Jump to content

Upgrading UPS from 7AH to 12AH


phLOx

Recommended Posts

6 hours ago, P1000 said:

Did you measure it with a scope, because being modified sine, the current won't be constant and a normal multimeter will probably give a pessimistic reading.

Quite right. I redid the measurements with a true RMS meter and a Fluke i30s current clamp

The AC volts were 234V and the current 0.65A = 152W

The DC current was 18A and battery 12V = 216W

 

Link to comment
Share on other sites

With a full house, of more devices connecting, the battery runs dry before the 150 minute mark I have noticed. Hopefully at the end of the month I can mod the 12AH battery in and monitor the situation from then to see what type of charge stays behind after 150 minutes.

Link to comment
Share on other sites

On 2020/03/10 at 2:23 PM, phLOx said:

I have three devices to run from UPS power during Stage 1-4 loadshedding.

D-Link DSL-2750U (12V, 1A), TP-Link Archer C20 (9V, 0.6A), Raycore CPE (Not 100% sure about model but believe the PSU is also 9V, 06A)

I have a Mecer ME-650-VU (Rated at 360W max output) UPS. It has a single 12V, 7AH battery. I do not know how much power the UPS subsystems use to monitor and power itself, but I (hopefully over-) guesstimated no more than 12 Watt

Do you still have the same load as your initial post??

Link to comment
Share on other sites

This is an intersting topic.

Further to the wise words of the posts earlier, the small UPSs are not designed to run for hours... hence the short run times that phLOx is getting. This is normal !

I too have replaced the batteries on UPSs with larger capacity ones. What nobody has mentioned yet is that the heatsinks on the MOSFETs  small UPSs while running on battery are rather small. They are only designed to handle the temperature rise for a 7AH battery which would have gone flat before any excessive temperatures were reached. It is easy to check this, open the UPS and see if the heatsinks are blocks of aluminium or the better solution of heat sinks with fins. The block of aluminium is good for drawing heat away from the semiconductors (but only for a short time before the 7AH battery has gone flat). The finned heatsink is better for continuous operation as the heat will be better able to be removed from the MOSFETS. If you increase the capacity of the battery eg going from 7AH to 12AH or 100AH it will work but beware the temperature rise which could lead to failure of the MOSFETS. I have converted a number of UPSs for fun to run on 18AH batteries and added in fans to cool the finned heatsinks. Those blocks of Al don't cool well enough.

It was mentioned earlier about the charger inside the UPS. Yes the charger will need to work harder and longer to charge the higher capacity battery. Typically the small UPSs use a LM317K voltage regulator to charge the battery and they are on a very skimpy heatsink (yes skimpy  because it was only intended to charge a 7AH battery 😬). I had one of those on a 18AH battery and the PCB was scorched where the regulator was situated due to the high temps.

Finally you do get UPSs that are designed to take massive battery banks eg the APC SmartUPS which you can add multiple external

banks of batteries. These UPS are designed to handle extended run time ie  the heat of charging and when running on batteries. Also they charge at a high current - on mine the UPS fans switch on when charging at a high current. 

Each one of the external battery boxes takes 4x 18AH batteries (this UPS is a 24V model).

The cost to replace the batteries is rather high so mine is now fitted with 2x 100AH gel batteries. Yes next time to be replaced with Lithium battery.

 image.png.aa8ff42a3fcd93f4d0366daa5a49a99f.png

Link to comment
Share on other sites

27 minutes ago, GreenMan said:

LM317K voltage regulator

Oooh, I remember those! I think I might still have one in a parts bin somewhere. Those things were the bomb back in the day for building adjustable power supplies. Many of the commercial ones had a big old heatsink on the back with the TO3 canister bolted to it. I used the LM317T (rated 1.5A) a lot more often for lower power uses. Those things were excellent... but being linear regulators they made a lot of heat.

27 minutes ago, GreenMan said:

Those blocks of Al don't cool well enough.

It's not only the FETs. The transformer itself heats up as they are often underrated too, so once you deal with the cooling issue on the FETs, that is usually the next thing that needs attention.

If you have the time, you could watch this (old, sadly no longer making videos) series of converting an APC UPS to inverter (including blowing it up in the middle) 🙂

Edit: In the second video he does the temperature tests showing what happens.

Edited by plonkster
Link to comment
Share on other sites

I agree with all of the posters here re running DC products on DC power.

I'm in the router industry we are one of the distributors for things like TP-LINK, Mikrotik, Ubiquiti etc... so I can confidently say I know the stuff well :D

Your best bet from a price / performance point of view is to get a 12v battery and charger and then run all of the 12V stuff directly off the battery, for other voltages get step up or step down converters, these are quite cheap and readily available.

I have around 120ah worth of batteries which run 4 routers, my home automation Intel NUC (have a step up to 19v for this although it does run off 12v but I've done this more for power filtering), efergy energy monitor, fibre router, 2 x outdoor routers for a ptp link,  it is capable of keeping this equipment up for days.

Most routers are either 9V or 12V, the 9V routers can almost all run at 12V without issue, products like Mikrotik have a very broad input voltage range of anywhere between 9v and 56v so can run on a plethora of battery configurations.

Its not a good idea to increase the capacity of the UPS you will have charge & heat issues they are not built to be expanded (well not the small entry level units), UPS in general are not designed for this type of work, they are designed to keep things like PC's powered up until a generator / inverter kicks in not to power a host of devices for hours. Unfortunately this is the perception and tons of people are rushing out and buying UPS' to act as inverters and with the frequency and level of load shedding we're faced with it is damaging the UPS and they're not even seeing their 1 year warranties out.

I'm happy to share pics of my setup and offer advise, I've been running on batteries for over 10 years with no issues. 

 

Link to comment
Share on other sites

23 hours ago, Jatho said:

I agree with all of the posters here re running DC products on DC power.

<SNIP>

Your best bet from a price / performance point of view is to get a 12v battery and charger and then run all of the 12V stuff directly off the battery, for other voltages get step up or step down converters, these are quite cheap and readily available.

<SNIP>

I'm happy to share pics of my setup and offer advise, I've been running on batteries for over 10 years with no issues. 

 

So, what I'm hearing people here say is something like:

 

Mains ==> battery charger ==> 12v Battery ==> buck converter (If needed) ==> fuse ==> connector for router/ont  etc.

 

I have questions 😉

I think a lot of answers depend on load so lets define that:

1x switch (Dlink DGS-1008A)  -  4.8w max

1x ont (Huawei EchoLife HG8040H ) - 7.5w max

1 x AP ( Asus 86U ) - 15w max

1x Raspberry pi 3b+  - 2w max

 

So - I'm looking at around 30w, and  want it to last for 4.5 hours (stage 4 in my area).

So the battery needs to 30w * 4.5w * 2 (don't want to discharge it more than 50%) = 270 watt hours / 12v = 22AH. (Yeah - I've ignored inefficiencies as well - so, lets jack up the battery requirement to 30AH just in case).

Assuming my back of the envelope calculations are right - what charger, and what battery would people recommend? (We probably need to factor in the fact that in the load 4 schedule, we sometimes only have 11 hours of charging time before the next cycle.)

 

I'm curious as to what the fuse setups would look like as well?

 

A bonus question - how would one monitor the performance of this setup - I get battery levels from my ups - I'm guessing I could monitor the battery level via the pi somehow?

 

 

Link to comment
Share on other sites

  • 2 weeks later...
On 2020/03/19 at 11:59 AM, Orange said:

A bonus question - how would one monitor the performance of this setup - I get battery levels from my ups - I'm guessing I could monitor the battery level via the pi somehow?

I know it can be done with Arduino, so Pi should also be able to facilitate this.

It entails having the device (pi, arduino) monitor and log the voltage it receives. Do this from a fully charged battery all the way down to a depleted one.
Boot the system back up and look at the minimum and maximum voltages received. You now know the limits of the battery in its current setup, and can use the lowest as 1% and the highest as 100% capacity for your system, which is easy to display at all times through a display module for instance.

This is how I understand it, but you may require some searching online to confirm this method.

Link to comment
Share on other sites

7 hours ago, phLOx said:

I know it can be done with Arduino, so Pi should also be able to facilitate this.

The ATMEGA chip in the Arduino has an ADC (analog to digital converter) while the Pi doesn't, so you'd still need some kind of interface between the two. Cheapest is likely to just use an arduino and a serial link to your pi.

Voltage is of course not a great measure of state of charge, but under a constant load it's not too bad.

Link to comment
Share on other sites

  • 2 weeks later...
On 2020/03/19 at 11:59 AM, Orange said:

So, what I'm hearing people here say is something like:

 

Mains ==> battery charger ==> 12v Battery ==> buck converter (If needed) ==> fuse ==> connector for router/ont  etc.

 

I have questions 😉

I think a lot of answers depend on load so lets define that:

1x switch (Dlink DGS-1008A)  -  4.8w max

1x ont (Huawei EchoLife HG8040H ) - 7.5w max

1 x AP ( Asus 86U ) - 15w max

1x Raspberry pi 3b+  - 2w max

 

So - I'm looking at around 30w, and  want it to last for 4.5 hours (stage 4 in my area).

So the battery needs to 30w * 4.5w * 2 (don't want to discharge it more than 50%) = 270 watt hours / 12v = 22AH. (Yeah - I've ignored inefficiencies as well - so, lets jack up the battery requirement to 30AH just in case).

Assuming my back of the envelope calculations are right - what charger, and what battery would people recommend? (We probably need to factor in the fact that in the load 4 schedule, we sometimes only have 11 hours of charging time before the next cycle.)

 

I'm curious as to what the fuse setups would look like as well?

 

A bonus question - how would one monitor the performance of this setup - I get battery levels from my ups - I'm guessing I could monitor the battery level via the pi somehow?

 

 

 

Sorry for the late reply, I really need to look at my notification settings...

So your calculations are correct, but I'd rather over spec the system as the costs are somewhat negligible in the bigger scheme of things and chances are when you realise how many other DC devices you have in your house that would be nice to have powered up during load shedding you'll quickly amass quite a nice draw on your battery backup system. To gibe you an idea my DC backup system started life as a backup to my routers (internet only) but soon I added my home automation as well as my NAS, these are both pretty power hungry and more than tripled my draw, luckily I had a pair of 100AH batteries laying around so upgraded the batteries.

For your system I'd say go for the 35ah battery you quoted but if you think you'll add more devices double it, it will increase the lifespan considerably.

 

On 2020/03/19 at 12:08 PM, Orange said:

Ack - the Asus wants 19v - so it's either go to a 24v system, or a step up convertor. probably a stepup - this one https://www.botshop.co.za/product/150w-boost-converter-dc-dc-step-up-module/  Conversion efficiency: 94% (measured at Input 16V, output 19V 2.5A) - probably less @ 12v to 19v.

Those step up modules are excellent for the money, I use one for my Intel NUC and a more expensive Meanwell for my Mikrotik although in hindsight I'd be happy to have used the former for my Mikrotik. While you're at it you may as well add a 12V to 5V USB converter, these too are very inexpensive and you'd then be able to power or charge 5V USB devices.

EDIT, don't run 24V you're looking for a world of problems designing the system this way if the majority of your systems are 12V (which they will be), it is also a lot more expensive plus you'll need to add some sort of battery management system, use step up convertors they're inexpensive and are generally very well made. 

 

 

Edited by Jatho
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...