Couple of questions about DC-Dc charging
I've been thinking about adding a DC-DC charger now that I've added 400 amp hours of AGM batteries. There are lots of useful posts but I haven't run into a couple of things I'm curious about. One ...
Forum Discussion
When I post a reply and specify a particular charging system and a particular battery, I mean that particular charging system and that particular battery chemistry. If you want an opinion on a different setup, then so state it. "How about an X system with an X battery?"
As far as the charging system is concerned, the Ford 3G, 4G, and 6G alternators are the only models with the OPs stated output amperage. The ECU models begin at 135 amperes and end at 270 amperes, some are dual alternator models.
Acceptable charging profiles are radically different for lithium chemistry batteries. So a charging system that is acceptable for use unchanged with an absorbed glass mat chemistry may be totally unacceptable for use with a lithium battery.
To compound the matter, newer vehicles control charging profiles via the central ECU and ignore earlier charging regimens in favor of protecting power generators or squeezing an extra tenth of a mile per gallon out of fuel. And again, newer systems do not incorporate charging algorithms for lithium chemistry.
Therefore, the use of a throttling resistance wire to protect an alternator from overheating is utterly inappropriate when lithium batteries are involved. The keywords are utterly and inappropriate.
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Moving on to other systems, I have noted that as far as lithium batteries for RVs is concerned, different manufacturers have listed different recharging profiles for their products. Usually, limitations on voltage are the key values to keep in mind.
Thus, I cannot help but feel that any and all models utilizing OEM specifications for charging system performance are totally inappropriate for use with lithium chemistry batteries. All, means, from the 1920s to 2022 inclusive.
Therefore, with lithium chemistry, a DC to DC power supply makes perfect sense as long as it's charging profile agrees with specifications put forth by the lithium battery manufacturer.
In the choice of a DC to DC power supplies, amperage limiting to protect the alternator(s) is automatic.
But total capacity of a DC to DC converter must be considered. For an example, a 20-ampere converter used on a vehicle with an existing 30-ampere hotel burden means the system would endure a net battery discharge of ten amperes while traveling down the highway.
ALTERNATOR CAPACITY
I know of no current OEM alternator that can endure maximum amperage output for other than a few minutes. The design limitation is primarily in the rectifier system principally heat sink radiating area in conjunction with airflow temperature and CFM. There is no magic design formula, and increasing the capacity of the rectifiers is not a magic solution. A heat sink is good for so many vf watts of saturation and no more. Extremes in temperature cooling air inlet aggravates the limitation.
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This is intended as a general overview. I hope it will suffice.
As far as the charging system is concerned, the Ford 3G, 4G, and 6G alternators are the only models with the OPs stated output amperage. The ECU models begin at 135 amperes and end at 270 amperes, some are dual alternator models.
Acceptable charging profiles are radically different for lithium chemistry batteries. So a charging system that is acceptable for use unchanged with an absorbed glass mat chemistry may be totally unacceptable for use with a lithium battery.
To compound the matter, newer vehicles control charging profiles via the central ECU and ignore earlier charging regimens in favor of protecting power generators or squeezing an extra tenth of a mile per gallon out of fuel. And again, newer systems do not incorporate charging algorithms for lithium chemistry.
Therefore, the use of a throttling resistance wire to protect an alternator from overheating is utterly inappropriate when lithium batteries are involved. The keywords are utterly and inappropriate.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Moving on to other systems, I have noted that as far as lithium batteries for RVs is concerned, different manufacturers have listed different recharging profiles for their products. Usually, limitations on voltage are the key values to keep in mind.
Thus, I cannot help but feel that any and all models utilizing OEM specifications for charging system performance are totally inappropriate for use with lithium chemistry batteries. All, means, from the 1920s to 2022 inclusive.
Therefore, with lithium chemistry, a DC to DC power supply makes perfect sense as long as it's charging profile agrees with specifications put forth by the lithium battery manufacturer.
In the choice of a DC to DC power supplies, amperage limiting to protect the alternator(s) is automatic.
But total capacity of a DC to DC converter must be considered. For an example, a 20-ampere converter used on a vehicle with an existing 30-ampere hotel burden means the system would endure a net battery discharge of ten amperes while traveling down the highway.
ALTERNATOR CAPACITY
I know of no current OEM alternator that can endure maximum amperage output for other than a few minutes. The design limitation is primarily in the rectifier system principally heat sink radiating area in conjunction with airflow temperature and CFM. There is no magic design formula, and increasing the capacity of the rectifiers is not a magic solution. A heat sink is good for so many vf watts of saturation and no more. Extremes in temperature cooling air inlet aggravates the limitation.
--------------------------------------------------------------------------------------------------------------------------------------------------------
This is intended as a general overview. I hope it will suffice.
