UPS (APC 3000) Beeping/Saying low battery but lots of volts from Charge controller.

[Will-UK]

(APC 3000) UPS wired up to lots of external (still sealed lead acid) batteries.

I'm sure it has some kind of intelligent gubbins in it which KNOWS it has not been connected to AC power for a while, because despite it showing plenty of volts on my battery pack, (solar charge controller pumping in about 56 volts) the UPS still flashes the one bar of battery LED and beeps . Only when I give it some grid power for a few hours does it shut up.

Anyone else had this problem? Its a brilliant machine apart from that and powers all kinds of stuff here like washing machine, fridge freezer, basically almost everything, as long a it is not all at once!

If i power the whole thing down and hold the 0 button it resets itself and when I turn it back on it shows full battery. (then after an hour of using it it goes back to saying the battery is flat even though its at full voltage)

Charging it with an Outback FM80 and 1500W of PV.

Thanks!

[SunEagle]

(APC 3000) UPS wired up to lots of external (still sealed lead acid) batteries.

I'm sure it has some kind of intelligent gubbins in it which KNOWS it has not been connected to AC power for a while, because despite it showing plenty of volts on my battery pack, (solar charge controller pumping in about 56 volts) the UPS still flashes the one bar of battery LED and beeps . Only when I give it some grid power for a few hours does it shut up.

Anyone else had this problem? Its a brilliant machine apart from that and powers all kinds of stuff here like washing machine, fridge freezer, basically almost everything, as long a it is not all at once!

If i power the whole thing down and hold the 0 button it resets itself and when I turn it back on it shows full battery. (then after an hour of using it it goes back to saying the battery is flat even though its at full voltage)

Charging it with an Outback FM80 and 1500W of PV.

Thanks!

First thought is that those batteries can no longer hold a full charge. They can get back to full voltage but under load they are empty.

A UPS is designed to provide a lot of power for a short period of time due to the loss of grid power. They are not designed to do this every day so the total number of cycles is much lower than a true deep cycle battery. While they might have a 5 year life most of that time the batteries are just sitting there full dumb and happy.Make them work a lot and they will die a quick death.

[Will-UK]

Thanks , the battery bank that I have it hooked up to is huge (300AH, 48V, 14500w/h)


The original (internal ) batteries would have been about 600w/h

I could always ignore the battery LEDs and unsolder the beeper, but it would be nice to know if the unit is programmable via serial port etc, and if so if any readers on here have done that.

[SunEagle]

Thanks , the battery bank that I have it hooked up to is huge (300AH, 48V, 14500w/h)


The original (internal ) batteries would have been about 600w/h

I could always ignore the battery LEDs and unsolder the beeper, but it would be nice to know if the unit is programmable via serial port etc, and if so if any readers on here have done that.

Well. There is your problem. You battery bank is huge and looks like quite a bit of parallel sets. More than likely you have a few bad cells which is keeping your bank from being equally charged because of the "bad" apple in the bunch.

I am also wondering if those wires are really big enough to pass the 30amp charging current to all the batteries without some losses.

[Will-UK]

Hi there are 8 batts in parallel, and then 4 lots of those.

So 30A would only actually equate to 3.75A per battery, even so they have a 40A cable/fuseholder and 20 amp fuse. Plenty.
Where the current goes in and out of each pack of 8 that's where I have the thick cable.

The battery pack is actually working great, it is literally the UPS that was irritating me as it appears to be basing its bleeps on runtime and load, rather than actually looking at the battery voltage. The battery pack has perfect float voltage and powers all my loads all night without any problem.

[SunEagle]

Hi there are 8 batts in parallel, and then 4 lots of those.

So 30A would only actually equate to 3.75A per battery, even so they have a 40A cable/fuseholder and 20 amp fuse. Plenty.
Where the current goes in and out of each pack of 8 that's where I have the thick cable.

The battery pack is actually working great, it is literally the UPS that was irritating me as it appears to be basing its bleeps on runtime and load, rather than actually looking at the battery voltage. The battery pack has perfect float voltage and powers all my loads all night without any problem.

Sounds like the UPS logic is based on one type of battery size and your system uses a much bigger system. There could be some type of incompatibility that might be resolved with reprogramming the UPS measurement logic.

I will go back and say your biggest problem is how the batteries system is wired.

Sound like you have 32 x 12V batteries that are wired 4 sets of 8 in parallel. Not the best way to wire them. I would first put 4 in series to make a 48volt set and then wire those sets in parallel but no more than two or 8 batteries total. More than 2 sets in parallel will cause charging and discharging issues no matter what size wire or how they are wired.

[Will-UK]

Thanks.

The reason for wiring the batteries that way was so that there are only 4 lots of 12, rather than 8, meaning i only have to test 4 potentials to check they're balanced, and easier to tweak if they do go out of balance a bit.

Is there a reason why this is not ideal performance-wise? Would each bank of 8 not just behave as one large 300Ah 12v battery?

Not had any problems with it so far, I ran my place for 72 hours on it as a test recently (no solar input) and although they did run down quite a lot (46V) the power was still on.

[SunEagle]

Thanks.

The reason for wiring the batteries that way was so that there are only 4 lots of 12, rather than 8, meaning i only have to test 4 potentials to check they're balanced, and easier to tweak if they do go out of balance a bit.

Is there a reason why this is not ideal performance-wise? Would each bank of 8 not just behave as one large 300Ah 12v battery?

Not had any problems with it so far, I ran my place for 72 hours on it as a test recently (no solar input) and although they did run down quite a lot (46V) the power was still on.

There is a website that shows different battery wiring techniques listing both the pros and cons. I don't have it right now but some other people can provide it if you are interested.

[DanS26]

http://www.smartgauge.co.uk/batt_con.html

[SunEagle]

http://www.smartgauge.co.uk/batt_con.html

Dan

Thanks for finding the website.

[sensij]

There is no way that entire set is balanced, nor can you tell that 32 batteries are balanced with only 4 measuring points. If you sketch out the actual hookup, it will be clear. I think the best chance of balancing them would come by connecting each of the 8 in parallel to a heavy busbar with wire that is exactly the same length, and then connect the busbars in series to get the voltage. I bet if you measured the SG on each of the batteries, the numbers would be all over the place.

If that whole bank is only 300 Ah, are you saying that each individual battery is only 37.5 Ah? If so, the 3.75 A charge current you are providing is appropriate, at least.

I'm not sure what all that costs, but if you just put 8 x 6 V batteries in series, you'd have a much better bank. A bank built from something like the Trojan L16RE-A, 325 AH, would cost <$3000, if you can get them.

[Will-UK]

Thanks for your inputs

The bank is connected like so, not the ultimate way but I was using what I had and minimising cable. Every pair of batteries has a fuse.

(1 layer)


I've knocked up a diagram for the whole system tonight.

Here..

[inetdog]

For Lithium batteries, the ladder type interconnection (make parallel groups and then put them in series) is common, but for lead acid it is much more common to build series strings first and then put them in parallel. Given the resistance and voltage versus SOC curves of lead acid, the latter arrangement works out better in terms of balanced charging without thermal runaway.

[Will-UK]

There is no way that entire set is balanced, nor can you tell that 32 batteries are balanced with only 4 measuring points.

How can batteries in parallel go out of balance if equally connected? This thread is about tips on how to reprogramme the UPS to not give a runtime warning. The battery pack works great!

I'm not sure what all that costs, but if you just put 8 x 6 V batteries in series, you'd have a much better bank. A bank built from something like the Trojan L16RE-A, 325 AH, would cost <$3000, if you can get them.

This bank cost me only £400 (second hand approx 2 years old) hence giving it ago. I've even got another bank the same size (not wired up yet, possibly going to build a mobile solar setup with those..)


The UPS was a freebie.

The major expenses have been the panels and the charge controller

[SunEagle]

No matter how well you think you have wired a large set of batteries you will still have higher resistance at a few of the connections. Even a few ohms difference will change the amount of current being sent down the wires to charge or discharge the batteries. If the current isn't the same throughout the wiring then you get imbalance. Eventually one or more of the batteries get too little or too much charge current.

And you know what they say "one bad apple spoils the bunch". The same goes for a battery system.