Sounds like a good problem to have---a fully charged pack while underway J
At that point, the choices include: (1) disable regen, (2) increase throttle, (3) engage dump loads (e.g. perhaps a heater?).
Any of these could be made manual or automatic upon detection of overvoltage.
There are charge controllers on the market that might be able to implement option #3 above.
In the meantime, watch your voltage if you’re an e-sailor with regen or solar or wind power---and know the limits.
-MT
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Eric
Sent: Monday, April 25, 2011 3:02 PM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] regen
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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