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--- electrical:12v:directcharginglfp [2022/09/17 18:14]
frater_secessus [failures]
+++ electrical:12v:directcharginglfp [2022/10/12 18:33]
frater_secessus [analysis of van-relevant installs]
@@ Line 39: / Line 39: @@
   * standard regulators (no external regulators, internal regulator hacks, etc)
   * with rated capacities ≥120A((where stated))
+  * plain isolators, not voltage-boosting [[electrical:12v:b2b|DC-DC chargers]]
 Since it includes screenshots the data will be for installs documented before Sept 15, 2022.
@@ Line 183: / Line 184: @@
   * you **already own a DC-DC**
-  * you **need consistent, predictable charging**, like 40A over the next hour.  DC-DC will provide this((barring interference from big chassis loads, BMS protections, high ambients, etc));  isolator charging starts out high and drops linearly.  You might learn its behavior over time, but it will never be as easy as "40A for 1.5 hours = 60Ah".
+  * you **need consistent, predictable charging**, like 40A over the next hour.  DC-DC will provide this((barring interference from big chassis loads, BMS protections, high ambients, etc));  isolator charging starts out high and drops as battery voltage rises.  You might learn its behavior over time, but it will never be as easy as "40A for 1.5 hours = 60Ah".
   * you **don't want to think about the battery**.  DC-DC will either stop charging (Renogy) or drop to float (all others) when charging is complete.  Isolators need to be switched off after charging, if you are driving long enough to fully charge the bank.
-  * choosing wiring can require some effort
+  * **choosing wiring** can require some research
     * [[electrical:12v:alternator#wiring_for_the_isolator|with DC-DC chargers wire sizing is straightforward]]:  charger output rating + 20% to account for DC-DC conversion overhead
     * **if isolator wiring is already present** from a previous bank, test it while using a monitor or BMS info to watch actual current.  You may want to decrease fusing to equal the actual wire rating((rather thant he usual rating + 20%)) during testing.
     * **if starting from scratch** there is less to go on.
-      * In the van-relevant examples above LFP banks typically pull 0.33C, or 33A per 100Ah of capacity.
+      * The most conservative approach would be to size the wiring for 1C (non-critical).
-      * LFP manufacturers typically allow up to 0.5C charging for normal use.  One might
+      * In the van-relevant examples above LFP banks typically pull 0.33C, or 33A per 100Ah of capacity, so it might be acceptable to size them to 0.5C (noncritical).
+      * a set of heavy jumper cables and a clamp-on monitor might help assess max current draw before buying any wiring.
 If you are still interested, here is one approach to assessing your setup for direct charging lithium:

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