Hi
I need some guidance whether my plan is feasible  
Okay some details before hand

I have a RCT 2000VA UPS ,
and the batteries(2 x 12v 7.2ah in series) are dead I am planning on replacing the batteries With 2 x 12v 50ah batteries

Now I know the built in charger is too weak to charge them

By my calculations and other posts in this thread,
it will take 2-3 days to charge them from empty on the built in charger
I will also add more cooling to avoid the overheating, maybe a heatsink and a few fans

To The Actual question now

So I am planning on getting an external charger, solar or Eskom to charge the batteries

What I need guidance with

I want to connect the batteries to the UPS with a diode/s to stop the built-in charger from giving power to the batteries And then a diode from the batteries to the external charger to stop power from going back into the charger

The above is so that I can avoid having to unplug batteries charge and then replug them like suggested in other forums and such

Will this work? 

So that I do not have to unplug the batteries, and can just keep it as a standalone low maintenance unit

Or must I rather add something like brad harrison connectors to the batteries unplug them to charge and then replug them after charging

Or will this cause more voltage to go intot he UPS from the charger being permanently connected

Thank you in advance

46 minutes ago, Antibiotika224 said:

Hi
I need some guidance whether my plan is feasible  
Okay some details before hand

I have a RCT 2000VA UPS ,
and the batteries(2 x 12v 7.2ah in series) are dead I am planning on replacing the batteries With 2 x 12v 50ah batteries

Now I know the built in charger is too weak to charge them

By my calculations and other posts in this thread,
it will take 2-3 days to charge them from empty on the built in charger
I will also add more cooling to avoid the overheating, maybe a heatsink and a few fans

To The Actual question now

So I am planning on getting an external charger, solar or Eskom to charge the batteries

What I need guidance with

I want to connect the batteries to the UPS with a diode/s to stop the built-in charger from giving power to the batteries And then a diode from the batteries to the external charger to stop power from going back into the charger

The above is so that I can avoid having to unplug batteries charge and then replug them like suggested in other forums and such

Will this work? 

So that I do not have to unplug the batteries, and can just keep it as a standalone low maintenance unit

Or must I rather add something like brad harrison connectors to the batteries unplug them to charge and then replug them after charging

Or will this cause more voltage to go intot he UPS from the charger being permanently connected

Thank you in advance

I assume you have the 2000va line interactive ups below:

These type of units are not built for supplying power for long periods (15~30min max). In the event of a power failure they are used on pc's to allow you time to back up and switch off. To try and fit bigger batteries will force the ups to stay on for longer periods and damage the unit. Rather look at purchasing a small 24v Rct Vm2 or Vm3 inverter that could serve you well for long periods. I would also advise to purchase lifep04 battery module as lead acid is not fit for purpose.

Edited January 24, 20242 yr by TaliaB

Thank you for the reply
That is not the same unit I have but maybe an older model
Anyways
Yes I know it is not made for prolonged use and this is because of Overheating,
and fixing the overheating issue it will run for prolonged periods as stated in my post
I am also on a tight budget, that is why I am not buying another inverter because that would double my budget 

That being said
I need advice on the last part I am going to replace the UPS eventually with a Proper Inverter later on

IE
 

I want to connect the batteries to the UPS with a diode/s to stop the built-in charger from giving power to the batteries And then a diode from the batteries to the external charger to stop power from going back into the charger

The above is so that I can avoid having to unplug batteries charge and then replug them like suggested in other forums and such

Will this work? 

So that I do not have to unplug the batteries, and can just keep it as a standalone low maintenance unit

Or must I rather add something like brad harrison connectors to the batteries unplug them to charge and then replug them after charging

Or will this cause more voltage to go intot he UPS from the charger being permanently connected

And not advice on the UPS etc. 

3 hours ago, Antibiotika224 said:

Thank you for the reply
That is not the same unit I have but maybe an older model
Anyways
Yes I know it is not made for prolonged use and this is because of Overheating,
and fixing the overheating issue it will run for prolonged periods as stated in my post
I am also on a tight budget, that is why I am not buying another inverter because that would double my budget 

That being said
I need advice on the last part I am going to replace the UPS eventually with a Proper Inverter later on

IE
 

I want to connect the batteries to the UPS with a diode/s to stop the built-in charger from giving power to the batteries And then a diode from the batteries to the external charger to stop power from going back into the charger

The above is so that I can avoid having to unplug batteries charge and then replug them like suggested in other forums and such

Will this work? 

So that I do not have to unplug the batteries, and can just keep it as a standalone low maintenance unit

Or must I rather add something like brad harrison connectors to the batteries unplug them to charge and then replug them after charging

Or will this cause more voltage to go intot he UPS from the charger being permanently connected

And not advice on the UPS etc. 

Normally the charge-discharge is the same wire inside the UPS. With the diode means the inverter will be getting 0.7V less than the battery voltage. 

At times there are limits to making something cheaper work. 

Also if not pure sine it might also have limits to the loads one can use. Sorry but I just don't like non pure sine wave inverters as I leaned my lesson with my 1st non pure sine inverter. 

Beware of fiddling with a line interactive battery circuit. 

Edited January 24, 20242 yr by Scorp007