Need to setup KID controller to maintain batteries over the winter

nlt999 · August 2015

Hi! New-user here....

We have the following installed near Dayton MT: 2 Chaori 280W, 24V panels in series driving a MidNite Solar KID controller with battery temp sensor installed. Battery bank is four Deka 8L16 370Ahr 6v batteries in series, and a Xantrex DR1524 1500W inverter. This installation is un-manned from end of August thru mid-June and I am trying to figure out the best way to set the charging parameters in the KID. In particular, how long to set the Absorb timer for so the batteries remain charged but are not overcharged, since there is no load on the system in the off-season.... only trying to maintain the batteries so they are not damaged while we are not there. Of course, winter temps get quite cold in MT so the batteries will remain cool or cold.

As long as the weather remains decent, I expect the batteries to be maintained in Float mode, but if the ground-mounted panels become snow-covered by deep snowfall, or the weather is completely cloudy for extended periods, the self-discharge characteristics of the flooded batteries may cause a drop in voltage, causing the KID to go into ReBulk mode and start a new full-charging cycle.

Current settings in the KID are:
Absorb Voltage: 29.1V
Absorb time: 120 Min
Float Voltage: 27,9V
Temp Comp: -3mV/deg C
ReBulk Voltage: 25V

Does anyone have any suggestions, and/or experience with maintaining unattended batteries over the winter months?

Thanks for any help! Nick

mike95490 · August 2015

So, you are going to have to figure out, WHAT your batteries drift down to, because every night, their voltage will drop. and that would normally trigger a re-bulk every morning. Be sure that any automatic EQ cycle is disabled. A week of cloudy with no loads would be no problem.

nlt999 · August 2015

Thanks for the input!
There is no auto-EQ on the KID controller, so that's not a problem. Would a ReBulk every morning be a bad thing? Have no way to know for sure how low the batteries will drift down overnight. Would it be better to lower the ReBulk parameter setting further? I assume that Float mode would then start up in the mornings unless bad weather had let the voltage drop further than normal overnight loss... that sound right?? Also, is the 120 Min Absorb timer too long in your opinion? Don't want to overcharge, especially since we won't be there to add water to the cells.

Thanks again for responding! Nick

Vic · August 2015

Hi Nick, nice to see you here - welcome to the Forum,

Personally, would suggest that you do not do a regular Absorb for Winter.

ReBulking is an interesting idea, but that probably should initiate an Absorb at a regular Abosrb voltage, but for a relatively short time.

Know that you are up against a Deadline, with your brother (the tender of tis system) scheduled to leave tomorrow 8/22/15 for about 10 months. To me, the largest issue is the very long absence duration -- about 10 months, which could cover one late Summer, to the early part of Summer, the following year. This seems TOO LONG a time period to expect Flooded batteries to remain unattended. The most-common scenario is for sites with harsh Winters to remain unattended for about 5 months, or a bit longer.

Had wondered about, perhaps having your brother take the batteries with him, for occasional attention.

Honestly, do not know the current state of functions available in the KID. Seems to me, you will want to Float the batteries daily, with a rare Absorb. Do not know if the KID can just Float daily, with ReBulk set to Absorb below about 24.6 V or so. There may not be a mode that allows Float only, except for a more normal Absorb, triggered by ReBulk ...

Know that you plan to have the Inverter shut off, so the only discharge on the batts is the KID's Tare loss, and that of the self discharge of the batteries.

Wish I had more to offer. Will look at the most-recent KID manual.

Good Luck! Vic

Mountain Don · August 2015

With an extended absence I would feel safest with taking the batteries out to someplace where they can be looked after. But that may not be easy / feasible....

It is possible for someone, anyone with a basic understanding of batteries and using a hydrometer to check sometime after the worst of winter is over? Someone who could add water and be there long enough to fully recharge them?

With all potential loads disconnected I can't imagine a scenario where The Kid would ever go into a rebulk. If my understanding is correct everyday the sun will wake up The Kid and it will go into bulk until the voltage reaches the absorb set point. Then it will absorb for either the programmed time or the end amps amount. I assume you have not worked with the system enough to know what end amps to use with the batteries. So I imagine a short absorb time should be okay as then The Kid will go into float for the remainder of the day.

I base all that on what I have done for the past 6 years. First I had an FM60, until lightning wiped it out. Now I have a Kid. I make sure the batteries are fully charged and the electrolyte topped up. I do an EQ and check all cells with a Hydrovolt hydrometer. Then I set the absorb time to 30 minutes and we leave. That will happen in late lare September or early October. We still may use our cabin for weekends at least a couple of times a month until snow makes the drive impossible. Most years that happens mid-December. For the next several months we may snow shoe in once a month and stay 3 days, maybe a week at New Years. By mid April we may be able to drive again. By May we will likely be back to weekend visits every other weekend. The point of all that is our batteries have done fine every one of the past 6 winters. I have never had to add water over any of those periods. I check because I'm there and have water stocked "just in case". I usually top up the water about 6 months after the last time in the fall. Going by an "eyeball" measurement I'd say they could go a few more months with no worries.

hing went wrong the batteries could be in trouble, maybe toasted or whatever. Ours are GC-2's so I take the chance; they are fairly low cost from Sams Club, but still going strong. I don't want to haul them out because we do want to be able to use the place now and then over the winter and I'm not about to snow shoe a single GC-2, let alone a set for 24 volts.

FWIW, one day I might like a set of LFP's. Leave them 2/3 charged and shut down everything and they'll keep fine.

BB. · August 2015

Keep charging voltage low/float. Boiling the batteries dry is the major problem. If they are very cold during winter, self discharge is much less. So float + cold should work fine.

Any sort of absorb or higher voltage charging worries me if more than 3 months between water checks. You might look at agm or sealed battery settings while gone.

--Bill

Vic · August 2015

Stating the seemingly-obvious;

It seems risky to set some new charge parameters on a CC that is part of a very new installation (I believe, from discussions, elsewhere), and then, immediately leave the site for about 10 months, unattended.

There is a reasonable risk that the system could do some unpredictable things during the long absence, and the variations in weather are probably large, over that approximate 10 month interval.

If the batteries cannot be moved, allowing some observation and maintenance, they could be damaged ... obviously.

Good Luck, Nick! Vic

nlt999 · August 2015

Thank you all for your input...... I really appreciate it!

Especially thank you Mountain Don...... your situation seems to fit pretty well for us.

No way can we haul the batteries home for the winter, the installation is on an island and the house about 100' above the water and only accessible by boat ....... can't just back up the car and load up the batteries!

I wound up having my brother set up the KID as follows:

Absorb Voltage: 28.8 (lowest-end of battery mfgr specs)
Absorb time: 30 minutes (as Don set his) (No End-Amps control available)
Float Voltage: 27.6 (lowest-end of battery mfgr specs)
EQ Voltage: 30.3 (mfgr recommended)
(KID only has MANUAL EQ, no automatic EQ)
ReBulk Voltage: 24.5V ( I think about 80% SOC level)

Had him check battery water levels
Had him run manual EQ last thing, after all loads were turned off

He will check the water levels and run a manual EQ first thing upon arrival next year, before turning on any loads.

We are crossing our fingers that this will work well enough to get us through this winter.... we'll see what he finds when he returns next summer! Thinking we may upgrade to the Classic controller, or an Outback controller if this doesn't work out well, where we may have more setup options, such as Skip Days.

Once again, thank you all for your responses...... greatly appreciated! Nick

mike95490 · August 2015

in addition to all loads being off, the inverter should be off too.

Sulfur · August 2015

with no load you should not lose enough water to matter. like previous post said, make sure the inverter is left off of course.

nlt999 · August 2015

Thanks for the reminder........ yes, the inverter is also off, so only loads are KID and self-discharge. Hopefully you are right and the water won't be a problem..... we'll find out next year!

Nick

Need to setup KID controller to maintain batteries over the winter

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