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**mmichellich** · 07-31-2012, 01:04 PM

dddd666 wrote:
Hi All-

At the end of last season we installed a new Xantrex SW 3000 inverter/charger on our 3988. When connected to shore power it does a great job of keeping the batteries topped up. and it even allows us to equalize all our batteries. This is important as we have sixteen house batteries that are all interconnected. When we are underway, however, we find that that the charging of the batteries via the 8K Westerbeke takes a lot longer than we'd like. Five hours of running the genny is not enough to get the batteries to the "absorb" level, let enough "float". Does anyone know if there are any "tweaks" that can be applied to get a faster charging rate? As ususal, TIA for all of your help.

-Don.

Underway you might be seeing interference between the alternator and the inverter/charger, dramatically reducing the charging rate. I would never equalize my batteries, but that is just me an electrical engineer. What rate is the Xantrex charging while underway using the gen set? Why not just let the alternator do the charging while underway? I have never had to run the gen set/inverter/charger and alternator while underway. Most Xantrex chargers can be set for a max charge rate so you do not blow a shore power breaker, has it been throttled back? How low do you let your inverter batteries get. Any lower than 50 % discharge is depleting the life of the batteries way too fast.

**dddd666** · 07-31-2012, 01:47 PM

Thanks for responding so quickly. As far as I know the alternator only charges the 8D starting batteries & is isolated from the house batteries so I can't imagine any interference. Regardless, it seems to be the same whether underway or when running the genny at anchor. The charging rate appears to hover around 12 amps. Sometimes 0.1 amps more or less. The max charging rate the Xantrex is set for is 100%. Battery size is set at 1760 (flooded). AC limits are set to: Low 90 V/ 55 Hz Max: 135 V/ 65 Hz. I understand the problem with letting the batteries get too low. I never let them get below 11 V and try to keep them at 13V or above.

**Guest** · 07-31-2012, 02:18 PM

Pull out your Xantrex manual and check the section on setting "floor" levels. You should never discharge as much as you are. 11.89V is 0% charge, or 100% dead. 11V is deader than dead. Zombie batteries. You're shortening you battery life drastically. Never discharge below 12.24V.

Next, check the manual for limiting shore power demand. You say you're set for 100% but I think the read out is in amps of shore power load. You want this to be 50A or higher.

**WhiteRockMike** · 07-31-2012, 02:25 PM

Wow - something isn't right as you inverter charger should have a max rate of somewhere around 120amps for that size inverter (our 2500watt Trace has 120 amp charger).

Btw, 11 volts is essentially a dead battery - I think about 5 or 10% capacity remaining, so if you let the batteries get that low several times you may have damaged them. What happens then is when you start charging, the batteries build up a quick surface charge and voltage, that then tells the charger to throttle back to a low charge rate.

**mmichellich** · 07-31-2012, 03:17 PM

At 11.0 volts your batteries are at zero charge-dead at minimum load and no charge. 11.1 volts is 10%, 12.1 is 30%, 12.3 is 50%, 12.5 is 70 %, 12.6 is 100%, with no load and no charge going in. This all assumes lead acid batteries. You should be charging your batteries at a minimum of somewhere around 13.8 volts with minimum loads and 14.0 at full charge. You boat should have been wired so that one of your engine alternators should charge the house and or inverter batteries and the other alternator charge the start battery. The gen set battery is charged by the gen set alternator. If you added independent inverter batteries, they should have wired them so one alternator charges them efficiently and not require any gen set charging while underway. Right now it appears there is something wrong with how the inverter charger is set up, so a deep review of the Xantrex manual for the control panel is in order. I have one of those Xantrax inverters but 2500 in my motorhome and it took me a couple of weeks to get everything set like I needed it. The percent charge reported on the control panel I find is very inaccurate and I only depend on voltages. Make sure you have the control panel manual and not just the inverter manual. You should be able to download them from the internet easily.

**Uncle_Bob** · 07-31-2012, 04:29 PM

The genny is providing 110V and shorepower is providing 110V so there should be no difference which source supplied the 110V. I am betting the shorepower is equally as slow but not noticeable since it is always active in the berth. I need almost 90 minutes of genny time with my 100 amp charger to replenish 6 golf carts from 70%. Five hours does not seem out of line for 16 golf carts well below 50%. Why 16?

**mmichellich** · 07-31-2012, 04:45 PM

1760 amp hours of batteries would take over 17 hours to fully charge them if discharged to 11 volts charging at a rate of 100 amps. I can not imagine discharging 1760 amp hours before recharging.

**ksanders** · 07-31-2012, 11:11 PM

There's been a bunch of great advice so far!!!

The xantrex sw3000 can charge at up to 150 amps.

The challenge is that it's common to drop down the max AC input current setting as to not overload a 30 amp shore power feed when considering other loads (on the shore power).

If you set the incoming AC to a higher number then you'll be able to charge at the max rate, just watch your loads.

You should really also consider a battery monitor system. That way you can accurately determine the best time to recharge based on amp hours.

**Guest** · 08-01-2012, 07:40 AM

mmichellich wrote:
At 11.0 volts your batteries are at zero charge-dead at minimum load and no charge. 11.1 volts is 10%, 12.1 is 30%, 12.3 is 50%, 12.5 is 70 %, 12.6 is 100%, with no load and no charge going in. This all assumes lead acid batteries. You should be charging your batteries at a minimum of somewhere around 13.8 volts with minimum loads and 14.0 at full charge. You boat should have been wired so that one of your engine alternators should charge the house and or inverter batteries and the other alternator charge the start battery. The gen set battery is charged by the gen set alternator. If you added independent inverter batteries, they should have wired them so one alternator charges them efficiently and not require any gen set charging while underway. Right now it appears there is something wrong with how the inverter charger is set up, so a deep review of the Xantrex manual for the control panel is in order. I have one of those Xantrax inverters but 2500 in my motorhome and it took me a couple of weeks to get everything set like I needed it. The percent charge reported on the control panel I find is very inaccurate and I only depend on voltages. Make sure you have the control panel manual and not just the inverter manual. You should be able to download them from the internet easily.

Careful with using voltage as an indication of battery condition. The numbers you are quoting are NO LOAD VOLTAGE. Put any sort of a load on the batteries (which is usual in a boat) and everything changes.

A battery at 11.8 volts with a load on it is not near 1/2 discharge! For example put 100 amp load on a house set with a 500 ah capacity and the voltage will drop as low as 11.8 volts. Switch to no load and it will go up to 12.5 volts. Boats are seldom at no load and even a 10 amp draw with throw the numbers above out of wack.

**ksanders** · 08-01-2012, 07:52 AM

lolar3288 wrote:
Careful with using voltage as an indication of battery condition. The numbers you are quoting are NO LOAD VOLTAGE. Put any sort of a load on the batteries (which is usual in a boat) and everything changes.

A battery at 11.8 volts with a load on it is not near 1/2 discharge! For example put 100 amp load on a house set with a 500 ah capacity and the voltage will drop as low as 11.8 volts. Switch to no load and it will go up to 12.5 volts. Boats are seldom at no load and even a 10 amp draw with throw the numbers above out of wack.

Exactly!

Thats why we use a battery monitor that counts Amp Hours in and Amp Hours out.

**mmichellich** · 08-01-2012, 07:58 AM

lolar3288 wrote:
Careful with using voltage as an indication of battery condition. The numbers you are quoting are NO LOAD VOLTAGE. Put any sort of a load on the batteries (which is usual in a boat) and everything changes.

A battery at 11.8 volts with a load on it is not near 1/2 discharge! For example put 100 amp load on a house set with a 500 ah capacity and the voltage will drop as low as 11.8 volts. Switch to no load and it will go up to 12.5 volts. Boats are seldom at no load and even a 10 amp draw with throw the numbers above out of wack.

On our boat no load is easy to come by, just temporarily shut off the DC Main breakers, shut off the inverter, and the power breaker to the inverter charger.

**dddd666** · 08-01-2012, 12:50 PM

Thanks to all for your helpful comments. I am currently (no pun intended) running some tests to confirm exactly what is going on. First, I confirmed that the alternators DO NOT feed into the house bank. Neither port or starboard engine shows any charge going to the house batteries. Right now I'm at dockside with 15 amp service. The recharge rate so far is:

11:30 AM 12.6 volts at 87 amps

12:00 PM 12.7 volts at 45 amps

12:42 PM 13.1 volts at 83 amps.

I'll keep you posted on my progress.

Thanks again,

-Don.

**mmichellich** · 08-01-2012, 01:39 PM

dddd666 wrote:
Thanks to all for your helpful comments. I am currently (no pun intended) running some tests to confirm exactly what is going on. First, I confirmed that the alternators DO NOT feed into the house bank. Neither port or starboard engine shows any charge going to the house batteries. Right now I'm at dockside with 15 amp service. The recharge rate so far is:

11:30 AM 12.6 volts at 87 amps

12:00 PM 12.7 volts at 45 amps

12:42 PM 13.1 volts at 83 amps.

I'll keep you posted on my progress.

Thanks again,

-Don.

The Xantrex control panel with only 15 amp shore power should be set showing you only have 15 amp shore power avail. When you do that, the charger should then use no more than half that avail current for charging or about 7.5 amps of AC which should charge batteries at about 90 amps DC max. Then when you have 30 amp shore power or are on gen set change control panel setting to 30 amps and you should then get the max rate of the charger, I think you said 150 amps DC.

**WhiteRockMike** · 08-01-2012, 01:46 PM

dddd666 wrote:
First, I confirmed that the alternators DO NOT feed into the house bank. Neither port or starboard engine shows any charge going to the house batteries.

Don, unless you've actually checked the alternator wiring, the fact that you're not showing any charge to the house batteries could simply mean you have a bad alternator or a bad ground or connection. It would be a very unusual setup to not have any house battery charging available from at least one of your alternators.

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