T105's in 1999 EZGO not lasting

[sunking]

Originally Posted by JohnnieB

It occurred to me that the projected life expectancy estimates on that chart are based on one discharge/charge cycle per day and the batteries we are talking about is being discharged and charged twice a day.

First the published Cycle Life vs DOD charts from manufactures will never be seen by the consumer. Those charts are made in a lab with tightly controlled environmental conditions and ideal charge/discharge conditions. What a consumer can do is compare charts from one manufacture up against another manufacture to get an idea of which is the better battery in terms of cycle life.

Independent testing agencies have done extensive real world test and with Trojan battery an dothers if, and that is a big if because not many users can limit discharge to 50% DOD, will last on average 750 cycles or 3 years whichever comes first to 50% specified AH capacity. FWIW US Battery about 650 cycles or 3 years whichever comes first.

Originally Posted by JohnnieB

That presents an interesting question: Would the batteries last longer if only charged once a day?

Yes with the caveat those two discharges in a day do not exceed 50% DOD. The biggest flaw or issue with Pb batteries is they do not tolerate operating in PSOC (Partial State of Charge) mode. Any SOC level below 100% causes lead sulfate crystal to start forming on the plates, and if left below 100% those crystals begin to harden, and once hardened cannot be dissolved back into solution. At 50% and below, the process accelerates. 90% of all battery failures are sulfated plates. The other 10% is Plate corrosion from over charging.

A few years ago Trojan and other battery manufactures were getting hammered with warranty claims from solar users who limit daily DOD to 20% and give their batteries TLC. To counter this Trojan did two things. They changed charging profiles for RE users raising the Absorb charge voltage for their Signature line of batteries which include the T-105. Second thing they did is came out with a new product line called RE (Renewable Energy), and incorporated the T2 technology carbon/pb plates used in the Industrial line. The RE and Ind Premium Line are true deep cycle batteries with heavier thicker plates that have longer warranty. They even make a T-105RE. These batteries are made to operate in PSOC mode between 50% to 100% SOC region.. Note do not use Trojan RE line in a cart, won's work because they are real deep cycle batteries and as such internal resistance is too high to supply the high C-Rates.

FWIW lithium can and should be operated in the PSOC region. In fact should never be charged fully to 100%. They only need recharged once you get down to 10-20% SOC, thus reducing charge cycles. Most LFP batteries are rated to 2000 cycles when operated at 10-100% SOC. Cut that back to 10-90% SOC and cycle life on paper goes up to 4000 cycles. Both Chevy Volt and Nissan Leaf will not allow their batteries to ever be fully charged up for this very reason.

[april]

Originally Posted by JohnnieB

No, it would be normal for the cart to be moving at 50% unless the batteries had severely sulfated plates. (IE: At or near the end of their useable life)

What was the pack voltage while the cart was trying to move and not succeeding?

Cart has been showing down to 21 while struggling on the new voltmeter that I got from Scotty.

So, with this new voltmeter and the notes that came with it, I am supposed to recharge the batteries when they get down to 37-36.3.
The problem is, if I get done morning chores and the vm is reading 37+, if I don't charge it there is no way that it is going to last for evening chores.
Am I still overcharging?

FYI: the last couple of days the vm was reading between 37 and 38 when done use. It's been showing 39+ when we start.

[CCFanatic]

JohnnieB's SoC Chart 2.jpg

[usgicollector]

Originally Posted by april

Cart has been showing down to 21 while struggling on the new voltmeter that I got from Scotty.

So, with this new voltmeter and the notes that came with it, I am supposed to recharge the batteries when they get down to 37-36.3.
The problem is, if I get done morning chores and the vm is reading 37+, if I don't charge it there is no way that it is going to last for evening chores.
Am I still overcharging?

FYI: the last couple of days the vm was reading between 37 and 38 when done use. It's been showing 39+ when we start.

Charge your batteries every time you use your cart. Batteries do better and last longer if they are kept in a fully charged state.

[CCFanatic]

Easy rule of thumb: if it's parked, it's plugged!

[JohnnieB]

Originally Posted by april

Cart has been showing down to 21 while struggling on the new voltmeter that I got from Scotty.

So, with this new voltmeter and the notes that came with it, I am supposed to recharge the batteries when they get down to 37-36.3.
The problem is, if I get done morning chores and the vm is reading 37+, if I don't charge it there is no way that it is going to last for evening chores.
Am I still overcharging?

FYI: the last couple of days the vm was reading between 37 and 38 when done use. It's been showing 39+ when we start.

Hopefully the DVM battery meter is connected directly to the main positive and negative terminals on the battery pack so you are reading the true pack voltage.

The voltage you read while the cart is moving (or trying to move) is "Under-Load" voltage and is not the same as the "At-Rest" voltages that appears of the State of Charge charts. During normal operation, the Under-Load voltage should not drop below 1.75VPC (Volts per Cell), which is 31.5V for a 36V pack. Under extreme conditions, it should not drop below 1.5VPC, or 27.0V for a 36V pack.

If the pack is taken below 1.5VPC, irreversible physical damage can and will occur. Specifically, the surface of the plates is sloughed off.

The fact your batteries drop below 27V during your chore run indicates they are in poor health, and will only get worse.

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The 37-36.3 is the minimum voltage you should ever discharge to, not the voltage you have to discharge to before recharging. You can and should recharge at any voltage above the minimum. General rule of thumb is recharge after each use. If you have driven the cart more than about 100 yards before recharging, you are not overcharging.

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Are you using the DPI charger now?
On the Trojan setting, it floats at 39.4V

[HiTechRedNeck]

Just a thought......

This work cart may be a good candidate for a lithium upgrade.
When a work cart is down it costs productivity as well as cost to fix cart.
As a work cart, reliability/performance factors may justify the cost.

Lower weight giving cart better performance with same loads.
Li's ability to operate in partial charge mode is clearly a bonus here.
10 Yr projected lifespan might save money ..over changing pack every 2 yrs.