 | Home > Technical > New battery required (and possible gremlins) |
 
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971   
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a) it is possible, there are two ways. The more accurate way (but it's a bit of a fiddle) is to loosen the negative terminal of the battery, clamp one lead of a multimeter set to DC amps on the battery and the other on the lead, then disconnect the lead. That will then measure any current being drawn by the vehicle up to the limit of your meter. The issue is that it's fiddly, you can easily accidentally disconnect the battery and set the alarm off and if you turn the ignition on with this setup in place you'll blow the fuse, normally 10A, in your meter. The other way to do it is with a DC clamp ammeter. This is much less accurate but can give you an idea of what's going on without having to insert anything in to the current path.
Here is a video on how to to the first method: The second method can be done with something like this: https://cpc.farnell.com/tenma/72-7224/clam...dp/IN05110 - note that many are available that only measure AC amps and that's not much good. My Defender draws about 45mA sitting idle, most of that is the Ultragauge. b) single or dual battery. The standard battery size for a TD5 is a 019 battery. I use a flooded Varta Silver Dynamic: https://www.tayna.co.uk/car-batteries/varta/h3/ for both starting and camping. You can *just* fit a pair of them in the battery box but it's tight. AGM batteries do cycle a bit better than flooded batteries, Odysseys in particular, but they're not so much better to justify the price IMO unless you really need the additional capacity. In which case I'd use lithium because they're better value as they last longer. You only need more battery capacity if you're running lots of things when parked. If you're not, then there's no need to spend the money. For my camping battery I use a Victron Cyrix CT 230A split charge relay to charge it, it's robust and it works. The rating is higher than I need for charging however it gives me the option to jump start myself. I then use a Victron BMV 712 Smart to monitor the second battery, which gives you a local display and also all the information over a bluetooth link to your phone. Monitoring a battery's state of charge by looking at the voltage is about as useful as licking it. State of charge meters aren't great but they're the best/least bad you can get. You get a screen like this which will tell you current in/out, state of charge and time remaining.  Click image to enlarge There is a lot to be said for completely fogetting about a split charge system - lorries don't bother. A battery's cranking rating doesn't drop much until you get below a 50% state of charge and you shouldn't be running a battery below 50% state of charge because it significantly shortens the lifespan. If you have two 100Ah batteries like the Vartas above that are separated when parked you have total usable capacity of 50Ah for camping and 800CCA for starting. If you have them permanently combined without a split charge system then you have a total of 100Ah (half of the nominal 200Ah capacity) for camping then 1600CCA for starting. So the system is simpler and better for both activities. The issue is that if you make a mistake and leave your fridge running for a week then both batteries will be flat and you're stuffed. A side note on Optimas and Odysseys. I do not see the point of Optimas. I've heard a lot of stories about premature failures and experienced one myself. If you're going for an expensive battery I think the Odyssey is a better option. They are rated down to a lower depth of discharge than most batteries, 30% instead of 50%, so whilst the headline figure is lower they have the same usable capacity. (70% usable capacity in a ~70Ah battery is the same as 50% usable capacity in a 100Ah battery). That said, I would prefer to just swap out a cheap (ish) flooded battery every now and then. A side note on fridges. Consumption varies massively between brands and depending on how you use your fridge. I used to have a 40l Snomaster than used the same amount of energy to keep itself at 5C that my replacement Waeco does to keep one (bigger) compartment at 5C and the other (smaller) compartment at -10C. By using the freezer half of the Waeco to freeze a couple of bottles of water to -22C then turning the freezer off, I've managed to keep the fridge half cold whilst only using 5Ah out of a battery over the course of 4 days. The flip side of it is that I've used 30Ah overnight (about 15 hours) in a hot car in sun in a hot country. A side note on wiring. Whatever you do, make sure it's fused and labelled. I've had to help too many people with electrics that don't work or have stopped working half way througha trip only to find that the wiring makes no sense and isn't fused. Nene Overland (or their workshop) want shooting for the quality of the wiring they do. It's dangerously  . Given that they seem to excel at being phoenixes I don't think death would hold them up for too long but it's a start.
DC/DC chargers do have a place but they're few and far between. That's a rant for another time. Edit: oh, and if you want a held looking for current draw I'm not far away from you if you're in Cambridge and I'm happy to help. |
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9th Nov 2018 3:08pm |
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| stigomery Member Since: 10 May 2016 Location: Cambridge Posts: 277 
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Wow... thanks!
This is hugely helpful... Let me get inside the battery box this weekend and have a fiddle to see if I can figure out if there is current drain somewhere and start from there... for now I have my trusty 20Ah lithium jump starter battery pack thingy which has proven invaluable over the past 6 months... amazing and it just sits behind the passenger seat until needed! Stig |
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9th Nov 2018 3:35pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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Ah, which jump starter thing have you got and does it work as hoped?
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9th Nov 2018 6:09pm |
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