12 volt battery tester?

[Rebotco]

2 hours ago, Dr Bob said:

Whilst you may not be interested in bluetooth now, in the future you may be.

Also if you become more interested in 12V stuff, and you start thinking about Lithiums or more advanced monitoring of power, the Victron monitor allows you to integrate with other bits of kit. I have mine connected to a Rasp pi so I can collect data on the Victron connect site. The attached chart is the sort of output you can get. Once again you may not be interested in that now....but you may be in future. Accessing boat power data remotely is an advantage.

I prefer the low profile of the BMV display.

At knocking on 80 yrs old, I'm more likely to be interested in plastic teeth than any bluetooth!! 

And the future you extoll is likely to be somewhat curtailed for one of my vintage.

I just like boating while the creaking bones still allow it - but I can't get terribly excited about graphs and tail currents etc 

[Tony Brooks]

5 minutes ago, Rebotco said:

At knocking on 80 yrs old, I'm more likely to be interested in plastic teeth than any bluetooth!! 

And the future you extoll is likely to be somewhat curtailed for one of my vintage.

I just like boating while the creaking bones still allow it - but I can't get terribly excited about graphs and tail currents etc 

I agree with you about graphs but unless you get to grips with rested voltage and tail current then you may as well carry on as now. Don't do any battery monitoring or testing and simply replace when things stop working to your satisfaction. To be honest I suspect the cost of the battery monitor will outweigh the cost of batteries between now and when you have to give up boating.

[Rebotco]

25 minutes ago, Tony Brooks said:

I agree with you about graphs but unless you get to grips with rested voltage and tail current then you may as well carry on as now. Don't do any battery monitoring or testing and simply replace when things stop working to your satisfaction. To be honest I suspect the cost of the battery monitor will outweigh the cost of batteries between now and when you have to give up boating.

Not sure that's what I want to hear - even if it is true!

Actually I think I do have a working understanding of those matters, though not to any great depth.

[Tony Brooks]

48 minutes ago, Rebotco said:

Not sure that's what I want to hear - even if it is true!

Actually I think I do have a working understanding of those matters, though not to any great depth.

Well I am four years younger and 60 years of working on the floor has taken their toll so have given up boating, you are doing well.  All you need is a working knowledge of rested voltage and tail current as long as you can apply it to regular readings at critical times throughout the 24 hours. Just ignore the % charged on the monitor.

[Rebotco]

3 hours ago, mrsmelly said:

I've had several and prefer the nasa bm2. Main reason is that for grown ups no glasses needed to read it and waterproof so can be mounted outside. 

Thank you.  That's just the sort of information I'm looking for.

[Keeping Up]

Another vote for the BM2. It is clear and easy to read, and if you set it up carefully it is really quite accurate and informative.

[Tony Brooks]

10 minutes ago, Keeping Up said:

Another vote for the BM2. It is clear and easy to read, and if you set it up carefully it is really quite accurate and informative.

I think its not just the setting up, its how you deal with your charging after it has been set up. To remain accurate it needs resynchronising very regularly and a periodic recalculation of battery capacity and resetting that.

[Dr Bob]

17 hours ago, Tony Brooks said:

I find that interesting. Especially a sit must show how your BMS shuts the charging down, and how    quickly the lithiums got to what is considered a safe full charge. Lead acids would only be about 80% charged in that time.

 

Would it be an electric coffee maker at about 09.15 and again at about 10.15? If not what was it?

 

Thanks

Tony, I think you are asking about my graph. I have put it in this post so easier to see.

 

This was from back in August when we were still getting to grips with charging on the new boat. The graph gives quite a bit of info re charging of Lithium batteries.

The initial peak at 9.20 and the 'ragged decay' for the first 10 mins was the engine being turned on and then me faffing around with the BtoBs. Cant exactly remember what was going on! I think one of the BtB's (we are using 2 *60A ones in parallel) was only set at half power hence the 60A current (should have been 80A ish). By 9.30 I had sorted it and the current went up to 85A. The batteries were about 190Ahrs down on full capacity from the other graphs in the system. We motored for around 2 and a bit hours but just after 10.00 I noticed the current had dropped to 40A so checked the BtoB's and noticed one had gone into float - hence the 40A current. More faffing reseting the BtoB to a better custom programme and off it went again back up to the 'full' charge amps delivered by the BtoBs. At 11.45 we finished our cruise and turned off the engine. The voltage had only just got to 13.7V and this is around 75% SoC at the 60A charging rate. We had put in around 150Ahrs during the cruise in the 2 and a bit hours. Batteries very happy sitting at 75%. This is typical of our battery usage now with us being around -200Ahrs overnight and getting back to -50Ahrs at the end of each day. The batteries seldom get over 80% full as we tend to just do 2-3 hours a day.

I guess if these had been lead acids we would have had to run the engine for a long time to get them back to full (ie the whole -190Ahrs from the night before). How many  hours do you reckon?

 

[cuthound]

On 07/11/2020 at 09:35, Murflynn said:

a cheap version of what the AA man uses before he tells you you need a new car battery.

 

 

I regularly test my leisure (actually traction in my case - leccy boat) batteries by the good old-fashioned headlamp bulb discharge test, applied to each battery in turn after disconnecting from each other.  Just make sure the bulb is not close to anything flammable - it gets damn hot.

 

Completely agree with this.

 

I spent my entire career in various jobs in  critical power and saw lots of battery monitors and testers. Very few gave anything like accurate results, and the handful that did cost £000's.

 

Capacity can only be accurately assessed by a discharge test at a lowish, say 10 hour rate at a constant current load, although a reasonable stab can be made by measuring rested voltage whilst looking at amp hours discharged on an amp hour counter.

 

As Tony Brooks has said, and accurate voltmeter and ammeter is all you really need,  although an amp hour counter is a useful addition. Rested voltage voltage will give accurate SoC, and tail current at 14.2 volts plus will show when a battery is fully charged.

[ditchcrawler]

4 minutes ago, cuthound said:

 

 

 

Capacity can only be accurately assessed by a discharge test at a lowish, say 10 hour rate at a constant current load, although a reasonable stab can be made by measuring rested voltage whilst looking at amp hours discharged on an amp hour counter.

 

 

And boy is that boring, noting volts amps every 30 minutes.

[cuthound]

1 minute ago, ditchcrawler said:

And boy is that boring, noting volts amps every 30 minutes.

 

Yup I remember it well, every two years we used to do a 100% discharge on each battery, taking specific gravity, current and voltage readings every 30 minutes (adjusting the current on the load bank every 15 minutes to maintain a constamt current to compensate for the dropping volage), then when the cell voltage dropped to 1.85 volts, adding readings from a cadmium electrode (which is electro negative tp the negative plate) and taking readings every 15 minutes until the first cell reached 1.75 volts.

 

At that point we dropped the load and immediately began recharging, again taking specific gravity, voltage and current readings every 30 minutes and adjusting the charge current every 15 minutes, until the cells began to gas, then reverting to a constant voltage charge until the tail current had remained constsnt for 90 minutes.

 

The whole process took around 24 hours, having to take food, tea and toilet breaks between readings. Knackering and brain numbing work.

 

I was really glad when they replaced the 2 volt wet cells with 6 volt monoblock VRSLA's from 1980, as they only needed a discharge test at 6 years old to determine whether capacity had dropped to 80% at which point the battery was replaced, and the power system automatically charged them,  without the need for readings to be battery readings to be taken.