12V battery at 12.5 volts. Should I worry about sulfation?

You need to remove from the post the negative terminal that connects to the body and insert the ammeter in its place between the negative post and the body.

 

Use a DC current clamp.
No need to disconnect anything.
https://gtc.ca/wp-content/uploads/2020/08/CMSeriesBR-EN_1303.pdf

 

That scenario it’d be in parallel, ie the electrons would have two paths between car body and neg post.

To achieve meter in series you disconnect car battery neg post from car body, instead connect car battery neg post to meter to car body. That way all electrons have to flow through meter.

if meter is not auto-ranging, start measuring in amps first, then if no reaction, switch to highest milliamperes, and step down. Just in case there’s a high amp usage. To avoid blowing a fuse in meter.

note, if you want to avoid losing memories due to temp disconnect of battery, a memory saver can be used, just for the disconnected time. Basically provide the car with alternate 12 volt source during the disconnect.

I’ve heard accuracy is iffy? For sure easier though.

 

A current meter, like any device, has an accuracy class. Some are good in accuracy, some are worse.
Ideally, it is better to take measurements through a 100-200A current shunt, including it in a series circuit between the battery and the wiring, connecting to the shunt in parallel with a high-precision milliammeter.

 

The CM100 listed above is $170 and claims 0.1% dc ma clamp on accuracies. For most parasitic draw tests you need to reliably read somewhere down to 15 ma dc current.

Some reviews of the $170 meter say it can do it (comparable low ma clamp-on meters or adapters start at $500) while some reviews say repeatability is bad (meaning one reading one time changes to another the next) and most reviews suggest it is very slow for any basic voltage or ohms reading (3 or 4 seconds) and is polarity sensitive in dc volts (meaning accuracy is poor in dc volts).

The same can be done with the $5 harbor freight meter (used to be free) when wired in series. Most likely you have a meter that can do the series connected ma test.

I have a couple of ma dc clamp meters that were highly reviewed but found they were only stable at 100 ma or more. This is fine if the parasitic draw is the "drain the battery overnight" kind but not useful for the 40-90 ma "drain the battery in a couple of days" situation.

Again the series connection ma technique is accurate and cheap. Given most cars rarely present with chronic parasitic draw (usually a light, aftermarket add-on or an obd2 device draw issue) and most quickly discharging batteries are damaged batteries (easily tested with a load tester) then the series connected, accurate and stable ma testing is the go to for pros and diy as well.

Measuring parasitic draw accurately does not fix the problem, it just provides a metric to determine if your wiring interventions over the next hour(s) is doing any good.

Cycling 12v power is not a real problem from an ecu memory perspective; maybe the radio presets have to be redone, often not even that.




The real problem with series (above) OR high dollar dc ma clamp-on is ensuring no lights or ecus are active. Disconnecting followed by reconnecting 12v with a meter in series can cause ecus to be active for a few minutes in modern cars. To eliminate the wait, a temporary jumper (above) can be maintain power while the meter is added, then removed for ma testing.

 

You do not need an ammeter to measure the parasitic drain. In fact, you cannot measure the parasitic drain using an ammeter—period.

Why? Simple: The parasitic drain is not a constant quantity. It will vary throughout the day. Your ammeter would have to have a digital interface with a time-integral-average function. Good luck finding one with that.

Here is how to measure the parasitic drain:

Get a Bluetooth battery monitor that samples the battery voltage every two minutes, such as the BM2:

BM2 battery monitor at Amazon

Then, use the following table to determine the SOC. Note that the battery needs to rest for at least 16 hours before you can measure the resting open-circuit voltage, and you should not come close to the doors with the key fob, which will start drawing a large current. (If the resting time cannot be as long as 16 hours, then choose a time like twelve hours and be consistent.) Once you tabulate the resting voltage everyday for the same resting duration (you cannot use 16 hours for one day and 20 hours for the next day), then you also have the SOC, which means you have the daily SOC loss and, hence, the daily average parasitic drain. You must linearly interpolate the data in the table. Note the OEM battery is a flooded cell.

 

Completely and utterly wrong. A vehicle will have a parasitic drain of 15-35 ma 99.9% of the time when shutdown. A bad drain will show during this time.

 

You are saying this because you do not have a battery monitor that shows how the parasitic drain varies throughout the day. I do.

In any case, using an ammeter is cumbersome, will give you inaccurate results in the best-case scenario because you are not doing an integral time average and most likely garbage results as the parasitic drain will vary throughout the day.

Get a battery monitor instead. You will have a much, much better picture on your smartphone of what is going on in the battery without even opening the hood.

By the way, the healthy parasitic drain in my 2021 Prius Prime Limited averages 45 mA—out of the range you gave.

 

The first illustration shows an intermediate configuration, which avoids losing memories. Following the amperage measurement you'd want to reconnect the jumper, before reinstalling the neg cable. In a nutshell, you're ensuring the car always has some 12 voltage available.

 

That clamp-on Hall-effect ammeter that measures the current using Ampère's circuital law (the line integral of the magnetic field around a wire is proportional to the current through the wire) is great if you want to look at the charging current etc., but as I explained earlier, it won’t be very helpful in determining the parasitic drain, which is actually not a current but a charge (the time integral of a wildly varying current). Get the cheap BM2 Bluetooth battery monitor, and you will not only find out how much parasitic drain is really there but a lot more like how the battery charges and doesn’t.

 

I use a volt meter that displays volts while I'm driving. Sometimes I see 14.3 volts, and other times it's 12.3. I've stopped worrying about it, as it seems to be operating normally.

 

It used to be expensive to buy a clamp ammeter that would measure both AC and DC. That was before this: https://www.aliexpress.com/item/4000575319270.html?src=google&pdp_npi=4%40dis!CAD!70.38!36.18!!!!!%40!10000009741357069!ppc!!!&src=google&albch=shopping&acnt=631-313-3945&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&gclsrc=aw.ds&&albagn=888888&&ds_e_adid=&ds_e_matchtype=&ds_e_device=c&ds_e_network=x&ds_e_product_group_id=&ds_e_product_id=en4000575319270&ds_e_product_merchant_id=108355505&ds_e_product_country=CA&ds_e_product_language=en&ds_e_product_channel=online&ds_e_product_store_id=&ds_url_v=2&albcp=19366866438&albag=&isSmbAutoCall=false&needSmbHouyi=false&gad_source=1&gclid=Cj0KCQiAy8K8BhCZARIsAKJ8sfRj7EOU9E0HEobjri0OSlPsyAwFVE1H8o0A_pZSm2TabC0JYZN78LcaAr9xEALw_wcB

I've had one for a few years, and I find it to be quite accurate.

 

1) Make sure the cells are topped off with fresh distilled water.

2) Use a charger that this that I bought from Amazon. (a)Use the REPAIR function until it turns off by itself, (b) then switch it to the charging mode (STD for standard battery) . This charger is great and it prolonged the life of my batteries. If you don't drive every much, it's good to top off the battery every once in a while:

Amazon.com: YONHAN Battery Charger 10-Amp 12V and 24V Fully-Automatic Smart Car Battery Charger, Battery Maintainer Trickle Charger, and Battery Desulfator with Temperature Compensation : Automotive

 

I did not disconnect the battery on my 2010 Lexus LS460 when I repaired & charged it 2X after the battery flattened by accident. If you don't want the desulfator then skip the repair function and just use the charging function. The charger let you choose the different functions or battery types. If you have any more questions then just message the seller on Amazon.

 

It hooks under the battery-terminal nuts. It is very light and its cables support it, but you can tape it on the battery if you like.

 

Charging function on these battery maintainers have a desulfation phase, but it is safe to the leave the battery connected. However, it is not safe to leave the battery connected if you use the repair mode, which is more aggressive with desulfation, as the voltages will be too high.

 

I wouldn't worry too much about sulfation. It usually happens over long periods of running at abnormally low voltages.