Yens Buyse avatar image
Yens Buyse asked

Phoenix combi 12/1600/75 with 200Ah battery

Hey everyone,

I recently acquired a Phoenix Combi (for a good deal) 12V / 1600W / 75A inverter and charger for my boat . After going through the user manual, I noticed that the manufacturer recommends using a 300-600Ah battery with this unit. However, I believe that a 300Ah battery would be overkill for my intended usage.

I plan to use the inverter for basic power needs on my boat, such as running some lights, charging small electronics, and possibly a small refrigerator. A 200Ah battery seems more suitable for my requirements and would also be a more cost-effective option for me.

My question is, would using a 200Ah battery instead of the recommended 300-600Ah battery cause any issues with the inverter's performance or potential battery damage? (overcharging) I want to ensure that I have a reliable power setup without overspending on an unnecessarily large battery.

screenshot-2023-06-08-at-000527.pngI understand that using a smaller capacity battery may result in shorter runtime, but as long as it can handle my modest power demands, I would be satisfied. I want to make sure I'm not overlooking any potential problems or safety concerns by deviating from the manufacturer's recommendations.

Has anyone had experience using a lower capacity battery with a similar inverter/charger setup? Any advice, insights, or recommendations would be greatly appreciated.

Thank you in advance for your help!

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

"for a good deal" - I hope you got it for free.

That device is 20 years or older.

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Yens Buyse avatar image Yens Buyse Matthias Lange - DE ♦ commented ·
As a matter in fact it was free :)
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1 Answer
matt1309 avatar image
matt1309 answered ·

Hi @Yens Buyse

As long as you setup the correct limits I imagine this is fine to do however i dont have personal experience trying it.

The one consideration I would flag is the current draw on the battery may be too much depending on chemistry/battery you buy. Should be easily overcome by limiting the inverter output power (not familiar with phoenix but imagine that's possible). Although 75a is less <0.5C it may be worth checking what peak output of the inverter is an limiting that according to protect battery.

Similarly for charging, check the C rating of the battery however if it can handle those c rates then should be ok. Might just have faster degradation if charging at higher rates.

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Yens Buyse avatar image Yens Buyse commented ·
Hi @matt1309,

Thank you for your response, I have checked the manual and it looks like it is not possible to limit the 75A continuous charging current. Due to this we are very limited in the batterie we can possibly use and unfortunately are forced to use a higher capacity battery :/

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matt1309 avatar image matt1309 Yens Buyse commented ·

75a was just an example.

The max the battery can handle will depend on the battery you have. For example a Lifepo4 battery could easily manage 0.5c (100amp output for 200ah battery) and I think most LiFePO4 are rated for 1c discharge (which would be 200amps if a 200ah battery). Not sure if the inverter supports Lifepo4, can someone else confirm? I can see you can adjust dip switches for float voltages but unsure if lifepo4 voltages are possible.

I've had a quick look in the manual. I might be wrong but I think you can limit the input current, which will reduce the charging of the battery (page 31).

I think there's also a remote controller you can buy to limit it also.

For discharge protection a solid bms with lifepo4 battery might be enough if no other settings available in phoenix

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