CharlieJ

So how I lost my forum connection. The reply was too long so I emailed it to you.

T1 Terry

No idea how this got tacked onto the wrong conversation, but hopefully you can sort it out enough to follow what I've posted

T1 Terry

We tried a 200 amp load test on a 100ah battery, it ran for the required 30 mins but the cells got quite warm so we decided that might not be a good idea for a demo ....

We have a 1200Ah 24v system we need to load test as part of the 3 yrs service, but we haven't figured out how we are going to cool a 600 amp @ 24v load for 2 hrs .... so it hasn't happened yet :lol:We do this service and load test roughly every 3 yrs so we can report to the owners how the battery pack is coping with the work load it's experiencing, so far none have failed to deliver the full advertised capacity and still hold 3v or more under load at the end of the 2 hrs, at least three of the systems have been working 24/7 for over 10 yrs now and still return 100% capacity and still hold the 3v percell under load .... so we must be doing something right ...

I have had to shorten each message to get under the 1000 character limit, so it might take another few instalments to get it all on here :lol:

I'd love to see someone crazy enough to try shorting a 12 v or 24v 400Ah battery.

To load test the batteries we use a length of stainless strap wrapped around a piece of multiple layers of ply about 4"square. 200 amps @ 12v on a 400Ah battery and it takes 4 hrs to discharge all 400Ah, and boils roughly 300ltrs of water while doing it. If a bit of the stainless strap gets above the water while under the 200 amp load at 12v, it glows yellow almost instantly. A 24v 200 amp load boils the 300 ltrs in under an hr.

We tried to be a 48v battery once, the heat was so great the stream held the water away from the strap, it glowed and fused and that was only at 100 amps.

I'm not sure anyone has been crazy enough to try and measure it :lol: I'm guessing you seen the meme with the spanner across a single 100Ah cell (so only 3.2v nominal) glowing yellow red and the bolt in one of the terminals white hot a spitting metal, just at the point of blowing apart ...... the caption says "I think Ill just leave it" I think it might have been on a site called Friday Funnies, but it was a few yrs back from memory.
There is a You Tube clip where someone decides to test a single cell with O gauge cables (50mm sq) and a knife switch, it blows the contacts off the knife switch so he has to change to double cabling either side and increases the cable length as well as changing to a much higher rated knife switch .... after a few mins the cables are smoking yet it continues for around 10 mins from memory, so it's not just the instant current, the chemistry will sustain the short circuit current for quite some time.

T1 Terry

Hi Charlie,

Have to thank you for your input on my thread about the Yanmar / Battery circuit. I have found it very difficult to find consistent information about this. It's like putting 10 economists in a room - you get 10 different opinions. Your posts are clear and, more importantly, have references. I am very happy with the current design and I'm sure it will work well on the boat.

This stuff is important to me. I have a fairly good grasp of DC circuits (used to be a telcom tech) but there are significant differences when applying to boats. A lot of people urge me to get professional advice - and I will get someone to go over it - but where's the fun in that. I learn by researching and doing. I want a deep understanding of how all this works.

Cheers

Steve

yah...I miss you, but I miss Angi more...Tess is no cook!