Battery monitor shows 91% to 53% in couple of days.

[nostalgia]

Hi all, had my van on charge for the last few months with a battery monitor on my phone, had to put the car in for repair so used the van Monday morning for work and again this morning, checked the battery dinner time to find it had gone down from 91% to about 53% in just a couple of days. The drive to work is 60 miles round trip so would have thought it should have kept it charged.
your thoughts are most welcome Phil

 

[Ads_Essex]

Hi all, had my van on charge for the last few months with a battery monitor on my phone, had to put the car in for repair so used the van Monday morning for work and again this morning, checked the battery dinner time to find it had gone down from 91% to about 53% in just a couple of days. The drive to work is 60 miles round trip so would have thought it should have kept it charged.
your thoughts are most welcome Phil

My BM-2 often shows my battery at 50%, sometimes lower, and it starts fine.
What monitor and application are you using?
I ask as most BM’s are not very adept to giving a true reading of a smart-alternator type battery.

 

[nostalgia]

Hi it’s a ctek

 

[Dellmassive]

I had 3 of the CTEK battery monitors and got rid of them for just that reason...... the readings were all over the place. (I show it in the thread)

As above ( @Ads_Essex ), swap it out for a BM2.... or other..

Battery Monitoring -- How I Done It --

Battery Monitoring -- How I Done It -- Part #1 Battery monitoring is a very important part of your 12v system . . . . whether its just the vans starter battery or your leisure setup keeping an eye on the power in your battery bank will keep you from breaking down and make sure your weekends...

www.t6forum.com

.

 

[nostalgia]

So which one is the best to get.
So what’s the big difference between the old alternator and the new smart ones and what battery readings should concern me.

 

[hoggle]

I have the BM2 monitors that were recommended by @Dellmassive on both my batteries. They work great and have never given me any strange readings.

 

[Deleted Member]

Also got 2x BM2 monitors as per Dell’s recommendation.

 

[Skyliner33]

My BM2 on my starter battery shows a similar drop over a couple of days. Starts fine also, so Im planning to take it off to stop me worrying lol.

 

[Higgidav]

I ignore the % reading and just go with the voltage as it states low voltage most of the time. Having said that my van can sit for 3 to 4 weeks before reaching 12.0v at which point I plug in the charger.

 

[Dellmassive]

The important thing to remember is to not get fixated on the % that battery monitors can can show.

due to the nature of the start/stop system the readings fluctuate wildly . .

also the Firmware inside these devices is set for a wide selection of batteries - built mostly Standard Lead Acid battery's (which will slue the readouts when on a AGM battery as they have higher resting voltage)

what is important is the history logging - Which the CTEK and BM2 do.


in this example you can see a very low battery being charged (mains charger) . . it starts LOW at about 10.2v and gets charged to 13.2v in the end.



in this example you can can see the engine and alternator charging the battery when charging . . .




in this example you can see a Lifepo4 being rapidly discharged by a test. . . .





..


so using the history log you can see the effect of the change in voltage over time . . so whether the battery is going flat or you have charging issues etc these chart will give you an indication on whats going on.


Having said all that they are still very usefully in standard mode . . .

for a standard T6 we have notice that above 12.0v is ok - normal. (voltage reading at rest with van off)

11.9v is low and the van will need charging. (voltage reading at rest with van off)




if you get more than one BM2 - say one on the starter and one on the AUX battery . . .

you can use the BM3 APP with can display up to 4x battery's simultaneously . .





Also the BM2 is the closest to the CTEK is looks and usage - so it will be familiar to you.



Bm2 : Battery Monitor BM2 device for car's 12V Battery/leisure battery tester Compatible with Android iOS and Ipad with bluetooth 4.0 and above.: Amazon.co.uk: Car & Motorbike




I've tried all the others . . .

The BM2 is the currently best, most accurate easy to use, low power, cheapest voltage datalogger available - IHMO

its been around for a few years now . . . so im expecting copy's / cloans and a possible new version with more features?

only time will tell.

 

[Loz]

Hi it’s a ctek

My 2 do the same, there seems to be a timer element to the algorithm that assumes the SOC will drop "an amount" over time and this gets more and more inaccurate as time goes on between charge. With the long coved layup ours has had this has got worse.
Only a very long charge seems to reset it.

 

[Dellmassive]

FYI:

here is a comparison with the CTEK and BM2 battery monitors.

 

[Dellmassive]

My 2 do the same, there seems to be a timer element to the algorithm that assumes the SOC will drop "an amount" over time and this gets more and more inaccurate as time goes on between charge. With the long coved layup ours has had this has got worse.
Only a very long charge seems to reset it.

@Loz i think me and @mmi bumped into that hurdle previously.

i even had 2x CTEK units on the one battery to try and work out what was going on . . . which is annoying as i have 3x CTEK battery monitors now. ( and they not cheap !!) (I've kept them hoping that a new FW or APP V.xxx would be released to fix the issues, . . . maybe its just not going to happen? - time to sell them on?)

as you say we come to the conclusion that the CTEK FW / Algorithm was trying to be too cleaver and would end up drifting massively out of whack.

this was verified with a second BM2 unit on the same battery. . . but also the Plug on 12v battery tester.

so in my case the end result was to replace the CTEK units for BM2 which is a shame as i love the CTEK range of kit, especially the chargers.

it just seems that the FW needs fixing before they are reliable . . . but i dont know if the APP is able to push a new FW to the unit?

anyway moving forwards you can now get 2x BM2`s for the price of one CTEK.