Another battery question

[JMGreco]

Okay, charged the cart at 3:30 yesterday afternoon. Before going to bed, checked voltage and was floating at 45.1. I know that it has not rested / settled for 12 hrs but plan on using to use the cart this morning for some chores. After charge last night, pack voltage reading 39.1 this morning. Individual battery voltage;

2012 Deka Pro Master = 6.60
2011 US 2200 XC = 6.52
2011 US 2200 XC = 6.52
2010 US 2200 XC = 6.49
2010 US 2200 XC = 6.47
2010 US 2200 XC = 6.43

This is the highest pack voltage I have seen thus far. Pack voltage prior to charging last night was down to 37.3 at rest. I have not done an individual voltage reading under load but on some my hills yesterday I saw voltage drops down to 29. +/-. This was pulling a cart with wood and one or two kids on cart.

[remac]

Those look like good voltages, higher than usual but that's why you posted.
Maybe your overall voltage increase was do to changing the battery.
Might have had some corrosion on the old battery terminal
or a loose connection that you tightened up during the change.

[JohnnieB]

There are four grades of Deka Pro Master 6V batteries ranging from 215AH to 255AH.
I suspect you have the GC10, which is 215AH and has a black case and top.

I'm not sure how long the batteries rested before the voltages were taken, but it appears the Deka is being charged more than the US Battery batteries, which in turn means one of your batteries is being overcharged while the other five are being undercharged.

Basically, the smaller amp-hour Deka battery is limiting both the charge and discharge characteristics of the entire battery pack.

The five US 2200 XC batteries are all within 0.1V of each other despite being different ages, so replacing the Deka with a used US 2200 XC battery, or just about anything about the same age and about 232AH, would very likely give you a couple more years of usable service life.

The magic numbers for Under-Load voltages are 1.75VPC (Volts per Cell) and 1.5VPC.
When battery manufacturers do non-destructive testing of their products they stop at 1.75VPC, so that is a good number to stay above while climbing hills and other heavy loading situations. That would be 31.5V for a 36V battery pack.

Irreversible physical damage can and does occur when the batteries are taken below 1.5VPC under load. That is the number to absolutely stay above. A 36V pack has 18 x 2V cells, so 27V is the number.

Pack voltage is an average of all cells/batteries in the pack, so the Deka battery being the least in AH may have been considerably lower the the 1.61VPC indicated by the 29V pack reading.

[JMGreco]

remac - JonnieB, thanks for the replays and info. I have been looking for a reason why to upgrade from 36 to 48 volt and this may be my justification this spring / summer. I am thinking of a EMP two speed motor for a winter project fully understanding that the improved performance will not be fully achieved until my battery situation is address. More $ = more fun.

I did the chores I mentioned this morning, hauled some more wood, wife took a ride with my daughter, etc. and voltage after rest 38.5.