Battery charging modifications.

We’ve all been there; not moving very much so the batteries are not getting a thorough charge. We’ve got four 100 Ah AGM batteries which I installed about 2½ years ago and they are still OK if not in the first flush of youth. They are charged from the two engine alternators through a Sterling A-B four stage charger which performs well, but recently the battery bank has rarely reached 100%.

If we have heavy usage in the evening, maybe running the hard-drive recorder as well as the TV, charging the laptop and with the fridge and freezer running overnight, the voltage can often drop to below 12.25 volts. Not a problem with the AGM batteries, they are far more resilient than standard flooded lead acid. But those of you with diesel-fired heaters, Eberspacher, Webasto, Mikuni et al will know that they are power-hungry on start-up, drawing maybe 13 amps initially, and they are very sensitive to low voltage so may fail to start as the voltage drops due to the amps being drawn.

Our old but generally reliable Eberspacher starts at 08:00 on a timer and runs for an hour to provide hot water for abluting, but we’ve had this situation a couple of time recently, easily fixed by firing up the donk for 15 minutes but a nuisance none the less.

When I swapped the old lead acid batteries for the AGM ones I had one that was only 6 months old and in good condition, and space to keep it in the battery bay. So I did and it’s been sitting there since, getting a top-up charge once a month but otherwise enjoying a life of leisure. So I thought what about dedicating that one battery to the heater and nothing else, isolated from the main bank. Obviously it would need to be charged more often than once a month, so today I’ve fitted a Voltage Sensitive Relay between it and the main domestic bank so it will charge when the engine is running and the alternators are pushing out the amps, but will be disconnected when the voltage drops below 12.8 volts.
That’s the chap, below the Sterling charge controller.
It will actually pass 140 amps, far more than normally required, and both feeds to and from the batteries are protected by fuses. It trips in when the voltage on the main domestic bank rises to 13.3 volts, and drops out when the combined voltage falls to 12.8. The power supply for the Eberspacher, and nothing else, is drawn from the single lead acid battery. It remains to be seen whether it will be effective or not, but there’s no reason why it shouldn’t.

I got the unit and a fitting kit including cable, fuses, battery clamps and comprehensive instructions from a company called Simply Split Charge, delivered within a couple of days.

Thanks all for the kind comments regarding the saloon doors; Kath, it’s not real stained glass of course. Stick-on lead strip and translucent glass paint. But it looks good if you don’t get too close…

We’ve reduced Meg’s steroid dosage today, she’s now on 10mg instead of 20mg. Hopefully she’ll still be OK on the lower dose. She’s going back to the vet on Friday morning, and I think Sam will be pleased with her progress.

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