12V battery + charger recommendation
 

Seeking recommendations for portable power source with XLR4 output. We have a number of devices to power (one at a time) including either field monitor, AJA i/o express and with use of Vortex XLR4 to Sony dc input cable could also power Sony SBAC SxS card reader or XDCAM deck in the field with a MBP.

well to answer my own query - I'm looking at generic 7.2A 12V cell with a 2m XLR4 cable - the field monitor is rated at 1.9A, so assuming the cell is 7.2Ah my understanding is I should be able to run the mon for 7.2/1.9 = 3.78 or max 3hr 45min.

Cut your run times just about in half with lead-acid batteries. If they are drained quickly, they put out much less wattage (amp-hours). Most batteries are rated at the 20-hour rate to get their amp hours. If you are draining it in only a few hours, they will not put out the specified energy. Also, if you drain lead batteries all the way down, they can be ruined on the first use. The 7.2AH battery you are talking about is likely a gel cell so it has another weakness. Bubbles can build up in the gel if charged or discharged quickly that can decrease it's power. If this happens a bit every time you use the battery, it will go down from a 7AH cell and you will effectively be working it harder every time you go out since it will have less capacity each time. A battery with less capacity will be more stressed than a larger unit. As the stress goes up, the damage increases. If all this isn't enough information for you, look up the "peukert effect". If you want a decent lead battery, look for a small AGM battery. AGM stands for "absorbent glass mat". They use fiberglass mat to soak up the acid and keep it from spilling. These batteries don't get the bubbles like gel cells. I have an Optima deep-cycle marine battery (like a car battery) that is still going strong after something like 7 years.

Insightful information - thanks Marcus.
Prior to seeing your post I'd actually been thinking about staying with Sony BP-GL65 14.4V 65Wh, using formula:

amp = Watt / volt

is that a 4.5Ah battery? Being Lithium-ion does it much matter that it's half capacity of gell or acid?

I filled in a purchase order for work describing my need for a rechargeable battery suitable to power a Sony PVM-740 (12V 1.9A). The supplier duly quoted and supplied Sony - almost flat and with no charger - before it was delivered I enquired whether it included a charger - they were going to check...then it was delivered.

technically they abided by the PO, but what use is a rechargeable li-ion without a charger?! That batt ain't cheap and the price for a genuine Sony charger is barely justifiable when we have 1 batt and 1 device that uses it. Hence thinking about general purpose battery - but the 740 isn't cheap item and I don't want to put it at risk either.

I don't think you will damage equipment using a different battery. I assume it has included 12V power connectors? If so, it should be fine on any battery of the right voltage. Batteries aren't prone to spikes like line power.

If you buy a battery, the charger is often not included. Also, you probably need more than one. The battery you got is a sony v-mount so it is fairly standard in pro equipment, but they are rather expensive. Of course, that monitor is not exactly cheap either.

Your calculations are correct regarding the amp-hours of that battery. The good news is that lithium runs for close to it's rating and should last much longer than lead. Lithium also should not be fully drained, but most devices that run on them won't take their voltage down that low. Lithium is best stored partly charged so don't leave it drained and don't store it fully topped off for long periods either.

I built my own battery packs with A-123 Systems nano-phosphate cells. The cells came from DeWalt drill battery packs as well as direct from A123 Systems.

The charger is a "balance" charger from FMA Direct. Each cell is charged individually.

These batteries can be discharged heavily without getting crippled. They can also provide a great deal of amperage if necessary. That also means they can fry something if used improperly. However, they're safer than lithium-ion cells as they are less likely to explode and won't burst into flames if cut open or even drilled.

Dean, can you elaborate on how you charge the batteries? I assume you have a series + parallel pack with multiple groups in a series of 4 to get 13.2 volts. Does the charger work on each group or do you wire each cell independently? I looked at the chargers at fmadirect.com and they all seem to have a 12V input. Do you use 12V as the source or is there a 120V model? I have never been able to figure out how to charge lithium batteries and I would like to do this knowing the advantages of LIPO cells.

Bescor makes a variety of 12v xlr4 batterys, some shoulder strap type, some belt type, I used their smallest one to power an led light on a Canon xha1 and was very happy with it. Check bhphotovideo for bescor batteries, there are many...here is one link: http://www.bhphotovideo.com/c/product/135340-REG/Bescor_BES015XLRNC_BES_015XLRNC_Shoulder_Pack_Lead_Acid.html

Marcus... The 4 cells are 3.3 volts, 2.3 amp-hours. They're connected in series to create a battery that provides 13.2 VDC at 2.3 AH (30.36 Watt-Hours).

There's a balance-charging tap to each cell leading to a multi-pin plug that connects to the charger. This balance tap allows the charger to charge and monitor each cell individually. And the battery charges fast. About an hour or so, I think.

FMA has a power adapter that converts household current to 12 volts. The charger connects to that. The reason FMA does this is because RC folks often charge their batteries out of their cars. They'll connect to the car's battery or to the lighter plug.

For the amount of power they put out, the A123 batteries are very lightweight. Especially when you compare them to gel cells and other lead-acid batteries.

The battery that Battle shows should work just fine if the monitor has XLR-4 power input. It's big enough that it won't die out too fast.

Dean, how do you connect the wires to those cells? Is the metal on the casing suitable for soldering? How would one make a series/parallel pack like this? Would two chargers work for double the cells? 36W/hours is not enough for powering lights long enough to shoot a scene so I would need a more powerful pack. I know there are A123 cells twice this size, but even those are too small.

Marcus... The cells have solder tabs. That allows the balance taps to be connected as well as soldering the cells into a pack. Applying heat to any type of battery itself (to solder connectors) is not recommended. Tabs are usually spot-welded in place with heat that's applied very briefly and the A123 cells have tabs already in place.

Balance tap leads depend upon the number of cells in the battery pack. For what I built, there's a schematic provided by FMA Direct: CellPro Node Connector Manual, http://www.revolectrix.com/support_docs/item_1213.pdf

The only caveat I'd post is that these cells can provide as much amps as demanded by a circuit -- even a short circuit. 22-gauge wire can fry like a firecracker fuse if shorted. So great care must be taken when working with these batteries.

It's possible to create a series/parallel pack, or create a wiring harness to allow parallel connections. In which case you'd charge the packs separately. A company builds packs with A123 cells large enough to run a Toyota Prius 40 miles. But it's $10,000.

I built four 4-cell packs which provide enough power to run a recorder, wireless receivers and an on-camera light. My Edirol R44 runs for 10 hours on a pack. They also power a CoolLights LED light which is OK for a short interview or for ENG-type work.

But if you're looking for enough power for production lighting you might be better off getting a small generator.

Yes, Sony mon has XLR4 input - if I can get 14Ah from my supplier I'll change down to Pb, 7Ah seems too small capacity - although we'd get two of the smaller one with chargers if we exchanged.

Dean, I switched to all Coollight LEDs so I don't need a huge amount of power and I rather not deal with generators with all the noise and exhaust. I just find myself needing to run a couple of lights on battery from time to time and like to have enough power to run for a couple of hours. I would probably want to make something like a battery belt with 100WH so I can run a couple of things at once. It doesn't seem so easy to make a pack with more than 4 cells in series. I do prefer a balance charger as I've read it is easy to kill a cell with bulk charging (just putting the whole pack on a 12V charger).

Marcus...

The battery pack will run a CoolLights 600 for about 20 minutes. If you're interested in seeing how it's set up let me know.

Wiring one of these are pretty easy. I can help you with that if you decide to build one. I have separate battery packs, and if I need to connect two in parallel I have a simple harness to combine them. I'm using "Deans" connectors which are small and provide a very positive connection. From there I have various adapters including 4-pin and coaxial.

If you want to check out a Honda EU 1000 I have one of those, too. You can get an idea of what it weighs, the noise level, etc.

Dean, I would like to see how you put those together. I guess your setup is more complicated for charging, but the fact that you can run in parallel is an advantage over some packs I've seen for sale that charge as one entity. Those big packs are apparently prone to getting imbalanced cells. The way you do things eliminates this. The really big packs depend on the huge number of parallel cells to compensate for individual cells going bad. If ony one cell in a multi-cell group goes out, the other cells can support each other. Although I want a larger pack, the ability to run in parallel and charge individual cells is a solution. As long as each pack has all good cells, no parallel group will be overtaxed.

I'm out of town next week so either this week or after I get back would work.