best way to auto-start your generator

JonF

Hello,

This is my first post, so let me say thank you in advance to the knowledgeable folks who create this great resource online. I have learned a lot from reading through the forum.

Question: One of my off grid systems has a 48 V 1040 AH Hawker deep cycle battery that is charged by a 15KW diesel gen set as the only charging source. The generator kicks on when the voltage on the battery bank reaches 48.0 and stops when the voltage reaches 58 V.

I am charging with an IBE battery charger rated at 120 Amps DC startup and 87Amps DC continuous.

The problem with this system, as I see it, is that when the battery bank is loaded the generator will kick on when the battery is at 80-90% SOC and when there are no loads the charger will kick on at a 30-40% SOC.

Worst, the battery will probably not get a full absorb or float charge because the set points do not consider amps.

I assume there is a better solution, but I can't find it. Any suggestions?

TheBackRoads

Re: best way to auto-start your generator

Are you running an inverter? What kind?

mike95490

Re: best way to auto-start your generator

How long has the setup been in operation ? (and what is the reason for asking now - is it failing ?)

Are there any other charging sources (wind, solar, hydrro?) or is it generator only ?


If generator only, you have to decide between burning a lot of fuel at very little load, to complete the absorb cycle, or shorter battery life.

Perhaps a weekly absorb cycle is the way to solve it.

JonF

Re: best way to auto-start your generator

Mike, very good questions. . .

The system has been in operation for approximately 10 years with no other charging sources.

I am in the process of planning a PV system and am trying to determine the condition of the battery and if I need to budget for its immediate replacement.

If I did incorporate a solar system, I think this charging scheme might be even more problematic.

I was hoping that there was a meter of some kind out there (I have a tri-metric 2020 installed) that would use an auto start module based cumulative negative AH out of the battery bank, say 35-50% DoD.

JonF

Re: best way to auto-start your generator

TBR,

I'm running a bank of Exceltech MX 1000 inverters configured for 220 V output. It uses the hot swap technology, so depending on how many loads I have (This is at a seasonal off-grid resort where occupancy varies by season) I will unplug some inverters to cut down on standby power consumption of the MX 1000s (20W per 1000W).

mike95490

Re: best way to auto-start your generator

JonF wrote: »

. . . . . The system has been in operation for approximately 10 years with no other charging sources.

Awesome ! Whats the warranty on those - 10 years ? You've gotten great service - I don't know that I'd suggest much different. The mix of deep and shallow cycles may be working in your favor.

I am in the process of planning a PV system and am trying to determine the condition of the battery and if I need to budget for its immediate replacement.
If I did incorporate a solar system, I think this charging scheme might be even more problematic.

Likely not, it would extend time between genset runs, and it would do some of the absorb time you are lacking. Panels, fuse, charge controller, you are all set.

I was hoping that there was a meter of some kind out there (I have a tri-metric 2020 installed) that would use an auto start module based cumulative negative AH out of the battery bank, say 35-50% DoD.

JonF

Re: best way to auto-start your generator

Likely not, it would extend time between genset runs, and it would do some of the absorb time you are lacking. Panels, fuse, charge controller, you are all set.

If it was only so simple. I'm in the bottom of a canyon and am investigating a remote array location using a high Voc and a Xantrex XW MPPT 80/600 CC. But maybe that question is for another thread.

BB.

Re: best way to auto-start your generator

I believe both the Xantrex and Victron line of Battery Monitors include programmable setpoints... For example, start genset at 50% of State of Charge, and shutdown at 80% state of charge.

-Bill

JonF

Re: best way to auto-start your generator

Thanks Bill,

Is that what you recommend for the set points(50%/80%) in a system with a generator only?

I assume that periodically you would want to adjust the relay set points so that you could get to 100% SoC. Do you have a recommendation on how often you would want to do that, weekly?

Also, when programming the Link meter, how do you determine the approximate point, in AH of a 25 or 50% DoD with an older battery? Is there a load testing procedure that you can point me to for bigger 48V battery banks?

I guess you are always going to be trading off between diesel consumption and perfect battery charging without a renewable source to absorb/float charge with.

mike95490

Re: best way to auto-start your generator

You need 2 gensets, and 2 chargers. 1 biggie to do the bulk, and one smaller to do the absorb. One can act as the "spare" because they do need maintenance once in a while.

Measure the charge current (not the loads) when the voltage peaks, just before the genset shuts off, that's 80% of what the small one needs to supply.

---

Or put tracker mirrors on the canyon rim, and beam the light to the solar panels !

BB.

Re: best way to auto-start your generator

Jon,

What is it you are looking for? A highly automated generator backed system with optimized charging/fuel usage?

Or just something that will do the job of keeping the batteries from accidentally being killed by others in the family/visitors/etc.

For example, you probably want to run the genset during the morning/daytime and have quiet time at night (so a timer in conjunction with state of charge). However, if the battery gets too low, you probably want the genset to light off right away--or at least set an alarm (light, buzzer, etc.) for people to make some decisions (turn off loads, look for something accidentally left on, or go ahead and run the genset for a couple hours, etc.).

Or even time it so that it runs from 7am-10am and 4pm-9pm to supply the major loads (cooking, washing, cleaning, shop work, pumping, lighting, entertainment, etc. -- And charge too). Let the batteries just handle the off-peak loads.

Have you monitored the loads on the genset (and fuel usage) so you get a profile of when the generator is heavily loaded and fuel efficient (40-50% minimum?) and when it is lightly loaded where loads would be best handled by the battery bank?

Is there some reason not to use solar panels to finish off the "lower rate" charging during the daytime (absorb)? If this is a 1-2 season operation, or shaded, then I can certainly understand that solar panels may not be helpful.

I can make suggestion some other suggestions--but there are others here with much more experience than I regarding battery care.

-Bill

techntrek

Re: best way to auto-start your generator

I like the idea of a smaller 2nd generator for a more efficient absorb cycle (and backup). Just be sure to get your big guy loaded around 80% (or above) for the best fuel economy. As an example, my 12 kw LPG genset uses 1.5 gallons per hour to produce its first 6000 watts. It only uses .5 gallon to produce its next 6000 watts.

Then I would get a Honda EU2000i inverter-genset (or 1000 or 3000 depending on what your max charge rate will be at the beginning of absorb), for the absorb cycle. It will throttle back as the charge rate drops, saving you more fuel.

JonF

Re: best way to auto-start your generator

What is it you are looking for? A highly automated generator backed system with optimized charging/fuel usage?

Or just something that will do the job of keeping the batteries from accidentally being killed by others in the family/visitors/etc.

Good question, I think that I have the latter already with the voltage trigger. I am really looking to figure out how to incorporate a solar array into my existing system, if the array is at all feasible.

The system has to be fully automatic, as I don't live on sight. I do make daily checks on the system, but I cannot depend on guests/family members to manually start a generator. If I have to give up some efficiency for this, then so be it.

It does, however, represent a problem for the possibility of absorption charging with a smaller generator, dual gen start relays would be at least 1K, not to mention a new generator and the headache of the system possibly shutting down when paying guests are around. For now I am going to continue to explore the feasibility of a remote solar array (post forthcoming).

I do track fuel consumption on a weekly, monthly and annual basis and I have a KWH meter on both my generator and after my inverter so that I can get a sense of the overall efficiency of the system. I do know that my IBE charger is something like 50-60% efficient, which is a real bummer.

I probably need to do an entire system audit to figure out where the inefficiencies are to determine a cost benefit of the various different upgrades that might be possible.

mike95490

Re: best way to auto-start your generator

JonF wrote: »

... I do know that my IBE charger is something like 50-60% efficient, which is a real bummer.....

I just tried a quick search, and it's real hard to find a high amp, 48V charger, with PF correction . Almost want to say "get a inverter that has a PF charger in it" !

Heck - even the XW with it's 100A charger, is small for your batteries.

Maybe golf cart or foklift chargers ?

BB.

Re: best way to auto-start your generator

You might, for example, setup the main genset to auto cycle from 50% to 85% or so... And put a timer on it (maybe only operate from 8am to 2pm as an example).

And once or twice a week, have the genset extend the charging cycle by 2-4 hours to take the battery over 90% state of charge (approaching 100%).

And, you should run a bulk/absorb cycle afer the last group leaves so you don't let the battery bank set at less than nearly full charge (I suggest less than 75%, others suggest that the batteries should be stored at nearly full charge to reduce sulfation).

And even with no loads, the bank should be recharged at least once a month (or reprogram the controller to charge 80% to 95% state of charge).

You have a very large battery bank and even a 5% rate of charge is not insignificant:

• 1,040 AH * 58 volts charging * 0.05 rate of charge = 3,016 watts

By the time you add efficiency and poor power factor for most battery chargers, you are looking at a minimum of 6,000 watts for active charging.

Perhaps, you could use a eu2000i once a week or four with a 1kW battery charger for "trickle charging" during the off season (if you have one).

Is that battery bank "too large" for your daily loads perhaps? A battery bank that size will handle a 10-20 kWH per day loads pretty easily (assuming recharging every 1-2 days). Is there electrical heating/cooking/air conditioning going on?

-Bill

JonF

Re: best way to auto-start your generator

it's a real bummer in that we have a big investment in inverters and they don't really make stand alone 3 stage battery chargers that can charge at the 100A rate, at least none that I know of. I'm pretty sure the IBE that I do have is from the forklift industry.

BB.

Re: best way to auto-start your generator

I forgot to add a thread that talks about Power Factor and smaller generators (per Mikes comment before my post):

Question about battery charger selection with EU2000 generator

Does a pretty good job of describing the issues and why getting good PF corrected chargers/devices can be worth the effort.

-Bill

JonF

Re: best way to auto-start your generator

bingo Mike, found this online:

48 V 3 phase battery chargers:

http://www.forklift-battery-charger.com/pulsetech/48-volt-powerpulse.php

48 V battery-desulfators:

http://www.forklift-battery-charger.com/pulsetech/48-volt-powerpulse.php

mike95490

Re: best way to auto-start your generator

JonF wrote: »

bingo Mike, found this online:

48 V 3 phase battery chargers:

http://www.forklift-battery-charger.com/pulsetech/48-volt-powerpulse.php

48 V battery-desulfators:

http://www.forklift-battery-charger.com/pulsetech/48-volt-powerpulse.php

Now you just need a 3 phase genset ! Generally, they are pretty quiet !!

But none of those list Power Factor. Using a transformer, and likely a bridge rectifier, they will not be too good, and require a larger genset than would be apparent

I'd look at this single phase model -
http://www.forklift-battery-charger.com/single-phase/48-volt-120-amp.php at only $1,425

AC Input: 208V/240V/480V
AC Current Draw: 41.9A/36.3A/18.1A
Does your genset have a 480 V output ??

TheBackRoads

Re: best way to auto-start your generator

Don't forget guys that the OP has a 15KW diesel gen set....... That can run quite a charger...