According to what I've read, a 12v battery tops out at 12.8V and is discharged to 40% of its capacity by 11.9V. Going below that 40% apparently risks damaging the battery and thus shortening its life. My two latest charge controllers will not let me protect my battery. Their cut off cannot be raised to 11.9V. Their cut off can be set only between 9V and 11.3V. A battery is 100% depleted by 10.5V. Those Chinese charge controllers are designed to destroy batteries - probably so the Chinese can sell more batteries!
The purpose of a charge controller is fourfold.
- It protects the battery from overcharge (an overvoltage cutoff switch)
- It protects the battery from overuse (a low voltage cutoff switch)
- It provides for a threshold voltage that cuts power back on.
- It protects the solar panels from the battery (a diode)
All my solar charge controllers claim to have "different charging algorithms" for different kinds of battery. Those claims are totally vacuous in my opinion. Electricity is often compared to water in most electrical textbooks and my question is... how many different ways are there to fill a bucket with water? Water goes in, reaches the top. Done!
I can honestly say I am distinctly unimpressed by the claims of these charge controllers. I'm thinking very much of just ditching charge controllers and going over to a simpler system. All my solar panels are double diode protected. They really should be fuse protected too. That eliminates one part of the charge controller system.
There are undervoltage cut off switches, voltage trigger switches, over voltage cut off switches and diodes. Individually these are probably more costly and take up more space but they might be the way to go, considering these Chinese charge controllers are just so bloody hopeless. So many of these Chinese products are built as though they're middle school science projects, slapped into a pretty case and given Google auto translated instructions that are printed in minuscule text on paper everybody else would wrap around fish and chips.
Looking around I see exactly the same charge controllers - same form factor, different colors being sold by different companies at wildly different prices. I've seen the same thing going on eBay for $10 that has been in Walmart for $20, Home Depot for $50 and Harbor Freight for $80. Then I see charge controllers being sold for upwards of $1,000 in other places. Add in to that the fact you never really know the background of anything and it becomes almost impossible to know whether you're buying a Chinese lemon or an American star. I dare say it took the Chinese 50 years after everybody else to develop a space program because of their lousy attitude to quality.
So, thinking forward, if the charge controller that's supposed to arrive from California on Friday actually works, my next purchase will be a timer. That way I can set my extraction fan to go for precisely 15 minutes every hour. I already have a thermal switch on it so that it won't run in under 25C (77F). I might further add a low voltage cutout switch.
In fact, with the low voltage cutout, a timer and an over voltage cutout, aside from diodes on the solar panels, there would seem no point whatsoever in having a charge controller. Timers seem to go for about $10, low voltage cutouts for about $40 and over voltage cutouts for about the same. For my purposes, with my diode protected panels, all I really need is to protect the batteries from low voltage and put a timer of my extraction fan. Over voltage with 35W of solar power and (when I get my CPU fans wired into the curcuits) 10W of ventilation plus 30W of extraction fan is most likely not going to be a problem. Having said that, it's always worth putting in overvoltage protection.
Meanwhile, I set to and adjusted my charge controller settings on the extraction fan. I figured that the battery was probably already gone so dropping the cutoff voltage from 11.9 to 11.5v wouldn't do any more damage. I'd read on one of those authoritative battery websites that one should never discharge a battery below 11.9v as it would damage the battery. Discharged to 10.5v and the battery would be dead instantly. Not expecting much from it, I initially connected to my 7ah battery and found the extraction fan worked for quite a while before cutting off and recharging after which it worked for quite a while again. Mystified I disconnected the 7ah battery and reconnected my 10ah and left it going. It charged and discharged a couple of times with impressively long fan operation times. I'll have to see how long it keeps going like that.
Then I got on and glued more of my lightweight cable from my circulation fan to the wall and then joined it to a heavier cable that leads to my front charge controller. The fine cable was flimsy enough that a terminal block connection didn't work. The wire snapped off as soon as the screws were tightened. Thus I soldered the connection and put shrink on insulation sleeves. How I wish I'd discovered those 40 years ago! The cable was glued into place and passed through a hole in the partition. I connected it to the charge controller using spade terminals.
Setting the fan going took a few minutes and I had to read the charge controller manual. It was in the usual Chinese gibberish. Alas that charge controller is set to 11.3v cutoff voltage. Now it could be that the website that I obtained my charge level information was written by some joker that had a hidden agenda or he could have been a complete cretin. Equally, he could have been dead right. Only time will tell. I neglected to include a thermal sensor in my fan setup. I will have to add that later.
I'm hoping and praying that my small batteries last a while like this. Not least because if they die, I'll have to replace all my charge controllers. I do intend to switch over to my bigger battery but the plans I have for that also involve adding an external solar or wind power input, putting the battery (which is fairly bulky) under the bus in a custom built cradle. For that I'll probably have to get my welder out of storage and (carefully) weld some of the leftover steel angle to form a cage that can be bolted to the C section members underneath the bus. At the same time I'll put an extra cable from front to back to carry the solar charge to the front where it will be shared between all my devices and a cable from the extraction fan to the front. I'll also include a connection for a fan above my bedroom desk. Then I might include some USB power ports. Needless to say, having the extraction fan on for more than 10-15 minutes is costly in electricity and most likely entirely unnecessary. One complete change of air every hour should be plenty! For that I might need to obtain a timer.
Despite the fact I come across unforeseen issues and problems, I do master them. This bus project has been a series of problems, solutions, frustrations, frequent cursing and I am eternally glad that I have been able to do it. My dad brought me up around tools and showed me how to use many. I wish that my woodwork was better. My dad, of course, was brought up by a multi-skilled father whose claim to fame was that he was a ship's carpenter for some of his life. Sadly, he passed away before I arrived on the scene. I can well imagine his tut-tutting over my carpentry skills! I'm keen to try my bus out on a short camping trip. I'll probably do that after it's retitled and the new insurance is sorted out.
At the moment I'm waiting on Walmart to provide the prints I ordered. They should come in on Friday. Those prints will go together with my $15 dollars and my completed application to retitle my bus as a motorhome pretty quickly. It took the DMV a month to respond last time. This time, I hope they're far speedier. Mind, this time I'm surer of my situation. The bus has been improved substantially and I have a bus driving license now as well as more driving confidence as a consequence.
It seems the biggest thing I did in order to reduce the heat in the bus was to paint the roof white. I have a feeling my CPU fans though slower were probably better value as extraction fans than my big bilge blower. I have a feeling my idea of having CPU fans as circulation fans is probably a good idea. The $5 window screen from Lowes (hiss, spit) isn't as good as the powered screen I built but stays in the windows earlier and wedging the window onto the screen with a 1 inch nut was a stroke of genius. School bus windows were not built to be very adjustable! There's no way, without air conditioning that I'm going to be able to get the temperature inside the bus much lower. Sure, there are elastometric coatings one can paint on the roof - the best example being Kool Seal which they put on the rooves of mobile homes. It's quite expensive and doesn't make enough difference over a gallon of ordinary white paint to be, in my opinion, worthwhile. The best defense against heat is to park in the shade.
Returning to my door alarm, I managed to put it in place so that it operates. From the front of the bus with both the fans going, I can't hear it but it'll surely scare the socks off any bad guy that tries to break in. The side door is more of a challenge as it has a wide rubber gasket.
At work I spoke with a painter whose comment about the paint peeling in patches on the bus was to scrape it off where it peeled then to do pretty much what I am. Where it peels I'm cleaning it and spraying with a self-etching primer then spraying with my usual paint. It means a little work every now and then but that's not a problem.
The latest on my extraction fan is I lowered the maximum charge to 12.9v as for some reason it wasn't reaching 13v and raised the minimum charge to 11.6v as the fan had been running for about 20 minutes. That's quite acceptable. As I said though, I feel CPU fans were a better choice as they ran pretty well constantly in the summer. They were very quiet and though they didn't shift quite as much air, I find that removing hot air doesn't help all that much. I thought it would. The fan setup doesn't half look impressive though!
At the end of the day I was thwarted. I'd started to build another fan assembley like the one in the galley but due to the partition in the bedroom being a different design, the fan assembley needed some extra tweaks. I used a 5/16 rivet on one end of one cross bar. That was fine - the other end and where the cross bar joins will be screwed to the woodwork. My problem was that though I know I have a full packet of 5/16 aluminum rivets I could not find them. Mind, having sweltered for most of the day in 93F while I both blogged and worked on the bus, I was in no mood by 7PM to go to hunt for them. That's a job for tomorrow. Once the next cross bar is secured, the new cross bar can be trimmed with my angle grinder and the overly long bottom bars of my fan holder can also be trimmed. Then it'll be a case of putting it up and waiting for cold weather to install the underbody wiring and to pass the wires through the floor to the new wire run.
I did have a crazy thought based along the lines of putting an LED rope light down the center of the aisle, attached to the ceiling. That could hide extra wires! Then I realized how crazy that idea was because my experience of LED lighting has been poor. This is precisely why I went for replaceable lanterns for my lighting.
Well, today has been one of rapidly changing opinions. I'd been totally dissatisfied with the Chinese battery control units and the batteries I'd bought. Then suddenly it all started to work. I end the day with reservations as to how long that setup will work but the prof of the pudding being the eating, I'll have to wait and see. I was very impressed by my USB circulation fan. I believe I will be equally impressed by the one in the bedroom when I get it installed and working. Once that is done, aside from the underbody stuff and making the battery cradle, I'm pretty much done. Or rather, done until I get another idea...
Looking around I see exactly the same charge controllers - same form factor, different colors being sold by different companies at wildly different prices. I've seen the same thing going on eBay for $10 that has been in Walmart for $20, Home Depot for $50 and Harbor Freight for $80. Then I see charge controllers being sold for upwards of $1,000 in other places. Add in to that the fact you never really know the background of anything and it becomes almost impossible to know whether you're buying a Chinese lemon or an American star. I dare say it took the Chinese 50 years after everybody else to develop a space program because of their lousy attitude to quality.
So, thinking forward, if the charge controller that's supposed to arrive from California on Friday actually works, my next purchase will be a timer. That way I can set my extraction fan to go for precisely 15 minutes every hour. I already have a thermal switch on it so that it won't run in under 25C (77F). I might further add a low voltage cutout switch.
In fact, with the low voltage cutout, a timer and an over voltage cutout, aside from diodes on the solar panels, there would seem no point whatsoever in having a charge controller. Timers seem to go for about $10, low voltage cutouts for about $40 and over voltage cutouts for about the same. For my purposes, with my diode protected panels, all I really need is to protect the batteries from low voltage and put a timer of my extraction fan. Over voltage with 35W of solar power and (when I get my CPU fans wired into the curcuits) 10W of ventilation plus 30W of extraction fan is most likely not going to be a problem. Having said that, it's always worth putting in overvoltage protection.
Meanwhile, I set to and adjusted my charge controller settings on the extraction fan. I figured that the battery was probably already gone so dropping the cutoff voltage from 11.9 to 11.5v wouldn't do any more damage. I'd read on one of those authoritative battery websites that one should never discharge a battery below 11.9v as it would damage the battery. Discharged to 10.5v and the battery would be dead instantly. Not expecting much from it, I initially connected to my 7ah battery and found the extraction fan worked for quite a while before cutting off and recharging after which it worked for quite a while again. Mystified I disconnected the 7ah battery and reconnected my 10ah and left it going. It charged and discharged a couple of times with impressively long fan operation times. I'll have to see how long it keeps going like that.
Then I got on and glued more of my lightweight cable from my circulation fan to the wall and then joined it to a heavier cable that leads to my front charge controller. The fine cable was flimsy enough that a terminal block connection didn't work. The wire snapped off as soon as the screws were tightened. Thus I soldered the connection and put shrink on insulation sleeves. How I wish I'd discovered those 40 years ago! The cable was glued into place and passed through a hole in the partition. I connected it to the charge controller using spade terminals.
Setting the fan going took a few minutes and I had to read the charge controller manual. It was in the usual Chinese gibberish. Alas that charge controller is set to 11.3v cutoff voltage. Now it could be that the website that I obtained my charge level information was written by some joker that had a hidden agenda or he could have been a complete cretin. Equally, he could have been dead right. Only time will tell. I neglected to include a thermal sensor in my fan setup. I will have to add that later.
Despite the fact I come across unforeseen issues and problems, I do master them. This bus project has been a series of problems, solutions, frustrations, frequent cursing and I am eternally glad that I have been able to do it. My dad brought me up around tools and showed me how to use many. I wish that my woodwork was better. My dad, of course, was brought up by a multi-skilled father whose claim to fame was that he was a ship's carpenter for some of his life. Sadly, he passed away before I arrived on the scene. I can well imagine his tut-tutting over my carpentry skills! I'm keen to try my bus out on a short camping trip. I'll probably do that after it's retitled and the new insurance is sorted out.
At the moment I'm waiting on Walmart to provide the prints I ordered. They should come in on Friday. Those prints will go together with my $15 dollars and my completed application to retitle my bus as a motorhome pretty quickly. It took the DMV a month to respond last time. This time, I hope they're far speedier. Mind, this time I'm surer of my situation. The bus has been improved substantially and I have a bus driving license now as well as more driving confidence as a consequence.
It seems the biggest thing I did in order to reduce the heat in the bus was to paint the roof white. I have a feeling my CPU fans though slower were probably better value as extraction fans than my big bilge blower. I have a feeling my idea of having CPU fans as circulation fans is probably a good idea. The $5 window screen from Lowes (hiss, spit) isn't as good as the powered screen I built but stays in the windows earlier and wedging the window onto the screen with a 1 inch nut was a stroke of genius. School bus windows were not built to be very adjustable! There's no way, without air conditioning that I'm going to be able to get the temperature inside the bus much lower. Sure, there are elastometric coatings one can paint on the roof - the best example being Kool Seal which they put on the rooves of mobile homes. It's quite expensive and doesn't make enough difference over a gallon of ordinary white paint to be, in my opinion, worthwhile. The best defense against heat is to park in the shade.
Returning to my door alarm, I managed to put it in place so that it operates. From the front of the bus with both the fans going, I can't hear it but it'll surely scare the socks off any bad guy that tries to break in. The side door is more of a challenge as it has a wide rubber gasket.
At work I spoke with a painter whose comment about the paint peeling in patches on the bus was to scrape it off where it peeled then to do pretty much what I am. Where it peels I'm cleaning it and spraying with a self-etching primer then spraying with my usual paint. It means a little work every now and then but that's not a problem.
The latest on my extraction fan is I lowered the maximum charge to 12.9v as for some reason it wasn't reaching 13v and raised the minimum charge to 11.6v as the fan had been running for about 20 minutes. That's quite acceptable. As I said though, I feel CPU fans were a better choice as they ran pretty well constantly in the summer. They were very quiet and though they didn't shift quite as much air, I find that removing hot air doesn't help all that much. I thought it would. The fan setup doesn't half look impressive though!
I did have a crazy thought based along the lines of putting an LED rope light down the center of the aisle, attached to the ceiling. That could hide extra wires! Then I realized how crazy that idea was because my experience of LED lighting has been poor. This is precisely why I went for replaceable lanterns for my lighting.
Well, today has been one of rapidly changing opinions. I'd been totally dissatisfied with the Chinese battery control units and the batteries I'd bought. Then suddenly it all started to work. I end the day with reservations as to how long that setup will work but the prof of the pudding being the eating, I'll have to wait and see. I was very impressed by my USB circulation fan. I believe I will be equally impressed by the one in the bedroom when I get it installed and working. Once that is done, aside from the underbody stuff and making the battery cradle, I'm pretty much done. Or rather, done until I get another idea...
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