under-load voltage abnormally low (1.61v per cell)

[sportcoupe]

Originally Posted by JohnnieB

Do you would happen to know what the ages of the specific batteries are?
Or at least which ones are older and which are newer.

Batteries 5 and 6 are 2013, the rest are 2011. All are the same model number.

Batteries 5 and 6 are also the ones that dropped in voltage after the new charge algorithm was used.

[JohnnieB]

Originally Posted by sportcoupe

Batteries 5 and 6 are 2013, the rest are 2011. All are the same model number.

Batteries 5 and 6 are also the ones that dropped in voltage after the new charge algorithm was used.

Birds of a feather...

Am I correct, Battery 5 & 6 have always been charged as part of the 72V pack?

Any idea how the other seven were previously charged. 56V Pack?
5 & 6 are evenly matched
1, 2, 3, 4, 7 & 9 are fairly evenly matched.
8 is the odball.

Without #8, your pack is charging to 93%, but # 8 has shown considerable improvement (78% to 84%) and it may improve some more.

Give the pack a couple weeks of repeated charging and see what the numbers are. They should continue to improve.

Of course, I doubt if #8 will ever come up to the same level as the other 2011 batteries, but stranger things have happened.

[sportcoupe]

The whole pack was 72v from the start in 2011. Batts 5 and 6 were replaced in 2013 due to damage when the cart rolled over on it's side riding some trails at CAW. I didn't own the cart at the time, it was member Andy's cart. He types in red letters.

[Cart-Buddy]

Originally Posted by JohnnieB

A belated welcome to BGW!
Glad to have someone with prior battery knowledge/experience on-board.

What battery chemistry, type and voltage for the 0.2V tolerance?

The difference in the At-Rest voltage given in Post #1 is 0.21V and they are 8V, 121AH, Lead-Acid, Wet-Cell, Deep-Cycle batteries made by US Battery company, that have apparently never been fully charged, and a dV/dT type charger is being used and it is now set to the correct charging algorithm, so they might equalize. At least they are likely to get closer together in voltage unless they've been irreversibly damaged

It definitely would be better to give #8 and any of the other lower voltage ones some individual charging, but 8V chargers aren't all that common.

I had prior knowledge of Gel-Cel, MiCd, NiMh, early Li-ion and other relatively new technologies, but the old-school FLA (Flooded Lead Acid) deep-cycle technology used in golf carts was overlooked territory for me.

They are far more tolerant of typical abuse and far more forgiving than the later stuff.

My cart batteries would only charge to 85% when I got my cart, but they were up to almost 100% when I upgraded to a 42V system. All I did was charge the living daylights out of them and added distilled water as needed.

As said earlier, welcome aboard and Semper Fi. (USAF 63-75)

Thanks for the welcome all the batteries we dealt with would show the internal resistance problem, they were primarily flooded cell lead-antimony or lead-calcium (usually Exide). We also dealt with AGM's in the form of Hawker's (Enersys) and Optima's. We also saw it if the troops had mixed calcium and antimony or AGM's with flooded cell.
Almost all the military systems are 24V though some are in series parallel and other in parallel series.

Their primary is the 6T battery it is a combination deep cycle-SLI. The size is unique to the military though they compare in mass to a healthy Grp-31.

"Charging the living daylights out of them" is one way to get the large crystal PbSO4 to break down. You can also do it with temperature regulated constant current higher voltage charging or with pulsing.\

I'll be around off and on and help if I can until I get one of my projects going then I'll ask for help

SF,

Mark

[JohnnieB]

Originally Posted by sportcoupe

The whole pack was 72v from the start in 2011. Batts 5 and 6 were replaced in 2013 due to damage when the cart rolled over on it's side riding some trails at CAW. I didn't own the cart at the time, it was member Andy's cart. He types in red letters.

If the Delta-Q charger came with the cart, it means Andy never set it to the correct charge algorithm for US Battery batteries.

I guess it was a good thing he never drove it with a fully charged battery pack, or he might have launched in into low Earth orbit instead of just rolling it.

However, I'll cut him some slack. The undercharging issues with US Battery batteries was not well know in 2011. The attached Technical Service Bulletin is dated Sep-2012.

A key statement in that document is "Testing has shown that the batteries are simply undercharged and usually recover capacity when charged properly."

So there is hope for all, except for #8 possibly.

It may have sustained some latent physical injuries in the rollover, or might have leaked some electrolyte where it was on its side or upside-down.
If it did lose some electrolyte and was topped up with distilled water, the acid concentration is lower than it should be.
If so, this would be one of those rare situations when something other than distilled water should be added to a battery, but I don't know where to get diluted electrolyte that has a high enough SG to work in a US Battery and handling pure H2SO4 is too dangerous for most of us to use.

[JohnnieB]

Originally Posted by Cart-Buddy

Thanks for the welcome all the batteries we dealt with would show the internal resistance problem, they were primarily flooded cell lead-antimony or lead-calcium (usually Exide). We also dealt with AGM's in the form of Hawker's (Enersys) and Optima's. We also saw it if the troops had mixed calcium and antimony or AGM's with flooded cell.
Almost all the military systems are 24V though some are in series parallel and other in parallel series.

Their primary is the 6T battery it is a combination deep cycle-SLI. The size is unique to the military though they compare in mass to a healthy Grp-31.

"Charging the living daylights out of them" is one way to get the large crystal PbSO4 to break down. You can also do it with temperature regulated constant current higher voltage charging or with pulsing.\

I'll be around off and on and help if I can until I get one of my projects going then I'll ask for help

SF,
Mark

Glad to hear you are familiar with Exide batteries, I've got seven of their GC-145 batteries in my 42V pack and I might be picking your brain some in the future.

Historically, golf cart chargers used a Ferroresonant Transformer design based on the recommended charge profile for Trojan batteries and had a control board that terminated the charge when the On-Charge voltage reached about 2.5VPC. That wouldn't "overcharge" most batteries after they got the normal PbSO4 buildup on the plates through aging, but it doesn't fully charge most batteries and some other brands require a higher finish voltage. So charging the living daylights out of most battery packs will improve their performance some.

However, there are also a lot of charger out there that use more sophisticated technologies.

I've got a question you may have an answer for. A forum member has a set of Super-Start GC110DT batteries (6V 230AH - made by east Penn) and is using a Save-a-Battery charger to charge themhttp://shop.saveabattery.com/48-VOLT...se-2365-48.htm. It is a low amp pulse charger and the batteries have a very high At-Rest voltage (30% higher than normal), but I cannot figure out why.
Here is the thread: http://www.buggiesgonewild.com/elect...-johnnieb.html

Can you shed any light on the subject?

[sportcoupe]

Battery #8 has came up more to 8.39 so we are making more improvements. Still that is no guarantee that it will hold voltage under load correct?

I don't have an 8v charger. Can I help #8 along some with a 12v charger for a short time? If that's not advisable maybe I can bypass it altogether in the pack. That would downgrade pack from 72v to 64v. I would ride the cart till the others are below #8's value then connect it back for the 72v charge.

If #8 lost too much acid mix in Andy's flip and too much water was added how would I ever know that? The local auto parts store has battery acid. I believe it is a mix though, not sure. I know Ace hardware has pure acid. Bad stuff as I've used it on another FLA battery experiment. It's amazing how much heat is created when acid is mixed with distilled water for the first time.

[JohnnieB]

Originally Posted by sportcoupe

1. Battery #8 has came up more to 8.39 so we are making more improvements. Still that is no guarantee that it will hold voltage under load correct?

2. I don't have an 8v charger. Can I help #8 along some with a 12v charger for a short time?

3. If that's not advisable maybe I can bypass it altogether in the pack. That would downgrade pack from 72v to 64v. I would ride the cart till the others are below #8's value then connect it back for the 72v charge.

4. If #8 lost too much acid mix in Andy's flip and too much water was added how would I ever know that?

5. The local auto parts store has battery acid. I believe it is a mix though, not sure. I know Ace hardware has pure acid. Bad stuff as I've used it on another FLA battery experiment. It's amazing how much heat is created when acid is mixed with distilled water for the first time.

1. You are correct, it might eventually charge all the way to 100%, but still fail under load.

2. Put an 1156 (or similar) 12V bulb in series with it. That will limit the current to about 2A.

Also, if you are feeling adventuresome, you might try something like this: http://www.alpharubicon.com/elect/3dollarbattggn.htm
Of course, you'd have to be very careful.

3. That is another way of doing it. Getting all the batteries at about the same voltage would give them the opportunity for an equal charge when charged in series.

4. You couldn't know after the fact. If #8 doesn't come up to par by other means, adding acid is the last resort.

5. The exothermic reaction can get pretty violent.
Always pour the concentrated acid into water. Otherwise it will spray acid all over the place.
It gets a little tricky mixing a highly concentrate acid with a less concentrated acid, but it can be done. Small amounts of the concentrated acid into the less concentrated acid, very slowly. Full face and skin protection is a must.

[sportcoupe]

Min/Max DVM arrived today, pretty loaded with features for only $36 shipped.

http://www.ebay.com/itm/120881994937...937%26_rdc%3D1

[sportcoupe]

Things seem to be improving. Since I got my new test toy (min/max DVM), and I had some time I decided to take some measurements. I started with a fully charged pack more then 12 hours off the charger (75.9v). Here are new under-load voltages only as measured with new meter. BTW, it's so much easier with a min/max then trying to watch meter on a full throttle launch AND actually see the lowest value AND not crash.

1. 6.56
2. 5.87
3. 6.20
4. 6.10
5. 5.84
6. 5.50
7. 6.66
8. 6.09
9. 6.56

Carts back on the charger so tomorrow I can see if I can ride more then 2 miles before it's under-load voltage drops below 1.75 per cell.

One more thing. Cart is now lifting the front tires off the ground on each of my full throttle launches from a dead stop.