Battery care for SLA (sealed lead acid) photographic and video batteries | Creative and business resources for photographers

Take charge of your batteries

March 28th, 2010

Here is a guide to the care and maintenance of SLA or sealed lead acid batteries often used in photographic lighting kit.

Typical battery carriages containing SLA batteries.

This is a particularly dull subject but one that affects a growing number of photographers and videographers who use battery lighting and portable flash on location. SLA batteries are the power house of most portable lighting equipment including Broncolor Mobil kits and Lowel id lights. The batteries have a high capacity, are heavy, relatively inexpensive and if maintained properly will last from 4 to 5 years. However just one extended discharge can destroy an SLA battery and render it useless. Even a near deep discharge can greatly reduce the amount of charge a battery will ever be able to retain.

Sealed Lead Acid batteries like these are commonly found in photo video lighting equipment. Either carried in shoulder bags for portability or inside location flash power packs.

Sealed Lead Acid batteries like these are commonly found in photo video lighting equipment. They are either carried in shoulder bags for portability or fitted inside location flash power packs.

Some battery chargers are quite good at recovering a battery from a fairly deep discharge by using a pulsing phase cycle that dislodges sulphur build up on the plates but no charger can perform miracles. If your battery has been left to go completely flat then it will need replacing but don’t panic because they are not expensive. In the UK we have MDS battery and Battery Masters among the online traders that stock the most common sizes. In most cases a battery can be replaced without the need for elaborate tools. The battery connectors are usually the Lucar spade type and the leads simply push on to secure. A Broncolor Mobil pack has just four small cross head screws securing the cover to the battery carriage. Undo these and a battery swap can take less than a minute.

An SLA battery does not need to be periodically discharged in order to maintain it’s performance, in fact, it is best kept in a fully charged state. An SLA battery can be kept on charge indefinitely if a high tech charger, like the Ctek, is used. Cheap chargers have no monitoring and can overcharge and destroy a battery if the battery is left on charge for too long. Basic chargers also have poor voltage regulation leading to a shorter battery life.

The Ctek charger from Lovegrove Consulting is available with a variety of interchangeable output leads. It charges at 800mA in it's bulk charging phase which is considerably slower than most chargers but it does look after the cells well. An overnight charge is needed to rejuvinate an exhausted SLA using the Ctek charger.

The Ctek charger is designed to stay switched on and connected to a battery or charging port of a power pack when it is not in use, even for months at a time to maintain a battery in perfect condition ready for instant action. Most high quality flash lighting kits come with a two or three stage switch mode charger. These usually have a high bulk charging rate and switch to a maintenance charging rate when the battery reaches 90% of it’s capacity. Sometimes they show a green light but allow the battery to discharge slowly without maintaining it in peak condition. If you have one of these chargers you should periodically unplug it from the battery, wait ten seconds and plug it back in to restart the charge phase. The charger light will go red or orange to confirm that it is indeed charging the battery.

A Ctek charger has a very low voltage ripple and can stay connected to equipment when it is in use without any risk of damage. The Ctek system was developed to maintain the batteries of supercars like Ferraris and Lamborginis in peak condition whilst they are keep in garages under wraps for months at a time. A considerable amount of research and development went into the technology in a Ctek charger and their slogan is ‘The smartest battery chargers in the world’. I associate the word smart with being able to think rationally and the chargers are certainly not capable of that but they do continually monitor the condition of your battery and pulse life into it as and when required.

Battery configurations like this are most often carried around in purpose made shoulder bags. The battery shown is a 7Ah 12v type.

Here are links to replacement cells for two of the most popular batteries used in portable photographic flash systems and of course continuous tungsten lighting.

These cells are designed for repeat cyclic use and are perfect for lighting kits that get regular daily use:
12v 7Ah, 12v 12Ah
Lighting systems that spend far more time on the shelf than in use would benefit from cells designed for primarily for standby use:
12v 7Ah, 12v 12Ah

Here are the Bron pack from the latest A2R Mobil kit (top) and the original Mobil kit (bottom)

Here are the Broncolor battery packs from the latest A2R Mobil kit (top) and the original Mobil kit (bottom) with their corresponding replacement cells. The latest Mobil kit uses a 12Ah battery to speed up the recycling of the capacitor charge and to provide more full flashes per charge than the original 7Ah unit.

Acess to the battery in a Broncolor Mobil pack is via four small cross head screws.

If you are in doubt as to which battery you need consult your equipment manual or speak to one of the team at MDS battery.

The Ah rating on a battery indicates the number of amps it is supposed to be able to deliver continuously for a period of one hour. So a 7Ah battery should be able to deliver 7A for one hour if it is in perfect condition. There is a bit of headroom available on current drain but it would be unwise to draw more than 10A continuously from this size of battery. The equation you need to use to calculate the current draw is Watts = Volts x Amps So if you have a Lowel iD light that is 12v with a 100w bulb, it draws 100/12 Amps or 8.3A This current delivery is just within the upper limit of a 7Ah battery but better suited to a 10Ah or 12Ah battery. Indeed an iD light should in theory run for 50 minutes on a 7Ah battery but in practice 40 minutes is all you can expect from a perfect battery dropping to 20 minutes when a battery is at the end of it’s useful life. The same 100W Lowel iD light will run for just over 80 minutes from a good 12Ah battery.

Warning: The terminals of an SLA battery should never be shorted. A 12Ah 12v battery is capable of delivering 500 Amps in short circuit condition, enough to make screwdriver glow red hot.

Damien Lovegrove.

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16 Comments Add your own

1. Ziggy | March 29th, 2010 at 10:13 am

How bizarre? Went to use my Mobil kit after leaving the battery on charge for over a week, and all it would tell me was ‘A1′. i.e. NO GO. Very, very useful article Damien and most timely
Had to fall back on the 580 EX and tips on ‘speedlight mastery’ from your excellent DVD.

Cheers

Ziggy
2. Ziggy | March 31st, 2010 at 5:42 pm

Sorry to ‘hog’ this article, but I’ve been playing around with the Mobil pack since I was last here. Having removed the battery from the pack and connecting it to the ‘Bron’ charger it seems to be taking a charge (48 hrs now) but drops straight down to the amber level after switching on.

Would you advise buying a replacement battery from MDS in a ‘Year Zero’ kind of way and treating it to a Ctek charger?

Ordinarily, I would concur that this is a dull subject, unless it is particularly pertinent as in my case. As an aside, I’d forgotten how much low temperature affects the battery life too. Went through two sets of rechargable AAs in the 580EX because the outdoor shoot was ‘Baltic’.

Any tips gratefully received, as always.
3. Chris | March 31st, 2010 at 11:52 pm

Hi Ziggy
Quick tip on the AA’s that work for me. Always carry my spare rechargeable AA’s in my trouser pockets on location in winter. (Manchester can be Moscow sometimes) and keep a set of Duracells in the kit bag
4. Thorsten | April 1st, 2010 at 7:46 pm

Not a dull topic at all Damien! In fact, as a result of your article I did some further online research into CTEK and ended up buying one of their larger chargers specifically for my wife’s car as she does lot’s of short local journey’s, which really stresses the battery and that type of scenario appears to be one which many happy CTEK users seem to encounter.

Any suggestions, based on your experience, on suitable chargers for AA NiMH batteries? If I recall correctly you use the same NiMH AA batteries that I do (there’s a “&” in there somewhere, right ). I can’t say I’ve ever had a problem with mine, but at the same time I often wonder if there’s a better solution out there that will discharge the batteries first to a safe minimum level before charging them, thereby maintaining their performance. I realise that discharging NiMH batteries before charging them isn’t as important an issue as it used to be with NiCd’s.

- Thorsten.
5. Ziggy | April 1st, 2010 at 10:24 pm

Cheers Chris.

Will do. Was in Moscow (Manchester) this lunch time going around the ‘Lovegrove Trail’ in Castlefields using my 5yr old son as a model. Batteries really don’t like the cold!!

Pockets and Duracells it is.
6. damien | April 2nd, 2010 at 12:08 am

Hi Ziggy,

A1 is not good. The Mobil cuts out at A2 when in use and that is the time to put the battery on charge straight away. Not in 24 hours time, sooner than that. Do not try and switch the Mobil back on until the battery is charged. A1 appears when the battery is past it and in most cases the battery wil not recover. I’ve found the Ctek can recover some batteries in this state but not all.

Thanks for your kind words about my DVD. Damien.
7. damien | April 2nd, 2010 at 12:18 am

Hi Ziggy,

Sounds familiar! Your battery is at the end of it’s life. Even a good battery will drop to amber fairly soon after a few flashes but that’s normal. The Ctek used as a maintainance charger will be perfect.

Damien.
8. damien | April 2nd, 2010 at 12:26 am

Hi Thorsten,

I use 7DayShop AA NiMh 2900 mAh batteries now. Really great value and performance. I have 2 Ansmann chargers like this. They do a great job.

Cheers, Damien.
9. Chris | April 2nd, 2010 at 10:04 am

Hi Zig,
Lovegrove trail eh! is that the trail thats cuts thro the Hanley arena
Like Damiens new Bristol location, I’m researching a new Manchester patch. Say hello if you see me around.
C
10. Tara Taylor | April 2nd, 2010 at 4:52 pm

Great article Damien, I now have my new battery happily attached to the CTEK!!
11. Sean Davis | April 15th, 2010 at 5:06 am

A quick question. Can I safely connect the charger on my Mobil pack and charge as I shoot? Will it bugger the capacitors in any way? The studio boosters are beyond rare, or I would pick one up in a heartbeat.
Great article, thanks.
12. damien | April 24th, 2010 at 8:52 pm

Hi Sean,
Yes you can charge and shoot. Broncolor have always supplied switch mode power supplies with a low ripple current with the Mobil. Forget the studio booster it’s a problematic bit of kit. I can supply you with a re-celled extra battery carriage for under £100 if you need one.

Cheers, Damien.
13. Andy Barr | January 6th, 2011 at 9:34 am

Hi Damien,

Don’t suppose you know if the XLR plug is compatible with the Elinchrom Ranger SLA batteries??

Cheers,

Andy
14. damien | January 23rd, 2011 at 1:44 pm

Hi Andy,

I’m not sure about the Ranger SLA battery terminals. If it is 4 pole XLR then it will be fine. We use the broadcast industry standard specification: Pin 4 +12v and Pin 1 0v

Kindest regards, Damien.
15. Bill Lusk | January 20th, 2012 at 5:33 pm

Hello,
I’m in the US and can find no resources for the problem I’m having. I have three batteries for the original mobil pack. Unfortunately, I let them all run down such that none of the batteries would charge any longer. I purchased replacement batteries, installed them and now only one of the batteries will charge- the light on the chargers will not even glow on the other two. If I remove the batteries from the non-charging carriers and install them in the only carrier that is charging then they will charge fine. Any experience with that problem? Thanks.
16. damien | January 22nd, 2012 at 4:03 pm

Hi Bill,

Your problem is a blown thermal fuse on the circuit board. It’s a very common problem. They look like silver metal resistors and should have no resistance. You can replace them with a jumper wire or another thermal fuse of 128C rating. Be fast on the solder though if you go down the thermal fuse route.

I hope this helps,

Kindest regards, Damien.