Jay, VRLAs tend to have a self-discharge rate, depending on the chemistry as low as 2%, but as high as 5%...
From: RE-wrenches [mailto:[email protected]] On Behalf Of Jay Sent: Tuesday, May 03, 2016 7:23 AM To: RE-wrenches Subject: [RE-wrenches] Winter Battery Maintenance Hi Steve Thanks I would only add that those self discharge rates are for good condition batteries. As they age, it increases. Question. How does the self discharge rates vary between, VRLA and flooded, or do they? Thx Jay Peltz power On May 3, 2016, at 7:09 AM, Steve Higgins <[email protected]<mailto:[email protected]>> wrote: Good Morning Wrenches! I’ve been watching this topic over the past few days and just wanted to put in my .02cents.. A Flooded Lead Acid Battery that is at 1.265 or greater SG will not freeze until it’s exposed to temperatures lesser than -90F or -60C. The same battery at only 1.220 SG will freeze at +20F or -6C. A flooded Lead Acid battery regardless of manufacture will self-discharge at about 8-10% per months when not under charge. For me, in most cases that gives you 3-4 months at best to disconnect a system. If you are decommissioning the system in Nov, recommissioning in Feb/March you should be okay. The problem is too many customers shut down in Oct, and don’t come back until March/April… if you get a late season cold snap this is when you have problems with freezing batteries. To prevent this there are a few schools of thought… One… You shut down completely and remove the batteries… This is kind of a pain and most customer really don’t want to lug batteries to and from their cabins. They may do this for a season or two, but eventually the lazy bug hits… Two… You shut down everything but the controller. You need to have the array installed so that it’s higher than the snow will be, and it’s suggested that you angle the panels 75+ degrees to keep snow from accumulating on the panels. In northern Canada/Alaska I’ve seen panels installed at 90degree to keep snow from accumulating… With this you need to disable Auto EQ, and I’d also suggest insulating the battery bank, and moving them together so they will help keep each other warm. When you return, you’ll have to remove the insulation, and separate the batteries again so you can get summer time airflow between the batteries. Generally leaving the controller on works well 99% of the time… unfortunately the only 100% fool proof way to not have frozen batteries is to pull them, or go with a AGM battery, although we did have a customer last season where the AGM batteries froze in an installation in Northern Canada. This is what happens when you install them outside on the porch! Steve Higgins Technical Services Manager P: +1.902.597.4020 M: +1.206.790.5840 F: +1.902.597.8447 Surrette Battery Company Exclusive manufacturer of <rollsebaad9>
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