Battery question

[skipsmith521]

I have a new battery set, using Scottyb break-in.

I am about a dozen or more cycles into the break-in.

I noticed the battery will charge up to 45 or so and charger turns off...and if not driven, the pack will settle to 38.3 after a day or so.

How long if not driven will it stay at 38.2 before coming down further on its own? The SOC chart shows this to be full charge as I understand.

1) is this days or weeks it will stay at that point?
2) what is best if it sits there and drops below 38.2? Do you go and plug back in the charger? Is it best to always top it off if you don't drive it?

So far during the break in, I have charged it up full and kids would drive it....go back on the charger. If they did not take it out, then i would drive it even if I did really want to go out on a drive....just to go through a break in period.

Thx for help

Skip





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[cgtech]

It will drop (self-discharge) on its own. It is suggested that they may lose 1% per day. It is best to occasionally unplug & replug your charger to keep the SOC up to as close to full as practical.

[honcho]

I bought 3 12v trickle chargers. Bought brand new batteries for the 3rd time since owning the cart. Keep my batteries on trickle charge all the time,usually only take cart out on weekends, my batteries are doing wonderful after 2 yrs,in my opinion,those big chargers fry the batteries over a period of time as you can hear them sizzling when they are on the charger. BTW I have not had to add any water to them in 2 yrs!

[scottyb]

Originally Posted by honcho

I bought 3 12v trickle chargers. Bought brand new batteries for the 3rd time since owning the cart. Keep my batteries on trickle charge all the time,usually only take cart out on weekends, my batteries are doing wonderful after 2 yrs,in my opinion,those big chargers fry the batteries over a period of time as you can hear them sizzling when they are on the charger. BTW I have not had to add any water to them in 2 yrs!

You may be stratifying your cells. Lead acid batteries have a tendency to let the heavy elements settle to the bottom of the cell and if they are not stirred up with some good ole fashion high amperage charge those minerals will never be in the equation again.

A float charge is good but a bulk charge is also an important part of lead acid battery performance + 2 years is not long enough know.

[skipsmith521]

I guess this is where one of those DPI chargers come in handy... Not sure about all what they do.

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[honcho]

Yea Scottyb you may be right,don't know that much about batteries, maybe I should run them down,and give them a going boiling with the big charger. I have 2 classic cars that don't get driven that much and always on a trickle. Have a Chevy diesel that doesn't get driven hardly at all and as you know with 2 batteries, it's an 2004,and just had to replace both batteries last year,but they had always been on a trickle, so getting 11yrs out of those batteries,factory batteries,I thought was pretty cool.

[honcho]

Sorry skipsmith521 did not mean to hijack thread

[JohnnieB]

Skip,

All Lead-Acid batteries self-discharge, some make/model batteries faster, some make/model batteries slower, but in very general terms, 1% of the storage capacity per day is a reasonably safe guess for estimating how long a battery pack can allowed to sit without being recharged.

When the battery is less than 100% charged, there is lead sulfate on the plates, which is part of the normal chemical reaction that produces electricity. When the battery is charged, the lead sulfate on the plates is chemically converted back into sulfuric acid and the surface of the plates convert back to lead (Negative plate) and lead-dioxide (Positive plate). The problem is that as the lead sulfate is sitting on the plates, it is crystallizing and over time, the tiny crystalline structures join and form larger crystals. At some point the crystals become too large and strong to be broken down by the normal charging process. The net result is that some of the active chemistry needed to produce electricity is locked up in an inactive crystal and the storage capacity of the battery is less.

How quickly small lead sulfate crystals grow into large sulfate crystals is influenced by how many small crystals exist and the deeper the battery is discharged, the more small crystals there are available on the plates and the faster they join and grow into large crystals.

The crystal growth rate while the battery is between 70% SoC and 100% SoC is relatively modest, but below 70% SoC it kicks into high gear and becomes a significant issue.

This process (plates becoming sulfated) is known as aging and is unavoidable, but the rate of aging can be reduced by keeping the batteries as full charged as possible and practical.

As mentioned, the 1% per day self-discharge rate is a general rule of thumb and will vary by make and model of the batteries as well as climate of the area since batteries self-discharge faster as the temperature increases. To determine the self discharge rate for your specific battery pack, let the pack sit about 24 hours after the charger shuts off automatically and measure the voltage. Call that 100% SoC. Let the batteries sit without being charged or used for several days, measure the voltage and determine the SoC. Divide the difference in SoC by the number of days and you have the self-discharge rate.

The you can use that rate to determine how long your batteries can sit without going below 70% SoC. Of course, you can pick a higher SoC than 70% and charge more often.

However, if you have a charger that float charges after the regular charge cycle finishes, you batteries stay at 100% SoC and periodically initiating a charge cycle isn't needed while the cart isn't being used for extended periods of time.

[JohnnieB]

Honcho,

There are two schools of thought about battery charging. Low amps for a long period of time and high amps for a short period of time. The chargers commonly used for charging golf cart batteries fall somewhere in the middle of those two extremes, typically on the lower amp, longer time side.

Attached is the recommended charge profile for Trojan batteries and most of the legacy type chargers are based on that profile.

Notice that the recommended charge rate during the bulk charge phase is 10% to 13% of the battery's storage capacity at the 20Hr rate. The standard 36V battery pack uses T-105 batteries, which are rated at 225AH, so the charge rate would be from 22.5A to 29.25A. Many of the 36V golf cart chargers put out in the 18A to 20A range, so they are on the lower amp, longer time side of the recommendation.

However, using low amp charging is okay if you have sufficient time between cart uses to fully charge the battery pack.

[honcho]

Thanks JohnnieB you are a wealth of knowledge my man,I think I am gonna continue using my trickle chargers and see if I can get more life out of these batteries than the batteries that have fried up on me in years past. BTW I checked my records and installed these batteries May of 2013,so it will be interesting to see trickle charge vs regular charge, which one will give me more life out of my batteries!!