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Old 09-04-2013, 07:23 AM   #11
JohnnieB
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Default Re: Batteries lacking the power

Fortunately, Deep-Cycle Lead-Acid Wet-Cell batteries are very forgiving and you probably didn't hurt them much. You might have shortened their useful lifespan by a few days, but the lost days should be 3-5 years (or more) down the road if you take care of the right from now on.

Batteries have three sets of voltages and you have to remember which set you are looking at for them to have meaning. It sounds confusing, but if you stop and think about what is being done to the batteries or has been recently done, which set is more obvious.

* On-Charge Voltage: While on charge the voltage of a 36V battery pack will climb into the 44V-46V range, maybe a bit higher. It depends on the type charger being used and numerous other factors.

* Under-Load Voltage: When amps are being drawn from the battery, the voltage decreases. The more amps drawn, the greater the increase.
While driving your cart, the pack voltage varies by several volts depending on whether you are accelerating, cruising or coasting and if you are going uphill, downhill of are on level ground.

* At-Rest Voltage: This is the only one of the three that isn't rapidly changing and is the one used to estimate the battery's SoC (State of Charge). To reach an At-Rest state, the battery has to "Rest" (meaning neither charged nor discharged) for about 12 hours after being charged or about 30 minutes after being discharged.

Attached is a chart that lists estimated % SoC at various At-Rest Voltages.

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With little exception, your battery pack voltage will be changing all the time. It starts decreasing the instant charging ceases and it starts increasing the instant discharging ceases. Then there is the fact that this type of battery self-discharges at about 1% SoC per day.

Of course, once the battery reaches its At-Rest state, the changes are slight and gradual, so the voltage appears to stay the same for many hours unless very exacting voltmeters are used.

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It takes a while, but the fog lifts.
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Old 09-04-2013, 12:22 PM   #12
Martee48
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Default Re: Batteries lacking the power

Okay, This morning the voltage measure 38.6 with the batteries at 6.46 to 6.47.

After being out for 5 hours, played 18 plus, a few other trips, the monitoring the voltage, when it got down to 37.6, I headed to the barn for a re-charge.

All this was with the SoC Meter disconnected. I would periodically check the pack voltage when I stopped. I noticed that it is all over the place when driving, up hill, coasting, level etc. So I assuming the measurement when I stop or before I start up again would be valid to give me an idea of the battery condition.

If I get another 2 or 3 days like this, I think I can safely assume it was the SoC that was my problem. Have one on the way, my second or third upgrade.

I don't think I want to hook the old SoC Meter back up, it might have a negative effect on the batteries, maybe?!
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Old 09-04-2013, 04:35 PM   #13
JohnnieB
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Default Re: Batteries lacking the power

Quote:
Originally Posted by Martee48 View Post
...............
1. I would periodically check the pack voltage when I stopped.
2. I noticed that it is all over the place when driving, up hill, coasting, level etc.
3. So I assuming the measurement when I stop or before I start up again would be valid to give me an idea of the battery condition..................
1. That is the way to do it.

2. The way the voltage bounces around while driving will drive you crazy. (Crazier for some of us. )
However there is some useful information there. When at max load (IE: Climbing a very steep hill) you don't want to load the battery pack below 1.75VPC (Volts per Cell), which is 31.5V for a 36V pack.
That is the lowest battery manufacturers take their products during non-destructive testing.

The absolute minimum is 1.5VPC (27.0V for a 36V pack). Below that and irreversible battery damage can occur.

3. You need to let the batteries rest for a few minutes after stopping to get a ballpark SoC estimate.
Five or ten minutes is usually long enough when you are wanting to know when to head back to the barn, but if you want an accurate SoC, you need to wait a half an hour or longer.

I was doing some testing today and my 42V pack was at 42.88V about five minutes after a stopped, 43.63V after 30 minutes and at 43.73V after about 90 minutes.

--------------
Get rid of that LED Bar-graph SoC meter. Some of them lie more than politicians and it sounds like you have one of them.

Your battery pack seems to be doing okay so far.
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Old 09-06-2013, 04:44 PM   #14
Martee48
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Default Re: Batteries lacking the power

Another day. Continious monitoring shows a low of 35.9 going up the Big Hill towards the end of a 5 hour outing. Again after a one round of golf and several side trips, the end voltage of the pack was 37.8, down from a start of 38.3.

Still having the original SoC disconnected.

I printed the chart out that was provided in an earlier post since I started to panic when I saw the 37.8 and I hadn't still had several holes to go plus the Hill. Got confused it is 36.3 that is 50% not 37.6. whew!.

Still didn't get meter, probably will recieve it next week. Tomorrow is the big day, 36 holes and several side trip including the Hill. Shooting to be above 36.3 after completing all of this.

Still not brave enough to reconnect the original SoC Meter, maybe after the test tomorrow.

Thanks for all the help.
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Old 09-06-2013, 05:56 PM   #15
JohnnieB
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Default Re: Batteries lacking the power

You only used about 12% of your storage capacity, so my guess is that your batteries will end up around 37.3v if you double the holes played and side trips.
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