Checking SOC for LifePo4?
Submitted: Saturday, Jan 04, 2020 at 10:15
ThreadID:
139503
Views:
10506
Replies:
8
FollowUps:
18
This Thread has been Archived
Member - silkwood
I am looking into options for checking the state of charge of my lithium batteries. I am running an Enerdrive dc-dc/mppt 40A, but this only gives current (pardon the pun) volts and amps.
From what I have read, the choice is in-out counting, which is imprecise and not user friendly, or a "coulomb counter", utilising a shunt.
The counters available from the major brands (including Enerdrive) are in the hundreds of dollars and I cannot get anyone to point out what they have over a more basic unit using the same shunt system that can be had for under $100. It seems excessive to pay over $300 for a meter to give you a readout, but what would I know? (not a lot, it appears??)
Can anyone clarify the issue and/or provide alternative solutions?
Cheers,
Mark
Reply By: Frank P (NSW) - Saturday, Jan 04, 2020 at 10:42
Saturday, Jan 04, 2020 at 10:42
Mark,
It may be that the more expensive ones have many more settings to make them more accurate. The BEP coulomb counter in my
Kimberley Karavan has, from memory, 21 settings. Many of those are pertinent only to lead-acid batteries, but they are there nonetheless and have to be paid for.
I expect the maximum current capacity of the shunt may affect price - larger ones more expensive.
I've had no experience with cheaper ones but I can tell you that quality of cabling and connections is crucial to an accurate result. In early models like
mine the
Kimberley wiring was woeful. I have to reset
mine quite regularly to correct a cumulative error that I am unable to fix. (It doesn't see all the amps going in, but a tong meter shows the amps are indeed getting to the battery. I've given up on tracing the fault and have learned to manage it.)
Cheers
AnswerID:
629325
Follow Up By: Keith B2 - Saturday, Jan 04, 2020 at 12:15
Saturday, Jan 04, 2020 at 12:15
The shunt goes into the earth line immediately after the battery. If any earth connection is made upstream of the shunt, it will result in errors on the meter. The only lead coming off the negative side of the battery should be to the shunt, as I discovered at my cost.
Keith
FollowupID:
904143
Follow Up By: RMD - Monday, Jan 06, 2020 at 22:20
Monday, Jan 06, 2020 at 22:20
Frank P
I would have though the size or connections wouldn't have a detrimental effect because ALL the current being measured is going through the shunt and so even if there is resistive wiring or connection it still reads what passes through. As others mentioned, small drains of other devices not
well placed would stuff up the count and create cumulative errors requiring a reset.
FollowupID:
904242
Follow Up By: Frank P (NSW) - Monday, Jan 06, 2020 at 23:39
Monday, Jan 06, 2020 at 23:39
I have no answer, RMD. I just know that I have an issue that I cannot fix and that the wiring and some connections are a dog's breakfast.
Cheers
FollowupID:
904248
Reply By: Idler Chris - Saturday, Jan 04, 2020 at 10:46
Saturday, Jan 04, 2020 at 10:46
What brand of battery do you have? My lithium battery (EV-Power) comes with an app that connects by bluetooth and gives the SOC and rate of charge/discharge.
Chris
AnswerID:
629326
Follow Up By: Member - silkwood - Saturday, Jan 04, 2020 at 14:44
Saturday, Jan 04, 2020 at 14:44
Mine doesn't...
FollowupID:
904147
Reply By: Bob Y. - Qld - Saturday, Jan 04, 2020 at 15:08
Saturday, Jan 04, 2020 at 15:08
I also have an Enerdrive dc2dc 40A charger, Mark, servicing 2 of el cheapo lithium 120Ah batteries and have been undecided about a battery meter after reading, on EO I think, that my preferred choice did not “read” the lithium’s performance adequately. Any further investigations were cut short by a 5 week trip up the Canning.
There seems to be quite a number of units, available from various outlets, that lay claim to being lithium friendly, but which one?
I do have a BM-1, from my previous lead acid set up, but haven’t tried it with the lithium’s.
Bob
AnswerID:
629332
Follow Up By: Allan B (Sunshine Coast) - Saturday, Jan 04, 2020 at 16:48
Saturday, Jan 04, 2020 at 16:48
.
Bob, I see no reason why the BM-1 would not serve on the lithium batteries. It is after all just measuring the electrical voltage and current. It doesn't know what sort of battery is connected. Just needs calibrating to the lithium profile in order to provide sensible readout.
Do your load accessories need to be "lithium friendly"?
Methinks those outlets that proclaim to have lithium friendly products are hoping that customers will conclude that non-endorsed products are not suitable for lithium.
FollowupID:
904153
Follow Up By: Allan B (Sunshine Coast) - Saturday, Jan 04, 2020 at 19:00
Saturday, Jan 04, 2020 at 19:00
.
Bob, I have researched the BM-1 more thoroughly now and confirm my view that it will support Lithium as
well as AGM or any lead-acid. It is a fairly simple device that equates Ah in to Ah out to determine battery SOC with functions of volts etc and settable alarm points.
There is now a model "BM-1 Li" aimed obviously for the Lithium market but from what I can see there is no difference except the logo and price. The BM-1 is a good product but I have no reason to believe that the manufacturer is not above using some marketing ploys. In fact Marine Tech advertises the BM-1 Li with a description that includes "AGM batteries".
FollowupID:
904157
Follow Up By: Bob Y. - Qld - Saturday, Jan 04, 2020 at 19:47
Saturday, Jan 04, 2020 at 19:47
Thanks for that info, Allan.
If I can drag myself out of the aircon tomorrow, I should fit the unit, as still have the shunt in position. Think my enthusiasm is down the shed too, along with my tools.
Trust you have managed to get through the festive season unscathed, and ready for some remote trips later on.
Bob
FollowupID:
904160
Follow Up By: Allan B (Sunshine Coast) - Saturday, Jan 04, 2020 at 20:09
Saturday, Jan 04, 2020 at 20:09
.
Well Bob, it can do no harm as the only component in the path is the shunt and that is passive.
I will find your observations interesting.
FollowupID:
904161
Follow Up By: Sand Man (SA) - Sunday, Jan 05, 2020 at 11:39
Sunday, Jan 05, 2020 at 11:39
The one problem with the BM-1 is that it is specifically designed for AGM type batteries and as such, will reflect a low SOC
well before the level you can draw down to with a Lithium battery.
I assume that is why a new BM-1 Li has been released, so it can be configured for Lithium characteristics.
I also used a BM-1, which was an excellent battery monitor for my previous AGM batteries.
When I installed a 120Ah Lithium battery to reduce the weight of two 100Ah Fullriver AGM’s, I upgraded to a Victron BMV-712 monitor that supports lithium batteries and reflects the lower level you can draw the lithium down to without damaging it, while giving an accurate SOC percentage.
FollowupID:
904178
Reply By: HKB Electronics - Saturday, Jan 04, 2020 at 15:10
Saturday, Jan 04, 2020 at 15:10
You can only use voltage a very rough indication of the SOC of a Lithium battery as the voltage remains very constant until the battery is near 0% SOC.
The battery management systems such as the Enerdrive EPRO unit monitor Ah in and out of the battery. It will show you how many Ah are in the the battery, the charge discharge rate and how long till the battery is discharge at the current discharge rate. It will automatically reset the battery Ah to a 100% when you fully charge the battery. You can program in the battery Ah capacity and it can then display SOC of the battery using Ah in and out of the battery which again is auto reset when battery is fully charged to correct gradual inaccuracies that occur after repeated charge discharge cycles where the battery is not fully charged.
It also gives stats, you can set alarm values ie operate alarm relays for under voltage, over voltage and can flash the display
orange if certain alarms occur, ie the SOC gets to low. It can be used to control chargers or protective devices, ie under voltage protection. Will display how long till battery reaches 0% SOC at the current discharge rate etc, and can display the battery temperature if required.
The standard shunt will also handle 500A if required.
AnswerID:
629333
Follow Up By: Allan B (Sunshine Coast) - Sunday, Jan 05, 2020 at 12:39
Sunday, Jan 05, 2020 at 12:39
.
Blimey Leigh, can the Enerdrive EPRO also
cook a steak with all the trimmings? lol
FollowupID:
904183
Reply By: Rocket Rod - Saturday, Jan 04, 2020 at 15:26
Saturday, Jan 04, 2020 at 15:26
I've just purchase but yet to receive this one
https://www.amptron.com.au/100a-battery-coulometer-monitor-with-shunt.html
Just like you I didn't want to spend a fortune on a meter and happen to stumble on this unit. I can't tell you if it's any good or not as yet to receive it.
AnswerID:
629334
Follow Up By: Frank P (NSW) - Saturday, Jan 04, 2020 at 16:16
Saturday, Jan 04, 2020 at 16:16
Thanks for that link, RR, I've just ordered the 350 amp version for the same price.
Cheers
FollowupID:
904148
Follow Up By: Member - silkwood - Saturday, Jan 04, 2020 at 16:16
Saturday, Jan 04, 2020 at 16:16
Yes, just saw this one myself. It appears to be very similar to many of the budget ($50-$70) units available, but at this price it may be worth paying a little extra to get it from a reasonably reputable supplier.
There's every chance it may be simply rebranded, of course.
Cheers,
Mark
FollowupID:
904149
Follow Up By: Member - silkwood - Sunday, Jan 05, 2020 at 11:28
Sunday, Jan 05, 2020 at 11:28
That one looks interesting, be good to get some direct
feedback from the user. Any idea who has this fitted?
Cheers,
Mark
FollowupID:
904177
Follow Up By: Member - Bigfish - Sunday, Jan 05, 2020 at 12:17
Sunday, Jan 05, 2020 at 12:17
Sorry
Silkwood, I cannot remember. I am pretty sure it was on a Lithium battery thread within the last 2 months.
FollowupID:
904181
Follow Up By: SCUBADOO - Monday, Jan 06, 2020 at 06:13
Monday, Jan 06, 2020 at 06:13
It may have been me Mark.
Our battery for the last 5 years has been a single 4 cell Sinopoly 300Ah LiFePO4 pack that both feeds the house and starts the truck.
I have been running a $300 Votronic battery monitor for the last 5 years of full-time travel and am more than happy with the device. I previously ran a BEP monitor for years with no issues.
About 8 months ago I decided to add a $40 Juntek to the mix and it has performed more than admirably so far displaying ALL the relevant information without button pushing on a very easy to read screen.
The huge advantage for me is the wireless option between the shunt and head unit that makes installation a breeze. I purchased 2 units and now have an extra display on the dash of our motorhome operating from the same shunt sender.
The Votronic and Juntek shunts are wired in series in the battery box.
10/10 for me.
Can I post a link to our NZ
forum here? Lots of follow up info for anyone interested. First post is
mine.
https://nzmotorhome.co.nz/forum/viewtopic.php?f=55&t=19169
Neville
FollowupID:
904198
Follow Up By: Member - silkwood - Monday, Jan 06, 2020 at 09:45
Monday, Jan 06, 2020 at 09:45
Thanks Neville, good information. So, with the "drift" in indicated SOC, I am presuming I can use the full indication on my Enerdive dc-dc to select when to reset the Juntek?
You say you turn it off every night. Is the display powered by the usb connection? If you use only the wireless, what powers the display (why turn it off at night)?
Edit: should have read the entire NZ post. It can be powered from the shunt or from any usb outlet, yes? With such a small current draw, why turn it off (unless left unused for weeks)?
Cheers,
Mark
FollowupID:
904209
Follow Up By: SCUBADOO - Wednesday, Jan 08, 2020 at 11:24
Wednesday, Jan 08, 2020 at 11:24
12V powered from the same circuit as our USB outlets, router etc. I turn the head unit off each night because it is rather
bright even at the lowest setting.
It does not affect any readings since all calculations are performed at the shunt module which remains powered 24/7.
The display reads all the relevant data within half a second of reconnection.
FollowupID:
904329
Reply By: malken - Saturday, Jan 04, 2020 at 21:44
Reply By: Peter_n_Margaret - Sunday, Jan 05, 2020 at 14:42
Sunday, Jan 05, 2020 at 14:42
I am still using a 15 year old PWM Plasmatronics PL60 solar controller that I installed when I built the OKA.
It records both power used (via 2 shunts and direct from the controller) as
well as power in (via solar and by the shunts including from the alternator) and uses that information to calculate a current state of charge.
It stores that information at the end of each day (along with other information such as daily power in and out) in a file for 30 days.
From time to time it resets the SOC to 100% when the battery goes into float mode to cancel out any cumulative errors that creep in.
All parameters are user settable so it can also do what it does with any battery size or type, including Lithium.
Cheers,
Peter
OKA196 motorhome
AnswerID:
629343
Reply By: Dave B18 - Sunday, Jan 05, 2020 at 19:51