Hi guys. Midway through installing. I have the panels mounted and working through wiring. Looking for thoughtful comments.
Here are a couple pics of install to date.
Here are a couple pics of install to date.
Quick update.
Finally started bottom balancing the cells. In this procedure each of the (24) 3.2v/100AH cells is discharged to 2.5 volts, allowed to recover to around 2.8v and then again discharged to 2.65v. Each cell should recover to around 2.7v. At that point cell voltages are compared. They should all be within a couple hundredths of a volt from each other. At that point groups of 4 in series are charged together and again voltages compared. I start with a relatively low charge limit and slowly adjust up to ensure no single cell will be charged past the manufacturers safe limit of 3.65. My actual final limit will probably be in the 3.4v max per any cell staying well below the margin of safety while charging. There is very little energy to be gained by trying to may out charging capacity.
Finally started bottom balancing the cells. In this procedure each of the (24) 3.2v/100AH cells is discharged to 2.5 volts, allowed to recover to around 2.8v and then again discharged to 2.65v. Each cell should recover to around 2.7v. At that point cell voltages are compared. They should all be within a couple hundredths of a volt from each other. At that point groups of 4 in series are charged together and again voltages compared. I start with a relatively low charge limit and slowly adjust up to ensure no single cell will be charged past the manufacturers safe limit of 3.65. My actual final limit will probably be in the 3.4v max per any cell staying well below the margin of safety while charging. There is very little energy to be gained by trying to may out charging capacity.
nickmgray wrote:
Very interested to see the final results. I've actually been doing some research of my own forand stumbled upon these same batteries yesterday.
Are you able to upload the kayout/diagram again? The link in the first post doesn't seem to work for me. I'm still in research mode, so I'm quite interested to see what the schematics for your install look like.
Thanks for the interest, here you go. The batteries will be 'wired' as shown on first page image not 4s6p as shown here.
I got the solar charge controller up and running today. The inverter will be next. The cells still need bottom balancing and assembly. That will take a couple days or more.
Dry fitting into the generator compartment without batteries. All cabling can be measured, built and checked for fit now to solar charge controller, inverter and house 12v.
HMS Beagle wrote:
LFP are becoming more common in sailboat applications and I have read about the need to restrain them against swelling, and some opinions that it needs to be fairly stiff. But I have yet to see a spec or any tests showing how forceful this swelling can be. I have seen pictures of batteries ruined by unrestrained swelling. You could perhaps add a steel angle or square tube across your plywood end to stiffen it up - but I have no idea if that is necessary.
From what I can gather reading online these newer CALB cells don't swell unless they are pushed well over max charging voltage. One article I read they couldn't get swelling even overcharging to 4.2v
Not running a BMS to individually manage cells and shunt our redirect voltages I am going to be charging to lower limits. After bottom balancing I will be carefully monitoring where each cell rises to and adjust the charging limits for the bank to keep those fastest risers well within their designed voltage. With LFP there is so little gained by trying to push to the very top of cells capacity on both ends and so much to lose. Staying clear of the cliffs is important.
Still researching battery monitoring and management systems... My main concern isn't overcharging (and swelling) as I have decent control over that with my charging devices. The more realistic fear for me is over discharging by accident. That is what the Victron Battery Protect is for. Still looking at secondary protection options as well.
