roger-moss avatar image
roger-moss asked

How to limit charge current from BlueSolar charger?

I have a micro-hydro system and want to charge a 12V lead-acid battery to run the control system (Raspberry Pi, motorised valves etc). This a cheap & simple system, separate from the main Multiplus power delivery system: it maintains a constant turbine rpm and output voltage, provided the load is not excessive.

Most of the time the battery system will deliver about 20W to the control circuitry. Occasionally however I will want to run a Windows PC and other equipment using a 375W inverter and will want the charger to deliver enough current to power this continuously (turbine permitting!). The battery capacity will be about 100Ah.

I am thinking of getting a BlueSolar PWM charger. The alternator output (400Hz 3-phase) will be rectified to give a suitable DC voltage at charger input. Most of the time there will be plenty of power available to run the charger but in dry weather the alternator output will be seriously reduced - perhaps only 30W. How can I ensure the charger does not overload the alternator and stall the turbine?

I suspect there are 3 alternatives:

(a) choose a charger with a control interface (suggestions?).

(b) use an MPPT charger and build a controllable current-limiting circuit (I'm an engineer) to make the MPPT choose a suitable power point

(c) use a pair of chargers, set one to a maximum output of 30W and only use the other when I want to drive bigger loads.

I'm finding it hard to decide which is most sensible. Help appreciated!


BlueSolar PWM
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1 Answer
qcrambes-1 avatar image
qcrambes-1 answered ·


Not sure if I got it right, but you seem to have a Multiplus "main" system somewhere. Have you thought about using the trickle charge function? It is initially made to maintain a starter battery but if you are not using your PC 24/7 it should be enough in you case

Be careful, it seems you will need to have a common ground (from reading posts here and there, I never did it myself) for it to work

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