Alternative 24V DC Charging System Installation

[1800 Diesel]

Ok I did a few searches on the forum but couldn't find much discussion other than solargizer usage. Either I'm not good at using the search feature or there's just no material posted.

I've got two MEP2s that are showing no-charge readings while running. I plan to go through the "Speddmon checklist" on both of them but in the event the stator is found to be defective I am working up a "Plan B" 24V charger installation, complete with a on/off switch, circuit breaker (for the AC side) & a charger on indicator light. An option could also be to install an actual voltmeter showing voltage reading, though this would be redundant since the unit already has the on-board gauge showing the "red" or "green" battery charging condition.

Things to consider:

1) Where to tap in to get the 120VAC? My first thought, piggyback on the same line that feeds the convenience outlet fuse, though on the "un-fused" side so this new circuit doesn't affect the 15-amp breaker load.

2) Where to install the charger? Possibly underneath the control cubicle on one the frame components and on small shock isolators.

3) Where to install the breaker, switch & indicator light. Thinking here to go into the control box. It's tight in there but there's enough real estate for these components and this location would minimize AC wiring lengths.

4) DC wiring would simply ride the existing harness to the battery & starter area.


5) Per TM, the on-board system puts out 6.5-10 amps & the unit I'm looking at puts out 5 amps. The unit being worked will be used on my brother's remote acreage (no grid power available) to run an irrigation pump and some lighting and it will also have a solar charger to maintain the batteries.

So has anyone already done something like this?

Will the 5 amp rate be enough? Are there any other DC loads besides charging the batteries? The charger I'm looking at has three levels: full charge rate, maintain rate & a float charger rate.

If anyone has a comment (pro or con) with my plan please weigh in.

As a footnote, I would normally do a repair on the on-board system, but this is the same unit that I was unable to pull the blower wheel, hence the Plan B consideration. Don't want to send my brother a unit that can't charge the batteries...especially since it'll be at a remote site...

Thanks.

 

[Harleyd315]

I bought a small 24v battery charger/mantainer mounted it on top of the output terminal box,plugged it into the conv outlet and just ran the wires over the fuel tank to the batteries using the alligator clamps that came with the charger. This will charge the batteries when running. I also mounted a solargizer to mantain the batteries when sitting for long periods. Hope this helps.

 

[jbk]

this is one type i use 2 bank 8 amp. marine waterproof 3 stage auto charging. i can keep it plugged up to maintain the batts. or if the charging system fails simply plug to the conveniance outlet. i have it mounted on the trailer fender $80.00. thats another charger in the third photo bottom left, note the a/c plug. 15 amp. marine

 

[1800 Diesel]

Thanks--I figured I could offer that too, but wanted something that looked a little more integral like a "factory" installation. Your idea is definitely easier & less cost though...

 

[1800 Diesel]

this is one type i use 2 bank 8 amp. marine waterproof 3 stage auto charging. i can keep it plugged up to maintain the batts. or if the charging system fails simply plug to the conveniance outlet. i have it mounted on the trailer fender $80.00. thats another charger in the third photo bottom left, note the a/c plug. 15 amp. marine

That looks good too but will still try to come up with an integral/internal arrangement. Will post pictures when I get it done. BTW, that's a nice looking paint job on your genset! Looks like a new unit...did you paint the stencils your self?

 

[jbk]

yes

 

[Isaac-1]

I doubt the actual amp draw on the DC circuit is more than a couple of amps, perhaps someone can check this on a running unit, the rest would go to recharging the battery, if this is the case you can probably easily get away with a 5 amp charger, maybe even something smaller in the 2-3 amp range. I would tend to opt for an epoxy sealed industrial or marine rated charger (something that could stand being out in the weather). It of course needs to be a modern multistage charger, and capable of outputting 24VDC. I use a Bosch C7 charger as a maintenance charger on my MEP-002a, I picked this one mainly because it supports both 12 and 24V operation as well as supporting AGM style batteries, so it is versatile and can do backup duty charging car batteries, deep cycle boat batteries, etc. It however is not what I would pick for this sort of application as I doubt it would stand up to the vibration for long. For more rugged installations I have had very good luck using Guest brand industrial and marine chargers, most of their models are sealed in epoxy, and they are built to last, of course they are not cheap.

Ike

 

[storeman]

1800,
Did you ever test the ac voltage from the stator to the dc VR?
Jerry

 

[edgephoto]

Will the 5 amp rate be enough? Are there any other DC loads besides charging the batteries? The charger I'm looking at has three levels: full charge rate, maintain rate & a float charger rate.

The DC system has to charge the batteries for sure, however do not forget that the fuel pumps are 24VDC, the fuel shut off solenoid is also 24VDC and if you use them, the panel lights are 24VDC. If the on-board system is good for 6.5-10amps your 5 amp charger may not be enough to run these items and top off the battery. Why not turn the pumps on a measure the current needed to run them. Then measure the fuel shut off solenoid current draw. Add them up and if less than 5 amps you are in business if not than you need a bigger charger.

 

[1800 Diesel]

1800,
Did you ever test the ac voltage from the stator to the dc VR?
Jerry

Planning to do that tonight. We're doing a little sheet metal painting work on this one since it's for my brother. But we're about 1/2 hour from lighting off & testing....came inside for coffee break...

 

[1800 Diesel]

The DC system has to charge the batteries for sure, however do not forget that the fuel pumps are 24VDC, the fuel shut off solenoid is also 24VDC and if you use them, the panel lights are 24VDC. If the on-board system is good for 6.5-10amps your 5 amp charger may not be enough to run these items and top off the battery. Why not turn the pumps on a measure the current needed to run them. Then measure the fuel shut off solenoid current draw. Add them up and if less than 5 amps you are in business if not than you need a bigger charger.

That sounds like a good plan...thanks for the input!

 

[storeman]

Planning to do that tonight. We're doing a little sheet metal painting work on this one since it's for my brother. But we're about 1/2 hour from lighting off & testing....came inside for coffee break...

If you have not tested the output from the stator, you wasted a lot of effort trying to get to it. If you have acceptable output, your problem is likely the DC VR, assuming the attached resistor below the DC VR is good (probably not the correct description, But I couldn't locate it in the TM).
Jerry

 

[1800 Diesel]

1800,
Did you ever test the ac voltage from the stator to the dc VR?
Jerry

Jerry,

We just shut down. DC voltage at "red band wire" 23.5.....batteries reading abt the same (one of the batteries has a weak cell but after a full charge it will read 13+ volts). AC voltage from stator 16.5...

Since this is the unit with unmovable blower wheel...time to order a 24v charger...

Thanks.

 

[1800 Diesel]

If you have not tested the output from the stator, you wasted a lot of effort trying to get to it. If you have acceptable output, your problem is likely the DC VR, assuming the attached resistor below the DC VR is good (probably not the correct description, But I couldn't locate it in the TM).
Jerry

Yep, Speddmon said the same thing, but I explained to him there was quite a lot of grime on the stator windings so between that and possibly rusty magnets I was hoping to get the wheel off to do some cleaning on both, but that wheel did not want to move. Now it's confirmed that something is amiss in or around the stator so I'm back to ordering and installing a 24v charger.

Thanks again.

 

[storeman]

Good move on the alternative charger.
Jerry

 

[1800 Diesel]

Looking at a "Plan C" option for setting up an alternative charging system. If a 120v/30v transformer (with adequate amperage capacity) could be wired into the 120VAC side & the two output leads were connected in place of the stator leads, would the system them function "normally"? (This concept assuming all other components are functioning properly.)

I can locate 30v output transformers but can't determine (both from my lack of in-depth knowledge of electricity & still learning the TM's content) what amperage is actually provided by the two stator leads. I see in the TM that the stator is supposed to provide 30-35 VAC and that the DC side should put out ~6-10 amps, but nothing found specifically that states the "AC amp input requirement" as provided by a properly functioning stator.

Most of the 30VAC transformers I can locate have output amperage rates in the 0.5-1 amp range...

Anyone have any thoughts?

 

[Triple Jim]

The charging alternator is a permanent magnet unit, and the regulator is a shunt type that wastes unwanted current. A standard transformer would not like this, since shunting extra current becomes a partial or full short circuit to the transformer. You could use a transformer with a series regulator to make a regulated 28V supply. With current limiting to protect the transformer, you'd have a charging system that works as well as the original one. It's probably easier to get a battery charger though. If I need to do this, I'll use my Soneil 2408 charger that I use to maintain my batteries, and that will put out 4 Amps and easily fit in the control box if/when needed. I got it used from eBay for $28 shipped.

 

[1800 Diesel]

The charging alternator is a permanent magnet unit, and the regulator is a shunt type that wastes unwanted current. A standard transformer would not like this, since shunting extra current becomes a partial or full short circuit to the transformer. You could use a transformer with a series regulator to make a regulated 28V supply. With current limiting to protect the transformer, you'd have a charging system that works as well as the original one. It's probably easier to get a battery charger though. If I need to do this, I'll use my Soneil 2408 charger that I use to maintain my batteries, and that will put out 4 Amps and easily fit in the control box if/when needed. I got it used from eBay for $28 shipped.

Triple Jim--Thanks for sharing the info on the transformer needing a series regulator...guess that complicates things a little. I already have a 24v/5 amp battery charger on hand. I'm trying to come up with an alternate system that could be installed in the MEP2 or 3 units for cases where the stator is found to be defective and owners may not want to (or can't) pull the blower wheel. So, I understand that this is harder than installing a battery charger, but would still like to pursue other options. I'll look into the series regulator option & its cost--high cost will eliminate the "plan C" & I'll go back to "plan B" as per my original post. Thanks again for your input.

 

[Triple Jim]

Understood, but why not mount the charger in the control box instead of building a charger and mounting it in the control box?

You can build a series (pass) regulator easily enough, either a linear one or a switching type, but you're effectively building a primitive battery charger, and I'd rather have a non-primitive one.

 

[1800 Diesel]

Got it--thought the transformer option alone would be pretty easy substitute for the 30VAC feed and all other on-board components would still be utilized--again not knowing enough about the application and additional components needed, I'll go back to plan B which installs the 24v charger but taps somewhere into the 120v side whereby the 15 amp outlet (I meant breaker.) is not affected and the charger isn't using one of the outlets. Also I like the idea of having a red indicator light (showing charger is on) and a switch to turn on the unit after light-off and voltages are stabilized...