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navyflyer 06-27-2013 08:14 AM

DC Voltmeter help
 
1 Attachment(s)
Hello everybody,
1) I have a 2008 Precedent. 4X12 2011 batteries. Added a voltmeter (as pictured below) wired correctly (thanks to this forum). My question is, after about 5-10 minutes of driving, it goes way down, like to 50%, and eventually into 30-40% range...is this right? Should it not be staying up in the 90% range and SLOWLY show drain?
Am I interpreting the info wrong?
2) The orange factory LOW BATT light (I was told) comes on at less than 50% charge. Is that true? If so, why would my new voltmeter show less that 50% and the factory light not come on?

I'm thinking either the new voltmeter is defective, or I'm just not undertanding what's going on with DC battery drain.

Thanks for your help.

scottyb 06-27-2013 08:55 AM

Re: DC Voltmeter help
 
2 Attachment(s)
Bar graph meters are inaccurate. Assuming you have it wired correctly you should get voltage readings at full and 1 bar down then 2 bars down etc, so you have some real numbers to compare to this chart. A much better choice would have been a digital meter which reads actual pack voltage. As a service tech those things drove me. Seems no 2 read the same and they reset to 100% after every charge regardless of the pack total voltage.
After all voltage is what we want to measure.
See chart

navyflyer 06-27-2013 09:18 AM

Re: DC Voltmeter help
 
Sooo, my bar voltmeter is showing correctly, BUT not in a scale that I'm accustomed to (or was expecting to see). For example, your chart shows 48.4V at 50%...I was thinking 50% should be 24V. Is it true to say that with these batteries 100% to empty is 50.96V to 46.00V?

The guage is working fine, it's just not 'calibrated' to what I think 'calibrated' should be. (Like a car gas tank 1/2 is half and E is E).

Your pic above shows a full 36V battery charge...so if you see that it's getting near 35 or so, you are getting low, right? Is that how you tell you're getting low?

Thanks for your patience and reply.

navyflyer 06-27-2013 09:29 AM

Re: DC Voltmeter help
 
10% drop in charge is a loss of roughly .49V...NOT 4.8V like I was thinking I'd see.

Nccart 06-27-2013 09:31 AM

Quote:

Originally Posted by navyflyer (Post 900188)
Sooo, my bar voltmeter is showing correctly, BUT not in a scale that I'm accustomed to (or was expecting to see). For example, your chart shows 48.4V at 50%...I was thinking 50% should be 24V. Is it true to say that with these batteries 100% to empty is 50.96V to 46.00V?

The guage is working fine, it's just not 'calibrated' to what I think 'calibrated' should be. (Like a car gas tank 1/2 is half and E is E).

Your pic above shows a full 36V battery charge...so if you see that it's getting near 35 or so, you are getting low, right? Is that how you tell you're getting low?

Thanks for your patience and reply.

That's correct. When you get to 50%,according to the chart, it's time to charge. Draining much lower than that decreases the life of your batteries.

doodles bug 06-27-2013 09:34 AM

Re: DC Voltmeter help
 
When are you reading the gauge? Stopped or under load.

Batteries have what we term an “internal resistance”. They have some resistance and it’s also a chemical reaction function.

The charts you may be looking at are probably for NO LOAD. As soon as you mash down on the go pedal, the voltage will drop.

There is also the resistance caused by heat both in the batteries and in the cables. With no load, this is minimal but under load there is a substantial voltage drop.

Also, how is your indicator calibrated? Does the last segment go off at zero volts or does it go off at some other voltage indicating the batteries are at minimum operating level.

navyflyer 06-27-2013 09:56 AM

Re: DC Voltmeter help
 
Operator error fellas...it's making sense now, did more reading/searching on the boards.

I'm going to hook up handheld voltmeter to see what my aftermarket voltmeter's scale truly is.

My yellow battery light should come on at 48.4V or so, I want to see where that is on my aftermarket scale. What I'm thinking is when the aftermarket meter shows "E", the low batt light will be flickering/near flickering..do we treat 50% as empty for battery health sake then?

What I'd like (and was expecting) is a meter calibrated so 50.96 is "FULL" and 46.0V is "E"

Thanks again. Sorry for the ignorance...

cmalberto 06-27-2013 10:47 AM

Re: DC Voltmeter help
 
Quote:

Originally Posted by navyflyer (Post 900214)

Thanks again. Sorry for the ignorance...

It is not ignorance...it is just an opportunity to learn and we have ll been there...especially some of us newer Cart members.

anix 06-27-2013 10:57 AM

Re: DC Voltmeter help
 
I would rather use one like Scotty is showing. At least with digital you know what's happening under different load conditions. Those bars may be .5 or even 1V apart and a few tenths may be trying to tell you something. Not sure but I think they make one that can be wired in so that you can monitor the pac as a whole or switch to each battery one at a time. This would be a very valuable tool.

jakesnake27 06-27-2013 11:16 AM

Re: DC Voltmeter help
 
Quote:

Originally Posted by anix (Post 900237)
I would rather use one like Scotty is showing. At least with digital you know what's happening under different load conditions. Those bars may be .5 or even 1V apart and a few tenths may be trying to tell you something. Not sure but I think they make one that can be wired in so that you can monitor the pac as a whole or switch to each battery one at a time. This would be a very valuable tool.

I installed a digital meter on my cart this year, and it is very nice. When I go up a hill, it drops even as low as 43-44 volts. I didn't know they dropped that low!
Then when at rest, it'll be around 49-51 volts.


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