tstockma Posted August 13, 2021 Share Posted August 13, 2021 I plan to install one of the better Maxxair fans, I see many reviews say if voltage goes over something like 13.6, they automatically shut down. And solar systems often go over that. Anyone know of a cheap reliable way to do that? Amazon shows me power filters, step-downs, all kinds of options, & don't tend to be cheap. I just need something small & inexpensive to keep voltage within a normal 12 volt system's range. Quote Link to comment Share on other sites More sharing options...
Alvin Posted August 13, 2021 Share Posted August 13, 2021 I need to know the current requirements of your fan, but it Looks like some Maxxair 12VDC ceiling fans require about 12V and 5A. You could go with a large linear voltage regulatir such as Analog devices LT1084CT-12#PBF. DIGIKEY has them for $11.22. You’ll also need a couple of low cost caps (see the datasheet). Quote Link to comment Share on other sites More sharing options...
linda s Posted August 13, 2021 Share Posted August 13, 2021 Charge controller? Don't you have one. Your solar is to recharge your battery and if you don't have one your battery can be damaged. Battery connects to power center and that is the power you should be sending to your devices. Not straight from solar to appliances like fans Linda S Quote Link to comment Share on other sites More sharing options...
WME Posted August 13, 2021 Share Posted August 13, 2021 (edited) ^^ What she said. If your very concerned about your fan, most charge controllers have a LOAD out set of terminals. Hook your fan there. KISS Edited August 13, 2021 by WME Quote Link to comment Share on other sites More sharing options...
Alvin Posted August 13, 2021 Share Posted August 13, 2021 I would need to know the current requirements of your fan, but it Looks like some Maxxair 12VDC ceiling fans require about 12V and 5A. You could go with a large linear voltage regulatir such as Analog devices LT1084CT-12#PBF. DIGIKEY has them for $11.22. You’ll also need a couple of low cost caps (see the datasheet). Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 13, 2021 Share Posted August 13, 2021 Don't swat the details enjoy the ride worry less it won't bother a thing, The battery load alone will cover it. I have a maxair and run solar but it's only been 7 years now. Quote Link to comment Share on other sites More sharing options...
tstockma Posted August 15, 2021 Author Share Posted August 15, 2021 Thanks all - I'll check that Analog device & caps. I'm looking into this because I've seen some new Maxxair fans get review on Amazon stating they're pretty picky about getting too much current & cut out if they detect that (or even fry out because they're sensitive). I'll put a meter on mine - I plan to wire through the ceiling light next to the old non-powered 14x4 vent - and see if the solar is regulated well enough by the controller, that I don't need to worry about this. Quote Link to comment Share on other sites More sharing options...
neilp Posted August 15, 2021 Share Posted August 15, 2021 I have also read about 12v fans failing due to poorly regulated voltage. I think this is when people are connected to shore power and have an old power converter. I recently replaced my converter with a modern unit. I think this removes a potential fire hazard, increases the life of the coach battery (it manages battery condition far better than the original), and also provides better regulated 12v to appliances,. Replacing my original 12v fan is on the list of upgrades I'd like to do at some point, although there are several projects ahead of it. When I get to that point I won't have to worry about the 12v supply being out of spec. In my experience repairing electronics that are a few years old, it is not unusual for some components to be way out of spec after a few years usage. So these old units are likely all over the place. Mine measured closer to 13v than 12v although I never looked that closely. Quote Link to comment Share on other sites More sharing options...
fred heath Posted August 15, 2021 Share Posted August 15, 2021 Look into dc to dc voltage regulator. They’re reasonably priced on Amazon. That might stabilize the input voltage to the fan. The maxxair draws about 1 amp on low speed and 5 amps on high. Be sure the wire gage of the ceiling fixture is large enough to carry the necessary load. Also if it’s a “switched “ circuit the switch may have to be bypassed depending on where the power to the light originates. Quote Link to comment Share on other sites More sharing options...
linda s Posted August 15, 2021 Share Posted August 15, 2021 Why do you guys make this so complicated. My Maxxfan vent is powered from a ceiling light and has been for the last 15 years. The only issue he could possibly have is if he's trying to go direct from solar with no charge regulator and if so his solar is hooked up wrong. Linda S Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 16, 2021 Share Posted August 16, 2021 An unregulated solar panel is capable of like 21 volts but that is a direct connected to a device. In any case it will need to be regulated that is common practice. It is meant to be a battery charging device not a DC powering device. So connecting it directly to a fan is asking for it. I run a solar panel the controller is at the panel it is portable. A permanent setup would have the controller at the battery to take advantage of cable length voltage loss so it would be highly unlikely to over voltage any fan, lights etc. Quote Link to comment Share on other sites More sharing options...
Alvin Posted August 16, 2021 Share Posted August 16, 2021 I design power supplies for USA defense. The question was not whether the solar panels were connected in typical fashion. The question was about how to keep the voltage presented to the fan from going as hot as 13.6V…. Which easily happens with solar panels directly connected to a device. Yes most people use regulated battery voltage to run the 12VDC RV appliances… and those batteries are charged from any number of sources… vehicle engine, generator, shore power, … you could use hamsters in cages if you want. And if you want to charge your house batteries with solar, then you would use a solar charge convertor as you said. But if somebody wants to forgo the charger and connect the panels up directly, that’s doable too with a voltage regulator. Quote Link to comment Share on other sites More sharing options...
WME Posted August 16, 2021 Share Posted August 16, 2021 Hummm and how do you plan on running your fan at night to keep things cool? Oh I know 🤔 hook it to a solar charged battery. K.I.S.S. Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 16, 2021 Share Posted August 16, 2021 11 hours ago, Alvin said: I design power supplies for USA defense. The question was not whether the solar panels were connected in typical fashion. The question was about how to keep the voltage presented to the fan from going as hot as 13.6V…. Which easily happens with solar panels directly connected to a device. Yes most people use regulated battery voltage to run the 12VDC RV appliances… and those batteries are charged from any number of sources… vehicle engine, generator, shore power, … you could use hamsters in cages if you want. And if you want to charge your house batteries with solar, then you would use a solar charge convertor as you said. But if somebody wants to forgo the charger and connect the panels up directly, that’s doable too with a voltage regulator. Yes that is my point it is far easier/cheaper to direct connect to the battery with a solar regulator it also will allow you to run the fan when the "sun don't shine" with the added effect of charging the battery, both of the device are about the same price. An other comment don't buy a fan that can stand 13.8 volts common charged battery voltage. Quote Link to comment Share on other sites More sharing options...
Alvin Posted August 16, 2021 Share Posted August 16, 2021 1 hour ago, Maineah said: Yes that is my point it is far easier/cheaper to direct connect to the battery with a solar regulator it also will allow you to run the fan when the "sun don't shine" with the added effect of charging the battery, both of the device are about the same price. An other comment don't buy a fan that can stand 13.8 volts common charged battery voltage. You and I are in agreement. My comment was actually directed to Linda, and she not wrong; she makes a good point. But she doesn’t consider the case of getting the most efficiency out of a small under-sized RV solar array: The traditional method of running solar power through a charge regulator into a battery and then out of said battery and finally to the fan motor Involves several power losses. 1) charge convertor losses 2) battery charging loses (all batteries have internal effective resistance) 3) battery source resistance, and 4) device motor losses… ignoring wiring copper loses. To get the most out of available solar panels, it would be desirable to direct connect the solar panel to the fan… if possible. From a losses standpoint the best solution would be a dc-dc regulator but those are $50 and up, so I recommended an LDO (low drop-out) voltage regulator for the solar panel direct connection. Most of the dc-dc power supplies I design are 85% to 93% efficient where efficiency of the LDO will be somewhat worse. But nothing beats the price of an LDO. Quote Link to comment Share on other sites More sharing options...
WME Posted August 16, 2021 Share Posted August 16, 2021 People this isn't Rocket Science. The RV 12v system/solar charger is designed to accept all the inefficiencies. That's why you have a 21v+ solar panel charging a 12v battery. The energy loss through a solar controller is going to be about the same as the loss through a regulator. A no name 12v regulator is the same $$ as a no name 30A controller. If your flying to Mars then every last erg of energy is important, if you camping at the lake then not so much. Quote Link to comment Share on other sites More sharing options...
Alvin Posted August 16, 2021 Share Posted August 16, 2021 You want things to work as well as they can work? Or just kinda work lol. if I wanted to drive my Odyssey to Alaska, I would be very grateful to have things working quite well. I would probably even go to great lengths to point my solar array perpendicular to the sun. No harm knowing the rocket science details. Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 16, 2021 Share Posted August 16, 2021 Another thought a pip squeak solar panel may not even be able to run the fan direct! Quote Link to comment Share on other sites More sharing options...
WME Posted August 16, 2021 Share Posted August 16, 2021 6 hours ago, Alvin said: You want things to work as well as they can work? Or just kinda work lol. if I wanted to drive my Odyssey to Alaska, I would be very grateful to have things working quite well. I would probably even go to great lengths to point my solar array perpendicular to the sun. No harm knowing the rocket science details. Are you using a diode isolator or a solenoid in your system? Quote Link to comment Share on other sites More sharing options...
Alvin Posted August 16, 2021 Share Posted August 16, 2021 My guess would be that the fan requires 5A at 12VDC max then the solar panel needs a minimum of about 80 to 100 watts to run it at high speed. Perhaps 20 watts at low speeds. This is assuming about 21 volts output in full illumination and a voltage regulator to get this down to the voltage needed by the fan. The losses are mostly in the regulation. As daytime slips away Vout will drop. Quote Link to comment Share on other sites More sharing options...
Alvin Posted August 16, 2021 Share Posted August 16, 2021 11 minutes ago, WME said: Are you using a diode isolator or a solenoid in your system? Solenoid if I remember right. Haven’t touched that ever. Quote Link to comment Share on other sites More sharing options...
linda s Posted August 17, 2021 Share Posted August 17, 2021 They actually use very little power. Mine has only 4 speeds but the low and the high correlate exactly. It blows a lot of air. I almost never use more than low speed. I have also left mine running on low all day while I was hiking or fishing with no noticeable impact on battery charge. Linda S Speed Airflow (CFM) Current (Amps) Noise (dB-A) 1 274 0.23 32.0 2 364 0.32 33.0 3 486 0.48 36.2 4 562 0.70 42.6 5 655 1.02 42.8 6 756 1.38 48.7 7 845 1.83 51.5 8 934 2.36 58.0 9 1020 3.01 56.0 10 1158 4.20 59.6 Quote Link to comment Share on other sites More sharing options...
WME Posted August 17, 2021 Share Posted August 17, 2021 3 hours ago, Alvin said: Solenoid if I remember right. Haven’t touched that ever. Normally the alternator and the truck battery are hooked to the same post and the house battery is charged when the switch is made. If you need every last erg of energy for your house battery, hook the house battery to the alternator and the truck battery to the switched side. The loss to the truck battery won't prevent it from doing it's job. On a long ago MH I gained .5v at the house battery. A diode isolator loses .7v to both batteries and the truck still starts with out any problem Quote Link to comment Share on other sites More sharing options...
tstockma Posted August 17, 2021 Author Share Posted August 17, 2021 Yikes, I sure didn't think my little question would cause this much excitement! Fred, your comment about the dc-to-dc regulator is on the money for my purposes. Linda, I will also run off my non-switched power supply from the overhead light. The only reason I'm exploring this is recent models of Maxxair fans, the 10-speed ones, apparently are more sensitive to voltage fluctuations & people report both the fans switching themselves off at times (even when not connected direct to solar), & control boards frying (yes, modern Maxxair have actual "control boards" with logic, not just old fashioned sturdier soldered switches). In my case, I've got a pretty big solar panel...the fan is very efficient, 5 amp on high...I'll usually run at slower speeds, like that 1 amp low setting...I'm not worried about drawing too much power. I'm just wanting to protect what apparently is a somewhat delicate but otherwise very well reviewed roof vent fan. That said, I don't want to interfere with a spirited technical brouhaha, so don't let me stop the discussion.... ; ) Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 18, 2021 Share Posted August 18, 2021 I just read several articles from various camper sites about the Maxxair 10 speed frankly I would stay away from it! Quote Link to comment Share on other sites More sharing options...
tstockma Posted August 25, 2021 Author Share Posted August 25, 2021 On 8/18/2021 at 9:23 AM, Maineah said: I just read several articles from various camper sites about the Maxxair 10 speed frankly I would stay away from it! Thanks, I'll research outside of just the Amazon reviews. Recall a site or two which you'd send me towards? Quote Link to comment Share on other sites More sharing options...
WME Posted August 25, 2021 Share Posted August 25, 2021 Amazon 12v-12v regulator 5 amp https://www.amazon.com/DROK-Waterproof-Automatic-Regulator-Stabilizer/dp/B018WZK5XQ/ref=pd_sbs_3/139-1095205-3096227?pd_rd_w=NZCCd&pf_rd_p=0a3ad226-8a77-4898-9a99-63ffeb1aef90&pf_rd_r=A0MTCZY2TJWB6THG2K7Y&pd_rd_r=553a93cc-0f86-452e-86a0-51eac251ae89&pd_rd_wg=IFBpG&pd_rd_i=B018WZK5XQ&psc=1 They also have a 10 amp version https://www.amazon.com/Cllena-Automatic-Converter-Regulator-Waterproof/dp/B08KZPXK63/ref=pd_di_sccai_1/139-1095205-3096227?pd_rd_w=bJKEy&pf_rd_p=c9443270-b914-4430-a90b-72e3e7e784e0&pf_rd_r=R98SJKKJGTGM0GXKHE1C&pd_rd_r=654ce85e-bf7a-4013-b95c-0471680f644d&pd_rd_wg=qJsh5&pd_rd_i=B08KZPXK63&psc=1 My current rig has a dedicated 12v line for the factory installed fan so the 5 amp unit is OK Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 26, 2021 Share Posted August 26, 2021 On 8/25/2021 at 12:32 PM, tstockma said: Thanks, I'll research outside of just the Amazon reviews. Recall a site or two which you'd send me towards? Google Maxair fan problems. I think the simple ones are very good fans I have one it has a rain sensor and reverses that works well and moves a lot of air it is a 3 speed no frills unit. What bothers me is the added voltage regulator to a 10 speed unit we are dealing with battery voltage most fan cover a wide range of battery voltage and really don't care, if it's low they tend to run a bit slower if it's high they run a little faster not big deal so the regulator is more about protecting the gadget part then the fan. Camping should be simple. Quote Link to comment Share on other sites More sharing options...
Nam Posted December 23, 2021 Share Posted December 23, 2021 I really thing we should do nothing...just to recap. Hook up the fan to near by 12V source and call it the day... Quote Link to comment Share on other sites More sharing options...
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