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OT kind of, setting up two batteries in series


radioguy7

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Guys, getting ready to hit the beach this weekend and take the camper along. It now has just one 12 volt battery for power but I want to add another because last year there seemed to be too much drain on it when running the heat a few nights. I'm pretty sure I know hot to do it but wanted to tap the knowledge base here to be sure. So, how would I add another 12V battery in series and keep the voltage at 12V??

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My patio boat came with one deep cycle RV battery but we like to dock it at night and use the lights and radio so I added another identical battery hooked up in parallel. So far so good.

I converted my previous patio boat to all electric with a 24V dual prop. 130 lb thrust trolling motor. This motor would drain the batteries in only about 1.5 hours so I bought 4 6 volt golf cart batteries and hooked them up in series for 24 volts. That doubled my range but I still wanted more juice so I added 4 720 watt solar panels on the roof. Then I could cruise all day ! Very expensive experiment though.

Don't try adding a brand new battery to a used one though. The old one will drain the new one. Best to buy two identical batteries.

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If you connect the batteries + terminal to + terminal, and the - terminal to - terminal, you'll still have 12 volts, but more capacity. That's a parallel connection. It's the same type of connection you would make if you were using jumper cables to start your car.

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OldGuy is right on the money. In the wonderful world of diesel technology, where lots of cranking rpm is required to get light-off, sometimes three or four 12 volt batteries are connected in this same fashsion. Most of the semis in the fleet where I worked for some years used four six volt batteries on a 12 volt system - worked very well.

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radioguy,

You might consider splitting the alternator output between the two batteries with an automatic switch . The output from the alternator goes to the battery that powers your dashboard (the primary battery) and when it's full charged the automatic switch will charge the secondary battery until the primary starts to drop, and when it's charged back up the secondary battery resumes being made happy again. The big advantage to this setup is that even if you entirely drain the secondary battery overnight you'll still be able to start the engine in the morning, and that insurance is worth the price with the peace of mind it brings.

Just a thought.

-Randy

Edited by randroid
Incorrect spelling of 'with', and I'm only on my first beer!
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radioguy,

You might consider splitting the alternator output between the two batteries with an automatic switch . The output from the alternator goes to the battery that powers your dashboard (the primary battery) and when it's full charged the automatic switch will charge the secondary battery until the primary starts to drop, and when it's charged back up the secondary battery resumes being made happy again. The big advantage to this setup is that even if you entirely drain the secondary battery overnight you'll still be able to start the engine in the morning, and that insurance is worth the price with the peace of mind it brings.

Just a thought.

-Randy

Ok, I did the + to + and - to - part, that I was pretty sure of, but it is what randy is talking about that I had questions about. This is for a travel trailer so no cranking of any engine will be going on, just used as a power source when we are dry camping (no hookups). What I have now seems to draw the one battery down so far I need to plug into the truck and feed off it's batteries after a long night of use. The main thing that draws the juice down is use of the heater, but I am noticing less of a recovery time on the battery so I think it is feeling the hard use. So will both batteries be charged equally with just the input from the inverter/charger in the trailer? or do I need to set them up seperatly???

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I've never owned a trailer. Just motor homes. My motor homes "house battery" is charged whenever the engine is started and run for a while by the 85 amp alternator. Does your trailer battery get re-charged from the alternator in your tow vehicle or only when you plug it in to 110 at home or at a camp site with hookups?

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I've never owned a trailer. Just motor homes. My motor homes "house battery" is charged whenever the engine is started and run for a while by the 85 amp alternator. Does your trailer battery get re-charged from the alternator in your tow vehicle or only when you plug it in to 110 at home or at a camp site with hookups?

it gets charged either from the tow vehice or when hooked up to 110 thru the inverter.

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Hi,you might try googling Hellroaring Technologies for some ideas,Ralph

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