Thank you thank you thank you.
If it wasn’t for you I wouldn’t have just found out something I have really needed to know (and worried about) for a long time.
I started writing a post about long term results of our changing to a different domestic battery type in 2010. We bought three Numax CXV 113Ah batteries which are 15% dearer than standard open cell types. This was a bit of an act of faith based on manufacturers claim of much longer battery life. Was I a victim of advertising hype? Did I waste my money?
A year ago I wrote that 2012 should be the decider one way or the other. So here we are in 2013 and I was writing that they did really seem to be lasting better. Then I thought I’d try to check my technical facts on these batteries. Previous attempts at this led me nowhere as none of the technical sheets or advertising specs gave anything away. Maybe it was snake oil. Maybe I had bought a pig in a poke.
Anyway my desire not to give you misinformation got me to have one last try, and just as I was giving up I found the vital snippet. It turns out that these batteries have plates that contain Silver and Calcium plus of course being mostly lead. Being none the wiser, I looked up Silver Calcium batteries. Bingo. Lots of info.
Now fitted as standard by Ford amongst others. Silver Calcium batteries have a much lower self discharge rate and a much longer life than standard open cell lead acid batteries. Ford reckon on 6 years in a car. They also lose a lot less water (by a factor of ten times) But here’s the bit of information I really needed and didn’t know, and it will significantly change how we manage these batteries. The charging voltage tolerance is increased from the usual 14.4v to 14.8 volts.
Well woopy woo I hear you say. What difference does that make? I’ll tell you what difference it makes. It makes me want to weep for all the wasted worry we have had about overcharging. It means I don’t have to keep worrying every day when our alternator voltage creeps up beyond 14.4 after some hours cruising. Full of battery boiling paranoia, we watch the Smartgauge like a hawk until it goes into error mode because of “over voltage”. Then we turn the fridge up higher to soak away the extra voltage, and still I worry that we might be damaging the batteries because they are sealed and can’t be topped up if the electrolyte boils off.
So it turns out that far from damaging the batteries, it would actually be good for the voltage to rise up to approaching 14.8. The batteries would get more fully charged. Doh. I had even built and installed an alarm that beeped when we rose above 14.5. I spent hours on it. Now I’ll have to strip that out. Also I’ll have to change the Smartgauge settings to reflect the max voltage.
So back to my original idea for this post. Most normal open cell batteries have a predicted life of about 250 charge discharge cycles. I reckon we must be well over the 300 cycle mark now and four months to go on the three year (rather than two year) guarantee. So how are we doing?
I suppose the first thing to say is that based on past experience, our older set of open cell types- same make, different model, - were giving up the ghost at this stage and suffering a lot of self discharge when left in the cold weather and of course ruuning down quickly in use. Our recent discovery that our solar panel had not been connected for at least two months this winter exposed our CXV batteries to the same conditions for self discharge, so how did they manage? Not badly is the answer. There was some self discharge, but very small in comparison.
On a broader front, the CXVs seem to be holding up well. Although I don’t think they have as much capacity now as they started with, they are still up to about 65 - 70% on the smartgauge after a 16 hour overnight stop using the normal fridge, lights, water pump, a bit of telly / radio. I won’t start worrying until that drops nearer to 50%.
So that shows they work does it?
Well we can’t really be sure how much better they are than the old ones because these days we look after our batteries better. Having a solar panel makes a lot of difference. Our batteries really do get charged to 100% very regularly, even after short cruising days, what the alternator doesn’t achieve the solar panel finishes off, and of course gives us a boost after sunrise before we get up. My new solar panel ammeter (which works-hooray!) shows that even on a sunny February afternoon with the sun low in the sky, we can get 4 or more amps out of the panel. On a long summer day, that would equate to a lot of amp hours.
I was going to write that the downside was that you had to do something about preventing your alternator from charging at too high a voltage, but now that problem seems to have disappeared. Thank you thank you thank you.
The big question is, next time would I buy these batteries again, even though they cost more? The answer has to be YES. a) because they really do seem to be lasting longer, and b) because topping up the old ones was a pain due to the fact that they had so little headroom over them. I suppose there is also a c) because they are sealed, there should be no potentially dangerous hydrogen escaping to cause an fire or an explosion in the engine bay or risk of acid spillage. Oh and a d) because my alternator is unlikely to produce a voltage high enough to overcharge them.