84v low voltage cut off and...

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Highxtech

10 mW
Joined
Jul 24, 2018
Messages
23
Quicky question,

I've got 7 12v 20ah batteries in series (84v 20ah total)

What should I set my controller to for low voltage cut off?

Also is the low voltage cutoff value suppose to be measure while on the throttle (under load) or when I'm stationary (no load)?

And last question, my controller (app) says my controller is at say 90v, but my voltmeter (connected to the controller) will read 94v and my multimeter 93v, which should I deem as more correct?

Thanks a ton!
 
Highxtech said:
Quicky question,

I've got 7 12v 20ah batteries in series (84v 20ah total)

What should I set my controller to for low voltage cut off?
Depends on your battery chemistry.

Also is the low voltage cutoff value suppose to be measure while on the throttle (under load) or when I'm stationary (no load)?
It measures it all the time, so when you twist the throttle and you have voltage sag and the voltage dips below your lvc for a given amount of time, the controller will cut the power


And last question, my controller (app) says my controller is at say 90v, but my voltmeter (connected to the controller) will read 94v and my multimeter 93v, which should I deem as more correct?
What controller do you have? Also whats the parameter of the 90V cont app reading? What exactly is 90V?

Thanks a ton!
Click to expand...
 
Thanks for the response,

it's 7 SLA batteries

It's one of the Bluetooth controllers (yuyangking app), 90v is just an example but. It generally read 3v-5v power than the voltmeter, Im just not sure if I should set the cutoff based on the voltmeter or what the controller tells the app it sees
 
You should be setting it for what the actual voltage at the battery is... The point of the cutoff is to protect the battery, so even if the system volt display says one thing, it's the battery level that matters.
Having run a 6 sla setup for a lot of miles, you will still need to be checking each individual 12v block pretty often and balancing them with a 12v charger to get any reasonable life span and range out of them. Otherwise the weakest one starts crashing early, and if not fully recharged starts sulphating, making it worse. Meanwhile the strongest ones start going crazy high during charging, as the charger just sees the total voltage, so one or two start peaking at 15 or 16 volts.
When you put your ear against one and hear it bubbling inside that's bad.... Personal experience tip for you :)
 
Your app reads 90V which is your battery voltage at full charge or close to full charge on your 84V(nominal) battery.
7 x 12V = 84V which is a nominal value, or shall we say average.
7 x 13.4V = 94V which is your max or near max battery voltage. I thought SLA's were 14.4V(max) but I guess it would depend on the battery itself. This site says Float Charge is 13.5V.



When you connect up your volt meter to the battery leads (at the controller) you read 94V with volt meter and multimeter will read 93V. Is that the case?

If you have a decent multimeter rather then a el-cheapo one, I'd trust that reading.

You ever thought about upgrading to Lithium Ion batteries?
It would be a very smart upgrade!
 
So I'll set the controller to cutoff at around 73v, so it'll cut off if I'm in the throttle. It should be 3-4v higher since the app reads low

I have a pretty good multimeter so I'll trust that over the app

The charger I have tops out at 101.8v (84v smart charger)

I've definitely considered lithium but I'd want an 84v 30ah setup which would run a lot more money than I'm willing to spend right now
 
markz said:
When you connect up your volt meter to the battery leads (at the controller) you read 94V with volt meter and multimeter will read 93V. Is that the case?

If you have a decent multimeter rather then a el-cheapo one, I'd trust that reading.
Click to expand...

Yes that is the case. If for example the multimeter reads 90v the voltmeter reads 89v and the controller on the app reads 84v
 
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