Tuesday, July 30, 2019

Perfect timing by battery manufacturers

You might think that in all the recent hot weather, Herbie would be overflowing with solar energy, but sod's law being what it is, that ain't strictly true.

Problem one: Solar panels lose efficiency when they get very hot.  At least I ensured a couple of inches air gap under ours.  I can't think how people get on with those that are stuck to the roof.  You could have fried an egg on Herbie's roof last week.

Problem two:  In very hot weather, the fridge has to work extra hard, and as the fridge is the main consumer of electricity on our boat I imagine is might have been using at least double the amount of juice during last week's hot spell.

Problem three: Sod's law bites again.  From our Smartgauge readings It looks like our domestic batteries are on their way out, and as bad luck would have it they are just out of their four year warranty.  Clever design or what? No doubt we could continue with them for a bit, and no doubt only one of the three is beginning to fail, but you really need to have all three changed at once or the old ones drag the new one down.  Our previous Numax ones lasted five years, so these I bought from the (ex) Canal Shop at Hillmorton haven't been so good.  These days you can get batteries with a five year warranty.  I found some 135 amp hour ones that would fit in the tight space we have.  They're taller than ones we've had previously, but we have the headroom so I fancy getting those.  Of course they cost a bit more but the extra capacity and the longer life  (600 cycles) would pay off I reckon.  According to the blurb, you can take 70% out of them without harm, but I wouldn't.  I never like to take out more than we can comfortably put back in in a few hours cruise.  In case anyone is interested, here's a link to the ones I'm looking at.


Dave Ward said...

"And no doubt only one of the three is beginning to fail"

Which is why you need to identify the faulty one ASAP! It's better to have a lower capacity battery bank with all the remaining batteries in good condition, than having one "Dud" quickly pulling the rest down. This happened to a family member on their yacht, and the result was one battery exploded!

The only way is to turn everything off, disconnect one terminal from each battery, and leave them for half an hour (or more) before testing the voltages. If one is showing appreciably less than the others leave it disconnected, and insulate the terminal(s).

nb Chuffed said...

Dave drilled some holes in the floor below our fridge a few years ago (taking care they didn't coincide with the position of the feet). The draught from the bilge really helped the fridge, though we still had to change the batteries a few weeks later!

Oakie said...

Not sure if you read Derwent6 blog, but they changed over to all lithium batteries in May this year and it is all in detail starting with:-


It goes on for several days after that. They did not say how much, but I bet it was an arm and a leg twice over! Not that I think you should change now, but it is interesting and in minute detail.