How to buy an Inverter Battery – a layman’s struggle in India

     This is March 2014 and already into summer in Bangalore and despite the fact that elections are coming later this summer, unadvertised power cuts have started regularly.  And my old Amaron inverter batteries having pushed their limits are giving way after a little over three years.  Now it was time for me to replace these batteries and I thought I would go with Tubular ones with their promise of longer life that comes with added cost.  I managed to do some two weeks of extensive research to know the technical jargons and what they mean so that I can confront the dealers more intelligently – as Alexander Pope said “ A Little learning is a Dangerous thing”, I am treading ‘dangerously’ through this article but wish to share some knowledge with my audience.

     For those of you lucky ones who do not need to worry about power cuts and hence UPSes and inverters, bless your soul. And for these souls I just blessed, if you want to carry on with me on this article, kindly do so.  For us unlucky ones who see nightmares of power cuts looming after elections, thanks to the usual excuse of lack of water and power generation and bad distribution, here is some help from a layman perspective – feeling slightly ashamed of not able to use my electronics brain more prudently! . 

    (Power) Inverter put simply is a device that gives us power from the stored battery  – it converts the direct current into alternating current, thus helping us run the electrical devices that are connected in our homes like fans, lights, TVs and even small home appliances.   Although there are huge inverters which can run heavier electrical appliances, for a common man, it is enough if it provides for a few fans, few lights and a TV which you may want to work when the main powers are down and this is where my article concentrates.  In my case, I have an inverter but just the batteries that needed changing and hence this article is how to buy a battery, that too in India.  I am not going to talk about what INVERTER itself to buy as this may be more electrical oriented and may not be my cup of cake.    It is not advisable to connect the heavy load appliances that work on 15A socket to the home inverter and when you do the electrical wiring to your house, have them separately on a different phase.

    Before I go any further, there is an excellent source of info about inverters with questions and answers that can provide you a balanced opinion:  I have managed to publish a few points here and there from this site to make some of my points clearer.  Also remember to do adequate research based on your requirements before you buy and  avoid lots of ‘fake’ batteries available in the market – always go with the some sort of brand that have a good dealer network in your area and a decent warranty.

    There are generally two types of batteries:  Lead-Acid batteries and Sealed Maintenance Free (SMF) batteries.  SMF are the “Buy and Forget” types where there are no  emissions, completely sealed, does not need water topping and has a very short charging time.  The downside of lead-acid is it emits fumes while charging as the battery gets heated up that is not environmentally friendly.  Always remember to keep these batteries in a ventilated open cool space away from any heat source.

    Even with Lead Acid inverter  batteries, there  can be two types – the normal flat-plate ones and the Tubular ones.  Tubular batteries are more reliable, charges faster, comes with higher battery life(~1.5x) , has less water loss than the normal flat plate but all these come at a cost for the same aH rating.  So, a prudent customer would like to negotiate price of the tubular to be < 1.5x than a good flat plate battery. 

   And in Tubular they have different form factors based on dimensions called differently by each manufacturers as Jumbo, Short, Flat etc. but think of them of being in two forms – TALL or Normal, and then check the dimensions.  If you do not have more floor area, you need to choose the TALL one but they do not fit into normal trolleys.  HADI that gets advertised usually come in TALL tubulars.

    Before one buys a battery, it is important to understand what lighting fixtures need essential backup and what would be the total wattage consumed by them.  This would set the limit of both the inverter to buy and the associated batteries to be used – one must have ENOUGH backup.  Then one must think of how much backup time one needs for these.   Let us say a few lights, fans and a TV add up to 400W and we want the backup for 3 hours.

    No inverter converts power at 100% efficiency – meaning the actual power derived from the circuit is much higher than the real power delivered – we can call it efficiency although a better word is power factor(PF).  Usually a PF ranges between 0.7 and 0.8 and you must add the additional losses due to the wiring itself which cannot be that easily factored in.  So the inverter has to be a rated at 400 W / 0.8 PF = 500 VA. So, it is safe to buy an inverter that can deliver a little higher and  go for a 600 VA inverter to run the 400W load. 

     The batteries available now in the Indian market are 12V and hence  one needs to go for a 600 VA/ 12V x 3 hrs. = 150 aH battery.   One needs to connect two or more batteries in series to get higher voltages  (as some inverters would require a 24V or 36V DC power source) at the same current, and while doing so, one needs to ensure to use the same battery type of the Equal capacity(same voltage and same aH rating) and never mix makes and sizes.  The weaker capacity causes the imbalance by quickly discharging and always the weakest link.  This applies to batteries getting old – even if one battery is worse than the other, one needs to unfortunately replace both the batteries at the same time.  Extrapolating from my previous example, for the same 150 aH and for the same 3 hours of back up time, if we use a 24V DC source, we will need a 1.2 KVA inverter.   Once you have the inverter, look at its specifications to see if it needs 12V, 24V or 36V which would make you buy, 1, 2 or 3 batteries respectively.

    The inverter batteries come in the range of 80aH to 150aH for flat plat ones, and from 100 aH to 200aH for Tubular ones in the Indian market.  In the flat plate inverter batteries, we have TATA Green, Amaron Current and Exide Inverter Plus among the brand names. In the tubular types, we have Okaya, Exide (Inva Tubular, Ceil, Inva Red and many other groups), Amaron, Luminous Inverlast, Su-Kam, Prestolite and Amco.  I did not see much of an action in the local Bangalore market for either Prestolite (Tudor India) or Amco.  We even have local Peenya makers like SunTrac who seem to be providing batteries which are much bulkier.   Exide seems to enjoy a premium in the market, thanks to the perception of higher quality, number of dealers and also in pricing.  There is NO reason for one to match the inverter brand to the battery of the same brand, if they are producing both but it would help you in terms of service when a problem arises as they cannot blame each other for it. Among Inverters, the leading names today are Su-Kam, Luminous and Microtek, although it looks like Exide also makes them now.

    When one looks for Batteries, we have either the C10 and C20 type which denotes the capacity rating of the battery, although I am still trying to understand what it really means – the former seems to be more tailored towards solar inverters(used on daily basis))  and the later towards the home power inverter(for infrequent power cuts) now. C10 is better than C20 as a lower aH rating of C10 corresponds to a higher aH rating in the C20 [Capacity at C10 = 0.8 x Capacity at C20, meaning 100 aH at C10 rating will have 125 aH at C20 rating] – C20 just inflates the capacity!   Both of them offer the same aH rating under different load conditions and manufacturers publish them accordingly in their website. For the same aH rating, higher C rating translates to higher battery costs. C20 takes a longer time to discharge than C10 for the same aH rating which makes it more suitable for home applications.   Please check this for more info:

    Now you have an idea of the battery rating and the capacity you want to buy, how many Tubular batteries and what dimensions based on the space available to store your batteries.  Now let us get introduced to something more technical which most of the dealers and distributors themselves may not know:

  •  The quality of the tubular batteries is on its spine tubes. These spine tubes have to be die casted in high pressure (100 bar +) – there is a machine from Germany called HADI that is used to do this invariably and most of the top brands use it, although I would insist on you getting this in writing in a specification sheet  for the battery you want to buy. Only top brands can afford these machines and if you are buying from the local brands, it is usually a low pressure or a gravity type one which result in lots of voids and non-uniformity. HADI tubular have low self-discharge, corrosion resistant and have longer life.
  • # of Cycles of deep discharge at 80% Depth of Discharge (DoD) – higher the better.  80% DoD means these deep-cycle batteries can be discharged down to 80% repeatedly and the more charge-discharge cycles the battery is able to do it, the better it is.
  • Manufacturing date is very important – the older the battery has been in combination between the transit+Go-down+dealer, the more charge it may have lost just without being connected – this is called “ Self discharge” which decreases the shelf life of batteries. When the battery reaches your home, it has less than full charge which must be compensated at the dealer end by a “Freshening up” or “Top up”.  It looks like the battery would reach you within 2 months from manufacturing best case and faster from the factory during the summer season when the new stocks arrive and when the needs goes up.   Again, here HADI tubular works out better due to its low self-discharge

   Now you are ‘knowledgeable’ and ready to buy but do not know which brand to get and here are some tips and my observations against each:

  • Exide – highest cost amongst batteries and lots of dealers and they take pride being marketed as a premium brand. I believe they are the largest battery manufacturer in India – the name itself stands for “Excellent oXIDE”.     Their website is one of the better ones although they do not necessarily have all their product lines listed.  You can buy online as well but only the flat plate batteries- their prices are higher online than with the dealer which is the case almost with any battery manufacturer- cannot understand the logic behind it.  They also do have the “don’t care” attitude because once you start bugging them for information; they do not necessarily provide it and actually get offended by our “recently gained smartness”. Exide has the widest range to choose from.  Their best line is Inva Tubular – the IT series, but they have the same batteries in another brand called CEIL that they do not advertise and which is much cheaper and with lesser warranty.   They try to ‘sell up’ first – meaning offer the highest price IT series and then as you tell them about your budget, slowly come down to other series which are much cheaper.  I have some great interaction with their Kolkota head office but cannot say the same about their local support.  They do not even have any social presence in Facebook.
  • Luminous – has its Inverlast series and may have the lowest warranty in its class compared to others.  Their website is not complete as they have a write up only on the LT500 but not on the other batteries in terms of cycle times, if it is HADI or not etc.  Have a good Facebook presence and they seem to be active there as they respond to queries within a day. They have their dealer network advertised in their website which is useful.
  • Su-Kam – has their Bazooka and the BIG series, but looks like they are more selling into the people who buy their own inverters.
  • Okaya – very confusing website and their  information contradicts each other in their website.  Do have an online store which is more expensive than others.  Have only one dealer in SP road here that can provide the quotes.  But their support network is pathetic to say the least – they do not reply to queries.  Generally cheaper batteries but they have some HADI lines as well. Sounds like a Japanese company but I believe they are from Hyderabad.   Generally, if you Google for batteries, Okaya has lots of mentions of complaints – not sure how truthful they are though.
  • AMCO – nothing to write home about on their Cheetah series, not very email centric – more Chennai based and do not care much about other cities and not sure if they use latest technologies or not in their manufacturing.  Nothing is written about them in their website.
  • PRestolite – again, little help from the website- has their product lines and you need to search under Tudor India. Their TALL lines are cheaper than most. Again, no detailed information about their batteries on their website
  • Amaron – has their CURRENT Series but starts only at 150 aH and above.  Absolutely nothing on their website in terms of specification or product  data.
  • SunTrac – talked with their manufacturing head and learned a lot about the process, their website does not read well and they are local manufacturer from Peenya – all their specifications are in C10 rating, much bulkier and it looks like they manufacturer for other OEMs.

  Let us talk about the final stage of the buying – dealers seem to be much better off in pricing than any online stores.   None of the dealers of any manufacturer would push you to make a sale – if you want to, buy it or get lost sort of an attitude. They give a price and that is it- none of the dealers I interacted with were able to answer or understand any of my question on technology and specification above to give a fitting answer confidentially. They drop the ball and disappear out of sight. They would even go to the extent and ask you if you are a dealer or a customer! Dealers feel intimidated by the questions being asked- they are usually happy with people who have not done their homework, who just walk in, buy something and get out. I was not willing to do it as this is not a small purchase – it costs anywhere between Rs 15K to 25K for a pair of batteries that I needed to buy and based on our usage, I estimated a life time of about 5 years for a good RoI.  Also realize that none of the manufacturer or the dealer are very email centric nor want to commit to a written quote, nor have information about their batteries in detail on their website.

   The way to start is to send an email to all the manufacturers about what you want and what you are looking out for. Some of them do reply and provide you with a rate and the name of a dealer you can work with.  Demand that you need a dealer close to your house which is very critical because if you want him to top up the water every 4-6 months and if there are any issues, it is always better to have someone close by.  Also ensure your dealer has been around for some time and not the run-of-the-mill type who is bound to close soon ( I have seen lots of battery shops disappear about a few months in my neighborhood itself)- you can easily get a feeling of wanting to do business (or not)  from their body language and their store once you visit them.  It would not be long before you realize that each dealer would sell one brand more because the commissions he gets out of them is higher and he would bad-mouth the other brands to convince you – so be aware of these and take them with a grain of salt.

   At the same time, you can also send an email to all the dealers closer to you and ask them for the best price.  Then visit them one evening to make sure you have your presence felt and they understand you are not just asking but can be serious for a buy.   They would say : “ if you buy  now, I would get you the best deal “ – do not fall into this trap as there is never a ‘best deal’ unless you do your homework. By talking to 2-3 dealers of each manufacturer, you may have an understanding of a ‘ bottom  price’ close to which they would not do a deal within which you need to squeeze them.  And do this for 2-3 manufacturers you have decided. Ensure you get a pricing that is all inclusive – taxes, delivery, and connecting.

   Talk around for the best exchange your old batteries can get – again here, the dealers would make it look they are doing charity work whereas every battery is recycled properly and you can get a decent price for the same. In your final quote, ensure you pay the amount after the exchange. Once you buy the batteries, ensure you have the warranties for those batteries and they have topped-up the charge before delivery to compensate for any storage related self-discharge.   Higher the warranty provided, the better deal you can get. The warranty is split between total replacement and pro-rata adjustment (discounts on getting new batteries) – try to maximize the total replacement warranty which increases your confidence on the product you are buying.