Adding Batteries to Tired Battery Pack?

3175 Views 11 Replies 4 Participants Last post by dtbaker, Mar 4, 2011

irish_pilot

Discussion Starter · Mar 3, 2011

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.

My thought is to add 2 fresh batteries to help out...here's how, and let me know if this is a really bad Idea.
My controller is a Kelly 144 volt (KDH14500B)
My Charger is a Quick Charge set to 120V system.
I have 10 12v batteries currently
My DC-DC is a 128V-12 Sevon

I thought I could add 1 or 2 more batteries in the series, but leave the Charger connected on only the 10 existing batteries, thus maintaining the existing pack. Then Charge the new battery(s) with a separate charger.
Thus the only time the old and new would be in the "series" is during actual driving. They would be charged separately.

Q? Would they need to be (more) separated during charging? (there is a big disconnect which is off when car is not used)

Q? Could I connect the DC to DC to wires tapping only 128V (orignial 10 batteries) would I be better off removing DC converter and using a separate battery for 12V (short drives anyway)

Q? is there any reason to hook new batteries in parallel to (one or two ) of the original batteries (just during driving) instead of series

Q? would adding 2 batteries in the series help with reserve power, thus drain the current batteries less during our 5 mile drive.

Q? Any other thoughts on getting more time out of these batteries before they are recycled? (and I find a great deal on new ones)

Thanks
Paul

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rwaudio

· #2 · Mar 3, 2011

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.

My thought is to add 2 fresh batteries to help out...here's how, and let me know if this is a really bad Idea.
My controller is a Kelly 144 volt (KDH14500B)
My Charger is a Quick Charge set to 120V system.
I have 10 12v batteries currently
My DC-DC is a 128V-12 Sevon

I thought I could add 1 or 2 more batteries in the series, but leave the Charger connected on only the 10 existing batteries, thus maintaining the existing pack. Then Charge the new battery(s) with a separate charger.
Thus the only time the old and new would be in the "series" is during actual driving. They would be charged separately.

Q? Would they need to be (more) separated during charging? (there is a big disconnect which is off when car is not used)

Q? Could I connect the DC to DC to wires tapping only 128V (orignial 10 batteries) would I be better off removing DC converter and using a separate battery for 12V (short drives anyway)

Q? is there any reason to hook new batteries in parallel to (one or two ) of the original batteries (just during driving) instead of series

Q? would adding 2 batteries in the series help with reserve power, thus drain the current batteries less during our 5 mile drive.

Q? Any other thoughts on getting more time out of these batteries before they are recycled? (and I find a great deal on new ones)

Thanks
Paul

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

· #3 · Mar 3, 2011

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

Discussion Starter · #4 · Mar 3, 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

· #5 · Mar 3, 2011

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?)

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

Thanks
Paul

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

· #6 · Mar 4, 2011

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

Discussion Starter · #7 · Mar 4, 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

· #8 · Mar 4, 2011

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

Discussion Starter · #9 · Mar 4, 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

· #10 · Mar 4, 2011 (Edited)

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?
Thanks
Paul

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

Discussion Starter · #11 · Mar 4, 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

· #12 · Mar 4, 2011

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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