Mercedes OM616.918 - A Few Questions

[Lloyd]

RCA,

Since the Balmar controller isn't software controlled, but by discrete components , you would need to arrange  discrete components to achieve a 1:1 "edit" I meant a 2:1voltage splitter ie: the bank says 48 volts the splitter says 24 volts back to the sense voltage back to the controller.

Depending on how the bank is set up, each isolated alt charges a 24 volt section of the 48 volt bank. Then bc all discharges ar 48 volt, and the Balmar controls both alternators from a singe sense from the 24 volt section of the 48 volt bank, then all cells in the bank should receive an equal charge.

With isolated alternators it is possible to hook them up in series, but you would need to make sure the bridge rectifier can handle the double voltage. it may require an external bridge built to the needs.

It might also be possible to use the new IGBT bat isolators  wired in series from the alts to achieve 48 volt out from 2 alts, you would need to build the discrete splitter to control.

Lloyd

[WStayton]

I am confused here!

rcavictim;

  You said:

"BTW, you have evaluated the capacity of your proposed battery bank incorrectly.  You said, " With the S-600 batteries, i have 16 * 450 = 7,200 amp hours. "  IF you were making a 6 volt system then yes you would have 7200 Ah.  Your system as I understand it will be 48 volts. That means you have two sets of eight batteries in parallel.  That is 900 amp hours at 48 volts. Assuming 80% charging efficiency it will take 1250 Ah to charge them.  A 15 kW generator can charge those fully in 4 hours."

I don't see what differance it makes wether I have them in 16 individual batteries operating solo, or two strings operating at 48 volts or one string operating at 96 volts.

In any case I've got, for each battery:

   Voltage= 6 volts
   Capacity= 450 amp hours
   Depth of Discharge = 50%
   Which equals 6 volts * 450 amps * 50 % = 1,350 watts per battery
   If I am using 16 batteries, to 50% depth of discharge, no matter of how I string the together = 16 * 1,350 = 21,600 watts
   If 746 watts = 1 HP-hr, I have 21,600/746 = 28.95 . . . HP-HR
   I rounded this up to 30 HP-Hr to account for battery charger/inverter losses.
   Since I will also be runninng 120 Volt loads while I am running the Battery chargers, I SWAG'ed those as about 10 HP., counting pump starting loads, etc.
  If I am going to recharge 30 HP-Hr/s worth of energy over six hours and knowing that the battery chargers have to taper off to not damage the batteries and use lots of water, I ASSUMED (and we all know what that means!  <grin>) that I could start charging at the 10 HP rate and tape off over six hours and get 30 HP-Hrs total.
  In making the forgoing calculations, I payed no attention to how much charge the inverter charger's were capable of because I had not gotten that far yet because I started out figuring on, 16 T-105 batteries in two strings of eight and discovered that this didn't satisfy the energy demand that I though I had so I then went to 32 T-105 batteries in series/parallell for two circuits of 48 volts each, but discarded this becvuase I though that having two strings of eight batteries each in parallel was asking for problems of having one string of eight batteries take more charge that the other and thus cause problems so I switched to specificatioin to the S-600 batteries which are roughly twice the capacity of the T-105s though the are much more than twise the cost . 

  I suppose a more cost effective solutions is to start over with some flavor of two each plain 3,000 to 4,000 watt 48 V DC inverter, capable of being stacked to 240V AC, without a charger, running on two strings of eight T-105's each for a total of 32 T-105's, and then some additional form of charger for each string of eight T105 batteries.

  I hadn't gotten as far as realizing the limitations of the charger function of that particular charger/inverter but that is really why I tossed it out here, before I actually "wrote the check" to see what I had forgotten.  Obviously what I had forgotten exceeds what i remembered, but isn't that why you  guy are here, to keep me from doing something stupid that will only succeed in spending money to no good purpose?  <grin>

  Rethink is obviously warranted!

  Now, where can I find info on the differance's in waveform of ST vs STC generator-heads without doing a web search and wading through 43,561 websites that really don't address the questions at hand?

[rcavictim]

RCA,

Since the Balmar controller isn't software controlled, but by discrete components , you would need to arrange  discrete components to achieve a 1:1 "edit" I meant a 2:1voltage splitter ie: the bank says 48 volts the splitter says 24 volts back to the sense voltage back to the controller.

Depending on how the bank is set up, each isolated alt charges a 24 volt section of the 48 volt bank. Then bc all discharges ar 48 volt, and the Balmar controls both alternators from a singe sense from the 24 volt section of the 48 volt bank, then all cells in the bank should receive an equal charge.

With isolated alternators it is possible to hook them up in series, but you would need to make sure the bridge rectifier can handle the double voltage. it may require an external bridge built to the needs.

It might also be possible to use the new IGBT bat isolators  wired in series from the alts to achieve 48 volt out from 2 alts, you would need to build the discrete splitter to control.

Lloyd

I am actually looking to control a 110 VDC generator rated at 2 kW which I can control the field on and use it to charge a 48 volt battery bank.  I have no plans right now of hooking up two 24 volt big-rig truck alternators.  I am also looking to control the SCR's in a big 3-phase welder to run as a battery charger so it will do bulk, soak, finish, float and equalize, or generally that sort of thing.  I have a large metal box right now that will do wash, rinse and spin, but that has to stay in the laundry room.

[Lloyd]

RCA...

This link might help you. http://www.simulation-research.com/help/



Lloyd

RCA,

Since the Balmar controller isn't software controlled, but by discrete components , you would need to arrange  discrete components to achieve a 1:1 "edit" I meant a 2:1voltage splitter ie: the bank says 48 volts the splitter says 24 volts back to the sense voltage back to the controller.

Depending on how the bank is set up, each isolated alt charges a 24 volt section of the 48 volt bank. Then bc all discharges ar 48 volt, and the Balmar controls both alternators from a singe sense from the 24 volt section of the 48 volt bank, then all cells in the bank should receive an equal charge.

With isolated alternators it is possible to hook them up in series, but you would need to make sure the bridge rectifier can handle the double voltage. it may require an external bridge built to the needs.

It might also be possible to use the new IGBT bat isolators  wired in series from the alts to achieve 48 volt out from 2 alts, you would need to build the discrete splitter to control.

Lloyd

I am actually looking to control a 110 VDC generator rated at 2 kW which I can control the field on and use it to charge a 48 volt battery bank.  I have no plans right now of hooking up two 24 volt big-rig truck alternators.  I am also looking to control the SCR's in a big 3-phase welder to run as a battery charger so it will do bulk, soak, finish, float and equalize, or generally that sort of thing.  I have a large metal box right now that will do wash, rinse and spin, but that has to stay in the laundry room.

[rcavictim]

Thanx for that link Lloyd!

[mbryner]

Thank you guys for those amp-hour calcs back there.   About 2 weeks ago I set up my Outback Flexnet DC battery monitoring system.    I took L-16 Deka batts @ ~360 AH x 16 batts = = 5760 amp-hours.   But you're saying since those batts are 6 Volt and my system is 48 volt, I should have used ~720 amp-hours as the correct number.  (Batt bank is 5760 x 6 = 34560 watt-hours, 34560/48 = 720)

Yes, I agree those Outback VFX inverters are not the best for interfacing w/ gen power.   I have 2 VFX3648 inverters also and they just kept charging from the generator instead of backing off and letting more power get to where you're using it.   That's why I built the ST head AC  rectifier to  DC input into the solar charge controller, which works great and still allows 120/240 emergency gen power at the flip of a few switches.    A 3 phase gen head would work great for that because the ripple would be less, and you'd have 3 phase backup.     

2 x 24 volt alternators in series w/ more electronic components to control it sounds complicated to me.

It sure sounds like you're building an off-grid system instead of grid-tied.

Marcus

[Tom Reed]

Marcus, the Outback inverters will back off the charging amps, mine do. I've got mine set to pull 13 amps max from the generator. If you haven't programmed your max charge amps they might be doing what you describe. The problem with them is that when the load exceeds 13 amps it all goes to the generator. My old sw2512 Trace inverter/charger would switch from charge to inverter synced to and combined with the generator power for loads beyond what the charger was set to. This is what's called generator support by Outback. Outbacks export inverters do have generator support, but the domestic ones do not and likely will not ever unless they change their design. This is per my communications with engineering at Outback.

[Lloyd]

RCA,

I hope it helps. Also look at this MINT Charger and their patent http://www.minit-charger.com/other/marine/products/marine-200sp/system_specifications.php The MARINE-200SP utilizes the patented Minit-Charger™ algorithm that performs precise charge control to maximize battery life and minimize charge times. Because the charge rate never exceeds the charge acceptance curve of the battery, temperature rise is minimal during charge allowing multiple charge cycles per day.

Thanx for that link Lloyd!