Modifying a RCT2000VA UPS with an External charger

KOPITE said:
Ok guys, I have a gut feeling the charger might be the one with the yellow on it called CSEpower. Anyone have any recommendations
Click to expand...

You are 100% wrong. That is the current sense transformer. It will almost certainly have nothing to do with charging.

Haha, I am watching this thread. Need to see what the end result is. This is going to be good.

This design was copied from the APC design btw. minus the true sinewave and safety circuitry before the first CT. Lower quality components (Chinese caps for example, relays look cheap, etc). But overall looks pretty decent tbh. Transformer is pretty cheap tho, so likely very inefficient. But considering it is low frequency it was going to be inefficient anyways..

So let's see:
1) This is a low frequency design. It is clear from the big ass mains frequency transformer. They clearly generate AC at low voltage then step it up using that thing.
2) They are running the inverter in reverse to charge the battery with the big ass transformer secondary being used as an inductor.
3) While this is happening the transformer primary is being used as a auto-transformer. Very classic APC design and really cool actually :)

They even say that in the manual you downloaded:
"Charger: The battery is charged by the mains through transformer and full-bridge inverter. "

The interesting bit is even though you are completely wrong about the current sense transformer, and I am super curious what will happen if you remove it (I suspect it will stop working but let's see), it does appear that there may be a way to disable charging.

This part for example has some very good nuggets of info:
"The flow chart of charger is described as follows: (Figure S-3-A & Figure S-3-B)
4.1 When UPS is connected to the utility, the control power (+5Vdc) will be established and the CPU will start to work.
4.2 When CPU turns on Main Relay (RY01), the AC power flows into Main Transformer.
4.3 Charging current will be generated from the inverter coil of the Main Transformer.
4.4 A PWM IC 3843 is used to adjust the charging voltage and charging current. (Refer to Figure S-3-A) The charging voltage can be set by changing the value of R87, R88, R46 and R65. The charging current can be set by changing the value of R14. "

So they are using a PWM chip to drive the transistors for charging. I haven't really got time to spend on this but if that PWM chip doesn't do anything other than drive the charge functionality I would considering removing VCC to the chip and see if that stops the charger from working.

Again. This. is. dangerous.

You are thinking of removing a current sense transformer to stop this thing charging when it doesn't even factor into it. It is actually there to prevent over current situations...

Are you are sure you should be doing this?
 
Last edited:
Gnome said:
You are 100% wrong. That is the current sense transformer. It will almost certainly have nothing to do with charging.

Haha, I am watching this thread. Need to see what the end result is. This is going to be good.

This design was copied from the APC design btw. minus the true sinewave and safety circuitry before the first CT. Lower quality components (Chinese caps for example, relays look cheap, etc). But overall looks pretty decent tbh. Transformer is pretty cheap tho, so likely very inefficient. But considering it is low frequency it was going to be inefficient anyways..

So let's see:
1) This is a low frequency design. It is clear from the big ass mains frequency transformer. They clearly generate AC at low voltage then step it up using that thing.
2) They are running the inverter in reverse to charge the battery with the big ass transformer secondary being used as an inductor.
3) While this is happening the transformer primary is being used as a auto-transformer. Very classic APC design and really cool actually :)

They even say that in the manual you downloaded:
"Charger: The battery is charged by the mains through transformer and full-bridge inverter. "

The interesting bit is even though you are completely wrong about the current sense transformer, and I am super curious what will happen if you remove it (I suspect it will stop working but let's see), it does appear that there may be a way to disable charging.

This part for example has some very good nuggets of info:
"The flow chart of charger is described as follows: (Figure S-3-A & Figure S-3-B)
4.1 When UPS is connected to the utility, the control power (+5Vdc) will be established and the CPU will start to work.
4.2 When CPU turns on Main Relay (RY01), the AC power flows into Main Transformer.
4.3 Charging current will be generated from the inverter coil of the Main Transformer.
4.4 A PWM IC 3843 is used to adjust the charging voltage and charging current. (Refer to Figure S-3-A) The charging voltage can be set by changing the value of R87, R88, R46 and R65. The charging current can be set by changing the value of R14. "

So they are using a PWM chip to drive the transistors for charging. I haven't really got time to spend on this but if that PWM chip doesn't do anything other than drive the charge functionality I would considering removing VCC to the chip and see if that stops the charger from working.

Again. This. is. dangerous.

You are thinking of removing a current sense transformer to stop this thing charging when it doesn't even factor into it. It is actually there to prevent over current situations...

Are you are sure you should be doing this?
Click to expand...

I'm not doing this myself. I asked an electrician today to see if he can maybe do it for me. Waiting on him.
 
OP try what I suggested. I do not believe it will **** anything up. One of 2 scenarios..

1. UPS is dead and won't work. Simply connect R14 again.
2. Charger only has stopped working. Everything else fine.
 
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KOPITE said:
I'm not doing this myself. I asked an electrician today to see if he can maybe do it for me. Waiting on him.
Click to expand...

An electrician is going to come up with an expensive "out of the box" solution. As in "out of the UPS box".
All that is needed is a very small disconnection inside the UPS. No extra parts or anything....
 
Still think the mains sence relay will work better
Small relay to detect mains
That relay switch a 24v car relay to conect battery
 
Joe_Moer said:
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.
Click to expand...

KOPITE said:
How do I do this
Click to expand...

Like that
 
Can we not contact RCT or the reseller and find out if the builtin charger has a float charge. Then I can charge them with both permanently.
 
thehuman said:
Like that
Click to expand...

Ok, so the way I understand this, because I don't have an extra battery pack, I only have the current batteries in series. What you saying I put a relay on the normal power plug and switch the relay to cut off power from the mains and then charge via the external charger. Is this happening while everything is on 24/7. I will only use the relay when I need to charge via external charger.
 
^^^You need to understand how a 3 stage charger works. It doe's not just float charge. It is constantly monitoring the battery/batteries under its supervision. They do crazy stuff..mine cycles from 14.4V down to 13.2V and keeps all topped up when floating the battery....

All that a normal float charger (internal cheap UPS) does is float the battery. Cannot think.

So, it's either one charger in control, or nothing. Otherwise they will end up fighting. You see it?
 
amongstthevotingfodder said:
^^^You need to understand how a 3 stage charger works. It doe's not just float charge. It is constantly monitoring the battery/batteries under its supervision. They do crazy stuff..mine cycles from 14.4V down to 13.2V and keeps all topped up when floating the battery....

All that a normal float charger (internal cheap UPS) does is float the battery. Cannot think.

So, it's either one charger in control, or nothing. Otherwise they will end up fighting. You see it?
Click to expand...

So is my explaination correct or not
 
KOPITE said:
Ok, so the way I understand this, because I don't have an extra battery pack, I only have the current batteries in series. What you saying I put a relay on the normal power plug and switch the relay to cut off power from the mains and then charge via the external charger. Is this happening while everything is on 24/7. I will only use the relay when I need to charge via external charger.
Click to expand...

Show that section to your electrician guy
 
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