72 volt Geo Metro
 

Hi there all.

Ok last week I picked up a Geo Metro that had been converted over to electric. Got it for a very reasonable price. It has 6, 12 volt group 27 deep cycles in it. They charged it up the night before I picked it up and then I drove it about 2 miles to work. Where I left it for the night and I too plugged it in to charge.

I brought my truck to work with trailer to bring the Geo home. I found a loose connection on one of the batteries and tightened it back up. I took it for a spin around the block not more than 2 miles and parked it until after work. Then loaded it up and brought it home. I live 3 mile from town and was told by the previous owner that it would go about 15 miles on a charge. So I headed off to town to get a extra key made. Thinking I had about 10-12 miles left on the charge.

I hot foot it to town, checking it out and seeing what it will do. Make it to town no problem. Park at the hardware store and get the key made. Maybe 10 minutes.

Then jump back in and head for home. Small incline getting out of town but then its a slight decline out of town to home.

I notice that I am not doing so well and can only get it to pull 100 amps I am maybe doing 20 mph I make it to the top of the small incline and break over the top. I am on the down hill run now but am still loosing speed. I stop at a parking lot and give the car a rest. I looked for an outlet but none to be found. I let it sit for about 10 minutes or so and check the voltage it was back up closer to 80 volts so I head out things are good but then I am back to 100 amp max and dropping. I don't want to hurt the batteries so I pull over in an empty field and park well off the road. About 3/4 mile from home.

I hike over to home and grab the EU2000 gen and head back to the car. Give it a 20 min charge and get it back to home. I charge it up Next day I take it to town again. This time with the gen in the back just in case.

I make it to town this time i try not to pull more than 200 amps on the way in and then get mail and head home I make it to home but just make it, and its only going 20 mph and slowing down by the time I get here.

I put it in the shop and check everything. Pull all the cables and clean and check each one. Found a loose threaded post on one of the batterys. So I got a clamp on threaded post (as the batteries have both threaded and regular posts. I charge it up and take it for a run this time full on and checking it again. This time I get 6.2 mile on it before it starts to slow down.

I checked the batteries after charging all night and they were reading with in 12.75 and 12.98. I forgot to check before I plugged it back in but I will check to see what they are falling to. I know the volt gauge in the car under load was dropping down to about 65 volt.

Shouldn't I be getting more miles out of a charge than that?

I am charging the batteries now and will run a load check on them when they are charged. Take it for a drive and then read voltage again.

Congrats on the purchase!

Have you asked them about this? Might be worth a phone call.

Not if the batteries are tired!

FYI, the most important instrument in the ForkenSwift is the LED battery gauge. Being able to monitor each battery at a glance in real time (under varying load conditions) is invaluable for protecting the weakest ones from damage by drawing the voltage too low under load.

... And for learning what kind of range they'll deliver (before voltage sags too much to continue "normal" use).

You could do the same thing with a bunch of multimeters.

http://www.youtube.com/watch?v=cHlq1J5dbb4

The previous owner's estimate of 15 miles is probably valid for new batteries under good conditions (warm day, 40 MPH, no hills, etc.)

If the car hasn't been used for several months, it is possible that the batteries may 'wake up' some with use. Try a few 2 or 3 mile drives, keeping amps below 200 or so. The range may increase some within about 10 cycles.

If the batteries are not new, they will have less range. You can check the date code to see when they were manufactured. If the batteries were well maintained, but just old, you can expect about 1/2 the range of new batteries after 3 or 4 years.

If the batteries are less than three years old, they may have been abused by the previous owner. This includes driving until the vehicle moves slowly. Each 100% discharge is like giving the pack a heart attack - it may survive a few, but not many, and will have somewhat decreased range after even one 100% discharge. No-Name and off-brand batteries are generally more sensitive to deep discharges.

Other ways to inadvertently abuse a pack:
- not charging a discharged pack immediately
- undercharging the pack (your 72 volt flooded pack voltage just before the charger turns off should be just over 90 volts)
- overcharging the pack (i.e. daily/weekly equalizing, or a bad battery charger, or floating at gassing voltages)
-leaving the vehicle off charge for more than a couple of weeks or so, particularly in cold weather.

If the pack is more than about four years old, the range you're getting is expected - time to get new batteries!

It doesn't sound like your connections were loose enough to cause a major problem. If a battery connection is loose enough to affect range, it will get very hot, and may melt a post.

Are the brakes overadjusted? Any amount of dragging will decrease range. If the car hasn't been used in a while, the brakes may be a bit sticky. Check for a wheel that is warmer than the others after a drive.

A 72v Geo Metro, now that's familiar...:p That's the problem with someone else's car- too many questions. Your pack is only as good as your weakest cell, so it might just be one cell causing you problems. And I can only guess at what my range is since I've never gone further than 6 miles on a charge, but I would estimate mine is about 15 miles so that's what I would tell someone if they asked about my car. What kind of charger do you have? I'm pretty convinced that some batteries die prematurely when they are charged together from a multi battery charger- but that's just my personal opinion. I would definately take a bunch of voltage readings before and after charging of every single battery. And personally, if it were my car I would charge each battery individually with a 12v charger and see how each battery behaves individually. Then, when you get more familiar with them, you could switch to a multi-battery charger. Good luck, and I know from experience that you have a great car on your hands. The Geo Metro seems an ideal choice for a conversion.

Thanks I saw the meter your using and am thinking that would be a great way to go. I will order the parts this week some time. I know the 4 batteries in the back are new. interstate The ones up front are different and I don't see any lables on them. I will have to check them all out as I have not done that yet. I figured load test. I have a carbon pile tester and hydrometer. I will let you know the results.

I've found the best load test is to actually drive the car while monitoring individual battery voltage.

Tom raises a good point: if the batteries have been sitting for a while, it may take a number of charge/discharge cycles to revive them.

Keep us posted!

Yea I know the car sat for a while and I figured the first few runs that I could not expect full range. But like I said I figured 6 mile would not be too much for it. Of course it could be my driving style as I have not learned to drive this car yet.

The charger I have is an zivan NG1 The controler is an Alltrex AXE The motor I can't see the MFG (its covered by the motor mount) But the info I did get off of it is that its 36 volt and 15 hp cont. Seems to do just fine.

I will be checking cells tonight with the hydrometer when I get home I charged it last night I did think about charging each battery individually but have not tried that yet.

I am working on a Geo Metro Convertible Conversion, so I read the thread with interest.

I have all of the components in house (garage actually) except the batteries.

Warp-8 Motor
Gen-2 Kelly 600A 24-144V controller
Brake vacuum pump
Emergency Disconnect
Primary & Secondary Contactors
Lots of 2/0 Wire & 2/0 crimper
Throttle Pot Box
120V Heater Box (may not install it as it is already only a 3-season car)
HV Cycle Analyst Monitor
Lots of other bits...

I was planning to do the conversion last fall, but the economy tanked that idea, so it is still running with it's 3-hampster ICE.

I am planning on 120-144V system to keep currents down, and allow a decent highway speed... So again I was reading "72V" with interest...

I also was planning Lithium...Probably 100A-TS which will give me a decent range, and last a while...but Expensive...
Again, I am looking at that 72V and wondering if I could go with a 96V system, but 150A-TS's...

If you are only pulling ~200A, that is only 2C on a 100Ah-TS, or less than that from a 150Ah pack... so please post more about what you are seeing and you experiences running at that voltage...

I agree with charging each battery with a 12v charger to get the pack balanced.
I have a paktrakr gauge that works the same way to tell you how each battery is doing compared to all of the other batteries, it also works as a volt meter and you can get an amp meter hook up, it's really one of the best meters I've ever seen for the meter, it also gives you a fuel gauge style meter, a warning if you over charge or over discharge any or all of your batteries.
Also after you drive the car a few miles feel each connection on the motor, controller and batteries and see if any are warm.
Also jack up each wheel and spin it around to see how they spin.
I suspect that your batteries are about as small as you can get away with, so as they age they are going to get more and more unhappy with heavy use.

Ok here is some more information. 4 batteries in the back are interstate srm-27 the two up front are actavator dc-27. The two batteries up front are sealed units that have the little window for checking green is good Black is bad. both are green and were reading 13.26v and 13.20v after the load test, 15 second 300 amp draw. Both kept climbing after the test. So the difference could be that I checked voltage on one quicker after the test than the other one. All the batteries in the back were also load tested and checked with the hydrometer. hydrometer check read 1250 on all the cells in the interstates. And they were reading 12.98 before the load test. After load test the interstates were reading 12.81

After all that I took it out for a road test. Headed toward town (slight up hill grade) tried to keep it in the 200 amp range. Turned around and headed back. total of 3.3 miles Then checked the voltages again.

front two read 12.92 and 12.91 back four read 12.81 12.82 12.82 12.81 volts.

I cheched all the connections even the motor and no warm spots on this run. I will check the wheels and see if any are dragging. I don't feel any drag while coasting. But will check with wheels off the ground.

Thanks for all the help