New batteries

[JohnnieB]

Originally Posted by dahur

I put in my new Trojans in June this year. After I charge them up, it takes about three days to get down to 38.2 if I don't use it.

The charts put out by Trojan and other battery manufacturers are averages based on testing of dozens of mature batteries.
New batteries will typically be off the top of the charts. As they age they will line up with the top of the chart closer and as they get older, they may be slightly less than the top of the chart.

Lead-Acid batteries are very forgiving, so the voltages for everything less than 100% SoC is close enough for all but the most exacting scientific studies.

[TreeBass]

Originally Posted by JohnnieB

I watched the NASCAR race and fell asleep in my recliner afterwards.

Appears that you are getting closer to getting your new batteries fully charged.

Are you running the charger with the relay by-passed, or did just cleaning up the connections get the charger staying on longer?

I think cleaning it did the trick!! Funny thing is, I cleaned it up before hand, but after you said something, I took a drill and wire brush to the connectors just to be sure!!

I think we have success, this morning the charger was off, and pack voltage was 38.7

I wont be able to get a 12 hour reading, but will check it when I get home this evening.

Thanks Johnnie, appreciate the help

[JohnnieB]

Glad to hear a little "housekeeping" took care of the problem.

[TreeBass]

If I get back up to West "by God" Virginia anytime soon, I'll have to buy you a beverage of your choice.

I'm due a trip to Keyser, its been awhile

[TreeBass]

After 12+ hours

Pack = 38.0

1) 6.32
2) 6.32
3) 6.37
4) 6.34
5) 6.32
6) 6.33

Been reading about batteries and charging most of the day, and came across a post from Johnnie about "bleed off" or something like that. So I tested each battery post where the wires connect with another battery and found leakage between batt 4&5-.03-.10

So this would indicate a bad cable, correct? And if so, is that much bleed off normal, or do I have something else draining my pack voltage?

[TreeBass]

37.9 this morning after sitting for 24 hours

[JohnnieB]

Those voltages are still a bit low, especially for new batteries.

If they were mine, I'd bypass the relay in the charger so it doesn't shut off and let the pack charge for about 24 hours. Then measure the voltages about 12 hours later.

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While on charge, the pack voltage gets up to about 45V and will start dropping as soon as the charger shuts off. The higher voltage is called a surface charge and isn't an accurate indicator of the battery's State of Charge, so you have to let the batteries sit for several hours for it to deplete.

After the surface charge is depleted (about 12 hours) the batteries continue to self-discharge, but at a slower rate of about 1% SoC per day. Some battery types/brands self-discharge at slower rates, other at faster rates.

Most carts have a "Pre-Charge" resistor connected between the large terminals on the solenoid that keeps the filter capacitors in the controller charged, which in turn, reduces the arcing on the solenoid contacts when they close. With the resister installed, they is always some current flow, which increases the "Self-Discharge" rate.

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Ideally, the high current cables have no resistance, but in reality the do have a slight amount. (IE: 0.0002485 Ohms per foot for 4Ga cable)

The higher the current flow through the cables, the higher the voltage measured across them will be, but for the short interconnecting cables between the batteries (each about a foot long) it should only be about 0.005V when the charger is putting out 20A and about 0.02V when the cart is cruising at top speed and drawing about 75A.

If a cable is dropping 0.03V to 0.1V while not being driven or charged, either the cable or its connections are bad.

Cables and connections with excessive resistance heat up when amps flow through them, so any cables or connections that get warmer than about 10°F above ambient air temperature need to be fixed or replaced.

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Parasitic drains are relatively easy to find, but checking for their existence is a royal pain.

The first step is to find out what the battery pack Self-Discharge rate is.
Remove the B+ and B- cables to the controller and any wires from the battery pack to any accessories. That would leave only the five interconnecting cables and the two wires from the charger receptacle connected.

Charge the battery, measure the pack voltage at 12 hours and at 36 hours.
The amount of voltage decrease during the 24 hours between the 12 hour and 36hour measurements will give you the self discharge rate for your batteries.

The reconnect the accessories, but don't turn any of them on, wait a few hours and measure the voltage. If the discharge rate is higher, something is drawing current when it shouldn't be.

Then reconnect the controller, wait a few hours and check the voltage. The controller will draw some current due to the Pre-Charge resistor.

[TreeBass]

Originally Posted by JohnnieB

Those voltages are still a bit low, especially for new batteries.

If they were mine, I'd bypass the relay in the charger so it doesn't shut off and let the pack charge for about 24 hours. Then measure the voltages about 12 hours later.

So we still suspect the charger? How do I do bypass the relay?

thanks

[JohnnieB]

Originally Posted by TreeBass

37.9 this morning after sitting for 24 hours

Went from 38.0 (95% SoC) at 12 hours down to 37.9V (91% SoC) at 24 hours. That is a discharge rate of 8% per day, which is mighty high.

You've got a parasitic drain of some kind. That may be while the battery voltages are lower than normal.


When the cart is turned off, what is the voltage drop across the resistor between the solenoids two large posts?
Also, what is the Ohm value marked on the resistor.

Is there any dirt/debris on the top of the controller? (Might be a conductive path between B+ and B- terminals)

[JohnnieB]

Originally Posted by TreeBass

So we still suspect the charger? How do I do bypass the relay?

thanks

I was suspecting a charging until I found out that the batteries were discharging at 8% per day. Now I'm not so sure, the battery and charger might be fine.

However, here is how to bypass the relay. The control board show isn't the one in your charger, but the relay looks about the same. Just connect the AC wire going into it and the AC wire coning out of it together and the charger won't shut off. (If the timer in yours is working, it may time out at about 12 hours, if so just restart it and let it run for another 12 hours.)