MinutemanUPS.com

toiyabeshawn · Joined: 01 Feb 2010 Posts: 3

Hello, I have a pair of MM600SS/1 ups units that, up until now, have been working flawlessly. The older unit mfg. in 1989 works and charges the batteries just fine. The unit mfg. in 1992 has now started to overcharge the batteries to the point that two of the four batteries got so hot that the terminals on the two inside batts burned and turned the jumper wire black. after 24 hrs of charging, the current going into the batts is still around 200 to 250 ma.

It appears that the regulation of the charge current has failed. Is there a simple way to fix this or can I disconnect the charge function and still have the inverter function? I have a stand alone 48 volt self regulated charger that I can hook up to charge the batteries.

tbuchanon · Posted: Wed Mar 24, 2010 7:53 am Post subject:

toiyabeshawn,

It sounds like one of your batteries maybe going bad. The MM600SS will only put out as much current as the batteries require. How old are the batteries and what brand are they? Also, What is your charge voltage?

Tim

toiyabeshawn · Joined: 01 Feb 2010 Posts: 3

the batteries are NOS (2 yrs old but never used) power sonic PS-1270. 12v 7.0 ah All eight batteries are from the same lot. I put 4 in the older unit, no problems... put the other four in the 1992 unit and after 48 hrs, the UPS case was extremely warm around the battery area so I opened it up and discovered the burned and melted connections. the charge voltage on both units is around 56-58 volts. and after the initial 48 hour charge on the 92 unit, the charge current was still very high around 250 ma.

the .250 quick connects were good and tight too, no loose connections.

also, the battery supplier I received the batteries from said that the batteries were charged every six months while they were on the shelf..Maybe or not, who knows, but all eight batteries had the same voltage and state of charge when I tested them right out of the box.

tbuchanon · Posted: Wed Mar 24, 2010 2:00 pm Post subject:

toiyabeshawn,

It still sounds like one of the batteries is going bad. To check you would need to put each individual battery under a load condition for 1 minute and then check the battery voltage.

Tim