Recent content by ckris

Very much what I have been thinking the last few years. It always used to be a binary choice on my boat to sail 2H or with 8/9 in RORC races because they used to have this weird rule that only 2H boats could use an autopilot, so you needed enough people to share the hand steering if sailing with...

Appreciate the world was different when you were younger but today girls, couples and youngsters can be go yacht racing as well....?

How the mark is described in the course/SIs matters. If b is a passing mark (eg pass to port) then can leave on the required side any distance away. If b is a rounding mark then a string representing the boats track pulled tight must touch the mark - meaning you may have to loop the mark. See...

Haha, yes size matters! But the op was talking about adding 50ah lithium. The point is, lowering the charge voltage does reduce the current accepted and this will be true for any size of battery (even yours if you lower the charge voltage enough). The voltage drop along battery cables may do...

Exactly what I see happening in practice, with the battery cable voltage drop having same effect as a resistor.

Hi kwb78 Great explanation and kinda what I was expecting when I switched to lifepo4, but I observed in practice a much less dramatic effect. My agm house battery swapped for 105ah lifepo4 with bms set for 12v low voltage and 14v high volt pack disconnect, which should keep between approx 10%...

A longer battery cable works very well in practice.

Not familiar with the Eco-worthy but looks like it does not have a configurable BMS or bluetooth, also not clear how it handles temperature protection or the warranty position. I have used 2 suppliers which I have been impressed with that you may want to check out: Life Batteries - slightly more...

OK, we can plug in slightly different numbers but when you add in the BMS and internal cabling I still think this explains why the short circuit current from a drop-in LFP may be much smaller than you might intuitively expect......which practically matters to determine the AIC rating of any...

Yes - but we were (well I was) trying to understand why such experiments as linked in post #56 indicate short circuit currents of a drop in lifepo4 battery are much lower than an equivalent size AGM which is counter-intuitive to LFP cells having low IR, very high discharge currents and faster...

Sorry, I know this might be tiresome and way off the topic of this thread but I am really trying to be sure I have not misunderstood this. If a single Lifepo4 cell is fully charged at 3.4v and has internal resistance of 0.5 milliohms using I = v/r gives a potential short circuit current of...

And the research paper linked to by migs above? I dunno, I am just a bloke on the internet trying to have more fun sailing. I would offer that AGM IR reduces as it reaches higher SOC......but it doesn't start charging faster so there is more to charge acceptance than IR. I also suggest there...

Still not with you. AGM battery at 12.8v and IR 4.8 milliohms = short circuit current 2666a. LifePO4 drop at 13.6v and IR 20 milliohms = short circuit current 680a. ( I know AGM specs said short circuit current 2555a but assume they used a mid voltage rather than highest) I understand an...

? But the above suggests pssc for lifepo4 battery is 6C = 600A for a 100ah lifepo4. My 100AH AGM specs say short circuit current = 2550.....equivalent to 25C. Why must it be AIC requirements for LFP will exceed AGM - what am I missing?

Thank you for the comments on fusing. I found the specs for my AGM batteries which quote internal resistance 4.80 and short circuit current 2,555a. I also did not find anything definitive for the drop in Lifepo4. Life batteries website mentions resistance 20 milliohms which imply a short...