I'm afraid new batteries are in my future.....

[ncrr]

Over the past couple of months, it seems that my batteries are slowly declining. All 6 batteries are trojan #605's with a datecode of "G3". I'm not aware of how that converts to date. When charging, the charger cuts off at about 43.6, and after sitting the voltage is 37.0/37.2. Somehow that does not look like a good sign. Many times when out, 3/4 mile or so, on the way home the battery voltage goes into the 34v range when going up a slight rise in the road. We are not running fast, but are running at a steady pace.

These batteries were in the cart when purchased, so I have no idea of their earlier maintenance. I check water levels frequently, never been below since I've had the cart.

What would be the best way to determine for sure that the pack is ready for a replacement?

Thanks.....
Henri

[JohnnieB]

First, a T-605 is an economy grade battery (210AH - vs the standard 225AH), so it won't have as long of a cradle to grave lifespan as standard AH batteries.

Letter is the month and number is year, so G3 = July, 2013 and your batteries are going on 4 years old, which falls within the typical useful lifespan for cart batteries in warmer climates.

They are only being charged to about 70% SoC (37.12V = 70% SoC), which might be due to the charging process since the charger is cutting off at 43.6V. The charger type I suspect you have (Powerwise 28115), normally shuts off in the 44V to 46V range and the charger is shutting off, so there may be some excessive resistance in the cart's charge receptacle or the wires and fuse that connect it to the battery pack's main terminals. Try cleaning those connections up and your batteries might start being charged more fully.

Also try doing a few back-to-back charges. Sometimes doing that perks up tired batteries.

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As for determining for sure when the batteries need to be replaced. When the cart's performance and/or range is unacceptable.

The pack is only dropping to 34v under load when only about 70% charged, so I don't thick you have a bad battery or cell, but you can measure the individual battery voltages while going up the same hill (six times) to see if any are dropping significantly more than the others.

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Considering you have 22" tires, a rear seat and 12V accessories power via a DC-DC converter, it is most likely time to replace those undersized batteries.

This would also be a good time to upgrade to 42V. Looks like all you'll need is buying seven 6V batteries rather than six, one 2Ga cable and a 42V battery charger. (DPI Accusense charger is the best bang for the buck)

[ncrr]

thanks, As usual, great stuff JohnnieB..

Correct on the charger... I have burnished up all the connections. I did notice while charging, that the 2 wires from the charge receptacle to the batteries get warm, not hot but noticeably warm. Shoukd I dismantle the Charge receptacle and polish-up the stuff in there too?? i think if I do that, I will 'up' the 2 wires at the same time, cannot hurt...

Yes, toying with the kickup to 42 or 48. I looks like, unless i read the charts incorrectly, 48 is better with 8 volters as opposed to 12's. but with my stock motor, I'm guessing 48 would be the killer for that motor. Going with 42, probably makes more sense (i usually come up short there....), and there is space under the drivers seat for the extra. But 4 12's sound good for less weight... oh well...

I will take the advice and do several back-to-backs, best to run them down a bit first?

I see you use the Exide GC-145, presume you are happy with that setup. in either case I'm into a new charger.... Actually wish there was good space inside the cart to put the charger, thought about the bag well, but it can get wet in there.... Any thoughts on that?

OK, thanks for your input.....
henri

[JohnnieB]

Originally Posted by ncrr

thanks, As usual, great stuff JohnnieB..

1. Correct on the charger... I have burnished up all the connections. I did notice while charging, that the 2 wires from the charge receptacle to the batteries get warm, not hot but noticeably warm. Shoukd I dismantle the Charge receptacle and polish-up the stuff in there too?? i think if I do that, I will 'up' the 2 wires at the same time, cannot hurt...

2. Yes, toying with the kickup to 42 or 48. I looks like, unless i read the charts incorrectly, 48 is better with 8 volters as opposed to 12's. but with my stock motor, I'm guessing 48 would be the killer for that motor. Going with 42, probably makes more sense (i usually come up short there....), and there is space under the drivers seat for the extra. But 4 12's sound good for less weight... oh well...

3. I will take the advice and do several back-to-backs, best to run them down a bit first?

4. I see you use the Exide GC-145, presume you are happy with that setup. in either case I'm into a new charger.... Actually wish there was good space inside the cart to put the charger, thought about the bag well, but it can get wet in there.... Any thoughts on that?

OK, thanks for your input.....
henri

1. The wires between the charge receptacle and main terminals of the battery pack getting warm is part of the batteries not getting fully charged problem. The control board shuts off the charger when it sees about 45V between the red and black wires that connect to the control board. If you trace those two wires, the red one connects to the heat sink inside the charge and the black one connects the the auxiliary contact in the D-plug. which touches the outside of the negative radsock in the cart's charge receptacle. The resistance in every wire, connection or contact (and fuse) in the series loop between control board's red and black wires reduces what portion of the 45V is actually being applied to the six batteries themselves.

Personally, I'd use 8Ga wire from receptacle to batteries and eliminate the fuse, unless you have kids or anyone else that might touch a conductive object to the two exposed terminal in the charge port.

2. A stock 36V PDS motor plays well at 48V. It is Amps rather than volts that kills it. You have a 400A XCT, so your motor will be okay at either 42V or 48V.

I wouldn't wish a 4 X 12V battery pack on my worst enemy since it has about 15% less range and about 15% shorter usable lifespan than a standard 36V battery pack.

A 48V pack made up of 8V-170AH batteries has the same range and lifespan as a standard 36V (6 X 6V-225AH) battery pack. For more range and lifespan, use higher (IE: 190AH or 204AH) Amp-Hour 8V batteries.

To get even longer range and lifespan use a 42V (7 X 6V) pack.

Attached is a chart comparing various batteries in 36V, 42V and 48V configurations. The closer to the top, the longer the range and lifespan.

A 36V pds cart upgraded with an XCT controller and a 42V battery pack is a match made in heaven.

With stock height or smaller tires, that combination will spin the motor beyond the max recommended RPM for a stock PDS motor (~6500RPM) or about 28MPH. With 22" tire, the motor probably won't reach that RPM, but the speed ought to be that speed or faster. However, I suspect you have low pressure tires (<10PSI max inflation pressure) since your top speed is only 22MPH with 22" tall tires. (Mathematically, it would be about 29 MPH at 36V and 22" tires)

A 48V pack will give you more torque, so your cart will be quicker off the line, but top speed will be roughly the same due to the max RPM limit of the motor.

3. Not necessary to discharge them at all, but okay if you do. Plug the charger in at night, then unplug it from the cart the next morning and plug back into cart a few moments later. The charger will come on and put out max amps (~20A) for several minutes, then taper off and the on-charge voltage will climb to 45V, shutting off the charger in an hour or so, maybe longer. Use cart as you normally do and if practical, initiate a charge or two during the day. After a week or so, let the batteries rest for 12 hours and check the voltage to see what the SOC the batteries are charging to.

4. Using 6V-245AH batteries gave me the 30+ mile range I was looking for, but the situation changed and I no longer need a 30+ mile range. Other than that I am very happy with it. If I had to do it over again and knowing the local ordinances would change to restrict golf carts on some of the roads I was planning to use, I would have bought seven lower AH (less expensive) 6V batteries. At 42V and with my 17" tall turf tires, I had to play with the throttle rate, linearity, speed and torque curves to keep from spinning the tires.

AS for chargers. If you need to have an on-board charger, get one designed to tolerate the rough ride and weather it will be subjected to, which will cost more than a stand-alone charger.

For on-board I'd go with: http://quickcharge.com/
For stand-alone: http://www.cartsunlimited.net/chargers-36-48v.html

[ncrr]

Thanks JohnnieB.... much appreciated...
I will open the charger, and burnish those connections and will convert over to the 8GA wires. I'll keep you posted.....
Henri

[ncrr]

Ok JohnnyB, I have FINALLY completed all the steps you suggested. Cleaned connections, replaced wires from the plug to the bats with 8ga (it no longer gets warm at all). After many repeated charges, The bank voltage has gone from 37.2 to 37.4 (after overnight rest), so I think the deal is done - new batteries....

All the batteries show a voltage of about 5.9 each, with one toggling to 5.8 every now and then. Which is kinda weird since that totals out to 34.4. guess it's time to get out the big DVM to see it it agrees..... weird!
Thanks for your suggestions....

[JohnnieB]

6 x 5.9 = 35.4 rather than 34.4.

That is still about 3.0V less than the total pack voltage.

With a pack voltage of 37.4, each battery should be about 6.2V, so something is strange.

A max of about 0.6V can be attributed to rounding errors and 6V is likely being measured on a different voltage range than the 36V pack, so some more can be attributed to that, but 3.0V is stretching those possibilities.

Maybe the battery in the DVM is low.

[ncrr]

the weirdness continues...
Hand Dash
DVM DVM

Bank 37.3 37.4
1 6.26 5.9
2 6.23 5.8
3 6.23 5.8
4 6.26 5.8
5 6.25 5.8
6 6.26 5.9
==== ====
37.49 35.0

all of the wires to the dash go the same route; battery pair thru DP8T switch to the dash mounted DVM. So if its wire/switch resistance, why would the bank totals be correct, and the individual battery numbers be that far off ~.26v ....

but the voltages are what you expected to see on the hand dvm....

[JohnnieB]

If you can reach the input terminals of the dash mounted DVM with the test leads of the handheld DVM, you can determine if the error is being caused by the rotary switch and wiring, or the dash DVM is the problem source.

Basically, piggyback the handheld DVM on the Dash mounted DVM and switch through the different batteries and total. If the two meters agree, the problem is in the wiring, if they don't read identical voltages (or nearly identical) the meter has some low end accuracy issues.

[ncrr]

I'll try that, but I think it's the dash dvm. Reason being is that the Bank voltage goes thru the same switch, on position #8, and it reads correctly, and ALL the low voltage ones are off by about the same amount, go thru the same switch, just different positions #1-#6. To me it seems if it was wiring/switch related, the Bank voltage would also be off..

Am I nuts?????