Build/adapt my own charger?

Adam Frisch FSF · August 12, 2016

So, I have this new to me Aaton 35-III cam and it uses 12V onboards with XLR connectors. Can't really find the original charger for these, so I thought I'd perhaps adapt my own. Camera takes 10-14V, so I'm assuming the best would be to find a 14V charger to charge the batteries with, right? I'm a bit clueless when it comes to electrical stuff, but I seem to recall from my science classes that to charge something to 12V, the charger needs to be more than that. So, here are some questions:

1. For a 12V battery, would 14v charger be best?

2. Would it charger quicker with a higher voltage, i.e. a 16V charger? Would I risk blowing something?

3. What would a good amp be for the charger, so I don't blow them up? They're probably around 20-40Wh these batteries. What's a good rule of thumb here?

Appreciate any insights.

Gregg MacPherson · August 12, 2016

I'm not a trained tech, but there are some easy answers to some of that.

A 10 cell 12V NiCad pack has a full charge heading towards 14V. A "12V" charger will supply the voltage that the bat needs.

Some quite good sounding bat chargers ex China on eBay, like this one, NiCad or NIMhi, various voltages, auto switch to trickle charg, really cheap...

http://www.ebay.com/itm/231757560127?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT#ht_4188wt_1366

Someone on the forum might have used one and commented recently. Maybe the Eclair subforum...

Did the Aaton 35 come standard with NiMhi. If you are recelling, I would go NiMhi. NiCads are apain to look after if you are only using them occassionally.

Phil Rhodes · August 12, 2016

Careful, folks, there's a lot more to do with this than just "find the right voltage." A reasonable charger will need to know the capacity of the battery, the chemistry (nickel cadmium, nickel metal hydride, lithium ion, etc) and the number of cells, which can be worked out given the chemistry and the specified voltage. A 14.4V NiCd, for instance, will be 12 cells, and will have a rating for capacity in ampere-hours. 20 watt-hours at 12 volts implies a capacity close to 2Ah (2Ax12V=24Wh). 40 watt-hours implies double that, so you really need to know more about them.

The charger mentioned above appears to support only two charge rates, 1A and 2A. Charging NiCd at the same rate as its capacity (that is, 2A charge on a 2Ah pack) is very hard on the cells, so if they are close to 20Wh use the one-amp rate and accept it'll take two hours or a bit more to charge.

My go-to solution for this sort of thing is something like this. They're very flexible and can be used to charge more or less anything from a cellphone battery to a full size camera pack and provide a lot of diagnostic information which can be quite informative about how well the battery is performing. They're cheap enough to buy several for simultaneous charging. There are a lot of options, but the menus are no more complex than most cameras.

P

Gregg MacPherson · August 12, 2016

Is the cameras safe operating voltage 10-14V? Then won't 12 cells be too much? Fully charged they would be about 17V, yes. i know my "12 V" 10 cell NiCads were 14V on a fresh charge. We could wait for some advice from a tech who understands the camera requirements and the battery systems.

Phil, do you think that the charger I pointed to, charging at 1A, for a 12V 2Ah NmHi battery, is too fast?

The charger you pointed to is better and more usefull. I didn't look around for one. Just pointed to one that someone on the forum had used recently.

Edited August 12, 2016 by Gregg MacPherson

Phil Rhodes · August 12, 2016

Is the cameras safe operating voltage 10-14V? Then won't 12 cells be too much?

Possibly. If Adam's batteries are nominally 12V they'll almost certainly be 10 cells, being as NiCd nominal voltage is 1.2V per cell.

Phil, do you think that the charger I pointed to, charging at 1A, for a 12V 2Ah NmHi battery, is too fast?

No, probably be fine. I'd avoid charging a 20Wh/2Ah battery at 2A, and if it's a 40Wh/4Ah-ish sort of thing, it could probably do with a bit more grunt if you need it quickly.

I own about four chargers of the type I mentioned and their flexibility is very handy. You do need to know broadly what you're doing to set them up, but you can store presets. Crucially, you can also get variants that run from 12V, so you can charge in a vehicle or from a larger battery. This is extremely useful.

P