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herringcove
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# Posted: 9 May 2017 01:20pm
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I currently have 3x250watt panels and 4x6Volt batteries in a 12V system. This system is 4 years old and we have been living off grid full time for a year. Last winter was brutal, we had the generator on for almost 3 months to keep the batteries fully charged. The generator is loud and problematic when the temperature drops to below -10C.
We are thinking of extending our home this year and doubling up the system, perhaps reconfiguring to 24V. I have read that it is not a good idea to add new batteries to an existing system, any suggestions what to do? I am located in Nova Scotia, Canada.
Thanks guys!
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ICC
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# Posted: 9 May 2017 06:14pm - Edited by: ICC
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Keep batteries warm in winter and they perform better. Needing to run the generator a ;lot might be caused by several things. Cold makes lead acid batteries lose capacity. Maybe you don't have enough panel watts to recharge with the limited winter sun.
Build a new 24 volt system, add more panels and batteries, maybe a new charge controller too. If you can find panels that are within 10% of Imp ans Vmp of the old ones you can add those together through one CC as long as it can handle the watts. Buy all new batteries, LiFePo4 if can can find the money otherwise use FLA. Before you spend a new nickle though figure out what is needed for battery capacity first. Then size the solar to suit the worst winter weather. I never run a generator but I am further south. If you got enough panels it can be done w/o a generator.
LiFePo4 batteries recharge faster than any lead acid based battery with the same amount of sunshine. The reason is that LiFePo4 have less internal resistance than lead acid.
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creeky
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# Posted: 11 May 2017 12:44pm
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Adding batteries to a lead acid pack is not recommended. The old batteries will quickly age your new batteries.
As icc points out, that's not the case with lithium. You can parallel in new modules at any time.
If you're looking to reconfigure I would go 48v. More efficient. Easier wiring.
Upgrading your system is a joy. Don't forget lots of people are just starting out and will be happy to buy your older equipment off of you. So it can be fairly reasonable.
Good luc.
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groingo
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# Posted: 12 May 2017 12:36am
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First and foremost keep the batteries warm, panels clean and make sure your charge controller is set properly and not defaulting to a lower max input voltage like 13.6 when you really need 15 volts as your max in winter.
Also keep close tabs on battery water levels and check your panels for power output.
Finally don' t forget to keep tabs on how much juice you are actually using.
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NorthRick
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# Posted: 13 May 2017 12:47pm
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First thing you should do is get a good accurate count of the amount of power you really use each day and then go from there.
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herringcove
Member
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# Posted: 16 May 2017 02:15pm
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Quoting: creeky Don't forget lots of people are just starting out and will be happy to buy your older equipment off of you. So it can be fairly reasonable.
That's a great suggestion!! Will give it a try.
Quoting: groingo you really need 15 volts as your max in winter.
I didn't think of that, I was just going with the manufacturers spec. It does make sense to max it in the winter, will try it next time.
The problem started because we were slack at taking regular readings, and when we saw the sudden drop in levels it took a few days to get it back up again. We have been keeping a better eye on the levels since then, hopefully it doesn't happen again. Also, I did one of those online energy calculations and have a better idea of what I'm going to need. Thanks for all your suggestions!
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