Battery monitor shunt, Lithium.

[Neeves]

Still it is a shame in an RV to install lithium batteries and not be able to use high draw convenience items, but as always this is the owner’s decision.

Its only a shame to you - the owner maybe perfectly happy. If he uses a recognised camp ground - he can use as many convenience items as he wants - without the need for lithium at all.

Many would say its a shame to have a well kitted out modern yacht - using lead - but that's what most people buy.

Jonathan

 

[noelex]

I'd have put it another way:

Shunts, brand name, high capacity shunts - are expensive - especially if you buy one of 350amp when you only need 100amp.

Shunts are not expensive.

Here is the first Google hit. A 500A name brand Victron shunt for €34.

If the rest of the system is capable of delivering more than 100A, it is shame to limit the output given the small price difference between a 100A and larger capacity shunt, especially with a lithium system.

 

[Kelpie]

It is difficult to replicate cooking with gas using electric - as many Chinese restaurants will attest.

I've yet to meet anybody who has swapped from gas to induction and regretted it.
Two houses ago we fitted a gas range, thought it was great. Then built a little self catering cottage and fitted induction for ease of cleaning and safety. Tried it out and what a revelation. Immediately installed induction in our own house too, followed by induction on the boat.

About the only thing I miss is that you can't roast peppers over an induction hob. But the speed, power, safety, cleanliness, running costs, and lack of heat more than make up for that.

 

[noelex]

Its only a shame to you - the owner maybe perfectly happy. If he uses a recognised camp ground - he can use as many convenience items as he wants - without the need for lithium at all.

If you have an RV that is plugged into a campground every night, there is little point having anything more than a very basic DC system, but most cruising yachts benefit from more independence and perhaps this explains our different priorities.

 

[William_H]

The instruction for installation of our shunt and meter is to instal a 0.3mm copper wire from the positive pole on the battery to a specific terminal on the shunt. The distance is maybe 0.5m. I was surprised that the wire was not supplied.
Jonathan

I can only suggest that instructions are wrong technically. I imagine you mean 2 wires one on a specific terminal of the shunt one to the positive terminal of the battery. The 2 wires going to meter or control. As I explained before any resistance in the main battery cable and terminals will add to the resistance of the shunt. (which is very low but specific) So possibly incurring an error in measurement. Note in the picture of the shunt there are 2 small phillips head screws in the side of the shunt. These are what should be used as connectors to the meter or control box. Not via the big lugs ol'will

 

[Neeves]

I can only suggest that instructions are wrong technically. I imagine you mean 2 wires one on a specific terminal of the shunt one to the positive terminal of the battery. The 2 wires going to meter or control. As I explained before any resistance in the main battery cable and terminals will add to the resistance of the shunt. (which is very low but specific) So possibly incurring an error in measurement. Note in the picture of the shunt there are 2 small phillips head screws in the side of the shunt. These are what should be used as connectors to the meter or control box. Not via the big lugs ol'will

I don't think the instructions are wrong, my summary is at fault.

Yes - the big lugs - one is connected direct to the battery negative, the other is connected direct to a negative bus bar that then distributes to those units needing, or producing, 12v power. The big lugs are specific, one for input, one for out.

The meter, on our unit, is connected via a dedicated shielded cable and plug and socket.

The probe or sensor is connected to the main positive battery pole (along with the heavy duty cable to take the positive to a positive bus bar). The sensor is the only connection to the positive of the battery. The probe or sensor I assume is connected to the meter within the shunt but has its own connectors on the shunt. The sensor/shunt connectors on the shunt are various - depends how your shunt is orientated and you can use the most convenient.

Currently I have almost everything installed but am by passing the shunt and meter.

I need to decide what the probe/sensor will be - a dedicated device/cable from an automotive/electronic retail outlet or ... the 0.3mm, OD of wire, cable. I also need to make up the cables that fit on the shunt, from battery and to bus bar. Something to do this evening.

Jonathan

 

[Neeves]

Shunts are not expensive.

Here is the first Google hit. A 500A name brand Victron shunt for €34.

If the rest of the system is capable of delivering more than 100A, it is shame to limit the output given the small price difference between a 100A and larger capacity shunt, especially with a lithium system.


View attachment 166200

I was ambiguous, my mistake.

The expense is buying the 2 units, meter and shunt, and I had not envisaged buying one from one source and meter from another - as all the meters I see come with a variety of differently rated shunts (the meter is 'common' which you can match to shunts of different specs).

I think the NASA Lithium package costs approx Stg127+ freight. I assume that the Victron meter + shunt costs a bit more.

No, not expensive but if you are investing in Lithium all the bits and pieces, none of which are options, add up (on top of the battery) - the total cost of a Lithium battery bank is not cheap (compared to Lead) - but all the costs tends to be lost in the string of advantages.

Jonathan

edit

The Victron BMV 700 'looks' similar to our mon. The Victron one in Oz costs Stg120, plus local delivery charges, ours costs Stg 34. delivered. Ours is a 100 amp shunt, limit of 150 amp (could have paid extra for the 350 amp shunt)

That difference, to me, is ..... expensive. Though for others its chicken feed

Now - ours might not work - no issues, guaranteed refund, ours might not last (our risk - but at the cost differential - worth a punt).

Ours was bought through Temu. The Victron unit available through a local (to Oz) distributor (the BMV 700 is currently on special).

Both units look like and have the same spec as our Xantrex unit on Josepheline (about 25 year old) - so pretty old technology.

Time will tell.

 

[Kelpie]

No, not expensive but if you are investing in Lithium all the bits and pieces, none of which are options, add up (on top of the battery) - the total cost of a Lithium battery bank is not cheap (compared to Lead) - but all the costs tends to be lost in the string of advantages.

Jonathan

You don't need every bell and whistle.
For the first 18 months after installing lithium, I had no battery monitor at all- I just checked the BMS via a phone app.

 

[Baggywrinkle]

There is one other good reason for replacing gas with electric ...

 

[Neeves]

There is one other good reason for replacing gas with electric ...

You are encouraging some to mention that Lithium might compare quite well as an accelerant....

Jonathan

 

[Neeves]

You don't need every bell and whistle.
For the first 18 months after installing lithium, I had no battery monitor at all- I just checked the BMS via a phone app.

I'll bite - why then did you instal a battery mon?

I can think of other things to spend stg100 - first up, some malt whisky.

Jonathan.

 

[Gsailor]

There is one other good reason for replacing gas with electric ...

It took them ages to get that boat to blow up. They couldn’t get the gas and air mix correct IIRC from seeing the video years ago.

Still, I have always preferred meths stoves - even for camping outdoors.

 

[Baggywrinkle]

It took them ages to get that boat to blow up. They couldn’t get the gas and air mix correct IIRC from seeing the video years ago.

Still, I have always preferred meths stoves - even for camping outdoors.

It was just done deliberately for dramatic effect, a large explosion is one possible outcome with gas on board - and it has happened to people - not very often - but it really depends on your personal approach to risk management and thoughts on probability.

Carbon monoxide poisoning and propane being an asphyxiating gas are also areas where Li and Electric score safety points.

I still stand by the assertion that the inherent dangers of gas on board are a reasonable reason to switch to induction cooking.

 

[Gsailor]

It was just done deliberately for dramatic effect, a large explosion is one possible outcome with gas on board - and it has happened to people - not very often - but it really depends on your personal approach to risk management and thoughts on probability.

Carbon monoxide poisoning and propane being an asphyxiating gas are also areas where Li and Electric score safety points.

I still stand by the assertion that the inherent dangers of gas on board are a reasonable reason to switch to induction cooking.

I have always removed gas from any boat I bought because of the safety reasons you state and replaced with meths. If I could have gone induction route I would have.

 

[Pete7]

I have always removed gas from any boat I bought because of the safety reasons you state and replaced with meths. If I could have gone induction route I would have.

If only Dometic hadn't got involved in alcohol stoves

 

[Baggywrinkle]

You are encouraging some to mention that Lithium might compare quite well as an accelerant....

Jonathan

Lithium iron phosphate (LiFePO4 used in boat batteries) is a different chemistry and doesn't release it's own oxygen to cause catastrophic thermal runaway - they will usually swell, split, and vent nasty gasses but a fire is unlikely unless you poke it twice with a very big pointy metal stick ...

Todays test was constructed after reading through countless testing and specifications for LiFePO4 batteries.

I have found that many of them specify a safety parameter for details such as overcharging, over discharging, crushing, and so on, however, none of them give any detail with respect to puncturing.

In this video, I took a heavy bar that had a spike on one end, and punctured an aluminum-cased LiFePO4 cell that I am doing other testing on.

The result after the first puncture was simply venting of vapor, but I believe that when I made the second puncture, there was a spark produced that caused this electrolyte vapor to ignite, leading to the flame ball observed in the video.

In a video coming soon, we plan to compare this to the type of fire that would be created with other battery chemistries, such as Li-Ion that contain cobalt. Cobalt within batteries allows the batteries to have a thermal runaway which cannot be extinguished due to the chemicals providing their own oxygen.

Later beyond

If we take a look at the chemical makeup of a LiFePO4 cell, we will observe that there are more chemicals inside of a battery aside from JUST LiFePO4.

Take a look of this info I copied from Wikipedia: Source: https://en.wikipedia.org/wiki/Lithium...
Cathode composition (weight)
90% C-LiFePO4, grade Phos-Dev-12
5% carbon EBN-10-10 (superior graphite)
5% polyvinylidene fluoride (PVDF)
Electrolyte: ethylene carbonate–dimethyl carbonate (EC–DMC) 1–1 lithium perchlorate (LiClO4)
1MAnode: graphite or hard carbon with intercalated metallic lithium

If you take note of the electrolyte, and further research dimethyl carbonate, you fill find that this is flammable.

I don't think LiFePO4 is any more dangerous than Lead Acid which can also explode, vent nasty gasses, and overheat.

 

[B27]

....



I don't think LiFePO4 is any more dangerous than Lead Acid which can also explode, vent nasty gasses, and overheat.

I think the biggest dangers of Lifepo4 on boats might be the stored energy and high currents possible?
Opportunities for amateur wiring to set fire to alternators, melt insulation and generally overload stuff which was just about adequate with lead?
It's encouraging some people to meddle with high current electrics which have the capability to do damage, and some of these people don't seem to have a terribly good grasp of basic electrical theory or what their little boxes of electronics actually do.

A 100Ah battery, whatever its chemistry, holds over a kWh of energy.
That's a lot of heat, enough to do a lot of damage or start a real fire.

 

[Baggywrinkle]

I think the biggest dangers of Lifepo4 on boats might be the stored energy and high currents possible?
Opportunities for amateur wiring to set fire to alternators, melt insulation and generally overload stuff which was just about adequate with lead?
It's encouraging some people to meddle with high current electrics which have the capability to do damage, and some of these people don't seem to have a terribly good grasp of basic electrical theory or what their little boxes of electronics actually do.

A 100Ah battery, whatever its chemistry, holds over a kWh of energy.
That's a lot of heat, enough to do a lot of damage or start a real fire.

The world is full of idiots, best thing is that with YouTube and TikTok we get to watch them do stupid things from the safety of our armchairs ... ... this kid is fishing for a Darwin Award.

 

[Neeves]

Lithium iron phosphate (LiFePO4 used in boat batteries) is a different chemistry and doesn't release it's own oxygen to cause catastrophic thermal runaway - they will usually swell, split, and vent nasty gasses but a fire is unlikely unless you poke it twice with a very big pointy metal stick ...

I don't think LiFePO4 is any more dangerous than Lead Acid which can also explode, vent nasty gasses, and overheat.

The trouble is the press rightly points out that Lithium is a major source of fires but omits to define Lithium, The public reads, or hears, Lithium and assumes all Lithium batteries are the same.

Jonathan

 

[B27]

Our shunt is 100 amp, max of 150 amp (the alternative was 350 amp which seems a bit excessive). The shunt is brass (a yellow metal with matching brass washers and spring washer). The shunt itself is three, parallel, heavy duty, silver coloured, wires. I have not measured them but they could be 3mm OD and maybe 40mm long. The whole lot is housed in an acrylic base. The negative of the shunt will be connected to a heavy duty brass (more yellow metal) bus bar with each ancillary cable to its own pole. The positive from the battery simply goes to positive circuits - no contact, see next sentence, with the shunt. There is a very low duty wire, 0.3mm, from the positive terminal of the battery to a separate terminal on the shunt. There is only one negative cable on the battery pole, it goes direct to the shunt and the cable will be a max of 200mm long, the cable from the shunt to the bus bar will be 50mm - 100mm. There are 5 negative cables on the bus bar with poles for more.

I'm not sure but all the poles seem to be stainless, including the battery. They are all 'stainless' coloured.

The eye connectors on the ends of the cables are all, sort of, mattish grey colour, standard AFAIK eye connectors. The eye connectors will interface directly with the bus bar, no washers,

The shunt and bus bar are located with all the other electrical kit, inverter, B2B, circuit breakers, isolator switch, water meter etc., and eventually this coulomb meter The shunt, the bus bar and the battery terminals are in full view when you open the door - I'm wondering if the battery and the bus bar should have covers ....... ? or I think they should but what? ..... acrylic boxes as covers.....?

There is no ventilation, the only 'holes' are where cables enter or exit - I'm thinking of a fan, my big computer fan.

But a fan, which by all accounts will be welcomed by the B2B and inverter , is no use if it simply stirs up warm air - I need to think how to introduce fresh air - which will be difficult in an Australian summer (maybe move to somewhere geographically colder . ).

I'd post a photo - but I have not taken any yet.

I have wondered why it is called a shunt.

Thank you all for your comments.

Jonathan

I assume your battery monitor is something like this:
Battery Monitor 50A/100A/350A VOLT Capacity Tester Voltmeter Ammeter DC 80V | eBay
As well as the wires going from the actual shunt resistance to the meter head, there seems to be an isolated terminal for a sense wire from the +ve terminal of the battery. This would go to the meter head unit via the same screened multi-way cable as the current sense lines. It probably powers the meter head as well as allowing the head unit to measure the battery volts.

That +ve wire should have a fuse in it near the battery.



The name 'shunt' for a parallel current path is long established, it's probably related to a railway shunting yard where you have lots of parallel tracks to sort goods wagons?
Rather than the colloquial term for a collision between vehicles.
As well as being a term for a current sensor, it can be an adjective for any component in parallel.