Measuring battery condition
Easiest way to measure battery level of charge?
Forum Discussion
- Dealing with multiple disciplines is never easy.
If you yourself will spend some time with a hydrometer and verify voltage on your meter to the actual state of charge you will have a system as good as any simple measurement around. Even an amp-hour meter needs to be "zeroed" once a month, using a hydrometer.
AGM batteries are easier to manage
Lithium is impossible without an amp-hour meter system.
This is like answering a "Celestial Mechanics Made Easy
Or learning phasor algebra in 3 days question.
Or the fraudulent "Learn Spanish Using 5 Easy Tricks"
A weekend of using a voltmeter and you won't get in trouble. Try it for a month, 100% boondocking and you will end up on **** Cree. I put the asterisks in. - The right way to measure the state of charge of a battery is not a voltmeter. You need a battery meter. Also known as a state of charge meter, battery gauge, etc. It involves a shunt wired into the negative battery cable to measure the current into and out of the battery over time. You program the meter with your battery capacity and the fully charged parameters and it measures current in and out and calculates the percentage state of charge. Tri-Metric is a good one. Victron makes one. Outback calls theirs the Flexnet DC. Magnum calls their the ME-BMK. Link 10 used to be one but I'm not sure they are made anymore.
As you can tell from all the previous posts, measuring just the voltage is subject to many variations. I don't know very many people who, when camping, are willing to turn off the RV, disconnect their batteries, and wait 15 minutes just to find out the SOC. A nice SOC meter with a wall mounted display is the way to go. KD4UPL wrote:
The right way to measure the state of charge of a battery is not a voltmeter. You need a battery meter. Also known as a state of charge meter, battery gauge, etc. It involves a shunt wired into the negative battery cable to measure the current into and out of the battery over time. You program the meter with your battery capacity and the fully charged parameters and it measures current in and out and calculates the percentage state of charge. Tri-Metric is a good one. Victron makes one. Outback calls theirs the Flexnet DC. Magnum calls their the ME-BMK. Link 10 used to be one but I'm not sure they are made anymore.
As you can tell from all the previous posts, measuring just the voltage is subject to many variations. I don't know very many people who, when camping, are willing to turn off the RV, disconnect their batteries, and wait 15 minutes just to find out the SOC. A nice SOC meter with a wall mounted display is the way to go.
I would agree with this. A voltmeter is a bit like the old joke about bikinis - what it reveals is interesting, what it conceals is essential.
On my previous truck I used a Tri-Metric and the battery monitor of the Blue Sky solar controller. Now I use the battery monitor of the Magnum inverter/charger.
With AGM batteries, I cannot do a hydrometer test and, as noted, in real life my batteries are always discharging - refrigerator, heat/fans, etc. And this does not count the induction stove/microwave or the espresso machine. ;) Simply not worth the effort to disconnect all loads for a half hour or more.
But this begs the real question - what are you trying to learn and why? A common answer is, "Well, I want to know if I have to recharge my batteries." Largely irrelevant as, at least with lead acid, the answer is always "Yes!" You want to recharge any time you can, every time you can, for as long as you can. So the real issue is to be sure that you have good chargers and that they are connected so that they come on whenever they can. One of two reasons that solar is so helpful.
I tend to watch the hour counter most of all - I blow off about 125Ah overnight and I always want to see it back to 0 as soon as possible.
N.B. With lead acid, that still means that you need hours of absorb charging.
Bottom line, most of us will be better off with some form of battery monitor. The SmartGauge is the simplest.
You can learn more about the SmartGuage and all manner of other things about lead acid battery charging here: SmartGauge The SmartGauge is sold in the US by Balmar.Freeway Flyer 05 wrote:
You also mention the terms "battery condition". There is an easy way to get a baseline for the batteries overall health. Take note of charge times. When a battery is in poor condition the voltage will spike when you try to charge it. That tricks the charger in to thinking the battery is fully charged. So the charge cycle happens much quicker than normal. Instead of charging for an hour like it normally did the bad battery will say its charged after a few minutes.
Easiest way to measure battery level of charge?
Thats a rough example. BUt just something to note. Works with any size battery. Little ATV batteries on a battery tender will turn green really quick when the battery is toast.
edit to say you can also trick the battery tender. If you are ever in a pinch and cant get a new battery just keep taking the battery tender off and on. Each time it will pump a small bit of amps into it.
