Solar voltage help...

If it will let you, you can adjust float voltage to be the same as absorption voltage so it stays there the rest of the day after reaching Vabs, say mid-afternoon. V falls back overnight anyway.

Not for storage, of course.

I want an adjustable voltage cheapo, so I ordered a Solar30 as mentioned by Niner a while back. My "RJ special" works well, but peaks at 14.4v and I want the PWM controller to have the same Vabs I set on my MPPT controller, 14.8, so they will work together on the one battery bank. Last time, I had two banks so one on each would be ok. If the voltages can't be matched, I can always go back to split bank operation for the summer.

When it gets here I will report on just what voltages you can pick. (manual doesn't say how high you can crank it, at least I don't see that.)

http://www.chinasolarregulator.com/user-manual/solar30.pdf

Almot wrote:

NinerBikes wrote:

If you buy a $12 pwm charge controller like this on ebay ... Adjustable V + - 0.9V for bulk and float modes.

you can then choose your set points based on battery types.

I've always considered myself being cheap, but this is more of a gamble - even though you only bet $12 :)...
I don't see where it says "adjustable" - but maybe, who knows. Still a gamble.

I found one for about $10 a while back, spent the money, and I've tested and verified that it, indeed, does just what it claims. It's even adjustable charge for different types of batteries. Open vent, AGM or VRLA, gel, etc, etc. It indeed has a pulse charge, the voltage bounces around, then once it hits that peak voltage in bulk mode, it kicks in to around 13.4V maintenance. You can, of course, also adjust the maintenance charge voltage also, should you so desire.

NinerBikes wrote:

If you buy a $12 pwm charge controller like this on ebay ... Adjustable V + - 0.9V for bulk and float modes.

you can then choose your set points based on battery types.

I've always considered myself being cheap, but this is more of a gamble - even though you only bet $12 :)...
I don't see where it says "adjustable" - but maybe, who knows. Still a gamble.

Mine is wired the same way. If you look in the manual, it shows not to connect short cables without the long cable. A more expensive connector that prevents polarity issues would be better, but alas.

I had the opportunity to try mine out today in lovely overcast conditions. I measured about 14v at the batteries - less if I covered the panels. Unfortunately we aren't supposed to see sun for a few more weeks :(.

They are all wired that wsy. The manual says to use the extension only.

I have the 100 W version of these portable panels. I found a problem with the cabling provided with the panels. If you use the long extention cable between the short alligator clip battery cable and the controller output cable there is no problem. However, if you omit the long cable and connect the short cable directly to the controller output cable there is a polarity reversal - red to black and black to red at the connector junction. Fortunately I noticed this problem before I hooked up to the battery with reversed polarity. I don't know if mine was a unique case or whether they're all wired that way. I changed all the connectors to Andersen Power Poles so that won't be a problem in the future.

Almot wrote:

Captain Obvious wrote:
In looking at it and reading through the engrish manual - it looks like it just dumps solar voltage onto the battery off and on until the battery looks charged around 14v, and then it stops dumping voltage until the battery voltage drops again. It's not a PWM and definitely not an MPPT charger.

They never put MPPT in those kits. And you wouldn't like el-cheapo MPPT if they did.

Even the most epxensive PWM works pretty much the same: voltage goes to pre-set point of 14-something (called Bulk), stays there for an hour, and then it tapers the current to let the voltage drop to 13-something (called Float). The biggest drawback of el-cheapo PWM I see in their inability to adjust those Bulk and Float setpoints - important because every battery has different setpoints, and also in lack of temperature compensation. Lead is getting more and more expensive, as all raw materials, so taking good care of your batteries makes sense. Low-current PWM with adjustable setpoints and temp-comp are not terribly expensive.

If you buy a $12 pwm charge controller like this on ebay ... Adjustable V + - 0.9V for bulk and float modes.

you can then choose your set points based on battery types. Anyone, before buying one of these units, should tie a watt meter charge controller, preferably a RC battery charger model, in line to see what actual voltage and amps are.

RC boat helicopter Watt/ Amp / volt meter for charging.

I can assure you, once you start paying attention to what this unit meters, as I have, you'll know for certain that even the stock PWM on that portable unit does indeed pulse charge at different volts and amps, constantly, in bulk mode.


A basic replacement model, if your original charge controller goes bad.

solar charge controller for Solar BLVD 120-160 watt panels.

Captain Obvious wrote:
In looking at it and reading through the engrish manual - it looks like it just dumps solar voltage onto the battery off and on until the battery looks charged around 14v, and then it stops dumping voltage until the battery voltage drops again. It's not a PWM and definitely not an MPPT charger.

They never put MPPT in those kits. And you wouldn't like el-cheapo MPPT if they did.

Even the most epxensive PWM works pretty much the same: voltage goes to pre-set point of 14-something (called Bulk), stays there for an hour, and then it tapers the current to let the voltage drop to 13-something (called Float). The biggest drawback of el-cheapo PWM I see in their inability to adjust those Bulk and Float setpoints - important because every battery has different setpoints, and also in lack of temperature compensation. Lead is getting more and more expensive, as all raw materials, so taking good care of your batteries makes sense. Low-current PWM with adjustable setpoints and temp-comp are not terribly expensive.

Captain Obvious wrote:
I just bought that same kit! From the same place!
It's been raining, so I haven't been able to try mine out yet.
I bought the kit knowing I would probably end up replacing the controller at some point with a better one. I also plan to rewire it so that the controller is closer to the batteries.

In looking at it and reading through the engrish manual - it looks like it just dumps solar voltage onto the battery off and on until the battery looks charged around 14v, and then it stops dumping voltage until the battery voltage drops again. It's not a PWM and definitely not an MPPT charger.

I'm curious how your replacement goes.

Once you understand the lights and the blinking pattern on the back of the charge controller, it's really easy to determine the state of charge.

I have the 120 watt version, same controller. It charges at 14.4V until the PWM inside reaches that level while charging at the terminals, then it drops the amps and the voltage down to about 13.6-13.7V. I run the charger while the battery is still attached and getting a draw from my travel trailer, so I've never seen it get to a float voltage, yet. I will sometimes peak at 6.63 amps during charging, but this has been during winter or late fall. You should see a 160/120 factor over what I am seeing for max amps, if your battery is deeply discharged at 40 to 50% SOC and the sun is high up when you START charging. Figure about 8.8 to 9 amps, after the controller. The 3 red lights should either be solid, or have the most difficult and minor flickering occurring to indicate a full charge. Or, you are getting around 12.7 to 12.75V at the battery terminals. Or the specific gravity of your cells is around 1.270 to 1.280 on a hydrometer.

The stock controller is more than adequate. What you should do once every 7 to 10 days, though, is disconnect the batteries from the camper, then bypass the charge controller and wire the panels direct to the battery, and measure the voltage at the batteries. When you see 16.0V at the battery, rewire the solar panel again, back through the charge controller, and put it back to a max of 14.4 V, then reconnect the camper to the batteries. This is for desulfating the battery. It needs to be done every 7 days during heavy discharge /charge cycles, to get the battery fully charged back to 100% state of charge.

I just bought that same kit! From the same place!
It's been raining, so I haven't been able to try mine out yet.
I bought the kit knowing I would probably end up replacing the controller at some point with a better one. I also plan to rewire it so that the controller is closer to the batteries.

In looking at it and reading through the engrish manual - it looks like it just dumps solar voltage onto the battery off and on until the battery looks charged around 14v, and then it stops dumping voltage until the battery voltage drops again. It's not a PWM and definitely not an MPPT charger.

I'm curious how your replacement goes.