| Q: What is the difference between VRLA, SLA, and AGM batteries? | SLA and VRLA are different acronyms for the same battery, Sealed Lead Acid or Valve Regulated Lead Acid. This battery type has the following characteristics: Maintenance free, leak proof, position insensitive. Batteries of this kind have a safety vent to release gas in case of excessive internal pressure build up. AGM, Absorbed Glass Mat refers to a specific type of SLA/VRLA where the electrolyte is absorbed into separators between the plates consisting of sponge like fine glass fiber mats. |
| Q: I've heard about lead/calcium, calcium/calcium and lead/silver batteries, what's this all about? | No
battery manufacturer uses pure lead as the grid material because it's
not hard enough to endure mechanical stresses a battery is exposed
to on a daily basis. Early in the development of lead acid batteries it was found that adding a few percent of antimony solves this problem, but not without any side effects. In addition to its hardening properties, antimony also improves the 'castability' of the thin lead grids. In the ongoing effort to keep down manufacturing costs, grid makers changed to a drawing process, and the antimony in the negative grids was replaced with calcium which still offers reasonable strength. The antimony was retained in the positive grids which have to endure higher mechanical stress, meaning the positive electrodes continued to be produced in a casting process. This battery is called a hybrid. There are also some changes in the electro chemical reactions depending on the type of alloy in use. During charging, antimony is slowly separated out from the positive grid due to corrosion. It drifts to the negative plate and 'poisons' it, which leads to increased self discharge of the negative plate and gradually lowers the voltage at which gassing starts. In order to do away with negative plate poisoning, the antimony was subsequently replaced in the positive plate with calcium. To achieve high mechanical strength of the positive electrodes, while reducing their thickness, tin and sometimes silver is added. These additives allow for slightly higher charging voltages thus a higher level of charge, as the gassing voltage gets pushed higher and corrosion resistance increases. As these new alloys add strength to the plates, they can be made thinner and the plate count increased thus giving another increase in capacity at the same battery volume. I'm not sure about US made batteries. Maybe some manufacturers still cast their positive electrodes which necessitates antimony in the alloy (see hybrid battery above) which offers increasingly less resistance to gassing as time passes, due to negative plate poisoning. This lower resistance to gassing, is probably the main reason why some charger manufacturers (most notably c-tek) limit their boost charge voltage to 14.4V, instead of 14.7V as specified by Asian battery manufacturers. |
| Q: why should I pay attention to the weight of the battery when comparing different brands? | The
amount of lead inside a battery of a given capacity is directly related
to the design life time. A deep cycle battery has solid lead plates,
and the thicker they are, the longer the battery will last. With the price of the raw material currently at U$2.30 per kg you can see quickly why manufacturers constanly push for less lead in the battery. It is then left up to the sellers
to come up with enough spin to make you think you're still buying a
long lasting product although the weight of the battery has been
decreased steadily. One word of caution when comparing AGM with GEL batteries. During production, the GEL is released into the battery container under vacuum in order to give good contact with the plates. Thus there are no voids inside a GEL battery, making them heavier than AGMs which do have voids. Due to this fact, GELs tend to be heavier than AGMs, although they don't necessarily contain more lead. |
| Q: Do I have to worry about battery gassing? | these batteries are of the AGM VRLA type (absorbed glass mat, valve regulated lead acid). There is a slight constant over-pressure (around 5 psi) inside the battery container which is a prerequisite for the hydrogen recombination. A tiny amount of gas is produced during every charging cycle which keeps up the pressure, against the regulating valves. Only under severe over-charging, or charging at extremely low temperatures, the recombination becomes less effective and the excessive hydrogen gas produced, will then vent through the regulating valves. But even under these conditions, the amount of gassing won't be excessive due to the calcium in the lead alloy (as opposed to lead/antimony alloys which gas quite a bit more at the same voltage setting). Having said this, no battery should be charged inside a totally sealed, air tight room for obvious reasons. |
| Q: How far can I run these 100Ah batteries down to? | I recommend to
about 80% of DOD (depth of discharge), meaning there should be around
20% capacity left at the time when recharging starts. Note, our deep cycle batteries can be taken down to 100% DOD. The cycle life (at which the capacity will have shrunk to 60%), is around 250 cycles. At 80% DOD, you can expect 350 cycles and at 30% DOD, you get a whopping 1250 cycles. View the graph for a better understanding of the relationship cycle life versus DOD. Example: say you've got a load connected to your battery which draws 5 amps. Since 80% of 100Ah equals 80Ah, your load can draw current for 80Ah/5A equals 16 hours. You can easily double this time by wiring two of these 100Ah batteries in parallel. Note that this simple calculation is only true for loads, smaller than 6 amps (or 12 in case of two batteries in parallel). For heavier load currents, use the method below. Note, our deep cycle batteries can be taken down to 100% DOD. The cycle life (at which the capacity will have shrunk to 60%), is around 250 cycles. At 80% DOD, you can expect 350 cycles and at 30% DOD, you get a whopping 1250 cycles. View the graph for a better understanding of the relationship cycle life versus DOD. |
| Q: Can I monitor the battery voltage to get an idea about the DOD? | Yes,
you can (and should). Do a load budget first: Say, you have a light, a fan, a fridge and a TV, all drawing current at the same time. You're drawing like, 2A plus 3A plus 3A (fridge time averaged) plus 5A equals 13A of combined load current. Now pull up the discharge table and locate the row for '10.5V' and 'A'. In the 'A' row, locate the closest values to 13A which are 16.0 and 11.3. 13A is about half way between these two values, meaning you can draw this current for a maximum of 6.5 hrs (half way between the corresponding time values from the top row). But remember this would bring your battery to 100% of DOD, and we only want it to go down to 80%, so subtract 20% from 6.5 hrs and the result is 5.2 hours. To find out what sort of terminal voltage this corresponds to, look up the discharge graphs and locate the 5 hr vertical grid line. Imagine what the shape of the discharge curve for 13A would look like and where it would intersect with the vertical 5 hr grid line. You'll find a result close to 11.4V, which is your '80% DOD cut off' voltage for a 13A load, which has been run continuously for 5.2 hours. The resulting 'run time' down to 80% DOD, can easily be doubled by wiring two 100Ah batteries in parallel. Remember, your absolute lowest limit for the cutoff terminal voltage is 10.5V. |
| Q: Do you have any larger Ah capacity in
stock? |
Not
at this stage, but you can easily double up - just read on. |
| Q: Can I wire two or more 12V100Ah batteries in parallel? | Yes.
By doing so, you effectively end up having one large 12V battery. You
can leave them permanently wired up this way, for discharging
as
well as for charging. The 12V charger only 'sees' one big battery. More on this under 'what sort of charger do you recommend'. |
| Q: Why would I want two or more 12V100Ah batteries? | Compared
to only one large capacity battery, you gain greater fitting
flexibility since the bulky volume of one big 200Ah battery is now
split in half. There is the important fact of twice the charge acceptance rate, meaning you can put twice as much energy (Ah) back into the battery, in any given amount of time. E.g. if you use your car alternator for charging, almost the full 60A charge current made available can be absorbed by two 100Ah batteries. If you only had one battery with a maximum 30A charge current acceptance, your engine needs to be run twice as long. Note that deep cycle batteries offer one to two thirds of the CCA current of a equivalent sized starter battery. Under normal temperatures this is not a problem as the maximum cranking current of around 250A can easily be accommodated by a 100Ah deep cycle AGM. Problems start to occur as the battery temperature gets below 10 degrees at which the capacity drops off significantly. Again, by wiring two or more batteries in parallel, you overcome this limitation. In effect, this gives you a battery with excellent cranking ability down to low temperatures, as well as all the advantages of a deep cycle design with a capacity twice as high. Save shipping money AND your back, by keeping the weight down (separate batteries only weigh 33 kg each). If there was only one 200Ah battery weighing in at 66 kg plus weight of packaging (skid or crate mount mandatory), couriers most definitely would charge extra for lifting gear. |
| Q: Can I use your AGM batteries for cranking, what's their CCA rating? | CCA
is a rating which takes into account sub zero temperatures (-18
degrees). Starter batteries are designed to supply cranking current up
to the theoretical peak of 400 amps under such freezing cold conditions. Car and 4WD starter motors have an internal resistance of between 30 and 40 milliOhms, meaning only while spinning up (for a fraction of a second) they consume their maximum inrush current of between 300 and 400 amps. Note that even if the starter motor was mechanically blocked so that it can't spin up, the current will never ever exceed this value (Ohm's Law). Once they're spinning at their rated RPM during cranking, they generate a voltage (back EMF) wich effectively reduces the current through them, typically to 50% of the inrush, say around 150 to 200 amps which is your typical cranking current. Our 12V100Ah AGM deep cycle batteries, when fully charged, are certainly capable of supplying the 400A peak and 200A cranking currents, at above zero temperature conditions, for several minutes. What's more, our batteries feature solid 8 mm lead bar terminals which allow for secure nut 'n bolt clamping, stainless are supplied with our batteries. These terminals have only half the contact resistance of some other designs (threaded screw in terminal post). Thus, they are better suited to high current applications due to less voltage drop at the battery terminals. In a nut shell, due to the deep cycle desing, our batteries are not rated in CCA, but can be used for cranking in above zero tmperature conditions. |
| Q: Can I use your AGM batteries in a 24V system? | Yes you can. Note our recommendations on 24V battery charging. |
| Q: What sort of charger do you
recommend? |
Any two or three stage charger with a setting for AGM, as
long as the charger is rated greater than about one tenth of the rated
battery capacity, and the charger is rated smaller than one quarter of
the rated battery capacity. E.g. if you have two 12V100Ah wired in parallel, your AGM charger would have to be capable of delivering a minimum of 20 A, and must not exceed 50 A. You can still use a smaller charger, but then you'd have to remove one wire connection from the parallel configuration and charge the two batteries separately. Find a battery charger with a boost voltage setting of 14.7V and 13.6V for float charging. This is the specification for all Asian made AGM batteries. There are some mainstream chargers on the market (most notably c-tek) which only deliver a reduced boost voltage of 14.4V when set to AGM. This is in an effort to accommodate so called 'hybrid' batteries which are still popular in the US. Hybrid batteries offer slightly less capacity per volume, compared to the newer alloys employed by Asian manufacturers. Temperature compensation of the charging voltages should be included in the design, especially if it's a higher output model, and/or you intend to float charge your AGM battery over a longer period of time. The temp coefficient should be around +/-24mV/degree, for battery temperatures below or above 20 to 25 degrees (at which temp the nominal 14.7V applies). E.g. if the battery sits at 35 degrees, you want to see a boost charge voltage of around 14.45V, if it's sitting at 10 degrees, a boost charge voltage of around 14.95V should be applied. Same goes for float charge voltages, based on 13.6V. If charging a bank of 24V, individual charging of each 12V AGM battery is strongly recommended. You don't have to disconnect the batteries from the circuit, just switch off all loads and use your 12V charger to charge the two batteries one after another (or use two 12V chargers, one connected to each battery, and charge them at the same time - if you need to keep down recharging times). Using an ordinary 24V battery charger (even if designed for AGM batteries) is NOT the best thing to do. Find out why, by sending us your questions. |
| Q: Can I have my own questions answered/published here? | Yes, by all means just ask away by using the email form below. For the fastest response just use one of the phone numbers below. |
| This is an important bit, I'd like you to read first. | AGM VRLA batteries can be operated in any
position. They can last 3 times longer than ordinary 'sealed
maintenance free batteries'. You cannot operate an ordinary 'sealed maintenance free battery' in any position, because the reality is, they are not 'sealed' at all. They have hidden vents through which the liquid electrolyte would spill! And the plates inside would be taken out of submersion which damages the battery very quickly if you'd draw any amount of current in this position. These batteries cannot be shipped by courier or posted because they're classified "dangerous goods" for a very good reason. Sellers calling these batteries 'sealed' are grossly misleading their customers. In contrast, the more costly to manufacture and long lasting VRLA AGM battery has the following benefits: No gassing because of the recombinant effect inside the glass matting under slightly elevated pressure. The lead plates are housed in a pressure regulated container with pressure regulating relieve valves. These valves only open under severe overcharging conditions. Under normal charging, almost 100% of the generated gasses recombine inside the glass matting and only a tiny amount of gas escapes. Originally designed for the military, this is the lead acid technology of choice and is called AGM VRLA (absorbed glass mat valve regulated lead acid). The active material on the plates' surface is held in place by the glass mat, so that it cannot be 'shed' under deep discharge conditions. Ordinary flooded designs for cranking purposes have very fine active material which is only held in place by electrochemical forces as long as there is a sufficiently high charge remaining in the battery. Once this battery is discharged more than to a shallow DOD, the plates start to shed their active material which just sinks to the bottom of the container (or sometimes envelope separator) where it cannot be recovered through any means of recharging. Beware of 'maintenance free deep cycle batteries' which are not specified VRLA AGM or gel. These are ordinary flooded lead calcium batteries which are worse than their non sealed cousins because their electrolyte level cannot be topped up with water. The only purpose to produce such a battery is, to maximise profits by reducing the manufacturing costs (no threaded openings with seals and caps on each cell). And at the same time dodgy sellers use the notion 'sealed' to imply the advantages of a true VRLA battery which is a lot more expensive to produce and has the above mentioned benefits. 'Maintenance free' is a total misnomer as such batteries should be called 'non serviceable'. Non VRLA 'sealed maintenance free deep cycle' batteries are the worst of them all since these batteries do not have any means of recombining/recycling hydrogen and oxygen which are produced during charging - no matter how well controlled the charging takes place. Thus, they loose electrolyte, through their vents. And this loss of electrolyte cannot be compensated by topping up, because the manufacturer has been cutting corners purely for the sake of increasing profits. A very short battery life time is the result. And the seller who adds the 'deep cycle' bit to the ordinary 'maintenance free', tries to screw you a second time around because any flooded battery rated in CCA or MCA is designed for cranking , and as such is exactly the opposite of a deep cycle design. The negative plates of a starter battery are made of lightweight sponge lead as opposed to thick solid lead in a deep cycle. You can't just add a 'deep cycle' component - this is utter nonsense designed to make a quick profit from unsuspecting buyers. |
| Q: how is shipping calculated and what does it cost? | The
examples on the ebay listing page are just that. Shipping and handling
costs to selected post codes. To get an accurate quote for shipping to
your doorstep, please use the contact form below and send us your post
code Please ensure your delivery address you've on file with ebay is up to date. If payment is made by paypal, we can only ship to this one address. If this is impractical, we offer direct deposit payment terms. Just let us know beforehand. We generally charge a handling fee of $10 which partially covers the cost of the custom made skid and professional packaging of the 33 kg heavy battery. |
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