Battery meter question

[JohnnieB]

Originally Posted by sprocket

O.K., so I'm thinking about my batt meter going through the key switch and having the reading a little bit low. I tell my better half that when it gets down to 37 to put it on the charger. Now I'm thinking that when the meter reads @ 37, that it's actually 37.? which still is safe.....point is with the "low" reading it's safer for the batts than a "high" reading at the meter. Does that make any sense!!

The battery meter reading a little low does toss in a safety margin.

Another fudge factor built into the system (Sort of ) is the fact the batteries will read low while driving and for several minutes after stopping.

----
Yesterday, I measured how many AH was used on a 10.2 mile trip by measuring the voltage before I left and after I got back.
The starting at-rest voltage was 25 hours after the batteries were taken off float charge, and when I returned home, I recorded the pack voltage upon stopping, then at 5, 10, 15, 20, 30 and 60 minutes.

When I stopped I had 37.05V and an hour later it was 37.57V.
The bulk of the change occurred in the first 20 minutes.

BTW - I used 3.97AH per mile , or got 443.3 Yards per AH.

[sprocket]

One fun thing about the battery meter is watching the volts recover after a drive then stopping. After a drive and going up a hill or grade I can feather the pedal a bit to keep the load over 31. I can't recommend another part that will offer so much info on anyone's cart.

[JohnnieB]

We technical types are easy to entertain.

[scottyb]

Originally Posted by JohnnieB

We technical types are easy to entertain.

That explains alot LOL

I like reading the load tests. I have a couple of 45% dirt banks I can shoot up and watch the pack voltage drop. And charging is always done early because I know each time I get on the cart what the SOC is. The meter is Brilliant

[Springlake]

What a great post you tech have going here. For newbies the information is fantastic. Did I see once, a post that tells us the lowest % and/or volts recommended? In layman terms when should we stop driving the cart before damage to our equipment occurs?

[JohnnieB]

Originally Posted by scottyb

.............
I like reading the load tests. I have a couple of 45% dirt banks I can shoot up and watch the pack voltage drop. And charging is always done early because I know each time I get on the cart what the SOC is. The meter is Brilliant

I like the DPI charger for almost the same reason.
It goes into float charge and my batteries are always fully charged when I take my cart out for the first trip of the day.

I've got paved roads with 45% grades.

Originally Posted by Springlake

In layman terms when should we stop driving the cart before damage to our equipment occurs?

personally .. i drive no lower than 36.5v on my meter

[JohnnieB]

Originally Posted by Springlake

What a great post you tech have going here. For newbies the information is fantastic. Did I see once, a post that tells us the lowest % and/or volts recommended? In layman terms when should we stop driving the cart before damage to our equipment occurs?

Battery pack voltage under load? Best not to go below 1.75VPC (Volts per Cell), which is 31.5V for a 36V pack, 38.8V for a 42V pack and 42.0V for a 48V pack.

Motor Temperature? Too hot to touch is too hot to run.
Under the most extreme conditions (tall tires, high amp controllers, steep hills, soft ground, heavy foot on the pedal, etc.) the motor is going to get very hot, but should still stay under the boiling point of water.

Controller Temperature? It will warm up quite a bit, but you ought to be able to leave your hand on it.

Cable, Solenoid, F/R assembly in series cart temperature? If they feel more than slightly warm to the touch (about 10°F above the air temperature), they are getting too warm and should be fixed or replaced.

Hope this helps.

[sprocket]

Just to be clear, I charge when meter reads no less than 37. I watch the meter going up all hills big or small and only press accelerator down so the volts don't go down (or load) below 31.? volts. My batteries are older and I can load them below 31 but I avoid it at all costs. I just use my cart around a farm property so I don't have long drives. Clearer!?