Battery Monitor

goldcoaster · Senior Member

Battery Monitor

Solo Steve · Senior Member

Hi Goldcaster

I have a BM1 hooked up to 2 100ah AGM battery and it works fine. You may have to reprogram it for Gel type.

Also if you have a charger fitted and you have not set the charging cycle for Gel batteries it may not be supplying the

correct voltages.

Steve

justcruisin01 · Guru

goldcoaster wrote:
I have the Clipper BM 1 and recently it started to play up,batteries were very low in the percentage column,it was discharging when it should of been charging. So off to Batteryworld got them tested only 15mths old as good as the day they went in. He suggested I go and see my autoelec ,made an appointment as bad as a dr.,next week the earliest. So I googled my BM1,works well with lead acid Batteries,I changed over 15mths ago to Gel Batteries cant find anywhere if it is still compatible or wether this is my problem. Open to suggestions. Thanks

Dont know the clipper BM1, but there is a difference between the lead acid & gel when it comes to charging. the main difference is the voltage point where the charger switches from boost/bulk charge to the absorbtion.

If the BM1 is a multi stage charger it may have a program that can be reset &/or a different wiring code.

I run redarks & there is one wire you reconfigure according to the battery type, eg. lead acid, gel & matt glass. This wire is connected to positive for one, neg for another & disconnected for the other.

There may be some thing along these lines you van look at.

JC.

PeterD · Guru

The Clipper BM-1 seems to be a badge engineered version of this one - http://www.nasamarine.com/proddetail.php?prod=BMN-1_Battery Can you confirm that please.

If so it just intergrates the current flowing in both directions thorugh it to calculate the state of charge (SOC) of your battery. The only thing that should happen with a change of battery chemistry is it will not be quite as accurate in its calculation of SOC. To get the best accuracy from it you may have to change the setting for the Peukert's constant in the BM-1s internal setting. You will have to ask your battery supplier for the value for your model battery.

You said "it was discharging when it should of been charging." Are you saying here that the monitor was showing that the battery was discharging when you actualy knew the battery was being charged? In that case has someone been fiddling with the wiring around the current shunt area? Something is astray with the monitor or your system. If you don't have a handbook then you can download it from the link on the first link in this reply.

goldcoaster · Senior Member

Thanks Solo Steve and PeterD, I think both of your answers merit. Too technical for me so I will pass both comments onto the auto elec. Just recently he fitted an Inverter to the Motorhome maybe he has done something to upset it. Thanks again.

Solo Steve · Senior Member

Hi Goldcoaster

I checked my BM1 manual and it does not matter what type of battery you are using but if you your new batteries were of a different capacity to the old ones

you must reprogramme the new total battery capacity into the BM!. You may also need to rezero it as well. If you dont have a manual you can probably download

google Nasa BM1 which is the same type as the clipper i believe. I still suspect that your charger needs to be reset for gel type batteries though.

Steve

PeterD · Guru

As Steve and I said above, there are things in the monitor to be reset. There are two PDF files on the first link I gave you above. The first is the handbook that will give you the setup instructions. The second is the diagram of how to wire the unit into your battery system, you can use that to check if the auto electrician has done something to the setup when he installed the inverter. Below the links to the PDF files on the bottom LH corner of the BM-1 web page you will see the picture of the shunt shown in the second PDF file (yours could however be slightly different to this one.) The only thing connected to the battery negative terminal should be one end of the shunt. All the common negative leads (including the earth connection) should be connected to the other side of the shunt. If anything is connected between the battery and the shunt then the current flowing in that lead will not be measured by your monitor. As a result of that the monitor will not be showing the true charge or discharge currents and hence the SOC of your battery. The monitor measures the battery current by measuring the very small voltage across the shunt. That is another way of saying that if not all the battery current is going through that shunt then the monitor will be next to useless.

As well as the battery capacity that Steve mentioned there is a setting for the Peukert's constant. From your comment "Too technical for me so I will pass both comments onto the auto elec," I would say you do not understand that term. Also the link above did not work, Peukert's constant - (it appears I have it working this time.) Let me try to explain it in simpler terms. A battery is not 100% efficient like everything else in this life. you have to put more current into the battery than you will get out of it. As well as that, the faster you discharge the battery the less you will get out of it. Another way of saying that is that you will get less out of the battery if you discharge it drawing high currents than if you discharge it at lower currents. Many years ago a bloke by the name of Peukert worked out the law that governs the difference in battery life with different discharge rates. This law results in different constants that have to be applied for different types of battery. All good monitors (including the BM-1) have the ability to set this constant within their programme. To be able to set the monitor up correctly you will have to find out what the constant is for your battery, your battery supplier should be able to find it out for you.

Solo Steve · Senior Member

PeterD your explanation of peurket's constant is concise and exactly as I understand it. My info suggests " For a leadacid battery however, the value of k is typically between 1.1 and 1.3. It generally ranges from 1.05 - 1.15 for VRSLAB AGM batteries, 1.1-1.25 for gel, and 1.2-1.6 for flooded batteries". However, I can't find any reference in my manual nor in the download that you mentioned on how to change it. Since the constant is an exponent in the peurket equations a large difference in value may indeed be significant. I still recon though that it is most likely that the charging voltage is incorrect or the shunt has been wrongly wired. If the later was rewired in parallel rather than in series with the batteries it would either be stuffed or wildly inaccurate. Am I correct in assuming this. I must say that I have no qualification in electronics but just interested in analysing this problem and value your experience. I know we have probably gone too far for goldcaster's needs however, the opinion of the autoelectrician will be interesting.

Steve

goldcoaster · Senior Member

Sorry I haven't posted earlier but I still have not seen the autoelec,he asked me if I wasn't in a hurry could I hold of till next week. Now I have more info to show him, thanks again .