genset cooling fan discharging genset start battery

[Tenor]

Ok,
My 1965 kohler genset is charging my start battery at a nice clip.  However, when the radiator cooling fan kickes in, the genset does not keep up.  I have put a small 6 amp car charger on the start battery, powered by the AC created by the genset, and it almost keeps up.  This genset does not use an automotive style alternator, but rather makes DC current from the main alternator.  I don't really have room to add an alternator.

Here is my idea,
Using my Vanner equalizer, pull the needed 12v power to run the fan while the genset is running and charging the house batteries. 

Here is where it gets tricky.  Currently, I have a SMALL 110AH liquid acid battery bank and my Xantrex 4024 recomends a 5 amp charge rate.  So, if I expect that the fan is pulling 7 amps, should I bump up the charge rate to 12 amps?  My worry, is that when I'm charging the batteries using shore power, my fan would not be running and I'd be charging the batteries at a higher rate than is appropriate.  Any thoughts?  Sean - our trustworthy advisor?

thanks in advance!!

[Tim Strommen]

Your cooling fan is DC?  Seems silly to me...  Why not swap out with an AC fan?  That way you can tap power directly from the genny while running (gen on, fan on...), and when plugged into shore power, you can tap the shore-pole for power...

A high current DC load like that should really have its own AC/DC power supply (not the low power DC output for battery charging...) especially if you don't have an alternator.

-Tim

[Jerry Liebler]

Glen,
    If the fan is drawing 7 amps of 12 volts then this draw will be met if the 4024 supplys about 3.5 amps to the Vanner.  I'd go ahead and set up the 4024's current limit at 10 amps as this will be easily tolerated by your small battery.  The 4024 also has good voltage regulation so set the "float" voltage to 26.4 to avoid using excess water.
Regards
Jerry 4107 1120

[Tenor]

Tim,
I should have posted it, but I do have an ac squirrel cage fan pulling air through the radiator and out the bottom of the coach, but it is not strong enough to keep the temp down.  When I add the DC fan pushing air through the radiator, it runs nice and cool. 

Jerry,
Thanks!  That is the info I was looking for - even with a poorly asked question!

Glenn

[Len Silva]

Glenn,
I think you should put more effort into figuring out why the squirrel cage isn't doing the job.  Most rigs I have seen only have a 1/4 or 1/3 hp motor and more than adequate cooling.  Could it be restricted discharge or dirty blower blades, maybe the wrong size pulley or slipping belt.  If it's not running, the 12 volt fan would be restricting the airflow as well.

[Tenor]

Len,
My fan is working.  I double checked it.  I think it's just too small.  It has 3 speeds, slow slower and slowest.  It is direct drive, about 8 inches wide with clean blades (cleaned them myself) and it vents out the bottom of the original AC compartment through the original vent opening.   

Glenn

[NJT5047]

Len,
My fan is working.  I double checked it.  I think it's just too small.  It has 3 speeds, slow slower and slowest.  It is direct drive, about 8 inches wide with clean blades (cleaned them myself) and it vents out the bottom of the original AC compartment through the original vent opening.   

Glenn

Glenn, are you 'pulling' air with the squirrel cage blower?  If so, you may wish to try forcing air thru the compartment with the squirrel cage.    It'll 'blow' more than it'll 'suck'...sorta of odd sounding eh?   
Same's true with radiator fans.  Electric fans that 'pull' the air thru and not as efficient as fans that push the air thru the radiator. 
Most Jap gensets have a neat little high powered AC motor and fan assembly that drives the radiator fan from the AC output.  A new one would likey cost a fortune, but you may find a used motor on Eplace or at a repair center.
Japanese (not Chinese, but real Jap) parts are getting expensive.   After five years, my Yuasa battery finally died on my Yamaha diesel genset...battery was $317 bucks... I won't start on the 'dollar vs Yen' thingy..but...     Similar battery for a Honda Civic...$90 bucks with an 8 year warranty.     
JR

[Tim Strommen]

Glenn, are you 'pulling' air with the squirrel cage blower?  If so, you may wish to try forcing air thru the compartment with the squirrel cage.  It'll 'blow' more than it'll 'suck'...sorta of odd sounding eh?  Same's true with radiator fans.  Electric fans that 'pull' the air thru and not as efficient as fans that push the air thru the radiator.

Hmm, I've heard the opposite...  My bus has a pull (standard bladed fan), and I believe all MCI's have factory "puller" squirrel cage fans...  I had read that it is easier to create low pressure on one side of a radiator than it is to create a high pressure - something to do with the turbulent air created by a fan not being easy to push through a radiator core - versus generally straight air coming out of a core getting grabbed by a fan.

If the stock AC fan for the genny is truly a puller (i.e. away from the engine and exhausting out the the atmosphere), you should first check if the blower is sealed to the face of the radiator core...  any air leakage can cause an air stream "short circuit" (air just does a loop around the fan instead of doing any work).
{EDIT} If it's a squirrel cage fan is trying to pull towards it's drive shaft, it is probably spinning backwards.  The rotation should be such that the blades are moving towards the wider part of the outlet ductwork...  See very crude drawing below {/EDIT}

If your blower is on the inside pulling warm air thought the genny enclosure, it may be wise to re-work that (even if it is a factory configuration) as it can be improved...

-Tim

P.S. Remember, the alternator needs a cool flow of air, and so does the radiator.  The actual engine can live with the warm exhaust from the alternator blowing over it, but the radiator should have its own dedicated air circulation. -T

[Tenor]

OK,
Once again, I should have put in more info!  My radiator is remotley mounted in the old air condtioning bay, the genset is  in the first baggage bay.  The radiator is mounted to a shroud/shield

http://i613.photobucket.com/albums/tt216/tenor007/P1020193-1.jpg

Air is pushed through the radiator by the DC automotive van and is also pulled through a squirrel cage fan.  That fan is positioned with one side facing the radiator and the output directed out the floor using the original air conditioning vent.  The box/shield behind the radiator is pretty well sealed with duct tape on the gaps.  I think the true issue is fan speed.  It will be tricky to find the same size squirrel cage fan.  Thanks guys!

Glenn

[Len Silva]

Glenn,

Lot's of suggestions to deal with the 12 volt problem as a temporary fix.
The ultimate solution is to use an adequate blower in the first place.  Get a Grainger catalog and see what is available that will fit.  Even if you have to modify the compartment, you will be miles ahead with the proper cooling.

Get the paper catalog, their online info is cumbersome and limited unless you know exactly what you want. The paper catalog has lots of good information for selecting the right parts.
I think this is one typically used in this application: http://www.grainger.com/Grainger/items/4TL98

As I always mention when this topic comes up, include a sail switch wired to an alarm or shut down circuit to insure the blower is running before the engine overheats.

[NewbeeMC9]

Tenor,

I'm not sure from your picture, but it sounds like you could use your dc propellor fan only on the radiator and not use the squirrel cage fan at all.  May take some re-aranging but it would give you more vented space. ( and less power usage)

Also, does your genny have it's own start battery? or are you talking about bus start batteries?


if it is just the genny start, maybe you could consider a solar charger maintainer.

Let us know what you figure out

[Tenor]

Newbee,
The DC fan might do the job, but with the design of the shroud, you really need something to pull the air out of the housing.  The genset has it's own start battery.  I do have plans (and panels - just need the right controller) for solar, but they will be for my house battery bank which is 24V. 

Len,
I think I'll check out grainger for another motor, and use the fan blade and housing I already have.  Great idea for the long fix!

Thanks guys!

Glenn