Modifying a RCT2000VA UPS with an External charger

[savage]

guys here is how to connect a 220vac / 12vdc relay so that it DISCONNECTS the 100Ah battery from the UPS when the MAINS comes back ON. allowing your normal battery charger to charge the 100Ah battery.

the UPS battery charger will still charge the UPS's battery.

Bad idea.

1) The UPS will not switch back to utility power immediately, thus, you run the risk that you can actually kill the power to your load,
2) It's a VERY bad idea to connect/disconnect a battery whilst it's under load,
3) Most relays are only rated for 15A across the contacts. Batteries uses much higher currents. Your relay contacts will burn, and eventually it will either be "stuck" in a off position, or in a on position.

A 100A+ Contactor, with a delay timer may be a better option.

 

[spiff]

Bad idea.

1) The UPS will not switch back to utility power immediately, thus, you run the risk that you can actually kill the power to your load,
2) It's a VERY bad idea to connect/disconnect a battery whilst it's under load,
3) Most relays are only rated for 15A across the contacts. Batteries uses much higher currents. Your relay contacts will burn, and eventually it will either be "stuck" in a off position, or in a on position.

A 100A+ Contactor, with a delay timer may be a better option.

the UPS has its's own batteries - I don't see how this will effect the 10-20ms change over time? I'm just switching off the extra 100Ah battery not interfering with the normal use of the UPS

so you're saying that even if I connect the 100Ah direct to the UPS it won't carry the current?

 

[Gnome]

The biggest problem which hasn't been mentioned is you are bridging two battery banks with each other.

They are sitting at different potentials and then you want to connect them using a relay?

Have you ever seen those warnings on remotes that say, don't mix batteries of different types?
You are doing that, but with huge ass batteries that are being charged at different rates by different chargers.

You would need to switch out the internal battery when you switch in the bigger battery bank to be safe.

Overall super complicated setup.

 

[spiff]

thanks Savage & Gnome for the heads up.

however Joe_Moer seems to have got it to work

OK, this is how I ran a similar setup at work for a couple of years without any problems. The extra battery pack (12V or 24V depending on your UPS) is connected in parallel to the UPS internal pack via the normally open contacts of a 220 Volt relay. The relay is fed from the mains supply, thus as long as there is mains the extra batteries are disconnected from the UPS internal battery pack. The ups chargers its own battery pack and the external pack is connected to a separate charger. When the mains fails the relay drops out and connects the external pack to the internal pack and Bob's your Auntie.

so maybe he can explain how he got it to work?

 

[AfricanTech]

Not really. Just have to know what you are looking for.
Chargers can be disconnected...without damaging things. Very hard over the Net though.

In front of me = sorted. Difficult on Forums or away from a hands on approach.

Gotta see the circuitry in front of me.....

As a lay person when it comes to electricity, it's damn scary

 

[savage]

so maybe he can explain how he got it to work?

No one is saying it won't work - frankly, it will work just fine... Initially.

If you want your batteries to only last 6 odd months, then go right ahead and do this. If you want your batteries to last (as long as they possibly can), then you need to treat them with the respect and proper maintenance that they require.

I'm sure you are aware of the cost of batteries, and if you can afford to fsck them up and replace them constantly, go for it

 

[Gnome]

No one is saying it won't work - frankly, it will work just fine... Initially.

I wouldn't even say that it will work initially. Batteries of different types have different float and discharge voltages. By bridging them you are effectively causing one battery bank to discharge into another. I mean they are even being charged differently. When they connect they almost certainly won't even have the same voltage.

If you start mixing batteries with different chemistries (eg. AGM and Lead Acid Calcium), they have completely different discharge characteristics. One battery bank ends up "charging" the other battery bank. The relay is going to be pushing massive amps between the batteries because you are dealing with huge batteries that want to equalize. This can also cause the battery to overheat and rupture.

Even if you are running the same type of batteries 100amp relays are incredible expensive.

Overall I don't believe it is safe. But what do I know, some guy on the internet said it worked for him.

So far R14 resistor is the safest option in my opinion and actually shows promise because according to the technical document on this forum, it can actually work. No need for unsafe bridging relays that are complicated, etc.

 

[spiff]

No one is saying it won't work - frankly, it will work just fine... Initially.

If you want your batteries to only last 6 odd months, then go right ahead and do this. If you want your batteries to last (as long as they possibly can), then you need to treat them with the respect and proper maintenance that they require.

I'm sure you are aware of the cost of batteries, and if you can afford to fsck them up and replace them constantly, go for it

I wouldn't even say that it will work initially. Batteries of different types have different float and discharge voltages. By bridging them you are effectively causing one battery bank to discharge into another. I mean they are even being charged differently. When they connect they almost certainly won't even have the same voltage.

If you start mixing batteries with different chemistries (eg. AGM and Lead Acid Calcium), they have completely different discharge characteristics. One battery bank ends up "charging" the other battery bank. The relay is going to be pushing massive amps between the batteries because you are dealing with huge batteries that want to equalize. This can also cause the battery to overheat and rupture.

Even if you are running the same type of batteries 100amp relays are incredible expensive.

Overall I don't believe it is safe. But what do I know, some guy on the internet said it worked for him.

So far R14 resistor is the safest option in my opinion and actually shows promise because according to the technical document on this forum, it can actually work. No need for unsafe bridging relays that are complicated, etc.

thanks Savage & Gnome some good info there.

think for the time being I'll use the UPS as is and when it starts beeping I'll just plug in the inverter to the UPS which will then utillize the 100Ah battery capacity.

 

[Gnome]

think for the time being I'll use the UPS as is and when it starts beeping I'll just plug in the inverter to the UPS which will then utillize the 100Ah battery capacity.

Pretty much what I ended up doing was Inverter + battery bank + battery chargers.

I have a cheapo UPS that my sensitive stuff sits on, so they can ride through the transfer.

I auto-failover using these:
http://www.amazon.com/dp/B0078RDYEC/ref=pe_385040_128020140_TE_3p_dp_2
With this:
http://www.amazon.com/dp/B005TALQYU/ref=pe_385040_128020140_TE_3p_dp_1

The relay has a 240v coil. When the power goes out it switches my AC output to the Inverter. Hence I'm switching from Eskom AC to Inverter AC using that relay. Switchover is super quick also. Lights dim slightly nothing more (switching time is slightly more than a cycle which is nothing). It is enough that a PC would shut down tho, hence the UPS to "ride through". UPS cost me R400 or something so don't mind to much having spent that extra.

Since that relay is rated at 16amps (3680watt @ 230v AC), I'm happy with using that instead of a mechanically interlocked contactor which would cost 10x as much. To be clear however, I'm only running my lights and PC from my Inverter. If I went more than that I would need to buy a contractor to switch it safely.

 

[KOPITE]

Ok gents, for the time being that we finding a solution. Can I do the following.have both ups and external charger connected to the battery terminals. I leave the ups on and running all the time. The leave the ups off and by the plugs. Will this cause any issues or damage to the ups in any way.

Secondly when the power does go off then I back feed into the mains system via the power wall plug. While this is on and running, the external charger is still connected, but I don't switch on the external charger by the button. Will anything happen to the external charger when the ups feeds the batteries and the external charger is still connected via the battery terminals.can any back feed run into the external charger even though it's shut off by the flip switch and not connected to anything else.

If anyone can confirm nothing will happen on both scenarios then I can run this while I figure out which option is the best to go for now.

Another question I wanted to know, someone mention something about a contractor. How much does it cost and where does it fit in all of this.

 

[Gnome]

Back feeding is dangerous

But I suspect your earth leakage would trip due to the current running in completely the wrong direction.

 

[KOPITE]

Back feeding is dangerous

But I suspect your earth leakage would trip due to the current running in completely the wrong direction.

I know, been running for a couple of months without any issues.

 

[Gnome]

I know, been running for a couple of months without any issues.

Wow ok, and EL doesn't trip?

That is interesting. I saw another guy on Youtube trying it and his EL tripped straight away. Guess it depends on the kind of Inverter.

Another question I wanted to know, someone mention something about a contractor. How much does it cost and where does it fit in all of this.

I looked extensively, they are pretty expensive. You need a 3 pole single throw contractor x2. They are in turn powered by a single relay, single poll double throw (electronically prevent both being powered at the same time).

The problem I had was that contractors with mechanical interlock and 3 pole x2 would have worked out at R2k IIRC.

Mechanical interlock prevents them being turned on the same time, which would be catastrophic (mechanical meaning that it is physically prevented rather than relaying on electronics to prevent it).

But that said I didn't do extensive research on that as normal relays had enough current handling capability to use that over the contactors.

 

[KOPITE]

Wow ok, and EL doesn't trip?

That is interesting. I saw another guy on Youtube trying it and his EL tripped straight away. Guess it depends on the kind of Inverter.


I looked extensively, they are pretty expensive. You need a 3 pole single throw contractor x2. They are in turn powered by a single relay, single poll double throw (electronically prevent both being powered at the same time).

The problem I had was that contractors with mechanical interlock and 3 pole x2 would have worked out at R2k IIRC.

Mechanical interlock prevents them being turned on the same time, which would be catastrophic (mechanical meaning that it is physically prevented rather than relaying on electronics to prevent it).

But that said I didn't do extensive research on that as normal relays had enough current handling capability to use that over the contactors.

And what about my other questions

 

[thehuman]

Ups switched of and unplugged should be ok
Charger wise
Should be ok . I would for now rather unplug charger from mains tho

 

[mister]

UPS backfeeding with external charger connected and plugged in = perpetual energy machine

 

[KOPITE]

Ups switched of and unplugged should be ok
Charger wise
Should be ok . I would for now rather unplug charger from mains tho

Which charger off from mains

 

[thehuman]

Which charger off from mains

Your fancy expensive one
If the switch on charger completely switch charger off then ok to use switch

 

[bvdh]

Does anyone know (for fact) the amp rating of the internal charger in the RCT 2000?

If it is 10 amps then why do we need the external charger?

There should be enough time between load shedding windows to recharge 2 x 100Ah batteries

eg 2x100Ah requiring 50% recharge = 100Ah = 10 hours with a 10 amp charger.

 

[thehuman]

Does anyone know (for fact) the amp rating of the internal charger in the RCT 2000?

If it is 10 amps then why do we need the external charger?

There should be enough time between load shedding windows to recharge 2 x 100Ah batteries

eg 2x100Ah requiring 50% recharge = 100Ah = 10 hours with a 10 amp charger.

The problem here I understand is the cheap ups charger even though it may be a 10amp charger is most probably a 2 stage charger
Current limited to x amps
Voltage limited to 27.6 volts
It does not charge battery to 28.8 v for an hour and then drops down to 27.6