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smack asked

Phoenix Smart charger goes straight to absorption


I have a Phoenix Smart Charger IP42 50A 1+1 that I am using to charge my lithium bank (not victron, DIY build).
My problem is that only minutes after switching on the charger, even if batteries are almost empty, the charger goes to absorption stage. The voltage (as shown in screenshots below) have not reached my set absorption voltage. The charger is not charging at max capacity, not is it charging at any constant voltage. The voltage changes slightly up and down. I don't see how this should be possible?screenshot-20210529-172923.jpg


I really just want my charger to go full power constant current until my BMS system switches it of. I have set the absorption voltage higher in the charger than in my BMS. I do not want to use the supply function in the charger since I like the fact that the settings in the charger will protect my batteries should the BMS fail somehow.


Now the absorption timer kicked in and it transitioned to float. Dropping the voltage and charge current even more.... :-(

Still nowhere near absorption voltage I set...


battery chargingcharger
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Jesse avatar image Jesse commented ·

Any progress?

Curious issue. Is the charger possibly overheating? Have you checked for voltage drop across wires or safety switches? All should be quite low, less that 0.1V ideally.

Have you tried setting the charge current to 40 or even 20 amps and see if that fixes the apparent logic issues? Otherwise maybe something is faulty?

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smack avatar image smack Jesse commented ·
No progress... problem persists.

I have no abnormal voltage drops. All brand new 16mm2 (short) cables and connectors.

If I run it at half speed (25A) it works. Overheating perhaps. But according to manual the charger should just reduce its output if it gets to hot. Should not affect charge phase or logic according to me. Also, not much of a 50A charger if it cant charge at 50A for more than a few minutes :-)

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1 Answer
Paul B avatar image
Paul B answered ·

The charger will change from bulk to absolution as soon as the absolution voltage is reached at its connections - so you need to look at some history and monitor the voltage , some VRM screen shots of the battery voltages would be helpfull and a time factor as to how long it stays on bulk charge. So monitor the voltage especially as it goes from bulk to absorption. If its over heating then more air flow is need over the unit.

the above a re few things to check

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