Pwm controller draining battery ?

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dunkelly

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Still new at the solar stuff and am constantly revisiting my kit , next purchase a 10amp mppt controller . My question is my Chinese pwm appears to take power out of the battery overnight - is that likely ? I was planning to use this controller with a small panel to keep my 12 volt summer house battery / lighting topped up but if it's more of a drain than an input what's the point . Anyone know what current these pwm things draw when not charging ?
 
Depends on the controller. I have a really cheap controller as a backup and have used it when one of my expensive ones blew a chip. It doesn't have any of the functions claimed (i.e monitoring Ah etc.). I could edit settings to get good charging, almost as good as my other controllers it really sunny weather when less advantage from MPPT vs. PWM.

My cheapo eBay controller claims to draw about 10mA. I think it allows me to leave a load connected overnight but I don't have anything wired to those connections. I think it would also drain if I connected something to the USB connectors overnight (Can't remember if these can be turned off overnight. Diodes prevent the battery feeding the panels overnight.

Bottom line with my spare unit: 10mA 24 x 7 as long as I don't choose to pull power from load or USB connectors. Probably about 1Ah coming out of the battery over 7 days, assuming no drain during daylight hours.
 
dunkelly said:
Still new at the solar stuff and am constantly revisiting my kit , next purchase a 10amp mppt controller . My question is my Chinese pwm appears to take power out of the battery overnight - is that likely ? I was planning to use this controller with a small panel to keep my 12 volt summer house battery / lighting topped up but if it's more of a drain than an input what's the point . Anyone know what current these pwm things draw when not charging ?
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The specification should tell you what drain there will be on the battery .
 
I've got a cheapo pwm controller and a small 30W panel. During spring/summer autumn it will top up my batteries between weekends away. During winter, boat ashore, and panel under cover it will drain the batteries. I just pull the fuse for the winter.
 
Mistroma said:
The figures may well be legible and you might see it written as self consume 10mA (自耗 10mA or possibly 消耗 10mA ).

Might be worth a look or post a picture of the unit in case someone recognises it and has an English manual.
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Thanks I'll go to the boat next wknd and have another look
 
dunkelly said:
Thanks I'll go to the boat next wknd and have another look
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I had a look on eBay and checked several that looked the same as my cheap spare unit. They all said either 10mA or under 10mA for power consumption.

I'm talking about ones like this one 10A 20A 30A Solar Panel Battery Charge Controller 12V/24V LCD Regulator Dual USB | eBay

It says "Self consume: ≤10mA". I wouldn't be surprised if total power out over 7 nights would be under 1Ah for most similar units.
 
For Op with a small solar panel and regular sized battery no controller needed. Just make sure there is a diode between solar panel and battery. (wisdom suggests this although I have never measured any night time leakage without a diode. Like this Diode 1N5822 Schottky 40V 3A DO-27 | Jaycar Electronics
Wisdom says less than 10w solar and more than 50AH battery no need for controller. My opinion is even larger panel OK without controller. if you anticipate a larger solar panel at some stage then I would suggest the smallest Victron MPPT controller. ol'will
 
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