New LFP House Battery
- Thread starter SycloneDriver
- Start date
I will check when I am on the boat tomorrow.
i don’t recall seeing that menu option when i went through the settings, but maybe i missed it or it is called something else. I do have a Charge switch and a Discharge switch. The discharge switch will kill the outflow of power out of the battery. But in the photos, both batteries are showing the discharge switches as being on.
Greg
I don't see anything wrong.I don’t want to hijack @SycloneDriver’s post, but this is AlFP system related, so hopefully not egregious… if I should start a new thread, please comment,
I was checking my new Humseink LifePo4 batteries today after the batteries have been on the charger for a few days. Batt 1 showed 100% SOC and Batt 2 showed 99%. Interestingly, the BMS on Batt 1 shut off the charging switch. I assume since it was at 100% and couldn’t accept any more charge. The batteries are paralleled (see photo below).
View attachment 233092
I went out for a 2.5 hour sail today, with a light load on the house bank (fridge, VHF, stereo, CP & instruments).
When I got back, I left the charger off until I could check the BMS for the 2 batteries. Now, Batt 1 still showed 100% SOC and batt 2 was at 86% SOC.
I am not sure why these batteries, if wired in parallel, would not supply power to the house system in equal measure. Instead, it seems that one battery is doing all of the work
View attachment 233093 View attachment 233094
I have written to Humseink to see what they can tell me (if anything). I have discovered that their BMS app will not let me see what the individual cells are doing. They did say that their engineers are working on an upgrade to the app.
So, here is a crude drawing of my DC system (left out the AC side of the equation for now)...and only the house side. Left off the starter battery, switch, charger, etc for that.
View attachment 233095
Does anyone see anything blatantly wrong with this set up (I hope not, as I have sailed with it a few times now). Or could this just an issue with the batteries? One thing I could try is to install a positive and negative bus bars and hook each battery individuslly to the bus bars. But the charger would charge the bus bars (single output charger ). Not sure that changes things much. Does paralleling LFP batteries need to be different than FLA?
Greg
I am curious as to what you have the charge and maintenance voltages set at in the charger?
Does the alternator have a programmable regulator?
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,159
It was a glorious sunny day, and it was time to test the solar panel charging my LFP.
A 50-watt panel is producing 36 watts. The app says that at this rate, it will take 36 hours to fully charge your battery. The battery is at 18%. So I let it go, and an hour before sunset, the battery had recovered to 25%.
My second battery was at 22%. I plugged in the 12V 25W Victron charger. When I got going, the message was that 25amps at 14.2 would take 3 hours to charge the battery.
When it was at 100%, I disconnected the battery, put it away, attached the solar-charged battery (at 25%) to the power charger, and went off to dinner. By the time I returned, it was at 75%.
A 50-watt panel is producing 36 watts. The app says that at this rate, it will take 36 hours to fully charge your battery. The battery is at 18%. So I let it go, and an hour before sunset, the battery had recovered to 25%.
My second battery was at 22%. I plugged in the 12V 25W Victron charger. When I got going, the message was that 25amps at 14.2 would take 3 hours to charge the battery.
When it was at 100%, I disconnected the battery, put it away, attached the solar-charged battery (at 25%) to the power charger, and went off to dinner. By the time I returned, it was at 75%.
This can happen when the individual cells in a battery are not balanced. The BMS will continue accepting a charge until all the cells are balanced at (or very close to) the same voltage. In use the cells will not charge or discharge evenly, top balancing returns them to equal voltages. This is pretty normal behavior for LFP batteries.
The other problem, uneven discharge between the 2 batteries seems more unusual. It may take a few charge/discharge cycles for the BMS to learn the SOC. The usual causes for the imbalance between the 2 batteries are uneven jumper lengths or the manner in which the batteries are put in parallel. The way you have wired the batteries was once the recommended method, it is still fine, however, current thinking has the batteries connected to a bus bar to parallel them and the loads taken off the bus. Buried somewhere on the Victron site is a basic wiring manual that shows the different methods of paralleling batteries. There may also be information on Calder's site, www.BoatHowTo.com.
While we're looking at the photos, the DC+ wires all need to be fused. One of the dangers of LFP batteries is the amount of current they can discharge in a short time. There should only be 2 DC+ connections on the battery, the jumper from B1 and B2 and the cable to a Class T fuse. A Class T fuse should be used because it has a higher interrupt level (AIC) than other fuses. If there is a short the power delivered from an LFP battery can arc across a blown fuse. Class T fuses prevent the arcing. All the wires after the Class T fuse can be fused with other styles of fuses. ATC fuses in inline holders or a Blue Seas fuse box will work. The fuse box is a bit neater.