Simple(?) solar question

[ratfink56]

95 Roadtrek with solar. I replaced the house battery recently. Regular pos and neg cables plus an extra pos and neg. Pos appears to be three wires. Did a voltage check the other day and batt showed 16.8. Immediately disconnected mystery ground. Van was not running at the time. And if the solar is producing shouldn't there be a charge controller?

[Ddarnell]

That might answer your question...theres no charge controller hence the 16.8v

[RoamingKat]

Yes, a charge controller is a good idea.

Also...consider putting in a power buss bar. You can put all the multiple connections there and then have only one wire to pos battery. Makes everything simpler for the future too.

[Blanch]

Or a malfunctioning one. My charge controller went wonky and let my batteries hit 15.7 before I caught it.

It didn’t go to float. This week it has been working just fine, but I am keeping a close eye on it.


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[sternwake]

16.8v is abusive to the battery, and some things like the absorption fridge circuit board have limits as low as 15.3v.

How much solar wattage is on the roof?
How much battery was it feeding?

My flooded group 31 needed something like 6 amps to get to 16.2v equalization voltage when otherwise fully charged, so I am guessing you have more than 150 watts in order to be able to bring your battery to 16.8v.

[tx2sturgis]

Or a malfunctioning one. My charge controller went wonky and let my batteries hit 15.7 before I caught it.

It didn’t go to float. This week it has been working just fine, but I am keeping a close eye on it.

Sounds like it went into equalization mode (sometimes called de-sulfation mode).

Some controllers will do this every 14 days, or 21 days, or whatever the time interval is.

[rvpopeye]

Agree ^
So , it's probably OK.

[Gr8ful]

Here's a great but a wee bit dated free course on batteries. I may post it by itself so if that's not allowed just delete this one please, Thanks!
https://batteryuniversity.com/learn/

[ratfink56]

Thanks for the replies. Just got back from a three day maiden voyage.

The battery is a group 27 marine battery, 75amp hours.

"How much solar?" Two panels of unknown origin and size. They look ancient and I'm surprised they work.

The solar hasn't been high on the priority list. So much deferred maintenance and cleaning to do first. Also, I am doing my test runs to COE campgrounds close to the house and they have electricity.

[Ddarnell]

Theres some 100w panels on amazon for $80. At least your cables are already ran. Can throw 1-2 them on roof or make a suitcase and get a modern charge controller.