48V charging via ST generator and solar charge controller (no ST mod)

[BruceM]

It sounds like an  EMI problem-  and diode noise might be a big part of it.  Diode noise will get worse as current increases.  I'd try putting 0.1 uF metal film cap around each diode on the bridge. Pick the cap max voltage rating of at least double the transformer AC output voltage.  (1.4 times AC for peak DC plus some head-room.)

Is the negative leg of the DC supply connected to your system ground?  That might also be helpful.
(But check the documentation carefully first- this may already be done in the charge controller).

[mbryner]

A valiant effort, Geno!   Well, my toroidal transformers should be here soon.   Then I can discuss w/ BruceM some more on buying the next components in my filtering setup....

[Geno]

It sounds like an  EMI problem-  and diode noise might be a big part of it.  Diode noise will get worse as current increases.  I'd try putting 0.1 uF metal film cap around each diode on the bridge. Pick the cap max voltage rating of at least double the transformer AC output voltage.  (1.4 times AC for peak DC plus some head-room.)

Is the negative leg of the DC supply connected to your system ground?  That might also be helpful.
(But check the documentation carefully first- this may already be done in the charge controller).

Radio Shack has the caps for $1.49. I assume you mean they need to be hooked up from the top to the bottom of each diode?

I'll check ground on the Flexmax tonight. I did ground the case.

My losses with this setup are very bad. My UPS says its putting out 12 amps and my Killawatt in the engine room says 20. Yikes.

Thanks, Geno

[mobile_bob]

20 amps input and 12 amps output, hmmm 60%?

my earlier guess wasn't far off, but

it does work, and now you can work to see what can be done to improve the efficiency

gotta start somewhere!



good job, thanks for the update

bob g

[BruceM]

Just make sure the caps are metal film types, Geno.
Yes, one cap leg goes to each end of each diode in the bridge.

[yellowhead]

Thanks for starting such a great thread Marcus and to everyone else for their insights. I'm new to posting on the forum but I've been lurking for a while.

I was happy to trip over it because I'm going to be in a very similar position. I haven't purchased any of the kit yet but I'm strongly leaning towards Outback. However, it is clear from the Outback forum that the FX inverter series charger has poor power factor (especially under light loads) and this causes people all sorts of grief getting things to work with a generator. This seems to range from not working at all through to low charge rates and poor AC delivered via the transfer switch in charge mode.

For these and other reasons I had pretty much decided to feed the house from inverter output full time and charge the batteries directly. I was also planning to use an Outback charge controller to do this. I don't have a solar array yet but I might add one.

My initial though was to transform and rectify output from my gen. set (Changfa 195/ST7) and feed the output into the charge controller. I was expecting to have to do some filtering but really not sure how much I would need. I did query Outback on this approach and they seemed initially supportive but a subsequent question about acceptable AC ripple on the charge controller input met with silence.

I see that Geno has tried this approach (without the filtering) with some success which is great. However, it looks like the efficiency was not so good. I don't know what sort of power factor this setup is presenting to the head but it might be a consideration. I'm really not sure how well ST heads handle poor power factors ...

I'm currently exploring an alternative that I thought I'd throw out for comment. Folk on the Outback forum  pointed me at this: http://www.weirdstuff.com/cgi-bin/item/22081# Pretty cheap for a 3kw switch mode power supply. Better still it is power factor corrected and should present a nice regulated DC input to the charge controller without further filtering. Efficiency is listed at 90% for 230V in. Not bad. It might be possible to beat this with a good toroidal transformer/rectifier/filter setup but I'm guessing it would be close. And I doubt you could beat the price unless you had the parts just sitting around 

[BruceM]

Looks interesting but I can't open the specifications.  Oddly listed as a rectifier module instead of DC supply, also.

Could be a simple, cheap way to get your DC for charging!

[mike90045]

weirdstuff.com/cgi-bin/item/22081# was a hot swap rectifer pack.   Not sure what the specs were.

I've heard the outback gear is very "twitchy" about the power quality, it's expecting Grid.

iota chargers are reported to work down to DC, so maybe throttling back till the output sags, is a way to find the slow speed.   As the battery charges up, it will pull less amps.

[yellowhead]

Looks interesting but I can't open the specifications.  Oddly listed as a rectifier module instead of DC supply, also.

Could be a simple, cheap way to get your DC for charging!

I found the specs here: http://cherokeepwr.com/ds/CAR3000.pdf

The ad. quotes the model as CAR3010L1NH which seems to fit.

Simon.

[bschwartz]

and this:  http://www.datasheetarchive.com/datasheet-pdf/022/DSA00383318.html

[mbryner]

Awesome find, but its output is 48V DC which is only nominal battery bank voltage.   Not high enough charging.     Correct me if I'm wrong.   I got all excited....

I see that Geno has tried this approach (without the filtering) with some success which is great. However, it looks like the efficiency was not so good.

If you're talking about the efficiency of 60% quoted a few posts back, he's referring to the efficiency of the UPS he's using instead of an inverter, not the separate charging circuit.

Marcus

[yellowhead]

weirdstuff.com/cgi-bin/item/22081# was a hot swap rectifer pack.   Not sure what the specs were.

I've heard the outback gear is very "twitchy" about the power quality, it's expecting Grid.

iota chargers are reported to work down to DC, so maybe throttling back till the output sags, is a way to find the slow speed.   As the battery charges up, it will pull less amps.

The grid-tie Outback inverters are indeed quite picky about the AC input and Outback does not recommend them for off-grid/generator use.

The off grid FX/VFX series have specs more appropriate to generator input. However, I know people have trouble with the charger as it is not properly power factor corrected. Probably plays hell with those big box store 3-5kw sets. I'm hoping the ST will be able to keep it in line should I ever need it.

Interesting to hear about the IOTAs. I have the impression that most switch mode power supplies will work down to DC (someone please correct me if I'm wrong) and as far as I can tell the IOTAs are just a SMPS with battery charging smarts.

I am quite keen to spin my Changfa down to maybe 1400 rpm or lower when battery charging. Much quieter and I don't need full power. 3kw would be plenty. But thats pushing the AC input frequency limit on this 'weirdstuff' power supply (listed as 47-63Hz). If I can hold the voltage up (probably using some sort of AVR) does anyone know what might happen if I supply the unit with 47-40Hz AC?

Simon.

[yellowhead]

Awesome find, but its output is 48V DC which is only nominal battery bank voltage.   Not high enough charging.     Correct me if I'm wrong.   I got all excited....

The output can be adjusted up to 52.8V. I'm planning a 24V battery bank so it won't matter for me. Maybe 52.8V is enough to charge (and more importantly I suspect) equalize a 48V bank through the charge controller ...

[mobile_bob]

that is not high enough, it takes 57.6 volts dc for a flooded lead acid battery to be fully charge at room temp
and a bit over 60vdc to do an equalization of a 48 volt bank of flooded lead acid batteries.

most charge controllers such as the mppt units have buck converters, but i am not aware of any that use boost converters
or a combination of both, so they are not a good way of boosting the voltage in my opinion.

bob g

[Lloyd]

Has anyone looked at the Newmar stuff.

Lloyd

http://www.newmartelecom.com/Power-Modules/Power-Module.html
These Versatile Rectifier Modules function as either power supplies or battery chargers for 12, 24 or 48 volt systems; positive, negative or floating ground. They may be employed singly or in combination, enabling the installer to scale the system anywhere from 500 to 10,000 watts per rack. Units may be paralleled for N + 1 redundancy and alarm contacts allow local or remote monitoring. An optional DC quick connect wiring kit allows easy replacement of modules without system shutdown.

Power Modules may be used separately as a power source, or they may be integrated with the Power Function Manager to greatly expand the system capability with other functions such as digital output monitoring, powering multiple loads via circuit breaker distribution and low voltage battery disconnect.