84 Marathon resistor cart project

[scottyb]

John89, Welcome to BGW!

This is some serious thread hijacking you are trying to pull off here in rlw's thread.
This is considered bad manners in the internet forum world which I understand you are just learning about. That's cool we all posted our 1st post on bgw

So go find the Ezgo electric section and hit 'new thread' instead of reply. We will see you there in your own thread.

[rlw]

@Johnnie,

Thanks for the tip about PDFs. Here's my spreadsheet. As you can see, the Crown batteries are the worst - 6.08V and 6.13V are the best I could get out of 'em after charging.

Looks like one Trojan and the Powervolt are the best - 6.41V and 6.40V after a full charge. The other two Trojans top off at 6.33V and 6.24V.

As to getting NEW batteries, turns out there's a guy about 3 miles west of me who reconditions and sells used cart batteries for about $50 each. I'm thinking of heading out there with a V-O-M and seeing what he has to offer. They can't be any worse than the Crowns are.

I beat my head against a bad APC UPS and a bad Linksys router at a customer's all day today. That got me to thinkin' about hooking up the Crowns in series to an old APC UPS I have. It seems to me that the charger in that device does some conditioning to keep the gel cells up. I wonder if it would do a good job on cart batteries. There's my mad scientist experiment!

Just a thought...

RLW

[JohnnieB]

Originally Posted by rlw

...................I beat my head against a bad APC UPS and a bad Linksys router at a customer's all day today. That got me to thinkin' about hooking up the Crowns in series to an old APC UPS I have. It seems to me that the charger in that device does some conditioning to keep the gel cells up. I wonder if it would do a good job on cart batteries. There's my mad scientist experiment...............

Good Grief another Geek AND Numbers Nerd. I was beginning to think I was the only one of that breed around here...

Your mad scientist experiment is roughly the same as the one I suggested, put them in the gassing phase and leave them there for an extended period of time.

Using an old UPS might work, but the low power units APC builds have Gel-Cells. You have to get above 3KW before they use wet cells, and even then they use Sealed wet cells, which has nearly the same charge profile as Gel-Cells, so based on a 12V battery, the "Float" voltage is going to be about 2.0V less that the "Equalize" voltage needed.

If the APC UPS sensed the pair of 6V wet cells as being discharged, it would try to charge them up to about 14.4V (2.4V per cell) and then float them at about 13.8V (2.3V per cell). To "Equalize" them, we've got to get them into the 2.6V to 2.8V per cell range and let them cook until there is no longer any increases in the Specific Gravity of the electrolyte between measurements taken an hour apart while on charge.

Here are some links to some battery info you might find interesting.
http://www.trojanbattery.com/pdf/TRJ...dSpecGuide.pdf
http://www.trojanbattery.com/Battery...ngStarted.html (Read all the "Related Links" in the menu of the right side of page)
http://www.trojanbattery.com/pdf/TRJ...dSpecGuide.pdf

BTW - You might find some halfway decent used batteries at the place you mentioned, not all trade-ins are bad.

[rlw]

Originally Posted by JohnnieB

Good Grief another Geek AND Numbers Nerd. I was beginning to think I was the only one of that breed around here...

It's the West-By-God-Virginia-October-Skies-Rocket-Boys syndrome. I grew up with a power-company-engineer dad, and an older brother who tried to build a cyclotron - he and his buddies got about 1/3 of the way through it, then, one-by-one, got drafted for the war. I started out building crystal sets (OK, diode, 365pF variable cap, coil, earphones, Fahnstock clips, fer gawd's sake) at the tender age of 6 or 7. I come by it honestly.

I'd already downloaded the Trojan PDFs. I'll need to re-read 'em again before I start this. Wish I had my dad's old HP recording DC voltmeter - it'd be a good way to chart what's happening.

I have a pile of old APC (and other) UPSs in the basement. Most of them work, just have bad gel-cells in 'em. I think the beefiest one is a 1.5kVA jobbie. I'll use that one for my experiments. I might try to find a copy of Powerchute Pro - there's alot of information about the batteries that gets logged, stuff not captured by the Powerchute lite software.

I'll probably try my hand at de-sulphating the Crowns first. Been reading lots of voodoo-mumbo-jumbo about using epsom salts or ED?? something to break up the gunk. Found a link to a $3.00 pulse charger made out of a light bulb and a 1A 200V diode. I've got a couple of 20 gallon HDPE lidded buckets - thought I'd put the batteries in there (with the lid just sitting to catch H2SO4 splashes) so I don't have to get a full face mask and Intel bunny suit. I won't put the lid on tight so the hydrogen can vent - don't want to build an H-bomb in my basement!

If I kill the Crowns, they're still worth the core charge ($15 each around here), so other than possibly blowing up the house, what have I got to lose?

We'll see. Maybe the guy 3 miles west will want the Crowns for the cores and I'll just buy 2 $50 batteries - probably easier, but I won't learn anything.

RLW

[JohnnieB]

I took a look at your spreadsheet.

Probably the best indicators are the 11/13 entry (12 hr charge - 5 hr rest) along with the 11/14 entry showing self discharge rates since batteries had not been used or charged for about 30 hrs.

Here's what it tells me.

1 & 6 = Full charge - Okay, but Self discharge rate seems a bit high. Need to be load tested.
2 & 4 = 80% & 90% Charge respectfully - might improve, but probably needs to be replaced.
3 & 5 = 50% & 60% respectfully - Needs to be replaced.

IIRC: You've got a manual charger with a timer. What I would do, is put the batteries on charge and leave them on charge until the highest individual 6V battery voltage reached 7.3 - 7.4V. That would correspond to the pack voltage of 44V - 46V that an automatic charger shuts off at.

If you have a 12V car battery charger, you could also charge them in the closer matched pairs (1&6 - 2&4 - 3&5) until they reached 14.6V - 15.3V.
Then charge the daylights out them with your 36V charger.

FWIW:
My 2008 PDS cart came with six T-105 batteries, all date coded 11/09 (L9 stamped into Negative terminal) and the electrolyte was above plates in all cells.
The pack would only charge to 85%, and the extreme voltage spread between batteries was about 0.1V. (at least a 12 hr rest)
After some fun and games, the pack now charges to 95% and the extreme voltage spread is only 0.04V. (at least a 12 hr rest)

What I did was basically, charge the daylights out of them. I put them on charge every night whether or not I had used the cart.
Some times I would restart the charger two or three times in one day even though the cart never moved an inch.
Granted, I used up some Discharge/Recharge cycles, but I ended up with a more useable battery pack, which was my goal.

My plan is to replace the pack next spring and re-purpose the old one for task lighting during power outages. (Series charge and parallel feed to 12V bulbs via 10 ga twisted pairs.)

[JohnnieB]

Originally Posted by rlw

..............It's the West-By-God-Virginia-October-Skies-Rocket-Boys syndrome............

.........Been reading lots of voodoo-mumbo-jumbo about using epsom salts or ED?? something to break up the gunk..........

...........Found a link to a $3.00 pulse charger made out of a light bulb and a 1A 200V diode.............

On the Rocket Boys syndrome.

I think most of the battery rejuvenating "magic" out there is like you said, voodoo-mumbo-jumbo.
About the only one I'd try is dumping the old electrolyte after agitating, rinse/agitate with distilled water a few times and refill with fresh 35% H2SO4.

The light-bulb/diode charger is interesting, but inefficient. Using a 100W bulb, you're only putting 830 to 900 mA through the battery and that's only a C-250 to C-270 charge rate.
Even being pulsed, I'm not sure if that little current is going de-sulphate the plates. (The output of your current 36V charger is pulsed at 120 Hz)
However, I've got a 500W halogen portable work light and a bunch of 1N4004's so I might see what happens at 8.3A.

[rlw]

Originally Posted by JohnnieB

.........Even being pulsed, I'm not sure if that little current is going de-sulphate the plates. (The output of your current 36V charger is pulsed at 120 Hz).......

Ahhhh, so there's no big capacitor across the +/-.

When I worked on old dumb terminals, we'd occasionally have a bad power supply (pre switching PS days). It was always the big capacitor across the 5V. Since they wouldn't let US techs do board-level repairs (some bean-counter determined it was cheaper to ship the thing halfway across the country instead of replacing a $3 cap), I'd write "LUMPY VOLTS" on the return tag and send it to the depot.

[yurtle]

Originally Posted by rlw

Ahhhh, so there's no big capacitor across the +/-.

When I worked on old dumb terminals, we'd occasionally have a bad power supply (pre switching PS days). It was always the big capacitor across the 5V. Since they wouldn't let US techs do board-level repairs (some bean-counter determined it was cheaper to ship the thing halfway across the country instead of replacing a $3 cap), I'd write "LUMPY VOLTS" on the return tag and send it to the depot.

The battery pack is your capacitor!

[JohnnieB]

Originally Posted by rlw

Ahhhh, so there's no big capacitor across the +/-.

There's probably a BFC in your manual charger, but it is across the high voltage secondary of a ferroresonant transformer. The DC output is the raw voltage from a full-wave rectifier.

yurtle is right about a battery acting like a capacitor.
I got rid of a clipping problem in a el-cheapo guitar amp by splicing in a pair of small 12V Gell-Cells in series across the power supply.
IIRC, it was roughly equivalent to adding about a Farad.

[yurtle]

Originally Posted by JohnnieB

There's probably a BFC in your manual charger, but it is across the high voltage secondary of a ferroresonant transformer. The DC output is the raw voltage from a full-wave rectifier.

yurtle is right about a battery acting like a capacitor.
I got rid of a clipping problem in a el-cheapo guitar amp by splicing in a pair of small 12V Gell-Cells in series across the power supply.
IIRC, it was roughly equivalent to adding about a Farad.

I often listen to my buggy radio in the garage while it's on the charger with no buzz at all.

How did you determine the capacitance of a gell cell?