what size inverter?

sohappy

looking fo some advice please, I want to hook up an inverter in the back of a van to be able to plug in a couple of battery chargers to be able to charge the batteries for power tools, ie.drill ect, My thinking was,I would get a split charge 30amp relay kit, hooked up to an extra 12v battery in the back of the van ,the relay kit only allows the extra battery to draw charge when the vehicle is running and breaks the circut when the vans not running so as not to drain the vehicle battery, ,i would hook up an inverter to the spare battery,

What size inverter should i use to run a couple of cordless drill chargers?
What size spare battery should I fit?

this is the type of relay kit i was thinking of using
http://cgi.ebay.ie/SPLIT-CHARGE-RELAY-KIT-12V-30AMP-SELF-SWITCHING-/110737128922?pt=UK_Campervan_Caravan_Accessories&hash=item19c8727dda

Bruthal

You could connect the invertor to the vans own battery, through the relay. So the invertor will only operate when the van is running. No need for the second battery at all.

A 350 watt invertor in argos for €20 would be more than enough for a couple of cordless battery chargers with plenty to spare.

red sean

Careful Sohappy. Most inverters selling cheap are not true sinewave generators and can destroy battery chargers in a very short time. Do your homework or you may not be so happy!
I got caught with an aldi 450w one that burnt out a drill charger and a laptop charger. Expensive lesson!

Bruthal

Most are not sine wave alright. Its a bit dearer for them.

sohappy

thanks for the replies, I guess the one in the link below is the type im looking for,? so 300w should be plenty for a couple of powertool chargers?

http://cgi.ebay.ie/300W-Pure-Sine-Wave-Power-Inverter-12VDC-230VAC-/270801880519?pt=UK_In_Car_Technology&hash=item3f0d0cc5c7

Bruthal

sohappy wrote: »

thanks for the replies, I guess the one in the link below is the type im looking for,? so 300w should be plenty for a couple of powertool chargers?

http://cgi.ebay.ie/300W-Pure-Sine-Wave-Power-Inverter-12VDC-230VAC-/270801880519?pt=UK_In_Car_Technology&hash=item3f0d0cc5c7

Yes more than enough in that one, and the sine wave will be better. You dont need the second battery either, connect direct to van battery through a 30 amp fuse and holder you can get in halfords etc, and tgrough the relay setup if you want to ensure it can only be used when ignition is on.

6 square flex cable would be ideal for the 12v supply cable to the invertor if required.

sohappy

thanks robbie, so if the van is parked and I have 2 chargers running for an hour they wont drain the battery?
thats why I thought I would need the second Battery and that then would charge up when the vans running,

Bruthal

sohappy wrote: »

thanks robbie, so if the van is parked and I have 2 chargers running for an hour they wont drain the battery?
thats why I thought I would need the second Battery and that then would charge up when the vans running,

Yes should be ok. Although your original idea would work well, you would only be using power from the second battery while charging when the van is not running, and while it is running, the batteries are being charged anyway.

The way to work out how much you will drain to fully charge a drill battery would be to just look at the drill battery capacity. A 2 AH 12v drill battery will take 2 AH`s from the van battery to fully charge the drill battery, although for a lithium ion battery, this will be about 1.6AH`s, as the drills using them only let them discharge to 20%, to protect the battery, which is why drills using them type batteries suddenly stop when the battery needs recharging.

If the drill battery was a 2 AH 24 volt one, then it will take 4 AH`s from the van battery to fully charge it, and about 10 or 20% more because the invertor is not 100% efficient, and neither is the charging process.

So the second battery setup would work well, and be better overall, especially if you get a deep discharge battery, which car batteries are not. But for small drill batteries, the vans own battery should do for an hours charging of 2 batteries. But if regularly doing it with the engine off, the second battery might be better alright.

sohappy

thanks for your help,