Battery voltage under load

[Cobra,1]

Have a 2012 ez go txt , bought used,48 volt full charge reads 51.9 volts.batteries are well maintained pushing 5 year old Trojan t 85 8 volts. What should I see as battery voltage going up steep grades? Batteries show equal voltage within .002 volts when charged, cart runs for several hours before reaching 48 volts at which time I charge them. Guess I ‘m asking at what point do I consider replacing batteries?
Thanks 😊

[Volt_Ampere]

As the batteries age you will lose some performance - get more voltage sag. It's time to replace them when they no longer perform adequately for your needs. 5 years is about the normal lifetime for well maintained batteries but some folks get more out of them.

[scottyb]

I allow a voltage sag equal to one battery under load. I'm not saying that in your case an 8v lag is good - I'm saying I don't panic until 8.5

[ThreeCW]

Originally Posted by Cobra,1

Cart runs for several hours before reaching 48 volts at which time I charge them.

You have had a pretty good run with these batteries so far considering what a lot of us consider a deep discharge charging cycle ... 48 volts is about a 55% depth of discharge.

If your usage pattern allows, you would be better off charging your batteries more often at a lower depth of discharge to maximize the battery life (see attached charts).

At a 55% depth of discharge, the expected life of your batteries is 1000 to 1200 charge cycles.

At a 30% depth of discharge, the expected life of your batteries increases to 2000 to 2050 charge cycles.

Something to consider if your usage pattern allows.

[bronsonj]

Originally Posted by Cobra,1

cart runs for several hours before... I charge them

If you are getting 2 hours with the GO pedal pressed, I think that's pretty darned good with lead acid batts.

Replacement though depends on what you need. If you need to be able to ride 2 miles, hit 16 holes and 2 miles back then when they start getting tired on the way back replace them with higher capacity batteries.

If you ride 2 miles to the inlaws and 2 miles back and don't charge but find after doing this 4 days in a row then its sluggish, I'd tell you to charge it every time you park it and don't replace the batteries yet.

[Sir Nuke]

Cobra.....to actually answer your question...."What should I see as battery voltage going up steep grades?" what you need to know is the MINIMUM Voltage you should allow your pack to get to UNDER LOAD. This is something I learned from the BIG BRAINS here..... You have a 48v pack, within it, there are a total of 24 cells (if you have 6-8v, 4 cells in each battery...or 8-6v batteries 3 cells in each battery), and you shouldn't allow your pack get below, under load, 1.75v/cell. SO for your 48v pack, UNDER LOAD, shouldn't get below 42v.


IF you had a 36v cart, you would only have 18 cells X 1.75V = 31.5V minimum voltage while under load.

[Cobra,1]

Great info guys, batteries when fully charged pack reads 51.9 volts pack charge, each battery reads 8.5 to 8.3 . (Seen voltage drop as low as 45 volts going up steep hills) so it seems batteries are nearing thier end of life.(even know they serve my purpose, I do charge them after every use, be it 10 minutes or 1 hour of use along monitoring water levels that don’t seem to go down. Has onboard charger. If it’s parked it’s plugged into charger.
Since cart is only used several times a year while camping ( wish Icould use it more ) guess I’ll figure on replacing them in the spring as I’ll probably use it for a total of maybe 4 hours the rest of this year then it will sit till April when I start camping again. At that point figure I’ ll do a lead acid replacement since payback on lithium upgrade would not be worth the investment for my use for a few trips/ use’s a year. Comments welcome as usual knowing my intentions for cart.
Thanks or the help😊

[BobBoyce]

Carts that are unused a lot hold up better with lithium. No battery maintenance required when parked. Just unplug the pack and they will be ready to go when you return to use it.

[DaveTM]

My 8 6V Trojan T-105's are dated 2012. I bought 'em new and installed them in 2012. Today when I travel up a steep grade, it's not uncommon for the voltage to drop from 51 to 43.

I can assume your maintenance was as well as what I did or your pack would likely be dead at this point. I know that I can get another 6 months (hunting season) out of mine in the colder Pa weather.....but my total travel distance per charge will be well down from a new FL pack.

Check your specific gravity in each battery. That will give you some indication of the life in each battery.

[davewil@mc.net]

Actually, 45 volts going up steep hills is pretty darn good.
My cart with 1 month old Interstate batteries drops to 43 volts. But it goes 17 mph up these hills and over 25 mph on flat ground.