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gbzeke avatar image
gbzeke asked

A possible new idea for using lead acid with lithium using DC chargers

I’ve done a bit of research and haven’t seen anything quite along these lines. Of course, it could be out there and I just missed it, but I would greatly appreciate some feedback as to its feasibility.

I have a 2015 camper van with a 400 Ah AGM house battery which is charged by a dedicated second alternator, 280 amps, and I want to add two 100 Ah lithium batteries.

I would use a Victron Orion Smart 30 amp DC/DC charger taking output from the second alternator to charge the lithium batteries. The AGM battery would continue to be charged by the alternator as before. When parked and camping, I would have a second Victron DC charger which would take output from the lithium batteries to charge up the AGM battery when needed.

There would be an SPDT switch so only one DC charger could operate at a time, or they could both be off. I know there would be inefficiencies in the power transfer from the lithium batteries to the AGM battery, but otherwise it seems like a simple and easy way to add lithium batteries to a lead acid battery system and keep things safe. This system also protects the alternator from any possible issues with the lithium batteries without any major modifications. I would, of course, follow the Victron guide for wire gauge and fuses. What do you think?

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3 Answers
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kevgermany answered ·

You need to take into consideration connection sequences for the chargers. Also voltage settings for charging to work. Best check with the manuals.

However no need to do it that way.

Make sure you have isolated Orions.

Use the LH terminals on the Orions to switch them on and off by bridging the contacts. I think you need DPDT, not spdt. But this is low current.

Configure alternator/AGM Orion to lithium to charge once AGM voltage hits, say, 14.4V i.e. normal charge settings.

Configure Lithium to AGM Orion to charge with lower lithium input voltage. Normally the Orion won't start with just battery voltage.




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gbzeke avatar image gbzeke commented ·
Thanks for your response! Yes, I will have isolated Orions. I believe I understand it all except for the switch. I would use the LH terminals and the switch I was planning on using was a SPDT, on-off-on, low current. The switch would only allow one or the other Orion to be on, but never both. Or both could be off. I'm not sure I understand DPDT switches, in general. I did check youtube to learn about them and I didn't see how they'd be used here.
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kevgermany answered ·

I'm never sure on these names. Just need a three position switch that will bridge LH on one or the other, with neither bridged in the middle

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gbzeke answered ·

Cool, thanks

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