The (old) battery storage question

MarkC

After searching deep cycle battery storage questions, it seems my dilemma is a little different.
I can "store" 4 deep cycle batteries (12V, ~150 ahrs) as spares for my golf cart  in a vented box inside my "solar shed".  Connections are set up to parallel these "spares" with my in-situ cart batteries.  The combined energy is enough to run certain ceiling fans, lights and a TV during the night in an emergency use case - and all is set up to do so quickly if an emergency (hurricane) happens by.   I bought the "spares" over a year ago (maybe 2) thinking it must be close to time of failure of the golf cart set (almost 6 years of torture by my Grandkids).  I recently put  the "spares" in operation and trying to:
1.  Decide when to buy a new "spare" set - would like to have them available IF the second set ever fails - not easy to get (good) new ones at this remote cabin.
2.  Decide on how best to maintain them in a South Texas (hot) shed.  Note that I've managed to use ventilation and reflective insulation board to essentially keep the interior of the shed approx same as outside - but still gets to 100 +oF a few days every summer.  No freeze problems!
3.  Bite the bullet and consider Li tech batteries at some point - $$$'s?

Any suggestions appreciated.  

mike95490

Seems like there is nothing wrong with the FLA golf cart batteries.   Just replace them, and in another 5 years, maybe the Li batteries will be practical.

Dave Angelini

If it has worked keep using the golf batteries.  You will have to figure a better way to keep that shed cooler or the value of long life with Li-ion will be negated. Even your flooded batteries do not like 100F and are not going to last as long as they could.

Many li-ion batteries monitor with their electronics the temperatures they are charged at and log this for warranty.

Estragon

> @MarkC said:
...
> 1.  Decide when to buy a new "spare" set - would like to have them available IF the second set ever fails - not easy to get (good) new ones at this remote cabin.

6yrs is pretty good for used/abused batteries. The second set WILL fail, the question is how (sudden death or slow loss of capacity), and when.

> 2.  Decide on how best to maintain them in a South Texas (hot) shed.  Note that I've managed to use ventilation and reflective insulation board to essentially keep the interior of the shed approx same as outside - but still gets to 100 +oF a few days every summer.  No freeze problems!

I'd dig a hole in the shed deep enough to moderate the temp of the "stored" batteries, and charge them every 3mos or so. Put the reflective board on top (but well above battery posts!).

> 3.  Bite the bullet and consider Li tech batteries at some point - $$$'s?

Maybe if the power to weight ratio would give you a hot-rod golf cart, otherwise I don't really see the point

softdown

I'd expect about two years at those temperatures. Have a basement? Basements tend to be much cooler.

MarkC

Good point about the temperatures affecting the LI tech batteries.  My Leaf's battery temperature runs about 85-95 oF normally in summer when kept in the garage overnight and not parked in the sun during the day. 

The one good thing is that the shed has a silver galvalume roof and often gets quite cool by morning (emissive cooling?).  The averaged temps during the summer are likely to be more like 85-90 oF.  I also have 4 "trickle" chargers - batteryMinder Plus that claim "desulphating" action.  Should I keep those on each battery continuously or for a few days every month or so?  In the "spare" set kept in storage, I discharged them (lightly) with my 48 VDC system every few months and recharged them with my 15 amp auto style to periodically mix the electrolyte.  They seem to be holding up OK in the cart, but its only been a few months.

softdown

MarkC said:

Good point about the temperatures affecting the LI tech batteries.  My Leaf's battery temperature runs about 85-95 oF normally in summer when kept in the garage overnight and not parked in the sun during the day. 

The one good thing is that the shed has a silver galvalume roof and often gets quite cool by morning (emissive cooling?).  The averaged temps during the summer are likely to be more like 85-90 oF.  I also have 4 "trickle" chargers - batteryMinder Plus that claim "desulphating" action.  Should I keep those on each battery continuously or for a few days every month or so?  In the "spare" set kept in storage, I discharged them (lightly) with my 48 VDC system every few months and recharged them with my 15 amp auto style to periodically mix the electrolyte.  They seem to be holding up OK in the cart, but its only been a few months.

We don't seem to recommend constant charging. I also don't believe the de-sulphating claims to be very worthy. 

Discharging them slightly with a 48 volt system seems like a bit of a project. 

The board members often tend to feel that stored batteries are toast by the "time you finish coffee." I live in a cool environment and have been able to store batteries for significant periods. One must keep them charged of course. That is much easier in a cool environ.

I still have a number of 8D's built in 2011 in service. Worth no more than scrap value to anybody else I supplement my existing bank with them. But my electrical demands are not very noteworthy. Below average in all likelihood. 

MarkC

I now do have the option of leaving the "48" volt wiring in place and use a 48 volt smart charger.  Either way, it's a 5 min job to hook them up as the wires sit next to the posts.  The more in series, the higher chance of balance issues?  Keeping them cooler is simply not an option.  It's half way through hurricane season now and forecasts are much lower chances due to El Nino - likely I'll wait until next summer to purchase the spare set.

Estragon

More in parallel = balance issues. More in series shouldn't be a balance problem, but worth checking once in a while, and charging a battery seperately if need be IMHO.

In higher temps, self-discharge will be higher, so charging more frequently (eg bi-weekly or monthly) at lower voltage (temp corrected, if possible) may be best. Others may disagree, but I wouldn't bother discharging beyond self-consumption. De-sulfation will likely be some sort of equalization at higher voltage and low current for some period after absorb and before float. Probably worth doing periodically.

mcgivor

Series is best for ballance, one option could be to use the 48v smart charger plugged into a timer set to come on for an hour each day.

MarkC

It is a 50 watt "smart charger" with desulfating circuitry (Granite manufacturer).  Easy to use an appliance type timer to turn it on daily for an hour or two.

I thought stratification was an issue with NOT discharging and bulk charging with FLAs - if left stored too long**?  Also, that minimal charge levels of .1C are needed.  These are why I "exercised" the spare set periodically.  Note that the spare set seems in great shape - time will tell!

 **However, I do hear "gassing" when charging even with the 48 volt 50 watt charger.

mcgivor

The 50W 48V charger on for an hour or so per day will  keep the self discharge to a minimum without overcharging, but being a smart charger that  shouldn't be a problem even if left on continually, but for the most part it would be doing nothing.

Estragon

My understanding is it's the gassing during the absorb and EQ stage of charging that mixes electrolyte and prevents stratification.

mcgivor

Yes that's true, it would probably be best to refresh charge, boost or equalize, before use after a long storage, a daily shot of energy would minimize the amount of refresh charge needed, electrolyte levels should not be depleted unnecessary in storage especially if unattended.

MarkC

Got it - thanks for all the advice. 

Going to watch forecasts - if things change and we get into the "cone of certainty  " of a hurricane this season, I'm going to buy the "spares" and set them up.  I realise this seems a little over the top, but we have actual experience in the past to our family - we spent over a week at our rural cabin while our Houston neighbors suffered without electricity for several days due to tropical storm Allison.  Luckily, they were able to use my home generator and bought a small window A/C unit for some local cooling - and to keep their refrigerator going.