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Open Roads Forum  >  Tech Issues

 > Converter voltage drop

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mpvuk

Portland, OR

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Posted: 06/23/22 05:22pm Link  |  Quote  |  Print  |  Notify Moderator

theoldwizard1 wrote:

Any QUALITY converter/charger will have a specific setting for LiFePO4. Use it !

Personally, I would just eliminate the converter and buy an inverter/charger/automatic transfer switch.


New to this so hopefully replying in proper format...all LFE specific converter/chargers I've found have a 14.6V bulk phase. My battery mfg says to stay at 14.4 or less in bulk. Are there LFE chargers that start at 14.4? Regarding an inverter/charger, I already have a 2200W pure sine wave inverter that Works great. My best value seems to be using existing inverter and upgrading the converter.

BFL13

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Posted: 06/23/22 06:20pm Link  |  Quote  |  Print  |  Notify Moderator

By the time the charger gets the battery to 14.4 volts, amps will have tapered down so there will be little voltage drop.

Standard PD converters do 14.4 not 14.6, so you want a standard PD converter (NOT their LFP model!!!) in the 45 amp range. Make sure it has the Charge Wizard or built in version of that so you can pick and choose between 14.4 and 13.6 yourself.

It is a good idea to have a battery monitor so you can see amps as well as voltage and see AH count so you know where you are at, and not hit the 13.6 button too soon. I have a Renogy 500A one that does the job nicely and is not expensive, eg.

It seems there is no one correct 14.6v that applies to all LFPs, so you are right to look carefully. It is like "AGM" voltage settings that are lower than for Flooded batts--except there are AGMs that specify 14.7v for charging.

However, if Battleborn says to use 14.6 on theirs, I don't know why anybody would choose not to if they have BB LFPs, and use 14.X instead. Up to the individual LFP owner I guess.


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pianotuna

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Posted: 06/23/22 11:43pm Link  |  Quote  |  Print  |  Notify Moderator

I'd go inverter/charger. Li follow the makers recommendations.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Microlite Mike

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Posted: 06/24/22 10:00am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

By the time the charger gets the battery to 14.4 volts, amps will have tapered down so there will be little voltage drop.

Standard PD converters do 14.4 not 14.6, so you want a standard PD converter (NOT their LFP model!!!) in the 45 amp range. Make sure it has the Charge Wizard or built in version of that so you can pick and choose between 14.4 and 13.6 yourself.

It is a good idea to have a battery monitor so you can see amps as well as voltage and see AH count so you know where you are at, and not hit the 13.6 button too soon. I have a Renogy 500A one that does the job nicely and is not expensive, eg.

It seems there is no one correct 14.6v that applies to all LFPs, so you are right to look carefully. It is like "AGM" voltage settings that are lower than for Flooded batts--except there are AGMs that specify 14.7v for charging.

However, if Battleborn says to use 14.6 on theirs, I don't know why anybody would choose not to if they have BB LFPs, and use 14.X instead. Up to the individual LFP owner I guess.


LiFePo4 batteries need >14 volts at the end of their charge cycle to assure proper cell balance. Whether 14.2, 14.4, or 14.6 really doesn't matter much and their BMS will actually shut off charging current when the voltage exceeds the manufacture's setting (14.7v on my Battleborn's).

If one is boondocking and cycling the batteries regularly a converter that delivers a fixed voltage from 14.4-14.6 v will charge quickly, depending on battery bank capacity and output rating of converter. Once charged the generator is usually shut down and the battery starts another cycle. No harm done to batteries with the "fixed voltage" as the battery isn't held at this high voltage for an extended period (measured in weeks and months, not hours or days).

When tied to shore power the recommendation is to just charge batteries to 100% and disconnect batteries, running only on Converter output which was sized by the manufacturer to run all 12v items without the need for a battery. If connected to shore power for months and months, Battleborn recommends to just switch batteries back online a recharge every 6 months.

If one has a converter that won't deliver >14 volts long enough to top balance the cells of a LiFePo4 battery, one economical solution is to purchase a battery maintainer that has "Lithium" capability. A NOCO Genius 2 amp smart charger is only $49 on Amazon and can be directly connected to the battery when running the generator or connected to shore power for topping off and cell balancing. Don't even need to shut off the converter as once the battery voltage reaches the max of the converter, the converter will essentially stop delivering current to the battery. The "maintainer will take over until it's max voltage is reached when cells are balanced and battery is fully charged.


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otrfun

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Posted: 06/24/22 10:56am Link  |  Quote  |  Print  |  Notify Moderator

Microlite Mike wrote:

LiFePo4 batteries need >14 volts at the end of their charge cycle to assure proper cell balance. Whether 14.2, 14.4, or 14.6 really doesn't matter much and their BMS will actually shut off charging current when the voltage exceeds the manufacture's setting (14.7v on my Battleborn's).

If one is boondocking and cycling the batteries regularly a converter that delivers a fixed voltage from 14.4-14.6 v will charge quickly, depending on battery bank capacity and output rating of converter. Once charged the generator is usually shut down and the battery starts another cycle. No harm done to batteries with the "fixed voltage" as the battery isn't held at this high voltage for an extended period (measured in weeks and months, not hours or days).

When tied to shore power the recommendation is to just charge batteries to 100% and disconnect batteries, running only on Converter output which was sized by the manufacturer to run all 12v items without the need for a battery. If connected to shore power for months and months, Battleborn recommends to just switch batteries back online a recharge every 6 months.

If one has a converter that won't deliver >14 volts long enough to top balance the cells of a LiFePo4 battery, one economical solution is to purchase a battery maintainer that has "Lithium" capability. A NOCO Genius 2 amp smart charger is only $49 on Amazon and can be directly connected to the battery when running the generator or connected to shore power for topping off and cell balancing. Don't even need to shut off the converter as once the battery voltage reaches the max of the converter, the converter will essentially stop delivering current to the battery. The "maintainer will take over until it's max voltage is reached when cells are balanced and battery is fully charged.
All the monitoring, switching on and off of the converter (and generator) you've described, is necessary if you use single-stage converter/charger---especially if it's a 14.6v unit.

If you purchase/use a multi-stage converter/charger (13.2/13.6/14.4 or 13.6/14.6) none of the monitoring or switching you've described would be necessary.

BFL13

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Posted: 06/24/22 11:16am Link  |  Quote  |  Print  |  Notify Moderator

The charging specs for this LFP are interesting. They say 14.6 max but 14.4 is ok. BMS cut off is 14.8. Big surprise ? Is balancing at 13.6.

https://www.canbat.com/downloads/CLI100-12.pdf

Also it says resistance is 30 mOhms at 50% SOC. An AGM spec says IR is 5 mOhms, but does not say when (probably at 25C/77F but ? SOC) that 30 mOhms seems way high where the usual story is that LFPs have low IR?

On shore power you can disconnect the LFP and run on converter for 12v. I still have not got an answer for what you do if your rig has an inverter/charger. Last heard, an inverter/ charger will not operate at 12v unless it it is connected to a battery to run its own systems. Not sure if it still would do 120v pass through.

3 tons

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Posted: 06/24/22 11:34am Link  |  Quote  |  Print  |  Notify Moderator

FWIW, LFP Simple Rules I live by - JMO

1) Except for occasional cell re-balancing, no need to fully recharge a LFP on a ‘wet-cell like’ routine basis…

2) Monitor closely the last few percent of recharge to 100% SOC thru to end of cell-balancing activity…

3) Post cell-balancing activity, discontinue Boost charging (avoiding the longer term) - shut-off 12v converter (at breaker) and thereafter run minor 12v loads from the battery (this still supplies active 120v for larger appliances). When off-grid, LFP can be supplemented with harvest…

4) For long term storage, disconnect and store LFP somewhere in the mid-SOC range (60-40’ish % SOC range).

3 tons

3 tons

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Posted: 06/24/22 11:41am Link  |  Quote  |  Print  |  Notify Moderator

BFL said:

“I still have not got an answer for what you do if your rig has an inverter/charger. Last heard, an inverter/ charger will not operate at 12v unless it it is connected to a battery to run its own systems. Not sure if it still would do 120v pass through.”

************

My pass-thru inverter-charger always stays connected to the batteries, whether on shore power or not…As power passes thru, it normally remains in just the ‘standby mode’ (or, OFF) - it’s built-in ATS switch prevents conflicts with incoming shore power…

3 tons

Gdetrailer

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Posted: 06/24/22 12:32pm Link  |  Quote  |  Print  |  Notify Moderator

3 tons wrote:

FWIW, LFP Simple Rules I live by - JMO

1) Except for occasional cell re-balancing, no need to fully recharge a LFP on a ‘wet-cell like’ routine basis…

2) Monitor closely the last few percent of recharge to 100% SOC thru to end of cell-balancing activity…

3) Post cell-balancing activity, discontinue Boost charging (avoiding the longer term) - shut-off 12v converter (at breaker) and thereafter run minor 12v loads from the battery (this still supplies active 120v for larger appliances). When off-grid, LFP can be supplemented with harvest…

4) For long term storage, disconnect and store LFP somewhere in the mid-SOC range (60-40’ish % SOC range).

3 tons


I thought the idea of LFP batteries was to eliminate "maintenance" and hassle [emoticon]

Looks like you signed on to a lot of work and hassle [emoticon]

MY FLA requires a simple plug in and forget and once a year check and add water if needed [emoticon] Maximizing my enjoyment of my RV without the work.

My PD takes very good care of my FLAs yr round and keeps them in good working condition that takes them well over 10yrs of life.

3 tons

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Posted: 06/24/22 12:50pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer says:

“Looks like you signed on to a lot of work and hassle….”

Maybe so to the uninitiated (or mischievous?? - I donno…), but winning over FLA converts was not my goal, nor a cogent point of the OP’s thread…Perhaps you should consider sticking with wet-cells and just feel self-assured (vindicated…) about what’s working well for you - Glad to hear it!!

3 tons

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