Battery Monitoring System: What do I need?

johnny5

New Member
I'm beginning my first van build/electrical system, and now looking at a battery monitoring system. I was looking at this bayite monitoring system (https://www.amazon.com/gp/product/B013PKYILS/ref=ox_sc_act_title_4?smid=A2EFSDTWMPHWEA&psc=1), but as you can see, one of the pictures shows a schematic with 4 monitors. I need 4 monitors, really? Or is that an optional setup? What exactly do I need?

Here's the system I will have:

2 100a 12v lithium batteries
2 100w renogy solar panels
Renogy 50a DC to DC MPPT Charger
1000w pure sine inverter

I'm looking at mostly replicating Will's schematic here:

https://www.mobile-solarpower.com/uploads/1/2/9/6/12964626/122-fgood_2_orig.jpg
 

svetz

Works in theory! Practice? That's something else
Everyone's different, mine probably more so as there are 4 independent battery/inverters working together (Enphase Ensemble).

For Battery monitoring, there are a few things I want to know and a few things to alert on (I send text messages or emails):
  • temperature (alert on too hot or too cold (this is just for emergency if something goes wrong so I can flip them off)
  • Grid State (Alert when off-grid, although technically this comes from the ATS, not the battery)
  • Charge Rate, time to fully charged at the current rate
  • Discharge Rate, time to fully discharged at the current rate
  • SoC
  • Cell Equalization events
I also wrote a little cellphone app (foghorn) to get key data at a glance for all the systems combined (for hurricanes, so I can see how much time I have left when the power is out, or how long it'll take solar to charge them). The idea is I can turn things off at the load center until the current discharge rate decreases to an acceptable level.

I don't typically graph data, but the Enlighten software that comes with my system (Enphase) does and it's been useful. For example, when the daylight savings time "event" happened this year my batteries went a little nutso, some discharging into others even though the overall SoC remained constant:

1620557405263.png

They got it straightened out pretty quick.
 
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mikefitz

Solar Addict
one of the pictures shows a schematic with 4 monitors. I need 4 monitors, really? Or is that an optional setup? What exactly do I need?
This monitor can only record 'one way' current ind is not ideal fro the small leisure system in a van.
Things you need to know, how much energy in the battery, the battery volts, and how much current is going in or out of the battery.
top of the range, Victron BMV712 or Victron smart shunt
Economy, AiLI with the 350A shunt,


The shunt for the above units is connected in the path from the battery negative and the negative buss bar, there should be no other connection to the negative battery post, (except the parallel cable connecting the second battery).

Note that the layout you are basing your systen on was put together with existing parts for demonstration. For a safe van installation some modification may be needed.
Fuses or beakers are primarily used to protest cable runs and should be fitted within 6 inches of the power source, the batteries, or where a smaller cable cross section is used at a junction. Unless you are using high quality breakers, Blue Sea/Bussman, fuses will be more reliable. (the no name breakers from Ebay/Amazon are unsafe)
Each element in the system should have its own fuse or breaker, for example in the layout you are following, a safer arrangement would be:

battery - main fuse/breaker- positive cable - positive buss bar, then from the positive buss bar via a suitable rated fuse/breaker to each of the following, the DCC50, the fuse box, the inverter. ( one fuse/breaker per connected element)

Mike
 

hardtop

New Member
I initially thought that I should have some sort of monitor/gauge on my LIFEPO4 battery. I wanted to geek out with charts and graphs and have a live readout always-on display.

But what I did was I ran worst case draw scenarios for a few days including one accidental BMS low voltage shutoff exercise. After learning my draw needs and how much is left in the battery afterwards, I realized I don't need the monitor at all and it would have been money I spent that I didn't need to spend.
 

johnny5

New Member
This monitor can only record 'one way' current ind is not ideal fro the small leisure system in a van.
Things you need to know, how much energy in the battery, the battery volts, and how much current is going in or out of the battery.
top of the range, Victron BMV712 or Victron smart shunt
Economy, AiLI with the 350A shunt,


The shunt for the above units is connected in the path from the battery negative and the negative buss bar, there should be no other connection to the negative battery post, (except the parallel cable connecting the second battery).

Note that the layout you are basing your systen on was put together with existing parts for demonstration. For a safe van installation some modification may be needed.
Fuses or beakers are primarily used to protest cable runs and should be fitted within 6 inches of the power source, the batteries, or where a smaller cable cross section is used at a junction. Unless you are using high quality breakers, Blue Sea/Bussman, fuses will be more reliable. (the no name breakers from Ebay/Amazon are unsafe)
Each element in the system should have its own fuse or breaker, for example in the layout you are following, a safer arrangement would be:

battery - main fuse/breaker- positive cable - positive buss bar, then from the positive buss bar via a suitable rated fuse/breaker to each of the following, the DCC50, the fuse box, the inverter. ( one fuse/breaker per connected element)

Mike
Thanks for your reply Mike, that's very helpful. I think I will give the AiLI monitor a shot.

Your suggestion of a breaker for each connected item makes a lot of sense. I'll pick up a positive bus bar and do just that. 250a bus bar would be appropriate?

So here's a list of the breakers (I'll go with Blue Sea) I think I need. What size breakers would you recommend for my system?

batteries to positive bus bar
positive bus bar to 1000w inverter
positive bus bar to 50a Renogy charger
positive bus bar to DC fuse panel (says it's rated for 100a max)
positive bus bar to alternator (my alt is rated for 100 or 105a)
 
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