Another AGM conditioning question
This is my chassis battery, an agm I got used and have little experience with. Trickle charger failed in storage, it is dead as a doornail. Not covenient to babysit it for long hours on meanwell or...
Forum Discussion
Back from a morning's hobble and electric cart hijack at Costco.
Barring this level of accuracy, that inductive panel DC ammeter that Mr. Wizard so kindly pointed out to me, is an acceptable substitute. The current MUST BE READ on a single cable going to a single connection on the battery post. No multiple wires on any battery post. That's what bussbars are for and this is where I catch a majority of amp hour meter errors at.
- Whenever meter readings do not jibe and I am left scratching my head...
- I test the meter
- A 100-watt incandescent 12-volt light bulb draws 7.40 amps. If your wall meter shows different then the whole system is suspect...parts and or assembly
- This is where a DC handheld inductive tester is invaluable. If it says 3.8 amps and your panel meter says 6.7 amps stop the music
- I purchased a 100-ampere 100mv Manganin lab shunt off eBay for eight dollars. Ran a foot of eight gauge to each side of the shunt
- Huge steel jaw clamps to the ends of the 8 gauge
- I can connect anything to anything in a jiffy. Disconnect pos battery cable. Clip one jaw to this cable the other to the evacuated battery post
- Set a DMM to the milli-volt scale
- ONE millivolt = one ampere across the shunt
- Since the resolution of the DMM is finer than one millivolt fractions of amps can be resolved
- This qualifies or disqualifies anything else I own
- A few times down the gilded path of BS readings led me to not blindly trust anything anymore.
Barring this level of accuracy, that inductive panel DC ammeter that Mr. Wizard so kindly pointed out to me, is an acceptable substitute. The current MUST BE READ on a single cable going to a single connection on the battery post. No multiple wires on any battery post. That's what bussbars are for and this is where I catch a majority of amp hour meter errors at.
- Take the current needed to light the DC lamp test base. For simplicity lets call the draw 7.5 amps
- Eliminate every other draw in the rig
- 0.00 amps showing on all meters
- Including the rig's panel amp hour meter
- Turn on the light bulb. Leave it on for four hours
- The sum of 7.5 x 4 is?
- 30.0
- Yes amperage declines as voltage goes down but unless you are running a tiny house battery Delta T span error will be minimal. No compensation needed
- Wanna play lab tech? Add the sum of the beginning voltage (after surface charge removed) with the voltage shown at the end of the test
- 12.7 + 12.3
- ----25--- right?
- Divide by (2)
- 12.5 right?
- Not enough variance to amount to snot for this test
- Does the amps + time agree with your amp hour meter amp hour reading?
- It doesn't?
- Guess which gizmo is wrong. It isn't guesswork, this is hard facts...
