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I currently have a 400 watt solar panel array in series with a Epever 24 volt charge controller connected to two twelve volt battery bank in series (24v) with a 24 volt split inverter.

I'm planning to incorporate a 24 volt 400 watt wind turbine to this same battery bank and it comes with its own charge controller.

Can I connect both charge controllers to the same battery bank?

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    \$\begingroup\$ The chargers could definitely interact with each other and cause strange behavior. \$\endgroup\$ – mkeith Feb 7 '18 at 7:25
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I don't see why not, as long as the batteries can handle the worst case charging conditions (both charge controllers delivering maximum current simultaneously). MPPT charge controllers (and lead acid battery chargers in general) basically act as current sources for the bulk of the charging process, so paralleling them shouldn't have ill effects. Once the battery is nearly full, one might switch to constant voltage and later float charging before the other, but this shouldn't cause any issues.

Epever seems to agree with this. Page 8 of user manual:

2 Installation Instructions

2.1 General Installation Notes

...

  • Multiple same models of controllers can be installed in parallel on the same battery bank to achieve higher charging current. Each controller must have its own solar module(s).

Another manufacturer even has a whole article about this: https://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/

While the wind turbine charge controller is clearly not of the same model, I see no reason why they wouldn't play nice together. Epever probably added that distinction because they can't guarantee that their product works when in parallel with every device on the marked.

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There's no problem with the physics of adding two current sources together to charge a single battery. The problem might come with the control.

Battery chargers tend to be programmed to
a) charge the battery as quickly as possible
b) not overcharge the battery

It's easy for two parallel chargers to each limit the voltage to the battery. They will have slightly different thresholds, but that really doesn't matter.

The problem comes with current. Perhaps the safest way to parallel two chargers is to allocate each charger 50% of your battery's maximum charge current (or 30/70, or some other fixed fraction). Unfortnuately with a strong wind at night, or a calm sunny day, the maximum charge rate will be limited by your chargers at below the maximum possible for the battery.

Ideally you'd like either charger to charge up to the maximum rate of your battery, but limit the total current on a windy sunny day. That means they have to know about each other, and play nice. The feature needs to have been anticipated and included by the controllers' designers.

If they are only standalone chargers, but both have a digital port, and can report current and be controlled on the fly, then you can tack on an Arduino or PI, and control the limits yourself.

If they don't have digital control, you may be able to do something on the analogue side, but you'd need to know what you were doing.

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Surely each charger will monitor the battery and see the other charger as a fully charged battery if their outputs are connected together. If you used diode control to stop the one charger from monitoring the other charger, then they will not monitor the battery either so they surely will both shut down in a fault condition?

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As long as the charging perameters are the same or close to the same.Is see no reason why you cannot run both controllers together.

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