Making a cheap BMS ABYC compliant

[tanglewood]

Originally Posted by newhaul

We are a very very small slice of the lifepo4 "drop in" battery market.

Do you think so? I really don't know, and would love to see researched market data. Are you assuming that the majority of drop-ins are RVs?

[s/v Jedi]

Originally Posted by tanglewood

Couldn't this approach still be tricked if one of the 12V batteries has one high cell and one low cell? It's better than nothing, but not fool-proof, and not a full substitute for per-cell monitoring.

Designing a scenario that defeats a safety is always possible. With a BMS just as easy as with the method I described above, especially when a battery internally has cells connected in parallel as well as in series, which means that there is no individual cell monitoring at all.

Best: prismatic LiFePO4 cells only connected in series, with a BMS driving an external latching solenoid (remote battery switch) and providing relay contacts that can be used for audible alarms and shutting down charging sources and loads.

But that said, when using sealed drop-in 12V batteries that contain four cells in series, you can in practice make this work for 24/48V systems with midpoint monitoring. The chances that a low cell offsets a high cell precisely to fool this type of monitoring is astronomically low and it is much better than any system using parallel cells.

I think it is important that manufacturers start copying the marine battery line from Sok with a housing that can be opened for service, providing access to the BMS and cells.

[goboatingnow]

I think in time we will see the emergence of a dedicated marine line of LFP drop in systems. Hopefully these will all be cell monitored so opening the box won’t be needed, warnings and charge control will be integrated etc.

[newhaul]

Originally Posted by tanglewood

Do you think so? I really don't know, and would love to see researched market data. Are you assuming that the majority of drop-ins are RVs?

Actually rv and land based off grid yes . (Let's not forget golf cars ). Just my opinion wrt the advertising market I have seen .

[goboatingnow]

Originally Posted by newhaul

Actually rv and land based off grid yes . (Let's not forget golf cars ). Just my opinion wrt the advertising market I have seen .

I think most market segments see drop ins as the future

[newhaul]

Originally Posted by goboatingnow

I think most market segments see drop ins as the future

Yes agreed the market will and is pushing that but meeting ABYC ISO or any other marine specific standards not so much. We are to small of a market. In 20myears who knows but faster than that I doubt it .

[goboatingnow]

Originally Posted by newhaul

Yes agreed the market will and is pushing that but meeting ABYC ISO or any other marine specific standards not so much. We are to small of a market. In 20myears who knows but faster than that I doubt it .

I don’t agree based on talking to the potential suppliers for example the big players like Victron , msstervolt, Sterling power were keenly aware of the incoming standards and all professed that they would have compliant marine LFp systems.

What the attitude of big brands like Bosch Varta etc is I can’t say but I presume these companies iare all watching this market Segment, Bosch is a big supplier to the marine battery segment so I presume they , will in time , release a suitable marine orientated product line.

Given say the Rcd will be updated in 2023 and will most likely incorporate the new ISO lithium standard that will force builders to be compliant and they in turn will pressurise their supply chains. So i think the timescales will be faster then u think.

[newhaul]

Originally Posted by goboatingnow

I don’t agree based on talking to the potential suppliers for example the big players like Victron , msstervolt, Sterling power were keenly aware of the incoming standards and all professed that they would have compliant marine LFp systems.

What the attitude of big brands like Bosch Varta etc is I can’t say but I presume these companies iare all watching this market Segment, Bosch is a big supplier to the marine battery segment so I presume they , will in time , release a suitable marine orientated product line.

Given say the Rcd will be updated in 2023 and will most likely incorporate the new ISO lithium standard that will force builders to be compliant and they in turn will pressurise their supply chains. So i think the timescales will be faster then u think.

We shall see . BTW bosch is just a label as is varta neither actually manufacture batteries .
Their batteries are made by Johnson controls. And they are not looking to expand their lipo battery market . Rather they are concentrating on improving their AGM lines.

[goboatingnow]

Originally Posted by newhaul

We shall see . BTW bosch is just a label as is varta neither actually manufacture batteries .

Their batteries are made by Johnson controls. And they are not looking to expand their lipo battery market . Rather they are concentrating on improving their AGM lines.

Bosch already commands a big section of the E-bike lithium markets

The batteries are produced and consolidated at the Bosch plant in Miskolc, Hungary. Most of the production and consolidation of the batteries also takes place at the Bosch plant in Miskolc, Hungary, and some in Penang, Malaysia.

All major players active in the marine space will have suitable products

This area is only getting going we wait and see but there no evidence it’s being ignored , exactly the opposit certainly the evidence at METSTRADE was lithium was a big sector and increasing fast as was the interest in electric propulsion.

[RaymondR]

Originally Posted by goboatingnow

Indeed. It you also need an alarm for HVC disconnect even though you hacev100% Soc

High Voltage Disconnect should only disconnect the charging sources, which I believe it does on the Victron smart battery system which has two relays, one for charging sources and a second for loads.

However the Daily BMS I used when I tore down the failed Victron to see what had caused the failure and then decided to salvage some of the good cells does not and this could be a problem.

[tanglewood]

Originally Posted by RaymondR

High Voltage Disconnect should only disconnect the charging sources, which I believe it does on the Victron smart battery system which has two relays, one for charging sources and a second for loads.

However the Daily BMS I used when I tore down the failed Victron to see what had caused the failure and then decided to salvage some of the good cells does not and this could be a problem.

Just curious... which of the two buses do you place an inverter/charger on since they can be both a charge source and a load? In this situation, the whole dual bus approach makes no sense to me, and I focus on controlling individual chargers and individual loads. But in practice, the inverter is the only controllable load. When there is a low battery I autostart a generator. If all else fails, the battery disconnects, which is harsh, but it works.

[newhaul]

Originally Posted by RaymondR

High Voltage Disconnect should only disconnect the charging sources, which I believe it does on the Victron smart battery system which has two relays, one for charging sources and a second for loads.

However the Daily BMS I used when I tore down the failed Victron to see what had caused the failure and then decided to salvage some of the good cells does not and this could be a problem.

The cure for this is getting the Daly unit with dual port legs. One is discharge the other is dedicated charging source .
Only problem is now all power has to go through the battery and not direct to power your watermaker or refrigerator when bank is full

[newhaul]

Originally Posted by tanglewood

Just curious... which of the two buses do you place an inverter/charger on since they can be both a charge source and a load? In this situation, the whole dual bus approach makes no sense to me, and I focus on controlling individual chargers and individual loads. But in practice, the inverter is the only controllable load. When there is a low battery I autostart a generator. If all else fails, the battery disconnects, which is harsh, but it works.

I didn't see a way to do that hence my use of a common port Daly unit.

[RaymondR]

Originally Posted by tanglewood

Just curious... which of the two buses do you place an inverter/charger on since they can be both a charge source and a load? In this situation, the whole dual bus approach makes no sense to me, and I focus on controlling individual chargers and individual loads. But in practice, the inverter is the only controllable load. When there is a low battery I autostart a generator. If all else fails, the battery disconnects, which is harsh, but it works.

At the moment I'm only running a single load on the Victron and it is connected to the Load Relay, I also have only solar panels connected through a solar controller so there is only a single charge source connected to the Charge Relay so there are not really "busses".

[fxykty]

Originally Posted by tanglewood

Just curious... which of the two buses do you place an inverter/charger on since they can be both a charge source and a load? In this situation, the whole dual bus approach makes no sense to me, and I focus on controlling individual chargers and individual loads. But in practice, the inverter is the only controllable load. When there is a low battery I autostart a generator. If all else fails, the battery disconnects, which is harsh, but it works.

Whether an inverter/charger is predominantly a charge source or a load depends on your usage scenario. As liveaboards who are only occasionally connected to shore power and who don’t have a generator, the inverter/charger is so rarely a charger that it makes sense for us to connect it to the load bus.

But regardless of which bus it is connected to, the inverter/charger in the first instance should be controlled directly by the BMS. This enables turning off charging or inverting capability independently and well in advance of an HVC event or LVC event. In normal operation neither of those should ever be seen.