No pictures or video today... Shock, horror!
A bit more tinkering with charging settings, increasing the float Voltage again to 27.00V (3.375Vpc) seems to null out discharging with the long sunny afternoons and water heater running.
I also changed the timers a bit. If there was not much load on the battery for a few days, even charging for 10 minutes per day to the upper Voltage limit might start to cumulatively over charge the cells. So I'm now making use of the absorption extension timer.
If the pack Voltage never drops below 26.60V (3.325Vpc) during the night, the next days absorption timer is set for only 1 minute top charge. This effectively eliminates the possibility of cumulative over charging. If we went away for a long time, I'd shut the whole system down.
If "normal" amounts of charge are taken from the pack, the Voltage drops to under 26.60V and the next days absorption timer assumes an extended absorption timer setting of 20 minutes.
I had noticed that 10 minutes wasn't resulting in a very large fall-off in input power to the battery during the constant Voltage phase, so extending the time seemed appropriate (with the new safeguard of a much shorter default timer).
The small SunSaver 15 Amp charger has now had its absorption timer defaulted to 1 minute for any condition.
With the clear blue days we've been having, I've seen total charge rates as high as 72 Amps, and at the top of charge, the battery pack doesn't need the assistance of the small charger for long before the Tristar charger can hold the constant Voltage.
Showing posts with label Morningstar. Show all posts
Showing posts with label Morningstar. Show all posts
Friday, February 24, 2012
Sunday, February 19, 2012
Initial Tests & Programming the Morningstars
First day of solar charging the new Winston Battery pack.
Got the two Morningstar charge controllers re-programmed with very conservative settings to start to get a feel for how the pack would behave. It was very sunny from the get-go, with the chargers putting out a combined 55 Amps into the battery. No magic smoke ensued. For that matter, nothing even got the slightest bit warm; none of the cables; the new "200" Amp battery disconnect breaker; any of the cells.
I checked the live data feeds from the two chargers with the MSView software to double check that they were adhering to the expected target Voltages and temperature compensation slopes. Some months ago, I'd previously had an issue with one of the programming wizards that had a bug in the temperature compensation settings, but Morningstar were quick to provide a bug fix after I mailed their software support team.
Basic settings are as follows (per cell values in brackets):
Absorption Target Voltage: 28.00 (3.50)
Absorption (Constant Voltage) Cumulative Time : 10 mins
Absorption Time Extended: none
Float Target Voltage: 26.80 (3.35)
Float Exit Time: 12 hours
HVD (trigger): 29.00 (3.625)
HVD (release): 26.40 (3.30)
Max Regulation Voltage: 28.40 (3.55)
Temperature Compensation: Pack -60mV/C (25C to 80C)
The smaller SunSaver charger has the same settings with the exception that the absorption target Voltage is set to 27.90V, so that this charger quits before the main one and then the main one is in the driving seat to control the finishing charge. This is especially important because the SunSaver charger does not have remote terminal Voltage sensing.
An overview of the programming wizard in the MSView software is included in the second video below. Speaking of which, today's video is a monster. It was so long (23 minutes) that I had to split it into two as YouTube complained it was too long. Soon I'll be making blog videos almost as long as episodes of EVTV :D
Get some popcorn...
Tuesday, September 20, 2011
Micro Battery Off Grid System
Sorry for the lack of posts... No excuses, but I have been busy over the summer [Damn. That sounded like an excuse...]
Remember the Big Capacitors of a few posts ago? Well they've found a use :D
They're really cool, as it happens. I charged them up and left them with a Volt meter on them, to see how long they could hold a charge for. Kinda expected they would self discharge in a few minutes, if left alone.
Time ticked on, and they didn't seem to discharge (now that the LED Voltmeter was not connected to the tops). In fact, a couple of weeks later they had only discharged down to a few Volts less than when they were full! Extremely low leakage current. When I shorted them out by accident, they still packed a terminal blackening punch :D
I got a couple of big 230Wp panels to test from a friend, and got to wondering about how I could use them. I had a spare 1kW inverter and a spare MPPT charge controller. Having a big 500Ah battery bank on the main house, I wondered about the opposite. How small a battery could you use for an off grid system..?
Luck came in the form of a bargain bin at a DIY superstore. They were selling off loads of drill batteries for just £3 each. [rant mode ON] The cunning manufacturers change the drills and batteries to be slightly different each year so that your old batteries can't be used on their new drills... (built in obsolescence, again). It also mops up those pesky consumers who think that they can keep their old drill until it breaks... Oh, no. They change the shape of the new "spare" batteries so that they don't fit the old drills - forcing you to buy a whole new drill set. [rant mode OFF]
Anyhoo... it means experimenters can pick up brand new 12V and 14.4V NiCd battery packs for less than the cost of a single cell at an electronics store. These cells are also rated for high current applications - A cordless hammer drill can pull 20A when working hard.
So, I had a pair of 12V drill batteries wired in series to make a titchy (for off grid use) 24V, 1.5Ah battery pack. But it can deliver 20A easy (480W). Good for a steady load but not enough to start something big, like a fridge or big TV... Enter the big capacitors!
The capacitors can pack a punch of maybe a few hundred Amps for a second or two and the NiCd batteries can deliver 20 Amps for about four and a half minutes. NiCd cells are good in that very small ones can sustain high drain currents without their effective capacity being degraded. Small lead acid batteries would be useless, as firstly their capacity drops as you drain them faster and draining them until they are empty is a sure way to kill them. NiCd cells don't mind being drained flat - it's what happens when they're used in a drill.
So what I had was a 460W solar array with a 480W four minute "buffer". You can use this system to power quite big stuff on a sunny day without the bulk and expense of a big lead acid battery bank and it will keep your load going when small clouds pass in front of the array. It only takes about 15 minutes of charge for the battery to get to full from empty.
Some drill batteries (the ones designed for a fast charger) even come with a temperature sensor in the pack, so the drill charger won't over charge the pack and cook it. Unfortunately, the 12V packs I bought didn't, but the Morningstar MPPT-15 charge controller has one. I super-glued it to the top of one of the packs. This charge controller is also fully programmable. So, despite being primarily for lead acid batteries, it can easily be programmed to charge NiCd batteries. You just have to set the Voltages differently (a topping charge of 30V and then a float of 28.5V) and the timers much shorter (as the pack is so small). I programmed the temperature compensation to do nothing below 25 degrees C, but then start an aggressive negative slope above that. So, if the cells are heating up from high charge or discharge currents, the charge Voltage would be reduced. The charger itself is limited to 15 Amps charge current.
So far it's worked ok. I managed to run a 140W 28" LCD TV on it for a whole afternoon with only a couple of power failures (when it started to cloud over in the afternoon). The fully charged battery could run the set for about 12 minutes without direct sunlight on the array. The capacitors provide the oomph to start the inverter and the TV without the Voltage dropping. At the "float" Voltage of 28.5V, the two 1F capacitors store 28.52 x 0.5 Farads x 0.5 = 203 Joules of energy - or enough for 203W for 1s or 406W for 0.5s or 812W for 0.25s (although that would require draining the capacitor flat).
Huge battery banks are hugely expensive in off grid systems. This alternative method allows quite moderate loads to be run in good weather, during the day, with only a tiny cheap battery. If you planned it right, you could use the inverter in the day to do power hungry things, and then just use the NiCd battery pack at night to run ultra low power 12V DC LED lights... Or watch a very short TV show :D
Remember the Big Capacitors of a few posts ago? Well they've found a use :D
They're really cool, as it happens. I charged them up and left them with a Volt meter on them, to see how long they could hold a charge for. Kinda expected they would self discharge in a few minutes, if left alone.
Time ticked on, and they didn't seem to discharge (now that the LED Voltmeter was not connected to the tops). In fact, a couple of weeks later they had only discharged down to a few Volts less than when they were full! Extremely low leakage current. When I shorted them out by accident, they still packed a terminal blackening punch :D
I got a couple of big 230Wp panels to test from a friend, and got to wondering about how I could use them. I had a spare 1kW inverter and a spare MPPT charge controller. Having a big 500Ah battery bank on the main house, I wondered about the opposite. How small a battery could you use for an off grid system..?
Luck came in the form of a bargain bin at a DIY superstore. They were selling off loads of drill batteries for just £3 each. [rant mode ON] The cunning manufacturers change the drills and batteries to be slightly different each year so that your old batteries can't be used on their new drills... (built in obsolescence, again). It also mops up those pesky consumers who think that they can keep their old drill until it breaks... Oh, no. They change the shape of the new "spare" batteries so that they don't fit the old drills - forcing you to buy a whole new drill set. [rant mode OFF]
So, I had a pair of 12V drill batteries wired in series to make a titchy (for off grid use) 24V, 1.5Ah battery pack. But it can deliver 20A easy (480W). Good for a steady load but not enough to start something big, like a fridge or big TV... Enter the big capacitors!
So what I had was a 460W solar array with a 480W four minute "buffer". You can use this system to power quite big stuff on a sunny day without the bulk and expense of a big lead acid battery bank and it will keep your load going when small clouds pass in front of the array. It only takes about 15 minutes of charge for the battery to get to full from empty.
Some drill batteries (the ones designed for a fast charger) even come with a temperature sensor in the pack, so the drill charger won't over charge the pack and cook it. Unfortunately, the 12V packs I bought didn't, but the Morningstar MPPT-15 charge controller has one. I super-glued it to the top of one of the packs. This charge controller is also fully programmable. So, despite being primarily for lead acid batteries, it can easily be programmed to charge NiCd batteries. You just have to set the Voltages differently (a topping charge of 30V and then a float of 28.5V) and the timers much shorter (as the pack is so small). I programmed the temperature compensation to do nothing below 25 degrees C, but then start an aggressive negative slope above that. So, if the cells are heating up from high charge or discharge currents, the charge Voltage would be reduced. The charger itself is limited to 15 Amps charge current.
So far it's worked ok. I managed to run a 140W 28" LCD TV on it for a whole afternoon with only a couple of power failures (when it started to cloud over in the afternoon). The fully charged battery could run the set for about 12 minutes without direct sunlight on the array. The capacitors provide the oomph to start the inverter and the TV without the Voltage dropping. At the "float" Voltage of 28.5V, the two 1F capacitors store 28.52 x 0.5 Farads x 0.5 = 203 Joules of energy - or enough for 203W for 1s or 406W for 0.5s or 812W for 0.25s (although that would require draining the capacitor flat).
Huge battery banks are hugely expensive in off grid systems. This alternative method allows quite moderate loads to be run in good weather, during the day, with only a tiny cheap battery. If you planned it right, you could use the inverter in the day to do power hungry things, and then just use the NiCd battery pack at night to run ultra low power 12V DC LED lights... Or watch a very short TV show :D
Sunday, August 15, 2010
Updated Monitoring Network
I finally got round to completing the Morningstar monitoring network. The problems with the Toshiba laptop and Vista and the clunkiness of having to start up the machine and configure the logger and so on each day (to save wasting too much power at night) got to me. Below is an example of the type of connection that can be made between Morningstar products. I don't have a Relay Driver but it shows that you can connect a bunch of things to the EIA485 data bus.
The Morningstar SunSaver MPPT charge controller can talk to the TriStar controller if it has the right adapters. I already had a RS232 adapter to connect the SunSaver to the laptop but you need an EIA485 converter to connect it to the same port on the TriStar.
Although EIA485 isn't common in day to day PC networking, it is common in industrial telemetry as it can work over a four wire bus and transmit up to 1.2km without repeaters. RS232 is only good for a few meters and even Ethernet runs out of steam at 100m. It's a bit of a pfaff when you only want to connect two things together by a 30cm bit of string though...
The instructions suggest using Cat 5 Ethernet cable for the 4 wire bus. Two are used for +12V and Ground power lines and the other two are the A and B serial data lines. They suggested using Ethernet cables because they have twisted pairs to eliminate interference. But I ignored that and just used 4 core flat telephone wire as it was such a short cable I was making. They also say that you're supposed to terminate the A and B wires at each end of the bus with a 100 Ohm resistor between them. I sort of did this by putting a 100 Ohm resistor at one end (inside the Tristar wiring box where it would be safe from being knocked). I didn't have two 100 Ohm resistors in my spares box so I didn't bother with the one at the other end... Seems to work ok without it. I've been receiving data from the SunSaver without problem so again it's probably only important for long wire runs.
With the SunSaver connected to the TriStar, you can use the MSView software to talk to any device on the EIA485 bus (up to 128 devices) using IP. The TriStar can be set to bridge the Ethernet and EIA485 networks (it just forwards the MODBUS packets to the devices on the EIA485 network). It's especially handy because with the exception of the TriStar MPPT-60, no other Morningstar products are IP enabled but now they can be. It opens up the possibility of using cheap and commonly available networking products to move the data around. For instance, I don't have Ethernet cable run around the house. I have a wi-fi transmitter and the TriStar is actually connected to the computer upstairs via an Ethernet switch and a pair of Netgear Ethernet over AC power adapters. This was more reliable than the wi-fi (which has a dead spot in that part of the house) and the CCTV data also travels over that switch and link.
So now my laptop upstairs can fetch performance data from the Tristar controller and also directly from the SunSaver controller. The two controllers share the same IP address on the Ethernet but have different MODBUS IDs so each controller responds only to it's own commands.
You have to run the custom settings wizard for each controller to change the default MODBUS ID (all Morningstar devices are preset to "1"). So I changed the SunSaver controller to be ID "2" and left the TriStar on its default of "1".
The EIA485 network needs external power of 12V DC so I connected the two power pins on the EIA485 connector plug to the variable lab power supply that I use to run the AA battery charger and mobile phone chargers. This converts the battery 24V to the needed 12V, although the EIA485 adapter isn't fussy and will work on any voltage between 8 and 16V, so you could just connect it to a 12V solar battery directly. But I'm running a 24V system so I have to use a DC-DC converter. The pair of adapters (RS232 and EIA485) together only consume about 20mA (or 0.5W power) so I can leave them running 24 hours (unlike the Toshiba laptop that consumed about 11W.
Although EIA485 isn't common in day to day PC networking, it is common in industrial telemetry as it can work over a four wire bus and transmit up to 1.2km without repeaters. RS232 is only good for a few meters and even Ethernet runs out of steam at 100m. It's a bit of a pfaff when you only want to connect two things together by a 30cm bit of string though...
The instructions suggest using Cat 5 Ethernet cable for the 4 wire bus. Two are used for +12V and Ground power lines and the other two are the A and B serial data lines. They suggested using Ethernet cables because they have twisted pairs to eliminate interference. But I ignored that and just used 4 core flat telephone wire as it was such a short cable I was making. They also say that you're supposed to terminate the A and B wires at each end of the bus with a 100 Ohm resistor between them. I sort of did this by putting a 100 Ohm resistor at one end (inside the Tristar wiring box where it would be safe from being knocked). I didn't have two 100 Ohm resistors in my spares box so I didn't bother with the one at the other end... Seems to work ok without it. I've been receiving data from the SunSaver without problem so again it's probably only important for long wire runs.
With the SunSaver connected to the TriStar, you can use the MSView software to talk to any device on the EIA485 bus (up to 128 devices) using IP. The TriStar can be set to bridge the Ethernet and EIA485 networks (it just forwards the MODBUS packets to the devices on the EIA485 network). It's especially handy because with the exception of the TriStar MPPT-60, no other Morningstar products are IP enabled but now they can be. It opens up the possibility of using cheap and commonly available networking products to move the data around. For instance, I don't have Ethernet cable run around the house. I have a wi-fi transmitter and the TriStar is actually connected to the computer upstairs via an Ethernet switch and a pair of Netgear Ethernet over AC power adapters. This was more reliable than the wi-fi (which has a dead spot in that part of the house) and the CCTV data also travels over that switch and link.
So now my laptop upstairs can fetch performance data from the Tristar controller and also directly from the SunSaver controller. The two controllers share the same IP address on the Ethernet but have different MODBUS IDs so each controller responds only to it's own commands.
You have to run the custom settings wizard for each controller to change the default MODBUS ID (all Morningstar devices are preset to "1"). So I changed the SunSaver controller to be ID "2" and left the TriStar on its default of "1".
The EIA485 network needs external power of 12V DC so I connected the two power pins on the EIA485 connector plug to the variable lab power supply that I use to run the AA battery charger and mobile phone chargers. This converts the battery 24V to the needed 12V, although the EIA485 adapter isn't fussy and will work on any voltage between 8 and 16V, so you could just connect it to a 12V solar battery directly. But I'm running a 24V system so I have to use a DC-DC converter. The pair of adapters (RS232 and EIA485) together only consume about 20mA (or 0.5W power) so I can leave them running 24 hours (unlike the Toshiba laptop that consumed about 11W.
Subscribe to:
Posts (Atom)