Hi Eric,
My project is still evolving and I expect it will some more as I really get to use it in action.
I am using the TS90 Control Unit, but I haven't used its relay to disconnect the load if the voltage drops too low. It has an alarm and I'm relying on that to warn me when voltage is low, and to then manually disconnect the power.
I'm a bit leery about having a device that can shut off my power in an unexpected way. I could be in a critical manouvre and could decide to sacrifice the battery to avoid crashing into a dock for example. With the alarm I can still respond quickly but its in in my control. Since getting the Torqeedo though I will be adding another external alarm - because it has a high pitch which is similar to the pitch of the alarm, and both sounds come from a similar location on the boat, the alarm is not so audible now from certain locations on board.
The last time the alarm went off it was totally unexpected - only about 50 ah had been discharged from the pack, and the pack voltage was still high. But I was in a position to be able to shut off the motor right away. I then looked at the pack to see which cell it might be that was triggering the alarm - and indeed on one of the cell modules the green LED was unlit - indicating low voltage. I checked the voltage of this cell and it was fine - around 3.2 volts. So I figured it was a failure of the cell module, or the contacts were dodgy. So I continued on the dock.
It could be the contacts that are oxidised that is giving trouble but even so I've ordered another cell module to have as a spare.
My battery pack is in a difficult position under the cockpit and when I wiggle in under there its quite cramped and the furthest cells are at arms length. Its quite a long winded exercise to remove a cell module - they are all soldered together in a daisy chain and so they have to be removed as group. One way or another I've procrastinated this project and its still awaiting final trouble-shooting.
Because the pack is in a difficult position I've run a wire pair to each cell and led them to a more accessible position. They come to a board which has sixteen jacks that allows me to easily test voltage of each cell. It also allows me to put a small charger on an individual cell if it needs topping up. I did this right near the start when I was having trouble figuring out the cell balancing, but now they've balanced the small charger does not seem to be needed.
I don't have an AC charger - all recharge comes from solar or wind.
Regarding solar panels, have you checked out solara panels? These are only a few mm thick and you can walk on them - so they can be stuck to the deck wherever you want. Although I would not want them in a high traffic area. But it is a nice way of mounting panels without windage and the unsightliness of the usual solar panel mounting towers.
I think you are right about not expecting any regen. When I had the Epod it only produced useful power from around 7 knots - so for a fast multihull its a possibility but for your Bermuda 30 its unlikely to be a useful source of recharge.
Cheers
Chris
On 03/11/2009, at 8:26 AM, Eric wrote:
Chris,
It's good to hear from you. I spent the morning reading just about everything on your boat's website, so I've only got a few more technical questions about your storage system. I also own a Farrier F-27, so I understand your focus on weight. Interestingly, my Cheoy Lee Bermuda 30 has serious space constraints that is leading me to an LiFePO4 solution, the initial plan is for 16 LFP160AHA for a total of 7.6Kwh. If all goes well, I could always add a second bank of the same to double the capacity/range. I have understood many of the additional benefits that you described in your post, but it's nice to hear that these bonuses are more than just theoretical.
I see that you're running the BMS cell modules from EV Works on each cell, I was already planning on doing same thing. Are you also running their MCU-TS90? I can really see the advantage to having a low voltage shut-off. I read about your experiences with charge balancing, have those issues become less prevalent now that your bank is more balanced? What kind of A/C charger are you using? Since my boat lives in a berth in a marina, I plan to utilize shore power for almost all of my charging.
For my project, there's really no good space for solar panels on Serenity; narrow beam, low booms and a sail plan that extends a couple of feet past the stern. With a full keel and a prop in an aperture, effective regen seems unlikely. The top of the mizzen mast may be optimal for a wind generator, but that will have to be release 2.0 of my project. My backup will be a Honda generator to run the shore charger, but I want to keep that to a minimum.
Fair winds,
Eric
SoCal
No comments:
Post a Comment