Battery enclosure construction

bc buck · May 2020

My battery bank was put in service in 2017. Im using 4 wet cell cart batteries. Charge controller is Morning Star MPPT with temp sensor programmed for 28 day equalize. 8o% of cycles are with ambient temp 40 to 10 degrees Fahrenheit. Other cycles up to 100 deg here in MO. The reason for this question is that I need to add water every 3 to 4 weeks whether battery bank is being cycled or not.
The enclosure is made out of well insulated cooler that is vented on both ends. Should a enclosure be this well insulated or am I doing damage to my batteries?

softdown · May 2020

Batteries last longer when they are cooler. Sometimes very much so. They also generate heat when taking a charge. We are encouraged to use battery boxes but not all of us see the need. The off gassing can build to dangerous levels in a closet or a box. I don't see that happening in a properly ventilated room of sufficient size.

One poster took advantage of his box by circulating water that was cooled by a chiller. I don't recall seeing him follow up with results though.

You could use a small fan to drive out the heat. I would strive to avoid battery box temps over 80F.

I think you may receive more technical answers from others. Basically - heat is pretty bad for batteries. Floridians may get 2-3 years, on the low side, out of their banks while Canadians may boast of 7-8 years - on the high side. It is pretty important.

mcgivor · May 2020

With regards to water consumption, having to top up on a regular basis could be attributed to having too high a charging voltage or the batteries have reached their useful life and are starting to decline. What are the charging voltages and did they always need topping up that frequently? Doing an equalization will consume water, doing automatically even if not required puts additional stresses on the battery, the need to conduct an EQ should be determined by SG differentials.

The cooler will definitely have a negative impact during hot weather because whilst charging the batteries will self heat due to their inherent inefficiencies ~20%, without air circulation the heat will manifest over time. This is something I've had a lot of problems with FLA batteries when temperatures are above 100°F for a few months the battery temperature can exceed the ambient air temperature, which is not good if the ambient is 100°F, water cooling is something I did with excellent results but it adds complexity.

BB. · May 2020

And insulated box is usually only needed for sub freezing operation (if the batteries are below ~45F, they have less "apparent" storage/AmpHour capacity). Lead Acid batteries themselves, work very well in subfreezing conditions--As long as they are kept well charged.. A fully charged lead acid battery will freeze below roughly -75F, but will freeze near 32F if it is "dead".

For hot areas, some people use basements or some sort of ground contact/berm/buried battery area (obviously, don't want flooding from rain/streams/etc.) to keep the batteries cool(er).

More or less, for every 10C/18F above ~25C/75F, your battery will have ~1/2 its aging life (at 35C/92F, your battery will age twice as fast).

And yes, you are probably reducing the batteries' life.

As said above, reducing charging voltages (Absorb, possibly float voltages) and making sure EQ is not too high of voltage/too long (or don't do auto EQ) is helpful (batteries get hot during EQ charging).

It is possible that during operation you will need to bump up the charging voltage (by a bit)--But during storage/float usage, too high of charging voltage will cause excessive water usage. If you can get it down to needing to add water every 2-6 months, that would be better. Also, make sure the plates are never exposed to air (quickly damages the plates).

-Bill

bc buck · May 2020

These batteries have always consumed this volume of water. I always add water while there is still a good 1/2" above plates encase something would happen and not make it back to farm for couple months.The charge controller is set, 14.7 absorption, 13.5 float. Trojan calls for 16+ volts for stratification but charge controller is set 15.4. Below 32 deg charge controller does increase voltage. Do you think I should leave lid open on enclosure during a deep cycle when ambient temp is above 70 deg? Been real happy with this setup other than the need to ad water. After 3.5 years the batteries still are giving me about same AH as what rated for.

Vic · May 2020

Personally, would remove the batteries from the "cooler", as it is really acting too much like an oven (as has been noted).

Would separate the batteries, so that there is about 2 inches -- 50 MM -- between them. A large-ish fan can help keep them cooler, if the ambient temps are quite a bit below the nominal battery temperatures. This separation can make the interconnecting cables slightly longer, but it is worth doing, if at all possible.

Here, we use a large fan to circulate air around the batteries, in a fairly small volume room, that has first priority on A/C use.\

\A battery box can really clean up the appearance of a power system, but, often at some cost.

Please try taking the SGs of all cells. Are they in the specified range?

Your Absorb voltage, and frequency may be too high. You could try reducing the Absorb voltage two or three tenths for about a week, or so, and see the effect that this has on the SGs.

EQs every month may be a bit too frequent. The variation in SGs will help you tell weather the batteries really need this much EQing.

FWIW, keep cool, Vic

bc buck · May 2020

Im going to start monitoring battery temps compared to ambient temp. Is what your saying above 50deg F you want to keep batteries at or below ambient temp and below 50 F its OK to use charging heat to warm bank. The SG all look the same so will turn off auto equalize and run when see SG variation.

Vic · May 2020

Hi bc buck,

Personally, allow the batteries to get as cold as possible. At about 32F, this quest is stopped. There is a smallish Capacity reduction with reduced temperatures, but that is not a factor, with the systems here.

Ok, you might try reducing the Absorb voltage a bit, and watch the SG readings, to see if you can maintain SGs in the target range.

EQs, every few months is not a bad idea. Prefer to do manual EQs, and monitor the battery during the process. But, that is just me.

It is good to not make too many changes at one time, as it can result in tail-chasing.

But, the bottom line, seems to be, that your batteries seem to be performing well. If you can reduce the water consumption, and still maintain SGs, then that should be a plus.

Good luck, Vic

Battery enclosure construction

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