Now we know - or do we?

At about 3:30pm I turned on the battery on the bus. It measured 13.2v so we can safely assume that it’s charged or patially charged resting voltage is 13.2v. Seventeen and a half hours should have allowed the battery sufficient rest time.

What I have not yet done is to charge the battery on a car charger. That’s still to come. I have bags of time to sort out what’s going on. I’m not going to be using the bus til September. I know I should take it for an oil change, clean, lube and new oil gasket. I can do that in August.

I’m still waiting for stuff to arrive in the post. I’ve got MC4 connectors coming and a new watt meter.  The cigarette lighter to Hopkins adaptor seems to be missing. According to the website it reached New York but I’ve not seen it update since. It has until the 18th to arrive so on the 19th I can file it as missing.

Before I start charging my battery with a car charger I want to put the watt meter on it so I have watt meters both sides, run the battery down after dark, let it charge during the day and then run it down in order to compare figures. I want to see what kind of loss is going on between power coming in and going out.

At this point I’m still not 100% sure what’s going on. It’s either a faulty charge controller or a faulty battery. It could be both. To be honest I’m not keen on the cost of replacing either or both. I know it’s going to be between $80 and $180.

In my research on charge controllers I’ve seen a lot of different reviews. The general theme seems to be that the cheap charge controllers have issues. The really crazy thing is that the issues could all have been easily resolved by simple design changes.

As can be seen, there are the terrible two. I have several copies of each of these controllers. The blue one comes in many guises and many different prices. Look at the form factor of both. If the charge controller is under $100 and resembles either of these, it is to be avoided. I’ve seen the bottom one sold as MPPT whereas it is PWM. As said before, the top one works but the software crashes and not only that but it will switch the load off randomly. The bottom one does not switch the load off when the battery is low. Instead it pulses the load in a rather useless manner. It might just as well not have a place to wire the load!

This little gizmo is a voltage converter. It’s supposed to convert any voltage from 9v to 24v to 12v. It’s allegedly a DC-DC converter but it cab’t be. There is no coil. There should be a whopping great big coil. I couldn’t see one initially until I put on my jewelers eyeglass. Then I saw it - that little circular component at the top right. I had been expecting something more solid than this to be honest and something way bigger. It’s not worthwhile for anything I’m doing and is a mere toy. If that converts an amp, I’d be surprised.

As I keep saying - don’t spend anything over $20 on eBay - you never know what you’re going to get or whether it’s going to be worthwhile. For charging the 12v battery to keep my internal fans, lights and USB chargers running, the bad chargers are acceptible but would be better running off a burglar alarm battery.

Looking at the differences between MPPT and PWM charge controllers, I like the fact MPPT controllers get about 30% more out of a solar panel than PWM controllers get. Having said that, how much do I get with my solar panels? Because I put a panel meter on and can switch the panels out of the circuit to the charge controller I can tell you that I’m currently getting 19v from my panels. There are 95W total of panels. If I divide 95 by 19 and multiply by 12 that should give a reasonable approximation of how much power the panels are capable of producing in bright sun. That works out as 60W. Notice how the panels now produce a third less power? In average lighting they will be producing maybe 30 - 45W. So, lets do a quick calculation. At 30W over 8 hours that will be 240wh of power or around 20ah. That would mostly fill a totally empty 35ah battery.

I’ll now plug my door lock back in and turn the desk light on. I have my desk fan, tablet charger, light and door lock on. That’s a draw of 1.22A or 15.7W. This is what I normally have going on when I’m sitting working at my desk in the bus. Under this load I can (assuming the low 30W figure) work for 16 hours before needing to take a break to allow the batteries to charge. In actual fact the normal power usage is considerably less because there’s something called sleep and something else called daylight.

Assuming my door unlocker keeps using 0.02A then That should consume in 24 hours no more than 0.28AH. With the current strange power situation, it should be safe to leave it plugged in. I’d been concerned that the controller would start pulsing current to it which would be the absolute worst for any kind of electronics.

Looking at the barge controllers, an MPPT could probably recover some of the lost wattage with its built-in DC-DC converter. Equally one could just put a DC-DC converter and simply output 15v DC straight from the panels converted from 19v between the panels and the PWM controller. I like go mess with electronics but when I want something that works, I tend to buy it if possible. We did electronics in high-school but at a very basic level. I wanted to get into the more interesting electronics but did not get on well with the teacher or the ultra-geeky electronics students so I never managed to get into that class. The computer class was another matter entirely! I knew more after the first week than the teacher did. In fact that’s what I qualified in, the first time around in college. It didn’t get me anywhere because I didn’t and still refuse to kiss asses to get work. The world should not be a casting couch! It goes against my morals.

Looking at the reviews of charge controllers it’s very hard to differentiate at the low cost level what’s good and what’s bad. It seems as I’ve probably mentioned before to be that the sub $100 controllers can be an iffy proposition. I like the idea of an MPPT controller but am alarmed at the fact somebody had one that caught fire. I like the low cost of the PWM controllers. I’m still stumped though until I receive my new watt meter. I need to be able to record what’s going in and what’s going out, simultaneously. I do know the current controller needs to be replaced from a performance point of view.

Renology has a nice PWM controller that works solely as a charge controller. It does not attempt to cut the power to the load when the battery is critically low. That’s a bit of an annoyance. Looking around there seems to be a low power consumption low voltage cutoff relay. It requires a manual reset but that shouldn’t be a major problem. In fact, a manual reset does alert one to the presence of a problem. Lots of things to think about though the simple thing would be to go for an all-in-one unit.

The more I look at PWM controllers, the more people seem to sell them with various badges. It’s really hard to tell which are the good and which are the bad after having seen several hundred reviews. Pretty much the same with MPPT but at a higher price. It very much seems a case of trying to pin the tail on the donkey.