I am looking to expand my use of the Charger 2 by adding a 12v LiFePO4 to my current setup that is using a ac200max. The 12v LiFePO4 mainly is to power a 12v rooftop aircon.
A few ?s:
Can the Charger 2 charge the ac200max while also using shore power and its AC charger?
Can the Charger 2 charge the 12v LiFePO4 while also using shore power and its AC charger?
If not, do I need a disconnect for the 12v LiFePO4 while charging from the Charger 2?
Am I correct that the CHG port to 12v LiFePO4 will be slow charging with a max of 288w?
Can the ac200max be assigned to ‘reverse charge’ ie charge the 12v LiFePO4?
Keeping in mind conversion loss, while not on shore power, can I get faster charging by plugging the 12v LiFePO4 AC charger into the ac200max while using alternator charging?
My use cases are:
Use solar while parked to top off both the ac200max and the 12v LiFePO4
Alternator charging and some solar to charge / top off both the ac200max and the 12v LiFePO4
Use shore power to charge the 12v LiFePO4 for running the aircon while boondocking
In a pinch, use alternator idling charging to top both the ac200max and the 12v LiFePO4.
You need to read the charger 2 FAQ and PDF manual which has diagrams and answers so these questions. The charger 2 has lots of quirks, including if reverse charging the car batteries, it’s not charging anything else.
@ben446 I don’t have definite answers to all of these, but
is definitely doable if the ac200max supports charging its own battery via one of its expansion battery ports, this is really controlled by the ac200 not by the charger2.
Electrically, it should be doable, but the BMS on the ac200 might not like it; essentially you’re saying to it: “I’m an attached battery whose voltage is higher than yours, rebalance the overall system by transferring some of my stored energy to yourself”.
.
Again, this isn’t controlled by the charger2 but in this case it’s controlled by the 12v lifepo4 battery or its 12v charger, if the shore power is connected there’s nothing stopping you from connecting both the 12v charger and the ac200 charger, you’ll get efficiency losses going through the ac200 (ac>dc to the ac200 and then dc>dc to 12v from the charger2). See next point though as that’s related.
.
You may want disconnects on the two charging lines to the 12v lifepo4 battery, that way you can prioritise one source or the other manually. Depending on the high-voltage disconnect settings in the charger2 and the 12v charger, they may fight each other and cycle through triggering each others’ high voltage disconnect limits, in which case you would only be able to use either the charger2 or the 12v charger to charge the lifepo4 battery, not both at once.
I don’t know what the charger2 disconnect settings are though; your best option is probably just to give it a short try and see what happens, it shouldn’t break anything doing that.
.
Yes, you’re limited by the max amps of the output, so you may get a bit more than 288w due to needing to supply a voltage higher than 12v to charge a “12v” battery, maybe as high as 345-350w during the bulk/absorption stage. This is why 48v batteries are generally used in home systems these days, as you can make the terminals/connectors/cables all that much smaller for the same overall power output, watts/power being a function of volts multiplied by amps and all (but you may already know that).
.
If you want to charge the 12v lifepo4 from the ac200 you may need a dc hub into the charger2, but the dc hub may not support appropriate charging voltages from its 12v output, Bluetti or someone who’s tried it need to answer this one. It’s not clear from the docs whether CHG output is enabled when only the BAT port (from the ac200) has voltage.
.
Yes I think you would be able to get faster charging by plugging the 12v charger into the ac200 while you’re not connected to shore power. The ac200 supports 960w easily enough. The main thing to look out for is what I said above for 2 and 3, you may need to disconnect CHG while you do that.
F0551L Thank you for the very detailed answer. My original post assumed I could charge the 12v LiFePO4 from the CHG port on the Charger 2. Now I am not sure if that is possible. Any thoughts?
As far as I can tell from all of Bluetti’s public documentation (and not having a charger2 on hand to try it), the CHG port is explicitly meant to be for charging non-Bluetti batteries, with the BAT port being intended for Bluetti batteries and power stations. The charger2 is also apparently smart enough to auto-detect the voltage of the third-party batteries (on CHG) so long as they’re in the 12v-60v range.
So I’m pretty sure the charger2 is explicitly built to support charging random 12v batteries especially lifepo4 ones.
The charger1 on the other hand only does voltage boosting from a 12v alternator input, and therefore the minimum output voltage is 15v which your 12v lifepo4 may not like, depending on its BMS.
A safety tip on wiring this up, it would be an extremely good idea to have a double-pole double-throw change-over switch on your 12v battery input cables, so that either the 960w charger or the CHG can be connected at once, but not both. That way it’s physically impossible to have them tripping each other out (as you can’t turn on both inputs at the same time).
