regular battery chargers

We really need a topic to discuss regular battery chargers. Since you can't just to to the wal-mart and buy a 24V unit, we can use industrial kinds (or modify one like I did before, but that one is not in any way regulated, and I want to address professional types separately than modifications)_

I picked up this little gem today. It's a LaMarche Constavolt A5E-10-24V-A1, and came from DRMO. It's about as old as the deuce.. Charged at up to 10 amps, and then when the batteries are full, switches to tricke, then pulse. This is all done with a saturable reactor, and the only electronic parts are the rectifier diodes.

The power cable and battery cable had to be replaced and I added a power switch and pilot lamp underneath. The unit mounts on the wall in the garage, on a piece of plywood that also holds the automatic transfer switch for my emergency power system. I made the battery cables out of a 100FT extension cord since the current is only 10A and when it comes time for the float charge, the current is so slight that the voltage drop is fairly negligible. Judging by the voltage drop at 4A (measured at the batteries and at the charger), the resistance of the the long cable is about 1 ohm. This is a very significant amount of resistance but since it's just to maintain the batteries not fast-charge them, it's fine with me. I need to figure out the correct voltage for floating wet lead-acid batteries.

in the "inside" picture, on the right beneath the terminal board is a saturable reactor. The jumpers 1-6 are for setting the unit for whatever AC input voltage is present, in my case the 120V seting for 117V measured voltage should be fine. Unit has two fuses for the AC input and two for the DC output. On the right is the power transformer, rated about 600 watts. I don't know what the resistor is for, but i suspect it sets the current in the saturable reactor. Note there seem to be two marks on the resistor. I think that the movable tap might have been in between these originally, but I am not messing with it until I understand itnbetter. Below the transformer is the rectifer.

In the pic of the front panel, note the red glow underneath. This is the pilot light. Note: I used a 36V lamp so it would not burn out

OK so it's just another gadget but I like it!

harbor has a 12/24 volt chager

Craftsman sells them through the catalog too. Grainger sells Dayton ones too.

So regular 12V with 10 or 60 amps won't work at all?

Nay, well, if you remove the cable that links the two batteries..pos to neg little dogbone lookin' thing, All you have then are two 12VDC batteries. Just takes twice as long to charge them one at a time

Walmart used to stock a 12/24 charger... I have bought a couple of them.. but two little 12 units one for each battery work fine too... No need to panic... There are many different cheapie battery chargers for 24 volt... I think the remote charter from the Scooter Store for wheel chairs... will work for you to... Call Gramma and borrow hers... RAM

A 24 volt charger should only be used if the internal resistances of the two series connected batteries are identical.
Precision battery maintainers, such as Chargetek 500, monitor each battery separately.
If the batteries are of the same brand, same age same discharge pattern (no 12 V tap for CB's etc) only then is a 24 volt charger okay to use.
IMHO a 12 volt charger used twice is the way to go, but I do like your find Patrick. Many power supplies have a "sense" wire for compensating for long wire voltage drops, perhaps you can work that into your charger/regulator...

On the subject of chargers and batteries, I discovered my batts were dead and then froze solid. Took them out of truck , in house, thawed them out which took 24 hours with heater under them, put on charger, 12 volt and recharged both . Not sure if the plates warped bad or if they will work, but gonna try them soon after the cold wave here is over. My neglect I guess, I let the truck sit too long and it drained them down to nothing.Question for cranetruck: If you have a 24volt charger, will it charge both the batteries as they are connected?

Like Will, I disconnect the dogbone link between the two batteries and charge each one on an old sears charger I bought at a yard sale for 5.00 bucks. Works just fine for me.

There's no need to remove the battery interconnecting cable, just put the charger cable on each battery as if it was 12v hookup. It's only 24v on the output.

pa.rich said:

...Question for cranetruck: If you have a 24volt charger, will it charge both the batteries as they are connected?

Click to expand...

Yes, that's how they are normally charged while you run you truck.

I'd like to have one of those chargetek units but this one cost me only $10, figuring I paid $5 each for 8 vacuum tubes, and $10 for a rackmount shelf, for a total of $60. Add $10 for the cost of the surplus panel lamp holder and power switch (both of which I added) and an old extension cord and cheap some battery clamps, and so I have maybe $20 in it.

A thought is to leave the battery equalizer engaged while charging. I have to say that my batteries are identical and under normal non-equalized conditions of the truck alternator operation, the voltage difference between the individual batteries is within 0.2 to 0.4 volt. I believe that keeping the cells properly watered and checked helps this.

The voltage when I quit last night was 26.5V, and I'll report the voltage later today since I put the unit in service last night. I need a "specific gravity" tester. There are instructions inside the unit for setting the voltage taps according to the specific gravity of the electrolyte once the batteries have charged for a week. Unfortunately, the voltage level for a float charge changes with temperature, the best chargers can probably compensate for this as long as they are in the same ambient environment as the batteries, or have a temperature sensor at the end of the battery cables to sense the ambient temp of the battery environment (I bet none do), but is this splitting hairs?

Although I understand about the unit using the saturable reactor to 'switch' to trickle mode after some level of voltage is reached (more like "gracefully entering trickle mode", since a saturable reactor is involved), but I don't see how it pulse charges, except that since it has no filtering, it may gently 'tweek' the battey 120 times a second during the peaks of the power sinewave -at this point we are probably talking 100mA pulses? Magnetic amplifiers have always fascinated me.

Not to be confused with solargizer and other "de-sulfating" type pulse-maintainers with their 10-40A 10-50 microsecond pulses.

Also a warning inside says it is not to be used with "sealed" valve-regulated lead acid (VRLA) batteries such as likely found in Grandma's scooter or in the typical UPS. Those require a filtered charge current for longest life, as do AGM batteries (as I imperfectly understand it).

pa.rich, it would be valuable to know how your batteries recover. Would it be right to suggest limiting the charge current to <5A for a time, to be gentle and avoid any localized heating or localized increase of chemical reaction?

OPCOM said:

... Magnetic amplifiers have always fascinated me.

Click to expand...

Funny, me too, there used to be a company in Joliet, Illinois, that made Magnetic amplifier kits for hobbyists, but they went out of business in the sixties, guess when solid state devices took over for the duration. Should have a couple of books on the subject...

The design of the saturable reactors is somewhat of an art ? I am always hopelesly lost in the math in those fascinating books. My WWII veteran friend tells me that he used to work on the mag-amps that rotated the turrets on battleships. Apparently a bank of 6L6 vacuum tubes tube was the control element in a multi-stage mag-amp for the traverse of a 3-gun turrent that must have weighed a hundred tons. Shows what can be done with what is at hand. later he worked on dive bomber radars. Somewhere I (hope I still) have the saturable reactor out of a 32V 50A Nobatron power supply. A single 6L6G (a 19 watt vacuum tube) controlled that 1800 watt unit, quite amazing.

I've asked the manufacturer LaMarche for the schematic and adjustment instructions for the one I have. Let's see if they will freely provide it for the common good, or will want to charge alot of money!
http://www.lamarchemfg.com/
An American company since 1945 in DesPlaines, IL.

""We believe every touch has the potential to win or lose a customer. For us here at La Marche, employee training is key. We believe that relationship building and good old-fashioned trust is what will take La Marche to the next level. We think about product in terms of total customer satisfaction. Growth and diversification through vertical integration.""

Frank's Surplus has an eBay ad:
24 V SOLAR CHARGER MILITARY TRUCK M998 M151 M37 M35 M54
Here is the link:
http://cgi.ebay.com/24-V-SOLAR-CHAR...054QQihZ014QQcategoryZ588QQrdZ1QQcmdZViewItem

after 19 hours, here's the reading: 27.2 volts at the batteries. I think it will be just fine.

A while back I posted about the frozen batteries, I recharged them, but they will not crank the truck. I guess the plates warped. I put a couple of old 12vt batteries in after recharging them and the ole M211 started right up.Guess its a wasted $200.00 for the 5 month old batteries. Live and learn.

Too bad, properly maintained the batteries will last for 5 or more years. Actually have over six years on a pair, now moved to the 8x8. Got new ones for the trip to the West coast.

Now after several days, I have 28VDC on the batteries. This is perhaps excessive for float-charging flooded cell lead-acid batteries, 14V per battery!

Can someone with battery experience help out? Is the correct final float charge the same voltage as shown for 100% charge -and this figures in the temperature as well?

I moved the link down one position on the charger to reduce the float slightly. Will report back later.

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Here is some interesting info from a website about batteries: http://www.capsante.com/Articles/battery_info.htm


II. Open-Circuit Voltage Test
For accurate voltage readings batteries must remain idle (no charging, no discharging) for at least 6 hrs, preferably 24.

* Disconnect all loads from the batteries.
* Measure the voltage using a DC voltmeter.
* Correct the readings to 80°F
o Add .028 per cell for every 10° above 80°F
o Subtract .028 per cell for every 10° below 80°F.
* Check the state of charge with Table 1.
* Charge the battery if it registers 0%-70% charged


If battery registers below the Table 1 values, the following conditions may exist:

1. The battery was left in a state of discharge too long.
2. The battery has a bad cell.

Batteries in these conditions should be taken to a specialist for further evaluation or retired from service.

Table 1. State of Charge as related to Specific Gravity and Open-Circuit Voltage
Percentage of Charge

I purchased an Xantrex charger inverter it is mounted under the passenger seat and if I want to charge it I plug in the cord and it has the same three levels of charge described in the opening comment. The neat thing about it is it also serves as a 2000 watt inverter from the 24 volt system. I will post a picture of it tomorrow or at latest by the weekend depending on how they call work tomorrow for the ice storm