Inverters & battery chargers

most intelligent chargers employ a delta peak cut off so charging in batches should make no difference, your other option is a radio control model charger running directly off of 12V

As long as it doesn't discharge batteries to a preset level at switch on you should be ok.

Thanks Dave - but how would I know?

I don't know the answer to that question, but one possible solution is to buy an additional battery of the "deep cycle" type, sometimes called a "leisure" or "marine" battery. They are used in caravans and camper vans, so you should find it easy to install one in your van, charged from the alternator by a "split charging circuit" which ensures the main vehicle battery is always kept fully charged.

You could then run the inverter directly from the deep cycle battery, leaving it on all the time. Unlike a normal car or van battery, the deep cycle battery will tolerate deep discharging (hence its name) so you have no worries about leaving it on.

When the van's engine is running, both the van battery and the deep cycle battery will be recharged, with the van battery always having priority thanks to the split charging circuit.

Deep cycle batteries generally cost about 50% more than a similarly sized car or van battery. You can buy a split charging relay on eBay from around £20. There are kits for vans such as Transit, Ducato etc.

I would be inclined to be sceptical - we took an inverter on holiday with us once when we had a camera which used a Li-ion cell and needed a 'mains to

most inverters have a cut of that stops them working below a certain voltage to prevent deep discharge

So your inverter will change the van's DC to AC so that the drill's charger can change the AC back to DC. Surely there must be a simpler solution?

Mad I know, but I don't know another way to do it?

if its a Nicd or NiMh then there are so many options, modellers have been using auto chargers for years, any model shop will sell you a similar charger to this one below all depends on the voltage of your drill how cheap you can get one for

Possibly. Most NiMH/NiCd fast chargers rely upon two charge limiting mechanisms. One, the primary one, detects a small depression in voltage when charge is complete.. The second detects battery temperature rise.

Both depend upon a relatively stable environment. In a van where the battery (and for cheap inverters) the inverter voltage will vary and the temperature will also likely vary neither of these may work any too well.

The temperature rise is the most reliable - but by the time it is detected the battery has been harmed to some degree. Most dV (voltage depression) detection fails when faced with intermittent charge periods, varying environmental temperature and fluctuating and noisy supply voltage.

Thank you for that, but it doesn't in any way affect the sheer brilliance of my idea. ;-)

Not if the voltage of the Makita battery is greater than 12?

there are plenty of 12v chargers that will charge a battery of more than 12v

The only Makita charger I have has a LED which flashes in different ways to tell you what's going on. The graphics aren't that clear so you might have to refer to the instruction book to see what they actually mean.

Yup mine has various LED's which are 'on' or 'flash', what prompted me to ask was that mine had an LED signal warning that the battery was overheating.

So there's even less of a problem?

Thanks, things just get better and better!

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "The Medway Handyman" saying something like:

There is a Makita charger that runs off 12V - costs a bit, mind.

The cigarette lighter socket in the 2 volkswagen vans I've owned isn't switched with the ignition - continuous power available.

Obviously having a charger plugged in discharges the vehicle battery, but not particularly rapidly.

Cordless tool chargers probably draw around 50W whilst charging (for say 30 minutes) - the equivalent of one headlight. Most modern vehicles with a good condition battery, you could leave the headlights on all day and still not adversely affect its starting.

So maybe consider having an unswitched cigarette lighter socket wired in?

just look at different source of supplier you might need a bit of DIY to hook them up but they will work, I fast charge mine with a model car/plane charger 2 nails and a plastic g clamp, it auto cuts off and you can vary the charge rate to suit how quick you charge them