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Thread: Voltage range for adjustable voltage regulator

  1. #1

    Default Voltage range for adjustable voltage regulator

    I have been working with one of the major LiFePO4 battery manufactures to design packages to convert the 45 year old GMC motorhome house battery banks to modern lithium batteries including replacing the devices required to properly recharge both the lithium house and lead acid starting batteries from all four common charging sources - alternator, shore power, generator power and solar (if so equipped). These old motorhomes use the very first GM designed alternator which was designed to do only one job, charging the lead acid starting battery. It was never designed to provide the high continuous amp draw lithium batteries can demand. Fortunately, there are now devices called Battery Isolation Managers that alter the duty cycle of the alternator while recharging house batteries without disrupting the recharging of the starting battery. They turn on charge current for the house batteries for 15 minutes and then turn it off for 20 minutes to allow the alternator to cool down. That looks like it will keep these old alternators alive while recharging the lithium batteries. For charging from the converter/charger while plugged into shore power or running the generator, most GMC owners long ago threw out the original "buzz box" and put in three stage chargers. Many of those like the ones from Iota and Progressive Dynamics can be reprogrammed to provide a proper lithium charging profile by just replacing an inexpensive module costing between $10 and $30. For those who can afford the cost and can find the room, I am recommending replacing those with a modern inverter/charger like the Victron units that would also provide seamless integration with MPPT solar chargers if and when solar is added to the mix. So, I think I have what I need for the GMC motorhome application.

    My question here is does anyone know the adjustment range for the Delco-Remy 1118448 (or 3, I can't tell which) voltage regulator for the 300 amp oil cooled alternator that recharges the house battery bank on a 1997 Country Coach. All I can find so far is that voltage can be adjusted via turning a screw on the front of that voltage regulator, but nothing about how high a voltage it can be set for. If I change to LiFePO4 batteries in this coach I need 14.2 to 14.6 vdc to fully charge those batteries. Ideally, they would like a float voltage of 13.6vdc, but can stand charging at 14.2 to 14.6 for a day at a time without damage. While plugged into shore power or running the generator, I know I can set the charge parameters to the correct profile on the two Magnum 2800 inverter/chargers. But, I need to know if I need to change the voltage regulator or simply turn the center screw to adjust it. I also would like to know the duty cycle for this alternator. Can it be run at high amp output for an extended period of time or do I need to use one of the Battery Isolation Managers here as well? Recommendations and comments welcome. Thanks.

    Jerry
    Last edited by Dtjoint; 09-13-2019 at 01:40 PM.
    Jerry Work
    Kerby, Oregon
    1997 Prevost Country Coach
    40 foot, no slides, Santa Fe
    decorating style

  2. #2
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    The 50DN was designed for extended high amperage output. But why are the batteries going to asking for so much current?

    Yes, setting the adjustment on the regulator will impact the voltage and nothing else.

    Although some don't like smart regulators, Country Coach and the marine industry has been using them for years. They have a model specifically for lithiums.

    http://www.balmar.net/multi-stage-regulators/

    You will have to ditch your battery equalizer and go to DC to DC converters. I can't see and effective way to support battery management with an equalizer. I also recommend the smaller batteries which may seem counterintuitive. It's so a bad battery doesn't have a significant impact on the bank.


    Gil and Durlene
    2003 H-3 Hoffman Conversion

  3. #3

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    Thanks for the info, Gil. I am talking about the 12vdc nominal house battery bank. I thought the battery equalizer is only on the starting battery bank where it is necessary to tap both 12vdc for the DDEC and lights and 24vdc for starting, etc.. When you say "ditch the battery equalizer" are you referring to something different that is in the house battery charging circuit? The new LiFePO4 house battery bank would be made up of 100 amp hour batteries so you add or subtract those to get the amp hours you want. 85% of the capacity of the Li battery operates at a higher voltage than a lead acid battery at full charge even in high draw applications. That higher voltage plus the ability to access nearly all of the amp capacity of the Li battery will provide more watts than a lead acid battery bank of more than twice the same rated capacity so 6 of these 100 amp hour LiFePO4 units should be enough for most of us who now have 6 8D house lead acid batteries. Since most of us have changed lighting to LEDs, 5 of them may be enough for many. To fully recharge them requires 14.2 to 14.6 volts. Ideally they should be charged at a 50 amp per hour rate or less each. That seems to me to put the recharging of this house battery bank right in the range of the 50N 12vdc (nominal) alternator if the regulator can be adjusted to the 14.2 to 14.6 range. Hence my question. The 24vdc (nominal) chassis battery bank would not be touched or impacted since it has its own alternator the way CC did it. Those two battery banks never come together. My thinking, anyway. Can you clarify your comment about the battery equalizer? Thanks.

    Jerry
    Last edited by Dtjoint; 09-14-2019 at 11:24 AM.
    Jerry Work
    Kerby, Oregon
    1997 Prevost Country Coach
    40 foot, no slides, Santa Fe
    decorating style

  4. #4
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    I forget you have a 12V house bank. So, disregard the equalizer statement. I trust you are only considering batteries with built-in battery management capability. You definately want a bad battery to take itself out of the bank.

    The smart regulator will vary voltage and current by charge state, just like your smart charger.


    Gil and Durlene
    2003 H-3 Hoffman Conversion

  5. #5

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    I have been working with the engineers at Battle Born Batteries in Reno, NV, on the GMC motorhome project so know to only use Li batteries from a reputable company with built in battery management. The only remaining issue for replacing the lead acid house battery bank in our 97 CC is how to be sure the alternator will turn itself off before the BMSs on each battery turns off incoming charge. I don't want that alternator to still be running with no where to put the charge current. In the GMC motorhome case it would still have the lead acid starting battery to absorb that charge current, but in the CC case the alternator would only be charging the Li batteries. The Balmar MC-614 appears to likely do that but it is not clear whether it would do so at a point below where the BMS would do that which is the goal. A trigger to shut off the continuous duty solenoid that controls field current to the alternator would do it but not sure where to get that trigger from the smart regulator. Time for a discussion with the Balmar engineers, I guess. Thanks for the comments here.

    Jerry
    Last edited by Dtjoint; 09-15-2019 at 10:47 AM.
    Jerry Work
    Kerby, Oregon
    1997 Prevost Country Coach
    40 foot, no slides, Santa Fe
    decorating style

  6. #6
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    Disclaimer: I am redesigning my ‘03 Royale system at this time. My comments are only based on my experience with diode damage due to sudden load disconnects and my research in replacing my lead acid system with lithium based batteries.

    While the Belmar unit may have the correct charge voltage control profile for a Li bank, you are correct in assuming that you need to interrupt the 50N field in the event that the BMS for the Li system “dumps” the battery load. This action needs to be near instantaneous since the output voltage of the 50N will runaway quickly due to back EMF and damage the diodes. There have been reports that the Stirling Power Alternator Protection Device can be effective at interrupting the field of the 50N.

  7. #7

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    Thanks. The Stirling Power Alternator Protection Device is definitely in the mix. The alarm signal looks like it can be used to shut off the field solenoid so no need for large wire to/from this device. My concern is when the BMSs in a multi-battery bank shut down the batteries at different times. Does this trip only when the last one shuts down? Still researching these.

    Jerry
    Last edited by Dtjoint; 09-16-2019 at 10:24 AM.
    Jerry Work
    Kerby, Oregon
    1997 Prevost Country Coach
    40 foot, no slides, Santa Fe
    decorating style

  8. #8
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    Guys, really. You are expecting ALL batteries to be shut down by each battery's BMS at the same time. If so, I think you have bigger issues as the BMS is for protection.

    What am I missing.


    Gil and Durlene
    2003 H-3 Hoffman Conversion

  9. #9

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    Obviously the Li battery BMSs will shut down at different times, if they ever do. The question I have is what happens if/when the last one shuts down. With the alternator only charging this bank of four to six 100ah Li batteries, by the time the last battery is fully charged the alternator would be putting out only a small charge current so I would think any resulting spike would be small, but there still could be a spike. That is what I would expect the Alternator protection device would catch if it ever happened.

    Did you ever encounter a Li only charging situation in your marine experience, Gil, or was it always issues of charging a combination of Li and lead acid?

    The work I have done so far designing Li conversion systems for the GMC motorhome community (which I will present in early October) has been for the case where both Li and lead acid batteries are being charged from one alternator. In that case the first alternator design GM ever implemented. It is a slip ring three wire design with a max output of either 80 or 100 amps. They were designed only to charge starting batteries so when pressed into service charging both starting and house batteries they often over heated. As GMC owners began to add larger house battery banks and inverters about ten to fifteen years ago the incidence of alternator failure soared. It looks like one of the battery isolation managers that alter duty cycle will help in the GMC case. Some are recommending changing out the three wire alternators for the newer one wire units which have a max output of 130 amps. I have no experience with those so don’t know if that would be a good idea or not.

    jerry
    Last edited by Dtjoint; 09-17-2019 at 11:09 AM.
    Jerry Work
    Kerby, Oregon
    1997 Prevost Country Coach
    40 foot, no slides, Santa Fe
    decorating style

  10. #10
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    Jerry,

    My only mixed battery or multi bank multi alternator experience has been AGM and FLA batteries.

    I can't imagine all lithium batteries in a multi battery bank being taken out of service at the same time. In fact, I'd be disappointed if one battery took itself out of service before the anticipated expiration.

    Definitely stay with an alternator that supports and external regulator. That's the only practical way of supporting an intelligent charge program. An external regulator is going to shutdown the alternator if all batteries are out of service. The question is does the VR shutdown the alternator faster than the loss of battery connectivity to the alternator. To eliminate the risk, a alternator protection device should be installed.

    Here's another design thought. Have you considered 2 banks both with a dedicated inverter/charger and alternator? This is a far more robust setup that doesn't cost much more. The biggest downside to this configuration is you won't get maximum battery run time. That can be overcome with a high current solenoid that connects the banks when their's no current inflow to the 2 banks. Just a thought.


    Gil and Durlene
    2003 H-3 Hoffman Conversion

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