Progress with Lithium Battery Installation

[jzk]

- Retaining a lead battery on the boat is good economy, as all old charging sources (solar, alternator, ...) do not need to be changed.
- Battery chemistry must NEVER be mixes/connected. All power generated (cf. above) should passe through a DC-DC device (and there are many other brands than Victron, not least Sterling-Power who have devices which handle 60A).
- A fully charged LiFePo4 battery has an output potential of 13,2V. So, charging can take place at all voltages between 13,2 and 14,6V. The latter is too close to harmful levels, so never go above 14,4V. The difference between charging with the low voltage and the high voltage is the time it takes to reach full charge (you can squeeze the coulombs faster into the battery when you apply a higher force = higher voltage).

Sorry if above repeat some points stated before in this thread.

I spoke to the owner of Balmar at a recent show. He didn't think mixing battery chemistries was a problem. He recommended running his high output alternator to the LiFePO4 bank with his controller, and then using a blue sea type combiner that connects the start battery to the system when voltage is high enough. I already have a couple renogy DC to DC chargers that I might reverse such that the house is the source and the engine is the battery that gets charged since I will have the alternators charging the house bank. That way, any time either the victron or the alternators are charging the house, the DC-DC will charge the engine batteries which are just regular starting batteries anyway.

Someone talked about why you would want to combine technologies? For one LiFePO4s are not to be used as a starting battery as the starter can pull a whole bunch of amps. Or at least my LiFePO4s are not to be so used.

 

[CapDave]

I spoke to the owner of Balmar at a recent show. He didn't think mixing battery chemistries was a problem. He recommended running his high output alternator to the LiFePO4 bank with his controller, and then using a blue sea type combiner that connects the start battery to the system when voltage is high enough. I already have a couple renogy DC to DC chargers that I might reverse such that the house is the source and the engine is the battery that gets charged since I will have the alternators charging the house bank. That way, any time either the victron or the alternators are charging the house, the DC-DC will charge the engine batteries which are just regular starting batteries anyway.

Someone talked about why you would want to combine technologies? For one LiFePO4s are not to be used as a starting battery as the starter can pull a whole bunch of amps. Or at least my LiFePO4s are not to be so used.

No reason that won't work. But you've "lengthened the chain" for keeping your start battery charged. If your LFP BMS calls for a disconnect that you can't cure, or your DC-DC charger fails, you'll get a few starts and then kaput. That's on top of the usual alternator/regulator etc. failure points.

My boat has 12V start and 24V house. Has some drawbacks, but each engine has a standalone stock 12V alternator that does nothing but charge its own start battery. If those alternators fail, I have a workaround to charge the start batteries from the house set through inverter/shorepower charger.

 

[jzk]

No reason that won't work. But you've "lengthened the chain" for keeping your start battery charged. If your LFP BMS calls for a disconnect that you can't cure, or your DC-DC charger fails, you'll get a few starts and then kaput. That's on top of the usual alternator/regulator etc. failure points.

My boat has 12V start and 24V house. Has some drawbacks, but each engine has a standalone stock 12V alternator that does nothing but charge its own start battery. If those alternators fail, I have a workaround to charge the start batteries from the house set through inverter/shorepower charger.

The point is to use the high output alternators of the engines to charge the much larger house. In a pinch, I could run the generator to use the victron to charge one of the engine banks. Or I could plug a spare charger into the inverter and charge an engine bank.

 

[Second Row]

I disagree that lithium batteries are not simple if talking about Lifepo4 ones which are quite easy to handle. They are just a bit different to lead acid and need to be treated as such, but there’s nothing particularly difficult about it. Problems arise when people don’t take account of the differences and assume they work the same as lead acid batteries, and because of the large amount of energy involved those problems can sometimes be dramatic. More exotic lithium chemistries have to be treated with a lot more caution however and I’d question their use on a boat.

Most of the settings on that charger will work ok for a Lifepo4 battery, with the exception of the 14.8v/13.9v one which is too high on both voltages and the 14.6v/14.2v one which has too high float voltage. You don’t want to charge above 3.65v per cell or 14.6v for the battery. The BMS should cut off charging above this anyway, but it’s not a good idea to rely on that.

Personally I’d use the 14.4v bulk/13.5V float setting, because that will give a 100% charge in bulk with the float voltage sitting just under the typical 13.6v fully charged resting voltage. Lifepo4 batteries don’t really need a float charge as they have minimal self discharge, but if you will be on board using power it will maintain the battery state of charge while connected. If you use a lower float voltage, any power usage will come from the battery not the charger.

In my opinion people overthink the charging cycles thing. You can use a more conservative bulk charge voltage and still get the majority of usable capacity out of them, but I’m not sure it makes a lot of difference in practice. You might get more charge cycles in the long term, but is it actually an issue? If you get 3500 cycles by charging normally that’s nearly 10 years of use if you fully cycle the battery every single day continuously. Are you going to be using them that intensely that the extra cycles are important? I suspect the battery is likely to die of old age before it runs out of cycles.

I don’t think it’s a good idea to use the same charger to charge both types of battery simultaneously however, unless it has properly isolated and independent outputs. Mixing chemistries would seem to me to be inviting problems. I would suggest it would be a better idea to have your mains charger supplying a single battery and then use a DC-DC charger to charge the other one.

On our boat we have the alternator and mains charger going to the starter battery, and a DC-DC charger feeding the lithium battery. That means that the lithium battery can have its own charge profile set, and it also protects the alternator from continuous large charging currents and sudden disconnections.

HI Caius. I am looking at replacing my House PbA with LiFePo4 and using the Orion DC/DC charger to keep the necessary changes to a minimum. My question is about charger location. The manual says to keep the charger as close as possible to the batteries, but other requirements makes the engine bay unsuitable i.e. don't place the charger over the batteries, keep good ventilation, etc. I do not want to put the charger in the quarter berths, which pretty much forces a Nav-Station location. This would require up to 10 foot wiring runs between the batteries and the charger...does this sound appropriate to you? Where did you put yours?

 

[caius]

The reason for having it as close as possible is that cabling losses become significant at 12V for high current applications. You can mitigate that to an extent by using thicker cables. The required cable size goes up significantly with length and current, and after a certain point becomes unwieldy and can be expensive. This is the reason systems with higher DC power requirements tend to use 24V or even 48V - the power loss in the cable is proportional to the square of the current, so by doubling the voltage, you halve the current for any given power and the cable loss is only a quarter of that of the lower voltage.

10 feet is doable, but it depends what current charger you intend to use. If you are going to be using something around 30A, you'd need at least 6 AWG or 14mm^2 to get reasonable loss. You also need to remember that if that's the output current of the charger, the input current will be somewhat higher than that because of charger inefficiencies. You also need to check the terminal sizes on the charger - no point running thick cable if you can't physically connect it. You can calculate the required cable size using Ohm's law, but there are various websites with cable loss calculators that will give you the answer by putting in the figures.

Ours is installed on the outer wall of the battery compartment, which contains both the starting battery and house battery. This puts it inside the cabin, but it's in a location where it's not going to get kicked or otherwise be in the way. The supply and output cables only have to go the distance across the battery box and back, which is pretty short.

 

[Second Row]

The reason for having it as close as possible is that cabling losses become significant at 12V for high current applications. You can mitigate that to an extent by using thicker cables. The required cable size goes up significantly with length and current, and after a certain point becomes unwieldy and can be expensive. This is the reason systems with higher DC power requirements tend to use 24V or even 48V - the power loss in the cable is proportional to the square of the current, so by doubling the voltage, you halve the current for any given power and the cable loss is only a quarter of that of the lower voltage.

10 feet is doable, but it depends what current charger you intend to use. If you are going to be using something around 30A, you'd need at least 6 AWG or 14mm^2 to get reasonable loss. You also need to remember that if that's the output current of the charger, the input current will be somewhat higher than that because of charger inefficiencies. You also need to check the terminal sizes on the charger - no point running thick cable if you can't physically connect it. You can calculate the required cable size using Ohm's law, but there are various websites with cable loss calculators that will give you the answer by putting in the figures.

Ours is installed on the outer wall of the battery compartment, which contains both the starting battery and house battery. This puts it inside the cabin, but it's in a location where it's not going to get kicked or otherwise be in the way. The supply and output cables only have to go the distance across the battery box and back, which is pretty short.

Thanks for the reply, you appear to have a very good handle on this tech, unlike me. Is it correct that your DC-DC charger should be rated at less than your input power sources? My Sentry shore-power charger is rated at 20 amps and my alternator is your typical 55amps...I plan to purchase a Victron 12/12 -18Amp Smart DC-DC charger. Is that the correct option as a 30 amp from Victron is available? I know that this setup will not charge in a hurry (300Amp Hour House battery), but she spends most of her time on shore power anyway.

 

[caius]

The Victron spec sheet for the Orion chargers shows an efficiency of 87% - that means if the output current is 30A, it will be drawing closer to 35A from the input assuming the same voltage. The 18A one would draw about 21A. A 55A alternator should cope fine with a 35A continuous load without overheating, assuming it's well enough ventilated and you aren't trying to charge for long periods at idle engine speed.

If your mains charger is on the start battery and can supply 20A, then that would limit the output of the 30A Orion. I'm not familiar with the Sentry chargers, but assuming they are decent quality they shouldn't be damaged by continuously pulling their rated output - the voltage will be pulled down a bit but the Orion has an input range of either 8-17V for the 18A or 10-17V for the 30A, with an input cut off of 7V.

Depending on how you configure the start up and shut down voltages, what will likely happen when you plug in to shore power is that the Orion will put it's full output into the house battery, taking the full 20A from the mains charger plus any extra it needs out of the start battery. When the start battery drops below the configured cut off voltage, the Orion will switch off and wait for the start battery to come back up above the cut in voltage again. The result would be the average power delivered by the Orion to the house battery will match that supplied by mains charger (minus efficiency loss).

It depends on what your usage is like as to which one to choose. If you are mainly doing day sails or going between marinas with shore power and you aren't bothered about rapid charging, then the 18A one is likely sufficient and you can save a bit of cash. If you spend more time at anchor or on longer passages, the faster charging under engine might be useful. I'd be tempted to go for the larger one, because it will probably put back a significant chunk of what you use during a day just in the time you spend motoring back into port.

 

[slug zitski]

HI Caius. I am looking at replacing my House PbA with LiFePo4 and using the Orion DC/DC charger to keep the necessary changes to a minimum. My question is about charger location. The manual says to keep the charger as close as possible to the batteries, but other requirements makes the engine bay unsuitable i.e. don't place the charger over the batteries, keep good ventilation, etc. I do not want to put the charger in the quarter berths, which pretty much forces a Nav-Station location. This would require up to 10 foot wiring runs between the batteries and the charger...does this sound appropriate to you? Where did you put yours?

Chargers generate heat …mount them stand off, air space behind, air flow , and make sure that the location has plenty of ventilation

I don’t know your model charger or situation but I’ve used many victron , mastervolts units

when they overheat they go into failure mode, red light flashing and don’t output

installations benefit from additional forced air ventilation …a small dc computer type fan triggered by a thermo switch mounted on the charger with glue

the typical thermo switch triggers at 40c

 

[caius]

The Victron units actually give their rated output at 40°C, so if you can keep them cooler than that they perform better - at 25°C they can output 20-25% more than rated, so it's definitely worth making sure they have good ventilation.

 

[slug zitski]

The Victron units actually give their rated output at 40°C, so if you can keep them cooler than that they perform better - at 25°C they can output 20-25% more than rated, so it's definitely worth making sure they have good ventilation.

I don’t know

the victron technical guy recommended the 40c thermo switch that operates the forced vent fan

 

[caius]

It's on the spec sheet - they explicitly give performance at 40°C and at 25°C. This video is relevant. This chap tested the Orion 30 with forced ventilation in his van to good effect.

 

[Second Row]

Chargers generate heat …mount them stand off, air space behind, air flow , and make sure that the location has plenty of ventilation

I don’t know your model charger or situation but I’ve used many victron , mastervolts units

when they overheat they go into failure mode, red light flashing and don’t output

installations benefit from additional forced air ventilation …a small dc computer type fan triggered by a thermo switch mounted on the charger with glue

the typical thermo switch triggers at 40c

View attachment 548892

Hi Slug...my charger is a SM1220. I have asked Sentry support where I can get a manual for it but not luck so far. Looks like I will need to put some ventilation fans into the area where the current charger and the new DC-DC Charger will live (i.e. under starboard quarter berth)...one turning to pull cool air in and another to push hot air out.

 

[slug zitski]

Hi Slug...my charger is a SM1220. I have asked Sentry support where I can get a manual for it but not luck so far. Looks like I will need to put some ventilation fans into the area where the current charger and the new DC-DC Charger will live (i.e. under starboard quarter berth)...one turning to pull cool air in and another to push hot air out.

Sometimes if you google Sentry sm1220 with PDF following the query you can find the manuals …even for old stuff
as for ventilation each situation is different ..air in , air out is important

don’t know if this is your unit

http://www.sentrychargers.com/downloads/G_series_manual.pdf

 

[caius]

my charger is a SM1220. I have asked Sentry support where I can get a manual for it but not luck so far.

There's a reference to that model here.

 

[Second Row]

There's a reference to that model here.

That one had the proper manual. I will ask Sentry directly, but in your opinion, if the system has 2 charging outputs and is rated at 20amps and has a maximum charging voltage of 14.3V (i.e. ~286Watts) and is 75% efficient, that would require input power of 286W*2/.75 or 762Watts to power both outputs at maximum charge. Given that the 115V AC input is rated at 4Amps (460 Watts) and fused at 6Amps (690Watts), I can safely assume that the charger will not push both charging outputs at maximum rating.

 

[willsailforfood]

This might make sense on smaller systems, but not on bigger systems. My boat is 24V, and I have two 140A alternators. That's ~8kW at the top of the voltage range. It would not make sense to retain a PbA interface battery and use a DC-DC charger for me.

In fact I would argue that many people making the lithium upgrade are looking at also adding and/or powering by inverter high power consumers such that the DC-DC route doesn't make much sense - once you're over ~1kW loads it's impractical.

I'm just planning a lithium upgrade to start March 1. I'm going to buy a pair of Lithionics [email protected] batteries with their external BMS with the dual channel option. I like the dual channel because it manages the charge and discharge sides separately. A disconnect fault on the charge side (most likely problem) doesn't affect the load side so you don't have a dark ship. This device also has a field control circuit which shuts off the alternators and any other charge sources if there's a charge side disconnect - critical item. It also has a pre-charge circuit so you don't melt anything with inrush current when connecting my twin 5kW inverters. I'm also going to switch from Balmar to American Power System Wakespeed regulators for the two 140A alternators, much smarter and data-integrated with the BMS. Aside from that my Xantrex solar charge controllers can be set to the correct voltages, and my 400W wind turbine can also. My 2009 vintage Victron Skylla TG-100 Universal shorepower charger will have to be replaced with the new version as the old one can't be adjusted for the correct voltages.

It's going to be a pretty big project, but I'm looking forward to losing 200 lbs, and no longer being the bitch of my PbA batteries.....

This is very similar to what I'm planning this winter for our boat.

 

[Second Row]

Sometimes if you google Sentry sm1220 with PDF following the query you can find the manuals …even for old stuff
as for ventilation each situation is different ..air in , air out is important

don’t know if this is your unit

http://www.sentrychargers.com/downloads/G_series_manual.pdf

That one is not but Caius found me one...thanks for your help!

 

[caius]

That one had the proper manual. I will ask Sentry directly, but in your opinion, if the system has 2 charging outputs and is rated at 20amps and has a maximum charging voltage of 14.3V (i.e. ~286Watts) and is 75% efficient, that would require input power of 286W*2/.75 or 762Watts to power both outputs at maximum charge. Given that the 115V AC input is rated at 4Amps (460 Watts) and fused at 6Amps (690Watts), I can safely assume that the charger will not push both charging outputs at maximum rating.

Yes that's correct. It won't supply 20A to both battery outputs simultaneously. It will be able to supply 20A in total, split between both terminals. How much current goes to each one would depend on the state of charge of each battery. If you only have one connected, that will get the full 20A.

 

[Second Row]

When putting together the connections, would you suggest tinned-copper or just copper? I have read that the conductivity
of tinned-copper wire is the came as just copper wire (which I find illogical as tin has 15% of the conductivity of copper, but maybe they only count the cross section of the copper when specifying the wire gauge), but the tin protects the
copper from oxidation (but wouldn't an intact silicon cover and shrink wrapped ends do the same?). Anyway, crimped ends are meant to cold weld the copper to the rings, does sheathing the copper in tin impact the effectiveness of the cold-weld process?

 

[slug zitski]

When putting together the connections, would you suggest tinned-copper or just copper? I have read that the conductivity
of tinned-copper wire is the came as just copper wire (which I find illogical as tin has 15% of the conductivity of copper, but maybe they only count the cross section of the copper when specifying the wire gauge), but the tin protects the
copper from oxidation (but wouldn't an intact silicon cover and shrink wrapped ends do the same?). Anyway, crimped ends are meant to cold weld the copper to the rings, does sheathing the copper in tin impact the effectiveness of the cold-weld process?

tinned copper is superior for marine use….it’s also expensive and hard to find

in general you use tinned wire for high endurance applications…wire that may get wet…. and normal copper wire for the rest