Erik, and others
For my charge controller I use a load diversion type controller for all my charging sources.
Mostly thats solar, but the wind generator and regen, or anything else, are also monitored by this controller.
It works differently to a regular solar controller. The normal solar ones are in the line between the solar panels and the batteries, and they throttle back the charge being supplied to the battery. Kind of like putting a kink in a hose when you want to cut off the flow of water.
And sometimes wind generators also have their own controllers built in, which also work in a similar way by limiting the power that is directed to the batteries.
But a load diversion controller works differently in that its not in the line from the charging source to the battery. A diversion controller is connected directly to the battery and watches its voltage. If it begins to get too high is bleeds off enough power to keep the voltage at the correct level. In my case I use a water heating element as the load for this controller, and so I get free hot water whenever the batteries are full and excess power is coming in :)
And all the charging sources, solar, wind, regen are connected directly to the battery without any regulation.
The charge controller needs to be big enough to dump the maximum charge rate that you'd expect to be ever able to come into the batteries. In my case I have a Xantrex C40 which can dump as much as 40 amps to protect the batteries. That could be possible on a sunny day with a gale and the wind generator spinning its head off. The way I do things though I doubt that would ever happen, and usually it just needs to dump excess from the solar panels which can be around 10 amps.
To continue with the water analogy, think of the battery as a water tank, and the maximum level it can be filled to is the maximum voltage. A load diversion controller is like have an outlet pipe set at this maximum level—as soon as the water reaches this level it begins to flow out the pipe. So this means you can fill the tank from any source you like, and its protected from overfilling by this overflow pipe.
A typical solar controller works like a tank with no overflow pipe. But the pipe coming into the tank from the solar panel has to be shut off whenever the tank reaches its top level. If any other charge sources are added, they also need to have their own valve in the pipeline to shut off the flow when the tank reaches top water level.
I hope this helps...
Cheers
Chris
On 26/04/2011, at 8:01 AM, Eric wrote:
Myles, Mark,
This conversation raises a question that I don't think has been addressed here before. Do our controllers have voltage or current limits related to regen? We're lucky in the fact that regen current doesn't show up to any great extent at our typical cruising speeds. But what if we were in regen mode and didn't pay attention for a few hours at high sailing speeds. Could the drive system hurt our batteries? I know that the charger for my Lithium batteries finishes at 60V+ but that is at very low current. At 64V, I would probably damage a cell. Personally, I'd rather limit the regen output to 58V or less.
Do our typical controllers, Sevcon, Kelly, Alltrax, etc. have any kind of charging profile programming installed?
Fair winds,
Eric
--- In electricboats@yahoogroups.com, "Myles Twete" <matwete@...> wrote:
>
> Mark-
>
>
>
> I don't think you have to be too concerned about that voltage unless it
> creeps near 2.5v/cell (60v/string) for a significant time. You were still
> over 5v less than this when you noticed the voltage was high. At
> 2.4-2.5v/cell (57.6-60v), the cells will be out-gassing pretty well, which
> is good to do monthly if you have flooded cells. OTOH, if you have AGM's,
> you would want to keep your voltage below 2.43v/cell (58.32v)
> generally---but I'm no expert.
>
> This looks like a decent reference for AGM charging:
> http://www.mkbattery.com/images/AGMBatteryCharging.pdf
>
> Your Kipoint 3-stage charger will attempt to put 20amps in CI-mode (Bulk
> phase), but will quickly go into CV-mode (Absorption phase, 54.4v) if state
> of charge is above 90% or so...the charge current will quickly drop
> accordingly until it hits a preset lower current limit. You noted 54.89v,
> which is above the CV-mode set point. Certainly the charger would deliver
> very little current when connected to the bank with that voltage. And it's
> likely that the current would drop so low that it could quickly transition
> into the Float mode (51.2v). Unlike the Lestronic, your charger doesn't
> wait for any significant time once it detects current has dropped below its
> threshold before dropping into float---and that's exactly what you're
> seeing.
>
>
>
> -MT
>
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