Thursday, 27 December 2018

The care of batteries

I am a member of the 12v boating group on Facebook. They are a group of knowledgable and very helpful individuals who are happy to help with good and detailed advice.

The mantra of the group when it comes to batteries is know how to care for them - first and foremost. There are many many types of batteries, charging systems and installs but it all comes back to knowing your batteries and what is going in and going out. The other message constantly made is know the power demands - do a power audit ....

So one thing I am looking at now from my recent learning it how many amps are going into the batteries as part of the charging process - this gives a good idea of the state of charge of the batteries. I do have a Smartgauge and this has been very helpful on Waterlily and Percy in helping me manage my batteries - the % SOC is, I have read around, the 'best' way to know when to charge. This I understand is because the system is doing many calculations on charge and discharge over the batteries life so it adjusts the SOC % to account for the natural 'ageing' of the batteries. Many ask for the banks combined AH and use that as the starting point for calculations, not ever changing so not allowing for the reduction of AH capacity over time = incorrect information ( my understanding)

However I'd still like to see that amps in and out.

Now my understanding from this group - thanks Brian, is I need a (at least) a DC clamp meter to read the amps on the main cable to the batteries to see what is going in at any point - and I guess on the same cable to the 12v side to see what is going out etc. £20 - £35 so not too much but very manual.

Now I could fit a BM2 or Victon or Phil meter ...... all three do what I am looking for  -  I'm less fussed about the % remaining as I have the Smartgauge which I trust for that. I guess it could be down to the install ease and also the ability to get the information... meaning the Victron with its Bluetooth is best here as i can  be around the boat and get the info I need  = lazy man

So I guess the two questions I need to resolve is can I fit either the BM2 or Victon alongside the Smartgauge and should I cut my costs and just buy a cheapish clamp meter and take occasions readings  (meaning opening up the batter cover - not a big job to be honest? )

I did have this post scheduled for automatic posting on Friday.... however I have just got into some deep reading of an excellent thread on CanalWorld forums about this subject. So now I have volt meters and ammeters to think about.... I may yet edit this post again before it's posted....

Here is the link to the post I am reading - its long !


Tom and Jan said...


For what they are worth..... Attached are the links to two blog posts I wrote about the installation and performance of the BMV600 in combination with the SmartGauge

You will have to cut and paste the links into your browser



Nev Wells said...

HI Tom

Thank you very much for the very useful and helpful links that do indeed provide me the answers to my questions.

I am sure I'll go for the Victron (with the bluetooth) for my belt and braces battery management with the Smartbank I have. Just got to decide cheap and cheerful wet batteries or some 6v traction may come down to what fits as I have a prescribed battery box in the engine room aboard NB Percy. I don't suppose you can recall if you included the smartgauges negative on the reading side of the shunt or did you keep that on the battery terminal....?

Take care and thanks again for taking the time to provide the info I was looking for .

Brian and Diana on NB Harnser said...

I use to have a Sterling battery Monitor, it served me well until the grey smoke leaked out after about 12 years, I have replaced it with a Phil meter, £30 and it tells me the voltage so I know if I need to charge the batteries and an ammeter to be able to read charge current so I know when they are fully recharged, ie its down to about 2 amp on my 225 Ah battery bank. Your Smartgauge is ideal to tell you when to charge and how full your batteries are, but its not so accurate when they are charging and solar can play hell with the accuracy due to a voltage rise not proportional to the charge
We will probably pass Percy tomorrow

Anonymous said...

You may find that a DC clamp meter needs to be zeroed every time you use it (because it uses a Hall effect sensor to measure DC current) unlike the AC setting where it acts as a current transformer. In a house you can fit a clamp meter / ring to the meter tails for your smart meter but I don’t know if you can leave one on a DC cable in the same way. I think not...

Nev Wells said...

Thanks for the comment Brian. I think you have affirmed my plans to get a hard wired solution - I like the Victron, but it is expensive . At first I thought reading the 225 a/h battery bank was a bit low but I guess the daily cruising you do means there is no great need for a large battery bank. Might be around tomorrow, not sure yet, have a great cruise back, the weather looks set fair.

Nev Wells said...

Hi Anonymous, thanks for the comment and useful information. I was thinking they were the same thing. We certainly had a ring on the mains at our last house... the smart meter at the cottage is a guess a bit more technical. As above I am more than likely going the Victron route as I like their kit and I like the hard wired approach. Plus I think their kit only has the data cable to the head unit whereas others have power cables to the unit and my install needed to be as clean as possible as its within the engine room and where the batts are makes the need for clean wiring essential.

Tom and Jan said...

All the negatives went through the shunt. This was the only way I could ensure I was capturing the data on ALL the current (amps) entering and leaving the battery bank. I had to make a small brass busbar to achieve that.