lifepo4 and maxxfan

[mdkelley]

Hello,

I am new here. I didn't see a new member introduction so I will do that quickly before posting my question.

Matt from Michigan. I have a 1989 pop top 8' skamper on a 2004 2500 duramax. So far I have installed a MaxxAir fan, one LiFePO4 battleborn with a power dynamics Li single stage converter/charger, and removed the non-functioning 3 way fridge and am putting a 5000btu AC unit in that space. I also purchased a 2200 honda generator to use for off-grid battery charging and running the tiny AC unit. This camper follows a van conversion camper the wife and I used for about 4 years. Also installing a WiFi ranger and have a wilson cell booster. That pretty much rounds out my rig introduction.

My question: Will my power dynamics 45 amp LiFePO4 controller burn out my MaxxAir fan? I ask because I think it did! So, on to question2. If that is true (too much voltage to run a fan) what regulator do other use to get around this issue? I wired the converter in to my system to act as shore power and have a quick disconnect to put the battery into the system when not on shore power or if I need to charge the battery. I figured there is no reason to constantly charge the battery if I am on shore power. I am not sure if I need to get a 12v regulator that is rated at 45 or more amps since that is the output of the converter, or if the regulator's amperage rating is more for amp draw and not really an amp input rating. I would think maybe a regulator from a truck may work since an alternator usually puts out more than 45 amps but looking for some guidance from someone who has done this already so I can avoid any implementation headaches (learning curve).

Thanks,

Matt Kelley
Michigan

[MEXICOWANDERER]

I run my sticknbrick FFs on a 14 volt brick in reverse for years until the brushes or bushings give out. I have four Endless Breeze waiting for affordable surplus EB Pabst fans, which are brushless and have sealed ball bearings.

[pianotuna]

BFL13,

I've fed my fantastic fan 14.4 volts.

[BFL13]

Whatever I posted earlier in this thread could be me mixing up MaxxAir with Fantastic Fans! Do Fantastic Fans have the voltage issue

[mdkelley]

maxxair just called back. He said it was most likely that the board was burned out by my converter. He said a regulator would definitely be helpful for my system. They have an updated board they are sending me that can withstand 13.8v but the regulator would be a good idea to protect it in the future. He said it would be good to regulate the input to 12.4v. The callback today was really fast but it may have been a follow up from yesterday's call, not sure. I think if I would have just been using my stock converter and FLA battery I would not have had any issues (I don't connect the truck to the slide in camper at this time).

So, very helpful support/warranty service from maxxair for sure. I should have suggested they list the input voltage limitation in the installation guide to help others but it sounds like they are aware of the issue. If you are looking to get a maxxfan maybe consider you will need a voltage regulator if you use a high output charger/converter that is specifically designed to work with LiFePO4 like I am using.

[mdkelley]

Thanks, I just changed my order from the cheaper buck converter to this model that will work for up or down. Went with the 25 amp unit ($60) since it will cover the 5 amp fan and 8 amp fridge (the 120v heat element doesn't work on my fridge so I will be running it off converter while on shore power and propane when on battery, until I get around to replacing the 120v heating element).

25 amp should be plenty since the original "converter" (which was just a transformer that made a lot of noise when in use) was only rated at 9amps. This will simplify my installation as well. I was going to go with some relay/solenoids and wire those into the original electric panel that had a converter/batt/off switch to isolate things but now I will just wire the converter to the battery (via my disconnect plug) and the converter through this regulator to the fuse box. Then I can run shore power while charging my battery if I want to. When on battery only, the converter will be powered off but the battery will flow to the fuse box via the converter outlet lugs.

EDIT: Still waiting on warranty callback from maxxair. I recieved a callback from the tech support line yesterday after about 3 hours, and they immediately transferred me to another hold queue after telling me I needed to start a warranty claim and was in the wrong "area" for warranty claims. I called back today and was added into another hold queue. There is one person that does warranty according to the person who answered the phone today. There is no direct number or option to get to warranty claims, you have to wait on hold until a support person picks up or calls you back, then they transfer you to the warranty person which puts you into another hold queue that I was told is running about a day behind! Hopefully they call me back this week. If they don't honor their warranty I will just put a reversible variable speed motor controller on this unit and be done. It is beyond the return date and amzn sells the controllers for much cheaper than a new controller circuit board from maxxair. The motor controllers are most likely more robust as well, I think they are rated to operate up to 36v. I will still be putting the regulator in to protect any other 12v devices/appliances though.

[CharlesinGA]

I have read a number of discussions on this and apparently the MaxxAir Fans were not designed with a broad enough range of acceptable voltage. I have read of quite a few failures of MaxxAir Fans on discussion forums, and on one someone even quoted the MaxxAir specs which had a max voltage of less than 14 volts. Why this would designed that way is beyond me. I think that may be a non issue with newer manufacture models.

One thread did discuss a voltage regulator to install in the supply power to the fan.

Something similar to this was installed behind the trim or elsewhere in the fan circuit to stabilize the voltage.

Amazon - Cllena buck boost miniature converter.

Charles

[FWC]

mdkelley wrote:
ordering a 20A/300W buck converter step-down unit. Hoping that unit is large enough I can just wire it in before my distribution fuse box and filter both the battery and converter for the entire camper (maxxfan, propane furnace, 3 LED lights, USB power outlet, and 12v/propane refrigerator). If not, I can use it for just the fan/light circuit and buy additional units for other circuits if needed, it was only $15.

on hold for well over an hour this morning with airxcel to see if they will warranty this (less than one year since purchase, just installed it a month or so ago). Had to drop off and opted for the callback feature on their phone system. I am wondering if they either have a very limited staff, or just so many issues their customer support department cannot keep up...

Definitely report back on this. I have feeling that it won't work. Typically a buck converter (particularly a cheap one) need the input voltage to be 2-3V above the output voltage. So if you are planning on regulating at typical lead acid battery voltages (12 - 13V) it may work when the converter is on (14.6v down to 12V), but once the converter is off and the battery drops to 13.2V, the converter will drop out.

I think the real solution is to return the existing fan, and get one that works at actual RV voltages. This is not a converter/lithium problem but is a fan problem. Most lead acid batteries need to be charged up to 14.7V every now and then as well, so the fan is apt to burn out in that scenario as well. While you are at it, it may be good to return the converter as well and get one that actually works with lithium.

[mdkelley]

ordering a 20A/300W buck converter step-down unit. Hoping that unit is large enough I can just wire it in before my distribution fuse box and filter both the battery and converter for the entire camper (maxxfan, propane furnace, 3 LED lights, USB power outlet, and 12v/propane refrigerator). If not, I can use it for just the fan/light circuit and buy additional units for other circuits if needed, it was only $15.

on hold for well over an hour this morning with airxcel to see if they will warranty this (less than one year since purchase, just installed it a month or so ago). Had to drop off and opted for the callback feature on their phone system. I am wondering if they either have a very limited staff, or just so many issues their customer support department cannot keep up...

[Gdetrailer]

road-runner wrote:

Gdetrailer wrote:

You will have to chose diodes that have a high enough current rating for the max draw of the fan.

Have to worry about getting rid of the heat from the diodes, too. Drop 1.5 volts drawing 4 amps and you've got a 6 watt heater. Maybe put the diodes in the air stream the way fan dropping resistors are cooled?

Each diode drops .6V-.7V and at 4A that is a max of 2.8W dissipation per diode.

There are a variety of package types of diodes, some are heat sinkable on higher amperage diodes. Typically diodes with amperage ratings of 6A or less will not have heat sinks.

Alternate method is to use a bridge rectifier which has 4 diodes wired together in one heat sinkable package.

Here is pix of typical power supply use of a bridge rectifier..



Transformer connects to the bridge terminals marked AC, rectified (-)DC on one terminal and rectified + DC on the other terminal.

Now, if we get rid of the transformer, make those terminals not connected, place your Positive from the battery to the bridge terminal marked (-) and you can connect the + of the load to the rectifier terminal marked +.

Like this pix..



What happens is the diodes on the negative terminal will conduct the positive voltage to the terminals marked AC, the diodes going from the AC terminals will conduct the positive voltage to the Positive output terminal..

[otrfun]

mdkelley wrote:
No wall switch, I wired it in directly and also tested it after installing and it worked fine. It just hasn't worked since installing the new high voltage converter and knowing the converter puts out higher voltage I did a web search about voltage and the MaxxFan. What I found was that there were some online who had issues with their fans burning out the circuit board, and MaxxAir told them their fan CB could handle somewhere around 13.6v but any more would fry the CB.

@otrfun - So, it sounds like maybe a voltage regulator would be a good idea between the converter and the camper (not between converter/charger and battery though) due to the higher voltage the single stage PD unit puts out?

I do disconnect the battery when running on shore power/converter because I agree with what you are saying about constantly subjecting the battery to the high voltage bulk charge (since I read on the BB site they say not to leave their battery subjected to the bulk rate for extended periods). I did a lot of reading up on the subject before finally deciding to go with a converter that the battery maker recommended. I am planning to only use this converter to charge the battery when it gets low. I am installing two battery monitors also, one to monitor discharge and one to monitor charge rate and levels. I am honestly brand new to LiFePO4 technology and there is so much conflicting info out there it gets confusing. Thank you all for the help and info.

There are a lot of 12vdc voltage regulators on Amazon if you elect to go that route. Make sure you purchase one that can handle the appropriate current. I believe the MaxxAir fans draw approx. 3-4a (on high).

First time hearing that MaxxAir's have a max voltage rating of 13.6v. We used to own a 5th wheel toy hauler with two MaxxAir MaxFans. Regularly subjected them to 14.4v while bulk charging our lead-acid batteries and never had a problem. That being said, I suppose the MaxxAir's could be operating right on the edge at 14.4v. Could be possible the additional .2v a 14.6v converter produces could be pushing them over the edge, but who knows.

Ref your purchase of a single-stage lithium converter, you're not alone. We followed the same recommendations you did and purchased a single-stage, 14.6v Progressive Dynamic lithium converter (later sold it on eBay). According to BB, as long as you don't leave a single-stage 14.6v converter connected to a fully-charged BB LifePo4 for more than a week or so at a time, you should have no issues. Yes, manually turning a single-stage 14.6v converter on only when you actively need to charge will protect your BB LifePo4 from overcharging. However, for us, operating that way is just too awkward. We prefer the option of leaving a 2-3 stage converter on 24/7 and not worrying about it.

[Gdetrailer]

BFL13 wrote:
Would a diode work with the direction choices? I figure the two wires to the fan motor get swapped for pos and neg with the rocker switch so the fan will either suck or blow.

Add diode(s) before the direction change switch in that case.

[road-runner]

Gdetrailer wrote:

You will have to chose diodes that have a high enough current rating for the max draw of the fan.

Have to worry about getting rid of the heat from the diodes, too. Drop 1.5 volts drawing 4 amps and you've got a 6 watt heater. Maybe put the diodes in the air stream the way fan dropping resistors are cooled?

[BFL13]

Would a diode work with the direction choices? I figure the two wires to the fan motor get swapped for pos and neg with the rocker switch so the fan will either suck or blow.

[Gdetrailer]

mdkelley wrote:
From another forum
MaxxFan top voltage = 13.5V per Airxcel, Inc.

Once that fan gets to 13.5 is when its starts to cause concern.

Derek Hicks
Technical Assistance Coordinator
RV Products, a division of Airxcel, Inc.
3050 N. St. Francis
Wichita, Kansas 67219
Office: 316.832.4357
Fax: 316.832.3417
www.Airxcel.com

Well, for a "device" that is supposed to be designed for a RV that is certainly a stupid voltage rating.

Most devices designed for 12V use like automobiles are typically designed with the capability of dealing with up to 15V DC..

Not all is lost, one can add one or two diodes in series with the fan positive input lead. Each diode will drop about .6V-.7V, two diodes in series should get you about 1.2V-1.4V voltage drop. So, the fan now should be fine with converter voltages up to 14.7V-14.9V.

You will have to chose diodes that have a high enough current rating for the max draw of the fan.