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Battery Charging

May 01, 2017, 09:39:01 pm

For those with solar, when you are plugged in for 30 days or more at a CG do you leave the solar on or off? The freedom floats the batteries at 13.40V and stays there steady as long as its left on with the solar off. With both on the solar charger wakes up in the am goes through its charging sequence then floats at 13.65-70, both are temp compensated. When the solar goes through its charge stages it will go up to 14.70 for a bit before it goes to float. The solar controller is an Outback 80 MPPT. The solar and the freedom are both wired through the shunt for the link 2000 so it will read both,

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Re: Battery Charging

Reply #1 – May 01, 2017, 10:07:02 pm

I have 2 320 watt panels and same charge controller you have. I turn the fridge and inverter/charger off when I leave the coach unattended for any period. I leave one window open and the thermostatic fan set at 85 F.  On my victron monitor have never seen batteries [ 3 8d's] below 87% state of charge in the morning, and usually topped off by noon.. I figure leaving 110v hooked up to coach unattended for a while is a risk  I can avoid. Once had a mouse chew through a 110 wire, killed the mouse but did not trip breaker. Coach smelled pretty bad for a while.

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Reply #2 – May 01, 2017, 11:02:16 pm

Bruce that's a good question. I haven't heard anything definitive. Here is how I understand it.

As long as your chargers have charge profiles they will sort of self regulate. Basically the strongest one wins. The chargers will see the voltage and cut back when it sees the voltage is higher than what it thinks the voltage/amperage should be. So the charger who's charge profile says give it the gas will shutdown the other chargers. Hope that makes some kind of sense.

I leave em' all on most of the time. Sometimes I'll turn off the 120v charger to test the solar if I'm bored. DWMYH...

see ya
ken

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Re: Battery Charging

Reply #3 – May 02, 2017, 12:18:29 am

Ken that sounds about right. In my case the solar controllers temp compensation is a tad bit diff than the freedoms which accounts for the higher float voltage. Which brings me to the next question, with both systems on in the am batts are fully charged. Solar wakes up and for say and hour and a half goes through its sequence, in the process putting as high as 14.70v on already charged bank. Although only .5 amp, is the high voltage causing damage to the batts?

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Re: Battery Charging

Reply #4 – May 02, 2017, 12:37:38 am

Bruce, my 2 cents on this issue. Well for a start my coach is not pluged in even here at home and the solar does it all, always when on the road as well.
If (and that is a big one) we were plugged in at CG ,I would turn the inverter charger off but should it be lousy weather then I would turn it on as solar would have a hard time keeping them (batteries) up to snuff.
I would think that as Ken said, if the charge parameters are both set the same (or as close as possible) then one at times would overide the other and as these AGMs have a tolerance for up to 15+ volts I would not worry about them for a short time. They seem to be doing great as far as I can tell 6yrs old last month.
JohnH

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Reply #5 – May 02, 2017, 01:00:11 am

I'm with John.  If you aren't in the coach, and draws on the batteries are only parasitic, the chances that bad weather overwhelms any sort of solar charging system feels very slim to me.  Unless you are leaving a residential fridge on?  That's what the solar is for!  I wouldn't plug in.

However, if I were definitely going to be plugged in for an extended period - I would pull the fuses we wired into the solar panel lines.  For me the reasoning may be different than some - it's because our solar charge controllers send float charge at 13.50V, when our batteries are only rated to float at 13.20V.  I had trouble using the custom settings on the charge controllers.  For reasons more detailed than needed in this discussion, that float voltage difference is inconsequential under any sort of daily/nightly use, even extremely minor use that would pull the batteries to 96% by the morning. However, if the coach were plugged in and the batteries were at 100% full every minute of every single day, over a long period of time, the additional solar voltage would cause an issue with the longevity of our particular set of batteries.

Our magnum inverter/charger has custom settings I was able to exactly set according to the battery specifications.  So if I were plugged in at exactly the right settings, there is no need to have the solar as well, particularly because the solar charger settings are not "exactly correct" in our system.

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Re: Battery Charging

Reply #6 – May 02, 2017, 01:16:01 am

Also - for the second question - I'm surprised that your solar charge controller doesn't skip over the 14.7V full charge stage, 14.4V-ish absorption stage and go straight to float charge.  I'm guessing that's because it sees 13.4V from the inverter/charger and thinks "that's lower than what I expect to see, a float of 13.7 V" so it goes through a short charge cycle.  I wonder if you had the float on the charge controller set at 13.4V, would it see the batteries as 100% charged and skip over the charge/absorption stages?

If leaving the coach for a long period where batteries will be constantly left at 100% via plugged in, solar float charge would be the most important voltage to get in sync with your battery recommendation (and consistent with the settings of the inverter/charger).

Therefore - I would recommend you check you battery recommendations.  If the battery literature says float at 13.7 volts, then leave the solar on!  It'll doing it's job during the day, and the plugged-in power isn't hurting anything at night.  If the literature says float at 13.4V, then unplug the solar if you are leaving it for long periods.  Or, reprogram both chargers to match the battery specs as closely as possible, and see if the solar charge controller behaves differently before making a decision.  Temperature compensation isn't really a factor here - we're talking about something like 0.02 V in temperature compensation swings vs. 0.3 V in settings-based float charge swings.

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Reply #7 – May 02, 2017, 10:41:53 am

I allow the solar to do all of the battery charging on the coach all the time. I have the converter turned off. Four years ago I baked, boiled, broiled my 8d AGM's after two years and two days, significant since the company wouldn't replace them since they were two day out of warranty. That's another story told elsewhere on the FF. Anyway, at that time someone asked why I simply didn't let the solar to all the charging and I didn't have a good reason so that's what I do. Some winter days in FL the batt's get a bit down then come right back up when the sun shines. The controller is set for the AGM's and all seems to be well. ALL of our 12 vdc comes from the batt's and therefore the solar. Run the inverter when boondocking which is frequently. No problems.

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Reply #8 – May 02, 2017, 11:14:35 am

We keep the coach under a tarp as the roof of the garage is only one third done. I just keep it plugged into shore power for the OEM converter and monitor the voltages every few days from the dash digital meters. A HF $20 trickle charger keeps the engine batteries up. The coach batteries are too far away for the temp sensor to reach but since there are six of them and they are "outside," temp is not a problem. Eight years and all batteries are perfect (always keep fingers crossed).

Pierce

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Reply #9 – May 02, 2017, 05:45:02 pm

Don't know if you are in you motorhome during the 30 days.  Our solar is off at our panel & battery breakers when plugged in, but we are living in the coach when plugged in.  We set higher solar charge & float voltages when extended dry camping like at Quartzsite, then lower charge & float voltage when in storage without shore power.  But when there are two different charging sources, they usually 'conflict' and the one with the lower charge voltages thinks the batteries are full, when they may be quite depleted.  Charge profiles are based upon battery type, and 14.7 volts may be too high for some battery types.

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Reply #10 – May 02, 2017, 09:01:34 pm

We are living in the coach. The batteries are Deka AGMs. The solar floats at about 13.70 at 40 degrees.

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Reply #11 – May 02, 2017, 09:08:12 pm

These?

http://www.dekabatteries.com/assets/base/1740Intimidatordeepcycle.pdf

Try calling that number at the bottom to see if they can provide you with the recommended bulk, absorb, and float charging specs?  Note: sometimes those numbers are different for renewable charging sources  (solar)  vs. utility power.

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