batteries

[thirteen]

I plan on being gone from my place for up to 4 months at a time. I am wondering if I should take the jumper wires off each battery or just an isolation switch for the pos and neg leads from each bank? There will be nothing that needs to be left on while I am gone. I just do not want to come back in the winter to a meltdown. I was thinking that when the batteries get older(8yrs) maybe then take the wires off but on a new system maybe not? The power shed will be insulated but not heated.  

[Flux]

If you have parallel strings it makes sense. If one cell in one string goes down it will discharge the lot and possibly sulphate them. If you isolate the strings you will only have one faulty string at the end.

I doubt that it would ever come to a meltdown situation, I think there is a lot of fear about batteries that is not justified unless you do something very silly, but preventing destructive discharge in event of a cell failure is sensible.

Flux

[bob g]

personally i am not big on letting a battery sit idle for extended lengths of time, they will have a certain self discharge rate, which gets worse as they age.

over time the self discharge which just like regular discharging will build up some sulfation and over 4 months is likely to harden and become difficult to break back down on recharge.

the result is loss of capacity.

some battery technologies are worse than others when it comes to self discharge.

the higher the antimony content in the plates the higher the self discharge rate.

iirc figure on about 2% per month, which compounds like interest monthly (maybe), and likely will be higher as the batteries get older.

at the very least i would make a good log of specific gravity readings if they are flooded cells, and then upon return be prepared to fully charge them and if necessary do an equalization charge to get them back into proper condition.

how big of a bank do you have? what type of battery technology? agm, flooded,vrla, etc.. ?

each have their own concerns.

bob g

[Flux]

Yes 4 months is a long time. I agree with bob that when new it may not be an issue but may be a problem with older batteries.

If you can't avoid this problem then using calcium grid batteries would help considerably.  VRLA and gell come out far better in this respect, that may be one of their greatest virtues, I don't generally like them.

The antimony based 2v cells and traction batteries do have a high self discharge and when a few years old they may not like being left 4 months. Any chance of a bit of solar to help against the self discharge. No need to have enough to need controllers.

If you do maintain some charge it removes your option to break the strings unless each one has a panel.

Flux

[snowcrow]

  I have a remote camp in the mountains and shut everything down for the winter, except an 80 watt solar panel and the charge controller. I set my controller up to maintain the battery bank at float voltage.  It takes care of the self discharge but doesn't do much to lower the electrolyte levels in two to three months time.

  Instead of just switches, you could put in a switch and fused link in parallel on each bank to prevent a melt down, and still be able to maintain the battery bank while you are away. When the switch is open, the power will go by way of the fused link. Just a thought.

Blessings, Snow Crow

[thirteen]

I could use a small solar panel just for a maintence charge. During the winter months there is only about 2.5 hrs of sunlight during the day in mid morning (9-11)then it is gone until the next day. A lower fuse may be a the answer for when I am gone and using the smaller solar panel. I would be nervous about leaving it all alone for 3-4 months. The more I think about it I really need to figure out something that would work.      

[elvin1949]

thirteen

 If it was me-I would grab a HF 45 watt set of solar panel's.That should not overcharge--just maintain

a charge.If you are worried to much you could add one of Ghurd's kit's to dump any extra.

 That would be overkill but safe and cheap.

later

Elvin