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--- electrical:12v:mandatory_dcdc [2023/05/08 11:15]
frater_secessus [situations where DC-DC is effectively required]
+++ electrical:12v:mandatory_dcdc [2024/07/15 13:15] (current)
frater_secessus [Is DC-DC charging mandatory?]
@@ Line 3: / Line 3: @@
 ====== Is DC-DC charging mandatory? ======
-Death and taxes are mandatory.  Gravity is mandatory.
+Death and taxes are mandatory.  Gravity is mandatory. Are DC-DC chargers mandatory? Ehh...
+In many/most situations, direct-charging the house bank with [[electrical:12v:alternator#combiners|a combiner]] (relay, isolator, VSR)  is both effective and inexpensive. Even [[electrical:12v:directcharginglfp|with lithium banks]].
-In many/most situations direct-charging the house bank with [[electrical:12v:alternator|a combiner]] (relay, isolator, VSR)  is both effective and inexpensive. Even [[electrical:12v:directcharginglfp|with lithium banks]].
+However, **some use cases may require a DC-to-DC charger**. These are much more intelligent (and expensive) devices that sit in between the vehicle batteries and the house batteries, and actively adjust both the voltage and current flowing from the vehicle's electrical system and into the house batteries.
-There //are// scenarios where one may want to [[electrical:12v:alternator#disabling_alternator_charging|disable the combiner]].
+**Note:** This article is just the TL;DR of DC-DC charger options. [[electrical:12v:b2b|More detailed info is here]].
-===== situations where DC-DC is effectively required =====
+===== Situations where DC-DC is effectively required =====
-  * small alternators vs. ginormous battery banks of any chemistry
+  * When the vehicle has a smart (variable-voltage) alternator
-  * smart (variable-voltage) alternators, more common in Europe
+    * Common on European vehicles, and on American vehicles newer than ~2017
-  * exotic alternator or battery bank voltages
+  * Small alternators vs. ginormous battery banks of //any// chemistry
-  * if one needs relatively-stable charge rates((Direct-charging from the alternator with a combiner of some kind tends to start out strongest when battery bank voltage is lowest, and taper as the bank voltage rises; I=V/R. This effect is most noticeable with flooded lead acid batteries and least noticeable with Lithium, at least after reaching the flat middle area of the voltage curve.))
+  * Exotic alternator or battery bank voltages, including setups like 24v house bank and 12v alternator (or //vice versa//)
-  * if you want to impose an arbitrary current limit((0.2C for Gel, 0.4C for lithium, etc))
+  * If one needs relatively-stable charge rates((direct-charging rates "taper" as bank voltage rises))
+  * If you want to impose an arbitrary current limit((0.2C for Gel, 0.4C for lithium, etc))
+  * when the alternator is the only charging source for the lead-chemistry house batteries. In this case DC-DC won't help with [[electrical:12v:charging#absorption_stage|Absorption]] duration((the vehicle is usually not running long enough to fully charge lead-chemistry batteries)) but it can help with Absorption //voltage//.
   * <del>when an influencer says so</del>
   * <del>when Chicken Little claims you need one or the sky will fall</del>
-===== situations where DC-DC is preferable =====
+===== Situations where DC-DC is preferable =====
-  * lead house bank when alternator is [[electrical:12v:alt_and_solar#how_solar_helps|the only charging source]]
-In this case DC-DC won't help with [[electrical:12v:charging#absorption_stage|Absorption]] duration((the vehicle is usually not running long enough to fully charge lead-chemistry batteries fully)) but it can help with Absorption //voltage//.
+  * when the alternator is the sole charging source for LiFePO4.  In this situation DC-DC will deliver more predictable and often faster charging, particularly when the bank is at higher SoC.

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