Pros and cons of Battery Equalizer / Dual alternator

[Trango]

Hi Guys

I am starting to wire the electrical on my project, and I'm torn between doing one of two systems. I'd love some feedback, and I invite you to comment either on the synopsis or any of the scenarios in the details of potential options.

Thanks for any feedback!


Synopsis:

I am torn between using a battery equalizer to achieve 12v off of a 24v system OR using a combo of a 12v alternator and a 24v alternator (similar to a CUCV system). The engine is a repower, originally 12v and stuck into my 24v chassis.




Details of potential options:


Scenario 1
1. Two Batteries, one single 24v alternator, with a battery equalizer to both handle 12v loads (starter and run solenoids - civvy engine).


Pros

- Simplicity, single alternator and no extra brackets or belts to fab or deal with


Cons

- Single alternator (single point of failure)
- If either battery fails, the system would likely become imbalanced and cause errors.
- I would have to rewire a fair amount of the engine harness, as the 12v output of the current alternator



Scenario 2
2. Two batteries, one 24v and one 12v alternator. 12v alternator feeds the "low side" battery (the one whose negative is connected to chassis ground), 24v alternator feeds the "high side" battery.


Pros

- Not sure if I can or should use my battery equalizer (this is an open question I have).
- 2 alternators would create, in the event that a single alternator failed, at least temporary redundancy on the 12v duties (starting and running, which are the most critical)
- In this particular case and with this engine, I wouldn't have to break alot of the existing wiring on my engine by removing the 12v alternator


Cons

- Need to fab a new bracket and install belt for the 24v alternator, but there is an extra drive pulley for it and it wouldn't be that hard.
- If the 12v alternator fails, it would mean battery death since this will be an imbalanced system



Scenario 2a
2a. There is a variation on "2.", which is two completely seperate battery systems: one 24v system from two batteries, and one 12v system, for a total of three 12 v batteries).


Pros

Would allow for the most redundancy and options in the event of failure.


Cons

Complex, expensive (batteries) and would crowd the battery box.



Any thoughts? I am a sponge on this topic.

Best,
Bob

 

[m-35tom]

a equilizer will not handle the starter unless you spend $$$$$ on one. run the 12v starter on 24 volts, it will not care. (you should use a 24v selenoid) keep as much as you can 24 v. then use a vanner 50 amp eq for any of the 12v stuff you may have. i got one on evilbay for $85

tom

 

[Green Toys]

I got the vanner equalizer use 2 group 31 truck batteries for 24 system and added an additional group 31 for my 12 v systems. The equalizer keeps it charged just like adding an alternator , with out addin one. Did it 3 months ago, run a radio with a 12" sub and 1200watt amp, electric trailer brakes and lights, and a garmin GPS.

 

[rattlecan6104]

a equilizer will not handle the starter unless you spend $$$$$ on one. run the 12v starter on 24 volts, it will not care. (you should use a 24v selenoid) keep as much as you can 24 v. then use a vanner 50 amp eq for any of the 12v stuff you may have. i got one on evilbay for $85

tom

this unless you really plan on running A LOT of 12v goodies, then I personally would go with your scenario 2a.

 

[nk14zp]

I use 2a.

 

[Stalwart]

a equilizer will not handle the starter unless you spend $$$$$ on one. run the 12v starter on 24 volts, it will not care. (you should use a 24v selenoid) keep as much as you can 24 v. then use a vanner 50 amp eq for any of the 12v stuff you may have. i got one on evilbay for $85

tom

The equalizer never has to be rated for the full load of an intermittent draw, just has to cover the constant current draws. I agree, a 12V starter will handle 24V just fine IF you don't let it crank too long or crank with low batteries. I too got a 100A one for $100 and it is even the new type.

 

[Trango]

Update - I became pressed for time and space, and simply put a 24v Delco 10si alternator along with an equalizer. Should work great.

Best,
Bob

 

[ApopkaFL]

I spoke to a guy that buys and sells buses he said they have equalizer`s on them to run all the 12v lighting he told me he would sell me one for 350.00 says it will do the job fine. Any thoughts on the ones that come out of buses?

 

[m-35tom]

bob, one additional thing i can say is that an eq will of course force both batteries to charge at the same rate. i had a batt that would not hold a charge and the other was fine. now with the vanner, the weak batt has seemingly recovered and acts fine.

tom

 

[Stalwart]

$350 is a lot of money for something the rest of us paid $85-150 for. Look on ebay and save "Vanner equalizer" as the search criteria and wait a bit. You should have one shortly for around $100 or so. We are all using the "Bus" type, but some of ours are new, not used for that price.

 

[steelypip]

It's all about the rated amperage output. Get that number and the source doesn't matter as long as it works and is properly made.

 

[OPCOM]

You can run a 24V alternator and use your 12V starter if:

1. you use a battery equalizer
2. the equalizer is current limited
3. keeping in mind the EQ has a definite current rating and will only recharge the battery that hard, your starting requirements must be able to be handled by the amp-hours of the EQ recharging the starting battery. Meaning that if you have extended cranking times this won't work well.

However, your post says 12V starter solenoid. If the starter motor is 24V and the solenoid is 12V, then only #1 above applies. This assumes the starter solenoid coil 'hot' is always separate from the 24V starter motor connection, and not briefly connected to it when cranking.

If the starter is 12V and you want to keep the 12V alternator, you can buy a DC converter that will make 24V from the 12V to run whatever else.

Final note with a battery EQ. Most are made to be used in vehicles that spend a lot of time running. They can draw an appreciable but small current at all times and this may discharge the upper battery into the lower one over time, like a month. A draw of 0.07A will eat 50AH of charge from a battery over one month time. This is overlooked in many cases.
To avoid this problem, I used a 24V 50A contactor (similar to that motors or central air conditioner condensers) and wired it so that the EQ was disconnected from the +12 and +24 of the batteries except when I threw a switch to energize the contactor's coil. Instead of a manual switch which I preferred, you could hook it to the truck's power switch for automatic use. The coil on mine was DC, not AC. An AC coil may draw too much current when run on DC and this depends on the DC resistance of the coil winding. Therefore in some cases avoid using a less-costly purpose-made air conditioning contactor with a 24VAC coil unless you know about this sort of thing.

In the picture can be seen the contactor and the EQ. I used #6 wire.

 

[JasonS]

You can run a 24V alternator and use your 12V starter if:

1. you use a battery equalizer
2. the equalizer is current limited
3. keeping in mind the EQ has a definite current rating and will only recharge the battery that hard, your starting requirements must be able to be handled by the amp-hours of the EQ recharging the starting battery. Meaning that if you have extended cranking times this won't work well.

However, your post says 12V starter solenoid. If the starter motor is 24V and the solenoid is 12V, then only #1 above applies. This assumes the starter solenoid coil 'hot' is always separate from the 24V starter motor connection, and not briefly connected to it when cranking.

If the starter is 12V and you want to keep the 12V alternator, you can buy a DC converter that will make 24V from the 12V to run whatever else.

Final note with a battery EQ. Most are made to be used in vehicles that spend a lot of time running. They can draw an appreciable but small current at all times and this may discharge the upper battery into the lower one over time, like a month. A draw of 0.07A will eat 50AH of charge from a battery over one month time. This is overlooked in many cases.
To avoid this problem, I used a 24V 50A contactor (similar to that motors or central air conditioner condensers) and wired it so that the EQ was disconnected from the +12 and +24 of the batteries except when I threw a switch to energize the contactor's coil. Instead of a manual switch which I preferred, you could hook it to the truck's power switch for automatic use. The coil on mine was DC, not AC. An AC coil may draw too much current when run on DC and this depends on the DC resistance of the coil winding. Therefore in some cases avoid using a less-costly purpose-made air conditioning contactor with a 24VAC coil unless you know about this sort of thing.

In the picture can be seen the contactor and the EQ. I used #6 wire.

Generally, you won't drag down your 12V battery below ~10% depth of discharge. The minor difference in DOD will self equalize during a normal charge.

 

[mudguppy]

running a custom 24V alternator and 100A Vanner equalizer - happy as can be.

as noted before, just because the equalizer is rated at xxAmps doesn't mean disaster if 12V is pulled exceeding that amperage. all it means is that the equalizer will only equalize at a certain rate and will have to play catch-up when/if that amperage is exceeded.

the 100A Vanner is a nice piece. i expect a long service life out of it.

 

[cranetruck]

Ref: Patrick's schematic above.
Be careful with this arrangement and don't use it when the engine/alternator is running. Switching the alternator load off will create some serious voltage spikes (load dump) and possibly kill the regulator .

 

[bottleworks]

An equalizer is the way to go. I have an extra 100 Amp equalizer for sale, BTW.

 

[rolling18]

great info here!!
does anyone know how to physically attach a Battery equalizer to the batteries?

there does not look like enough battery post to add more cables to it...
any pictures?

BTW I bought a sure power duvac2 24v-12v EQ/ converter (can be run in either mode) 75amp from a pawn shop for $30!! think weighs about 30 lbs!

 

[mudguppy]

great info here!!
does anyone know how to physically attach a Battery equalizer to the batteries?

...

the equalizer has three (3) terminals:

• ground (first battery Negative lug)
• 12V+ (first battery Positive lug)
• 24V+ (2nd battery Positive lug)

there is nothing easier than adding an equalizer.

 

[rolling18]

the equalizer has three (3) terminals:

• ground (first battery Negative lug)
• 12V+ (first battery Positive lug)
• 24V+ (2nd battery Positive lug)

there is nothing easier than adding an equalizer.

my sure power equalizer has 2 pos posts, 2 neg posts and one called 12v output 75A cont.

also, in the deuce what battery is considered the first or "a" the ones closest to the engine or farthest?

thanks!

 

[goldneagle]

my sure power equalizer has 2 pos posts, 2 neg posts and one called 12v output 75A cont.

also, in the deuce what battery is considered the first or "a" the ones closest to the engine or farthest?

thanks!

The equalizer he is writing about does not have any connections for the load side. You take the loads off the batteries themselves. The equalizer just keeps the voltage even in the batteries. This way when you recharge them they charge to the same level.