| Dave: Thanks for your post and link. I'm personally not concerned that having two chargers means more failures. The important thing as you point out is to keep monitoring them when they are in operation . That means using a good battery monitor to me or having some indicator like the LED graph on the Dual Pro. It's one of the reasons I mounted my Dual Pro charger inside the cabin. I wanted to make sure I could see it easily. You do bring up certain concerns about using one of the batteries for running things like a Paktrakr battery monitor off of one of the batteries. Yes, it seems it will cause a little unbalancing of that battery of the bank. But, how harmful vs how helpful it is might be a decision that we all need to make. One could install a switch to shut it off when not in use and that may help. But, then you would have to reprogram it when you turn it on again. You could also run it off of a separate 12 volt supply but, then it would not give you a true total pack voltage reading. In the case of my bank it is constantly being topped up with a solar panel and/or wind generator so I am not as concerned about the Paktrakrs load drainingg the battery too much. Though perhaps a small (5 watt?) solar panel across the one battery with the Paktrakr might help make sure that things stay more balanced (if you don't want to go with a battery balancer like the HDM EQ). Though maybe one only needs to install a single battery balancer between the the third and fourth (paktrakr) battery to account for the 10ma load of the Paktrakr. I think the another question is when is enough enough? Steve has a little more issues than most of us as he has 12 batteries to keep an eye on for his 144 volt bank and more cost if he wants to go the individual (or dual pro) charger route. I think most of us have four or less batteries which makes it somewhat easier and less costly to keep an eye on things. So something like the HDM unit might be the way for him to go. Though it might be the way to go for others who have less batteries and things like the Paktrakkr and are using solar and/or wind for charging. I am thinking it might be the way to go too. Though having invested quite a bit of boat bucks already in two separate charging systems. I am reluctant to spend more for something like the HDM system system at this point. Though it as you point out might be more harmful to the bank if it should ever fail. I think that is Steves concern too. One might not know it right away because of it's limited diagnostics. I think you are spot on that the real important concept for most electric boats is keep the batteries charged and don't go to long between charges and make sure whatever charger you are using that it is working properly and I'd also add matched to your battery banks chemistry. I think we all want to find the best simplest system that keeps are battery bank healthy. There may be many ways to get there.
Capt. Mike .
--- On Tue, 1/4/11, davecover <davecover@gmail.com> wrote:
From: davecover <davecover@gmail.com>
Subject: [Electric Boats] Re: Battery Balancing (again)
To: electricboats@yahoogroups.com
Date: Tuesday, January 4, 2011, 1:42 PM
I thought I'd add a few comments to this post, it seems to be a pretty popular subject. Once again, I'm coming from the perspective of autos, not having a boat yet. First, I'd highly advise against powering anything from one battery in a pack. Even with a low drain (10MA) you will constantly bring that battery out of balance. The longer between charges the more you imbalance the pack. And if you need to discharge the pack fairly deep, even once, for any reason (emergency?), you will have a much higher chance of ruining a battery. The old saying is "Most batteries don't die, they are murdered." It's much better to use a DC-DC powered by the whole pack. This gives you power for all your 12 volt needs (or whatever voltage you need) and respects your pack. You can get some pretty high (and low) efficiency DC-DCs. When looking at multiple chargers, remember that you now multiply the points of failure. Taking it to the extreme, some people use one small charger per battery. This can work fine, each battery gets full attention of it's charger. But now you multiply the chances of something failing. What happens when one fails or a charger gets unplugged by mistake? Will you notice it? As you motor out you could be reversing a battery. You need to monitor your pack very well. But there are some simple (and cheap) techniques for protecting your pack. One of the best (simple and inexpensive) is the Lee Hart regulator. In the auto EV world, Lee is a well respected voice. Basically the regulator is a simple device that will bypass some of the charging current on the "fuller" batteries so the weaker one can come up to charge. This helps ensure that all batteries in your pack get a full charge. It doesn't address all problems, but it is a pretty effective basic protection for standard 12v lead acid batteries. The parts are inexpensive and anyone with a soldering iron can make them. Here's a link; http://www.seattleeva.org/wiki/Zener-lamp_regulatorDave Cover http://www.evalbum.com/2149
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