Is it worth it to heat agm battery box

just starting

Would it be worth putting a 24 volt computer fan to push heat from my house to an outside box my battery's are in the - 3-7 c range would keeping the battery's around 50 f e worth the amps lost to the cold

CALLD

At those temperatures you are probably only getting 70% of your battery's nominal capacity, so I could understand why you would want to warn them up a bit. Getting the temperature up to about at least 10-15°C would make a big difference. I'm not sure a computer fan would manage that unless the air ducting and box were heavily insulated. If you can accomplish the required insulation then it's just a question of waiting the required time for the huge thermal mass of the batteries to slowly absorb the heat - possibly a couple of days...

It could be worth it if you do it right;)

just starting

The batt box is 2x4 construction with r13 and 2" blue foam board its only 3' from the house So I have some PVC the problem is that my woodburner is about 6'total from the box So I t will get heat at night

westbranch

what are the lowest winter temps you get?

just starting

-25f for a few days in a row weeksto months of -10f

just starting

I'm on the back side of pikes peak in colorado if you know where that is.

westbranch

well from me that would be the sunny south side...
My choice would be more insulation and if the power (W) used to run the fan is low enough over a 24 hr period in you opinion, go for it and have the warm air enter at the bottom, warm air rises, and exit out the top , use a smaller pipe for exit, and make a U shape down and up to stop siphoning of the warm air out and cold back in.

Batteries also warm a little when being charged, more if they are not in top shape.

You could also dig a pit for them next year and the ground will ameliorate the temps summer and winter...  insulated as well of course.

just starting

West branch how many w PV do you have total

westbranch

1680 W so far and 2 x that to come if needed....

just starting

I have 1500 panel ready with breakers for another cc and array I have an 894 ah agm bank kind of similar

just starting

1500 pv and 250 e panel

oil pan 4

Might be worth it if you don't over do it.

Lots of insulation around the box, maybe use 12 volt reptile warmer pads on timers and temperature switches to keep the pads off if above a certain temperature and only run them for a few hours aday.

just starting

I was just going to get a 24 volt temperature control and put the sensor on the battery post and stop at 50f

animatt

Are you running out of power? Or for what reason  do you want to heat the batteries.   As long as they are above freezing and you are not running out of electricity I see no point in heating them.

I am in what most would consider a tropical climate.  I would love to keep , my  batteries at such low temps. 
Battery life is extended  the cooler the battery.

Matthew

just starting

I'm afraid of voltage drop because of temperature a few times under load my voltage was at 24.7 at -6c if I can bring up the temp ill get 30 percent of bank power back
And more opportunity loads during sunlight +
less time to charge

just starting

When you look at using a 1/2 amp computer fan for 24 hours so 12 amps and a 894 ah bank 30 percent is a lot of lost power

inetdog

If you are planning to just vent the return air outside you will be adding a large heat loss to your dwelling space. But, especially if using FLA you have some issues to deal with when returning air to the inside.
A fluid loop with a heat exchanger on each end and simple convection for flow would be more thermodynamically efficient and not risk getting acid vapors back into the house.

just starting

I have a fisher mama bear in a 600 sf dwelling I have more heat than needed. I just plan on venting to the outside maybe some one way valves with ping pong balls to keep flow one way and to stop flow without a fan

animatt

It is lost storage capacity.  If you are not using the capacity makes no difference.  But if you. need the capacity definitely something to investigate.   Would seem really easy to test to see if it is worth it.

With 30% more capacity  would take longer to charge (assuming you are going to be using that extra juice). And opportunity loads can be somewhat independent of battery size (with in reason)

just starting

I've been hitting float everyday even on cloudy days most usage was 3.5 kw but want a chest freezer and washer I have a converted chest freezer to fridge and TV cell phones and x box for the kids five cfl and 2 gcb on 12 v for water pumping but have been charging them with 110 charger

just starting

Thank you about explanation of storage I miss understood.

just starting

Does that mean I have about 3 kw storage for two days at 50 dod

inetdog

just starting said:

Does that mean I have about 3 kw storage for two days at 50 dod

My understanding of the effects of cold on the batteries is that the amount of energy in them is the same, you just cannot get it out as well.
In which case you might try only warming the batteries if you see that you are going to be challenging your autonomy limit.
Cold batteries are going to last significantly longer before they degrade than warm ones too.

just starting

Do any of you know how to get a steady 24 volt 2 amp supply from 24 volt battery bank.During charge the volts go up the 30 sometimes don't want to burn up the fan or thermostat

Hill_Country

Just Starting....

We have a 48 volt DC system, but needed steady 24 volt DC for some of our home-circuits to run two DC fridge/freezers, 3 DC ceiling fans, and some DC LED lights at 24volts.  We ended up using a Solar Converters, Inc. DC-DC Converter that stepped down the voltage from 48v (nominal) DC to 24 v DC.  It keeps a steady 24v DC (actually we have it set to 28 v DC).  In your case, since you're going anywhere from 24 volts to 30 volts DC input (during charging, equalize, etc.) to a steady 24v DC output, you'd need something that takes a variable DC voltage in and outputs a steady DC voltage at an acceptable current (2 amps), which shouldn't be hard to find.  I did a quick search and found this for a variable 24 v DC input and a steady 24v DC output:  www.axiomatic.com/TDAX080200.pdf

Please note, I am NOT endorsing this product, nor do I have any experience with the product...personally, I would recommend you contact NAWS (the host of this site) and see what they have equipment-wise...they were very helpful for me when I was faced with the DC-DC conversion I was facing.  Hope this helps!

arby

I think when you use the bank, it warms itself up.
 Once upon a time,in extreme cold, people would turn on their car's headlights for a minute or two  before they tried starting the engine in their car.

softdown

Wonder what happened to this concept? So many of the old do-it-yourself type ideas were quite sound.


arby said:

I think when you use the bank, it warms itself up.
 Once upon a time,in extreme cold, people would turn on their car's headlights for a minute or two  before they tried starting the engine in their car.

vtmaps

arby said:

I think when you use the bank, it warms itself up.
 Once upon a time,in extreme cold, people would turn on their car's headlights for a minute or two  before they tried starting the engine in their car.

softdown said:

Wonder what happened to this concept? So many of the old do-it-yourself type ideas were quite sound.

The battery's ability to heat itself by discharge (or to be heated by charging) is a function of its internal resistance.  AGM batteries have very low internal resistance and therefore do not heat up very much when in use.

--vtMaps

BB.

One person here posted (long ago, as I remember) would use a genset (winter cabin) to get the place warmed and lights on. Had a battery heater in an insulated battery box. After 8 hours, cabin and batteries where warm and the batteries kept warm enoigh from daily cycling.

-Bill