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Subject: 12 volt electrical Question?

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steveVa    Posted 12-07-2017 at 14:03:27 [URL] [DELETE]        [Reply] [No Email]  
  • 12 volt electrical Question?
  • 12 volt Electrical Question?
    I am building another bank of batteries for my solar collectors to batteries to 120 volt inverter electrical systems. I have several sizes of batteries available, but have always heard that you should use the same size batteries when building an array.
    I am currently just connecting 4 same size batteries in parallel, charging them with a solar controller and running an 800 watt inverter to get 120 volts. It works great, but will discharge the batteries more the 50% after a few days depending on the amount of things I run from the system.
    Is there a simple way to safely parallel different size batteries??
    I bought two high amp hour batteries, but they are smaller in size then the larger car batteries that I am using now.
    I have a marine battery isolator that allows me to charge two separate batteries without one discharging the other, but it seems to confuse the solar controller.
    I think it is because the controller cannot get the feed back it needs through the marine battery isolator.
    Is there a simple way to parallel different size batteries together?
    Also, if one battery is bad or has a bad cell, will the bad battery hurt others that are parallel with it?? Thanks in advance for any input.

    Loren, CA    Posted 12-07-2017 at 20:33:51 [URL] [DELETE]        [Reply] [Email]  
  • Re: 12 volt electrical Question?
  • To answer some of your questions: Yes there are 12 volt LED light bulbs that screw into regular sockets, I have seen them at Camping World, so any RV shop should be able to get them.
    If one battery has a bad cell when hooked up in parallel OR series the charger will continue trying to bring it up to set voltage, that will cook the good battery and ruin it. If one battery in a set goes bad, replace both; never use an old battery with a new one.
    Surprised that the battery isolator didn't work, don't know about that.
    You mention "high amp battery's", if that is cold cranking amps then you have the wrong battery for your application. That is a starting battery designed to produce high amps for a short period of time, batteries marked RV/MARINE/DEEP CYCLE are actually a combination style with thicker plates, but not true deep cycle. A true deep cycle battery has thick plates to produce energy over a long period of time, such as "6 volt golf cart batteries". Just bought two of these today for our motor home; $87 a piece at Costco. These batteries have a 210 amp rating at a standard 20 hour load.
    One of our neighbors up in the hills has an array of solar panels with ten of these 6 volt golf cart batteries hooked in a series/parallel configuration feeding his large inverter.
    Well this is probably more than you wanted to know, but I hope some of it helps you.

    steveVa    Posted 12-08-2017 at 17:36:42 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 12 volt electrical Question?
  • Thanks for the comments. The high amp hour batteries I was talking about are high Amp Hours, which are deep cycle. They are just expensive. I have used high cranking amp batteries in the past and they work fine too...
    What brand are the golf cart batteries from costco?? $87 is a really good deal for those. Are they 210 amp hours or 210 starting amps?? 210 amp hours would be great for $87. The best price I can find is about $2 per amp hour. A 100 amp hour battery is $200. I will need to check with our local costco. I have used automotive batteries in the past and they work fine. I found some maintenance free Delco batteries that lasted over 10 years.

    Loren, CA    Posted 12-08-2017 at 19:03:46 [URL] [DELETE]        [Reply] [Email]  
  • Re: 12 volt electrical Question?
  • The batteries at Costco are Interstate 210 amp hour deep cycle golf cart. I have had very good luck with Interstate over the years. I too have used starting batteries for small solar hookups, because that was what I had at the time, but replaced them with deep cycle when they eventually failed.

    Island Mike    Posted 12-07-2017 at 19:01:38 [URL] [DELETE]        [Reply] [Email]  
  • Re: 12 volt electrical Question?
  • Do not have all the answers. But on the boat: I have two six volt batteries connected to make one 12 volt unit. Plus a dedicated starting battery. I have a smart solar panel regulator. A 12 volt magic box that charges both batteries separately together. Both being 1 starter, 1 12 volt comprised of the two sixes.
    I also have a magic charging unit that does the same thing, but uses 120 volts to power it. Some disagree, but I only use one charging system at a time. Regulators get confused if more than one input. The other input is the alternator.

    Inverters use a lot of power. Something to do with sine waves.
    Everything you wanted to know about twelve volts, is in a book by that name.
    Might be Living on twelve volts. I use a 1000 watt inverter on the boat to charge small batteries and run the coffee grinder. Everything else like lights, fridges, navigation, stereo runs on 12 volts. Will do the same with my cottage on the Island.

    Island Mike

    steveVa    Posted 12-07-2017 at 19:22:25 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 12 volt electrical Question?
  • Very good point about staying with 12 volts and I do run several things including lights from 12 volts. I use the inverter to run 120 volt items, but turn it off when not in use to save the drain. The TV and computers are what I run from the 120 volt inverter. The 9 watt led light bulbs are also 120 volt. I wonder if they have 12 volt leds other then those car lamps with many bulbs?? I will have to look.

    Island Mike    Posted 12-08-2017 at 00:07:00 [URL] [DELETE]        [Reply] [Email]  
  • Re: 12 volt electrical Question?
  • Wot Loren said above. I forgot: Use matched batteries if you are joining them for more volts. Deep cycle is best for most everything. But Use a dedicated starting battery with a lot of cranking amps. CCA on the sticker.
    I have accurate amp meters on the boat, to measure amps out from nearly all devices, and amps in from the solar panels. The problem with the new style amp meters is, if they quit no volts flow thru, and what was downstream will not work. So I use a dedicated fused cig lighter style plug just in case. Plus another plug in type.
    LED bulbs can be bought in strips starting around 4 inches and going up. One regular 1157 type bulb will draw around .75 amps. 6 or more LED lights barely move the amp meter. LED bulbs that plug in like an 1157 bulb can cost a bunch.
    The strip over the sink in my rolling condo is 18 inches long. Most in the boat in the corners are 6 inches, except the main cabin which is about 12 inches I think.

    Island Mike

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