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Old 04-21-2015, 12:52 AM   #1
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Solar + alternator = faster charge?

My wife asked me this question tonight and I couldn't answer. She wants to know if the new solar I'm adding will allow the house battery to charge faster while driving. In other words, are the solar amps additive to the alternator amps, or is it just one or the other?

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Old 04-21-2015, 07:14 AM   #2
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Re: Solar + alternator = faster charge?

My setup seems to take what it needs from both as needed. Typically my solar charger cuts out while driving at speed while the voltage is higher from the alternator. If I stop at a light while the sun is out I see the solar charger start to contribute a charge. Again it shuts down when I take off and the alternator is pumping out more.
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Old 04-21-2015, 08:38 AM   #3
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Re: Solar + alternator = faster charge?

If the sun is shining while you are driving down the road, they will both charge but the solar panel puts out a mouse-farts worth of power compared to the alternator........

As Brent mentioned above, when the alternator/voltage regulator is charging it's usually around 14V or so; when the solar controller sees the battery voltage that high it will go into float mode.
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Old 04-21-2015, 08:52 AM   #4
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Re: Solar + alternator = faster charge?

Quote:
Originally Posted by boywonder
mouse-farts worth of power
Must be an engineering term.
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Old 04-21-2015, 02:08 PM   #5
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Re: Solar + alternator = faster charge?

Quote:
Originally Posted by sbgrimm
My wife asked me this question tonight and I couldn't answer. She wants to know if the new solar I'm adding will allow the house battery to charge faster while driving. In other words, are the solar amps additive to the alternator amps, or is it just one or the other?
It's how I found out that my stock alternator couldn't keep up with the load the stuff in the van pulled. With the Starcool running while driving, I found that the charge dropped into negative zone pulling power from the battery system when I drove through shade. In sun the charge showed a positive flow. So in a sense it did add to the charge. It also made me aware I needed a larger alternator. With the new high amp alternator, the solar controller jumps into its float much quicker.
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Old 04-23-2015, 01:29 PM   #6
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Re: Solar + alternator = faster charge?

Not to hijack, but I'm going to go solar because the alternator barely contributes a charge. I will go down 0.1-0.2 VDC on the battery per day, just with the fridge on 2/5 and 4 hours of driving. Is this a good indicator that my alternator can't put out enough power?

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Old 04-23-2015, 02:27 PM   #7
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Re: Solar + alternator = faster charge?

4 hrs driving everyday? Freeway driving?

Ran my batteries down yesterday with things I was charging and using. On the way home the Alt was putting out approx 145 amps with approx 5o of that going to my house batteries.
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Old 04-23-2015, 04:07 PM   #8
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Re: Solar + alternator = faster charge?

Well, yesterday was 8 hours driving and the battery still need a few hours from shore power to top off.

What is a recommended alternator size for charging a 4D in respectable time? I have the 5.4 engine so I'll be checking on what's available (and other threads, 'cause that's got to be covered somewhere!)

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Old 04-23-2015, 04:13 PM   #9
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Re: Solar + alternator = faster charge?

So you have a house battery and chassis battery correct?

8 hours you should be able to top up easily unless you have a huge draw while driving.

To choose the best improvement route you really need to identify what your total draw from all accesories is first and then work backwards through the system.

Do you have a way to measure draw for everything?
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Old 04-23-2015, 05:13 PM   #10
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Re: Solar + alternator = faster charge?

That's correct if you're only looking at the output. I've driven with everything off and still not got a satisfactory charge rate. That's why I'm looking at the input now

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