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After a frustrating experience with a Victron DC-DC charger (details in another thread), I restored the wiring to the original configuration. The 7-pin charging wire (10AWG) is connected to the bus that connects the batteries to the camper dc circuits. The 7-pin ground (10AWG) is tied into the terminal block with the other grounds. I kept a lead-acid 12 volt battery as backup to my new lithium batteries. So I connected it first and used a multimeter with a current clamp to see the current flow situation. Nothing exciting there, which is what I expect since that is what I’ve dealt with for years now.
The real question is when I tie into the lithium batteries. Like many of you, I watched the video where the draw from a lithium battery was literally burning up an alternator. My understanding from that is the most critical situation is when the engine is idling and the alternator is subject to a high load and can’t properly cool itself. So I switched to the lithium batteries and I did not see any high amps being drawn.
The initial condition was basically steady state, the lithium batteries are meeting the basic needs of the camper (13.11v, discharge 1.53A (first figure). When I plugged the camper into the truck (not running) via the 7-pin, the discharge from the batteries jumped to 2.30A. This is because the battery on the truck is sitting with a lower voltage than the lithium batteries. When I started the truck, the draw from the lithium batteries spiked to about 14A for an instant. Then the truck alternator started charging the lithium batteries at about 3 to 4A (second figure). The whole sequence can be seen in the third figure. Connected to the truck battery; downward spike when starting the truck; charging from alternator; shut down engine.
I did the same test earlier in the day, but had run the truck before testing the lead-acid battery, and the lithium batteries were off. The fourth figure shows this sequence. The lithium batteries drew over 5A from the truck batteries when connected (and the truck not running). I think this is because the truck battery had a higher charge because the alternator was charging it shortly before. Then started the engine, the charge to the lithium batteries was 3 to 4A. Shut the engine down, and the lithium batteries went to a normal discharge to the camper.
I reviewing this, I don’t see a reason not to have the lithium batteries connected to the truck the same way the lead-acid batteries were. I could take it for a driving test, but I don’t expect it to see much different results. Does anyone see this differently? Or have suggestions of a different scenario that might be more critical and I should test?
I do like the idea of charging while driving. So I will continue to look into the DC-DC charger, but if I don’t resolve it before our next trip, I am not going to worry about using the lithiums as drop ins with the original electrical configuration.
If I am missing something, please let me know.
Thanks, Dave
The real question is when I tie into the lithium batteries. Like many of you, I watched the video where the draw from a lithium battery was literally burning up an alternator. My understanding from that is the most critical situation is when the engine is idling and the alternator is subject to a high load and can’t properly cool itself. So I switched to the lithium batteries and I did not see any high amps being drawn.
The initial condition was basically steady state, the lithium batteries are meeting the basic needs of the camper (13.11v, discharge 1.53A (first figure). When I plugged the camper into the truck (not running) via the 7-pin, the discharge from the batteries jumped to 2.30A. This is because the battery on the truck is sitting with a lower voltage than the lithium batteries. When I started the truck, the draw from the lithium batteries spiked to about 14A for an instant. Then the truck alternator started charging the lithium batteries at about 3 to 4A (second figure). The whole sequence can be seen in the third figure. Connected to the truck battery; downward spike when starting the truck; charging from alternator; shut down engine.
I did the same test earlier in the day, but had run the truck before testing the lead-acid battery, and the lithium batteries were off. The fourth figure shows this sequence. The lithium batteries drew over 5A from the truck batteries when connected (and the truck not running). I think this is because the truck battery had a higher charge because the alternator was charging it shortly before. Then started the engine, the charge to the lithium batteries was 3 to 4A. Shut the engine down, and the lithium batteries went to a normal discharge to the camper.
I reviewing this, I don’t see a reason not to have the lithium batteries connected to the truck the same way the lead-acid batteries were. I could take it for a driving test, but I don’t expect it to see much different results. Does anyone see this differently? Or have suggestions of a different scenario that might be more critical and I should test?
I do like the idea of charging while driving. So I will continue to look into the DC-DC charger, but if I don’t resolve it before our next trip, I am not going to worry about using the lithiums as drop ins with the original electrical configuration.
If I am missing something, please let me know.
Thanks, Dave
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