high rate charging on generator

[pianotuna]

Hi all,

The batteries:

556 amp-hours of surplus acid AGM batteries 12 volt jars 105 lbs each. They are wired as two banks with balanced wiring.

The depth of discharge:

12.1 volts under 425 watts of load plus normal RV overhead applied for 4 hours. During the day the fridge (325 watts) was run for 5 hours and the RV was driven at highway speeds for 3 hours. On the last hour of driving charging was initially 50 amps but that soon tapered to 25 amps. The solar contribution was about 5 amps.

The generator:

Yamaha Sieb 2800 Va (23 amps of output @120 volts AC)

The inverter/charger:

Magnum 3000 hybrid.

What happened:

I deliberately took the battery bank down farther than I normally would. I turned on the generator after setting the Magnum to draw no more than 23 amps.

Within one minute the Magnum remote reported "fet over load". Remote was showing 127 amps of charging at 12.9 volts DC just before the over load shut down.

I reset the Magnum by removing all power sources. I "dialed down" the possible input to 15 amps from 23. This still caused the Magnum to display 125 amps of charging. I finally dialed it down to just 13 amps to prevent over load on the fets. At that level charging was 90 amps @ 12.5 volts.

I've been charging for 45 minutes at 90 (+) amps and the voltage had risen to 13.8.

I 'opened up' the input to 23 amps and after 15 minutes it is now charging at 14.3 @ 98 amps. The remote is saying absorb charging.

15 minutes later and the remote says 14.3 at 80 amps.

1.5 hours and charging is 14.4 @ 27 amps.

During this time frame I did also run the microwave and three oil filled heaters (400 watts each).

The generator was running with the eco switch on and at the 45 minute point started throttling back as the load shifted.

Next time my voltage is so low I'll dial the Magnum down to 13 amps to start out.

[MEXICOWANDERER]

Niner
The head of the nail took a solid hard whack thanks to your post. You understand what you have and that amigo makes for a battery/consumer marriage made in heaven. Off grid homeowners can cluster as many telecomm batteries as they wish since weight and space is not a concern to them.

Telecomm batteries are superb specific purpose batteries.

[NinerBikes]

MEXICOWANDERER wrote:
Thicker acid mats reduce plate area. If you understand the strength and weakness of a telecomm battery they will suit the purpose perfectly. But cycle lifetime ratings for telecomm are wholly different than cycle rating for off grid. Cycle ratings for telecomm are ONE HUNDRED PERCENT DISCHARGED - ZERO PERCENT REMAINING. There is a huge difference in how batteries are rated.

Theoretical average sampling (assumed)

Guaranteed

You guys are comparing apples to oranges. Ratings and performance wise. Like golf car and scrubber batteries telecomm batteries are more competitively priced than other AGMs and for exactly the same reason. But they have DEFINITE PURPOSE strengths and weaknesses.

I would not go Honking on Bobo the telecom battery, with the big inverter, making coffee, running the hair dryer or electric heater. But running parasitic load, LED lights, a small TV, anything that is not demanding instantaneous heavy demand draw, is probably just fine. My belief is you'll have to practice some electron conservation, or start stacking more batteries so you do have enough battery to cover heavy amp high usage draws.

The batteries are big, heavy, and like lumbering low and slow charging, as well as low and slow discharging, with steady current draw. Your usage in an RV should try to match those parameters, if you'd like these types of batteries to work for you.

I have a generator I can run if I want electric brewed coffee, while recharging the battery too with the generator. But I camp solo, no wife, no hair dryer, no instant gratification needs required at the touch of a switch or a finger. I do tend to still rough it a bit, after all, it is camping for me, not a Motor Home... big difference there.

[MEXICOWANDERER]

Thicker acid mats reduce plate area. If you understand the strength and weakness of a telecomm battery they will suit the purpose perfectly. But cycle lifetime ratings for telecomm are wholly different than cycle rating for off grid. Cycle ratings for telecomm are ONE HUNDRED PERCENT DISCHARGED - ZERO PERCENT REMAINING. There is a huge difference in how batteries are rated.

Theoretical average sampling (assumed)

Guaranteed

You guys are comparing apples to oranges. Ratings and performance wise. Like golf car and scrubber batteries telecomm batteries are more competitively priced than other AGMs and for exactly the same reason. But they have DEFINITE PURPOSE strengths and weaknesses.

[NinerBikes]

It's football season, I may spend more time out at the TT watching football on the TV, drinking a beer, and in general cycling the battery and generator regularly to keep the gas in the Honda generator fresh, and the jets in the carburetor clean. As well as cycling the Telecom battery. I don't believe I have gotten much below a 60 to 65% SOC yet.

I don't know how deeply discharged mine was when it only took 21 amps. What I do know it that with the Mega Watt 30 amp, and this battery rated 158AH @ 20 hrs amp rating, I am right at the C/5 max rate. I put a good 14 days in a row on mine the first two weeks of Sept. It's held it's voltage at 12.88V and a month of sitting in my garage in some heat had it down to 12.84 when I just float charged it again and topped it off. I will probably check it again come December 1st, for holding voltage, and top up as necessary.

I would think that a sunny day, and with one 158 amp hr battery, my 150w solar panel aimed at the sun on a sunny day for 3 to 4 hours will more than suffice to top charge the telecom battery before letting it rest again in storage.

What I am seeing, time and again, is that it takes about 3 to 3.5 hours for the battery to get the last 4 or 5% charge while recharging, back into it... There is no forcing it, no rushing it... doing so with a generator is a huge waste of fuel. And it is imperative to get that last 5% back in, to prevent sulfation, as soon as is possible, if you want the battery to last. These batteries don't sit well if not stored completely, fully charged, that is considered abuse. The cell site keeps them top charged constantly, if power goes out, as soon as power comes back on, these batteries are being recharged fully to 100% SOC. You need to mimic and duplicate that condition, as best you can, while dry camping.

[JiminDenver]

So will the telecom batteries be recommendable in the future?

The set I had a line on were $500 for 600 Ah new. A pretty good $-Ah ratio I believe.

Altho AGM, they can't slurp up the juice like other AGM jars. Then again you are not paying the premium price either. ( 1/3 the cost of Lifelines)

They can't take the daily cycling like 6 volt jars.

It would seem best to over size the bank to keep the cycles shallow for longer life. That kinda kills the $-Ah ratio and you have to have the room and weight capacity.

I think they are in their own category and will fill certain needs and have their own requirements for care. They are maintenance free, can be mounted on their sides. Their size and weight have to be considered. All that remains is to see their longevity when used by various members with their personal touches.

Isn't it great when they give us new toy to play with.

[pianotuna]

Hi Niner,

I'll use them right into the ground as I did with the flooded batteries I replaced.

I do understand that recharging via a generator is a totally different kettle of fish that using shore power.

My brief excursion into the region of 50% state of charge was 3 hours of generator run time to return to 8 to 12 amps of float. Out of pocket for fuel was a whopping $12.00 Cdn. I only run premium in the generator and it was $1.149 per liter.

Turning down the maximum charge rate from 125 to 108 is going to make a difference of about 14% in generator run time, worst case. But I think, given my charging style, it will not cost me any more to limit the rate.

Again, because I'm by nature a shallow cycler, up until my deliberate deeper discharge the greatest charging rate I've seen was about 70 amps. 30 minutes of generator time gets me back to a 14 amp recharge rate. That is approximately 97.5% of fully recharged.

I'm fortunate to have remote control of the Yamaha generator, and so I can start it and stop it at will. It takes about 30 minutes for the oil filled heaters to start to cycle. When they do, I shut down the generator and let the space heating "coast". During the coasting I am generally running a laptop and a 50 watt heating pad, which I operate on a 300 watt MSW inverter. At 4 C (30 f) I stay comfortable with the bedroom about 18 C (64 F) .

At -4 C (24 F) I need about 800 watts to keep the bedroom at that temperature. If I wanted to stay at or above 60% state of charge I could do the 800 watts for approximately 3 hours.

The lowest voltage I've seen in the morning is 12.4 volts with about 2 hours of generator run time overnight. This was at the 4 c ambient temperature.

Now that winter is upon us I need shore power to keep warm and shortly will need either 3 fifteen amp circuits--or go to the only campground that is still open, where I have access to 50 amp power.

I'll be going the campground route probably on November 1st.

[NinerBikes]

Solar panel time, and sunny days, Don. Smaller generator and smaller amp hours for telecoms, if you're going to stick with them.

[MEXICOWANDERER]

Telecomm companies establish parameters for maintenance based on OEM guidelines. OEM is aware that their client wishes the very highest degree of performance reliability. So a operating lifetime max hours is agreed upon. Max hours of guaranteed reliability. Zero non performers. The batteries have a specified level of max discharge at which Telecomm shuts down transmission and the batteries go dormant. The percentage of charge remaining is unknown to me.

Technicians operate by holy writ in the form of rote. They follow maintenance, troubleshooting and testing exactly and precisely according to company doctrine. It is all well documented then entered into a computer database for reference, study and analysis. Job one is the repeater must not fail.

Transcribing telecomm writ to a usable form for RVers can be deceptive. What worked excellently for telecomm may not be in the best interest of somone whose use of the used batteries may be totally different. Telecomm is after 100.0% reliabilty at the expense of trade-offs. Are you aware of the tradeoffs?

Understand this point. After an outage, telecomm batteries have forever and a day to recharge. Do you? Charge amperage ceilings are based on acheiving ultra maximum longevity. This is a moot point if telecomm batteries spend a majority of their golden years connected to shore power with incidental short interruptions for boondocking. In that scenario following Telecomm rote is the wisest choice as it most closely mimics what the batteries were designed for.

When things shift to off-grid rote gets chucked out the window. Calculated charge maximum absorbsion voltage is not the same animal. Neither is maximum absorbsion voltage. Only float voltage remains thec same.

If you stick like glue to telecomm rote prepare to rum your generator a lot longer. You are mimicking unlimited time value recharging via your generator. Your fuel and your time.

When I generator recharge 3300 amp hours of 24 volt battery it is absolutely different from charging using CFE shore power. One is 500+ amperes. The other is 120 amperes (the 4024 Trace). Coursing 120'amperes through a 1650 amp hour battery / 2 banks is a gentle recharge. Life with public power available is absolutely unlike recharging via a generator. The issue is time. The issue is money. Lots and lots of money. To do an in-frame on the Kubota is around five thousand dollars. Add that to $3.35 fuel, filyets, lube oil and labor and it makes shore power recharging calculations totally, completely and absolutely irrelevant. To the point of becoming absurd. Cost of kWh hr transcribed to usable battery kWh includes the ACTUAL cost of fuel plus generator wear and tear. I an not a telecomm company and nothing I manage even remotely can serve as a model for both economics nor management.

[MrWizard]

mine turned 4yr of use in July
i'm way over that 300 cycles

with about 1500 total cycles, i'm real sure i hit that 300 to 60% quite some time ago

i know they are Not "like new" any more

they have sure earned their cost

they will be replaced when i find suitable "Obtainable" replacements with in reasonable driving distance for pickup

[pianotuna]

Hi Phil,

"They will be fine as long as it's at proper voltage. Unlike flooded cells they don't need to high current to stir the juice and keep the plates from sulfating"

pnichols wrote:
Don .... did he advise you of what the minimum charging rate was for AGM batteries .... for us low and slow guys?

[landyacht318]

pianotuna wrote:
300 cycles to 60% is what is expected for the lifespan.

I almost want to ask if there is a Missing 0 after the other two but 3000 is less believable than 300.

Interested to see how long these telleycom AGMS last in RV usage with proper recharging.

[pianotuna]

Hi Phil,

No, but I'm still in contact with him so I will ask.

[pnichols]

pianotuna wrote:
He advised me that c/5 is the maximum charging rate for our surplus acid AGM batteries. I think that is quite useful information to have.

Don .... did he advise you of what the minimum charging rate was for AGM batteries .... for us low and slow guys?

[MEXICOWANDERER]

Good info Don. Kudos

[pianotuna]

Hi Mr Wizard,

I bumped into a telecom engineer on facebook who manages several hundred battery banks.

He advised me that c/5 is the maximum charging rate for our surplus acid AGM batteries. I think that is quite useful information to have.

In my case that means:

139.2 x 4 = 556.8

556.8 / 5 =~ 111.38 amps

I've redone the setup on the Magnum to limit it to 90% of 125 amps, which is 112.5 amps. I also set up the input charging limit to 13 amps down from 15. That should limit charging to 108 amps. (I prefer to wear a belt and suspenders *grin*)

Fortunately, thanks to the fet overload I had throttled back on the charging rate so I did not damage the batteries.

The same gentleman has just told me that 300 cycles to 60% is what is expected for the lifespan.