Whats the latest in DC-DC charging on a vehicle that doesnt break the bank?

[fat_old_sun]

If the LFP battery voltage is < 13.2 then current will flow.
I must be missing something.

Yes, if the voltage is less than 13.2, a current will flow. However, the resting voltage of a LFP pack will be above 13.2V for SoC 30% or more and the controller's float voltage will have no effect. The voltage will sag if there's draw. In this case, the controller will either stay in float or go in to full charge mode, depending on the voltage sag.

 

[John Frum]

Yes, if the voltage is less than 13.2, a current will flow. However, the resting voltage of a LFP pack will be above 13.2V for SoC 30% or more and the controller's float voltage will have no effect. The voltage will sag if there's draw. In this case, the controller will either stay in float or go in to full charge mode, depending on the voltage sag.

I guess I wasn't missing anything after all.
Thanks.

 

[Bhupinder]

Alternators put out 14.5V at high revs and for a short time immediately after engine start. ATt other times, it is usually 13.5-13.8.

Not exactly sure, what it is about? But each LA cell needs somewhere around 2.35 Volts to be fully charged (14.1V for 6 cells).
Alternators must put a slightly higher voltage, continuously to be able to do that.

Besides, 14.5V does not provide the voltage differential required for most MPPT controllers.

What could be behind that?
Why should there be a high enough voltage differential for SCC to open charging FETs?
They should be regulated by present battery voltage and not the PV input (barring over voltage situation).
Going by that @14.5V on the Inputs side, an SCC should be able to charge LifePo4 batteries sufficiently (13.4V).
However, never tested that arrangement. Do you have any experience with this?

 

[fat_old_sun]

Not exactly sure, what it is about? But each LA cell needs somewhere around 2.35 Volts to be fully charged (14.1V for 6 cells).
Alternators must put a slightly higher voltage, continuously to be able to do that.

[illustration deleted]

What could be behind that?
Why should there be a high enough voltage differential for SCC to open charging FETs?
They should be regulated by present battery voltage and not the PV input (barring over voltage situation).
Going by that @14.5V on the Inputs side, an SCC should be able to charge LifePo4 batteries sufficiently (13.4V).
However, never tested that arrangement. Do you have any experience with this?

Engine batteries rarely get discharged very much. Starting an engine consumes 2 or 3 Amp-hrs. It does not take the alternator to return that charge to the battery, causing the battery voltage to reach 14.4 and triggering the control loop to drop the voltage to float. Newer vehicles have a shunt & associated electronics that raise the voltage if it senses a need. Any vehicle 10 years or older is unlikely to have this feature.

I made that comment in the context of MPPT controllers. They are much more than a simple FET turned on/off. They are DC-DC converters with an added feature on their input side - being able to track a panel's sweet spot by actively changing the input conductance. The whole process of DC-DC conversion requires some voltage differential. There are "low dropout" converter designs which can function with very low differentials. To my knowledge these designs are not used in most MPPT controllers.

At 13.4V, an LFP pack is not sufficiently charged.

Yes, I do have experience with these. I have pile of controllers and related devices - home grown & commercial - in my shack.

 

[mkaye]

Bogart said the SC 2030 will drop 0.3V

 

[fat_old_sun]

Bogart said the SC 2030 will drop 0.3V

It's probably 0.2 V @ 30 Amps based on the measurements I have made. We install Bogart products exclusively (due to their reliability/robustness) in van conversions we do for research groups.

 

[Bhupinder]

Engine batteries rarely get discharged very much. Starting an engine consumes 2 or 3 Amp-hrs. It does not take the alternator to return that charge to the battery, causing the battery voltage to reach 14.4 and triggering the control loop to drop the voltage to float. Newer vehicles have a shunt & associated electronics that raise the voltage if it senses a need. Any vehicle 10 years or older is unlikely to have this feature.

I made that comment in the context of MPPT controllers. They are much more than a simple FET turned on/off. They are DC-DC converters with an added feature on their input side - being able to track a panel's sweet spot by actively changing the input conductance. The whole process of DC-DC conversion requires some voltage differential. There are "low dropout" converter designs which can function with very low differentials. To my knowledge these designs are not used in most MPPT controllers.

At 13.4V, an LFP pack is not sufficiently charged.

Yes, I do have experience with these. I have pile of controllers and related devices - home grown & commercial - in my shack.

My experiences are different. I think we can happily agree to disagree. Cheers!