following good advice

System · December 2007

Hi Guys,
Following the good advice from others on this forum I have now aquired the services of an Onan generator 2cyl. 5.0KW 120V or 240V.1800rpm
I also have purchased two multi-stage battery chargers (12,8,2amp)
This is only for a one time use.. and not to be confused with a permanent solution for all my energy needs.
So, if I use both 12v chargers at the same time I might be able to charge two batteries banks at once? best case scenarion is (10) 12V batteries could be recharged at once.
Is this possible with the two (12,8,2 amp) battery chargers that I have purchased?
How many 12V@160 a/h deep cycle batteries could I recharge at once?.
Should I get (1) bigger charger instead of (2) smaller ones?
or will this work as a temporary emergency measure?
Thanks for your replies.
kevin

BB. · December 2007

Re: following good advice

Kevin,

One question I have for you... Is the generator going to be running anyways (for construction, lights, etc.) or will it only be for charging/maintaining your battery bank in storage (for now), or as a hybrid generator system (generator on when needed for heavy loads, and battery+inverter for off-peak loads)...

-Bill

System2 · December 2007

Re: following good advice

Hi Bill,
I'm in an emergency situation. The batteries are in a 7 month state of sitting with no recharge!
I need to get some juice into them and fast.....before winter sets in!!!
I am likely to visit these batteries 3 times during winter months.
During summer months my visits will be more frequent. I will be using the generator on weekends to run my tools and to build my cabin.

I have no use for these batteries ....they are just dead weight on the island but eventually I would like to add a windmill to automatically recharge these same batteries and elimate my need to recharge them with the Onan 2cyl.
What do you say Bill? Hybrid system?
It might take 2-3 years before I find and buy the right wind system

kevin

BB. · December 2007

Re: following good advice

Kevin,

The problem (that I see) is that the 12 amp battery charger when divided across (for example) two 12v strings of 2x5 series/parallel 160 AH batteries--that gives you 800AH per battery charger--12/800=1.5% charge rate--If you assume that your batteries have dropped from ~1%-15% per month... call it 7% for 7 months (0.93^7=60% SOC after 7 months).

To recharge 1/2 of your batteries with a 12 amp charger (1.5% charge rate):

40/1.5=27 hours

Are you willing (and able) to run your generator for 20-30 hours to recharge your batteries (and you probably would need at least twice the current to equalize them)?

Your 12 volt charger uses probably (12a*15v*1/80 eff=) 225 watts. Your generator should easily manage 10-15 times larger battery charger, and instead of taking a day or two to charge, you will now be down to 4-8 hours--quite a bit of savings in time and fuel (assuming that the generator below 25% capacity does not burn much less fuel because of engine and windage losses)...

If you can, it would be better if you could find/borrow/salvage a charger (or several in parallel) that can crank out 2-3kW to charge all of your batteries (wired into what ever bank voltage works).

Was not quite sure about your hybrid question/comment...

-Bill

Lefty Wright · December 2007

Re: following good advice

I hope you have better luck than I had when I tried to put some charge into my 220AH battery bank with my 10A/2A automotive charger.

The Batteries drew so much current that the charger overload relay kept tripping.

It was during a prolonged period of overcast skies and I wanted to stuff some energy into the batts but found that my 10A automotive charger couldn't do it.

quid_non · December 2007

Re: following good advice

That's a bummer Lefty - I was planning on doing the same thing myself. Anbody else have the same result or a explanation why the charger behaves this way?
Thanks
Wayne

crewzer · December 2007

Re: following good advice

The 10 A automotive charger is probably designed for charging an automotive battery that is similar in size to a Group 27 deep-cycle battery, or ~105 Ah. As the battery voltage increases, the charger’s output current decreases, and the temperature of some component inside the charger (i.e., a current limiting resistor) is kept in check.

However, using the 10 A automotive charger to charge a 220 Ah deep-cycle battery may be causing it to deliver at/near the full 10 A for a period longer than intended for its design. As a result, something in the charger (the previously mentioned resistor?) may be overheating and causing the charger to disconnect.

Automotive battery chargers are less than ideal for recharging deep-cycle batteries, but they may be better than nothing in a pinch. You might try cooling the charger with a small fan and to see if that helps.

HTH,
Jim / crewzer

Lefty Wright · December 2007

Re: following good advice

I don't know how much current a moderately discharged 220Ah bank would draw from a source like an automotive battery charger, but mine popped it's resettable overload breaker instantly.

I agree that using an automotive charger is better than nothing when you find yourself in the middle of a long dark spell. Has anyone ever heard of any rule of the thumb about battery size vs. charger ampacity using these things?

I do know that a 10 A charger doesn't make it for 220AH.

System2 · December 2007

Re: following good advice

Hi Bill and others,
I am currently in the same boat as Lefty!
I don't know the exact state of discharge of my batts until I get to island and
1) measure voltage across the terminals
2) take specific gravity of all the cells and
3) then what?
After I measure these two items.....then what? I forget? Do I compare to specs for Exide CA-9's ?
BTW: I have just upgraded to (2) 20,10,2 amp with 60amp engine start, multi stage battery chargers for wet cell batteries (2 of them).
Q: So, have I wasted my $127.50??
If the same thing happens to me as Lefty I will be chucking the bank, the charger, the hygrometer, the computer, the generator and NAWS right in the old ocean!!!:D
Will 20amp smart charger be enough?

Kevin

System2 · December 2007

Re: following good advice

Bill,
I am really new to this.
Most battery chargers that I see on the shelf (at least the 12V ones) come with an amp rating.
So, when you say 2-3KW would be ideal? I say great...how many amps is that?
I do have multi stage batt charger...so does that mean 20amps* 12V= 240Watts?
If I have two of them plugged in at the same time I will be drawing 500 watts of power from my brand spanking shiny new generator that puts out over 5.0KW(continuous)
Is that correct?
Am I close?
If I put 800a/h on charger "A" and another 800 a/h on charger "B" how many hour are we looking at with a 20amp 12V charger??
Or do I need to steal my friends 100amp auto charger? Its not multi stage.
Kevin

crewzer · December 2007

Re: following good advice

Has anyone ever heard of any rule of the thumb about battery size vs. charger ampacity using these things?

Trojan Battery recommends a charger current of ~10% to 13% of battery capacity for their flooded-cell deep-cycle batteries. See: http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/ChargerSelection.aspx

Xantrex makes a couple of models of their first-rate "TrueCharge" multi-stage 12 V deep-cycle battery charger. The model TC20+ is recommended for a battery bank in the 100 Ah to 400 AH range. Note that this model is passively cooled, and it must be installed in a vertical orientation to promote adequate cooling. It can overheat if installed horizontally. The TC40 is suggested for 12 V battery banks of 400 Ah and up; this one includes a cooling fan. These are very good but not inexpensive chargers. See: http://www.xantrex.com/web/id/69/p/1/pt/7/product.asp

Here's a link to other apparently quite good chargers (when used with the IQ4 option): http://store.solar-electric.com/bach1.html

HTH,
Jim / crewzer

mike95490 · December 2007

Re: following good advice

If you have to buy a new charger, consider placing your batteries in SERIES, and charge 4 at at time @ 48V.

Or 5 strings of 2 batteries, at 24V. Any chargers out there with adjustable 12 - 48V outputs? It would be a better use of generator time. [ charge each string individually the first time, so you don't have mismatched strings charging and discharging each other
22V
25V
22V
24V You can't put that in parallel, charge them all up to the same voltage, before hooking in parallel ]

BB. · December 2007

Re: following good advice

Yes Kevin, you are starting to see the math...

Power (in Watts) = Voltage * Amps

So, if you know two of the three, a little algebra gives you the third.

And, once you know the Watts, you need time (hours) to get how much total power you will need...

You have a nice large generator and the 12 amp battery charger is just a little load. Generators are generally not very efficient with light loads--and batteries with small charger take forever to charge (and if the charger is too small, the battery cannot equalize).

-Bill

System2 · December 2007

Re: following good advice

Ok Mike,
I see.... thats good advice.
I need to see that all the batteries have exactly the same Voltage before I put them in paralell.
BTW: I have (2) 20amp chargers @ 12V

OK, so I get that 5.0KW is 5,000 watts and I am only using 500watts or 10%.
Hmmm....so I need to find something else to do whilst I am charging. Like what? I have no appliances and its too cold to start building the cabin yet.

BTW: My 3 stage charger says it puts out steady DC voltage? instead of pulsated DC voltage? Is that just sales hype? or what?

If my friend has a heavy duty 100amp auto charger.....and I have just the (2)20,10,2amp (12V) chargers and the batteries might be discharged 50% or more. Would you suggest higher amps to start? Then finish charging with 20,10,2amp.....or the other way around?

Remember this is just a one time event until I get set up in the summer with proper facilities (ie; batt shack, charger, controller, inverter etc)
The reason I am asking all this is because when I get off grid...I will be off-line and to be "off base" is not good either........it may be more useful to get good advice 1st than look for 1st Aid in the bush!

Kevin

mike95490 · December 2007

Re: following good advice

envelopes2007 wrote: »

If my friend has a heavy duty 100amp auto charger.....and I have just the (2)20,10,2amp (12V) chargers and the batteries might be discharged 50% or more. Would you suggest higher amps to start? Then finish charging with 20,10,2amp.....or the other way around?

Remember this is just a one time event until I get set up in the summer with proper facilities

I'd charge them on the 100A charger, (well, you can't put just one battery on, 100 A will cook it. If these are the 160A batteries you spoke of earlier, flooded cell batteries, sustained charge current should only be C/10 (capacity / 10 ) or 16 A per battery.

HOWEVER, unless your friends 100A charger is set for deepcycle batteries, it will only charge per the starting battery profile, and shut down too early. It may put 20 or 30 amps in for a couple of minutes, but it will fold back fairly quickly. It will likely fade before you can cook your batteries too badly anyway. You really need a 24 or 48V charger, to charge that many batteries, that's way too many cells to run in parallel. If you MUST use automotive chargers, I like the Vector/B&D series, that have a deep cycle setting. I've got a VEC1093DBD in the $110 price range online

System2 · December 2007

Re: following good advice

Mike,
I plan to charge only (4) 6V batteries with (1) charger Ie the batts will be in a (2)12V@320a/h array.
I have two chargers on hand plus my friends 100amp.
I am going this weekend (in the cold rain and snow) so its a merely a one time maintenance charge that I am hoping for.
Just taking all the 12V chargers I can rustle up ...100amp into 320a/h array?

mike95490 · December 2007

Re: following good advice

That should work.
Using the 100A charger, watch the amps carefully for the first 10 minutes, record the initial amp output from the charger, and then check every 5 minutes. If after 10 minutes, the amps have not decreased by 25%, throttle the charger back to about 30 amps max output, run that way for a half hour, then see how many amps it's drawing from the charger.

[ Before charging, top off the cells with distilled water. ] EDIT

Yikes ! I meant this in the spirit that the cells need to have attention paid to them, regarding water level, and that the plates stay at least covered, not full to the brim.

crewzer · December 2007

Re: following good advice

Before charging, top off the cells with distilled water.

I recommend against that practice, and so do Trojan Battery and Bill Darden, among others.

See: http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/Watering.aspx
and: http://jgdarden.com/batteryfaq/carfaq3.htm

I believe the fundamental concern is that internal battery plates and electrolyte expand as they are heated during the charging process, which is only ~80% efficient. If the cells are completely full, the electrolyte could be forced out. This would cause a caustic mess on and around the battery(ies), and it would reduce the acid content of the remaining electrolyte, which in turn would impair battery performance.

The best watering guidance I’ve seen is to check each cell before charging the battery(ies) and verify that the internal plates are just covered with electrolyte. If necessary, add just enough distilled water to cover the plates. Once the charging process is complete and the batteries have cooled, then check the electrolyte levels again and top off each cell per the manufacturer’s instructions.

HTH,
Jim /crewzer

mike95490 · December 2007

Re: following good advice

thanks crewzer, good catch. I was thinking batteries not attended to, may be low in water.

System2 · December 2007

Re: following good advice

OK.
I have listened to the advice here and visited the site at Trojan and have laminated myself a copy of a deepcycle maintenance chart and a SOC sheet.
I have waterproof notepaper and a clipboard.
I have a battery tester.
I have de-ionized water in a plastic jug and a hygrometer and a syringe (just in case) and a rubber apron,
So, anything else before I venture forth?
There is only 9 hours daylight each 24 hr day right now ...so, thats when my charging period will end (end of subject)!
8 batteries per day for 3 days.....plus one day to build a batt shack and put an outside door on it and then maybe thats it!
....see you in '08.
Kevin

BB. · December 2007

Re: following good advice

You have 20 somewhat large batteries... You may need way more than a gallon of deionized water... If this is a one way trip (no local stores), then I would probably bring 4-5 gallons of water--at least it will keep for when you need it next summer...

Check all batteries first and add enough to cover the plates so that you don't use all of the water up...

-Bill

niel · December 2007

Re: following good advice

in storing that water with nobody there means that water is quite apt to freeze so please make some provision to prevent its loss or spillage in splitting open its container.

System2 · December 2007

Re: following good advice

hi Neil and Bill,
I am considering purchasing a XANTREX FREEDOM COMBI 12v 2500w INVERTER CHARGER with a LINK 1000.
It is available here in Canada (locally).
My expected loads are just power tools, lights and music.
limitations?
benefits?
good choice?
comments?
Kevin

BB. · December 2007

Re: following good advice

I do not have direct experience with the hardware--so I can't comment on features/usage from my view...

But, I will suggest that the Xantrex is a Modified Square Wave inverter. Generally, if you are building an off-grid system for your home, I would suggest that you would be happier spending the money for a true sine wave inverter.

Mod Sq wave inverters are not good with motors (higher losses) and possible damage to appliances sensitive to sq waves just make wiring a home with one for long term use a bit dicey...

The problem is that the Mod Sq wave inverter will work OK with 90% of your appliances/electronics--and it will be up to you to figure which 10% do not (overheating, failures, etc.).

The downside with pure sine wave inverters--they are much more expensive. Read the Wind-Sun inverter FAQ here for a nice overview of inverters...

One other thing to look for... The "high end" inverters (Outback, Xantrex and others) can have a very neat function. With the generator running, the AC power is passed directly through to the load(s) (less losses), and the inverter/charger can monitor the total current flow. So, say you have a 2kW generator and set the inverter/charger to 12 amp load (approx 1.44kW)... Plug in a 100 watt load, then 1.34kW is available to charge your battery bank. Plug in a 1,000 watt load and 0.44kW is available for charging your batteries...

For your 5kW unit--you may not need this feature unless you use a lot of electricity at times (tools, well pump, electric heat--shutter...).

A very nice feature if you are using a small generator... You will probably have to plow through the manuals and/or ask somebody directly to recommend an inverter with this feature (if you are interested).

-Bill

niel · December 2007

Re: following good advice

i agree with bill that the sine wave inverter is the better way to go for many reasons. it will cost you more for it, though. you should read up on the inverters to get an idea of their capabilities and requirements while also figuring what you will need from an inverter maximumly at any one time. the inverter you choose must be able to handle your maximum draw on a continuous basis and having extra capability does not hurt for possible future expansions on your power needs.
i do have to say that some items can be run via dc rather than the power lost in inverting to ac. lights such as dc cfls are great in reducing power needs and power consumed. if you can use smaller 12vdc car stereos (not those 500w mobile boom boxes) you can save power that way too. audiophiles will obviously find most of the smaller car stereos unacceptable, but i suppose with some research a bigger and better car stereo could be used more efficiently than many home stereo systems. it all depends on what you want.

following good advice

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