UPS battery

[andy]

my UPS for my comp has a 7AH battery. however i have added a second 50AH battery. would the charger on the UPS be able to charge the 50AH battery (obviously itll charge slower) or will i need a seperate charger?

 

[Screwi]

no you cant use that batt - you will damage the electronics as they wont be rated for the increased charge current and longer time plus more heat etc etc

 

[big-all]

wouldnt have thought so andrew not unless the charger is grossly over rated for 7 ah but i dont realy know the answer

all i can tell you its got to be able to match the cappacity of a fully charged battery plus a bit more as the battery is fighting the charger till its fully charged
although non transformer tecknoligy may be different

 

[andy]

no you cant use that batt - you will damage the electronics as they wont be rated for the increased charge current and longer time plus more heat etc etc

it can take the extra demand of running longer. i have put it in a larger case with 2 fans which come on automatically if the power fails to keep the PCB and transformer cool. main question was wether it could charge the extra battery. im gonna order a seperate charger to charge the extra battery

 

[plugwash]

using a seperate charger could do more harm than good unless you are very carefull.

the trouble is you don't really wan't to connect two chargers together so you will have to design some switchover system.

also if you plan to keep the original battery as well you have the potential issue of current flowing between the batteries when they connect together and if you don't then you are likely to get a brownout as your switching system activates.

 

[andy]

using a seperate charger could do more harm than good unless you are very carefull.

the trouble is you don't really wan't to connect two chargers together so you will have to design some switchover system.

also if you plan to keep the original battery as well you have the potential issue of current flowing between the batteries when they connect together and if you don't then you are likely to get a brownout as your switching system activates.

ATM there is a 70A relay so that the external battery is only connected if the power fails. so because of this, it cant be on charge and connected to the main UPS

so far it has been alright when switching from mains to battery and everything is staying cool... 1 1/2 hours into the test....

main concern was re-charging the external batteries... which im gonna get a seperate charger from sometime nxt week (my week off)

 

[plugwash]

did you leave the internal battery connected or not?

mind you lead acid batteries can generally stand pretty rough treatement. What you are doing with the relay is not really a whole lot different from what you do when jump starting a car.

 

[Big_Spark]

Andrew, the charger you have will charge the battery, or both of them if connected in parallel. It is the voltage that is important, so long as this is the same then your OK.

Of course the charge rate will be dramatically reduced as a result and the time taken to charge both batteries from empty to full will depend purely on the charge rate of the charging system.

I wonder why you need a 50Ah battery in conjunction with the existing 7Ah unit? Domestic UPS's are not designed to run the machines, they are designed to allow controlled shutdown after you have saved your work, in essence. The software that came with your UPS may not allow you to run a machine longer than a set time due to heat stresses and electrical stresses in the Inverter it contains, I would be more concerned about this than whether it can charge the batteries.

 

[kevplumb]

you are likely to get a brownout

alright i'm only a dozy plumber somebody want to explain

 

[andy]

Andrew, the charger you have will charge the battery, or both of them if connected in parallel. It is the voltage that is important, so long as this is the same then your OK.

Of course the charge rate will be dramatically reduced as a result and the time taken to charge both batteries from empty to full will depend purely on the charge rate of the charging system.

I wonder why you need a 50Ah battery in conjunction with the existing 7Ah unit? Domestic UPS's are not designed to run the machines, they are designed to allow controlled shutdown after you have saved your work, in essence. The software that came with your UPS may not allow you to run a machine longer than a set time due to heat stresses and electrical stresses in the Inverter it contains, I would be more concerned about this than whether it can charge the batteries.

thanx for the info.

i have changed its case and it has good cooling so it wont overheat (its been runnig from battery for over 1 1/2 hours and i can touch the transformer and the main heatsink on the PCB. altho they are a lil warm). the ups is not connected to the computer... its only connections are mains in, out and battery in

 

[ninebob]

you are likely to get a brownout

alright i'm only a dozy plumber somebody want to explain

Try here or here

 

[kevplumb]

cheers si

 

[breezer]

i do not think it wise to use a 50 ah batt on a charger that was designed for only 7ah batt.

yes in theory it will work, take longer to charge etc, in practice it doesn't always work.

as batteries are getting flat, bigger one may discharge into smaller one also when 50 ah batt is flat it will draw a heck of a lot of current at initial mains restoration, this my be too much for your charger, also if it is being trickle charged all the time, the battery may never recover if it goes flat.

 

[andy]

i do not think it wise to use a 50 ah batt on a charger that was designed for only 7ah batt.

yes in theory it will work, take longer to charge etc, in practice it doesn't always work.

as batteries are getting flat, bigger one may discharge into smaller one also when 50 ah batt is flat it will draw a heck of a lot of current at initial mains restoration, this my be too much for your charger, also if it is being trickle charged all the time, the battery may never recover if it goes flat.

thanx. ive ordered a seperate charger for it

 

[Big_Spark]

i do not think it wise to use a 50 ah batt on a charger that was designed for only 7ah batt.

yes in theory it will work, take longer to charge etc, in practice it doesn't always work.

as batteries are getting flat, bigger one may discharge into smaller one also when 50 ah batt is flat it will draw a heck of a lot of current at initial mains restoration, this my be too much for your charger, also if it is being trickle charged all the time, the battery may never recover if it goes flat.

Breezer, whilst one battery may discharge into the other, this is of little consequence in the scheme of things, however your comment about about the battery drawing a lot of current initially is misleading and will not be the case. The Battery will be charged at the rate of the input of the charger with no ill effect to either.

I have built many charger systems for Solar and similar UPS systems over the years and you will never see the effect your suggesting unless there is a failure of the batttery cells.

I have installed a 3AH 20V Solar Panel on the roof of my Van, this charges a bank of (5)90AH and two 500AH 12V Lead-Acid batteries in a compartment in the rear, as well as trickle charging the Van battery when the engine isn't running (switching by a No Volt release contactor). The Panel and the circuitry, as well as the batteries suffer no ill effects of this.

In fact a slower charge is better for the battery as it reduces electrical, mechanical and chemical stresses in the batteries.