UPS battery

[breezer]

you speak from your experiance, i speak from mine.

 

[kendor]

I think you should be aware of what the minimum internal resistance of the batteries could be when both where discharged as this will determine the charging current as lead acid chargers unlike nicad chargers are not constant current sources, i would worry whether the secondary winding of the charger's transformer would be of sufficient current capacity so check first as it could be an expensive mistake otherwise!

 

[andy]

I think you should be aware of what the minimum internal resistance of the batteries could be when both where discharged as this will determine the charging current as lead acid chargers unlike nicad chargers are not constant current sources, i would worry whether the secondary winding of the charger's transformer would be of sufficient current capacity so check first as it could be an expensive mistake otherwise!

thanx for the advice every1

current setup:

4 50AH bateries in parallel. these are charged from their own charger and connected to the main UPS by a 70A relay which only changes if the mains fails. in which case the charger would be off so that cant do damage to the UPS

total run time: got sick of the beeping after 8 hours

 

[kendor]

I think you should be aware of what the minimum internal resistance of the batteries could be when both where discharged as this will determine the charging current as lead acid chargers unlike nicad chargers are not constant current sources, i would worry whether the secondary winding of the charger's transformer would be of sufficient current capacity so check first as it could be an expensive mistake otherwise!

thanx for the advice every1

current setup:

4 50AH bateries in parallel. these are charged from their own charger and connected to the main UPS by a 70A relay which only changes if the mains fails. in which case the charger would be off so that cant do damage to the UPS

total run time: got sick of the beeping after 8 hours

Do you use an invertor to convert the battery power into mains to drive the UPS? or are these batteries in parallel with the internal batteries in the ups?

 

[andy]

Do you use an invertor to convert the battery power into mains to drive the UPS? or are these batteries in parallel with the internal batteries in the ups?

the 4 50AH bateries are in parallel with the 7AH internal battery, but they go thru a 70A relay so the external batteries are only connected when the mains fails. when the mains is there, the external batteries are seperated from the ups battery and are charged

 

[kendor]

clever idea! can't see any obvious problems with your setup so good luck!

 

[CallEdsFirst]

you are likely to get a brownout

Isnt a brownout what happens when four 50aH SLA batteries go up in flames because the charger can't handle the load?

I have to say the set up strikes me as incredibly clever. Batteries only connected when mains off, disconnected battery bank only charges when mains on. The only concern might be, as already mentioned, overheating. You have a box that is designed to supply 7 amps for an hour or even 1 amp for 7 hours, and you are making it able to supply 1 amp for 207 hours. Is that right? I would hope that fusing prevents it from supplying 207 amps for 1 hour!!!!

 

[electronicsuk]

I would hope that fusing prevents it from supplying 207 amps for 1 hour!!!!

I think the invertor is far more likely to freak out at the sight such a large load before any fuses would pop

 

[wiggles]

One of my pet articles on the subject. I particularly like the discussion on the pros and cons are various battery types. I've often thought about setting up a system like this and keeping the batterys outside in a weatherproof but ventilated area.

http://www.dansdata.com/diyups.htm