Take charge of your batteries

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.

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.

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.

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 7Ah12v 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 7Ah12v 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.

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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About Damien

Damien Lovegrove learned his trade as a cameraman and lighting director during 14 years at the BBC, working on programmes such as the Clothes Show, Top of the Pops and Casualty. Fifteen years on, Damien has become one of the foremost trainers of photography and entrepreneurial business strategies in our industry. A published writer and regular columnist, Damien has travelled the globe sharing his knowledge and expertise. “Photography fascinates me” declares Damien. "Much of my photography is inspired by a burning enthusiasm within me” explains Damien. “Picking up a camera gives me such a rush that I’m instantly driven to create pictures.”

46 thoughts on “Take charge of your batteries

  1. 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.



  2. 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. 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. 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. 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. 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. 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.


  8. 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. 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.

  10. 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.

  11. 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.

  12. Hi Damien,

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



  13. 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.

  14. 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.

  15. 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.

  16. Hi Damien,
    The original fuse welded in the circuit board of the Broncolor mobil battery kit is smaller that the suggested thermal fuse of 128C rating.
    The suggested Mapplin fuse has 14mm long x 4mm and also larger leads diameter than the original one.
    Also according Mapplin recommendations when installing any of these devices, never solder directly to the wire leads – you must use screw terminals, terminal blocks or crimped on connectors.
    Have you replace the original with this one with success?
    I would like to be sure if before Buying

  17. Hi Artur,

    I suggest you send your battery to Broncolor for repair. Broncolor is now destributed by Hasselblad in the UK. They will be able to help you because this is a very popular fault. I don’t want to be responsible if a home repair does not work for you. I have repaired many boards myself but I’m very fast with the 40w iron and I am used to this process now. The thermal fuses change size specification from time to time depending upon the supplier Maplin use. Also check out RS or CPC. You will notice that the original fuse is soldered (not welded).

    Best regards, Damien.

  18. Hi Damien
    I had the original mobil (not the A2L or A2R) from broncolor and looking for additional battery with the carriage or cage that goes directly to the mobil pack…any help where I can fins one, here in the US no luck trying to find a used one.

  19. Hi Pedro,

    I know what you are looking for. I used to have several for spares and repairs. The circuit boards had a tendency to blow the thermal fuses and occasionally the tracks would melt. When I ceased to supply Broncolor (politics got in the way) I binned my spares stock. Try the US distributer/ importer for Broncolor. They should have spares under contract.

    Sorry I can’t be of more help.

    Kindest regards, Damien.

  20. Hi Damien, I need to replace the batteries in my broncolor mobile A2R, and I wanted to upgrade from SLA batteries to lithium, I have however a hard time finding out a specific brand or model number for compatible lithium batteries.
    Any chance you have that info?
    thank you

  21. Hi Sebastian,

    I use Lithium batteries of far higher capacity than the 12aH A2R cells in our inverters. We have them made for us in the far East and they have inbuilt safety circuits for overload etc. However the A2R has a high recycle current and this suits a SLA cell far better as the current on recycle can reach 60A+. The charging circuit is different too as is the battery level indicator circuit. I think your best bet is to stay with the SLA system or buy the new Move kit by Broncolor.

    Kind regards,


  22. Hi Damien,

    Thanks a lot for your answer, I just bought a new couple of SLA batteries and will certainly consider the new Move kit from Bron.
    thanks again

  23. Does the Visatec Litepac take the same battery as the original Mobil & does it swap out as easily? I’ve been trying to find an extra battery case without any luck – so I was thinking of getting an extra battery & external charger so I’d be able to swap out the battery in the field if it was ever necessary – at least until I can find another battery case.

    Thanks for all the info – this page is helpful.

  24. Hi John,

    It’s been a few years since I was a Bron dealer and I can’t remember the details of the Visatec system. Hasselblad UK are the new distributors but I’m not sure how much help they will be. Give them a call and find out. Sorry I can’t help you further,

    Kind regards, Damien.

  25. Hi, jumping in late on this discussion but thought I’d add my 2 cents for anyone finding this in a search and looking for an answer. the Visatec Litepak uses the same battery as the Broncolor mobil. They are in fact interchangeable.

    Also — there are lithium batteries designed to substitute SLA and they can not only be used in the Broncolor pack but can also be charged with the stock SLA charger. I’ve made the upgrade myself and love the lighter weight and higher capacity!

  26. Rudi can you give us more information about the lithium batteries you are using to replace the SLA…I am gping to need to replace mine in the old original mobil pack (not the A2L or A2R)


  27. I have the original mobil pack and charger. What would be the best way to maintain my battery? Would the broncolor charger be safe to leave plugged in continually ? Would I need to periodically unplug an replug it? If so, how often. I only use the pack every 3-6 months or so.

  28. Hi Erin,

    The original Mobil charger is not ideal for continual charging. The cells will probably deteriorate. A Ctek charger for Sealed Lead Acid batteries is by far your best bet. Replace the cell yourself for about £20 and treat yourself to a new Ctek charger. You will need to have the lead modified. We used to sell these but that was 4 years ago.

    Kind regards,


  29. Hello Damien,
    I came across your blog & this particular thread after Googling ‘A1 Mobil warning’.
    Mine came on when I was using the Studio Booster & the mains supply tripped off. So it’s not a battery issue.
    I tried inserting a charged battery but it shows the same, so it confirmed its the unit at fault.
    Would you suspect the soldered-in thermal fuse?
    (I’m definitely up for some DIY electronics before shipping it off to Hasselblad at great expense)
    sincerely Ben

  30. Hello again Damien
    ….re-reading back though the comments it sounds like the ‘blown thermal fuse on the circuit board’ is in the battery case & not the mobil body???


  31. Hi Michael,

    We no longer distribute Broncolor. I’m sure there must be a dealer in the US somewhere. Otherwise recel the batteries yourself with replacements from Radio Shack. Kind regards,


  32. Hi Ben, the Studio Booster caused Broncolor all sorts of problems, not just you. It was a troublesome bit of kit. I ceased dealing in Bron kit several years ago and I never look back. I can sell you a fabulous Elinchrom pack. Haha. Anyway, it’s unlikely to be the thermal fuse it is more likely to be faulty capacitors. As you say, Hasselblad can fix the fault for you at an alarming price. I wish I could help but they now run a monopoly on Bron kit. Kindest regards, Damien.

  33. Hi Ben, Thermal fuses stop the battery charging but it’s not a fault that you will see if you use the Studio Booster. That can cause devastation without a battery. Don’t short the thermal fuse because if your fault is a shorted capacitor in the pack the copper tracks on the battery board will fry. I hope this helps, Damien.

  34. Hello Damien,
    thanks for your response & info.
    This was a very expensive kit when I bought from Calumet in Holland, some years ago.
    When it worked it was good, but fragile for the price.
    I will look at Elinchrom in the future!

  35. Hello Damien
    ….is the capacitor something that a keen amateur solderer (as myself) could fix with components supplied from my local Maplin, or am I just going to have to bite the bullet & send it off to Hassleblad? (with my wallet)

  36. Hi Ben, There are a few things to consider when working on Flash packs. The Capacitors hold a massive amount of power and even after months of non use can deliver a serious shock. They need to be discharged safely through a suitable resistive load. You will need a circuit diagram to be able to follow the circuity. It might be one of the other discrete components that caused a failure of the unit and the case of the component might not show any signs of the damage within. By far the best thing to do is to ask a competent independent photographic equipment repairer to give you a quote. Expect to pay a nominal £20 or so investigation fee. I hope this helps, Damien.

  37. Hi

    I just bought a Elinchrom Ranger RX Speed pack. Just wondering if there are any 12v 12ah lithium batteries with BMS or other suitable battery on the market in the UK I could replace the old lead batteries with?

    Many thanks,


  38. Hi Damien!
    I was wondering, once the battery is replaced for the Mobil pack, can the battery be charged directly via the pack as usual or you will have to take it out to be charged with the Ctek charger? I might be buying a Mobil pack, but I’m pretty sure the battery is busted (says A1 when plugged in) I was thinking of replacing the battery with the Yuasa as mentioned in the post.

  39. Hi Peter, The battery can be charged in situ with the Ctek charger. We haven’t been a Bron dealer for quite a few years now and don’t have any Ctek leads for Bron anymore. You might be better looking at Li-Ion replacement cells.

    Kind regards,


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