External Battery Charger

Basil48192 · June 10

I'm sure this has been covered, but I haven't been able to find the specific information.
I am installing two, new lithium 12v batteries, in parallel, into my 2021 T@B 320S.

Due to all of the issues I've seen on this forum, I am not changing out my converter. My plan is to let the old converter charge the batteries to around 85% (or whatever it ends up being), then letting my solar panels charge them up to 100%. I realize I need to change my solar controller settings.

Lastly, in the event we have little sun, I purchased a Victron external battery charger. Because I shouldn't need it very often, my plan was to simply connect to my installed batteries with alligator clips and then remove them when complete.

My main question: Will turning off my factory battery disconnect switch be sufficient to isolate the T@B while charging with the Victron? I know there are a few items that are powered outside of the switch.

Thank you in advance!

elbolillo · June 10

Turning the battery disconnect off will isolate it from the Tab. I had a Victron external charger that I connected to the battery using the supplied M8 eyelet cable. That way the cable was always connected and I just had to connect the charger to it. I never turned off the disconnect.

Basil48192 · June 11

@elbolillo. Thank you! I am planning on doing exactly the same thing. So, you didn't turn the disconnect off, even when you were charging?

elbolillo · June 11

Basil48192 said:

@elbolillo. Thank you! I am planning on doing exactly the same thing. So, you didn't turn the disconnect off, even when you were charging?

No. I didn’t see any reason to do so. I didn’t turn off the disconnect when charging via solar. And I didn’t use the WFCO converter to charge either.

Horigan · June 11

You can permanently install the Li charger in parallel to the non-Li WFCO and Li solar chargers. That's what I did and have had no issues.

Basil48192 · June 21

One more question (maybe!):
My T@B sits in my driveway while not in use. Due to small parasitic draws, the batteries drop down a few percent at night, then the rooftop solar brings them back up to 100% during the day. Is this a good practice? I've been over-whelmed with the information on the internet...so I'm not really sure.

Horigan · June 21

No issue with that. Is the draw with the battery switch off? A measurable drop over night with the battery switch off would be surprising.

Basil48192 · June 21

@Horigan. No, that is with the switch on. But it still seems a little high. It's basically the draw from all of the device screens and lights (CO/Propane detector, smoke detector, radio screen, etc.). According to my solar panel, it seems to be about a 0.5 amp draw. So, for the roughly 10 hours that my panel doesn't get light (it faces north), that would equate to about a 5 amp/hour loss. Since I have 200 AH capacity, that would drop the SOC down to about 97.5%.

Horigan · June 22

Okay. Makes sense.

mjwaldner · June 24

When I did our lithium upgrade I decided to go with a Victron Blue Smart charger instead of upgrading the built in charger. This has worked out great. I installed it just behind the WFCO power center. It technically would fit in the same place the WFCO charger is but I was concerned about over heating. I keep the old one in place but disconnected it. This way we have a backup if it was ever needed.

https://a.co/d/2DJglYt

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