Portable Battery Charger

[vdubnut62]

Way to go! Looks like the little dude is cooking right along! Were some of those wires glowing, or was it just a trick of the light?
Ron

[Geno]

The heater wire was the best load I could think of to rig up. I kept shortening each piece till they got bright orange. I don't know how many watts they draw but there is only a slight change in engine note when I hook them up. The 600 watts of lights made a more noticeable change in engine note.

Thanks, Geno

[biobill]

Good to see and hear it running Geno.  Funny how these hot screaming deals always get a little more expensive in the long run, huh. Still, a diesel battery charger for around $500 ain't too shabby.   Bill

[Geno]

I began the mods to the alternator to try and get it to charge 12-48 vdc battery banks. The rectifier is removed and the regulator is disconnected. I have a "router speed control" thing on a shelf somewhere that will hopefully act as a rheostat to control the field. Off my shelf is good if I can get away with it. I may even begin to test it all out this weekend.

Edit: The outside posts do have insulators under them.

Thanks, Geno

[Geno]

I got to do some more testing last night. I removed the stock rectifier and regulator and put in this variac. When I raise field voltage above 2 volts it begins to put an increasing load on the engine even though there is no external load on the alternator. The alternator is acting as a brake. I'm obviously putting too much current to the field but what is this effect called? If there were a load on the alternator would this brake effect stop?

I then hooked up this rectifier to the alternator. I can raise field voltage till I get ~30 vdc coming off the rec and then the engine begins to load. I raised it up to ~60 vdc and the engine began to smoke a bit so I backed off. I expected the diodes to avalanche but the engine ran OK. I didn't leave it there long, it can't be good for the alternator. Do diodes go into avalanche gradually or is there a sudden hit?

I then put a resistance wire on the rectifier output but didn't go past 24 vdc. It should have been about 1000 watts. It was glowing brightly and there was some load on the engine. After 2 hours the alternator was still cool, the rectifier was hot and the engine was running well. The variac was drawing about 25 watts.

My next test will be an attempt will be to raise voltage to 65 vdc rectifier output with a 3.5 ohm resistance wire hooked up to it. That should give me about a 1200 watt load.

Thanks, Geno

[mobile_bob]

Geno:

my  bet is the rectifier is made up with diodes that are meant for 60hz and probably not much more

the 16 pole machine you have is probably running at over 500hz, and the diodes stay in full conduction
or do not switch off like they should reliably

this explains the machine loading, when you have no load connected, and getting worse with higher voltage

bob g

[Geno]

I decided to retest things to verify what I saw last weekend. Even though there is nothing hooked up to the alternator as I raise field current the engine begins to load. After hooking up the rectifier I notice this engine load above 30vdc rectifier output with no load on anything. In the future I just won't go above 24vdc. This is primarily a battery charger for camp. I can now hook up my flexmax to the 24vdc output and properly charge 12vdc batteries to my hearts content. It runs about 1000 watts of resistance heaters very nicely at 24 volts. No smoke from the engine, the alternator stays cool and rectifier is pretty warm to the touch without a fan on it.

Bob, I'm still curious how you plan to get 48 volts out of these alternators but it can wait.

Thanks, Geno

[XYZER]

Geno,
I just picked up my 2nd Leece Neville and plan on building a portable 12 volt charger like yours and will charge my camp batteries. I will probably have to buy an engine and was wondering if you feel the 6 hp is big enough? It sounds like it will do fine for battery charging. I checked out Carol Stream and I can get a 6hp diesel for around $400 That would put me way over your $500. I might just defect and buy a cheap 10hp gas one as much as I will use it.

[Geno]

My engine is 4 hp continuous and it will put out about a 1000 watts easy. I don't have the measuring equipment to be more precise. I didn't even know my engine rpm. My pulley ratio is 2:1 and I used the "that sounds about right" method to judge things. How much charge current can your batteries handle? I won't be charging more than 4 t-105s at a time so I'm limited to 600 watts. I'd think a 6 hp engine could handle a pretty big battery bank.

In the future I just won't go above 24vdc. This is primarily a battery charger for camp. I can now hook up my flexmax to the 24vdc output and properly charge 12vdc batteries to my hearts content.

Thanks, Geno

I don't know if your planning on manual field current adjustment like I tried but it doesn't work too well with a varying load. Alternator voltage goes up much more than I thought it would as current to the batteries goes down. Some sort of automatic 24 volt regulation is in order.

Thanks, Geno

[XYZER]

Geno,
I have 4 6volt Trojan golf cart batteries wired to 12v......maybe the 4.5hp diesel he sells would be enough and I might get an auto alternator instead maybe not.......Is your alternator double or 1/2 the engine speed?

[BruceM]

My memory is slipping, but there was a post on this forum about a company that had a complete Kubota based battery charger; they had a custom regulator for HD alternator that did 3 stage battery charging with temperature compensation.  It might be worthwhile to see what they might want ($) just for the external alternator regulator.

I can't be trusted to manually monitor and adjust a charge cycle, it's too easy for me to get distracted and forget...

[mobile_bob]

that was ample power that made and markets the kubota battery charger, there are others as well

they manufacture and sell a very good temp compensated 3stage regulator

a partial list of others

balmar, mc612 is their 12volt version
xantrex, xar12 is their 12volt version
amplepower, don't recall the model number
hehr power products, don't recall theirs either

there are some good heart interface units out there too, as well as a couple that are made and marketed out of england
who's names escape me just now.

a good 3 stage controller will do temp compensation with optional temp sensor, they will also monitor alternator temperature
as well, with an optional sensor. good ones will also have an amp manager function that is in my opinion most useful
in its ability to match your available hp to the alternator you are using. good ones will also have a soft start, programmable setpoints
and are programmable for 4-6 different battery technologies, (agm,gell,flooded, are the majors). the best ones will have a remote sense
capability.

prices range from 250 to 400 retail, and around 200-275 on ebay for new surplus units.

yes they are a bit pricey, but it only takes forgetting your reostat controlled charger for a few hours, for you to cook the price of a controller
out of an expensive set of batteries. over the life of the batteries the controller will more than pay for itself in increased battery life, more amp/hrs in and out of the batteries, and far less fuel burned.

bob g

[BruceM]

I didn't realize that there were a number of choices for smart alternator regulators.  Thanks, Bob! It would be very sweet if  the higher end ones have a "charge done- gone to float" signal for auto generator shut down. 

[mobile_bob]

Bruce:

i am not sure, and would have to go back and reread the doc's but i think there is a port that is meant for an indicator lamp
to tell you when the controller goes to float,

that lamp port would be all that would be needed to initiate a shutdown with a few other ancillary components, or very easily
integrated into a microcontroller system, as you know i am sure.

i am pretty sure balmar and the xantrex controllers have that ability, and likely so do amplepower and the english offerings.

if i get some time this afternoon i will look into that and see if it is possible.

bob g

[Lloyd]

Bob,

You could also easily use a potted voltage switch with a time delay relay. That's how I am going to operate my system. It's cheap and reliable.

i am currently using a dual potted w/relay to ventilate my batteries, on at 14.4 volts, off at 13.2 volts. W/20 min delay, to assure all gassing is removed.

Lloyd