Lowering Battery Temps (Fan Mod)

[gbkims]

Gene,

Excellent information. Without specialized equipment, It would be tempting to hold the highest possible load for one hour to check temperatures of components. For my single battery system, this will be during charging where a one hour charge is typical for my system at 56 amps or so.

What is the recommendation for making high current, low resistance connections? Crimp or crimp with solder? Use of a contact grease like below?

https://www.sanchem.com/electrical-c...lubricant.html

Jim

Jim,

I think keeping the bolted connections tight is key.

Crimped connections are what I use now.
I moved away from soldered connections to crimped as I went from being an electronics tech to an electrical tech and got involved with equipment wiring.

Joint Compounds. I've just used in outside environment connections.
I've used Kopr-Shield and "Penetrox E" for copper-to-copper or copper-to-silicon bronze.
I've used the Zinc based ones NoAlox, Penetrox A for aluminum-to-aluminum or aluminum-to-copper.

Thought back to the 2 month long downtime at one of our stations I had to work
The fire inside the switchgear was conductor phase to phase arcing and fire (probably from Corona degrading motor T leads insulation) inside metal clad switchgear that also shorted out the station's 12.47KV>4160V transformer windings.
The specialists from Dashiell just wanted denatured alcohol to clean the switchgear's bolted busbar, starters, arc chutes, cables & connections, etc.
No joint compound was used on any connections.

Couple of PDFs:
ELECTRICAL CONNECTIONS FOR POWER CIRCUITS https://www.usbr.gov/power/data/fist/fist3_3/vol3-3.pdf
https://www.bruker.com/fileadmin/use...ted_Joints.pdf

Thomas & Betts Kopr-Shield - https://www.mc-mc.com/ASSETS/DOCUMEN...0568638374.pdf
Penetrox E http://www.krimp-dsm.com/wp-content/...ccessories.pdf

[howson]

First Test with Fans

First--a couple of updates.

1) I am not going to use the BMV's relay to trigger the fans on and off. If the BMV's relay is used based on temperature, I'll get an alarm everytime the fans come on (because the temp will have reached the high temp setting in the battery monitor). That will be a nuisance.



Instead a separate temp controller with integrated relay will trigger the fan on and off. It should arrive early next week. (Later in this post or possibly the next I'll show how it will be used with the fans.)



2) Based on what's been learned from gbkims posts, I think the temperature being recorded by the BMV is the increase across the battery terminal due to current flow, not necessarily internal battery temperature. There's a critical difference! Unfortunately it is not possible to know the internal temperature of a Battle Born (what the battery's monitor system, or BMS, is "seeing"). In fact, I'm not even sure adding the fans will have any effect at all on the battery terminal temperature.

Is there an option? What I probably should have measured is the internal temperature inside the battery storage area. I still may have a way of recreating the original configuration...gotta think about some more.

See post 26 as from here out it's a continuation of that post.

I painted the screen and attached two S-7 120mm AC Infinity USB-powered fans to it.




These 120mm fans are configured to exhaust air out of the box and will be set to low speed (options are off, low, medium and high).

To force cooler air into the box an S1 80mm fan was mounted in the hole I'd made behind the Nautilus panel.



continued in next post...

[howson]

First Tests with Fans (cont)

The convenience of using these USB powered fans is they can be daisy-chained and then power will come from the CCGX.


Fans get their power as shown below.


So how will I integrate the temp controller? Below is the OEM wire diagram:



This is how I *hope* it can be wired/utilized. I don't think an on/off switch will be required as I'll use the controller's switch. The fans won't come on if the relay is not engaged.



As previously mentioned, the controller is not in my possession yet so the test I did was with the fans only. Those results next!

(to be continued...)

[howson]

First Test with Fans (Post 3 of 3)

So it looks like the fans did make a difference. The starting temp of the batteries was higher than recorded in post 26 (97 vs 95) yet after running off 10% of the battery SOC the temperature only increased to 104 (vs 108 previously).

More testing will be needed to validate the results--but it looks promising. (Is the difference worth all the hassle and work? A good question...)

In the future I'm going to turn off the solar input so the power drawn from the battery will be more consistent from test-to-test and over the 10% use of the SOC.

[Guest]

howson ,

Nice work Howard. Battery temperature with the BMV is most likely a measurement of temperature since a temperature model based on current would need inputs on the properties of the battery to accurately model temperature. In autos we use the battery temperature sensor on the negative battery post and can do so much more than just measure temperature. We will adjust the alternator charge based on battery temperature to maximize battery performance but will also calculate battery SOC (state of charge) as well as SOH (state of health). We also use this information to perform load shedding if that becomes necessary.

I'll need to cool my battery down since I'm charging at around 56 amps in my single battery. What is the maximum charge or load on your individual batteries?

Jim

[howson]

What is the maximum charge or load on your individual batteries?

Good question!

I assume it's the total current divided by 4 since I have four batteries. There's no way to know without a current measuring device in series with each battery's wiring.

Example: If the amperage on the BMV is -160A, each battery is supplying 40A.

The opposite is also assumed--each battery when charging will be the total inflow divided by 4.

[howson]

I've completed 2/3 of the testing with the fans that I want to do prior to installing a permanent solution, so I'm not ready to share that info yet. It probably won't be until the end of next week until I can get it all done. I've got to figure out how to present the data without overwhelming the post with numbers (that few will want to read).

The purpose of this post is to show how I'll control the fans. As previously noted, I don't want to use the Victron BMV-712's High Temp relay as that will trigger an alarm. Setting a lower temperature to turn on the fans (~95F?) will cause too many "high temperature alarms" that I don't want to deal with (emails from VictronConnect, the BMV beeping in the trailer, etc, etc).

Instead I'm going to use an independent temperature-driven relay in the Inkbird controller shown below. The temperature sensor and relay activation of the Inkbird is powered by 12v so I'll hook that up to my Battle Born battery bank. I'll send 5v (USB) power from the Victron CCGX (which has a convenient USB port not being used) through the relay to power the fans as shown in the diagram in post 33.

Happily, I found the Inkbird only pulls 52mA (.6W, that's POINT 6 watts, or less than 1). I was going to use the BMV's SoC relay to turn the Inkbird on and off, but with that low of a power drain I'm not going to bother. I'll just leave the InkBird on and use the power button when I want it off. (The .6W is with the cooling relay activated, too!)

Here's a few pics:



More next week.

Howard

[howson]

Messed around with charts in Excel to try and convey the results for comparison purposes. The question these charts are attempting to answer is, "Do the two vents added to the battery box make a difference to the rise in battery temperature under a heavy load?" First, the test conditions.

1) For all the tests the only item running is the bedroom air conditioner via the Victron inverter (shore power is off). Nothing else was powered in the trailer other than the normal 12v items (carbon monoxide, fire sensors, etc), the Victron equipment, and the Winegard router. Solar ("PV") was turned off completely, including power to the controller.

2) Each test started at (or near) 100% State of Charge (SoC) and ended when the SoC reached 90%.

3) A reading was taken once per minute. Additional readings were taken at each drop in SoC and each rise in battery temperature. Sometimes all three happened simultaneously.

4) "Vents" referenced in the charts are those I introduced into the battery box as shown in previous posts.

5) The time it took to go from 100% to 90% SoC is referenced next to the date and time the test was conducted, i.e. "(xxm)".

6) The interior bedroom's thermostat reading (in Fahrenheit) and the external temperature from an internet resource is also above each chart.

7) Three tests were run at different times of day for each configuration. (Note I haven't done the "Fans On" tests yet.)

The two sets of charts:





The answer to the question "Do the vents make a difference..." appears to be no. (!) I'm very interested to see the results when the fans are added. Many more questions than answers at this point...

Howard

[Guest]

howson Howard,

I ventilated my single marine battery box with 1 inch holes along the bottom of the box and two 1 inch holes at on the top/side of the lid to let the warmer air out. Started at a 30% SOC with a starting charge at 55 amps. Starting battery temp was at 61F where the temp peaked at 86F. So much cooler response, however with the cells being initially cooler it would take some energy to warm them up so the temperature rise most likely would be different if starting at a much warmer temperature. I'm all set for a dry camping trip this upcoming weekend to PA. More data will be needed in hot weather next year.
Interesting that the chimney effect is working since I could feel the low flow of the air exiting the box at the top.

Jim

[howson]

howson Howard,

I ventilated my single marine battery box with 1 inch holes along the bottom of the box and two 1 inch holes at on the top/side of the lid to let the warmer air out. Started at a 30% SOC with a starting charge at 55 amps. Starting battery temp was at 61F where the temp peaked at 86F. So much cooler response, however with the cells being initially cooler it would take some energy to warm them up so the temperature rise most likely would be different if starting at a much warmer temperature. I'm all set for a dry camping trip this upcoming weekend to PA. More data will be needed in hot weather next year.
Interesting that the chimney effect is working since I could feel the low flow of the air exiting the box at the top.

Jim

Thanks for the update, Jim.

I've had the minor inconvenience of a CAT II hurricane come through my area and now it's cooler than normal. Eventually I'll get back to this project and hope to have data to share.

[Guest]

Thanks for the update, Jim.

I've had the minor inconvenience of a CAT II hurricane come through my area and now it's cooler than normal. Eventually I'll get back to this project and hope to have data to share.

Stay safe Howard,

Jim

[howson]

After a significant delay I've *finally* installed the ITC-1000F Temperature Controller. Very pleased with the results.

The controller itself went into my "control panel" housing all the rest of my controls. For those that know the 315RLTS, the door was an OEM provided way to access the front storage passthru from inside the bedroom. I converted the space for my batteries and control panel. All of this is documented in my inverter install project.


The controller's interface is simple to use. I set the controller to turn on the fans when the temperature reaches 90F. There's a 3 degree offset (programmable) so the fans will run until the temp reaches ~87F.

There's a small power savings by having the fans off when not needed (and it's convenient to not have to remember to turn the fans on or off.)


Below is a rough sketch of how it is wired. The USB connections makes it very easy to disassemble, and since fans come with extensions it will be a simple matter of plugging in the USB if I want to add more fans. Nice! (See post 32 for more info on the fans themselves.)



Finally, the power switch on the face of the controller allows me to completely turn off the system if desired.

So the $10,000 question: Will the fans actually make a difference and lower the battery temperature on a hot day? At this point...no idea. But for the minor power draw the ventilation it provides can't hurt anything.

Any questions, fire away.

Howard

[dgerfan]

howson So in summary would you say that the fans have worked or not? Were they worth the time and hassle? The reason I ask is because I decided to install all the solar components in my 5ers front compartment to save space in the pass thru. However after living with he system for a year or so I have noticed that the compartment is pretty much the same temperature as the outside. An to address this I'm now considering moving all the components to the pass thru which would cut into the precious storage space. Also we mostly boondock or moochdock and rarely have access to a plug so the one A/C in our rig rarely runs. Even if we could run the A/C there is no vent in the front compartment so I doubt it would have any impact on cooling that area. For heating the area I think I'm going install a vent on the wall that the pass thru and front compartment share.

[howson]

howson So in summary would you say that the fans have worked or not? Were they worth the time and hassle?

I can't assert with facts whether they've made a difference or not. Anecdotally...I doubt it. The temp relay device works well and as intended, but the fans don't move much air. Pulling conditioned air from the camper through the battery box and then into the passthru is probably a better way to do it.