New Lithium Battery Report

[rgleason]

Paul,


Its a smaller boat, on a mooring, with limited room for solar 200-300watts max, 100w now, when we finally change to LFP the alternator will be the primary charger. I have some specific goals about charging C so it does not force engine use more than necessary. There isn't room for multilple DC/DC units. Still having trouble finding a suitable location for LFP. I'd rather use a small DC/DC for the starter battery, but I see others are rethinking that too.


I was referring to adjusting the wakespeed.

Originally Posted by PaulCrawhorn

Or just use GEL lead, Deka or Sonnenschein

Setpoints are just fine for both.

What have you got against DCDC?

Which adjustable VR are you talking about?

Is your alternator even a significant charge source overall, you spend a lot of your off grid time motoring?

[goboatingnow]

Originally Posted by rgleason

Actually a reasonable approach, so that LFP is easily removed for winter. I was considering placing the BMS/LFP in a small case under the fold up table on the cabin sole and strapping it to the buikhead, but there isn't enough room.

However if you wanted to charge the LFP directly with the alternator how would that work when you remove the LFP?

I still don’t follow the logic to remove the bank over the winter. It defeats the whole purpose , why not just stay with lead.

The lithium setpoints of the alternator would be fine as your dc dc to the starter will handle the charging

You could either reprogram the wakespeed , which is a simple task or ignore it.

Your plan to charge the LFP from the alternator is the most efficient , but I don’t get the justification for removing the LFP in the winter.

My small solar easily supports the boat laid up over the winter

[rgleason]

Originally Posted by goboatingnow

I still don’t follow the logic to remove the bank over the winter. It defeats the whole purpose , why not just stay with lead.

I was thinking about the few times that temps drop to the teens in Rhode Island and concern about the LFP freeze up and the possibility of using it to power the dink too (not really necessary).

The battery needs a dry and accessible place in the cabin, not stuffed into some small inaccessible area, accessed easily without disruption of normal activities if possible, with enough ventilation to keep the temps low, ideally reasonably close to the alternator to reduce cable runs.

I had an idea that if I installed a Quickstart rectifier, it would reduce heat in the engine area, and I could run the 3 wires with AC current to the battery area and have the rectifier near the battery. It might save on heavy 0/2 wire as well.

Originally Posted by goboatingnow

The lithium setpoints of the alternator would be fine as your dc dc to the starter will handle the charging. You could either reprogram the wakespeed , which is a simple task or ignore it.

Good point, I realized that afterwards.

Your plan to charge the LFP from the alternator is the most efficient , but I don’t get the justification for removing the LFP in the winter.My small solar easily supports the boat laid up over the winter

I guess I could put a small thermostatically controlled heating mat in the battery area, and rig one of my 50w SunPower panels that is normally on the dodger in the summer. The winter temps are on the margin in RI I think. I would also want to have any charging stop below freezing. Where is your boat located?


Sorry, I guess this is off topic.

[goboatingnow]

Originally Posted by rgleason

I was thinking about the few times that temps drop to the teens in Rhode Island and concern about the LFP freeze up and the possibility of using it to power the dink too (not really necessary).

The battery needs a dry and accessible place in the cabin, not stuffed into some small inaccessible area, accessed easily without disruption of normal activities if possible, with enough ventilation to keep the temps low, ideally reasonably close to the alternator to reduce cable runs.

I had an idea that if I installed a Quickstart rectifier, it would reduce heat in the engine area, and I could run the 3 wires with AC current to the battery area and have the rectifier near the battery. It might save on heavy 0/2 wire as well.


Good point, I realized that afterwards.

I guess I could put a small thermostatically controlled heating mat in the battery area, and rig one of my 50w SunPower panels that is normally on the dodger in the summer. The winter temps are on the margin in RI I think. I would also want to have any charging stop below freezing. Where is your boat located?


Sorry, I guess this is off topic.

Yes a small heating mat would keep the LFP happy.

The internal temperature might only be a problem occasionally do the matt would only be used occasionally

[newhaul]

Originally Posted by rgleason

I was thinking about the few times that temps drop to the teens in Rhode Island and concern about the LFP freeze up and the possibility of using it to power the dink too (not really necessary).

The battery needs a dry and accessible place in the cabin, not stuffed into some small inaccessible area, accessed easily without disruption of normal activities if possible, with enough ventilation to keep the temps low, ideally reasonably close to the alternator to reduce cable runs.

I had an idea that if I installed a Quickstart rectifier, it would reduce heat in the engine area, and I could run the 3 wires with AC current to the battery area and have the rectifier near the battery. It might save on heavy 0/2 wire as well.


Good point, I realized that afterwards.

I guess I could put a small thermostatically controlled heating mat in the battery area, and rig one of my 50w SunPower panels that is normally on the dodger in the summer. The winter temps are on the margin in RI I think. I would also want to have any charging stop below freezing. Where is your boat located?


Sorry, I guess this is off topic.

Remember most good solar charge controllers have a temperature sensor and when set to the lifepo4 charge profile it stops charging when below freezing. Mine actually cuts out when the sensor hits +1C . My bms also has the same feature . Aside from the fact the self discharge rate is so low no need to charge during layup periods.

[rgleason]

Thanks Newhaul. I checked the ABYC wire calc to answer a question I had about wire size for AC vs DC with the Quicktifier Rectifier and there really is no difference in wire size for same amps and distance, etc. Probably not worth the extra cost if not needed.