Author Topic: can anyone help! (Read 5289 times)

davidbrown80 · « **on:** January 26, 2008, 09:35:21 PM »

hi

I am new here! I have just installed a 3kw wind turbine which is connected to a battery bank consisting of : 20 x 12v 110 amp hr batteries this in turn is connected to a 5kw inverter to supply my home. i also have a 5kw diesel genset for backup. i have no other source of electricity! what i would like to know is how i can charge my batteries' ( in case of low/no wind)from another source other than my wind turbine IE my genset.

i have looked but can't find a 240v ac charger that will charge my 240v dc battery bank. my battery bank is 20x12v 110amp hr batteries connected in series thus producing the 240v dc to supply my inverter. does any one know how i can do this . is it possible to connect a few normal car chargers, for instance ten chargers each charging two batteries? whithout it causing a short curcuit with the series wiring??

or any other way . my inverter does not supply a charging current for this purpose. and my turbine charge controller does not have an ac inlet either. anyone with any informtaion would be appreciated curcuit diagrams or any other ideas wecome.

many thanks for any help.

Duplicate postings removed. Resectioned.

chainsaw · « **Reply #1 on:** January 26, 2008, 03:19:50 PM »

I would be curious to what type of inverter you have that operates on 240 VDC.

SparWeb · « **Reply #2 on:** January 26, 2008, 06:28:30 PM »

If you are totally isolated from a supply of grid electricity, then you probably cannot do better than the diesel generator that can provide the 240V (and higher) that you need to charge the battery. Wind/Diesel is a fairly common combination for remote areas. Are you now having trouble obtaining diesel for the generator?

Cobbling together a string of car alternators is like building yet another generator system, and what you're suggesting sounds both complicated and risky. Even if you do manage to mate 10 car chargers together, what will be the prime mover? Another diesel engine? Sounds like reinventing the wheel...

Just trying to get a handle on the problem that is causing you to ask about alternatives.

Why do you have a string of batteries wired in series to give 240VDC? Why not 48VDC, which would give you many more choices of inverter that can be bought "off the shelf"?

jonas302 · « **Reply #3 on:** January 26, 2008, 07:36:02 PM »

I don't know about a plug in charger but maybe build a high voltage alt to couple with a diesel engine for batt charging

richhagen · « **Reply #4 on:** January 26, 2008, 09:57:26 PM »

I am not certain, but I am assuming that your problem is that you have ac output from your generator to power your circuits, but no idea how to charge your batteries from that source. 240VDC is a high voltage dc battery bank, most of the folks I know have 48V or less, and even the local utility here uses 120VDC nominal for its substation back up. Do not underestimate the shock hazard of a high voltage battery bank.

If I am correct in my guess of what your problem is, and your generator outputs 110AC, then you still have several options. There are isolated chargers that will do what you propose, in charging parts of the string of batteries. I have a 72V electric vehicle that is charged that way. There may be limits on the isolation, so you may want to check with the manufacturer of the charger that you wish to use. I have 'Dual Pro' brand chargers on my electric vehicle. They work off of 110AC and manage individual strings of 12VDC in the bank. They are largely marketed for marine usage.

Another option would be to get a charger or converter that would be able to charge the 240V string together from the 110V source. The substations mentioned above use chargers made by a French company, 'Loraine' or 'Lorentz' although they were supplied from 480VAC. I have no Idea whether they or other manufacturers make chargers for a 240VDC bank, but I would bet they are big bucks if they do. While there are some people on this site who could no doubt make an efficient high power charger for an application such as this, it is not something that I would try myself, or recommend to someone without a reasonable amount of electronics experience.

Another Idea, if you can add a belt and bracket to your generator would be to use a PM DC motor as a generator to dump current into the battery bank. You would then drive both the AC generator head, and a DC charging head with the motor, just add a disconnect to the battery charging output to disconnect it when the battery is full. I have seen this technique applied to lower voltage battery banks, and if one could find a suitable motor there is no reason it would not work on a 240V bank. Rich

Flux · « **Reply #5 on:** January 27, 2008, 01:36:13 AM »

Yes you could use individual battery chargers but from the look of some that I have repaired I would not be too happy applying 240v to earth on the low voltage end.

You would be far better off finding an isolating transformer, feeding it to a rectifier and including a small ballast resistor to keep current under control. 240 rms ac has a peak voltage that is just high enough to fully charge a 240 v battery but with the high reactance of most alternators the final stage might be very slow. Having a few taps on the transformer may be a good idea.

Even better to use a higher voltage and add a choke in the dc positive line between the rectifier and battery. You are into some pretty serious stuff, just don't under estimate what you are dealing with. Fuse any potential battery charger with adequate HRC fuses that can clear a 240v dc fault. Use 800v or over bridge rectifiers.

Flux

ghurd · « **Reply #6 on:** January 27, 2008, 02:10:54 AM »

Correct me if I am wrong...

This sounds like an idea more than something that actually exists?

Might consider a transformer to get the windmill voltage to 48V.

And a 48V inveter.

And next year, when the 110AH battery bank is used up, maybe L16HCs or better.

It would be crazy to put a 240V DC supply large enough to charge that battery bank out in the open.

People would be killed.

Maybe I can make U235 out of cigarette butts and french fries, but I wouldn't put it on the internet.

G-

thyristor · « **Reply #7 on:** January 27, 2008, 07:27:21 AM »

Apart from the necessary safety precautions involved with 240V, your inverter will be very efficient at that high voltage, also a high voltage means a low current, which in turn means connecting and distribution cables that does not approach the dimensions of welding cables.

The type of charger will most certainly be the isolation type, i.e. with a transformer containing separate primary and secondary windings. All lead-acid batteries need to be kept in the charged state at all times or should be recharged soon after a discharge. The deep cycle types are more tolerant in this respect and should be used in an installation like yours.

If your diesel gen-set is 3 phase you'll require a charger with a 3-phase transformer.

If it is a single phase unit, a single phase charger is required. It is possible to custom build any of the former and it should preferably be a regulated type to prevent over charging of the battery.

dastardlydan · « **Reply #8 on:** January 27, 2008, 09:03:41 AM »

They have chargers for electric

car that will go to the voltage you want.

Check the web for EV stuff

you will find it.

davidbrown80 · « **Reply #9 on:** January 27, 2008, 01:20:00 PM »

hi

well this system does exsist. i bought it recently and are now in the process of installing it. the system as a 3kw wind turbine with a rated power of : 3,000 watts

with a rated voltage of :240vdc and is recommended to be married with 20x12v 110AH deep cycle batteries which is what i have. and is rated to produce 8,672.4 units(KW Hours) per annum ,the turbine is a pioneer plus OG specified for medium to high consumption and has a built in controller and battery charger. the problem i have is that i am concerned that in the case of low or no wind ill have no way of charging my battery bank and with no way of inputing a supply from my genset for this purpose. since my house will be supplied from the inverter which is a 5kw pure sine wave and boasts. a wide input votage rage from 90v-280v . four steps AVR and a charging current of:500W up to 15 A 1kw up to 25 A . i realy need a way to keep the bank charged when there is no charging from the wind turbine. i am aware of some of the problems of a high voltage system like for instance connecting the batteries togther you cant just grab the nuts to screw down the contacts as the volatage increases the more batteries that are connected up to the final 240v dc which would more than twang a bit if you had a shock off them.

thanks for all who have replied.

terry5732 · « **Reply #10 on:** January 27, 2008, 03:36:55 PM »

Your cheapest bet would be to build your own charger but you would need a little electrical knowledge. You merely need to rectify your generators AC to DC. These would be some fair size rectifiers. You could get fancy and add a charge controller or smoothing caps but these aren't a neccessity. Plenty of opportunity for a bad accident with a bank of that size. I do like the advantages of the voltage though.

fcfcfc · « **Reply #11 on:** January 27, 2008, 03:40:12 PM »

Hi: All the other factors aside, you had better have every connection insulated on that 240 battery bank like it was 440VAC. You could turn yourself into a lump of charcoal with that voltage and large amperage available!!

Safety first!!!!

fungus · « **Reply #12 on:** January 27, 2008, 03:57:29 PM »

If I was going to have a high voltage bank (and I probably will some time in the future..) , for servicing I'd put isolating switches on every 4th battery, you'd turn off all the switches for servicing splitting it up into 48v segments which are just below the danger zone.

jacobs · « **Reply #13 on:** January 27, 2008, 08:16:19 PM »

I have a 144vdc system and I charge it with an older gasoline generator. In fact I use two different Kohler generators. One of them is a 1930's 4 cylinder water cooled 1500 watt, 1000 rpm, 110vdc generator. I installed an additional spring on the throttle to allow it to run at a slightly higher rpm to boost the voltage for battery charging. The other generator is a portable 3600 rpm 1980's model. This generator I again installed a spring on the throttle but this time to slow the rpm's down to 1800 rpm and I charge off the 240vac output through a bridge rectifier for charging my batteries. Bridge rectifiers for this application cost about $4.00 from Mouser Electronics.

If you can find a small 440 volt generator, you could rectify that output to charge your 220 volt batteries similar to the way I did or if you can find a 220vdc generator, that will work also.

I've been using a high voltage system for 27 years and wouldn't consider using anything else. It's much more efficient with less losses. Breakers, switches, and wire are much more economical and easier to install. If you are aware of the hazzards of high voltage and don't get careless when servicing, you'll laugh at low voltage systems. Just be careful!

spinningmagnets · « **Reply #14 on:** January 27, 2008, 08:56:03 PM »

Since you need to make a solid metal-to-metal connection between the cable clamps and the battery posts, perhaps you could configure your pack in 5 sets of 48 volts. Then, in-between the sub-sets you can have 4 sets of 240V-rated switches to make the final connection. I'm not experienced with this, but maybe a useful idea...

I dropped a steel wrench onto a high-amp 24V set (2 X 12V) that was used to start a bulldozer. Melted the lead post and damaged the battery. I've been told that even using a wrench with one hand (so current won't cross your heart), if you get high volts into your hand, the muscles will contract and you can't let go. (don't know if it's true...but being too cautious is free)

jacobs · « **Reply #15 on:** January 27, 2008, 09:09:26 PM »

I've been zapped by high voltage dc many times and I've never had muscles contract. The first time was about 45 years ago when I got zapped by the high voltage anode on a TV picture tube.....that was roughly 15,000 volts! That's one experience I'll never forget.

Any battery voltage can be dangerous. Someone needs to make plastic wrenches for us.

spinningmagnets · « **Reply #16 on:** January 27, 2008, 09:17:17 PM »

OOPS! Sorry Fungus,

If you do set up your pack to allow isolation into 5 X 48V sets (also isolated from the other parts), perhaps it will be easier to find a couple of the 120VAC-to-48VDC chargers (I'm assuming your diesel-gen has a couple of 120VAC outlets).

If you do go that route, and then install a better system later, you shouldn't have any problem selling the chargers for a reasonable price.

davidbrown80 · « **Reply #17 on:** January 28, 2008, 11:26:20 AM »

hi

do you have any circuit diagrams for such a charger?

Thks . Dave

davidbrown80 · « **Reply #18 on:** January 28, 2008, 11:28:12 AM »

hi what rating would these isolating switches have to be?

dave

jonas302 · « **Reply #19 on:** January 28, 2008, 04:53:26 PM »

snap on makes plastic wrenches 65 dollars for 9/16 x 5/8 ratcheting box end rated 1500 vdc part# crb1824 wouldn't be a bad investment on any system its easy to melt a wrench with just on batt

richhagen · « **Reply #20 on:** January 29, 2008, 01:36:47 AM »

Generally, there ratings should exceed the banks maximum voltage with a safety margin, and should be rated for more current than the battery banks fusing again with a bit of a margin. That said, I might just look at using some Anderson disconnects if rated for that voltage. Rich

thyristor · « **Reply #21 on:** January 29, 2008, 11:42:25 AM »

Another simpler and cheaper way to make a charger, is to build a small triac phase controller with manual voltage control which you can then adjust until your ammeter reads 11A (C/10) or 22A (C/5) where C=amp-hour capacity of the bank which in this case remains the same as for any one of the batteries, namely 110Ah (series connection).

You do get a TRIAC rated at 800V (or even 600V) and 40 Amps. This is called BTA 40-800 and comes in a handy TO-3 pakage that can be bolted onto a heatsink.The metal part of this is also conveniently isolated and does not need any insulating washers, just a thin smear of heatsink compound (Silicone grease).

O.K. you will first have to get hold of the forementioned isolating transformer with a 240V AC output. This output is then passed through the TRIAC (WHICH IS CONTROLLED BY MEANS OF A SMALL PHASE CONTROL CIRCUIT). The phase-controlled output is then fed into a bridge rectifier, ammeter and onto the battery bank. No taps are required on the transformer, as this controller has a very wide range.

(Use fuses or DC rated circuit breakers to safeguard everything as was mentioned earlier).

The only drawback is the fact that it is not an "automatic" charger, but otherwise, it works quite well as long as you keep an eye on it. I recently built one for an automobile battery supplier (November 2007) and so far everything is still O.K.

When you do work on the batteries, just "keep one hand behind your back", so to speak! If none of the positive or negative is connected to ground, then there will not be a shock hazard if you should touch any of the terminals, but don't become too tame! Always be aware what you're busy with when high voltage is present.

jacobs · « **Reply #22 on:** January 29, 2008, 08:56:48 PM »

Interesting....Here's a link to it http://buy1.snapon.com/catalog/item.asp?store=snapon-store&item_ID=68015&group_ID=17470

That sure would be nice to have but for that much money I think I'll just continue to be careful. I melted down a wrench about 20 years ago on a battery...now I'm much more careful when servicing them.

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Author Topic: can anyone help! (Read 5289 times)