Submitted:Monday, Nov 19, 2012 at 08:24
Member - John and Val replied:
The basic problem is that if you want to get say 30Ah average out of your battery each day you need to put 30Ah average into it each day (plus a bit to cover inefficiencies). Your options are a mains charger maybe driven by a generator, a dc-dc charger driven by the vehicle alternator, direct connection to the vehicle battery with suitable switching so it is only connected when charging voltages are available, or solar with a suitable controller.
Charging from the mains or a generator via a charger is a good way to go, BUT takes time – your 8 amp charger (if it does actually deliver a continuous 8A) will take about 4 hours to pump in the 30Ah you need each day. In practice an 8A charger may start off delivering 8 amps, but will probably taper down so that after an hour or two is only delivering 4 or 5 amps. (Many small generators also have in inbuilt charger for batteries, but usually these are pretty poor, without good regulation and can deliver excessive voltages towards the end of charging; this can damage batteries.)
If you do opt for a charger running from the 240V generator, I’d go to a bigger charger – maybe a 20 or 30 amp one so that you can meet your daily needs by running the generator for only an hour or two.
Depending on how much driving you do on an average day, and how many consecutive days you don’t drive, you may be better off installing a dc-dc charger and using the vehicle alternator to supply your charging current. It’s important to use heavy wiring from the engine bay to the charger (which should be close to the van battery). Also, before going up that path, check that your alternator has enough reserve capacity to run the charger. (These chargers effectively draw extra current from the alternator and use that extra energy to deliver a higher voltage to the battery, forcing higher current into it. With 20A flowing out to the battery, the input current to the charger will be at least 25A, and more if it also has to compensate for voltage losses in the wiring. This can get quite out of hand as the increased current results in more voltage loss due to resistance in the wiring, leading to it drawing more current, less voltages…….)
If you do plan to go solar in the future, suggest it’s worth considering something such as the Ctek D250S or Redarc BCD1225 which provide in one package the switching gear, a dc-dc charger and a MPPT solar controller.
For the moment, I’d opt for a bigger 240V charger that’s suitable for your AGM battery.
|J and V|
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein
Blog Owners Reply