Generator/Charger set-up

hemmjo · February 2015

I have to add backup charging capability to our existing off grid set up and provide for it in the new installation I am planning in another building. The existing system is the staff house shown below. The new installation will be similar, perhaps with 6 batteries instead of 4. Perhaps with generator back up we can stay with 4 batteries? We have a Honda eu2000i generator.

The generator specifications say "120V 2000W max. (16.7A) 1600W rated (13.3A)" (from http://powerequipment.honda.com/generators/models/eu2000i-companion) I would like to get an Iota DLS-55 its maximum current draw is 13.4. The DLS-45 has a max draw 11 amps.

So I have a couple of questions.

1. Do you think the Honda will run the DLS-55 or should I stay back away from the upper limit on the generator and go with the DLS-45?

2. Where in the system should I connect the charger? I have a shunt and current sensor (WhizBang Jr.) installed. Should the charger be wired to pass through this shunt? Or, is best to wire it direct to the battery bank?

3. I have two systems what will need access to the back-up generator but only one generator. Since we have only one generator, I am thinking I will get only one charger, and it will have to be moved between buildings. I have installed a few of these plugs on service trucks to handle jumper cables and other high current applications. (http://www.newark.com/anderson-power-products/6800g2/plug-socket-connector-plug-2pos/dp/88C9450)

Any thoughts on is tentative plan?

Thanks,

John

Blackcherry04 · February 2015

Re: Generator/Charger set-up

The Honda EU 2000 will power the IOTA dls-55 without issue. The question is are you better with higher charging amps and more load on the generator and more fuel or a smaller charger and longer run time and less fuel. Lately I have changed my scheme to the smaller charger and more run time and less fuel on the ECO throttle. The dls-55 will run on the ECO throttle, but it does use more fuel. I have another scheme where I use 2 dls-30's, one powered all the time and the other on a relay that a load will pull in and out.

I run mine through the shunt.

Well, if your going to move the charger then the anderson connectors make sense, you need it as " Murphy Proof " as possible or you'll have blown fuse's on the charger.

hemmjo · February 2015

Re: Generator/Charger set-up

I do wonder about high amps vs low amps and fuel use also. If the Honda will handle it, I am going to go with DLS-55, since I need to get one system charged and move the rig to the other system to keep it charged. And we wont want the gen running at night.

Thanks,

John

BB. · February 2015

Re: Generator/Charger set-up

Personally--I would suggest two chargers--High current DC connections are not something that you really want to make/break a couple times a day. Add that you want to be very careful with somebody swinging a wrench on/near a battery bus too.

If you are still looking to do the DC plug, then I would look at Anderson Connectors:

http://www.solar-electric.com/installation-parts-and-equipment/wiring-cables-and-connectors/anhicupoco.html

About $7 per 50 amp plug end (one for charger, one for each battery bank). Actually surprisingly reasonable price (looked at any higher current AC connectors lately?

).

Is it worth putting the generator at a fixed location and run AC power to the two buildings/chargers? I would assume that security and avoiding complications would be nice (having somebody responsible for moving genset around/fueling/etc. is a pain on its own).

-Bill

westbranch · February 2015

Re: Generator/Charger set-up

John, how far away are the 2 buildings?

I agree with BB about running 120V vs moving the genset about, and having 2 chargers.

You mention going to 6 batteries. 3 series of (2 x6V) batteries is not a good setup for keeping the different strings balanced all the time, and considering there is no 'expert' on site even a worse situation..

Maybe this is the time to reconsider a 24 Volt system, 2 x (4 x 6V) and hooking the 2 building systems together somehow...

Thoughts?
hth

hemmjo · February 2015

Re: Generator/Charger set-up

Thanks for the input. I realize that all good design solutions are a compromise I am trying to work through them. I do appreciate your input, I have no one else to critique my crazy ideas.

The buildings are 250 feet apart. We discussed this in another thread a while ago when I was trying to decide whether to simply upgrade/enlarge the existing system and run conduit under ground to the other two buildings, or simply build a whole new system. The complete new system won out it was just about the same cost wise. Having the redundancy of two separate systems turned the scale that way. In addition, with 2 systems, if one "group" of users wastes power, it will not deplete the resources of those who save it! I like having the inverter BEEP at them with they exceed their load limit!!!!

We are staying with the 12 volt inverter because we had two donated a while ago. Buying another would eliminate all possibility of other more important additions in this budget. The KISAE 1000W-PS inverter we have has been working fine for almost a year. If we ever do need a new one, we will switch to 24v.... That brings up another question!!! I have been convinced to bring the power in from the panels at 36v instead of 72v. If I switch later to a 24v system, will the 36v (actually 31Vmpp) from the panels be enough to charge the 24v system? Or should I go with the 72 now, knowing that someday this will switch to a 24v system. I do think I am going just go with 4 batteries instead of 6. This will help with defray the added expense of the additional for the MNBCM displays and allow me to get two chargers instead of moving one back and forth.

Now the question becomes... If I get two chargers and build a little "generator house" between the two buildings, it would only 125 feet to each building. If I do this, my new dilemma is what two chargers do I get? If I get two DLS-55's, 13.4 amps each, there is no way the little Honda would run both at the same time. I would have to drop down to DLS-30's, 7.3 amps each to be able to run them at the same time. Would it be better for the batteries to charge one set at a time with the larger DLS-55, or charge both sets a the same time, at a lower rate using DLS-30's.

Thinking out loud, one problem with putting the generator between the buildings is, it is a relatively flat open space they use for soccer, baseball, kickball, etc. For now the generator is going to have to move between locations.

This is just part of what is rattling around in my head.

Thanks,

John

BB. · February 2015

Re: Generator/Charger set-up

Your choice where to put the building... Remember the total wire run will be the same if the building it to the left, middle, or right of the run (i.e., short run to building A, long run to building

.

Two larger chargers with an A or B switch vs two smaller chargers with an A+B switch/connection. That is really your choice. If both will need roughly equvalent charging at the same time, then it probably does not matter much.

If one building uses more power than the other--Than two big chargers and an A or B switch Fast charging for the bank that needs the charging.

You would probably want a 10% minimum rate of charge (i.e., 50% to 80% rate of charge will take ~3 hours). If you go with 5% rate of charge, even that smaller range of charging will take you ~6 hours to accomplish. Similar amount of fuel, but longer time to "baby sit" the charging.

-Bill

westbranch · February 2015

Re: Generator/Charger set-up

Since you are seriously considering changing up to 24V in the future, you can still go with the 72Volt for now knowing you re losing a bit of power to heat generation in the interim. It is not a game changer just a choice. I would do it that way so you do not have to change anything later on other than update the Classic and reconfigure your batteries. Your wiring may be a bit larger going into the CC but will no need to be changed later...

About the charger, what is the current use pattern, ie how far down do the batteries get to by the time the Gen is started?

hemmjo · February 2015

Re: Generator/Charger set-up

westbranch wrote: »

About the charger, what is the current use pattern, ie how far down do the batteries get to by the time the Gen is started?

During the sunny season April-December, the SOC is typically 68-70% each morning before the sun comes back up. Unless it is really overcast, we can get enough power even with some clouds to get the batteries up to 80-90 SOC and cut back electric use until the next day. We seldom have 2 days in a row with no sun.

Actually yesterday is the first time since the installation last March that they have asked about the generator. Right now the only option is to use a little 10 amp automotive charger we have there. I was told it raised the SOC 10% but I am not sure how low it got. This is the first rainy season we have had the system installed. We definitely need generator back up during these months.

I am leaning toward the larger chargers. Thinking this further out, we really need a second generator rather than relying on just one for ALL functions. We are building our medical program up and will need RELIABLE refrigeration. Right now it is a "nice to have" feature. When we get one full of medical supplies, it will be a MUST have feature so the redundancy of a second generator will be necessary.

mike95490 · February 2015

Re: Generator/Charger set-up

I would say, 2 chargers & 2 generators. Eventually, one generator will not start when it's supposed to.

BB. · February 2015

Re: Generator/Charger set-up

Build one shed for the gensets--A second for the fuel? Avoid fire taking out the entire installation.

-Bill

Generator/Charger set-up

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