Please everyone keep me posted on reasonable prices for lithium. Some how the concept of spending way more for the batteries than the car cost is hard to deal with. The other thing is driving a $10,000 Geo metro seems just wrong.
> 
> The funny thing about a Metro, is with ICE it would get 40+mpg, pretty low cost per mile even at $4 per gallon. I enjoy driving one as an electric. But the cost per mile with Lithium over 5-8 years, just does not calculate...perhaps that will change soon on Lithium prices.


I DO think the numbers work with the price of Li down to $1.15-1.20 per ah, and gas at $2.75 or more.

This works out to cost of Li somewhere between $.055-.08 per mile, and the cost of gas plus oil changes right around $.08 in the same little geo. Sure I'd like a spyder 550, or a mga, but for a virtually free small 4-seater, you can't beat the availability of the goe/swifts out there!

http://www.envirokarma.org/ev/01.Design.shtml


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## irish_pilot (Jan 25, 2011)

Dan,
When you say 1.20 per AH I assume you mean X voltage + BMS...?
If I want to take my Geo with 120volts and run it with lithium, how much will
that cost and where is the best supplier?
Thanks
Paul


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## dtbaker (Jan 5, 2008)

irish_pilot said:


> Dan,
> When you say 1.20 per AH I assume you mean X voltage + BMS...?
> If I want to take my Geo with 120volts and run it with lithium, how much will
> that cost and where is the best supplier?
> ...


the price per ah varies between Thundersky/CALB, and also whether you decide to trust someone with a pre-paid check and ship FOB china, or buy from stock already in US which is more expensive.

The metro/swift is GREAT now with 8" motor and 38 cells of 100ah (120v nominal to match motor and curtis 1221 controller.) not a race car, but very drivable, light years better than the previous 96v of FLA. the 38 cells of 100ah is a tight fit with 15 on front crossmember, and 23 under rear seat in the space I had 6 x 8v FLA. You could maybe squeeze a couple more under the hood, or a couple more under rear seat..... or give up some rear cargo space if you wanted more range.

I do not include the price of a BMS because I decided NOT to use one.

The 38 x 100ah pack worked out to $5416 incl bus bars and hardware S&H to my house from EVolveElectrics.com They were great, and use a bigger outfit AllianceRenewable to handle the China connection that has been very trustworthy. Only other guy I think I would go with at the moment would be Dave Kois at currentevtech.com if the price was better.


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## irish_pilot (Jan 25, 2011)

Dan,
thanks for that information...Gonna be a while before I can pony up 5 large on the batteries. Did that include a new charger and BMS?

I think I am back to boosting my pack with a couple of new batteries... Its actually quite zippy with the old AGM's I got. If I did not have to go 45mph soon after leaving my house, I would probably have much better range. 
Cheers
Paul


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## dtbaker (Jan 5, 2008)

irish_pilot said:


> Gonna be a while before I can pony up 5 large on the batteries. Did that include a new charger and BMS?


it's totally worth it....

$5k for the batteries. I do not have a BMS. I did buy a new charger and dc-dc and hope to sell the old ones to make that part of the upgrade close to a wash.

anybody want a 96v FLA Zivan ng-1? or 96v Curtis 1400 dc-dc?


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