question

Mait Kindlam avatar image
Mait Kindlam asked

ORION Charger and MPPT on a boat with AGM and LiFePo4 batteries

Hi! I am working on a "simple" diagram for a sailboat.

All charging sources (including 4pcs MPPT 75/15) go to Charge Bus Bar that feeds LiFePo4 house battery.

From the same Charge Bus Bar I am going to feed the ORION DC-DC Charger to charge the AGM starter battery. The AGM start battery will supply also the bilge pump.

When I leave the boat for longer period, I would like to disconnect the LiFePo4 house battery to store it at 50-70% SOC as recommended (all charge sources and loads disconnected).

The AGM battery remains connected to keep the Bilge Pump working.

Now the question:

Will the AGM battery get solar charge, when MPPT supplies voltage to the Charge Bus Bar and from there to ORION Charger, but no other battery is connected to the Charge Bus Bar (in other words: no battery connected to MPPT). oe36-drop-in-lfp-agm-windlass-wiring-diagram-24052.jpg

MPPT ControllersLithium Batteryorion dc-dc
oe36-drop-in-lfp-agm-windlass-wiring-diagram-24052.jpg (2.6 MiB)
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2 Answers
mvas avatar image
mvas answered ·

Copy & Paste from FAQ #4:

Can the output of the MPPT be used as a power supply, thus without batteries?

The answer is ... it depends on the type of load.

During low current situations the MPPT control bandwidth is too small to be able to maintain a stable voltage. The result is that loads that need to see a stable voltage before they can activate or loads that require a certain “under voltage” to active will not be able to run.

Loads where under voltage does not apply, like light globes, can be operated without any problems.

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kevgermany avatar image
kevgermany answered ·

Couple of issues here.

MPPT must have a battery on output.

Orion charger setup. Usual method is that it's voltage switched. In other words it needs to have charge level voltage on its input terminals. There's a small voltage change on lithium, so you may end up with it running 24*7.

Probably better to install a small panel and MPPT to top up the starter independently

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