Sometimes, less is more.

The first time anyone asked me for batteries for their remote-operated automatic mower, I thought, “this guy is nuts”.

After all, I have been using my remote operated automatic mower for three years and NEVER put batteries in him – heck, I didn’t even know they took batteries.  But when this customer explained that he was NOT referring to a mono-syllabic, soda-gulping teenage son who mows his yard, as is the case at our house, I was intrigued.

Apparently, in an effort to prove the stereotype of the fat lazy American under the guise of “Eco-friendly” and “time saving”, Robomow® has developed and sells an entire line of automatic robotic lawn mowers. (For the record, my teenager is not “automatic” but he is easily motivated by potato chips and internet usage). Robomow® claims to “saves you time and effort. Unlike other lawn mowers, Robomow mows the lawn for you” which sounds a lot like a teenager to me, but nevertheless, is really a $1500 lawn mower which runs on batteries!

Honestly, it sounded like a waste of money until I found out the Robomower ran on batteries… In which case The Battery Genius’ official position is this: Everyone should own two of these things! Just kidding.

But I did get a call this morning from a very dissatisfied Robomow® customer who bought some replacement batteries at a local electronics store.

He explained to me, his Robomow® battery pack is 2 – 12 Volt 18 Amp Hour Batteries. He told me that his batteries had lasted him about a year and now he was in the market to replace them.  His question to me was this, “If what really matters in battery power is Amperage, then wouldn’t I be better off replacing my 18 Amp Hour Batteries with 22 Amp Hour Batteries that are the same physical size, but more powerful?”A very good question, indeed. It’s logical to assume something like this when replacing batteries, and if you buy batteries at the Radio “Jack” or your local Smiley-faced discount store that’s probably the answer you’ll get.

However, when comparing Deep Cycle Batteries, or Sealed Lead Acid Batteries for Standby or Cycling, the most important factor is not always Amperage for Power. SOMETIMES, taking in to consideration the design of the battery itself is important to understanding how a battery will perform. (By the way, you can’t get this kind of knowledge at Radio “Jack” or a discount retailer. Rather, only a battery professional like Powerstride Battery can tell you this kind of stuff).

A Deep Cycle Battery’s deep discharge comes from its plate design (they’re thicker than a starting or cranking battery’s plates) and from that battery’s internal chemistry. A deep cycle battery has thicker plates than a cranking or starting battery. Thicker plates allow for a larger concentration of potential energy to remain in the active material (electrolyte)of the battery by slowing the rate of energy released as an electrical current moves through the battery from its positive plates to the negative plates – this is called internal resistance.  Normally, this movement actually decreases the amount of energy a battery has available (it takes energy to make energy), but by using thicker plates, the loss is offset and a nice amperage is achieved for the size of the battery engineered.

Suppose, however, that a manufacturer needs a little more power (amperage) from the same PHYSICAL DIMENSIONS of the battery… What then? Well, a manufacturer has a few options…

1)      It can make the plates inside the casing thinner to increase the amperage – LOWERING the discharge TIME but slightly increasing the Amperage.

2)      OR – they simply remove one or two of the negative plates inside the battery, lowering the battery’s engineered internal resistance and creating a higher internal circuit.

3)      The manufacturer does both – engineering an inferior product.

The problem then, is that you have an engineered product – take the Robowmower for example – that requires 24Volts and a Minimum of 30 Amp hour to run for two hours.  But when a customer uses 2 – 22 Amp hour battery instead of the 18 Amp hour batteries that came installed from the factory, the customer unwittingly LOWERED the amount of run-time by using a battery that can deliver a HIGHER Amperage, but with thinner plates only for a shorter time! which probably leaves his yard half-mowed and his temper a little hot.

To use an analogy here for those of you who love them, think of Twins; one a Marathoner and the other a Middle distance runner who both stand at 6’2” and 170 lbs.  Both can run for a while, but the Marathoner can go for a long long while…

For more information about how your battery performs, and the right one for your application, call the battery geeks at Powerstride Battery Toll Free at 877-5-POWER-9 or visit for more information.

Jul 12th 2010 The Battery Genius

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