Cheap MPPT controllers- any good?

[Kelpie]

I'm going to install a medium sized solar setup on the boat, thinking roughly in the 50w sort of area, give or take. Enough to keep up with (mainly LED) lighting and working the bilge pump from time to time. No fridge, radar, anchor windlass etc. I stay aboard the boat several nights a week and don't want to have to run the engine to keep up with usage. I have a few leaks around the place so want to stop the auto bilge pump from discharging the batteries after heavy rain as well.

I'm aware that MPPT controllers are the bee's knees, but the prices seem to vary massively. For example, for under a tenner you can get one of these: http://www.ebay.co.uk/itm/New-30-20...195574?pt=UK_Gadgets&var=&hash=item19f053a376
which is advertised as being MPPT, but is this too cheap to really bother with? If it's any good, why are people paying ten times that for a controller?

I've also heard that some controllers can act as a battery monitor as well, which I like the sound of. Any recommendations?

 

[vyv_cox]

I realise that plenty of knowledgeable people on here advocate MPPT controllers but it's odd that none of the providers of controllers for marine and motorhome use seem to recommend them. There is a useful explanation of the reasons for this at https://www.sunware.de/sunware/technik/systeme

I have had two PWM controllers, one many years ago from Fox, https://www.sunware.de/sunware/produkte/regler and now one from Sunworks, http://www.sunworks.co.uk/ in fact the one that is illustrated on their home page. There is also one in my motorhome, don't know its manufacturer at present. All work perfectly well and are designed for the type of use I give them. My Sunworks one is for two battery banks, switches between them as demanded by their charge level and displays voltage of each bank and the current being delivered.

 

[VicS]

I'm going to install a medium sized solar setup on the boat, thinking roughly in the 50w sort of area, give or take. Enough to keep up with (mainly LED) lighting and working the bilge pump from time to time. No fridge, radar, anchor windlass etc. I stay aboard the boat several nights a week and don't want to have to run the engine to keep up with usage. I have a few leaks around the place so want to stop the auto bilge pump from discharging the batteries after heavy rain as well.

I'm aware that MPPT controllers are the bee's knees, but the prices seem to vary massively. For example, for under a tenner you can get one of these: http://www.ebay.co.uk/itm/New-30-20...195574?pt=UK_Gadgets&var=&hash=item19f053a376
which is advertised as being MPPT, but is this too cheap to really bother with? If it's any good, why are people paying ten times that for a controller?

I've also heard that some controllers can act as a battery monitor as well, which I like the sound of. Any recommendations?

This one has cropped up in discussions before. I think you will find that it is a PWM controller not an MPPT controller as advertised by e bay sellers

 

[ghostlymoron]

I've concluded that MPPT controllers are not worth the extra money for my sort of useage. Spend the money on extra wattage of panels if it's burning a hole in your pocket. I recently bought a PWM controller from an eBay seller for 7 quid. It keeps my leisure battery nicely topped up and can control streetlamps if I want it to. Seems to be well made and easy to fix/terminate. Only time will tell if it's durable. They should really have got a native English speaker to proof read the instructions though.
This looks similar to mine but the terminals look even better. The street light controls are not as sophisticated. http://www.ebay.co.uk/itm/10A-15A-2...05&prg=10245&rk=2&rkt=6&sd=111406195574&rt=nc Good price! Forgot to add the delivery charge!

 

[VicS]

I've concluded that MPPT controllers are not worth the extra money for my sort of useage. Spend the money on extra wattage of panels if it's burning a hole in your pocket. I recently bought a PWM controller from an eBay seller for 7 quid. It keeps my leisure battery nicely topped up and can control streetlamps if I want it to. Seems to be well made and easy to fix/terminate. Only time will tell if it's durable. They should really have got a native English speaker to proof read the instructions though.
This looks similar to mine but the terminals look even better. The street light controls are not as sophisticated. http://www.ebay.co.uk/itm/10A-15A-2...05&prg=10245&rk=2&rkt=6&sd=111406195574&rt=nc Good price! Forgot to add the delivery charge!

You could use the street light controls to automate your anchor light.

Other types have load control circuits that can be used to disconnect a fridge, for example, if the battery volts fall unacceptably low

 

[TQA]

MPPT controllers become worthwhile if you have panels that deliver higher voltages than the battery wants to see.

Battery max is 15 volts.

Say the panel delivers 20 volts at 3 amps. The MPPT controller converts that to 15 volts but 4 amps. Well nearly 4 amps there are some losses. SO you have a gain of about 30%.

 

[VicS]

MPPT controllers become worthwhile if you have panels that deliver higher voltages than the battery wants to see.

Battery max is 15 volts.

Say the panel delivers 20 volts at 3 amps. The MPPT controller converts that to 15 volts but 4 amps. Well nearly 4 amps there are some losses. SO you have a gain of about 30%.

marginally better than you suggest in theory.

The MPPT controller aims to control the panel at the terminal volts at which its useful power output is at its maximum. Usually around about 16 volts or so, but it should be given in the tech spec for the panel.

 

[oldvarnish]

I've got an MPPT controller by Blue Sea Systems. It has a switch on the front and you can read what the charging current would be with and without the controller.
I always seem to be winning - but winning less when the current is less that 2 amps

 

[pappaecho]

Have got 600 amp battery banks, with a 80 watt solar panel, and a cheapish Maplin controller, which compares two different battery banks, and send charge to the most depleted. It cuts off at 14 volts. A very well made German unit, which I think cost about £10 four years ago. In winter the battery levels fall to about 12.7 volts but in summer tend to be at cutoff at 14 volts. Dont know if a MPPt controller would do it better, but the system works faultlessly

 

[VicS]

Have got 600 amp battery banks, with a 80 watt solar panel, and a cheapish Maplin controller, which compares two different battery banks, and send charge to the most depleted. It cuts off at 14 volts. A very well made German unit, which I think cost about £10 four years ago. In winter the battery levels fall to about 12.7 volts but in summer tend to be at cutoff at 14 volts. Dont know if a MPPt controller would do it better, but the system works faultlessly

A PWM controller should keep a battery at a consistently higher state of charge because it reduces the charge rate rather than switching off and allowing the SOC to decay before switching back on. A bit like a charger reducing to a float charge.

The object of an MPPT controller is to get the maximum out of the solar panel.