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Old 20-07-2012, 18:53   #61
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Re: Golf cart batteries

OK. I've got a real-world test underway.

Test batteries: two 5-month old T-105 golf-cart batteries in series....225AH @ 12VDC.

All measurements made with a calibrated Fluke 189 and a Watts Up monitor

Began with the Trojans fully charged. Voltage 10 mins off charge: 13.2VDC

Applied a 12-amp resistive load (C/18.75). Been running about 2.5 hours now.

Have removed a total of 28 AH so far, or about 12% of total capacity. This was done at a rate nearly 3.5 times that of Don's situation.

Voltage right now under load is 12.35 at the battery terminals. When I remove the load, within 10 mins the voltage climbs back up to 12.66VDC.

My plan is to pull the resting voltage down to 12.5 (about 75% SOC) and then to apply a 3.5 amp load overnight. This load is very nearly equivalent to Don's 7A load with his 460AH battery bank.

So, starting at 12.5VDC resting, we'll see what happens overnite.

Will report findings in the AM if time permits....gotta work on a boat on the Chesapeake all day tomorrow.

Bill
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Old 20-07-2012, 20:02   #62
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Re: Golf cart batteries

Bill-- do you have a typo? You have a higher voltage reading while under load than when resting.
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Old 20-07-2012, 20:07   #63
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Re: Golf cart batteries

Quote:
Originally Posted by foggysail View Post
Bill-- do you have a typo? You have a higher voltage reading while under load than when resting.
Yes. Thanks for catching that. The voltage under load was 12.35VDC, not 13.35VDC. Unfortunately, I can't edit the error now...too late I guess.

I've now taken 45AH out of the 225AH battery bank or about 20%, so I'm going to begin the overnite 3.5A load soon. Resting voltage is 12.53 about 3 mins after removing load, and still increasing. I'll give it 10 minutes as before, then start the overnite.

Thanks, again for the catch.

Bill
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Old 20-07-2012, 20:18   #64
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Re: Golf cart batteries

OK. 10:15PM. Resting voltage after 10 minutes climbed to 12.57VDC.

Getting late; gotta start the overnite.

Applied a load of 3.7A two minutes ago. Voltage under load is 12.52 and dropping slowly.

Will leave this overnite and record data in the morning.

Bill
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Old 20-07-2012, 20:22   #65
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Re: Golf cart batteries

Bill--

Two questions, first the graph where you show some kind of status for your 8 Trojans, I am lost with what the numbers represent on the X axis. Surely they are too low for specific gravity.

Second-- how are you adjusting your float voltages? Are you using a custom charger or maybe an alternator where you have control of the field voltage? I have a Xantrex XC5012 charger. The float is not adjustable.

Foggy

EDIT: I am looking at Xantrex's specifications. Appears I can get a higher float voltage if I set the charger for Gel cells rather than flooded.

Flooded 12.8 @122F, 13.5 @77F, 14.2 @32F

Gel-----13.1 @122F, 13.8 @77F, 14.5 @32F

Ironically the absorption voltages for Gel are lower than the flooded.

Flooded 13.7 @122F, 14.4 @77F, 15.1 @32F

Gel-----13.5 @122F, 14.2 @77F, 14.9 @32F
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Old 20-07-2012, 20:46   #66
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Re: Golf cart batteries

Foggy,

The X-axis represents MCA....marine cranking amps. The Midtronics testers don't measure AH directly, so I use MCA as a proxy. New golf-carts measure just over 800 MCA (like the two at the top of the graph).

Over the years I've found this to be a pretty good measure of flooded battery health. It's perhaps less reliable with gels and, especially, AGMs, but it nevertheless provides a consistent measure of "capacity"....more or less :-)

I am able to adjust absorption, float, and "repeat absorption" voltages with the Victron Multi-Plus inverter/charger. It has a wide range of adjustments which can be made with the internal switches (a pain in the butt) or with a special software program provided by Victron. I use the program!

Bill
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Old 20-07-2012, 20:56   #67
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Re: Golf cart batteries

Quote:
Originally Posted by DotDun View Post
Southwest Florida retail for T-105's is $86 at a Golf Cart store.
Please post a phone number and address for this distributor and I will send a truck down from Maine and load up...
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Old 20-07-2012, 21:11   #68
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Re: Golf cart batteries

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Please post a phone number and address for this distributor and I will send a truck down from Maine and load up...
Maine Sail---

That truck will most likely use RT95 for its travels. Please contact me when it departs with batteries. I would like him to stop on route at the Massachusetts/Rhode Island border and drop off 10 for me.

Foggy

EDIT: Maybe we should not be too quick to order these things! I came across many places during my battery hunt that offered USED BATTERIES for sale. This just might be one of those companies!
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Old 20-07-2012, 21:15   #69
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Re: Golf cart batteries

Quote:
Originally Posted by btrayfors View Post
Foggy,

The X-axis represents MCA....marine cranking amps. The Midtronics testers don't measure AH directly, so I use MCA as a proxy. New golf-carts measure just over 800 MCA (like the two at the top of the graph).

Over the years I've found this to be a pretty good measure of flooded battery health. It's perhaps less reliable with gels and, especially, AGMs, but it nevertheless provides a consistent measure of "capacity"....more or less :-)

I am able to adjust absorption, float, and "repeat absorption" voltages with the Victron Multi-Plus inverter/charger. It has a wide range of adjustments which can be made with the internal switches (a pain in the butt) or with a special software program provided by Victron. I use the program!

Bill

Thanks Bill for the clarification!

Foggy
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Old 20-07-2012, 21:29   #70
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Re: Golf cart batteries

Quote:
Originally Posted by foggysail View Post

EDIT: Maybe we should not be too quick to order these things! I came across many places during my battery hunt that offered USED BATTERIES for sale. This just might be one of those companies!
That is what I fully suspect. Wholesaler/distributor cost is more than $86.00 on new T05's, even for a large wholesaler..


There are many unscrupulous people out there willing to take your $$$.... Still I'd like some contact info so I can check into it. Up here I could re-sell those and pocket $50.00+ per battery and still beat our local distributor even at their non-retail "wholesale" price... The thing is I want NEW T05's for $86.00 each and I've not seen than since about 1999 - 2000....
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Old 20-07-2012, 23:24   #71
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Re: Golf cart batteries

Info.I have come across a battery brand called Centennial.I believe their batteries are made by Trojan.They are cheaper than Trojans.What I dont know is if they are a separate company or if Trojan own them .Perhaps someone in the battery business can comment if it would be easy for Trojan to alter the specs for a cheaper brand or if they are likely to be regular Trojans.
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Old 21-07-2012, 05:37   #72
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Re: Golf cart batteries

OK. Saturday, 0715. Test over.

Batteries have been on a 3.7A load for 9 hours overnight.

A total of 77.2AH has been removed from the batteries since full, or 34.3% of their rated capacity.

Voltage under load at 0715 was 12.26VDC. Again, this is voltage measured at the battery terminals. It makes a difference, as if you take measurements further downstream they may show considerably less.

So, in this case, a pair of Trojan T-105 batteries in series, totaling 225AH rated capacity, showed 12.26VDC under a 3.7 amp load when 34% discharged.

Gotta go prepare for work on a boat today...first decent day we've had in a long time, with a high of 81F forecast.

Bill
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Old 21-07-2012, 06:29   #73
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Re: Golf cart batteries

Quote:
Originally Posted by Maine Sail View Post
Please post a phone number and address for this distributor and I will send a truck down from Maine and load up...
Affordable Carts - Batteries

Just pulled the receipt: $86 + $16 core per battery. (~ 6 months ago)

Of course, I had trade-ins, so no core for me.
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Old 21-07-2012, 07:02   #74
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Re: Golf cart batteries

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Originally Posted by DotDun View Post
Affordable Carts - Batteries

Just pulled the receipt: $86 + $16 core per battery. (~ 6 months ago)

Of course, I had trade-ins, so no core for me.
And yes, they were new batteries (if fact the month before 'born on'). Apparently, Trojan predicts shelf time.
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Old 21-07-2012, 07:15   #75
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Re: Golf cart batteries

I suspect part of the problem is that some of Don's numbers don't make much sense..
Quote:
Originally Posted by Don Lucas View Post
a couple of weeks ago I recorded the resting voltage for a few days and it varied around 12.58 to 12.4 with SOC between 99 and 92%
If that was a true "resting voltage" reading then your monitor is either off or giving you what it "thinks" is the Peukert corrected SOC, in which case the voltage should be much higher than 12V under load..

12.4V is about 72% SOC 12.58V on a Trojan is 86% SOC not 99% - 92% full. A Trojan wet battery, after resting, (this means fully disconnected from everything for 12-24 hours) should read 12.73V.

It appears the monitor is out of calibration which could be due to an incorrect Peukert #, CEF etc. etc. or the solar panel tricking it into thinking the bank is full. Solar panels very often trick the monitors into re-setting to full as they are below the "full" current threshold for the specified period of time needed for a re-set to 100%.

When re-setting, based on 2% acceptance, it is important to determine this with absolutely no loads on and no other charging sources.. All DC loads should be shut off and the solar panel also turned off before determining the accepted current to the bank. The solar panel has the potential to trick the regulator into cutting back if the absorption voltage is set slightly higher than the alts voltage regulator. This can cause you to "think" your batts are only taking 2%.

Had this exact situation a short while ago and the VR was actually cutting field output to 0% because the bank voltage was higher than the solar controllers setting. The solar panel was supplying the "current" not the alt. Owner thought bank was full because it was only taking a few amps. Shut off solar charge controller and the alternator kicked back on and was supplying current again... Simply adjusted the VR to .2V higher than the solar controller and all was well..

As Bill mentioned a 450Ah bank of Trojans's should not be anywhere near 12V based on your description. I suspect your bank is not as charged as you think and have some monitor calibration issues causing the confusion. You may also have another load on there not being counted by the shunt. Can you post a picture of the house bank wiring and wiring between house bank neg and the shunt?

I am sure we can get this sorted out...

P.S. Just for grins I just ran the Peukert Exponent calcs for a bank of 450Ah T105's.

At a 6A draw, if you drew the bank to 10.5, volts you'd get 626 Ah's out of the bank..

At a 22.5A load your bank would deliver 450 Ah's before falling to 10.5V or what is considered the cut off for a 20 hour capacity test...
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