Which Battery Charger?

[Meck]

Hello again,

I'm hopeful that some day I will be able to contribute as much a I receive from this forum I'll keep working on it!

So, I'm shopping for battery chargers (must be 220v input), I've got over 900 amp hours with four Trojan L16h Batteries for the house bank and a Kohler 6.5kw genset. You all recommended 150 amps of charge. Here is what I have come up with:

Iota: 3 55amp units = 165amps for $648
Newmar 2 80amp units = 160amps for $2000
Sterling 3 60amp units = 180amps for $1350
Sterling 3 50amp units = 150amps for $1150
Victron 3 50amp units = 150amps for $1150
Victron 3 60amp units = 180amps for $1500
Victron 2 80amp units = 160amps for $1200

I am tempted to go with the least expensive option, but always aware of the wise quote "if you don't have the money or time to do it right the first time.."

I would really like some feedback on these options, I'm a real greenhorn when it comes this kind of stuff.

Best Regards,
Meck

[onestepcsy37]

i'm also looking for a new onboard charger. so far i've heard some very good reports on the iota. it seems that price is not always the best indicator or reliability.

[btrayfors]

The Iotas are certainly good chargers and they can be paralleled, but I believe they are 120VAC input only, not 240VAC which you say you need.

I think I'd opt for the Sterling 60A model....an excellent charger, extremely versatile, worldwide power input, etc., etc. And, I'd probably go with just two of them. That would give you a true 120A capacity and would be a good enough match for the four L16s.

I assume that you also have a healthy sized alternator on the engine(s) and perhaps solar panels and/or wind generator?

Bill

[deckofficer]

This is where I can learn something also, like why is 150 amp charge recommended? Also L16s are 435 a-hr at the commonly used 20 hour rate, so instead of "over 900 a-hr", more like 870 a-hr. Since lead acid doesn't have near the charge acceptance as LiFePO4, and for flooded lead acid the accepted charge rate is 0.1C, then why 150 a-hr charger instead of a 80 a-hr charger? My guess is with multiple chargers combined with the low charge acceptance of LA, each charger will see the other's voltage and taper. My uneducated vote would be for a single 80 a-hr charger.

Without using HydroCaps, and charging at 0.2C, who would want to add that much more distilled water to the cells each year?

[colemj]

Originally Posted by btrayfors

The Iotas are certainly good chargers and they can be paralleled, but I believe they are 120VAC input only, not 240VAC which you say you need.

Iota make both 240V AC and 24V DC versions of their chargers.

Mark

[btrayfors]

Originally Posted by deckofficer

This is where I can learn something also, like why is 150 amp charge recommended? Also L16s are 435 a-hr at the commonly used 20 hour rate, so instead of "over 900 a-hr", more like 870 a-hr. Since lead acid doesn't have near the charge acceptance as LiFePO4, and for flooded lead acid the accepted charge rate is 0.1C, then why 150 a-hr charger instead of a 80 a-hr charger? My guess is with multiple chargers combined with the low charge acceptance of LA, each charger will see the other's voltage and taper. My uneducated vote would be for a single 80 a-hr charger.

Bob,

Flooded lead-acid batteries can take 20-25% of their rated 20-hour capacity (C) during the bulk phase. Depending on the state of charge (SOC), the construction details of the batteries, their condition, and the ambient temperature, this amount of current tapers in awhile to something less than this.

The principal reason for using a relatively large capacity charging source is to economize by reducing the time needed to recharge the batteries using the engine or an onboard generator. Charging via these mechanical devices is VERY expensive, as Nigel Calder has documented and lectured about repeatedly.

However, the fact is that most boats out there have undersized charging capacity, many of them being woefully undersized.

I often hear things like, "Will a 10-amp charger be OK to use with my 1,000AH house battery bank? I'll be at dockside most of the time."

Well, yes, OK. Ten amps is enough for a boat plugged in most of the time. But it's ridiculously undersized for a cruising boat.

Bill

[btrayfors]

Originally Posted by colemj

Iota make both 240V AC and 24V DC versions of their chargers.

Mark

Yes, Mark, thanks for that.

Apparently they now do have 240VAC input chargers. And, they have 12, 24, 36, and 48VDC output chargers as well (nice to know for our Hatteras clients who have 36VDC systems for the most part).

See, e.g., http://www.solar-electric.com/bach1.html

Thanks again,

Bill

[deckofficer]

Now that Bill is onboard on this thread, I know I'll learn something.

Bill, during my time with EVs, I have found that my large charger quickly tapered when charging my flooded LA banks. This taper was less with my AGM LA, and when I finally upgraded to LiFePO4, no taper till the end.

For off grid homes that I've installed power systems, I've used chargers that were larger than the 0.1C of the bank to shorten gen set run time, but found increased water loss of cells till I started using the HydroCaps. This was many years ago, before lithium and AGM was new. The last home I did, still before lithium, I had good service from 700 a-hr 2 volt AGM cells over the tried and true L16s, plus I could carry the 2 volt cells, unlike the 125 lb L16.

[btrayfors]

Originally Posted by deckofficer

Now that Bill is onboard on this thread, I know I'll learn something.

Bill, during my time with EVs, I have found that my large charger quickly tapered when charging my flooded LA banks. This taper was less with my AGM LA, and when I finally upgraded to LiFePO4, no taper till the end.

For off grid homes that I've installed power systems, I've used chargers that were larger than the 0.1C of the bank to shorten gen set run time, but found increased water loss of cells till I started using the HydroCaps. This was many years ago, before lithium and AGM was new. The last home I did, still before lithium, I had good service from 700 a-hr 2 volt AGM cells over the tried and true L16s, plus I could carry the 2 volt cells, unlike the 125 lb L16.

Bob,

Thanks for that info. This is a good opportunity for me to learn, too, because I have absolutely no experience with LiFEPO4 batteries. Most of my experience and research has been with flooded lead-acid batteries and with AGM lead-acid batteries.

I've learned that it's a very good idea to use either HydroCaps or WaterMiser caps. All 10 of my flooded golf-cart batteries have WaterMiser caps, and they really do make a difference. And, you don't have to remove them during equalization as you do with HydroCaps.

As you know, the level of charge acceptance is a function of several things:

- the battery itself (SOC, its condition, construction materials, etc.)
- the ambient temperature
- the ampere capacity of the battery charging source
- the size and condition of the interconnected cables and connectors
- the output waveform of the charging current ... continuous, pulsing, etc.
- the output voltage of the charging source

It can be said that, in general, at any given output voltage from the charging source, the charging amperage will be determined by the other five factors. But, mostly by the battery itself.

If the battery under charge is taking 10 amps @ 14.4VDC, it will take 10 amps @ 14.4VDC no matter the size of the charger.

In other words, if the battery takes 10 amps with a 40A charger, it will still take 10A with a 400A charger, so long as the voltage is limited to 14.4VDC.

If you increase the voltage to 14.8VDC, the battery will take more amperage.

If you decrease the voltage to 13.6VDC, the battery will take less amperage.

And, as we all know by now, as the SOC of the battery increases, its charge acceptance decreases. At high levels of SOC, the capacity to accept charging amps is greatly diminished.

AGMs can accept a tremendous amount of charging current, as much as 1.2 times their rated 20-hr capacity when only 50% discharged. That is, a 100AH AGM which is 50% discharged can take 120 amps initially. And, there's evidence from the battery manufacturers that this is a good thing, i.e., that charging at these high rates extends the life of the battery.

I've written about this and posted several graphics elsewhere showing some of the results of AGM testing.

Still, very few boats with AGMs have anywhere near enough charging capacity to take advantage of their charge acceptance rates, and for many cruisers AGMs are probably not a good choice.

Bill

[deckofficer]

For my hot rod electric scooter I ran (4) Odyssey PC 680's in series for 48 volts, 16 a-hr and because of what you mentioned above, charging was fast with a simple golf cart charger running 17 amps. Could recharge in less than 1 hour.

So Bill, you recommend for the OP 120 amps of charge (and WaterMiser caps) for his series/parallel bank of L16s, but if he was using (6) 700 a-hr 2 volt AGMs in a single series string you would load his gen set to 80%, so about 350 amps?

[btrayfors]

Originally Posted by deckofficer

For my hot rod electric scooter I ran (4) Odyssey PC 680's in series for 48 volts, 16 a-hr and because of what you mentioned above, charging was fast with a simple golf cart charger running 20 amps. Could recharge in less than 1 hour.

So Bill, you recommend for the OP 120 amps of charge (and WaterMiser caps) for his series/parallel bank of L16s, but if he was using (6) 700 a-hr 2 volt AGMs in a single series string you would load his gen set to 80%, so about 350 amps?

Ha! Well, it wouldn't hurt but it would be a challenge to come up with a battery charger solution which would reliably generate 350A. On one of the Hatteras's here a fellow marine electrician installed four Iota 90A chargers for a total of 360A charging current. But, unfortunately, they've had a good old time trying to keep that running OK, and have "blown" a couple of chargers.

Thing is, it's all about charging efficiency and cost. AGMs can take a lot of charging current, yes, but it's difficult with a very large bank to provide that charging current without installing a high-capacity alternator setup on the main engines or finding high-capacity battery chargers.

And, while AGMs can accept high charging currents, they need to be fully charged frequently else their life is shortened. Flooded and gelled batteries, though also lead-acid, tend to be a bit more forgiving in this respect.

I'd say that on a typical mid-sized cruising sailboat...say under 50 feet or so....if you choose to install AGMs then you would be well advised to upgrade your onboard charging capacity through the use of high-capacity alternator(s), external regulator(s), onboard generator (AC or DC), large capacity smart battery charger, and plenty of solar and/or wind generator capacity to make sure those AGMs get a really FULL charge without having to run the engine or generator for 8 hours.

Otherwise, just go the flooded or gelled battery route...at least until some of the emerging technologies really come of age.

FWIW,

Bill

[pbiJim]

Originally Posted by btrayfors

Bob,

Flooded lead-acid batteries can take 20-25% of their rated 20-hour capacity (C) during the bulk phase.

I see a lot of people on this board quoting numbers like that. The numbers often come from people who seem to have a good deal of real life experience. I also see that some manufacturers, like these guys - State of Charge & Charging - Flooded Lead Acid Batteries : Technical Support Desk, claim that the maximum bulk charge rate should only be 10% of the 20 amp hour rate.

Contradictory information like that leaves me wondering.

Perhaps it varies with the brand of the battery???

[btrayfors]

Sizing a Battery Bank (Gel,AGM, or flooded)

[deckofficer]

Well Bill, I've had some wild ideas in the past that you have calmly showed me my miscalculations, got another for you.

I have been playing and running all kinds of load tests on my LiFePO4 cells, that I feel confident (until you show me otherwise) this type of battery will allow me my fully electric galley and running A/C without the constant drone of a generator. 36 kwhr capacity lithium bank, 4400 watt output 48VDC input inverter, and a 20 kw DC gen set for charging. Worst case scenario, Mexico in the summer, A/C running almost 24 hours per day at 75% cycle on time, so that would work out to a daily gen set run time of a little over one hour. Not bad in hot weather to have constant A/C comfort for such a short noisy gen set run time. Solar to cover hotel loads w/o A/C.

[pbiJim]

Originally Posted by btrayfors

Sizing a Battery Bank (Gel,AGM, or flooded)

Thank you for that reference, but that still leaves me with contradictory information from two sources, each of which would seem to be trustworthy.

I'm still left wondering:
Does it vary by brand?
Is the information from Rolls a bunch of Hooey?
Is the generally-accepted standard-practice flawed?