Charge controllers are rated by the number of amps they can process to the batteries. In our case, we have 240 watts of solar panels that produce about 15.0 amps under ideal conditions.
So we would need a charge controller rated at least 20 amps. The most common ratings are 10, 20, 30, 45, and 60 amp versions.
The charge controller we have been using for the last eight years is a 30 amp controller. This time, we also chose a 30 amp controller over the 20 amp version. One of the reasons we did that is that solar panels have come way down in price, and given the right opportunity you never know when we might find a good enough deal to warrant adding another panel to our system. Plus, in this situation the new 30 amp controller was only a couple of dollars more than the 20 amp version.
There are also two different types of charge controllers available. A PWM (pulse width modulation) and a MPPT (maximum power point tracking). The PWM version is more basic and less expensive than the MPPT version, while the MPPT version makes better use of the available voltage coming from the panels. MPPT units can be as much as 30% more efficient, but in a smaller system like ours that benefit might only be 10%.
So I didn't see the value in spending more than twice as much to get a 10% gain.
Our new charge controller... $30 USD on eBay.
We have Trojan brand batteries, model number T-105. These are popular, quality wet cell batteries that are used by a lot of RVers.
Trojan specifications recommend that the bulk charging voltage for these batteries is 14.82 volts.
The problem is, that many charge controllers have set charge parameters that don't allow the batteries to be charged at this rate.
Many charge controllers also don't have the ability to do an "equalization" charge at 16.2 volts. This equalization charge reduces battery sulfation (the formation of crystals on the plates) which is the leading cause of battery failure. Trojan recommends performing an equalization charge on fully charged batteries once every 30 days.
Our (now 8 years) old Trojan batteries have NEVER been charged at 14.82 volts. And they have NEVER been equalized.
So I wanted a charge controller that would perform at these levels. The new charge controller that we have bought is fully adjustable!
Oh, there are some charge controllers that do have this ability... but they typically cost between $100 and $400 dollars!
Did I mention that this little Chinese controller was only $30?
Now, some would say "Yeah, but that's cheap Chinese junk..."
But our friend Doug is an electrical engineer, and I trust his judgement. Also, he has used this controller in the past and has had good success with it. And, if you do some research, you can find a lot of good reviews on this particular unit. So for $30, it's worth a try.
Our old charge controller never charged the batteries at higher than 14.0 volts before dropping back to a float charge of 13.5. So I don't think that our old batteries have EVER been fully charged. Now, perhaps the fact that they've also never been OVERcharged is one of the things that has led to their longevity. But, we've also never had the benefit of their full use.
So, it will be an interesting experiment this fall to see if charging to the proper parameters will give new life to our tired batteries. Like I have said in previous posts, we will likely buy new ones prior to entering Mexico, but I'm curious anyhow. And, the new ones will now be charged properly!
--------------------------------------------------------------------------------------------------------------------------
Great deal on a 12.5 foot telescoping ladder...
Lifewit 12.5ft EN131 Telescoping Aluminum Extension Multi Purpose Ladder
And in Canada, this 4 in 1 portable air conditioner is on sale and gets great reviews...
Delonghi 13000 BTU 4-in-1 Portable Air Conditioner with Heat Pump
Thank you for that very informative post. I love to hear the "why" as much as what you chose to go with. Hope you can reach that magic equalization number.
ReplyDeleteWe hope that you found the information useful.
DeleteKevin is all excited to get this installed and then be able to play with it.
Good idea for a good charge controller, ours is a Blue sky controller and was set up to charge our batteries, to 14.8 volts and does a wonderful job. But now we need to add distilled water every month or so. Sure will make a difference with your battery life, our trojan T-105's are 8 years old as well and doing fine. No problem hope it works well for you.
ReplyDeleteRight, and I had mentioned that many of the more expensive units are also programmable. And in fact, I had looked at buying a $169 Blue Sky unit similar to yours, but couldn't justify the price when I could get something to do the same job for a whole lot less money.
DeleteSo much to know about solar power, I can easily see you guys in an off grid plot somewhere in Mexico in about 10-15 years
ReplyDeleteWe have often said that if we ever settle down somewhere it will be with solar panels and batteries.
DeleteWell, I am completely confused now! Electrics has never been a strong point for me. I just don't get it. I hope this gadjet will do for you what you expect from it.
ReplyDeleteSolar and batteries can definitely be a bit confusing especially if you haven't worked with them before. Kevin has done lots of research on them and on learning how it all works but he is still always learning new information on them. I guess if you don't ever think you will use solar power then you don't really have to figure it all out. :-)
DeleteIf your friend brought you one up from the states, that's a plus but for 60 bucks he could have picked you up a MPPT unit
ReplyDeleteWith CD An a lot less than a blue Star
As you know your PWM is only rated at 80% efficiency
you're in MPPT unit is rated for 99% why not grab the other 19%
I've read a lot of articles that state that an MPPT controller might be between 10% to 30% more efficient than my PWM unit. The 10% figure would more likely apply to my small setup. I simply don't have the need to spend the difference.
DeleteIt will be interesting to see what the new controller does with your batteries when you hook it up.
ReplyDeleteI will make sure to do a full report!
DeleteWe're running a 60 amp system with AGM batteries. We'll probably be adding to it later.
ReplyDeleteCanadian Tire presently has a Two Pack of 100 Watt panels on sale for about what we paid in the US figuring Taxes and Exchange. Something to think about.
Be Safe and Enjoy!
It's about time.
We definitely don't need another 200 watts, but that is not a bad deal at Canadian Tire for $350 considering Canadian prices. Having said that, you can regularly buy a single 100 watt panel on Amazon.ca for $160 and not have to pay provincial sales tax in a lot of cases depending on which province you're in.
Delete100 watt panel at Amazon.ca
I'll be interested to see how this controller works for you. Does it do bulk absorption and float? We got a new MPPT controller a few months ago (SolarBoost 3000i which cost about $100). Scott just adjusted the parameters on our controller (we have the same batteries) and we're seeing how that works out. We're planning on replacing our battery bank this year too.
ReplyDeleteI'd be curious as to where you got that SolarBoost 3000i for "about $100"...?
DeleteWe already had the 2000 which was malfunctioning and the company (Blue Sky) offered one to us at a reduced rate. They were fantastic to work with. Great customer service and support.
DeleteAh, well you didn't mention that!
DeleteYes, my $30 controller is fully programmable and has both bulk and float charge. Not surprised to see that Blue Sky controllers aren't bulletproof. You'd think for that kind of money they would be, but I guess you're paying for the great customer service and support. I don't expect that from the company that makes my $30 one.