Another battery question

JMGreco

I have a basterdized set of US 2200 6V batteries. Original pack was purchased in 2010. My cart was in a wreck / roll over in 2011. Two batteries did not survive and were replaced. After one year of the rebuild one of the original batteies went bad and I replaced it with a Deka equivilant of T-105.

When the original pack was installed pre-accident, voltage after a vull charge would be 38.4 after twelve hours with very good run time. Recently I have noticed my runtime has decreased a little, but after a full charge and rest of twelve hours I am seeing voltages of 38.7 - 38.6?

I know that JohnnieB explained surface voltage to be the culprit of higher voltage reading but why did the original pack never do this? Is this a sign that pack is starting to deteriorate? Individual battery voltage seem fine after full charge and rest as well with very little variation between batteries.

As always, appreciate everyone's feedback.

BGW

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remac

What I have seen in other replies - you have to be careful mixing batteries.
What might help sort this out is to make up a chart of your batteries.
Somethine like this:
(numbers run from POS cable to NEG cable)
# MFG Rating Year Voltage
1 US2200 245 2010 6.37
2 US2200 245 2010 6.00
3 Deka 230 2012 6.42
4 US2200 245 2011 6.42
5 US2200 245 2010 6.20
6 US2200 245 2011 6.39

Your voltages may vary.....

Anyway - important part in replacing batteries appears to be matching rating.
Second important part in finding problems is to look for differences.
In the case above - I would worry about #2 and #5.

I have seen several people refer to giving the batteries a full charge
and then checking the voltages 12 hours later to get a stable reading.

Hope this gives you something to do until the real experts chime in.

JMGreco

remac - thanks for the tip, and agree that ideally you don't want to mix and match like I have done. I have to cut the cord and replace the entire pack at some point. From what I have learned here, the larger pack of batteries (in my case, the oldest) will bring down the new batteries to their (oldest batteries) level. Still don't know why voltage after full charge and rest is increasing?

scottyb

remac is steering you right.
In his example the readings for #2 and 3 appear to be too far apart to be compatible in the same string.
If just one of your replacement batteries is a lower amp hour capacity or any battery weakens under load, overall performance will drop off.
More important than standing voltage is the under load voltage. Connect your DVM to each battery and run up a short hill. Note the drop in each one and compare those numbers. This will give a better look into what is happening when you are running the cart.

remac

JohnnieB is a REAL GOOD source of information.

He just posted a chart on another thread about batteries
that lists all the manufacturers and their battery ratings.
Looks like your US Battery 2200 are actually 232AH rated
so the Deka is real close at 230AH.

remac

Actually - we might need to get back to basics.
I just re-read your original post and your question was about the
voltage level being higher after resting than it was years ago.

Are you using the same DVM that was used years ago?
Have you recalibrated the DVM or checked it against another source?
Are you connecting to the same points to measure the voltage?
Did you change the cable or connectors on the DVM?
Did you change the battery cables or connectors?

When making measurements we have to remember that the instrument
is part of the system being measured and changing the instrument
or the point where the measurements are taken can change the results.

JMGreco

remac - DVM is the digital onboard one the Scotty, Carts Unlimited has. Everything else has remained constant with hand held DVM, cables, connectors, etc.

JohnnieB

Sounds like you've got a triple whammy going on.
1. Mixed battery ages.
2. Mixed battery brands.
3. Mixed AH ratings.

The first one is bad, but the other two are worse.

With mixed ages, the newer batteries soon acquire approximately the same aging characteristics as the older batteries and the whole pack wears out at about the same time as it would have originally.

Mixed brands may or may not play well together. It depends on which brands being mixed.
In this case, a fully charged US Battery has a higher voltage than a fully charged Deka battery.
I don't have a SoC charge chart specifically for Deka Batteries, but here are two for US Battery and one for Trojan, notice the 100% voltage is different on each.
The batteries are being charged in series and the current flow will be determined by the On-Charge pack voltage, but the amp flow through all of the batteries will be equal and for the same amount of time, so the ending SoC of each battery will vary according to brand and age.

Mixed AH ratings will have about the same results, the higher AH batteries will be consistently undercharged while the lower AH batteries will be consistently overcharged.
Both conditions will shorten lifespan.

Attached Images

	USBatterySOCtable.jpg (107.7 KB, 0 views)
	SoC vs Voltage - US Battery.JPG (58.1 KB, 0 views)
	SoC vs Voltage - Trojan Battery.JPG (56.9 KB, 0 views)

JMGreco

Okay - sounds like I should just be prepaired to upgrade to 6 T-875 soon. Hope I can make it through the winter - thanks for the insight.

remac

Just to make it absolutely clear....

I made up ALMOST ALL of the numbers in the chart
it was loosely based on his narrative
but was intended as an example of what he could do
to compare the individual batteries.

His original question was (to paraphrase):
'why am I getting higher resting voltage now
than I was a couple years ago?'