[RE-wrenches] Is there a charge controller do this?

[Solar]

I think DT is on the right track. We have a relay driver set up at the college. We have it set it for turning lights, alarms and motors on a certain voltages. The students also do a lab with it. It could do exactly what DT mentions. 

Jesse Dahl

NABCEP PV Installation Professional
IBEW Local 292 - Electrician 
Electrical/Solar PV Instructor - HCC

Sent from my iPhone

> On Jan 29, 2018, at 9:07 PM, Darryl Thayer <darylsolar1 at gmail.com> wrote:
> 
> Hi Friends, sorry to be slow.  This fits the Morningstar relay driver exactly.  It can look at the battery voltage and activate relays in multiple fashions.  When the battery voltage is low at the recharge point, the relay driver can be set to start a two wire or three wire generator.  This can be done with the relay driver using a start delay or not.  Then when the generator is running after warm up, the relay driver can close a relay/contactor to load the generator.  The voltage comes up to absorb volts where the battery will absorb a lot of current.  It is possible to use the relay driver to insert a resistance via a contactor or just let the battery go to a higher voltage and shut the generator off.  For example start the gen at 50 volts, let it charge to 58 volts, and shut it down. If the generator is large the battery voltage will rise too quickly and a relay/contactor with resistor should be used.   There are a number of control scenarios.  
> 
> I think by the description the generator will overload and depending on generator field control either stall or reduce speed and keep running.   Good luck 
> 
>> On Sun, Jan 28, 2018 at 9:23 PM, Mac Lewis <maclewis1 at gmail.com> wrote:
>> Hello wrenches,
>> 
>> I'm working on 3 off-grid telecom sites.  They are designed to operate solar only under most conditions but the project manager ordered a custom-built 48 VDC generators, intended to be used as the battery charger/backup power for the site.  These are ~20 kW generators, and can probably do about ~350Adc at 48 Vdc at the elevation that these are sited.  The battery banks are 4 x 1000 Ahr GS Nanocarbon 48 battery strings and can gobble up the 350Adc easily when they are discharged.
>> 
>> While discussing the generator operation with the generator supplier, we have found this generator isn't capable of charge control, or limiting its own output.  The charge control functionality isn't necessary at this site because we really just need it to keep things online until the sun returns, a simple 54 VDC float voltage would work.  However, without the generator being able to self-limit its output, we expect this generator to stall when started because it can't regulate its output current and will immediately become overloaded by the discharged batteries.
>> 
>> I am trying to come up with some options to rectify this serious design issue.  One idea that immediately came to mind was putting in some parallel solar charge controllers between the DC generator output and the battery bank.  If the generator output could be dialed up to around 60-70 VDC, could parallel solar charge controllers be used for charge regulation?  It would be kind of like charging a 48 V battery bank from a 70 V battery bank.  MPPT isn't applicable, could the max current limit in the charge controller(s) be used to regulate charge rate?  Will the charge controllers blow up?  If not, what brand might work.  Each site has 8 x Midnite Classic 150s but I'm open to other manufacturers if it would work.  I am open to blowing up a charge controller in the shop but I thought it best to ask first.
>> 
>> What are other ways to put this generator to use, and limit its load?
>> 
>> 
>> 
>> Thanks for your input/comments
>> 
>> 
>> 
>> 
>> 
>> 
>> -- 
>> 
>> 
>> 
>> Mac Lewis
>> 
>> "Yo solo sé que no sé nada." -Sócrates
>> 
>> 
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