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Discussion Starter #1
Hi all,

I'm in the process of replacing the dead leisure battery on my T5 camper. I've got a 250W solar panel on the roof, so am going for AGM batteries this time around.

I decided to get an extra battery, so I would have 2 leisure batteries to double my capacity for off grid camping.

However, my electrician is concerned that having three batteries running off the alternator could be dangerous, and that I ought to upgrade the alternator. So Q1 is, is this necessary? Does anyone here have any experience of this? Apparently Californias have an alternator rated at 180 W (?) for this reason?

Q2 is, would it be possible to just rely on the solar panel to charge the 2 batteries and not have the alternator connected at all? I've been trying to understand the arithmetic of amps and A-h capacities, and to me it looks feasible, but I'm really no expert at all. The problem is the variability of sunshine of course, and the reality that I consume more power in the winter when the sun is least.
 

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Q2 is, would it be possible to just rely on the solar panel to charge the 2 batteries and not have the alternator connected at all? I've been trying to understand the arithmetic of amps and A-h capacities, and to me it looks feasible, but I'm really no expert at all. The problem is the variability of sunshine of course, and the reality that I consume more power in the winter when the sun is least.
Whether it's feasible depends on how much power you use. If you use - on average - more power than the 250W panel generates, then it's not a viable solution, but as you don't say how much you use, nobody can answer the question!

However... I would think that a 250W panel would probably be adequate for most users for 3-season use. I use a 100W panel 3-seasons without any great issues - I do have split charge but if I camp in the same place for several days that doesn't help, of course.

Part of the reason is that my biggest consumer of power is the fridge, and that takes most power when the sun is out and it's hot. It certainly runs more during the day than during the night, which obviously suits the solar output well.
 

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Discussion Starter #3
Good point re usage. I'm not a TV camper, so usage is the fridge (40W), lights (not sure) and in winter the fan for a diesel heater (about 30W I think but not on for hours like the fridge). When my first leisure battery was working I could get two nights out of it unplugged.
 

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Makes me wonder if your first battery was not up to spec - you do occasionally get batteries with internal damage (probably incurred in transit). My use is about the same as yours, and I get at least 2 days with only a 100W panel.
 

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Actually, I'm not giving the full history here. Before I had the solar panel the battery gave me 2 days, but there were a couple of times when it ran completely dead, and I think this knackered the battery, as it has never had the same lifetime since.

After these events I fitted the solar panel. With the solar panel what I found was that the battery would recharge during the day, but die overnight, especially when the fridge was running on and off all we had the heater running.

Which makes me realise that I am starting to answer my own question, so thanks for challenging me!
 
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