I'm intending to DIY a solution for the camper where I have a 12V lead to the leisure batteries which can do two things:
(1) Connect the kick ass tyre pump (too kick ass for a cigar lighter socket)
(2) Connect a proposed purchase of a Supercharger battery charger (
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) to recharge the batteries when away from hookup, and possibly also drive an inverter by feeding power into the batteries whilst using the inverter to take power out ( see
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).
To do this easily I need a lead from the leisure batteries which can be easily connected or disconnected from either device, and can live near a window not under loads of gubbins where the batteries are hidden.
So - snap connector for 12V leads, one female and two males, female preferably with some kind of blanking plug or cover for when not in use.
XLRs are very good for this sort of thing. also though you might also think about making it all switchable via a relay or something. I don't like the idea of loose wires dangling about.
Have you considered a normal generator? This would avoid the power losses in the inverter for mains power whilst the machine is running. You can charge your batteries and use the 240 supply simultaneously.
I'm sure a Honda would be quieter than the Supercharger. The latter appears to not quote a sound output level, and there is no video with someone talking over the machine so you can make a judgement. I can't find anything on You Tube. I'm really very suspicious of the claim that a 49cc engine can be 'super quiet'.
The Supercharger claims that it needs minutes, not hours, to charge your batteries. Leisure batteries cannot in my experience be charged at such high rates. To repeatedly put 50A into a 110Ah leisure battery for an hour would kill it in no time, and it would be less than half-charged (much less: the process isn't 100% efficient and the charge rate would drop rapidly after the first few minutes. Obviously if you used the supercharger to charge a bank of batteries simultaneously the high charge rate would be less of a problem.
A vehicle alternator will never in my experience charge your battery as fully as an 'intelligent' charger. Maybe the Supercharger uses a modified alternator, I don't know.
The Supercharger claim, "The advantage you have with this method is that the SUPERCHARGER can quickly and effortlessly replace any used battery power in minutes, whilst mr generator man is running his generator for hour upon hour to watch television and only getting 8.3 amps12 volt power MAXIMUM from his generator........ WHILST ANNOYING EVERYONE!!!!!." is disingenuous because anyone using a mains voltage generator would also use a decent battery charger which would easily produce as high a charge current as a leisure battery will happily take. It would be just stupid to run an 800W genny just to power a 30W TV set and put 100W into the battery when a battery charger would increase the charge rate to any figure you desired.
If it's any help to you, here's what I do. I use a Honda 20i 1.6kW genny (£1,100 new, much cheaper S/H) which (if there are neighbours) I take
30m away from the vans, where it is scarcely audible. I point the exhaust away from the vans by the way, and if there's a wall I use that as a sound screen. I have two 24V 15A intelligent chargers. Each charges a 110Ah 24V battery pair. There is also a 24V 8A charger for the disability scooter, and a 24/12 converter for the 12V circuits. So I'm getting a peak of about 950W of charge, which drops down as the batteries charge up. While the genny's running I can use the mains for phone chargers, TV set, TV recorder, small vacuum cleaner, expelair, etc.
You could do something similar but with less power with a Honda 10i genny very cheaply. I have seen good S/H ones for sale for £300. People buy one then decide they need the 20i, so bargains are there.
Bear in mind that charge rates are extremely sensitive to cable/connector resistance. A long cable will drop the charge rate a lot.
If you need an inverter make sure it's a genuine sine wave one.
Thanks - if I had room to pack a "suitcase generator" then that would be my first option. However I don't have a convenient space inside the van with enough height to take a traditional genny.
I don't want to carry a generator in the living area and have to offload it and chain it to something every time we stop for the night.
The attraction of this one is the compact nature. The possible downside is the 12V only.
I have a bank of two 110Ah leisure batteries so they should hopefully not be too stressed by the charge rate, although to top them up from 50% discharge (roughly 100 Ah) would presumably take 50 amps for 2 hours at maximum efficiency.
On a simple "volts * amps = watts" a 12v 50 amp alternator is presumably chucking out around 600 watts which is pretty tiny compared to most suitcase generators - I did see a 700w Honda generator a few years back but they are not made any more and I have so far not managed to find one on eBay.
So not ideal, but I haven't found another compact generator so far.
It would actually take much longer. The output voltage of a normal alternator is safely low (the Supercharger quotes 14.4V). This means that charge rates are relatively low right through the charging process. The terminal voltage of a 12V battery rises during charging and before very long it approaches 14.2V. The charge rate is determined by ohm's law, the figures being 14.4V - 14.2V = 0.2V and the internal resistance of the battery plus the resistance of the cables, plugs, and fuses. The internal resistance of leisure batteries is higher than normal car batteries. So you end up with something like 0.2 over 0.2, or 1A. At that point the battery is probably 75% charged,and that would be fine if the alternator was in a vehicle because over time the battery will get almost fully charged, and it will never risk overcharging. Remember, a normal 'start' only takes 5 to 10Ah, so that's soon put back, and any moving load is automatically carried by the alternator. Vehicle alternators are not designed to charge from near-flat in a hurry. They will get a battery up to a reasonable state, maybe 35% charged, quite quickly, but after that it's very very slow.
So a vehicle alternator is no good really for the sort of rapid charge to finality you need for your application. This might illustrate it. When I've been wild camping and I haven't used the genny the vehicle will start to charge the batteries (which will be down to maybe 23.5V) when I set off for home. The vehicle battery will initially take 10A and this will rapidly drop to about 250mA. The two sets of aux batteries will both start at about 25A, but after an hour this will be down to about 8A, and by the time I get home (after maybe four hours) it will be
3A. I then connect the house mains and both aux batteries will take 16A from the 'smart' chargers, showing that they are nowhere near fully charged. It will be the next morning before the charge rate drops to
100mA, meaning that the batteries are fully charged. How long would it take for a vehicle alternator to fully charge the batteries? I think it would be a trip from Land's End to John o' Groats! When I've moved from one site to another (neither with mains) perhaps travelling for 45 minutes, the amount of battery charge gained makes very little difference.
I should explain that 'smart' chargers overcome these problems by battery monitoring and by having a series of charging stages. They start with a very high voltage (about 17V for a 12V battery) which gives a fast but safe charge rate. Then they automatically reduce their voltage, and when the battery says it's fully charged they just give it about 100mA.
Feed 'Honda 10i' into ebay. There's dozens.
You really would be much better off using a mains genny (true sine output though; this is important) and a smart charger. That way you will really charge your batteries significantly in two hours. Take a look at Numax and Waeco.
FWIW my prejudice would be exactly the same as Bill's.
Although my requirements are a bit different. I use the Machine Mart smallest inverter generator (Honda clone) to charge my Renault Master horse lorry when we manage to let the battery go flat, using a "high current + boost option" battery charger. Half an hour or so at ~ 20 amps, then add the boost of ~ 100 amps and it starts.
I think I have used my ingenuity to the full (who knows?) but the Honda-a- likes (such as Kipor) don't seem to want to fit. A lot of people seem to use the gas storage locker after they have had a tank fitted, or they have a garage under the fixed bed. We have normal gas bottles and no fixed bed.
I did meet someone with an old Honda 650w generator which seemed much more compact - this was the one I was having trouble finding.
I am tending towards a mains generator because of the limitations (and the misleading information) associated with the Supercharger. Just need to find one the correct size.
Some of them are quite noisy, especially on full load (which is how you'll use it). Last time I bought one I checked out a couple that were temptingly cheap, but they were significantly more noisy than the Honda.
Older ones make more noise, so if you get a S/H one I should have a listen to it first.
Don't use a generator plus a standard battery charger, even a high output one. That's hardly any better than a vehicle alternator. You do need to get a smart charger, and it should be overspecced, and in my opinion should have a built-in fan.
Twenty years ago I imagined a big fat 30A charger of the 'garage' type would be all I'd need. I soon found out I was wrong. I still have the charger; it's excellent for charging a car battery overnight or for whacking in a partial charge very quickly. But it was no use for trying to fully charge a battery in the shortest possible time. Even on the fastest charge rate the charge would have tapered off to about 5A after an hour.
Of course with basic chargers a great deal depends on the mains voltage. A charger that is nominally 240V AC input and 14.8V DC output will, when run from a generator that might have a 220V AC output (as many do), will only have an output voltage of 13.6V, which is almost useless.
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