Something else to look out for.

My 120 amp hour lithium iron phosphate battery came with a couple of bolts to act as the terminals however I wanted to put three leads onto one of the terminals one of which was a bit thick so I went down to a battery place and asked if they had a bolt which was a bit longer. The guy happily gave me one for free.

I've been running it that way for a little while but I'm not that pleased with the battery and notice it's internal resistance is high and once and internal siren went off whilst charging so I was doing a video as evidence to support a return. The low voltage cut out also doesn't seem to work at least not within 0.5 of off a volt of where it is supposed to.

Normally I put the charger on and walk away but this time trying to video things and putting a volt meter on the terminal as well I noticed that the terminal with the non-standard bolt was very hot. I measured the temperature at each terminal and the non-standard bolt was at 54 degrees C whereas the standard one was at 37 degrees C. I swapped the bolts positive for negative and the heat went with the non standard bolt. I suspect that non-standard bolt is stainless steel whereas the specifications say that the standard bolt is nickel coated iron.

Maybe don't mess with or swap out your bolts!

This is for a battery which is supposed to support 50 amp charging and as it is out of the boat I am using a mains 40 amp charger althoigh the clamp meter says its only 36 amps going in. Probably this wouldn't be a problem when charging using solar has my solar system can't achieve anywhere near that amperage although the bolt is clearly adding to resistance no matter what type of charging or discharging is going on.

The stainless has a higher resistance. What about trying brass bolts with a smear of vaseline?

I noticed similar issues when using a Lithium Iron Sulphate battery for an electric outboard. For house lithium I got onto eBay for battery posts (brass or lead). Fitted these instead of the bolts and went back to 12v car clamps allowing more space for connections.

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Ramona said..
The stainless has a higher resistance. What about trying brass bolts with a smear of vaseline?

Thanks will do. Came across attached which might be useful for others. Was surprised at the massive temperature difference.

My race car has SS bolts into the terminals on an AGM battery. After looking at that table I might have to go bronze.

www.babf.com.au/products/144500?srsltid=AfmBOoprNKsxgQmNE5aarajBjQPVnrVpcPRssf8i_SVZ-GqDbD5sZ25J

I would have thought the bolt is there to put clamping pressure between the battery terminal face and the wire lug. Not to carry the current.

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Jolene said..
I would have thought the bolt is there to put clamping pressure between the battery terminal face and the wire lug. Not to carry the current.

True but during mains charging the bolt head is the interface for the alligator clip

We are talking about electrical conductivity. Iron is already a bad conductor and when you mix it with carbon to make steel and stainless steel its terrible. Hence your hot terminal Jules. Ohms law says P (watts) = Amps x Amps x R (resistance/conductivity). So immediately the higher the R the higher the P (heat). Copper is right near the top and generally the best easy to get low cost and high conductivity, and if its tin plated a little it reduces oxidation and corrosion.

Trek, I can't let that equation slip through without explanation. (I am a Science teacher).

Ohms law - Voltage = Current (I) x Resistance (R)

Power (l) = Current (I) x Voltage (V)

Combining the two gives us.

Power = I Squared x R.

So when Jules is trying to push 32 amps in with his battery charger it will have 4 times the heat loss compared to when he pushes 16 Amps in. And if he uses a small 4 amp battery charger he will be generating about 1.5% of the heat loss for 12.5% of the current. Those pesky non linear relationships are a real bugbear.

Pushing 30plus amps needs a bit more attention to details. From my experience, wires have to be soldered to lugs and all lugs must be pretty much polished.

I am notn sure that's true Charriot. My anchor winch pulls 100 amps through non crimped lugs - although you do need a good crimpsing tool. I sand my lugs with fine sandpaper.

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Kankama said..
I am notn sure that's true Charriot. My anchor winch pulls 100 amps through non crimped lugs - although you do need a good crimpsing tool. I sand my lugs with fine sandpaper.

I my van is 1000W inverter, fine sandpaper is perfect.wrong word used.