hot batteries

[almac]

noticed 24v battery bank pulling 20amps from the charge controllers and never getting charged. after sunset i checked the voltage and it had dropped to 23v WITH NO LOAD! realizing the discharge was going somewhere i felt the batteries. there are 6 x 12v paired to make 3 x 24v. 2 of the 12v batteries that are paired were HOT! the 50 amp fuses had not blown. i disconnected them and put them outside to cool down. im guessing one of the 12v batteries in this pair has developed an internal short. starting to think i might end this junked battery trial and buy some new deep cycle. i can get FLA deep cycle about 500AH 24v for around the $2000 mark. still good valueDSCN0645.JPG

[Logan005]

If I gather correctly, you have 24 volts paralleled in 3 banks? there is your first problem, paralleled batteries charge unbalanced and live short lives. I would not get any more batteries until you understand how you destroyed all of these batteries.

[Mike90250]

I'm very glad you spotted them before a big problem happened.

[Sunking]

Both are boat anchors. Time to replace them with real deep cycle batteries. You should not use SLI or car/truck batteries. Hope you learned your lesson.

[SunEagle]

noticed 24v battery bank pulling 20amps from the charge controllers and never getting charged. after sunset i checked the voltage and it had dropped to 23v WITH NO LOAD! realizing the discharge was going somewhere i felt the batteries. there are 6 x 12v paired to make 3 x 24v. 2 of the 12v batteries that are paired were HOT! the 50 amp fuses had not blown. i disconnected them and put them outside to cool down. im guessing one of the 12v batteries in this pair has developed an internal short. starting to think i might end this junked battery trial and buy some new deep cycle. i can get FLA deep cycle about 500AH 24v for around the $2000 mark. still good value[ATTACH=CONFIG]n302859[/ATTACH]

Unfortunately this issue is what we have warned you about. Mixing and matching cheap batteries will usually end up getting the entire system crashing.

Just saying that "One bad apple" or battery will ruin the whole bunch.

[almac]

thanks , i understand about mixing batteries with different capacities will put strain on the battery with the least resistance giving it an early death, these batteries cost $6 each and i get that back at the scrap dealer. i am more concerned about the hazard posed by this battery shorting and getting hot. it would be nice to have 500AH of new deep cycle batteries for sure, a $2000 investment well spent i dont deny. i would never mix expensive batteries. the 50 amp fuse allowed enough current to pose a hazard. maybe if i went to a much lower amp fuse, just enough for the loads i intend to use .

[Sunking]

Fuse has nothing to do with it. Your panels are not capable of generating enough current to operate the fuse. The hazard is a battery explosion and fire. You were warned long ago this was going to happen and will continue to happen.

[almac]

Fuse has nothing to do with it. Your panels are not capable of generating enough current to operate the fuse. The hazard is a battery explosion and fire. You were warned long ago this was going to happen and will continue to happen.

not according to mike. the fuses are for each battery in parallel. the current that roasted the battery came from the other batteries wired to it in parallel. when the cell shorted the other batteries discharged into the shorted battery. in this case the resistance of the short kept the current under 50 amps. still enough to heat the battery dangerously so a lesser fuse should be safer. also lowered the charging voltage from 28.8v to 27.4v

[sensij]

With a 500 Ah battery, should should probably be charging it at 50 A, Hard to see how you can make the fuse much smaller than that.

[almac]

With a 500 Ah battery, should should probably be charging it at 50 A, Hard to see how you can make the fuse much smaller than that.

its not 500AH. in any case we are talking about PARALLEL BATTERY FUSES. with 3 batteries in parallel there are 3 x 50 amp fuses. when i draw say 80 amps using my 1400w coffee machine i am drawing about 25 amps across each fuse. plenty of scope for smaller fuses

[Sunking]

Fuses are to protect wiring nothing else. Size them too small and the equipment will malfunction. Size them too large and you risk a fire.

[almac]

Fuses are to protect wiring nothing else. Size them too small and the equipment will malfunction. Size them too large and you risk a fire.

im using 25 amp wire, iv tested 25 amp wire they can handle double that for short periods ( less than a minuite) but these are installed to fuse should a battery get a shorted cell so i dont get 200+ amps dumped into a battery and have a battery explosion

[Sunking]

im using 25 amp wire, iv tested 25 amp wire they can handle double that for short periods ( less than a minuite) but these are installed to fuse should a battery get a shorted cell so i dont get 200+ amps dumped into a battery and have a battery explosion

Geeze that is so dangerous. You clearly do not understand electricity basic fundamentals or electrical safety. You cannot control current in the fashion you describe. Makes no fricking difference what the peak current is. Fuses and breakers are sized on the wire size. That means a wire, say 3 mm^2 can only safely conduct 25 amps continuous. That means the largest fuse you can use is 25 amps period. You can use smaller, but you cannot use anything larger safely.

[almac]

s

Geeze that is so dangerous. You clearly do not understand electricity basic fundamentals or electrical safety. You cannot control current in the fashion you describe. Makes no fricking difference what the peak current is. Fuses and breakers are sized on the wire size. That means a wire, say 3 mm^2 can only safely conduct 25 amps continuous. That means the largest fuse you can use is 25 amps period. You can use smaller, but you cannot use anything larger safely.

safer than before i had no fuses at all. dont intend to load more than 25 amp . ok so 50 amp fuses are pointless. so will try 25 amp fuses , if they dont blow then all good. if they do blow then will have to go to 30 amp cable and fuses

[ButchDeal]

s
safer than before i had no fuses at all. dont intend to load more than 25 amp . ok so 50 amp fuses are pointless. so will try 25 amp fuses , if they dont blow then all good. if they do blow then will have to go to 30 amp cable and fuses

Good plan ( lack there of). Hack it together till something happens then adjust. Only problem is the something that could happen is explosion and fire....
But keep hacking away.