Multibattery Uninterruptible Power Supply

[babatayomi]

Please i need ur help on a project i am doing on the above subject. The concept is that of a UPS that has more than one battery with all the batteries charging at the same time but discharging at different times in order to increase to increase the time for which the UPS lasts when there is no power supply. Pls i need a circuit diagram for this operation. i will be very grateful if u consider my request.

 

[Sebi]

I recommend to use 1 higher capacity battery, but keep in mind: the simple 500VA/15min UPS have very small heatsinks for longer work.

 

[Jay.slovak]

Please i need ur help on a project i am doing on the above subject. The concept is that of a UPS that has more than one battery with all the batteries charging at the same time but discharging at different times in order to increase to increase the time for which the UPS lasts when there is no power supply. Pls i need a circuit diagram for this operation. i will be very grateful if u consider my request.

Actually running them in paralel in both charging AND discharging will bring you longer operation, than switching them in sequence of discharging. The more load you place on battery, the lower final capacity it will reach and Vice versa.
And if you run them in paralel, you won't need any switching circuit and there won't be any "Dead" time between switching from one battery to another.

This only aplies when all batteries are same.

 

[eblc1388]

This only aplies when all batteries are same.

Fine but it is never the case in real life situation.

Even with the same batch of batteries, they reach their end of discharge at different moment and with just a 0.1V voltage difference, there is sufficient circulating current to damage other batteries in the group.

 

[Jay.slovak]

This only aplies when all batteries are same.

Fine but it is never the case in real life situation.

Even with the same batch of batteries, they reach their end of discharge at different moment and with just a 0.1V voltage difference, there is sufficient circulating current to damage other batteries in the group.

Hmm it depends on the battery type. If you use Pb gel batteries, this shouldn't be a problem. Also if you put a very low ohm resistor in series with each batterie (like 50mR), voltage drop would compensate any volatege irregularities. 8)

 

[audioguru]

Have you ever seen the lead-acid battery in a telco central office?
They don't have parallel problems because they use the biggest 2V separate cells, connected in series, that you have never imagined. :lol:

 

[Nigel Goodwin]

Have you ever seen the lead-acid battery in a telco central office?
They don't have parallel problems because they use the biggest 2V separate cells, connected in series, that you have never imagined. :lol:

BIG aren't they :lol:

How about submarine batteries?, now they are REALLY big!.

 

[babatayomi]

thanx 4 d help

This only aplies when all batteries are same.

Fine but it is never the case in real life situation.

Even with the same batch of batteries, they reach their end of discharge at different moment and with just a 0.1V voltage difference, there is sufficient circulating current to damage other batteries in the group.

What u r trying 2 tell me is that if d batteries r d same they will all still discharge at approximately the same time even if there is a switching circuit for the batteries. :?: :?

 

[eblc1388]

Re: thanx 4 d help

What u r trying 2 tell me is that if d batteries r d same they will all still discharge at approximately the same time even if there is a switching circuit for the batteries. :?: :?

Read very carefully. There are two issues in your question.

1. Discharging time: It only depends on the load. Two batteries will give double the discharging time.

2. Multiple batteries:

What I was telling you was even with batteries of the same brand bought at the same time, they would not give you exactly the same discharging time and there will be say a few minutes differences. This would cause no harm if batteries are connected in series but for parallel connection, circulation current will flow from the batteries that still got higher energy than ones that hasn't.

You are wasting energy and risk damaging some of the batteries in a parallel configuration.

So say for example if you need two 12V 10AH single battery in parallel, you are much better off buying two 6V 20AH batteries and connect them in series. Both will give you 12V 20AH but series connection would avoid all the troubles.

If you switches in a full battery as the one in use is approaching its end of discharge, then you are not limited to only two batteries(you can have as many as you wish) but the difficulties in the hardware switching aspect is not an easy one to solve.

 

[babatayomi]

Re: thanx 4 d help

I am so grateful for ur help. like u said the project is a hard nut to crack but i still think its possible. do you? :?: Please i dont know if you could help with a format for my table of contents for the project cuz i also have to submit a thesis on the project. thanx.