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Current Very Slow

The current moving between cells quickly slowed and kept slowing. I let the batteries sit wired in parallel for about 3 weeks with no charging, mostly because I got side tracked...


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John 29-Aug-2016 00:58

Enjoyed your extremely thoughtful and detailed N=1 experience with LFP. On my last boat I had 3 x 200Ah Sky Energy /Winston Cell for the house and treated them with total disregard- No top balancing (shunts only), float charging to 14.6V and a few other sins (no BMS) for a period of 3 years. Never had an issue.

On the current boat, a Maine built Able Apogee 58 (Chuck Paine design), I am replacing the 3 year old 8 x 700Ah Winston cells (all in series for 24V configuration.)(possible degradation by a lightning strike- at least one cell won't charge beyond 2.7V). The Battery MONITORING (not management) system and chargers were also fried. Thankfully the insurance co said replace them all. This bank too was float charged, but only to 24.4V and had cell level shunts, cell level monitoring and never went below the 2.85V/ Cell LVC or the 3.75V/ cell HVC. Never had an issue until mother nature weighed in.

It was great to stumble upon your article since I am now taking your approach to battery setup and mgt. on the new 700Ah battery bank. Using a company called Voltronix in Calif, I have had them test 8 cells, matching them for internal resistance and total Ah capacity and then top balancing. We have graphed a baseline discharge curve down to 2.99V for each cell and am showing an average of 104% capacity.

The new battery Monitoring system is the Orion Jr. BMS and is configured with relays to cut off charging including solar) at the designated 28.8V (3.6V/cell)and eliminate float stage from either the MPPT Controller or the Elcon Charger. Peak Solar Input averages 6-10A @ 24V nominal. Unfortunately, the 24V charger is small, rated at just 80A at 230V (my shore and genset V), or about .11C. The backup Charger is a Xantrex 2500W Inverter/ Charger used only for Inverter mode.

Based your experience, I am going to back the max off to 28.4V (3.55V/cell). My floor discharge voltage is set at 3.0V/cell with a LVC of 2.9V (23.2V total). HVC is set at 3.7V/cell (29.6V). I may also reduce this a bit. My loads are a bit higher than yours, typically 12-35A @ 24V when underway and 6-24A at anchor, depending whether refrigeration is running.

I have two Balmar MaxCharge 624 External Voltage Regulators managing two large case Leece-Neville 105A alternators. Both run cool to the touch. They will be configured consistent with above voltages per your methodology but I do not have a separate relay for cut off. ( I have separate starter batteries connected for engine and 8KW genset and for the 24V Electronics bank which is charged of the house bank.)

My question is- should I have a relay to cut off the alternators to the house bank? Not sure how this fits with the sensing wire arrangement- I have now reached the limits of my electrical knowledge here.

Whole package set to arrive next Friday (9/2/16) after being set up tested, discharged to 80% and then recharged to 50%.

In any event I will keep you posted on my experience. I have PC based monitoring software which will download captured historical data from BMS so this will be my N=1 as well. Happy to talk offline if this is too much for a forum.


John Lubimir
s/v Patriot (currently lying Hinckley Yacht services in Stuart, FL)