will it hurt my motor to run on low voltage?

[mike777]

I have a 07 TXT "series" with original T105 batts in from 07after a charge the next day it reads 38volts maybe a little more pack voltage, I know I need new batts, I'm just wondering if it will hurt the motor running on sporadic low voltage
the individual batts read 6,39, 6,37, 6.41, 6.25, 6.34, 6.35, the 6.39 is a newer replacement trojan,(other 1 cracked over winter) I know its all over the charts,
it runs along at about 12 mph on flat ground , when doing so the voltage drops to 35.4 , alot of the time its around 36.5( scottybs in dash batt guage) on steep hills it drops to 33.5 sometimes lower and of course the mph drops considerably,once it flattens out the volts go back to 35.4- 36.5 again, if I stop the cart within 5 min it will climb back to 38v, I took a loop last night a couple hills , mostly flat avg 10 mph, went about 8-9 miles got back the pack voltage was around 75-80%, put it on charger it was fully charged and shut off in a couple hrs.
I'm planning on going 48 volts soon with all the upgrades except motor, so not too worried about anything but the motor, will I have any probs running it in the time being? thanks for the replies
Mike

[scottyb]

Remember this about low batteries. Volts plus amps = watts or X amount power for a given task. Chew on that for a little bit.
If we take away volts, but X or the given task remains the same then Amps must be increased to make up the watts needed. See picture of Watts below.
This is all well and good except that amperage flow creates heat. So the more amps used the hotter the motor will get, See picture of hotter below.
The same heat shows up in the controller , solenoid, F&R - basically the whole system heats up, See pic of heated up system below.

So - in review, don't do it. .............. Your motor will get too hot and your wife will kill you.
See pics of your motor is getting too hot, & your wife will kill you below.

[Thatsme?]

Even I can understand that picture

[gornoman]

Originally Posted by Thatsme?

Even I can understand that picture

Me too. Come on, BREEZE!

[Sir Nuke]

Mike......looking at your post, the only thing that is a bit off is ONE battery is a tad low... you stated that after you "07after a charge the next day it reads 38volts maybe a little more pack voltage" that is perfectly normal.....as 100% is 38.3v....so there is no problem at all. and you were giving us readings from the digital meter WHILE you are running, those readings are PERFECTLY NORMAL READINGS. And the fact that stated "if I stop the cart within 5 min it will climb back to 38v" that too is perfectly normal.....AND you stated "I took a loop last night a couple hills , mostly flat avg 10 mph, went about 8-9 miles got back the pack voltage was around 75-80%, put it on charger it was fully charged and shut off in a couple hrs." this too is perfectly normal and it seems your pack is in pretty good shape considering its age.


So mike......you truly don't have a problem.....no problem at all.

[mike777]

Originally Posted by Sir Nuke

Mike......looking at your post, the only thing that is a bit off is ONE battery is a tad low... you stated that after you "07after a charge the next day it reads 38volts maybe a little more pack voltage" that is perfectly normal.....as 100% is 38.3v....so there is no problem at all. and you were giving us readings from the digital meter WHILE you are running, those readings are PERFECTLY NORMAL READINGS. And the fact that stated "if I stop the cart within 5 min it will climb back to 38v" that too is perfectly normal.....AND you stated "I took a loop last night a couple hills , mostly flat avg 10 mph, went about 8-9 miles got back the pack voltage was around 75-80%, put it on charger it was fully charged and shut off in a couple hrs." this too is perfectly normal and it seems your pack is in pretty good shape considering its age.


So mike......you truly don't have a problem.....no problem at all.

thanks for the input, strange that you and Scottyb are telling me opposite opinions, why does it lose so much momentum and crawl up the hill slowly?

[Sir Nuke]

actually if you decipher what he wrote, its correct. You don't want to run your motor with a low pack charge/voltage, it will hurt your motor if/when it over heats. BUT YOU don't have a LOW Pack Charge/voltage. What you have to remember, is that the reading you are seeing on the meter is RUNNING voltage, not the true voltage in the pack. THAT is what you see when or after you stop, that is what should be truly concerned about.

[MuckSavage]

I measured my pack this morning after a 12 hr charge and had similar readings. 38.4v total pack. 6.54, 6.36, 6.40, 6.43, 6.42, 6.34. I was told a while ago this was okay. Not perfect, but suitable. I'm going to attempt to even out the packs utilizing a 6v charger on individual batteries. Glad to see our #'s are similar & you got good remarks from the gurus here!

[JohnnieB]

There are a lot of things going on here and they do overlap, so it does get confusing.

Let's start with Amps, Volts, Watts and Heat.
The picture of Watts may generate some heat for the viewer, but she might get a chest cold wearing that dress.

Amps X Volts = Watts
It takes the same number of Watts to move the cart from Point-A to Point-B regardless of the battery pack voltage.
If the pack voltage is lower, it takes more Amps, if the pack voltage is higher, it takes fewer Amps.

A motor converts Watts into motion (Torque) and/or heat (Temperature rise).
Also, if there is any resistance in the high current cables, connections and contacts, some of the Amps flowing through them is converted to Heat and there is a voltage drop across that component. (Note: This voltage drop steals voltage that ought to be applied to the motor, so it doesn't spin as fast.)
Heat generated by resistance is exponentially proportional to the Amps flowing through it (Amps X Amps X Ohms = Watts), so a cart running a 48V voltage battery pack will run cooler than a cart running a 36V battery pack.

------------
Battery voltage, there are three of them to contend with and you have to understand which one you are measuring to understand what it means.

At-Rest voltage: This is the only one that can be used to accurately estimate the battery's SoC (State of Charge). It does not exist until the battery has rested about 12 hours after being charged or about half an hour after being used (discharged). If one of those two criteria isn't met, the SOC estimate is not valid.

During charge and discharge, the chemistry interface (Where sulfuric acid meets the lead and lead dioxide of the plates) becomes hyper or hypo active (aka stratified) and it takes time for it to equalize with the rest of the chemistry. After being charge, it is commonly called a surface charge and takes about 12 hours to deplete via the self discharge process. The opposite stratification occurs during discharge, but only takes about half an hour to equalize. (Actually, the voltage continues to rise after discharge for an hour or more, but only by hundredths of a volt after the first half hour, so half an hour rest suffices for SoC estimates)

On-Charge voltage: To pass a charging current through a battery, the voltage applied to the battery must be higher than the At-Rest voltage.
As a battery is charged, the On-Charge voltage increases. Technically, a battery is not fully charged until the On-Charge voltage ceases to increase, however most automatic chargers shut off at a preset voltage that is considered to be close to fully charged for most batteries.

Under-Load voltage: When Amps are being drawn from a battery, the battery's voltage decreases. The more amps being drawn, the lower the battery's voltage drops to.

This is why the voltage on a DVM battery meter bounces all over the place while cart is being driven. If you also had an Ammeter installed, you would see the the battery voltage was inversely proportional to Amp flow.

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Hope this helps more than it confuses.

[MuckSavage]

More great info johnnyB. Thank you. I need to add that I read my voltages only 15 minutes after disconnecting the charger. I should add that the charger had been on for 12 hours, but was still reading 10A. Is this odd? Is it caused by the imbalance between batteries?