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Old 07-01-2012, 08:17   #16
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Re: Best Generator

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Originally Posted by cfarrar View Post
If you look at the 3-stage charging profile for a battery bank of 4 golf cart batteries (~200 amp-hrs?), recovering from an average discharge of 60-80 amp-hrs, I think you'll find that most of your charging will be done at a rate below 40 amps, anyway. So it's probably not a big deal.
You have a good point here, but your math is wrong.

Four T-105 golf-cart batteries in series/parallel have a total capacity of 450AH (not ~200).

If they are only discharged by 80AH, that's about 19% of capacity (so, SOC = 81%) and they won't accept a lot of amperage.

However, if they're down 50% which is where cruisers normally take them, they'll take a lot of amperage .... easily 90 amps or more ... until the SOC increases to 75-80% approx. Thereafter, the charge amperage will decrease quite a bit as they move towards 90-95% SOC.

In cruising service, you're almost never going to get to 100% SOC unless you have BIG solar panels, a good wind generator, or are powering all day!

Bill
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Old 07-01-2012, 08:39   #17
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Re: Best Generator

Pete, we have the Honda 2000i and use it to run a 40 amp 4 stage Sterling battery charger. The Honda has two settings, it runs very quietly powering just the battery charger and only if we connect in the 1.25 kw water heater do the revs increase to maximise the charge.

As Btrayfors says the charger will taper off as it charges. Ours starts our at 42 amps and over the next half an hour will drop to say 30 amps, then down to 20 amps after an hour if we are replacing 40AH of a 220 AH bank. So the last 10% takes forever and we don't bother. You can fool the charger by switching off and then back on again after a minute so it goes back to 40 amps but it still tapers the charge back down.

However, the Honda is a superb bit of kit. If you don't want to heat water or run electric radiators during the winter like us, then you could get away with the 1000i. There are some things on the boat I just want to work on the boat and start first time. The genny is one of them.

Plan on fitting some sort of battery monitoring device as well, so you can see the amps going in and the voltage, useful to see when its nearly full and you want to call it a day rather than just sitting there hoping. At full charge it will run for 7 hours on a tank full of fuel so gives us heating from midnight until 7am when one of us has to crawl out from the duvet.

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Old 07-01-2012, 08:53   #18
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Re: Best Generator

Bill,

Thanks for the correction. I have a 420 amp-hr AGM bank. My charging profile is similar to Pete's, and I rarely use the full capability of my alternator or charger. Typically the charge rate is less than 30 amps after less than 30 minutes. Colin
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Old 07-01-2012, 09:20   #19
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Re: Best Generator

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Bill,

Thanks for the correction. I have a 420 amp-hr AGM bank. My charging profile is similar to Pete's, and I rarely use the full capability of my alternator or charger. Typically the charge rate is less than 30 amps after less than 30 minutes. Colin
Colin,

You must keep your batteries at a high SOC, i.e., only draw down a little amperage. Those 420AH AGMs should be able to take 400 amps or more charging current (yes, 400 amps), so if you're only seeing 30 amps after less than 30 minutes then they're at a high SOC already or the charging voltage is too low.

Another possibility: the AGM's capacity has been greatly reduced -- as happens with them after 3 years or so when they've not been fully charged regularly and have become heavily sulfated -- and then they'll only take a little charging current. I have a small AGM on my bench right now which is 3 years old and will only take 0.7 amps charging current @ 14.3VDC. Normally, at this SOC it would take 20 amps or so. The smart charger says, "F03" which means "heavily sulfated or won't take a proper charging current".

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Old 07-01-2012, 10:08   #20
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Re: Best Generator

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You must keep your batteries at a high SOC, i.e., only draw down a little amperage.
Yes, that's right, Bill. We're usually down by 40-50 amp-hrs in the morning. Using the engine to raise anchor and hoist sail re-charges us halfway, by which time the MC-612 steps into acceptance mode and the charge rate drops. I shut down the engine and let the solar panels do the rest (they put out 12.5 amps with good sun).
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Old 07-01-2012, 10:19   #21
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Re: Best Generator

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Originally Posted by cfarrar View Post
Yes, that's right, Bill. We're usually down by 40-50 amp-hrs in the morning. Using the engine to raise anchor and hoist sail re-charges us halfway, by which time the MC-612 steps into acceptance mode and the charge rate drops. I shut down the engine and let the solar panels do the rest (they put out 12.5 amps with good sun).
Colin,

Great! AGM batteries and gels have a much higher charge efficiency than do flooded cells, particularly at high SOC.

So, it takes significantly less energy to replenish those 40-50AH in your AGMs than it would with flooded batteries at a similar SOC.

Cheers,

Bill
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Old 07-01-2012, 17:37   #22
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Re: Best Generator

As mentioned, we have about 440 Ah in our house bank. If we cycle between 80 and 50% SOC each day (ie, approx 132 Ah) I suspect we'd be running our Honda generator with 40 Amp battery charger 4-5 hours per day. Does this sound about right? We'd probably only get 100% SOC on those days we happened to be motoring for quite awhile.
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Old 07-01-2012, 18:16   #23
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Re: Best Generator

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As mentioned, we have about 440 Ah in our house bank. If we cycle between 80 and 50% SOC each day (ie, approx 132 Ah) I suspect we'd be running our Honda generator with 40 Amp battery charger 4-5 hours per day. Does this sound about right? We'd probably only get 100% SOC on those days we happened to be motoring for quite awhile.
Pete
Pete,

Yes. That's about right. And, that assumes that your 40A charger is capable of sustained 40A output.

Here's another way of looking at it.

You think you'll be using about 132AH, and the house bank will be cycling between about 50% and 80% SOC.

Between these parameters, the battery charge efficiency is likely to be on the order of 80% (flooded batteries).

So, you'll need to input a total of 132AH plus 20% or 16.4AH for a total of 158.4AH. Even with a maximum sustained output of 40A, this would be:

158.4 divided by 40 equals 3.96 hours

And, of course, you won't achieve that efficiency in the real world.

So.... as I noted early on, you have a generator which is (just) powerful enough to handle a 75-80A charger (unless you use one with PF correction which would be a bit larger), and your batteries can easily take that amount in bulk and absorption modes.

To me, it's a no-brainer, unless you really like the sound of the little Honda generator!

Bill
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Old 07-01-2012, 18:27   #24
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Good explanation, Bill. You make a good case for a bigger charger. Additional ideas: reduce Ah consumption (LEDs, etc) and/ or add a solar panel. C
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Old 08-01-2012, 03:35   #25
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Re: Best Generator

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Originally Posted by btrayfors View Post
Pete,

Yes. That's about right. And, that assumes that your 40A charger is capable of sustained 40A output.

Here's another way of looking at it.

You think you'll be using about 132AH, and the house bank will be cycling between about 50% and 80% SOC.

Between these parameters, the battery charge efficiency is likely to be on the order of 80% (flooded batteries).

So, you'll need to input a total of 132AH plus 20% or 16.4AH for a total of 158.4AH. Even with a maximum sustained output of 40A, this would be:

158.4 divided by 40 equals 3.96 hours

And, of course, you won't achieve that efficiency in the real world.

So.... as I noted early on, you have a generator which is (just) powerful enough to handle a 75-80A charger (unless you use one with PF correction which would be a bit larger), and your batteries can easily take that amount in bulk and absorption modes.

To me, it's a no-brainer, unless you really like the sound of the little Honda generator!

Bill
Thanks. My problem now is I just bought and installed a Xantrex TrueCharge 2 40 Amp charger along with remote control panel. I even re-did my instrument panel to accommodate several new pieces of electronics including the remote control panel. Naturally, this charger works great when on shore power and time to charge is not an issue.

I'm trying to figure out how to keep what I have, but also accommodate an inexpensive 75 or 80 Amp charger that would be used in conjunction with the Honda. I have thought of a separate charger with a direct connection between Honda and that charger. The issue is largely about money since the Honda is a big enough investment without having to buy a 2nd charger. Any ideas? I do fully appreciate the merits of what you say; it sounds like I may be able to cut my charge time to nearly half.
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Old 08-01-2012, 04:10   #26
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Re: Best Generator

I just had another idea. Why not purchase a 2nd 40 Amp charger and run the two in parallel when the Honda is in use? That saves money (as compared to a 75-80 Amp charger) and adds a level of redundancy. I'm not sure if the outputs from the two chargers would conflict though. Maybe if they were the identical make and model (ie, Xantrex TrueCharge 2) it would be ok?
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Old 08-01-2012, 05:47   #27
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Re: Best Generator

I just discovered on the manufacturer's website that my Xantrex True Charge 2 40Amp can be paralleled with another one. That would offer the following advantages:
- redundancy
- less expense buying another 40 rather than replacing mine with a larger one
- allow use of other AC such as appliances since it's a permanent install
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Old 08-01-2012, 08:38   #28
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Quote:
Originally Posted by prroots
I just discovered on the manufacturer's website that my Xantrex True Charge 2 40Amp can be paralleled with another one. That would offer the following advantages:
- redundancy
- less expense buying another 40 rather than replacing mine with a larger one
- allow use of other AC such as appliances since it's a permanent install
Pete
Many of the manufacturers state their chargers can be paralleled - I am looking at Victron. I am in the beginning stages of planning but I will definitely weigh the cost of two 40s against the cost of those vs one 80. The redundancy is a bonus.

If I were in your boat (pun) the second 40 would be thenlogical step.
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Old 08-01-2012, 08:47   #29
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Re: Best Generator

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Many of the manufacturers state their chargers can be paralleled - I am looking at Victron. I am in the beginning stages of planning but I will definitely weigh the cost of two 40s against the cost of those vs one 80. The redundancy is a bonus.

If I were in your boat (pun) the second 40 would be thenlogical step.
Thanks. Yes, it looks good except that the generator may not provide enough current to feed both during the bulk charge stage. It's been suggested on another forum by Maine Sail that I measure the exact current draw on my one 40 Amp charger to see if twice that can be handled by the Honda. Seems like a plan. In the meantime, I'm looking for the best price on a Xantrex True Charge 2 40.
Pete
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Old 08-01-2012, 08:52   #30
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Re: Best Generator

i have had two honda eu2000i generators, one had been dropped in the drink and no amount of servicing could bring it back. it worked for a bit then all the electronics corroded, after we cleaned all accessable connections and the oil, and pretty much everything we could think of we did. my old man bought a new one for himself and it runs beautifully, just beware that they have a lot of hidden electrics which can become problematic in corrosive environments.

At the moment i have a honda ex1000 mainly for charging batteries, bomb proof non inverter style generator. It is not as quiet and burns a little more fuel, but it starts first time, and can be fixed without having to order half the generator inparts when it stops working.

most importantly, go with a honda. it's worth the piece of mind.
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