Slow Charge

[Anonymous user]

Hi Everyone,

I have two UPS SU3000RMXL backups and each unit is connected to three external batteries. I had a power outage yesterday and I am quite concerned that it took one of the UPS units 8 hrs to reach a full charge (where the other unit charged more quickly). The powerload on both units is the same (three bars on the display).

Why does the UPS take a long time to charge?

Thank you,
D

[Anonymous user]

Hello,

Is it OK to install 6 external batteries to one "command unit" (aka SU3000RMXL)?

Thanks,
D

[Anonymous user]

ddasilva99 wrote:
Hi Everyone,

I have two UPS SU3000RMXL backups and each unit is connected to three external batteries. I had a power outage yesterday and I am quite concerned that it took one of the UPS units 8 hrs to reach a full charge (where the other unit charged more quickly). The powerload on both units is the same (three bars on the display).

Why does the UPS take a long time to charge?

Thank you,
D

Because you have external batteries connected. The charging circuit is current limited, so more batteries you have connected, longer it takes to charge.

[Anonymous user]

Its also advised that you use batteries that are generally around the same age too. Same age being roughly within 1 year of one another. ie. Don't mix 3-4 year old batteries with new ones.

[Anonymous user]

Hi,

Thank you for your post. Could you please explain why the same UPS unit (same setup of three batteries) charged much quicker? Is it normal for 3 external batteries + 3000XL take approx 8 hrs to charge?

Thank you,
D

[Anonymous user]

ddasilva99 wrote:
Hi,

Thank you for your post. Could you please explain why the same UPS unit (same setup of three batteries) charged much quicker? Is it normal for 3 external batteries + 3000XL take approx 8 hrs to charge?

Thank you,
D

I don't work for APC and I can't find that information on their site, but that seems pretty normal. Because of the way lead acid battery is charged, it reaches 80-90% and it's the top off charge that takes a long time and based on measurements I've taken, continues even after the capacity indicator reads 100%.

3 indicator means your UPS is loaded anywhere from 50-67%, so if one unit is loaded to about 51% and the other one to 66%, the drain on battery will obviously be different and usually, the drain on battery is greater than increase in load (i.e. double the load results in runtime less than half)

Use a 940-0024C cable and connect to computer. Connect to UPS with HyperTerminal 2400 bps Xon/Xoff mode.

Send shift-y and wait for "SM" response.
shift-p reports actual load in percent. Multiply by 24(for your unit) to get the actual combined load wattage (running off of that particular unit).
"f" reports battery capacity in percent, although this isn't always accurate.
"z" to reset everything to factory default.

[Anonymous user]

Hello,

How old are the two units? Are they both the same age or is one older than the other?

Do they also have the same exact type of batteries, or does one have larger extended batteries than the other?

A Smart UPS, by itself with no external batteries, will take about 3-5 hours to recharge fully. Each extended run battery could add upwards of 2-3 hours, depending on the size, to recharge fully. If the unit with three extended batteries recharged in 8 hours, this sounds normal.

[Anonymous user]

That shouldn't be a problem. Just keep in mind that you will have a very long charge time as stated in the previous posts. Also, If you are using this UPS to gracefully shutdown any computers, you will want to make sure you program the UPS to know how many external battery are attached so it will calculate the correct runtime. This would be done through whatever PowerChute software you are currectly using. If you are not using this UPS with PowerChute software then don;t worry about programming the UPS with the number of batteries.

[BillP · Accepted solution]

The recharge rate of the batteries is roughly 10x the discharge. So it is normal to have an 8 hour recharge. Additionally, the batteries will charge to 80% rather quickly but it is the last 20% that takes the time. If the batteries are more than 3 years old you might want to consider getting the batteries replaced and the unit recalibrated.