Off the wall battery charging question.

[gomangodave]

I have been lurking in the background wanting to ask a question for quite some time.  You guys seem pretty nice and I am over the fear of getting flamed by now.  Here goes.

I Charge batteries using a 4KW Onan hooked to my outback inverter.  I was always curious to know if the MX 80 would handle a rectified output from a smaller generator and actually charge without using the inverters charger.  The book tells me that the charge controller will handle up to 150 volts of input, but they refer to solar input.  I would worry about the pulsed nature of the rectified single phase power.  Any thoughts?

Dave

[mbryner]

Hi Dave,

Welcome!  Yep, it works.  Know from experience.   I think I'm the only one here who's doing that.  In fact my Listeroid is charging the batteries currently through a rectifier, then though a large choke to smooth the ripple, then into the MX80.  

You'll have to put a 10 Ohm or variable resistor (low Ohms, high amp resistor) into the field coil to reduce the Voltage if you use an ST head.  I don't know about your Onan generator, but you will have to reduce the voltage a little because 120V AC rectified is 170-180 V DC, and will cause the MX80 high voltage sensor to trip @ 140.

Make sure you isolate the AC from the generator from your batteries with an isolation transformer, and use appropriate breakers.

The key is to use a large choke to reduce the ripple.   You can just use one side of large transformer for a choke.  ( + input on one leg and + output on the other leg of same coil.). Someone else tried feeding the MX80 rectified AC w/o smoothing it first.   The MX80 continued to charge but the screen got garbled and had to be hard reset every once in a while.

Look for my threads about it.   I don't have time to put a link right now but I'll find it later...

Marcus

[Geno]

I do it with a transformer to reduce the voltage and a high power rectifier I built. At high output the MX60 display would get scrambled but I think it was still charging. I fixed this with some 0.1 uF metal film caps on the rectifier (thanks Bruce) See this thread for lots of info. I don't have a lot of discharge cycles on the batteries but it's been reliable so far

http://www.microcogen.info/index.php?topic=500.0

Thanks, Geno

[mbryner]

Hi Geno,   Thanks.   Late at night last night my head was a little foggy and I forgot it was you who had the trouble w/ the garbled screen.   I didn't realize you were still using the setup -- thought you only did it as a test.   Cool, glad to know someone else is having success w/ that setup.

Marcus

[Tom Reed]

Geno,

My MX60 garbles the screen at high outputs from my PV panels too. I don't think it's your setup.

Dave,

I'm working on the similar, but using a 3 phase motor for the generator. Using 3 phase will hopefully create a smooth enough DC so the MX60 can be fed directly with a transformer and the associated losses.

[Geno]

It was kind of an experiment with that old, inefficient UPS I was using. I've dumped the UPS and now have a 2500 watt inverter.  It works fine but I usually power the house directly off the ST5/Roid.

That's interesting Dave. Bruce thought EMI might be the cause. Those caps might help.

Thanks, Geno

[mbryner]

That's a great idea: rectify 3 phase.   If you want to still use the generator for 120 or 240 it won't work, but for cleaner DC it should work well.

[admin]

welcome gomangodave!

no worries about getting flamed here, i think you will find the folks here to be pretty even tempered and very helpful.

unless you come in trying to sell blue pills for whatever ailment or porno you won't have any trouble from this group.

bob g