using power tool batteries !

[promomdis]

Hi Folks - yep another newbie here

Got an idea for my camper van and wanted some experts to state how stupid it is or realistic

I want use a 12v power tool battery as I have a few for my power drill . I want to use it to run the lights and fan in the back of a van. I have one charger.

My question is would it be possible to use a charger to manually/automatically systematically charge each battery once the van is connected to a 240v electrical hook up. Then a means to switch to then draw the power from a battery or the batteries if they are in series- . So the issue is to not disconnect from the power to be able to charge the batteries.

Anyway I will keep an eye out for some advice.

 

[Arouse1973]

Yes you can no problem. You need a battery charger with power path control. This basically charges the battery whilst also supplying power to the lights and fan. When the power is removed then the batteries take over. How you connect the battery packs up is down to you
Adam

 

[dave9]

Yes, simple run a wire from each charger contact to the respective battery contact, or easier still would probably be to run the wires from the charger contacts (open it and solder to the circuit board) out to the lights and fan.

You would need to measure whether the charger drains the battery while connected, when the charger has no AC mains input.

Frankly with a vehicle having a much higher capacity primary/starter battery, I would just use that and have a low voltage cutoff so it doesn't accidentally run the battery down too low.

You'd need to do this for each battery. There's no way to automate hooking one charger up to multiple batteries at once unless it has a separate bay and subcircuit for multiple batteries. Well with some very crude chargers that are just VA sources, that type could charge multiple batteries in parallel very slowly but I wouldn't even bother with that kind of charger.

 

[promomdis]

cheers guy interesting read. I think the main battery is some metres away, and I also wanted these as a backup.
so a charger with apath control - ebay ? manually switch to each battery as the charge green light come on saying full ! was thinking of taking out og the power drill case to layout in a better format ? is that as simple as it seems.

I have been reading that I cannot stack these batteries up to 14v and use to charge other 12 v batteries ? I will dig around this forum to see if there are any other hacks....again thanks fgor the ideas...appreciated

 

[dave9]

I can't understand what you mean.

Main battery being meters away is not a problem. They make pieces of wire much longer than this !

No idea what Arouse meant by a path control. It's not a term I'd associate with any charger I've seen.

What does "taking out og the power drill case to layout" mean?

What does "cannot stack these batteries up to 14V" mean?

You have been far too vague, to the point of this being a hopeless topic. We don't even know if your batteries are Li-Ion and if so, if there is a over-discharge protection circuit built in so you can't drain them too low and damage them.

ALL the details matter.

 

[Arouse1973]

cheers guy interesting read. I think the main battery is some metres away, and I also wanted these as a backup.
so a charger with apath control - ebay ? manually switch to each battery as the charge green light come on saying full ! was thinking of taking out og the power drill case to layout in a better format ? is that as simple as it seems.

I have been reading that I cannot stack these batteries up to 14v and use to charge other 12 v batteries ? I will dig around this forum to see if there are any other hacks....again thanks fgor the ideas...appreciated

Looks like our resident battery charging expert is taking the lead here. I'll leave you in his hands
Adam

 

[kellys_eye]

I'm not sure I recognise the need for the system as the OP wants it to be.....

The lights/fan can't consume more than a couple of amp-hours (the amount that a simple tool battery can hold) and a couple of amp-hours drain on the main batteries is almost negligible as far as discharging them is concerned (around 1/80th of their total capacity perhaps?).

Fitting a small trickle charger to the main batteries would save you messing about with rearranging wiring, fitting battery holders and other 'faffing about'.

If the vehicle is parked outdoors i.e. not under cover, then consider a simple solar mat on the roof of the vehicle and connected (via a trickle charge circuit) to the main battery. Such systems are common on small vessels (yachts) and you can cobble one together from eBay bit'sn'pieces rather cheaply.

 

[dave9]

^ That's just it, we don't know if all the pieces are compatible. You can get a 12V computer fan that draws 100mA, or a radiator fan that draws 5A. The original incandescent overhead lights might be around 1A each, or LED replacements roughly 150mA at the same lumen output, times the # of lights.

The battery could be an ancient Ni-Cad that started new at 1.4Ah and is now old and realized capacity under 1Ah, or a brand new 9Ah Li-Ion. It seems unlikely someone would buy a new drill, only to not be able to use it because the batteries are somewhere else in service, so I'd sooner suspect old low capacity batteries.

Assuming there's nothing wrong with the van, still operable, it could merely be ran every couple days to top off the primary battery.

Then again, a 2nd lead acid battery could be put in the back, or forget about the drill batteries and just get a Li-Ion pack, like one of those USB portable power packs, which you can charge with the same method you're going to want for a phone.