Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
MightyMax 18Ah AGM battery
SW, I did hook up the 10/2 charger, set it to the 2 amp side and left it on for 12 hours.  Case of the jump pack was still cold to the touch and the meter on the charger was all the way over, so perhaps that 14.4 to 14.6 it can put out helped some. I just charged it clamp to clamp with the switch “on”, thats about the only way I have to override the internal ac charger its built with.  I have no idea of the electronics in the “smart” charger and when it goes to float, but it was worth a try.

Thanks for the reminder to try and elevate the voltage.
They say when you get older two things happen, one is you lose your memory and the other, I forget.

Organized people are simply too lazy to search for stuff.
Good work.

I think it is important to stuff these batteries to a true 100% to retain that ability to be able to do the job of jumpstarting for as long as possible.

Long Ago I had a Schumacher jumper with a UB12120 battery inside, 12AH.  I carried it around for a long while after I had a dedicated house battery, and one time lent it out only to have the lendee come back and say it didn't work on a small 4 cylinder i 70F ambients.   Helping that lendee to get the vehicle started then was an annoying  process, as the vehicle was a half mile away in Baja and my van had an elaborate tarp shelter attached to it.

The jumper pack was  at least 5 years old at that point though, and I rarely charged it other than using the single stage wall wart which was stuffed inside the jumperpack casing.  I still have this and its specs are 12.0v at 800 mah, 0.8 amps.  When I put my DMM on it unloaded it read 13.8v.  Still have it somewhere.   I really think if I knew then what I know now, I could have gotten many more years and much more use out of that battery and would not have to removed and  half carried my gruop 27 battery to the other vehicle.

I tried a quick resistance measurement on the 18Ah MM battery  using my MV-50 air compressor but there is 12 inches of 20 gauge from battery to 30amp powerpole to wattmeter, so a lot of resistance is in those too thin cables. I decided to not waste any more time as there was a huge amount of resistance at 20 amps in those thin wires leading to wattmeter.

This particular powerpole was cut off of the cord from my older voltage fan speed controllers which plug into ciggy plug receptacles and  is rated at 2 amps max.  I wont bother with more resistance measurements until i get some 8AWG hooked to 45A powerpoles to a ring terminal on the battery.  Other projects are higher on the to do list ATM.
SO this 18Ah AGm battery has not been used for jumpstarting, It has only been very lightly discharged when used as a portable 12v power source, mostly powering fans and then usually quickly returned to brimming full.

I acquired some free metric 8mm2 wiring, which is just a bit thinner gauge than 8AWG, which would correspon to 8.26 mm2 cross section. Today, I bought 4 8AWG Ancor heavy duty ring terminals with a #10 hole and 2 6AWG with 1/4 inch hole and used up the last of my 45 amp anderson powerpole( ANEN windcamp Anderson clones)

I have two short runs of this ( almost) 8 gauge wiring from this battery, through a pair of 45 amps powerpoles. These powerpoles and ~8awg paired wires will then goto the cables which are in my engine compartment where the starter battery would be, if I had a starter battery in this stock location. I stuffed two wires into one 6awg ring terminal and will just tighten these down in the post clamps that are currently wrapped up with electrical tape. All ring terminals crimped with hydraulic crimper. The early HF crimper dies are so far off, i used the ones labelled 4awg to do 8awg lugs, and then used another set of dies that I filed out previously to properly crimp the 8awg lugs into a nice hexagon.

With the powerpoles connected, I will be able to simply turn my Main battery switch from battery 2( Northstar AGM-27) to battery 1, and be able to start the engine solely on the 18Ah AGM battery, or BOTH to have the 18Ah battery assist the Northstar in starng the engin, and or powering house loads..

I am assuming the 18 AH MM battery will be able to start it. If not the Switch goes back to battery 2, or to the BOTH position.

The MM 18Ah AGm battery will reside under where the original battery tray once resided. Not sure how I wlll keep it in place, yet but there is a divider in place which used to support the original battery tray which I cut out in june 2015 and never bothered to replace.

I have a pair of alligator clamps to which I have previously attached 8awg leads. I think these clamps came with a schumacher sc2500a charger I bought in 2007. The 8AWG attaches to one side of the clamp and goes to 45 amp anserson powerpoles, and to the other side of the clamp, I just added the 8mm2 wire to another set of powerpoles. So the wiring between battery and my original post clamps, or these alligator clamps is basically safe to continuously carry 90 amps.

My starter is rated at 1400 watts, which is 140 amps at 10 volts, 155.5amps at 9 volts. I am fairly confident the anderson powerpoles should be able to handle this amount of amperage for short durations. Enough to test anyway, not as if I will regularly ask this battery or the two pairs od 45amp Andersons to pass starter current. I just want to see if it/they can.

Anyway I have two wattmeters rated at 130 amps each( briefly) that I can hook inline when starting the engine. These wattmeters can easily handle 40 amps continuous so I expect they will have no issue with 80 amps briefly.

I will be able to see how low the battery voltage falls when cranking the v8 engine with just this 18 AH AGM battery, the maximum amperage consumed, the maximum wattage consumed, and also AH and watt hours, and I will do so tomorrow.

I will also be able to see how much this battery provides to assist the Northstar -27AGm. at various states of charge.

In theory I could leave my battery switch to BOTH, as both have the same recommended charging voltages. The battery seems to rest fully charged( 13.18v) at a higher voltage than the Northstar( 13.06v) so the Northstar will always pull the mm AGm down to 13.06v wut hno charging source present, which is less than ideal, and they wilol both generally be the same voltage if discharged together.

Anyway, more data coming, soon.
OK, the results are in, and they are a little disappointing.

There is certainly some measurement error possible.

The battery was 83f
The engine was 81F, and has not been started in exactly 2 weeks.

The engine barely started on the Mightymax 18Ah agm.

upon turning the key it rolled over and slowed significantly, then chug chuged along for 2.5 seconds before catching. If a regular full size battery behaved this way i would condemn it then and there, especially considering the 83f battery temperature.

My dashboard voltmeter dropped as low as 7.83 volts
My dashboard ammeter is not set up to measure amperage on this circuit, only my main battery.

Wattmeter 1 dropped to 8.24 volts
Wattmeter 2 dropped to 9.16 volts

Wattmeter one registered 122.58 amp peak
Wattmeter two registered 82.81 amp peak

Wattmeter one registered 1010 watt peak
Wattmeter two registered 776 watt peak

The amp hour and watt hour figures were not recorded and wattmeter two just said zero for both. Wattmeter two I do not like as it always recorded Ah and WH wildly incorrectly. it is a windynation clone that came with 8awg wires.
Wattmeter one is a gtpower clone that i modified with 8awg( from 12awg)

So my '1400watt' starter consumed 1786 watts. I have never replaced it in my 17.5 years of ownership of this van. It could be original. This excessive wattage could be indications it is worn out.

Amperage wise, it consumed over 200, 205.39 amps!!

I'll have to compare readings on my regular battery monitor, but it does not record minimum voltage or maximum amperage, and does not refresh teh readings multipe times a second, perhaps twice, so it might not capture the peak amperage or minimum voltage which actually occurs.

Anyway, While I would perhaps trust this 18Ah MM AGM battery to be able to start a warmed engine in mild ambient temperatures by itself, I would not trust it to be able to start an overnight cold engine in sub60F temperatures, at least not with my existing starter which appears to be drawing significantly more wattage that it is supposed to.

The differences in wattmeter readings could certainly be different resistance on teh wiring feeding each from the battery, or the fact that wattmeter two has always been less trustworthy. The differences could be product inaccuracy too, in addition to different wire/connector resistances.

Noneof the connectors felt warm to the touch after startng the engine

My clamp on Ammeter showed the MM AGm battery accepting 11 amps at 14.7v by the time I climbed back out the side door and walked to the front of the Van.

What I found strange is that the wattmeters only read amperage in one direction. And since the alternator was providing the current, the wattmeters should have read zero. One did, but the other showed amperage flowing from battery. I unplugged wattmeter 2 and then wattmeter one showed 0.0, as it should, but then a minute later showed 0.35 to 0.65 amps flowing from battery.

i cannot explain this. I though perhaps the huge currents fried something in my wattmeters, but I then hooked them up to my one fan and it did not read current in reverse and read current in the normal load/source direction, accurately.

While I cannot say for sure my Starter was absolutely consuming 1786 watts, but I also do not believe the wattmeters are 400 watts off either. A worn starter motor should indeed draw more wattage and mine is certainly no less than 17.5 years old, and could be 30+ years old. Mine is a 1989 model year but was fabricated in Canada in june of 1988.

So anyway, there we have it. The MM battery will no doubt be able to assist my highly dischrged or weakened northstar AGM to start my engine, and could perhaps start my engine on its own if the Northstar completely failed with a shorted cell. it would depend on the battery temperature nd the engine temperature, and the condition of the battery at the time it were asked to do so. which is why I intend to keep thisbattery as healthy as possible for as long as possible by keeping it fully charged.
that little battery not only turning over but starting an american v8 is pretty impressive if you ask me,should fire a honda 4 cylinder right up

variables in starter performance from the starter itself to say having the heads resurfaced making the compression higher making the engine harder to turn over making the starter work harder

Stern needs to start saving up for a couple new batteries
I think my northstar is good for 6 to 8 more months. And i likely will just get one more.northstar, but a group 31 instead of a 27.

This 18 ah back up jumper battery just insures i do not need more than one battery for house and engine duty. Since it can by itself crank my v8. It will have no issues assisting the northstar when its cca and capacity falls even lower.

Forum Jump:

Users browsing this thread: 1 Guest(s)