Low voltage alarm circuit...exist?

[slashpine]

just an off the wall wonder...

I'm curious if anyone offers commercially or has come up with a DIY mod for a low voltage alarm?...i.e., something simple like a SoC meter that when the voltage reaches 55% of the pack voltage closes a relay that that can be connected to some type of alarm...??

I'm curious because there may be times of up to a week or better where our cart could be used by folks that are not familiar with golf carts at all and will know nothing about voltages etc... or the importance of letting a pack go below a 50% SoC...

[cgtech]

Originally Posted by slashpine

just an off the wall wonder...

I'm curious if anyone offers commercially or has come up with a DIY mod for a low voltage alarm?...i.e., something simple like a SoC meter that when the voltage reaches 55% of the pack voltage closes a relay that that can be connected to some type of alarm...??

I'm curious because there may be times of up to a week or better where our cart could be used by folks that are not familiar with golf carts at all and will know nothing about voltages etc... or the importance of letting a pack go below a 50% SoC...

I'm not so sure you fully understand the relationship between SoC & battery voltage. 55% of 36v is 19.8v. If your cart is still running at 19.8v, you are doing irreparable damage to the batteries. And back to the original question, no, I have not got around to building that yet. And I don't know any other ones either.

[rib33024]

Every time you drive the cart. At the end of the day put it on the charger. Not drive it for a few days, and then charge it. And if your cart is a 36 volt cart. You would want to charge it when it says 36 volts on your meter. 36 volts is 50% charged pack

[slashpine]

Thanks for the replies...I may have misspoke saying "SoC" meter...I was referring to one of the (fuel type) gauges that have a series of bars that light up as the charge decreases etc...

As for charging every day regardless etc...
According to Scottyb's battery break in procedure it says to run the pack down to 75% and then charge until it stops on its own...still being winter the cart is not currently being used that much so it can take many days to get these new batteries down to 75%...Does this make a difference breaking in a new set of batteries??

FWIW...The scenario that brought up my query about an alarm involves the use of a cart by guests at another cabin that does not have a charger...

[rib33024]

OK.

[cgtech]

In my opinion, no charger = no golf cart.

[scottyb]

Originally Posted by slashpine

Thanks for the replies...I may have misspoke saying "SoC" meter...I was referring to one of the (fuel type) gauges that have a series of bars that light up as the charge decreases etc...

As for charging every day regardless etc...
According to Scottyb's battery break in procedure it says to run the pack down to 75% and then charge until it stops on its own...still being winter the cart is not currently being used that much so it can take many days to get these new batteries down to 75%...Does this make a difference breaking in a new set of batteries??

FWIW...The scenario that brought up my query about an alarm involves the use of a cart by guests at another cabin that does not have a charger...

I spent some time working on this last spring but never came up with a reliable solution. I could not find the stuff I needed at a reasonable price.

[yurtle]

ScottyB sold me an Alltrax ExRay that has a user setting Warning and Danger LED for voltage.

[JohnnieB]

The hurdle that has to be crossed is the fact that the battery voltage drops when amps are drawn from the battery. The voltage drop is almost instantaneous (fraction of a second) while voltage recovery is slow (on the order of minutes - total recovery is an hour or more) and the voltage drop under load (amps being drawn) during normal operation of the cart, can exceed the low voltage alarm trip point.

For example, a fully charged 36V pack is 38.2V while 55% SoC is 36.5V and the pack voltage can drop to 34V or less when accelerating from a standstill and down to 35V or so while driving the cart.

[scottyb]

An Alarm based on the battery voltage can easily be triggered by a hill, so I used a delay but on a long hill forget it. It's the battery pack holy grail.