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...
Hello,
ReplyDeleteI´m always reading on the homepage/blog from GWL about "Over charge protection".
How do you make an "over charge protection" with your system?
I could implement an over charge protection (and was going to, using a second CellLog8 with the upper voltage alarm function). But as it turns out, it isn't necessary.
DeleteThe charger is programmed to only charge to a safe pack voltage of 3.50V per cell and it stops a short time after reaching that voltage. Because the pack is balanced and then operated within the linear region of the charge curve (so that no cells get to be completely full or empty) the pack stays in balance.
So far I've completed about 150 cycles with no issue.
Over charge protection is a main feature of top balance BMS designs that always push the cells to a high voltage (3.65V per cell or more) in the non-linear range of the charge curve and have to use shunts to stop the cells that get full first from being damaged. This is a dangerous way to operate a battery in a highly non-linear unstable mode where you are relying on brute force power electronics to stop the cells from doing what they want to - to self-destruct!
In my system, I only have to make sure that no cell is over discharged below 3.00V to maintain the bottom balance. It does this by simply turning the load off!
Hi There,
ReplyDeleteI just stumbled on your blog, I need to replace 500Ah on my boat and was looking at LI-ion. Now I dont want to replace my chargers (Outback FX and a morningstar). Could you let me know how you re-programmed the morning star?
Cheers,
Michael
Hi Michael,
ReplyDeleteIf you're in the UK or Europe, we can help you with replacing that lead acid battery bank with our Lithium ion solution. Mosey on over to www.sustainables4u.co.uk for more info.
We can most probably work with your existing chargers but would need to look at how the loads on your boat work with the battery bank, as Li-ion banks need more strict over-discharge protection.
Hi,great blog. Looks as if you may be the only resource that can help me out. Could you tell me what your current controller setting are?
ReplyDeleteI have a Sunsaver MPPT I'd like to charge my StarkPower Ultra Energy 12V 100Ah LiFePO4 battery with and I'd like to maximize battery life. At most I'll use 40Ah a day.
Thanks,
Craig
(SP-12V100-EP) battery info
Voltage: 12V
Capacity: 100Ah, 1280Wh
Chemistry: LiFePO
Weight: 32.6lbs (14.8kg)
Dimensions: 13"(L) x 6.8"(W) x 9"(H), [330mm(L) x 172mm(W) x228mm(H)]
Life Cycles: 2,000 @ 80% DOD
BMS: YES (Internal)
Max Charge Voltage: 14.6V
Discharge Cut-off Voltage: 10.5V
Max Charge Current: 50A
Max Discharge Current: 100A
Max Starter Current: 300A
Operating Temperature: -22°F to +140°F, (-30°C to +60°C)
Hi Craig,
ReplyDeleteThe values given by the manufacturer are pretty much absolute maximums beyond which you'd quickly destroy the battery.
Depending on the quality of the "internal BMS" in the battery, you might be able to charge to 14.6V but the BMS should have a way of telling the charger to stop. The use of bulk chargers (those that do not monitor each cell individually and only view the pack Voltage) are not good, but you can get away with it as a bodge if you use very conservative charging values and a few other conditions are met.
Charging any lithium ion cell or battery without over charge protection can lead to cell venting, swelling or even fire. Use of bulk chargers in this way is done at your risk. The settings I have suggested in this blog are applicable only to the cells I am using and you'll have experiment with your battery to find the best settings for that battery and your particular application of that battery.
I'd suggest that the discharge cut off limit they have suggested is very low and will risk damage to the battery, depending on the number of times you hit that limit and under what discharge circumstances.
I'm now designing a commercial product for solar energy storage as part of a home energy management system, so this blog is now maintained only as an archive.