Cheapish battery monitoring

[slawosz]

Hi,
I have 2 dual purpose batteries, and 1-2 switch. One day I use one battery, the other day another. I wanted to install battery monitor, but this setup requires 2 or dual monitors - around 180 quid . So instead, I am thinking about installing voltmeters from Amazon that will show current battery voltage and some ammeter like this:https://www.amazon.co.uk/Heschen-Single-Mounted-Electricity-Ammeter/dp/B06Y2XTPCL connected to domestic circuit to have idea what is current draw. I don't have many receivers: tiller pilot, plotter, light during the night. Just need to have a rough idea of how much electricity is being consumed so I can use the engine to recharge. Or 2 cheap battery monitors like this: https://www.amazon.co.uk/Heschen-Single-Mounted-Electricity-Ammeter/dp/B07W7XXKVF - but here I don't know if I could trust them.

What do you think?

 

[LiftyK]

I have two meters, one for house battery and one for engine battery. It is really useful to know what is going on. Reliability of state of charge is a subject of great debate but in my experience, having an idea of amps in and out, and volts at rest are the most informative figures. I would not be too concerned about the particular meter you choose, so long as you have sufficient panel space for your display and a route for your cables from panel to battery. The alternative would be a wireless meter such as the Victron Smart Shunt but you have already indicated the high price it would be to choose two of those.

 

[BabaYaga]

Hi,
I have 2 dual purpose batteries, and 1-2 switch. One day I use one battery, the other day another. I wanted to install battery monitor, but this setup requires 2 or dual monitors - around 180 quid . So instead, I am thinking about installing voltmeters from Amazon that will show current battery voltage and some ammeter like this:https://www.amazon.co.uk/Heschen-Single-Mounted-Electricity-Ammeter/dp/B06Y2XTPCL connected to domestic circuit to have idea what is current draw. I don't have many receivers: tiller pilot, plotter, light during the night. Just need to have a rough idea of how much electricity is being consumed so I can use the engine to recharge. Or 2 cheap battery monitors like this: https://www.amazon.co.uk/Heschen-Single-Mounted-Electricity-Ammeter/dp/B07W7XXKVF - but here I don't know if I could trust them.

What do you think?

I use an ON-OFF-ON-switch to monitor voltage and current on two battery groups (house bank and starter) with only one ammeter and one voltmeter.
To be useful the ammeter, in my view, should be able to measure both charge and discharge on the house bank (starting current bypasses the shunt, in my case).
Such analogue ammeters do exist, but one problem with analogue meters is that the same scale must cover charging currents of say 40 A or more and also small loads of a few tenths of an amp. Detail is lost.
I ended up installing this digital type:
https://www.bluesea.com/products/category/6/118/Meters/Mini_OLED_Digital_Monitor
EDIT: Forgot to mention, for this to work two shunts are needed, one for each battery bank. The switch makes it possible to use only one ammeter.

 

[awol]

I keep getting tech-porn from China in my mail box and bought one of these https://www.banggood.com/DC-500V-50A-100A-200A-300A-500A-Wireless-Voltage-Meter-Ammeter-Solar-Battery-Charging-Coulometer-Capacity-Power-Detect-Tester-p-1721288.html?cur_warehouse=CN&ID=517857&rmmds=search though a fair bit cheaper. Works well with lots of numbers - only problem is the screen brightness. I've had to fit a black-out blind to cut the light.

 

[Porthandbuoy]

On my last boat I fitted one battery voltage monitor from Amazon and a 3-way switch. Bat1- Off-Bat2. That and a simple graph showing volts vs %charge worked for me.

 

[bitbaltic]

Has anybody tried one of these?

Battery Monitor BM6 device for Cars & Campervans 12V Battery/leisure battery tester Compatible with Android iOS and Ipad with bluetooth 4.0 and above. https://amzn.eu/d/5Rh139t

Seems rather good for the money, although it has a lot of automotive features I don’t understand.

 

[Kelpie]

I've bought something similar to this but haven't installed it yet.
https://www.amazon.com/AiLi-Voltmet...y+monitor&qid=1677069055&s=electronics&sr=1-4

 

[DinghyMan]

Has anybody tried one of these?

Battery Monitor BM6 device for Cars & Campervans 12V Battery/leisure battery tester Compatible with Android iOS and Ipad with bluetooth 4.0 and above. https://amzn.eu/d/5Rh139t

Seems rather good for the money, although it has a lot of automotive features I don’t understand.

Yes, just returned two of the BM2 versions as they were draining batteries
Their bluetooth range is at best a couple of metres but the monitoring was as accurate as my meter

 

[bitbaltic]

Yes, just returned two of the BM2 versions as they were draining batteries
Their bluetooth range is at best a couple of metres but the monitoring was as accurate as my meter

Draining them significantly? Certainly defeats the purpose if the thing massively drains the battery you want to monitor. Prob not so much a problem for a car that's started and run more regularly than a boat I guess.

 

[DinghyMan]

Draining them significantly? Certainly defeats the purpose if the thing massively drains the battery you want to monitor. Prob not so much a problem for a car that's started and run more regularly than a boat I guess.

I was using them for a couple of cars, one used regularly, one not used for ages

First one I tested would flatten the battery in a couple of weeks - had issues after fitting to regularly used car so tested with battery sat on bench not connected to anything as a test when I was trying to trace what was happening, battery about 4 months old and fully charged before testing

When I was searching for them a major problem was that there are many different versions, some had the BM2 markings, some didn't, some probably the real thing, some probably not, I tested several versions and wasn't happy with them but would like to buy a reliable version, maybe the BM6 is better?

 

[Molteni]

I've bought something similar to this but haven't installed it yet.
https://www.amazon.com/AiLi-Voltmet...y+monitor&qid=1677069055&s=electronics&sr=1-4

I've used a couple of these monitors (one for each bank of three batteries) for a few years and they work well, constantly reminding me not to drop below the 60% charge level. Make sure you get one with a shunt capable of handling the maximum possible current you're likely to ever use.

 

[Spirit (of Glenans)]

IMHO, one monitor, fitted to the house bank, is sufficient. The house bank needs to be monitored, but the starter battery gets re- charged by the alternator after every use, and if it does lose enough charge to fail to turn over the engine, a pair of jump-leads to the house bank will get you started.

 

[BabaYaga]

My understanding was that the OP does not have a dedicated house battery nor starter battery.

 

[Spirit (of Glenans)]

My understanding was that the OP does not have a dedicated house battery nor starter battery.

I'm referring to a conventional setup. I had forgotten the details of the OP's arrangements, which fall outside the norm. Having reread it I would suggest that he may save some cash by just alternating between two presumably normal automotive starter batteries, but monitoring both will cost more than he is saving.
IMHO when the time comes for replacement, he should revert to the normal type of installation.

 

[slawosz]

I'm referring to a conventional setup. I had forgotten the details of the OP's arrangements, which fall outside the norm. Having reread it I would suggest that he may save some cash by just alternating between two presumably normal automotive starter batteries, but monitoring both will cost more than he is saving.
IMHO when the time comes for replacement, he should revert to the normal type of installation.

Actually, for my type of sailing, I think my setup is optimal. My batteries - two dual-purpose Hankooks were advised to me here by someone with a lot of experience. I think when the batteries will reach the end of life I will do the same. Here is original topic: Yet another 'which battery to buy' topic
I don't really need battery monitor, as I can always start the engine and charge the battery more often, it's nice to have though. I will see the options recommended above, as well as I will consider a simple analog ammeter, or voltmeter which will give me good enough estimation.

 

[superheat6k]

I keep getting tech-porn from China in my mail box and bought one of these https://www.banggood.com/DC-500V-50A-100A-200A-300A-500A-Wireless-Voltage-Meter-Ammeter-Solar-Battery-Charging-Coulometer-Capacity-Power-Detect-Tester-p-1721288.html?cur_warehouse=CN&ID=517857&rmmds=search though a fair bit cheaper. Works well with lots of numbers - only problem is the screen brightness. I've had to fit a black-out blind to cut the light.

I like the device, but not the casing / mount arrangement. I recently fitted a similar device for my AC, which replaced the original massive ammeter, which due to its 100 full scale was useless. I wish to find a similar looking DC device that could replace the AC VM, that is now redundant due to the new AC meter.

The small hole beneath the meter is the temperature probe picking up cabin interior temperature.

Also the KWH tally is very close to the recorded usage on the shore supply power meter. So I can easily check I am getting the shore power I am paying for.

 

[superheat6k]

I like the device, but not the casing / mount arrangement. I recently fitted a similar device for my AC, which replaced the original massive ammeter, which due to its 100 full scale was useless. I wish to find a similar looking DC device that could replace the AC VM, that is now redundant due to the new AC meter.View attachment 152367

I've opted for this meter - 2 off with a mount similar from traffolyte.

I have found an Ebay seller who knocks these up to a drawing for less than £10 each.

 

[Kelpie]

Very smart. Does it just tell you voltage or does it have a shunt somewhere?

 

[superheat6k]

Very smart. Does it just tell you voltage or does it have a shunt somewhere?

This just looks at voltage, which after all is the best measurement of a batteries condition. I did look at those measuring current and calculating % and power etc. But most are not accurate enough due to secondary issues that affect battery capacity. At the end of the what ever it is you are concerned with, it is the ability to restart the engine that really counts, and that is mostly about voltage.

I have made small mod to the traffolyte label - I already have cabin temperature on the AC multi function meter, so now the Port will measure outside temperature and the Stbd will measure the sea water temperature (at one of the engine inlets).

 

[Molteni]

As far as starter battery efficiency is concerned, the periodic use of a starter power meter device can help. It shows the ability of a starter battery to do it's job of providing enough power to start an engine.
Something like this