generator for 24V DC system

System · September 2007

My cottage system is totally DC and mostly 24V. Both the panels and the batteries are in series/parallel to produce 24V. I use a step down converter to get to 12V for lights. I do NOT use AC for anything.

However, in the Fall, when the rains come, there are many days with no sun and eventually the system shuts down (LVD) at 21V. There is not much wind, no sailing here, so a wind turbine would not work.

Is there a way that I could connect a small generator to charge the batteries? Since the batteries are configured for 24V, what hardware would I require (charge controller, step down/up converter, ?).

THanx

crewzer · September 2007

Re: generator for 24V DC system

One solution would require a generator and a 120 VAC-to-“24 VDC” battery charger.

Each of your Dynasty batteries is rated at 12 V x 134 Ah, so the entire bank of six is rated at 24 V x ~400 Ah. A battery charger rated anywhere from 20 A (~5% of capacity) to 120 A (~30%) would be appropriate for your AGM battery bank, but larger chargers require larger generators.

An Iota DLS-27-25 charger (“24 V” x 25 A) with the optional IQ Smart controller should work well. Based on this charger’s specs, it should be a good match for an inexpensive but noisy 120 VAC generator such as the Coleman Powermate Pulse 1850 (1,500 W continuous). The Honda EU2000i generator (1,600 W continuous) is ultra-quiet, but costs more.

See: http://www.iotaengineering.com/dls2725.htm
And: http://www.iotaengineering.com/iq.htm
And: http://store.solar-electric.com/bach1.html

HTH,
Jim / crewzer

mike95490 · September 2007

Re: generator for 24V DC system

rojo wrote: »

My cottage system is totally DC and mostly 24V. Both the panels and the batteries are in series/parallel to produce 24V. I use a step down converter to get to 12V for lights. I do NOT use AC for anything.

You could make a Lawnernator, and set/get the regulator to 24V or use a truck alternator.
http://www.qsl.net/k5lxp/projects/Lawnernator/Lawnernator.html

If you need it to run extended and be easier to care for than a lawnmower engine, you could look into the quiet Honda Inverter series of generators, and use a 24V charger system

niel · September 2007

Re: generator for 24V DC system

mike,
were did you come up with that one, a ham to boot?
any,
didn't i remember seeing something like that from homepower too?
rojo,
it may be wise for you to devise something better to warn you of a low battery condition because at 21v those batteries are 100% dead and you should never go that far as it destroys a vast part of the batterys' life.

System2 · September 2007

Re: generator for 24V DC system

Thanx for the info. I will start sourcing the items. I had decided on the Honda generator series. I like quiet.

I had the LVD at 21.5 V last Fall but it would cut out too often. I could run one more day at 21V. Maybe short time gain for long term financial pain.

mike95490 · September 2007

Re: generator for 24V DC system

niel wrote: »

mike,
were did you come up with that one, a ham to boot?
any,
didn't i remember seeing something like that from homepower too?

There's been several conversion pages, I liked the Lawnernator the best, and it was a well done site. I've been involved in field days, and T hunts since high school, but inactive for years now.
There was one fellow, who had had an assortment of plates machined, to hold varied types engines (lawnmowers, vert shaft and horz shaft) and alternators, but I could not find his site, and I thought I'd had it bookmarked.

The Honda inverter generators are hard to beat for power in a small package

BB. · September 2007

Re: generator for 24V DC system

Your best bet for monitoring battery charge state (other than a hydrometer) is to look at one of these battery monitors...

Problem is the voltage cutoff point is very depending on rest time, load, temperature, and wiring. 21.5 VDC may be too low for zero or light load, but too high when starting a large motor.

By monitoring all of the current into and out of the battery--you are measuring something that is easily quantifiable (within 10% or so) regardless of load, temperature, etc...

Battery meters and monitors

Just make sure that ALL of the CURRENT flows through the shunt (many folks put the shunt in the negative lead as there is only one connection, unlike the positive lead which may have chargers, solar chargers, load banks, etc.).

-Bill

backroad · September 2007

Re: generator for 24V DC system

Is there any reasonable way to convert a 12 volt iota charger to 24 volts. I already have a 90 amp iota and am only using it to run my 12 volt fans for my swamp coolers since I converted to a 24 volt battery bank.

Dennis in Bagdad...........:D

BB. · September 2007

Re: generator for 24V DC system

Probably not--you can probably hook two in series to two 12 vdc batteries in series (check for ground isolation of the chargers).

You can call Iota and ask.

-Bill

James · September 2007

Re: generator for 24V DC system

here is a link to an outfit with a bracket for a small engine dc power source using car or truck alternator 12 or 24 volt.

http://theepicenter.com/tow02077.html

System2 · October 2007

Re: generator for 24V DC system

I decided to go with a Xantrex 2524 battery charger instead of the iota engineering. The reasons are that my solar charger is a Xantrex C-40, the Xantrex 2524 natively supported my AGM batteries and the also supports up to 3 independent battery banks of varied type.
It was easy to install.
- connect DC end to the battery bank
- connect the AC end to a dedicated receptacle (10AWG wire from charger to receptacle)
- 30 seconds to program charger
- type of battery (it tells you if you make the wrong choice)
- type of charging (2 or 3 stage)

You start the generator (Honda EU2000), run a cable from generator to receptacle and it starts bulk charging. It then switches to absorb mode and lowers the amperage it requires as it charges.

Approx 4 hours later, the battery bank is recharged.

THanx for all your help.

generator for 24V DC system

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