Battery Charger, Shore Power and Generator?

[motion30]

I could use advice from the experts on my plan. I have 2 55 amp iotta chargers I am installing in my boat with 30amp shore power. The chargers need 13 amps each so 13+13=26 not much left over for anything else so here is my plan, wire one charger up to shore power, wire the second charger up to the no 2 leg of my 8kw generator ,that way at anchor with the generator running I will have 110 amps charging capacity , when docked and hooked to shore power I will have one 55amp charger Is this a good plan or is it flawed.? I would like not to incur the expense of installing another 30amp service on the boat right now
Thanke in advance

[senormechanico]

The 13 amp draw is maximum and would only be when you have first plugged in, and only when your batteries are quite discharged. When they're floating after a charge, they won't draw much at all.

Steve B.

[camaraderie]

I suggest you wire everything normally and simply have breaker switches to enable you to turn off one or both of the chargers when you will be using other stuff at dockside. If you are normally plugged in...the ACTUAL draw will be minimal as the batts will only be drawing an amp or so to stay topped.

[S/V Illusion]

You didn't indicate how large your house bank/banks is/are.
Why would you even consider connecting both chargers?
Do you have sufficient battery capacity to warrant use of two 55 amp chargers?

[camaraderie]

Anyone with a decent sized bank of AGM's...say anything over 400ah's could really benefit from 110amps of charging...You'd need around a 700ah bank to make it worthwhile for wet cells.
The BIG deal for full time cruisers with AGM's is that you can charge them in 1/2 the engine/generator run time if you have a big enough charger. They pay for themselves with the fuel savings...AND...your time waiting each day for charging to be finished!

[motion30]

Originally Posted by S/V Illusion

You didn't indicate how large your house bank/banks is/are.
Why would you even consider connecting both chargers?
Do you have sufficient battery capacity to warrant use of two 55 amp chargers?

My house bank is 500amps of agm hence the 2 chargers

[CharlieJ]

I know I sound like a broken record...AGM batteries require temperature compensated charging. IOTA chargers do not offer this feature. What this means is that, as the temperature goes up, the chargers will provide too high a voltage to your AGMs. AGMs can accept a lot of charging current. They do not tolerate high voltage, however.

That being said, how is your generator currently wired? 120 VAC single phase or 120/240 VAC split phase? It sounds like you are wired split phase.

[motion30]

Charlie I understand your reasoning but sometimes compromises need to be made. We will see how this works out Anyway, yes I am wired split phase I have on side of the generator that is doing nothing

[camaraderie]

We did just fine cruising FT in the tropics without temp compensation on our 1000ah+ bank of AGM's with a 135amp Heart 3 stage charger. I don't think you have much to worry about motion30.

Charlie...where are you getting AGMS REQUIRE temp compensated charging from? Please point me to a quality battery mfr. that requires it. Not saying it is a bad idea...just have NEVER seen any such requirement.

[CharlieJ]

Cam-
Actually ALL lead acid batteries require temperature compensation during charging.
Here are a few examples:
Lifeline AGMs:
http://www.lifelinebatteries.com/manual.pdf Section 5.4, page 16
Northstar TPPL AGMs:
http://www.northstarbattery.com/SES-544-01.pdf Figure 2, page 13
Trojan Flooded:
Trojan Battery Company
Nigel Calder's "Boatowner's Mechanical and Electrical Manual; 3rd Edition"; Table 1-10 on page 33 shows gassing voltages as a function of temperature.

And it is not only ambient temperature that gives us problems. Large charging sources will cause heating of the electrolyte, liquid, AGM or gel which manifests itself in requiring less potential to drive the electro-chemical reaction. Put this system in a hot engine room and you are reducing the life of your batteries fairly dramatically. The three references that I cite above also have charts/graphs showing the loss of cycle life as a function of temperature >77F (25C)

So, here is the scenario: your battery bank is being charged with un-temperature compensated charging sources and ultimately does not provide the cycle life you expect. You approach the manufacturer with a warranty claim, how do you think you will fare?

Hope this clarifies.

[camaraderie]

OK...none of the above sources require temp compensated charging. That was my point. If they mention it, it is only as a good practice and then only do so in terms of ambient temperature adjustments.
And manufacturers warranties do NOT state anything about temp compensated charging so their warranties must be honored if the battery fails in the 90% plus non-coompensated installations out there. The warranties are thus either too SHORT to be affected by such concerns OR they do not believe their is much effect OR they simply build in the cost of keeping customers happy into their pricing. One thing for sure...you will NEVER be denied warranty coverage for not temp compensatiing.

For example...using your northstar charts...the ideal voltage for charging at 80 degrees vs. 100 degrees is 14.7 vs. 14.4. and for float 13.6 vs. 13.3.
I am not aware then of any non compensated 3 stage charger made by any of the common marine store brands which could damage your ultimate battery life from ANY ambient temperature up to 100 degrees.
(I assume one could achieve longer battery life by moving somewhere where average air temperatures were lower...or by installing a cooling system ...but as a practical matter...boaters need to charge their batteries regardless of the airtemp. )

Of course OVERCHARGING destroying a battery is a different matter altogether.

Note, I do NOT dispute that temp compensation is a good idea. I am only saying that it is no big deal if you follow installation guidelines (i.e. good ventilation and ambient temps) .... and it is certainly not a requirement for any mfr. or for their warranty to be honored.

[donradcliffe]

If you believe the marketing guys, temperature compensation is not that critical on AGM batteries. For some reason I can't cut and paste from Charley's references, but the Lifeline manual says:

"With Lifeline AGM batteries, tests have shown that increasing the charging voltage 1.0V above the recommended charging voltage results in only a 23% reduction in the cycle life."

Their recommended charging voltage ranges from 14.4V at 70 deg F to 13.87V at 120 deg F, or a range of only 0.5V. The conclusion is that if you set the charger for 14.4V and don't compensate for temperature, the reduction in battery lifetime will be less than 10%.

[CharlieJ]

Originally Posted by camaraderie

OK...none of the above sources require temp compensated charging. That was my point. If they mention it, it is only as a good practice and then only do so in terms of ambient temperature adjustments.

Cam- Regarding the use of the word "require" I think that we are arguing about how many angels can dance on the head of a pin .

When you purchase a piece of equipment, that piece of equipment usually comes with an installation/owner's/technical manual. That publication provides the installer and end user with instructions for installing, operating and maintaining the equipment. And, generally speaking, warranty claims are based on the proper installation, operation and maintenance of the equipment. Operate the equipment outside of the parameters spelled out in the documentation may very well negate a warranty claim.

Do the manufacturers that I cited "require" temperature compensated battery charging sources; I say yes. They provide tables, graphs and text to guide the installer and end user in how the product is expected to be installed, operated and maintained. If it wasn't an important factor, they would not include the temperature compensation information in their technical documents. And AGMs are more susceptible to high voltage charging then flooded batteries and not quite as susceptible as Gels.

As I have stated in other posts on AGMs, battery temperature is made up of two components: the ambient temperature of the area where the battery bank is installed and the temperature increase that is a result of the electrochemical reaction taking place during the charging process. One of the main virtues of AGMs, and especially TPPL AGMs, is that the charging rate can be as high as C (C is defined as the amp-hr capacity of a battery; thus, a 200 amp-hr battery can accept a 200 amp temperature compensated charging rate). These two damaging components can be mitigated, to a large extent, by using a temperature compensated charging source. (And there is the specter of thermal runaway that we can get into at a later time.)

Regarding your statement, "I am not aware then of any non compensated 3 stage charger made by any of the common marine store brands which could damage your ultimate battery life from ANY ambient temperature up to 100 degrees." here is an excerpt from the Xantrex TrueCharge 2 technical manual (the successor to the venerable TrueCharge 20+/40+ chargers):

Xantrex strongly recommends that you install the optional
Battery Temperature Sensor (BTS) to protect your battery
and improve charging accuracy. If no BTS is connected, the
charger defaults to the charging temperature settings (Cold,
Warm, or Hot).

And, again, it is not ambient temperature that is of concern. It is the temperature of the battery that will prematurely age it when exposed to excessive charging voltage.

Finally, AGMs are expensive and their care and feeding is more sophisticated then most people know about. They are sensitive to high charging voltage, which is a function of temperature, but they are also sensitive to under voltage. For instance; the charging profile for the TrueCharge2 battery charger is not nearly agressive enough for AGMs in general and TPPL AGMs in particular. The 25C absorption value is 14.3 VDC and the float voltage is 13.4 VDC. The Northstar TPPL AGMs, and others, require a nominal 14.7 VDC and 13.6 VDC respectively. Using the AGM profile on this particular charger will chronically undercharge the batteries which will ultimately lead to sulfation and premature failure.

In the early days of AGM initiation into the marine industry, we did not understand the affects of temperature and charging voltage. I have a very good friend that we cruised with in the Eastern Caribbean. He went through three sets of AGMs before we began to understand what was going on. Installed the fourth set and temperature compensated his charging sources and all was right with the world

Charlie, Out.

[btrayfors]

Flooded batteries and AGMs are not particularly sensitive to high voltages. In fact, the recommended Lifeline voltages at "normal" temps often exceed 14.3 VDC for a 12-volt battery (see Tables in the above-cited manuals by CharlieJ). By contrast, gelled batteries ARE very sensitive to high charging voltages.

Flooded batteries and AGMs are much more often damaged by UNDER CHARGING and TOO LOW charging voltages, than by high voltages. See Rick's excellent piece re: voltages and battery charging.

Further, the Iota chargers use PWM technology for charging. They are specifically designed so as not to cause overheating, due to the type of pulsing used and the intermittent character of the pulses.

That said, if an abnormal condition were to exist, it's a good idea for ANY battery to have a temp sensor. But, then...many of the current crop of temp sensors are faulty, themselves causing either undercharging or overcharging, and possibly very dangerous situations (where the actual battery temperature is much higher than what the sensor is reporting). How is the average boatowner to know?

Personally, I wouldn't hesitate to use Iota chargers with AGM batteries, and Iota engineers have confirmed to me (reported elsewhere) that they are fine with AGMs.

I think I'd spend time worrying about other things!

Bill