Off Grid battery backup system charging question.

[Zerk]

I am going to go with what the manufactors recommend. Same size. Now if financially I didn't want to replace all the batteries, I may roll the dice.


Another thing is are float charging, constant charge, running of charger, or boost charging, periodically raising voltage. Not sure how these tenders work. We do both on battery banks, not sure the reason, Maybe just the thoughts at the time.

We have battery banks that last 25+ years. They don't get moved, constant temp, and charging. I think lack of movement may be a driving factor. But battery banks at home are not moving.

As mentioned earlier there are safety concerns with charging large banks of batteries. Do people take this into account at home?

 

[RNeumann]

What your Xantrex "sees" is voltage- this is what determines when it is charging, floating etc. It isn't the battery type. The Xantrex is asking for amp hour rating to determine the estimated time left at the current rate of discharge. The unit is asking battery type as different battery construction types (AGM, lead acid) take slightly different charge/float voltage. No battery charger changes rate of charge based on amper hour rating- that is always changing with battery condition.
The battery banks need to be properly isolated (your isolation switch ain't it- that's for sure) from each other. It would be interesting to see how you can keep them isolated and yet charge them as one.....not sure their is a practical solution to this.
My other concern is the thought of "reviving" batteries. If this was truly possible someone would be very rich and batteries would last a long long long time. Without a Midtronics tester you will have very little idea the actual state of the batteries.
Good luck. But based on what I've read so far things are far from optimal.

 

[Tractor Seabee]

Per Neumann, above stated reviving cells (batteries) is not really possible. I have seen minor sulphating be overcome but the capacity and life are compromised. There is a shocking process used that causes the sulphate to drop off the plates. In a clear case cell (all large individual cells have clear cases) you can see this happen and it piles up in the bottom of the case. Sulphating reduces the strength of the acid when it precipitate's on the lead plate. The Sulphur crystal part of the acid does dissolve back into the liquid acid. De-sulphating is probably not a good DYI effort.

Lots of luck, Ron

 

[CCWKen]

I have a 7KW UPS system that uses four drawers of motorcycle sized batteries. They're connected in series for 120vdc (+/-) and parallel for current support. If just one battery in the case is flaky, the console flashes an error and beeps. It takes me about an hour to find the errant battery and replace it. The charging system is smart enough to know there's a problem but not smart enough to tell me where. I suspect it monitors charge/battery factors in a narrow band and throws a warning if it goes out of bounds but its always been right. On average, I replace 1-2 batteries a year. And all the batteries have to be the same or it chokes on startup. If I hit the lottery, I may just replace them all and get 4-5 years of peace and quiet.

And yes, I'm a nervous wreck after poking around in a 120vdc cabinet.

 

[Zerk]

Curious what are you doing with this? Is it just a back up for your house, instead of a generator? Are you charging it with alternate energy an using it, or is it just back up?

 

[Tractor Seabee]

I have a 7KW UPS system that uses four drawers of motorcycle sized batteries. They're connected in series for 120vdc (+/-) and parallel for current support. If just one battery in the case is flaky, the console flashes an error and beeps. It takes me about an hour to find the errant battery and replace it. The charging system is smart enough to know there's a problem but not smart enough to tell me where. I suspect it monitors charge/battery factors in a narrow band and throws a warning if it goes out of bounds but its always been right. On average, I replace 1-2 batteries a year. And all the batteries have to be the same or it chokes on startup. If I hit the lottery, I may just replace them all and get 4-5 years of peace and quiet.

And yes, I'm a nervous wreck after poking around in a 120vdc cabinet.

I know what you mean non working around DC. I would much rather get it by AC not if I can help either. Just be careful and isolate live parts with a blanket and wear di-electric gloves. I have safely worked on up to 500V DC and 480 V AC by being careful and not going into live stuff except when absolutely that is the only choice. The most dangerous (scary) array is large banks of large single cells (a room full) for 250 and 500 DC power. The National Electrical Safety Code (NESC) does not allow working on live parts.

Be safe, Ron

 

[Industrial Toys]

Most xantrex chargers I have owned or worked on have a selection for the type of battery. Usually flooded, gell or glassmat

I hope everyone with battery banks has a high current limiting fuse or breaker at the battery. CRAZY not to.

Plus tape up your wrenches.

 

[scdeerslayer]

So is this 4 total batteries? If so I would just get a 4 bank marine charger.

 

[Zerk]

Most xantrex chargers I have owned or worked on have a selection for the type of battery. Usually flooded, gell or glassmat

I hope everyone with battery banks has a high current limiting fuse or breaker at the battery. CRAZY not to.

Plus tape up your wrenches.

Ya battery banks have fuse. I don't find working with 125 vdc that big of deal. 250 DC will melt alligator clips faster.

 

[90cummins]

What your Xantrex "sees" is voltage- this is what determines when it is charging, floating etc. It isn't the battery type. The Xantrex is asking for amp hour rating to determine the estimated time left at the current rate of discharge. The unit is asking battery type as different battery construction types (AGM, lead acid) take slightly different charge/float voltage. No battery charger changes rate of charge based on amper hour rating- that is always changing with battery condition.
The battery banks need to be properly isolated (your isolation switch ain't it- that's for sure) from each other. It would be interesting to see how you can keep them isolated and yet charge them as one.....not sure their is a practical solution to this.
My other concern is the thought of "reviving" batteries. If this was truly possible someone would be very rich and batteries would last a long long long time. Without a Midtronics tester you will have very little idea the actual state of the batteries.
Good luck. But based on what I've read so far things are far from optimal.

As I described my original 2 banks of batteries are isolated with a switch and has a 200 amp fuse in the circuit.
When charging/discharging the J185 batteries I de-energize the T105 bank and remove 1 bridge between the batteries then connect the J185's to the 24v charger using a 175a Anderson connector, then re-energize that bank only which charges the j185's.
I paid $50 for the complete machine with batteries.
I went to my local salvage yard and was told that the scrap price for each battery was approx. $25+- so I have nothing to lose here.
In addition I have stripped the machine of all relays and heavy cable including a 175a connector that is being used here.
This is a learning experience for me with nothing to lose, as I mentioned earlier I revived the T105's currently being used and they are at 80~90% capacity.
If these batteries are beyond saving I will put them aside as a core for when I need to buy new batteries.
This is all good information and appreciate the input.
90cummins