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Old 03-08-2022, 12:15 PM   #1
Golf Cart Surgeon
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Default 48v rxv 51v down to 40.9v under load...

Putting a multi meter on while driving full speed, the batteries drop to 40.9v. Bad batteries? The complaint is that they are not lasting as long.
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Old 03-08-2022, 02:29 PM   #2
Volt_Ampere
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Default Re: 48v rxv 51v down to 40.9v under load...

That is a significant drop under load for fully charged batteries. They are probably due for replacement. If they still get the job done, you could continue to use them and prepare for eventual replacement.
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Old 03-08-2022, 02:57 PM   #3
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Default Re: 48v rxv 51v down to 40.9v under load...

Quote:
Originally Posted by Volt_Ampere View Post
That is a significant drop under load for fully charged batteries. They are probably due for replacement. If they still get the job done, you could continue to use them and prepare for eventual replacement.
What does a 48v cart need to be running on full charge under load? 45? 46?
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Old 03-08-2022, 06:04 PM   #4
scottyb
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Default Re: 48v rxv 51v down to 40.9v under load...

At a minimum. If you are asking about a fully charged pack 50.9v running wide open on flat pavement with properly inflated tires I would expect to see 48v. Each volt lost is going to reduce the vehicle speed.
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Old 03-08-2022, 06:08 PM   #5
basshawk84
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Default Re: 48v rxv 51v down to 40.9v under load...

Either the batteries are old or not properly charged. I've seen good RXV packs pull down to 43 volts on a real steep hill.
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Old 03-08-2022, 06:21 PM   #6
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Default Re: 48v rxv 51v down to 40.9v under load...

You might have one bad battery in your pack ... or more.

To get a true picture of the health of the pack, you should repeat the load testing on each battery individually. Record the at rest voltage before each load test and the voltage under load for each battery. This should give you a much better idea what you are dealing with.

What make and model of batteries do you have? And how old are they? Original owner of the battery pack or not? Well maintained or put away wet ... and uncharged?

I have my good 48 volt battery pack typically drop 4 to 5 volts under high loads ... the same pack might drop 2 to 3 volts under lighter loads.
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Old 03-09-2022, 01:42 PM   #7
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Default Re: 48v rxv 51v down to 40.9v under load...

I remember reading somewhere to expect a 1v drop per 100 amps. On flat pavement the most I've ever pulled in my cart was 304 amps, so a 3v drop would be right for my cart on my terrain. but hills make things different and if you are running four 12v batteries they don't have the same reserve capacity as six 8v or eight 6v so you may get a little more drop per 100 amps... Having said that, dropping 10 volts sounds like shot batteries (or possibly dry batteries or shot battery cables).
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Old 03-09-2022, 01:59 PM   #8
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Default Re: 48v rxv 51v down to 40.9v under load...

Quote:
Originally Posted by bronsonj View Post
I remember reading somewhere to expect a 1v drop per 100 amps. On flat pavement the most I've ever pulled in my cart was 304 amps, so a 3v drop would be right for my cart on my terrain. but hills make things different and if you are running four 12v batteries they don't have the same reserve capacity as six 8v or eight 6v so you may get a little more drop per 100 amps... Having said that, dropping 10 volts sounds like shot batteries (or possibly dry batteries or shot battery cables).
The 1V/100A is for a 36V pack made from 225AH 6V batteries and is for just the batteries. Cables, connections and contacts will double that, or more.

It is 1.5V/100A for a 48V pack made from 170AH 8V batteries, so it would be greater for 150AH 12V batteries.

In a nutshell, the normal voltage drop per 100A depends on the storage capacity of the batteries, the SoC (State of Charge) and the temperature of the battery, plus the resistance of the cables, connections and contacts.
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Old 03-09-2022, 02:13 PM   #9
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Default Re: 48v rxv 51v down to 40.9v under load...

Thanks for the info. These are Trojan T-1275's, serveral years old.

all the batteries rear around 12.5 except one is at 12.84
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