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Old 08-09-2015, 01:31 AM   #1
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Default Using excess solar energy to charge 2nd battery

i have a single 245w solar panel charging a 8d battery. The 8d battery runs a fridge full time, plus 1000w inverter when needed. This setup works well, fully charging the battery during my usage cycles. I have the factory aux battery to power other electric consumers. What I'd like to do is use the excess solar power to charge the aux battery.

My charge controller is Midnite Solar The Kidd. It has a load output, so I'd like to know thoughts as to how to utilize this output to funnel charging power to the Aux battery.

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Old 08-09-2015, 02:07 AM   #2
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Default Re: Using excess solar energy to charge 2nd battery

If you are happy charging only one at a time, then a simple A/B switch would let you select which battery to charge. If you want to do them both at once, and assuming that the two batteries are different, the best way would probably be a DC-DC charger. If the two batteries are identical (or can be made identical), then just wire them in parallel. If you are worried about priority loads, then you can use a smart isolation relay to protect one of the batteries.
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Old 08-09-2015, 02:33 AM   #3
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Default Re: Using excess solar energy to charge 2nd battery

Contact Midnight. If memory serves (and it may not) the Kid load output may only be active (or can be configured as such) to only out put when the charge regimen is complete. Midnight is a great company and is very respective to customer input.


PS. Thinking about the issue a bit more, your 245 watts of solar is only likely to put out a max of about 13 amps, assuming it is ideally aimed, somewhat less on a typical RV install. Give that your 8D has an ah capacity of ~225 ah (just guessing, feel free to adjust) it would like an ideal bulk charge current in the 25-30 amp range. Depending on your total daily ah load, yprovaly don't have much total charge daily capacity anyway.

Ideally as the Controller goes from bulk to absorb, you might have some capacity, but it is likely to be pretty small. May guess is your float time is pretty limited.

As a side note, I would seriously consider EQ charges more frequently since you are charging y battery at a sub optimal current. Give them a stout charge every now and again, (as well as a stout load now and again) to reduce sulphation.


Last edited by icarus; 08-09-2015 at 02:54 AM.
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Old 08-09-2015, 04:05 AM   #4
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Default Re: Using excess solar energy to charge 2nd battery

Check out using the Trik-L-Start. http://www.lslproducts.net/TLSPage.html

Its generally used to keep the vehicle battery charged when there's excess charge ability (or voltage) from the coach batteries. Might be able to set it up to charge your second battery from the main. Dunno...
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aux battery, charging, solar

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