Optimate 5 Voltmatic charger on test
Story snapshot: Useful and worth buying. But we've had some concerns and doubts that needed addressing (see update)
We've been handed an Optimate 5 Voltmatic battery charger gizmo, so now we're supposed to say something deep and meaningful about it. And we certainly would if we could. But the fact is, when it comes to a battery charger, it's very hard to deliver anything profound, or witty, or insightful. These things are like smoke alarms, ain't they? You stick 'em someplace sensible and then you go about your daily grind secure in the knowledge that the little piece of high tech gadgetry will do its duty and will make your life easier and safer, etc.
Until recently, we'd mostly been using an old battery charger that we bought about ten years ago at Halfords or somewhere. Part of it broke soon after, and so we bodged it and used it, but were always a little suspicious of it. Sometimes it worked. Once or twice it tried to cook a battery. And once or twice it left us with a flat battery, and we never got to the bottom of that. This Halfords battery charger gave us no clue to the charging rate. It just flashed lights that read CHARGE or BE PATIENT, WILL YA? Or words to that effect.
So we found a genuine "classic" 1960s battery charger at a boot sale and bought it for a couple of quid. It was housed in a (oh-oh) rusty metal casing, had a toggle switch for 12 volts or 6 volts, had a broken earth wire, an old-style ammeter, and a dangerous selectable fused-voltage thingy on the side that gave us a jolt every so often when we mishandled it. But it looked kinda cool in a ridiculously-long-past-its-sell-by-date sort of way. And as long as you treated it with mucho respect, and didn't stand in any nearby puddles or wear a pacemaker, it was safe enough. The wiring inside, incidentally, was found to be lethal and came to pieces in our hands. So we found a length of modern flex and sorted it out. And to lower the charging rate for bike batteries, we used an in-line 12 volt headlight bulb, and that seemed to do the job.
Sometimes.
But that's probably history now. So is the Halfords bodge-up box. Instead, we're giving this Optimate 5 system a long workout with a view to keeping it. Why? Because it's very solidly built, is easy to plug in and play, works on our 12 volt and 6 volt bikes, and switches between voltages automatically.
Also, it was free.
This Optimate 5 monitors and restores sulphated batteries (or so say the manufacturers), and we'll try that sooner or later and will report. The leads and clips look pretty well designed, and the kit comes with a plug-in take-off point that you can hard wire onto difficult-to-get-at batteries and access conveniently. And we particularly like the nice long mains lead supplied with this device, plus the fact that it's got provision for mounting on a wall or a board or something.
If, like us, you're a bit slow waking up to this modern battery charging/battery recovery system stuff, and if you're as stupid as we are sometimes (and are stubbornly using dangerous old/low/classic tech chargers), you might want to lift your head from the pillow of your rose-tinted lethargy before you set your house alight.
Old battery chargers are potentially dangerous, and you certainly don't want to be leaving them on overnight. So okay, we're (sometimes) a particularly suspicious bunch here at Sump and ain't quite ready to sleep with the Optimate shifting volts around from one part of the garage to another. But we're getting there.
However, we do have some concerns with this thing. Firstly, the Optimate instructions reckons it's charging at the rate of 2.8 amps for a 12 volt battery, and 4 amps for a 6 volt battery, and that sounds too high to us. The usual rule of thumb for the charging rate is around 10 percent of the battery's amperage rating. In other words, our 14 amp/hour Triumph TSX battery should be charged at around 1.4 amps per hour—and that's half of what this Optimate device delivers. Meanwhile, our old 6 volt BSA battery is rated at 4 amp/hour, and that should be charged at around 0.4 amps. That, at least, had long been our thinking.
So maybe the circuitry of this charger knows things that the homespun battery experts don't know (and we've no doubt that it knows a lot more than we know). Apparently it delivers a "float charge" and enjoys "rest periods".
But 2.8 amps? And 4 amps? We're looking into it and will let you know as soon as the Optimate boffins bring us up to speed. Also, note that if you try to charge a battery that's got less than 8 volts available, this Optimate will treat it as a 6 volt battery—at least until you follow the override procedure to re-educate the device (see the included instructions for that; it's simple enough).
Beyond that, the Optimate 5 readout is complicated. It's got lights and symbols and processes and stuff, and you need to study the instructions for twenty minutes to see and understand what's going on. However, for most purpose, most of the time, you just plug the device into the mains and hook up the leads and then go and take care of the rest of your business.
The Optimate 5 costs around £75 depending on where you buy (tip: don't risk a cheaper eBay knock-off).
Our guarded verdict so far (December 2015) is that this kind of trickle-charging/battery maintenance tech is probably worth investing in, and Optimate has some cheaper models in their range if you don't need 6 volt charging. But we've gotta check out that amperage question. We're hoping that we haven't already wrecked the four batteries we've been experimenting on.
The scientists and designers at Optimate are probably way ahead of us, but we're gonna have to get them to pull over and explain things a little. There are questions oustanding...
UPDATE: We've received this reply regarding the Optimate. It makes for interesting (if technical) reading. But it certainly addresses our concerns. Here's the text in full:
Regarding your concerns over this models charge current. Although the charger delivers 2.8A in 12V and 4A in 6V please bear in mind this model uses TecMate’s Ampmatic™ processor which, during the constant current stages, the processor monitors the change in voltage of the battery every second and compares with the previous reading.
Should the battery voltage be deemed to be rising too fast, the charger reduces the current and likewise if the voltage increase was too low the current is increased. The initial current delivery starts at just 400mA and within a few seconds the charger will find the optimal current for the battery. The OptiMate 5 Voltmatic™ is only the second retail charger from TecMate to use the Ampmatic™ processor, the other being the OptiMate 6.
You may even see two charge rates listed on some batteries the first being the 1/10th of the capacity x 5 hours, the second being ½ capacity for 1 hour. However the latter normally only used for AGM batteries.
The reality for an ideal recharge rate for any lead acid battery roughly 1/3rd of the 10hr rate. So for a battery with 9Ah capacity at the 10hr rating the maximum safe current would be 3A. However this should only be used if the battery is flat rather than deep discharged. With a deep discharged battery a different method needs to be employed, using a much lower current and an increase voltage cap.
The reason for this is that much of the reactive material in the battery is lead sulphate crystals, and the higher voltage overcomes the higher impedance of the battery in this state. Once the battery starts to accept current more readily, or when two hours have passed, the charger drops back into the normal charge cycles. As OptiMate chargers assess the state of charge of the battery automatically and set the charge program accordingly, there is no need to worry about what is the best course of action. Just plug it in and away you go.
— Dexxion
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