charger/inverter selection and updating electrical system on a Gulfstar 37

rmeador · #1 08-24-2010

So I just bought my first boat, a Gulfstar 37. It hasn't been surveyed yet (and I guess technically it isn't mine yet, since I can still reject it...), but when I looked at it I saw what I think is the battery charger, and it is some metal box that looks like it's from the 70s. The boat was built in 1979, so this isn't impossible. I'm told it's been on a mooring for the last 18 years (at least two owners worth), so it probably hasn't been connected to AC power in a long time. I assume I'll need to replace the charger. I have no idea how many amps I'll need. My understanding is the battery charger powers all your 12V equipment when AC power is available. I'll be living aboard, and I'll be adding 12V refrigeration.

If I'm going to go to the expense of replacing the charger, I'd like to do it right. I'd like something that can do in-depth monitoring and management of the batteries (unless this is best accomplished with a separate device -- advice?). Though I don't really need it (I have no plans to be away from the dock for extended periods), if the additional cost isn't too high, an inverter would be nice. I'm pretty sure if I'm going to ever get an inverter, it will be the type that's built into a charger because I like the seamless switchover you get when the dockside AC is disconnected -- none of your AC electronics lose power. I probably want a pure sine wave inverter.

Another thing I probably don't need since I have no plan to use right now is a solar charger, but again, if it could be a feature of the main charger/inverter and could be had for only a little more money, I'd like to go for that. I don't know when/if I'll be adding solar panels, but I'd like to have the controller built into the rest of the electrical system rather than tacked on if I ever do it.

Any suggestions on models that meet some or all of these requirements? Are my requirements insane? I don't want to spend too much money.

mitiempo · #2 08-24-2010

I'd monitor with a separate device like either a Link type product from Xantrex or the comparable type unit from Victron.
You want pure sine wave and that puts invertors into the upper price range. Modified sine wave will be less expensive. Here's a link to a Xantrex 3000 watt invertor (pure sine wave) with a 140 amp charger built in. About $1200. There is also a 2000 watt unit.
You say you would like a seamless switchover when unplugging. How much would you like to run with the invertor? Unless the invertor is very large most manufacturers recommend that you wire the invertor from a breaker on the AC panel and output it to a sub panel with no really high loads powered by it. You really need a list of the AC items you would like to use when away from the dock and then add up the totals to see what size invertor you need.
And remember while invertors are nice, a 1000 watt microwave will pull about 84 amps from your battery bank, a 1500 watt water heater about 126 amps.

hellosailor · #3 08-24-2010

"I have no idea how many amps I'll need."
Wait for the surveyor, and don't be surprised if you need to start from scratch will new batteries. Blueseas and some other vendors have a lot of good information online about options and choices. It can be a lot to absorb, and if you aren't familiar with this stuff, an un-pressured reading of a couple of classic books like "the 12 volt bible" will help.
As you get familiar with the options--and the way they interact and push your budget--you may rethink things. The older charger, if it is running right, may still be quite adequate. They can literally last 50-100 years if they were built right. And you're lucky.

mitiempo · #4 08-24-2010

100 years? You have evidence of this?

But you're right there are a lot of options. Most would plan not to use AC when away from the dock any more than necessary. A microwave using 84 amps for a few minutes is not much of an issue but water heaters and other items are a large draw from your batteries and best avoided. You might find that a unit like the Xantrex Freedom HF 1800 will do the job (if you need a charger) at 1800 watts and 40 amps charging.

rmeador · #5 08-24-2010

I would of course turn off the hot water heater when using the inverter, and I don't plan on having a microwave (we'll see how long that lasts, but I've noticed I only use the one I have in my apartment about once a week). The big thing I want to use away from the dock is my desktop computer (music and movies; draws 220W according to the UPS I have it plugged into now).

I like the idea of having a separate panel for inverter-powered circuits, I'll probably do that. Then again, perhaps I'll forgo the inverter entirely.

Is 40A a good charge capacity for my usage? If I do need to replace the batteries, I'll probably go to a 3 battery system, 2 for house 1 for starting. I have no idea how to estimate the amount of charge capacity required... obviously anything larger than the current draw of the 12V devices will charge the battery, but slowly. And there is a point at which a bigger charger will not charge faster...

I looked up the Link unit recommended above for monitoring... it was surprisingly hard to find online -- it doesn't appear to be on the Xantrex site. Anyways, that's an expensive little bugger. It stands to reason that one built into the charger would be cheaper. Is there a reason for recommending a separate unit?

I'm an electrical engineer, so I have more than a little knowledge about electricity, and I'm quite capable of doing all the work myself. My expertise is in microprocessor system design, not power systems, however. I just don't know what products are out there, which ones are good and bad, how to get the most bang for my buck, and what features/capacities I really need. Thanks for the help so far!

mitiempo · #6 08-24-2010

I don't know of a good monitor currently built into a charger. Most have a small control panel that is removeable for remote mounting that only give you minimal information. A typical one is shown below. Xantrex has apparently discontinued the Link 1000 and 2000 which were designed to be full battery monitors and control invertor/chargers as well. But they were more expensive than a good monitor like the Linkpro. They are on the Xantrex site but are under accessories I believe. If you know the specific model and google it you can go direct to the proper page like here. Xantrex Technology Inc. - LinkPRO Battery Monitor - Product Information
The Victron I mentioned is a good unit and more affordable as well. The BMV-600 is $175 at Jamestown Dist. Victron BMV 600 Battery Monitor
and a 2 bank monitor is available as well but not really necessary.

As far as charger size you ideally want one that is rated at about 20% of the house bank size. The 40 amp unit I mentioned was just an example.You may decide to install a separate charger and buy a small invertor for your needs instead of the combination unit. The best way to charge the start battery is through either an Echocharge, Duocharge, or ACR. It is seldom down more than a few AH if only used for engine starting. All charging ideally goes to the house bank direct and avoids the master switch (1/2/both/off). The 3 items I mentioned will either pass current to the start battery when a charge current is sensed (the first 2) or parallel the batteries as the ACR does.