DC Generator source

Cariboocoot · July 2012

There has been discussion on the forum regarding "direct DC generators". New member Rick Hoving http://forum.solar-electric.com/member.php?11062-Rick-Hoving runs a company called Alten which sells these DC generators. You can look at his web site at alten-dc.com http://www.alten-dc.com/

These may be the solution some of you have been looking for.

firerescue712 · July 2012

Re: DC Generator source

Is anyone familiar with these? The propane powered model looks promising. Thank you, Coot, for bringing this into the forums.

waynefromnscanada · July 2012

Re: DC Generator source

I don't see anything to explain the electrical, or mechanical difference between these DC generators and a regular automotive type rectified alternator.

inetdog · July 2012

Re: DC Generator source

waynefromnscanada wrote: »

I don't see anything to explain the electrical, or mechanical difference between these DC generators and a regular automotive type rectified alternator.

Just from looking at the pictures and the limited specifications, I see a few differences:

1. Engine driving them is diesel.
2. The alternator/rectifier used is rated for continuous use rather than being used beyond its design limits.
3. The big ones are bigger than any automotive alternator I have ever seen!

Other than that, I would not be surprised if the basic technology is very similar. Maybe the rectifiers are not built into the alternator frame, reducing heat problems?

waynefromnscanada · July 2012

Re: DC Generator source

Thanks for that info "inetdog", obviously I was not able to find and view the information you were looking at.

sawmill · July 2012

Re: DC Generator source

Thanks for the link to these DC generators. Although the electrical information seemed a little skimpy on their web site it appears to be a nice unit. Whether they are suitable for deep cycle charging remains to be seen. When time permits contact with the company will be necessary for particuliars. For example the charging specs of 28.8 v for the 24v unit did not say whether the full amperage is maintained at the 28.8 volt level or does it taper once the 28.8v is reached. 160 continous amps at 28.8 volts will have some serious heat removal problems.

I did not understand the 36 volt cut out in the specs.
I can't think of any situation where 36 volts would be reached in a 24v system except when the "magic" smoke is released. If anyone has experience with these units in a deep cycle situation, please chime in with your experience.

inetdog · July 2012

Re: DC Generator source

sawmill wrote: »

Thanks for the link to these DC generators. Although the electrical information seemed a little skimpy on their web site it appears to be a nice unit. Whether they are suitable for deep cycle charging remains to be seen. When time permits contact with the company will be necessary for particuliars. For example the charging specs of 28.8 v for the 24v unit did not say whether the full amperage is maintained at the 28.8 volt level or does it taper once the 28.8v is reached. 160 continous amps at 28.8 volts will have some serious heat removal problems.

Thanks for raising a question which others may also have.
You have to keep in mind that these are generators, not charge controllers! They produce DC which can be used directly to power DC loads and inverters and to charge a battery bank. But the connection to the battery bank must go through a charge controller, just as the output of solar panels would. The question I would have is whether a 28.8 volt output is high enough to satisfy a typical solar charge controller for a 24 volt battery bank, even if it has a separate generator input. If not, then a 48 volt generator could be used as input to an MPPT charge controller, but could not be used to directly drive 24 volt loads.

Cariboocoot · July 2012

Re: DC Generator source

Some additional info from Rick Hoving:

Our chargers are designed as a backup charger where we have in our 12 volt units a 14.8 volt bulk charge and a 14.0 volt float charge on a single selector switch. We do not see the need to make them a complicated "multi stage" charger as we've found the final 10%+or - of charge is a waste of fuel and takes quite a length of time. Once the batteries have a load applied, they are no longer in a "finished" charged state and the solar and/or turbine systems are far more sophisticated to apply this "finish" charge if felt necessary. All the Battery manufactures we have contacted (Lithium, Lead Acid, Nickel Iron) say our charger is perfect for charging their batteries and we have found total sucess implementing them in the field. They are self regulating in that as the battery bank recieves the DC energy and becomes charged, the amperage drops to a trickle as the batteries become energized. Typically, our customers run our chargers for 1 hour or less depending on the size of their battery banks and how much they have been discharged.

So it appears to be a typical fixed Voltage generator, switchable between 14.8 and 14.0 Volts (multiples). This is in my opinion too high for many FLA batteries and certainly for AGM's, as well as being too low for others (Interstate recommends 15 Volts Absorb). Since the Voltage appears not to be user adjustable (I specifically asked that question) this limits the applications. Ironically the Voltage is too high to do a simple Bulk-and-sustain charge.

As for what inetdog suggested, a PWM controller would be fine (with the appropriate generator Voltage) but MPPT controllers might not take kindly to the not-very-clean DC from a rectified AC source.

stephendv · July 2012

Re: DC Generator source

Why would these have to go through a charge controller? 14.8V seems to be a pretty good voltage to charge a 12V battery directly. Given how generators are typically used in off-grid systems, I would only let this thing stay at 14.8V for an hour or less. No need to go through a full absorb as that just wastes fuel.

What I don't understand is why they're running that motor at 3600rpm which is very fast for a single cylinder diesel. Since it's producing DC they shouldn't be limited by having to choose a 2 pole alternator to make 60Hz. That engine reaches best fuel efficiency at around 2000rpm... which seems a waste not to take advantage of DC output. Maybe adding the gearing would be too much of a cost?

Cariboocoot · July 2012

Re: DC Generator source

Unless I'm reading it wrong, it is a constant Voltage like all generators. In that case 14.8 is too high for many batteries, and if left connected they would be overcharged. Especially AGM's. The "switch" to 14.0 Float Voltage is manual, and also too high. It would work with Trojans, but I wouldn't leave them Floating at 14 Volts either. It seems to me these generators would require your full attention to make sure the battery is charged, not over-charged, and the gen not left running wasting fuel.

And sometimes in the off-grid world you do have to let the gen do the whole charge cycle. It can rain for days on end, especially if you're trying to replace the roof. :roll:

Rick Hoving · July 2012

Re: DC Generator source

Thank you for the interest in our DC Generators and please feel free to use this forum with any questions you may have or, don't hesitate to contact us directly for your specific application. We look at each individual installation to recommend the best fit to match voltage, amps required and depth of discharge.

We do not have a single product for every application and our Diesel Battery Chargers have different features than the simple gasoline powered units. There is not any need for a charge controller for any of our units. They simply connect directly to the battery or, bank of batteries with the appropriate sized cable set. The alternators we have directly coupled to our engines (gas, diesel and soon to be released propane) are automotive type that are internally rectified and self regulating. We modify the regulators of our gasoline and propane powered units where we add the two features to control the DC energy of turning the power on/off and making the high/low voltage selection.

We can provide these simple features with a diesel powered Battery Charger, but typically they are provided with an under voltage relay and autostart function where in a 24 volt system where the UV set-point (configurable) is set at <26 volts. We set the runtime for one hour (configurable) where typically this is plenty of time to recharge the batteries to 85-90% of their capacity. The Charger constantly monitors the batteries voltage and if it needs to restart after this hour it will run for up to another hour. When the units are installed and a typical load is introduced, you can idle the diesel engine back to an RPM where to engine is working at its peak performance.

This is a simple procedure and easy to tell where the optimal RPM is by listening to the engine and feeling the vibration produced. It most instances, it is between 1800 and 2200 RPM. The 24 Volt Diesel unit produces 28.8 volts of straight DC energy and as the batteries absorb the power, the amps slowly drops to a trickle as the batteries become charged.

We offer our Duke Diesel Battery Chargers with various features including on-board fuel tanks, cold climate kits, mufflers, full enclosures, cyclone filtration as well as our popular Remote Monitoring System (RMS). The RMS adds the capability to monitor you DC Charger from anywhere you have an Internet connection.

We recommend utilizing our DC Chargers as backup for your primary charging systems whether it is solar, wind, thermal or hydro. Our units do not include "multi stage" charging for finish charging as we find this wastes fuel and takes a long time where the engines run with minimal loads. With the introduction of a backup DC battery charger you can size you primary charging system and battery bank to a more affordable size knowing you will always have a backup in times where the primary system can't keep up and/or, your DC loads are higher.

Rick Hoving · July 2012

Re: DC Generator source

Hi Cariboocoot,
Thanks again for including my thread! Our chargers are self regulating - just like your vehicle. Your won't overcharge your batteries, just like your vehicle battery doesn't overcharge if you drive all day and night! We have had great sucess charging all types of batteries including AGMs and recommend deep cycle batteries in general for best performance.
Rick

Rick Hoving · July 2012

Re: DC Generator source

Greetings inetdog,
No need for charge controllers with our DC Battery Chargers. The alternators are internally rectified and self regulating just like the ones in your vehicle. As your batteries absorb the charge the amperage drops lower and lower and lower and the batteries only accept what they are capable of.
Rick

inetdog · July 2012

Re: DC Generator source

Rick Hoving wrote: »

Hi Cariboocoot,
Your won't overcharge your batteries, just like your vehicle battery doesn't overcharge if you drive all day and night! We have had great sucess charging all types of batteries including AGMs and recommend deep cycle batteries in general for best performance.
Rick

Thanks Rick. I notice that in your description you recommend using a timer to limit the amount of time the generator runs. In addition to saving fuel this will also remove the threat of long term overcharge. Common sense (so uncommon these days!)

Zero maintenance batteries for vehicles are built on the premise that a vehicle's charger will not overcharge them and so there will never be a need to add water. In practice that does not work. Some of this can be attributed to faulty voltage regulators, but some of it is just that the set point is actually delivering a constant overcharge which is electrolyzing water. An AGM battery, kept within its voltage limits, will just recombine the hydrogen and oxygen without venting, and a FLA battery bank can have water added as needed.

"In theory there is no difference between theory and practice. In practice, however...."

Rick Hoving · July 2012

Re: DC Generator source

sawmill wrote: »

Thanks for the link to these DC generators. Although the electrical information seemed a little skimpy on their web site it appears to be a nice unit. Whether they are suitable for deep cycle charging remains to be seen. When time permits contact with the company will be necessary for particuliars. For example the charging specs of 28.8 v for the 24v unit did not say whether the full amperage is maintained at the 28.8 volt level or does it taper once the 28.8v is reached. 160 continous amps at 28.8 volts will have some serious heat removal problems.

I did not understand the 36 volt cut out in the specs.
I can't think of any situation where 36 volts would be reached in a 24v system except when the "magic" smoke is released. If anyone has experience with these units in a deep cycle situation, please chime in with your experience.

Good question Sawmill!
In an extreme case (which we never have seen happen) the internal diodes my fail in the alternator and the voltage elevates to a maximum of 36 volts where the voltage regulator cuts out.
Rick

vtmaps · July 2012

Re: DC Generator source

Rick Hoving wrote: »

Our chargers are self regulating - just like your vehicle. Your won't overcharge your batteries, just like your vehicle battery doesn't overcharge if you drive all day and night! We have had great sucess charging all types of batteries including AGMs and recommend deep cycle batteries in general for best performance.

What about temperature compensation? In the winter my cold batteries need about 30.5 volts. In the summer, I want my charger to reduce its voltage as the batteries get warm. Actually, I think that is a bit of a safety issue.... thermal runaway can occur in the absence of temperature compensation.

--vtMaps

Rick Hoving · July 2012

Re: DC Generator source

vtmaps wrote: »

What about temperature compensation? In the winter my cold batteries need about 30.5 volts. In the summer, I want my charger to reduce its voltage as the batteries get warm. Actually, I think that is a bit of a safety issue.... thermal runaway can occur in the absence of temperature compensation.

--vtMaps

Our chargers are designed as a backup for your primary charging system and deliver either a single 28.8 volts as with our 24 Volt Diesel powered autostart units or, the selectable 28.8 High setting, 28 volts low setting on the simpler ones. We recommend running the chargers for an hour at a time to restore bulk energy and prevent battery damage from being overly discharged. Nothing can kill your batteries quicker that running them flat. We have systems installed at very remote locations in the Yukon and North Sea as well as the dessert SW at broad range of temperature extremes and never had issues with too low of voltage delivery in the cold or, overheating of batteries in hot climates. Folks that want to start the gas powered chargers and walk away, simply put an hour worth of fuel in the tank and refill it when they are ready to run again. We purposely make them very simple to install and operate with a minimum of items to fuss with. As your batteries absorb the energy and become charged, their ability to accept more energy dwindles to only a few amps and our chargers with their self regulating alternators can't increase the current if they wanted to. The voltage will remain relatively the same through the bulk charging, but the amount of amps delivered are minimal towards the end. Sophisticated multi-stage chargers are available for "finish" charging if you feel it is necessary to bring your batteries up to their last 10% charge, but once a load is applied the batteries will no longer be finished charged. If you want to safely, reliably and quickly replace the DC energy in your batteries, our chargers are for you!

Cariboocoot · July 2012

Re: DC Generator source

Rick Hoving wrote: »

Hi Cariboocoot,
Thanks again for including my thread! Our chargers are self regulating - just like your vehicle. Your won't overcharge your batteries, just like your vehicle battery doesn't overcharge if you drive all day and night! We have had great sucess charging all types of batteries including AGMs and recommend deep cycle batteries in general for best performance.
Rick

Unfortunately this is not true. Not all batteries take the same charge Voltage, and the settings on your generators are too high for many - especially AGM's.

So basically this is a hopped-up car alternator bolted to an engine. The lack of user adjustable Voltage is a significant shortfall of design. Of course the long wires from the DC gen to the batteries may cause a significant Voltage drop. Although most car alternators in fact temperature compensation it is no place near as accurate as the type used in solar charge controllers. In this instance it would be worse due to the lack of the ability to sense actual battery Voltage.

I can't say I'd recommend this product to anyone, due to the lack of adaptability to individual installations.

Cariboocoot · July 2012

Re: DC Generator source

I have removed Mr. Hoving's last sales pitch and am closing this thread. Regrettably he has been less than direct in answering legitimate questions about his product. If anyone has an further inquiries, please send them to him directly.

This thread will be moved to the product review section.

DC Generator source

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