Harbor Freight Mexcharger Question

[Snowman9000]

Prior to going on a recent dry camping trip, I tested my new Mexicowanderer HF Charger. 2/10/55 or whatever it is. If I understand it, for regular charging, it should be set at 10 amps and Start, which should yield about 17-18 amps and no tapering.

The battery was at 12.3v, so not deeply discharged, when I tried it. It put out the 17 amps, but the voltage was only 13.1. Is that how it works? I thought the voltage was going to be in the upper 14's. I didn't try it on the trip, I left it home due to space constraints, given the above performance.

[Snowman9000]

deleted by me. question already answered.
🙂

[mena661]

Snowman9000 wrote:
I was hoping to use the HF for charging from 50 to 90%, instead of my built in 7345. But it looks like it's more suited for going from 80 or 90 to 100%. Please correct me if I'm wrong.

You can but you'll have to babysit it. Follow MEX's steps but if you're not using a converter first then MEX's route will take longer.

[Snowman9000]

I was hoping to use the HF for charging from 50 to 90%, instead of my built in 7345. But it looks like it's more suited for going from 80 or 90 to 100%. Please correct me if I'm wrong.

[mena661]

MEXICOWANDERER wrote:
18 amps out of a 10 amp charger for that kind of money is tough to beat.

I got almost 19 from mine. I figured it was because of the size bank I was using. Will it do that on smaller banks too?

[MEXICOWANDERER]

18 amps out of a 10 amp charger for that kind of money is tough to beat.

Here's a suggestion for charging by generator:

Use your "smart" high power charger long enough until it goes stupid and cannot finish charging the batteries to a level above 14 volts. Toss the smart charger in the loony bin until next time, connect the HF charger on Manual 10 amps NOTE THE TIME OF DAY. Continue to charge the battery at the 10 amp setting (the amperage will have dropped way back by then - it's natural ans expected)

When the voltage reaches 14.8, NOTE THE TIME. How many hours or minutes did it take?

Buy a 120 volt cutoff timer or a wind up alarm timer. The next time you need to boondock generator charge, it will be a lot easier when you have an idea of how long the finish charge is going to take.

AGAIN!

Charger manufacturers can get SUED if they insist their charge regimen is "correct" and batteries boil dry. But batteries that sulfate way too soon are darned near impossible to prove that the manufacturer used the wrong charge algorithm. Got it? THEY UNDERCHARGE WAY WAY WAY Undercharge on purpose.

Show me a SMART charger that is applied 30 cycles, and battery electrolyte density is correct. Good freakin' luck.

[wa8yxm]

Snowman9000 wrote:
Clearly I have a lot to learn. (sigh)
🙂

I thought it should push whatever amps it does at high voltage right away, like my B&D charger does. I'll have to test my Battery Tender too. I am under the impression it start out in the mid 14's.

Amps: The lower the battery voltage the higher the amps, UNLESS the voltage is so low the charger regulates them to a lower (and safer) setting.. Some smart chargers (The really smart ones) will charge a completely dead battery,, at a very low rate (few amps) till they come up to "Chargable" range.

Volts, however, is what you said you measured. And unless you are pumping in 50 or more amps they tend to stick right close to the battery's voltage. (minimum charge voltage of battery).

[mena661]

red31 wrote:
I thought the MEX HF charger was for doing a periodic overcharge to 15.0 v after charging or slight self discharge.

I was planning on trying this with a ole 'diehard' 6/2 amp before building the timer switch that would let me turn it on to X hrs and walk away.

This correct, the Start mode is for manual use with this charger. Most of us with this charger are only using it to do equalizations and finishing charges. You CAN use it to charge the batteries but like was mentioned, the amps are low so it will take a long time to do that. Also, you need to keep an eye on it to make sure it does not overcharge your batteries. But at 10 amps, it will take a number of HOURS to do so. MEX does not trust the auto charging function of this charger but the manual portion works just fine.

Golden, the reason why MEX likes this charger is because it's robust. It will not burn up. I've used this NUMEROUS times for finish charging, equalizing, and destratification. Finish charging can take 2-3 hours with my bank and this unit works like a champ.

[red31]

I thought the MEX HF charger was for doing a periodic overcharge to 15.0 v after charging or slight self discharge.

I was planning on trying this with a ole 'diehard' 6/2 amp before building the timer switch that would let me turn it on to X hrs and walk away.

[Golden_HVAC]

Hi,

THe battery will stay close to it's starting voltage until a LOT of amperage is pushed into it. If the battery tender is only rated at around 2 amps, it will take some hours for it to raise a battery from 11.8 volts to 12.8 volts (full) and them only a few more hours to raise it from full (12.8) to 14 volts.

Under no load, the battery charger might put out 14 volts, but connect it to a 11.9 volt battery, and it will limit the output.

It is a good thing you did not leave the 2/10 amp charger on the start mode a long time, or the small transformer inside would have melted or a fuse blows. It is only designed to be in the "Start" mode for less than 1 minute at a time, with a considerable rest time to allow the charger to cool off afterwords. Probably printed right on the charger is instructions to use start mode a maximum of 30 seconds, then unplug for 10 minutes (or more).

THe charger is only "Rated" to put out 10 amps all day long. The start mode is only good for a minute or so.

Once the battery is full, say by using the RV charger (should be rated at 45 amps or so) then the 2/10 amp charger will put out about 13.6 volts or 14.2 at the most (hopefully) while the "Start" mode might put out a battery cooking 15 volts or more.

What are the desired battery voltages?

Three stage chargers work like this.

Stage 1 - puts out the maximum charger rated amperage until the battery voltage is about 14.1 volts, then holds 14.1 volts while tapering the amperage until the 14.1 has been held for about 1 hour.

THen stage 2 it will reduce the voltage to 13.8 and still run a lot of amperage into the battery, at a rate so fast the battery will feel warmer than the air around it. Yes some water will be lost at this high voltage.

Then stage 3, it will reduce to 13.2 to 13.4 volts, and hold this voltage until the charger is unplugged.

Some very smart chargers will count 30 days, then go back to stage 1 for a hour or so each month. This is what the Trace Pro Chargers do.

So best thing? Let the RV charger do it's thing. If you are not getting good results from that charger, replace it with a good converter/charger.

One problem you might have is if you have a decent charger, and put on your 2/10 amp charger to "Help" it, the charger/converter will see the 14 volts, and quickly shift from the stage 1 bulk charge mode to stage 2 or even stage 3, and not put out very many amps at all. This will slow the overall charge rate for the battery, by not letting the 45 amp RV mounted charger do it's thing.

Fred.

[Snowman9000]

Clearly I have a lot to learn. (sigh)
🙂

I thought it should push whatever amps it does at high voltage right away, like my B&D charger does. I'll have to test my Battery Tender too. I am under the impression it start out in the mid 14's.

[wa8yxm]

You said you attached it to the battery turned it on and the voltage went up A LITTLE, where as you expected A LOT.

The problem is not the charger..

What you are seeing is the charger/battery ratio... Give it time and the voltage will continue to climb. You have a big battery there, takes time to raist the voltage with a fairly slow charge.

now if you tried to pump say 60-100 amps into that battery, THEN you'd see a bit jump in voltage, but at 10 amps, not so much.