[RE-wrenches] Off-grid non-inverter battery charger recommendations?

[Drake]

Through a strange set of circumstances, I found a way to equalize 
batteries with an Iota charger.

My DLS 45 was borrowed on a couple of occasions.  I made the mistake 
of telling the borrowers how to adjust the voltage through the 
potentiometer.  Predictably, when I needed the unit, the pot had been 
ruined.  Calling Iota, they said there was no fix. The pot was 
soldered to the board.

The way the device works is that lowering the pot resistance 
increases the output voltage.  My solution was to cut the pot out of 
the circuit board and solder the leads together.  Now with the quick 
charge plug out, it holds at 15.2 to 15.4 volts.  The the quick 
charge plug in, it runs at around 15.7 volts.  I equalized a pair of 
T-105s yesterday without the quick charge plug.  It worked like a charm.

This is much more useful for my needs than the factory 
configuration.  My uses are emergency charges from generators, often 
in cold weather, and equalization charges.  The operation of removing 
the pot was tricky for me, but someone more used to working with 
electronic circuit boards might not find it too difficult.


At 01:27 PM 10/15/2012, you wrote:
>Hi, Mechanix~
>
>Bill Dorsett polled the group about recommended battery chargers for 
>connection to a generator. Iota brand is the successor to Todd 
>brand; I believe Iota bought the designs, tooling, etc. and these 
>have appeal because of the relatively low cost per rated amp. They 
>seem generator tolerant.
>
>The Todd design is a "constant voltage" type charger, 
>however--basically an AC to DC converter with a fixed voltage 
>output. In my experience, the "75 amp" Todd type charger will 
>deliver 75 amps only for a relatively short time when first 
>connected to a low battery. As the battery's voltage comes up that 
>presents a sort of "back pressure" which slows the rate of charge. 
>That's not so bad if one has utility power >always on< to drive the 
>charger, but if an engine generator is running...
>
>The inverter/chargers (with which we are all familiar) begin with a 
>"constant current" part of the charge cycle--aka bulk charge. The 
>charger is determined to sock the battery with the amperage we have 
>requested in the setup; I think a pulse width modulation is going on 
>where the charger hums up its voltage in order to keep the amps high 
>even as the back pressure builds. When it's time for the absorption 
>phase of the charge, the logic shifts to a "constant voltage" where 
>the amps are gradually dialed lower in order to keep the battery at 
>the target voltage so it can "absorb". Ignoring the float phase 
>which would come later, this overall charge regimen would be called 
>CC/CV for "constant current/constant voltage". The CV part of that 
>is not much different from what a Todd style charger does; it's just 
>that the Todd design does not precede that phase with a CC "constant 
>current" phase.
>
>Some free-standing battery chargers have a CC/CV algorithm but those 
>seem to cost as much or more than a comparably rated 
>inverter/charger. Check the Magnum mod-square multi's, Bill, such as 
>their RD series. As others on this List have noted, just the charge 
>function is pretty good and since the inverter circuit is not pure 
>sine, that keeps the cost lower. Built in time delay before it loads 
>up the generator is an added benefit.
>
>Jolliness,
>
>Mick Abraham, Proprietor
><http://www.abrahamsolar.com>www.abrahamsolar.com
>
>Voice: 970-731-4675
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