How much water should batteries use?

[bash11]

I have a 36 volt EZ-GO PDS. How much water should I expect to add to the batteries over a 10 week period in the summer if I discharge to about 80% SOC, 3 times a week (30 charges)? Do I use more water when charging more often at a higher starting SOC or charging less often with a deeper discharge? Which scenario do the batteries "like" better and give the maximum Amp-hours of service over the life of the batteries.

How often should I check the battery water level?

Thanks in advance,
Bash11

[Volt_Ampere]

The batteries like to be at a state of full charge. The less you discharge them between charges the longer they will last if you keep them watered properly. Check battery water level at least monthly and more often in hot weather. Always check it and add water after charging - not before. They will overflow if you fill them up before charging. Makes a mess.

[radioman]

You need to check them regularly to determine how often they need watering. A lot of factors go into water usage. I would check the water once a week to see how often they need watering. A deeper discharge will generally require watering more often than charging them after each use. Add water as necessary after charging. This will help prevent overfilling.

[JohnnieB]

Electrolysis occurs whenever a current flows through the electrolyte (Charging or Discharging), but reaches its peak intensity at about 2.35VPC (Volts Per Cell), which is 42.3V for a 36V pack and that primarily occurs during the charge cycle.

At that on-charge voltage, roughly 90% of the Amp-Hours removed from the battery, has been returned to it. Deeper discharging, leaves the batteries in the 90% to 100% portion of the charge cycle for a longer period of time, so they out-gas more Hydrogen and Oxygen.

Ideally, cart batteries should be recharged after each use and between uses they should be float charged at a constant voltage that is below the gassing voltage (2.35VPC) and above the At-Rest voltage (2.122VPC), which is 38.2V for a 36V pack.

The voltages mentions are for Trojan batteries, the voltages for other other makes may vary.

How much water is consumed during normal operation varies by the make/model of batteries, the make/model of the battery charger, the temperature, the relative humidity and depth of discharge as well as other lessor factors.

My seven 6V batteries hold a about 49 Quarts of electrolyte and I typically add about a gallon of distilled water per year. YMMV.

Start checking fluid level at a regular interval and lengthen or shorten the interval as needed.

FWIW: I check mine monthly during the summer months, every other month in spring and fall and before I store it for the winter and before I start riding it in the spring.

[bash11]

Thanks for your help. I am sure my batteries will be happier when I follow your recommendations; and I want happy batteries.

[JohnnieB]

Keeping your batteries happy is second only to keeping SWMBO happy.
(She Who Must Be Obeyed)

[Swan]

happy batteries is a happy wallet

[jjance]

My seven 6V batteries

Does that mean you run seven batteries in series. That would probably explain why you only use one gallon/year of water.

[DaveTM]

My batteries prefer a quality Cabernet Sauvignon. No cheap stuff....there has to be a cork in the bottle!! Wait!! Maybe that's me? I can get confused this time of night. You know.....6:30 EST when I'm on my 3rd glass.

Hey....it's after 5:00.

[JohnnieB]

Originally Posted by jjance

1. Does that mean you run seven batteries in series.
2. That would probably explain why you only use one gallon/year of water.

1. Yep, I run a 42V battery pack. However, they are high AH (245AH) and the cases are taller than the standard capacity (225AH) 6V batteries, so they hold more electrolyte.

I don't have the exact volume for my Exide batteries, or for Trojan batteries, but US Battery was kind enough to provide me with a list of how much electrolyte their batteries contained and the other brands use roughly the same sized cases and pack similar amount of plates and other stuff in the cells, so the amounts ought to be roughly the same for all brands.

6V = 6.44qt to 7.31qt
8V = 5.89qt to 6.82qt
12V = 7.50qt

2. That, plus recharging after each use, float charging between uses, mostly shallow discharges and a moderate climate that doesn't get exceedingly hot or extremely dry. Also, when not being driven, cart is usually parked in the shade and lives in a well ventilated garage with the seat bottom propped up a few inches, when not in use.